THE UNIVERSITY
OF ILLINOIS
LIBRARY
5-04-
OAK ST. HDSF
FOUNDED MDCCCXCVIII
DISTRICT OF COLUMBIA
Class Q i:iB.ti u , 1
BookT>44-^^^^^^^^'^ Vol
GIVEN BY
PtSTERSOIir s
FAMILIAR SCIENCE;
OR THE
SCIENTIFIC EXPLANATIOU
OB
COMMON THINGS.
E»ITED BY
R; Peterson,
HIMBKB OF THS ACADEMY OF NATUEAL SCIENCES, PHIL ASZLPHIA.
L'homnie, sur un monde de poussiere qui tourn6 ct Pemporte avee
rapidite, a mesure I'immensite des cieux. II vous dira la grandeur det
antres, leur vitesse et leur distance; interrogez-le sar I'atume qui eat
(lepras de lui, il gardera le silence.
X. Aim'c Martin.
ONE and tenth thousand.
J^HILABELPHM :
J. B. LIPPING OTT & GO,
\
Office of tiik Cor^TROLLEEs of Pi3 blic Schools, j
First School District of Pennsylvania,. \
Philad'a., Sept. 11, 1S51.
At a Meeting of the Controllers of Public Schools, First D.'stricl
af Pennsylvania, held at the Controllers' Oltice, Tuesday, Sept 9»
ISfjl, HiC loilowing resolution was adopied.
Resolved, Tbat the work entitled Familiar Science," be intro-
duced into the Grammar Schools of this Di>lrict.
Ho BERT J Hemphill, Sec'ry.
At a Tneetin«: of the Board of Education of the Brooklyn Public Schools
held Dec. 2, 1851, the following resolution was adopted ;
Hesolvedy Thai " Peterson's Familiar Science," be adopted as a text
Dook for use in the rublic Schools,
W. S. DILLINGHAlVf,
Chairman of Com. on School Booki
Ittest, 8. L. HoLMM, Sec'y.
Elntered according to the Act of Congress, in the year 185L by
ROBERT E. PETERSON,
In tlie Clork'fl OHice of the District Court of the Eastern DidtriCI
of PtJiLcsyi vania.
0
' - ' ' • ^ ' jr^, -?* V r"«
A part of ijie followml^ woflr' i^'"from the pen 0/ the Rev.
i)r. Brewer, of 'I'wjaityjiall, lilso, TIe&d Musi en
of King's Colleg6^^iSuihMri|fti^WQh-^^ liiiioii with iying's
College, London. It ■ oonfem airTmiciT-Tiscfulv as well as prac
ti( al scieuuiic knowledge, in a very popular and entcrtainiiig
ferm ,
The work, however, as it emanated from the English press,
was not only in many points unsuited to the American pupil,
but was OAcreniely deficient in its arrangement. The Editor
has endeavored to remedy these defects, by making many
additions, as well as by altering those parts which were
purely applicable to Great Britain, and adapting the whole
to our own countiy. As to the arrangemcnl, he feels con-
fident it will be the means of facilitating the acquirement of
the great amount of useful information embodied in the work,
and also of classifying in the mind of the pupil the different
branches of which it treats.
" No science is more generally interesting than that which
3xplains the common phenon^ena of life. - We see that salt
And snow are both wliite, a rose red, leaves green, and the
nolet a deep purple ; bul how few persons ever ask the rea-
son why ! We know that a flute produces a musical sound,
and a cracked bell a discordant one — that tire is hot, ice cold,
and a candle luminous — that water boils when subjected to
heat, and freezes from cold ; but when a child looks up into
our face and ask us 'why' — how many times is it silenced
with a frown, or 'called very foolish for asking such silly
questions !'
This book, intended for the use of families and school's,
explains about two thousand of these questions, and is writ-
ten in language so plain as to be understood by all. Care
has been taken, however, in the endeavor, to render it intelli-
gible to the young, to avoid that childish simplicity which
might he unacceptable to those of riper years.
A very full Index is appended to the work, to facilitate tha
pupil's researches.
f Dr Srewer'fl Frefacct
iii
1^627
PREFACE.
In the Preface, to the English edition, already mentioned,
there is an aneodote related, which is so appropriate, that it
IS here given in full.
remarkable instance came before the author a few
months since, of the statement made in the earl} part of this
Profacc. The conversation was about smoke — why it waa
black, and not white like the fine dust of lime. A Httle child
who was present, asked, * Why is the kettle so black with
smoke?' Her papa answered, * Because it has been on the
fire.' * But,' (urged the child) ' what is the good of its being
black V The gentleman replied, ' Silly child— you ask very
foolish questions — sit down and hold your tongue.' "
Information of that description is just what children love
to gain, and what many older persons, who are even tolera-
bly well informed, are not competent to give.
The Editor trusts his book may prove an interesting and
useful companion to both old and young, either in the family
circle, or in the school-room. /
Twenty-five thousand copies of the English edition of the
above work were sold in London in less than two years.
Philadelphia, Apkil, 1851.
The following is extracted from a letter received by th«
Editor, from the Hev. Dr. Brewer :
Robert E. Peterson, Esq.
Dear Sir — I have received the American edition of my
Guide to Familiar Science, and thinlr it very handsomely
printed and skilfully rearranged. I shall esteem it an honor
to>*give my full consent to your expressing my approbation
of your edition of my Familiar Science, and I thank you foi
fche k^idness in having sent me a copy.
Dear Sir,
Yours truly,
E. 0. BREWER.
St Helen, Isle op Jersey,
3d Dec. 1851.
CONTENTS.
PART I.— HEAT.
UIB.
CiiAP I -TheSttn. 7
Sec. 1. The sun the primary source of heat. , - 7
2. Caloric. . . . , ■ 8
II. — Electricity. .... - 9
Sec. 1. Electricity produced by friction. . . 9
2. Lighlmiii!:. . . - * c 13
§ 1. Dano-er from licfhTning. , , 19
2. Lij^tiMiinsx conductors. • . 28
3. Ettecis of lightning. ... 33
3. Thund-r. ...... 33
<^ III.— -Chemical Action. . • • . c 43
Sec. 1 Expansion. . . . » , 43
§ 1. Exjiansinn of liquids and gases. , . 43
2. l']yMa[ifiir)n of metals. • . . 54
3. Venrilanon. . , . , , 60
2. Cotidiu'iion oi heat. .... 79
^ 1. Conductors of heat. • . 79
2. Convection. . • • • . 99
3. Change of state. . . . • . 107
§ 1. Latent heat. • • • , 110
2. Ehullition. . , , , 113
3. Evaporation. • . , , 121
4. Vaporization. • « • , 131
5. Liquefaction. • • • • 1.35
4. RndialKMi. 137
5. Reflection. . • • • . 144
6. Absorption. • • . • • 149
IV. — ^Mechanical Action. • • • , ,101
Sec. 1. Percussion. . . • • , 181
2. Friction. ...... 1G5
3 Condensation or compreision. • . , 188
PART II.— NON-METALLIC ELEMENTS.
HHAP I.— Oxygen and Oxides. . . . • , 17«
Sec. 1. Oxvjjen. ...... 170
2. Oxides 175
** II. — Hydrogen and Wateb. • « > • 184
Sec. 1. Hydrogen. . • • * 184
2. Writer 187
" III. — Nitrogen and Air. . • • • • 192
Sec. I. Nitrogen. . , • • • ,192
2. Air. 193
« rV.— Carbon. 195
5ec. 1. Carbonic acid. . . . , .200
§. Effervescence. • • • t 216
2- Carburetted Hydrogen, . • . .229
VI
coNTEii rs.
CRAP. V -PHospnorviJs and Phosphueettei» Htdrogen. 223
Sec. 1. Phosphorus. ..... 223
2. Phosphurctted hydrogen. . , , 22(5
VI.— Combustion. ...... 2*^
Bee. 1. Sponlaneous combustion. . . « 249
2. Flame. . . > o . . 250
PART III.— METALS.
CHAP. J —Metals and Allots. ..... 269
Sec. 1. Metuls 239
2. AUf^ys. . . • . . 264
'•* 11. — Glass, Pokcelain, and Earthenware. . , 266
PART IV.— ORGANIC CHEMISTRY
CHAP. T.— Sugar .274
" II , — Fekmentation and Put refaction. . . 275
Sec. 1. Fermentation. ..... 275
2. Puliefaclion. ..... 2S6
" III.— Components of tee Ahimal Bodt. . . . 292
« IV.— Animal Heat 297
Sec. 1. Food. .... I . 306
2. Hunger. .... 311
« v.— Sleep. ....... 315
« VI.— Acids 317
VII.— Oils 320
" VIII.— Antidotes for Poisons. . . . .324
part v.— meteorology.
CHAP. I.— Atmosphere. ...... 327
" II.— Winds 336
Sec. 1. Trnde winds. ..... 342
2. Monsoons ..... 346
« III.— Clouds. . . , . . , . a56
Sec. 1. Modification of clouds 269
2. Dew. 374
3. Rain, Snow, Hail. .... 388
4. Mist, Fog, Frost. . . . ' . 399
« IV,— Ice 413
PART VI.— OPTICS.
eilAP. I —Light .427
Sec. 1. The eye the seat of vision. • . , 452
2. Deceptions of vision. .... 458
« II.— Refk action. ...... tei
" III.— REFLECTIOJSf. ...... 473
« IV.— Color 477
PART VIL— SOUND.
CHAP. I —Transmission op sound. . . • t 485
jb'ec. 1. Musical sounds. . . • • « 496
2. Echo * ,499
MISCELLANEOUS. . . . . * . flW
PART I.-HEAT,
CHAP. L— THE SUN.
BS«riONI. THE SUN THE PRIMARY SOURCE OF HBAT
1.
Q. What is heati
A. The sensation of warmth.
2.
Q, What is the principal source of heat ?
A. The Sun is an inexhaustible source of
heat.
3.
Q. Does the heat of the Sun possess any
different properties from artificial heat ?
A. The heat of the Sun passes readily
through glass, whereas this property is pos-
sessed by artificial heat in a vei^y small de* -
^ree.
4.
Q. Is sun-shine detrimental to combus-
tion?
A. It is; the reason is not cerfaiinly
7
8
THE SUN.
kn. i^vri , but fires are never so bright when
ti;--: . 'm shines on tliem. It is generally
- ^ posed some chemical effect is proclucfMi
vi[>un the Mr in contact with the fire which
>Mj>Hdes tlio progress of combustion.
SECTior; II. CALORIC.
5.
Q. How is the sensation of heat produced ?
A. When Ave touch a substance hotter
than ourselves, a subtle invisible stream flows
from the hotter substance^ and produces on
our nerves the sensation of warmth.
6.
Q. What is that ''subtle invisible stream^^
called, which flows from the hotter sub-
stance ?
A. Caloric. Caloric, j:herefore is the
agent, which produces the sensation of
warmth ; but heat is the sensation itself.
7.
Q. Is caloric equally distributed over thf!
globe ?
A No ; at the equator the average tempe-
CALORIC.
9
^ature h 82i% while at the pole» it is be-
haved to be about IS"" below Zero.
Average Temperature,^'' that is, the mean. or medium tempenttiirg'.
Zero," the point I'tora which a thermometer is graduated— St i32*
ow freezing.
CHAP. II.— ELECTRICITY, THE SECOND
SOUECE OF HEAT.
SECTION 1. ELECTRICITY PRODUCED BY FRICTIOfiT.
0.
Q. Was electricity known to the ancients?
A. Yes ; they knew that when amber (the
Greek word of which is ?7^£xr(po^'— electron,)
is ruhhedy it acquires the property of attract-
ing other bodies.
9.
Q. Why is electricity excited by fncticn ?
A. Electricity, like heat, exists in all
matter; but it is often in a latent state ;
friction disturbs if, and brings it into active
peration.
^Latenij^^ — that is hiiiden, concealed.
10.
Q. When you rub a piece of paper with
Indian rubber, why does it adhere to the ta-
ble?
10
ELECTRICITY.
A. Because the friction of the Indiari
cnMj'jr against the surface of the paper de-
ve.l6|j^s electricity, to which this adhesive-
noiss is mainly to be attributed.
11.
Q. If you dry a piece of common hrown
foper by the fire, and draw it once or twice
between your knees, why will it stick fast
to the wall ?
A. Because the friction developes electri-
city on the paper, which manifests itself by
this proj)erty of adhesion.
12.
Q. When a glazier is mending a window
and cleans the pane with his brush, why
do the loose pieces of putty (on the opposite
side of the window pane,) dance up and
down ?
A. "\^T[ien glass is rubbed, electricity is
excited in the parts submitted to the fric*
Hon, and on the part opposite also; electricity
attracts light substances such, as loose frag-
ments of putty; as soon as these fragments
have touched the excited part of the glas^
they become charged, and fall back agairlj
the ledge on which they fall deprives them
of their burden, and they then fly up again
to receive a fresh charge; this proceSjS being
PRODUCED BY FRICTION. 11
1^3 pea ted often, makes the commotion in tlie
loose fragments of putty, referred to in the
question.
13.
Q. Why does hrusJung the hair for a long
ime, frequently make the head itch.
A. 1st. — ^Because the friction of the hair
brush excites electricity in the hair, Avhich
thus becomes overcharged and irritates the
skin; and
2nd. — The hair brush excites increased
action in the vessels and nerves of the scalp,
producing a slight degree of inflammation,
which is indicated b ^ a sensation of itchin jjreiit dansrcr need really to he appn^h^nded from 'iffbtnin?, if yon
avoid lakiiig your posinou near tall trees, siurea, or other elevated otjeeta
28
ELECTRICITY.
77.
Q. Is it better to be wet or dry during a
thunder storm?
A. To be wet ; if a person be in tlie open
tield, the best thing he can do, is to stand
about twenty feet from some tree, and get
completely drenched to the skin.
IB.
Q. Why is it better to be wet than dry?
A. Because wet clothes form a letter con-
ductor than the fluids of our body ; and there-
fore, lightning would pass down our wet
clothes, without touching our body at all.
§ n. — Lightning Conductor.
79.
Q. WTiat is a lightning conductor?
A. A metal rod fixed in the earth, run-
ring up the whole height of a building, and
rising in a point above it.
80.
Q. Wh^i metal is best for this purpose?
A. Copper makes the best conductor.
81.
Q. Why is copper better than iron?
A. 1st. — Because copper is a better con-
ductor than iron ;
^ LIGHTNING CONDUCTORS. 29
2n(|^— It is not so easily fused or melted ;
and
3rd. — It is not so readily injured by
weather.
82.
(Jl What is the use of a lightning con-
ductor?
A. As metal is a most excellent con-
ductor, lightning (which makes choice of
the best condudGrs) will run down a metal
rod, rather than the walls of the building.
S3.
Q. Why should liglitnmg-conductors be
pointed ^
A. Because points conduct electricity
away silently and imperreptUdy ; but Ivuobs
produce an explosion which w^ould endanger
the building.
P.)infs empty the p'onds of electricity, actinsrat n innch ^renter distanoia
Ihriii k jolx ; f liu*. a lievll^'Jl jnr «»f consiHerahle fsize mny l)e sMfVly and
c-ilH.nIv tli<<-harirefl, by holdiiii^ the point of a ii-^rdie an inch or iwo o:T.
Mbnlcj; of L'r i^/i(i by heat ; and
a bar of iron when hot will measure more
than when it was cold.
184.
Q. Will the iron contract in size on cool-
ing, after it has been heated?
A. Yes ; it will return to its former
dimensions on getting cold again.
185.
Q. Why do most persons dip their razoi
in hot loater before shaving with it?
A. Because the heat of the water ex-
pands the edge ; by that means rendering
it more fine and sharp. ,
186.
Q. Why does a cooper heat his hoops red
Lot when he puts them on a tub?
A 1st. — As iron expands hy heat, the
hoops will be larger when they are red hot ;
EXPANSION OF METALS.
57
ill consequence of which, they will fit on
the tub more easily ; and
2nd. — As iron contracts by cold, the hoops
will shrink as they cool down, and girt the
tub with a tighter grasp.
187.
Q. Why does a wheelwright make the tire
red hot which he fixes on a wheel?
A. 1st. — That it may fit on more easily ;
and
2nd. — That it may girt the wheel more
tightly. I-
188.
Q. Why will the wheelwright's tire fit the
wheel more easily, for being made red hot?
A. Because it will be expanded by the
heat ; and (being larger) will go on the
wheel more easily.
189.
Q. Why will the tire which has been
piit on hot, girt the wheel more firmly?
A. Because it will shinnk when it cools
down ; and, therefore, girt the wheel with a
tighter grasp.
190.
Q. Why does a stove make a crackling
noise when a fire is very hot ?
58
CHEMICAL ACTION
A. Because it expands from the heat ; and
liie parts of the stove rubbing against each
other, or driving against the bricks, prod uco
a crackling noise.
191.
Q Why does a stove make a similar crack'^
hug noise when a large fire is put out ?
A. Because it contracts again, when the
fire is removed ; in consequence of which,
the parts rub against each other again, and
the bricks are again disturbed.
192.
Q. Why does the plaster roui^d a stove
crack and fall away?
A. Because (when the fire is lighted) the
iron -work expands more than the brick- work
and plaster, and pushes them away ; but
(when the fire is put out) the metal shrinks
again, and leaves the "setting'' behind.
The ''setting" is a technical word for the plaster, etc., in immediate
ccntnct with ihe stove.
The.=e questions apply more particularly to what is called a * Franklil
Stove " — they may be Seen in many of our farm houses.
193.
Q. Wliy does the plaster fall away ?
A. As a chink is left (between the "set*
ting'' and the stove,) the plaster will fre-
quentl}' fall away from its own weight.
EXPANSION OF METAI^.
59
194.
Q. Wliat other cause contributes to hnng
the plaster down?
A. As the heat of the fire varies, the size
of the iron stove varies also ; and this swell-
ing and contracting keep up such a constant
disturbance about the plaster, that it cracks
and falls off, leaving the fire-place very un-
sightly.
195.
Q. If the boiler or kettle attached to a
kitchen range, be filled with cold water
sometime after the fire has been lighted, it
will be very likely to crack or burst. Why
is this ?
A. Because the heat of the fire has caused
the metal of which the boiler is composed
to expand; but the cold water very suddenly
contracts again those parts with which it
comes in contact ; and as one part is larger
than the other, the boiler cracks or bursts.
IDS.
Q. When the stopper of -decanter ot
smelling-bottle sticks, why will a cloth
wrung out of hot water, and wrapped around
the neck of the bottle, loosen the stopper ?
A. Because the hot cloth heats the neck
60
CHEMICAL ACTION.
of the bottle, causing it to expand^ and con-
sequently loosens the stopper.
197.
Q. Why does the stopper of a decanter
stick fast if it be put in damp ?
A. If the stopper be damj), it fits the
decanter air-tight ; and if the decanter was
last used in a heated room, as soon as the
hot air enclosed in the inside has been con-
densed by the cold, the weight of the ex-
ternal air will be sufficient to press the
stopper down, and make it stick fast.
198.
Q. Why does the stopper of a smelling-
bottle very often stick fast ?
A. Because the contents of a smelling-
bottle are very volatile, and leave the neck
of the bottle, and the stopper, damp.
If the !*melling-bottle was last used in a hot room, as soon as the hot air
and volatile essence, inside the bottle, have been condensed by the cold,
the weight of the external air will be sufficient to press the stopper dcw«
and make it stick.
§ III. — Ventilation,
199. ^
Q. What is ventilation ?
A. The renewal of fresh air — a continual
ehange of air.
VENTILATION.
61
200.
Q. Is the air in a room in perpetual ino*
tion as the air abroad is ?
A. Yes; there are always .urrents of
air in the room we occupy; one of hot air
(lowing out of the room, and another of cold
air flowing into the room.
201.
Q. How do you know that there are these
two currents of air in every occupied room ?
A. If I hold a lighted candle near the
crevice at the top of the door, the flame will
be blown outward (towards the hall ;) but if
I hold the candle at the bottom of the door,
the flame will be blown inwards (into the
rooin.)
N B. This is not the case if a fire Jje in the room. When a fire i3
lighted, an inward current is drawn through all the crevices.
202.
Q. Why would the flame be blown out-
wards (towards the hall,) if a candle be held
at the top of the door ?
A. Because the air of the room being
heated, and consequently rarified, ascends ^
and (floating about the upper part of the
room) some of it escapes through the crevice
at the top of the door, producing a current
of air outioards (into the halL)
6
62
CHEMICAL ACPiON.
203.
Q, Why would the flame be blown in*
wards (into the room,) if the candle be held
at the bottom of the door ?
A. Because a partial vacuum is made at
the bottom of the room, as soon as the warm
air of the room has ascended to the ceihng,
or made its escape from the room ; and cold
air from the hall rushes under the door, to
supply the void.
204.
Q. What is meant by a "partial vacuum
being made at the bottom of the room V
A. A vacuum means a place from which
the air has been taken; and a ''partial va-
cuum^' means a place from which a part of
the air has been taken away. Thus, when
the air near the floor ascends to the ceiling,
a partial vacuum is made near the floor.
205.
Q. And how is the vacuum filled up again ?
A. It is filled up by colder air, which
rushes (under the door, and through the
'joindow crevices) into the room.
206.
Q , Give me an illustration ?
A, If I dip a pail into a pond and fill it
with water, a hole (or vacuum) is inade in
VENTILAIION.
33
tlie pond as big as the pail ; but the monieut
I draw the pail out, the hole is filled up by
the water around.
207.
Q. Show how this illustration applies ?
A. The heated air, which ascends from
the bottom of a room, is as much taken
away as the water in the pail ; and (as the
void was instantly supplied by other water
in the pond) so the void of air is supplied by
the air around.
208.
Q. Why is a room (even without a fire)
generally warmer than the open air ?
A. Because the air in a room is not sub-
ject to much change, and soon becomes of the
same temperature as our sldn, when it no
longer feels cold.
209.
Q. Why do we generally feel colder out-
of-doors than in-doors?
A. Because the air (which surrounds ub)
is always changing ; and as fast as one por-
tion of air has become warmer by contact
with our body, another colder portion sur-
rounds us, to absorb more heat.
210.
Q. Why is there a strong draught through
the keyhole of a door ?
04
CRj^MICAL ACTION.
A. Because the air in the room we occupy
is warmer than the air in the hall ; there-
fore, the air from the hall rushes through the
keyhole into the room, and causes a draught.
211.
Q. Why is there a strong draught under
the (/oor, and through the crevice on each
side ?
A. Because cold air rushes from the hall,
to supply the void in the room, caused by
the escape of warm air up the chimney, etc.
212.
Q. "Why is there always a draught through
the window crevices ?
A. Because the external air (being colder
than the air of the room we occupy) rushes
through the window crevices to supply the
deficiency, caused by the escape of warm air
up the chimney, etc.
213.
Q. If you open the lower sash of a win-
dow, there is more draught than if you open
the upper sash. Explain the reason of this?
A. If the lower sash be open, cold external
air will rush freely into the room and cause
a great draught inwards ; but if the upper
Rash be open, the heated air of the room wDl
VENTILATION.
65
msli out, and (of course) there will be less
draught inwards.
214.
Q. By which means is a room better veti"
tilahd—By opening the upper or the lower
sasli ?
A. A room is better ventilated by opening
(he upper sash ; because the hot vitiated air
(which always ascends toward the ceiling)
can escape more easily.
215.
Q. l)y which means is a hot room more
quickl}' cooled — By opening the upper or
the lower sash ?
A. A hot room is cooled more quickly by
opening the lower sash ; because the cold air
can enter more freely at the lower part of
the room, than at the upper,
216.
Q. Which is the hottest place in a church,
chapel, or theatre ?
A. The gallery.
217.
Q. Why is the gallery of all public places
hotter than the lower parts of the building ?
A. Because the heated air of the build-
ing ascends ; and all the cold air (which can
enter through the doors and windows) keeps
to the floor, till it has become heated
6*
66
CHEMICAL ACTION.
218.
Q. Why is the gallenj of a church or the-
atre hotter than the aisle or pit ?
A. Because the hot air ascends from the
bottom to the top of the building ; while cold
air flows to the bottom from the doors and
windows.
219.
Q. How are mines ventilated ?
A. The mine is furnished with two shafts
or flues. These flues are so arranged, that
air forced down one, shall traverse the whole
extent of the mine before it escapes by the
other. By keeping up a fire in one of these
shafts, the air is rarified or expanded within,
causing an ascending current, carrying with
it all the noxious gases, and rendering the
air pure.
220.
Q. What effect is produced upon air by
rarif action ?
A. It is made lighter and ascends through
colder strata ; as a cork (put at the bottom
of a basin of water) rises to the surface.
221.
Q. Prove that rarified air ascends 1
A. When a boy sets fire to the cotton or
gponge of his balloon, the flame heats th4
VENTILATION.
67
air ; which becomes so light, that i{ ascends,
and carries the balloon with it.
222.
Wliy should stoves be fixed as neaj
the floor of a room as possible ?
A. In order that the air in the lower part
of the room may be heated by the fire.
223.
Q. Would not the air in the lower part
of a room be heated equally well if the
stoves w^ere more elevated ?
A. No ; the heat of a fire has very little
effect upon the air below the level of the grate ;
and therefore, every grate should be as near
the floor as possible.
224.
Q. Our feet are very frequently cold when
we sit close by a good fire; Explain the
reason of this ?
A. As the fire consumes the air which
passes over it, cold air rushes through the
crevices of the doors and windows, along the
floor of the room-, to supply the deficiency ;
and these currents of cold air, rushing con-
stantly over our feet^ deprive thera of theii
warmth.
225
Q. What is smoke ?
68
CHEMICAL ACT! CIS.
A. Small particles of carbon, separated
by combustion from the fuel, but not con-
sumed.
226.
Q. Why does smoke ascend the chimney j
A. Because the air of the room (when it
passes over the fire) becomes lighter for he-
ing heated; (being thus made lighter) ascends
the chimney, carrying the smoke with it.
227.
Q. "Why do smoke and steam curl as they
ascend ?
A. Because they are forced round and
round by the ascending and descending cur-
rents of air.
228.
Q. Why do some chimneys smoke ?
A. Because fresh air is not admitted into
a room as fast as it is consumed by the fire ;
in consequence of which a current of air
rushes down the chimney to supply the defir
ciency, driving the smoke along wdth it.
229.
Q. AVliy cannot air be supplied as fast as
it is consumed by the fire ?
A. Curtains round the windows, sand
bags at the threshold of the doors, and all
such contrivances keep out the draught.
VENTILATIOxN.
G9
230.
Q, Why will the air come down the
tkimmy ?
A. Because it can get into the room in
no other way, if the doors and windows are
all made air-tight.
231.
Q. What is the best remedy in such a
case ?
A. The speediest remedy is to open the
door or window ; but by far the best re-
medy, is to carry a small tube from the
hearth into the external air.
232.
Q. Why is that the best remedy?
A. Because the fire will be plentifully
supplied with air by the tube ; the doors
and windows may all remain air-tight ; and
we may enjoy a warm fire-side, without the
inconvenience of draughts of air and cold
feet.
233.
Q. Why is a chimney raised so high above
the roof?
A. That it may not smoke; as all funnels
do which are too short
234.
Q. What is meant by the /?m7ir/ or flu.
of a chimney ?
70
CHEMICAL ACTION.
A. That part of a chimney through which
the smoke passes.
235.
Q. Why does a chimney smoke if fun-
nel be very short ?
A. Because the draught of a short flue is
too slack to carry the smoke up the chimneyo
236.
Q. Why is the draught of a short flue
more slack than that of a long one ?
A. 1st. — Because the fire is always dull
and sluggish if the chimney be too short :
2nd. — Because the smoke rolls out of the
chimney before it has acquired its full ve-
locity ; and,
3d. — ^Because the wind, rain, and air,
have more influence over a short funnel
than over a long one.
237.
Q. Why is the fire alw^ays dull and slug-^
gish, if the chimney flue be very short ?
A. Because the draught is bad ; and, aa
the rarified air passes very tardily up the
chimney — fresh air flows as tardily toward
the fire ^ to supply it with oxygen.
238.
Q. Why does not smoke acquire its full
velocity in a short funnel ?
VENTILATION.
71
A. Because the higher smoke ascends,
(pro voided, the fire be clear and hot and the
flue be unobstructed) the faster it goes ; if,
therefore, a funnel he very short, the smoke
never acquires its full velocity.
239.
Q. Does the draught of a chimney de-
pend on the speed of the smoke through the
flue?
A. Yes. The more quickly hot air flies
up the chimney, the more quickly cold air
will rush toward the fire to supply the place;
and therefore, the longer the flue, the greater
the draught.
240.
Q. Why are the chimneys of manufacto-
ries made so very long ?
A. To increase the intensity of the fire.
241.
Q. Why is the intensity of a fire increased
by lengthening the flue ?
A. Because the draught being greater,
more fuel is consumed in the same time ;
and, of course, the intensity of the heat isf
proportionally greater.
242.
Q, If a short chimney cannot be length
72
CHEMICAL ACTION.
ened, what is the best remedy to prevent
smoking ?
A. To contract the opening of the chimney
contiguous to the stove.
243.
Q. Why will a smaller opening in that
part of the chimney near the ^re prevent
smoJdng ?
A. Because the air will be compelled to
pass nearer the fire ; and (being more heated)
will rise through the chimney more rajDidly ;
this increase of heat will, therefore, compen-
sate for the shortness of the flue.
244.
Q. Why will a room be full of smoke if
there be two fires in it ?
A. Because the fiercer fire will exhaust
the most air ; and draw from the smaller
one, to supply its demand.
245.
Q. Why will a chimney smoke if there be
a fire in two rooms communicating with each
other ?
A. Because (whenever the door between
the two rooms is opened) air will rush from
the chimney of the inferior fire to supply
the other ; and both rooms will be filled with
«moke.
VENTILATION.
73
246.
Q. What is the best remedy in this case?
A. Let a tube be carried from the hearth
ctf each fire into the external air; and then
ea:h fire will be so well supplied, that
neither will need to borrow from the other.
247.
Q. Why do vestry chimneys so ofteu
smoke ?
A. Because the wind (striking against
the steeple) is reflected hack, and, rushing
down the vestry chimney, forces the smoke
tnto the room.
243.
Q. Why does a house in a valley very
often smoke ?
A. Because the wind (striking against
the surrounding hills) hounds hack again upon
the chimney, and destroys its draught.
249.
Q. What is the common remedy in this
case?
A. To fix a cowl on the chimney top to
turn like a weather-cock, and present its
back to the wind.
250.
Q. Why will not a cowl always prevent a
chimney smoking ?
7
74
CHEMICAL ACTION.
A. Because if the wind be strong, and
there should be a steeple or hill near the
chimney, it would keep the opening of the
coidI towards the steeple or hill; and then tlie
reflected wind would Uoiu into the coivl, and
down the chimney.
251.
Q: As a cowl is not a perfect remedy, can
any other be suggested ?
A. Yes. If the chimney-flue can be
carried higher than the steeple or hill, no
wind can enter the flue.
252.
Q. If a chimney flue be carried up higher
than the steeple or hill, why cannot the
wind enter it ?
A. Because the reflected wind would
strike against the sides of the chimney-
flue, and not pass over the opening at all.
253.
Q. In what other cases will a chimney
smoke ?
A. If the door and fire-place are both on
the same side of the room, the chimney will
very often smoke.
254.
Q. Why will a chimney smoke if the door
md fire-place are both on the same side ?
VENTILATION.
A. Because (whenever the door is open-
ed) a current of air will blow obliquely into
the chimneTj place, and drive the smoke into
the room.
255.
Q. What remedy can be applied to this
evil ?
A. The door must be set opposite to the
chimney-place, or nearly so ; and then the
draught from the door will blow the smoke up
the chimney, and not into the room.
256.
Q, Why will a chimney smoke if it needs
sweeping!,
A. Because loose soot obstructs the free
passage of the smoke, delays its current , and
prevents the draught.
257.
Q. Why will a chimney smoke if it be out
of repair?
A. 1st. — Because the loose mortar and
]>ricks obstruct the smoke; and
2nd. — 'Cold air (oozing through the
chinks) chills the air in the chimney, and pre-
vents its ascent.
258.
Q. Why does an old fashioned farm-hmise
rhimney often smoke ?
76
CHEMICAL ACTION.
A. Because the opening of the chimney-
place is so very large, that much of the aii
which goes up the chimney, has never
passed near enough to the fire to become heated;
and this cold air (mixing with the hot) so
reduces the temperature of the air in the
chimney, that it ascends very slowly and
the draught is destroyed.
259
Q. Why does a chimney smoke if the
draught be slack ?
A. Because the current of air up the
chimney is not powerful enough to huoy up
the smoke through the flue.
260.
Q. If the opening of a chimney be too
large what remedy can be applied ?
A. The chimney-place must be contracted.
261.
Q. Why w^ill contracting the chimney-
place prevent its smoking ?
A. Because the air will then pass nearer
the fire; and (being more heated) will fly
faster up the chimney.
262.
Q. Wliy do almost all chimneys smoke
in gusty weather ?
A. Because the column of smoke is sud-
VENTILATION.
77
denly chilled by the wind, and (being un-
able to ascend) rushes back into the room.
263
Q What is the use of a chimney -pot ?
A, It serves to increase the draught when
the opening of a chimney is too large.
264.
Q. How does a chimney-pot increase the
draught of a chimney ?
A. As the same quantity of hot air has to
escape through a smaller openings it must
pass through more quickly.
265.
Q. Why do blowers^ when placed before a
grate, tend to kindle the fire ?
A. Because the air (by passing through
the fire) is made. much hotter, and ascends
the chimney more rapidly.
266.
Q. Why is a fire better supplied with
oxygen while the blower is before it ?
A. Because the blower increases the
draught ; and the faster the hot air flies up'
the chimney, the faster will cold air rush
towards the fire, to supply it with oxygen
267.
Q. Why does a parlor often smell dis-
agreeably of soot in summer time ?
78
CHEMICAL ACTION.
A. Because the air in tlie chimney (being
colder than the air in the jxrrlor) descends
into the room, and leaves a .^eeable smell
of soot behind.
268.
Q. Why does a poker tail uc, oss a dull jin
evive it ?
A. For two reasons : 1 .d, — Because the
poker concentrates the heat, and therefore in-
creases it ; and
2nd. — Air is arrested in the narrow aper-
ture between the poker and the coals, and
a draught created.
269.
Q. Why are fires placed on the floor of a
room, and not tovv^ards the ceiling ?
A. Because heated air always ascends.
If, therefore, the fire were not near the floor,
the air of the lower part of the room would
never be heated by the fire at all.
270.
Q. If you take a poker out of the fire, and
hold the hot end downwards, why is the handle
intensely hot ?
A. Because the hot end of the poker heats
the air around it ; and this hot air (in its
ascent) scorches ih(i poker and the hand whi'^li
holds it.
CONDUCTION OF HEAT.
79
271.
Q. How should a red hot poker be carried,
R) as not to hum our fingers ?
A. With the hot end upwards ; for then
the air (heated by the poker) would not
paes over our hand and scorch it.
SECTION II. CONDUCTION OF HEAT.
272.
Q. What is meant by conduction of heat ?
A. Heat communicated from one body to
another by actucd contact.
§ I. — Conductors of Heat
273.
Q. Why do some things feel colder than
others ?
A. Principally because they are better c on-
ductors ; and draw off heat from our body
much faster.
274
Q. What are the best conductors of heat ?
A. Dense, solid bodies, such as metal and
Btone.
275.
Q. "Which metals are the most rapid con*
ductors of heat ?
80
CHEMICAL ACTION.
A. The best conductors of heat arf; 1
gold ; 2, silver ; 3, copper :
The next best are 4, platinum; 5, iron;
6, zinc; 7, tin. Lead is a very inferior con
ihicter to any of the preceding metals.
276.
Q. What are the worst conductors of heat?
A All light and porous bodies; such as
hair, fur, wool, charcoal, and so on.
Two of the worst conductors known are hare's fur and eider down ; — tha
two next worst are beaver's fur and raw siik ; — then wood and luinp-
blaok ; — then cotton and fine lint ; — then charcoal, wood ashes, &c.
277
Q. Why does a piece of wood (blazing at
one end) not feel hot at the other?
A. Because wood is so bad a conductor, that
heat does not traverse freely through it;
hence, though one end of a stick be blaz-
mi the other end may be quite cold.
273.
Q. Why does hot metal feel more intensely
xuarm than hot wool ?
A. Because metal gives out a much
greater quantity of heat in the same space of
time; and the influx of heat is, consequently,
more perceptible.
279.
Q. Why does money in our pocket fe^l
very hot when we stand before a fj'e?
CONDUCTORS OF HEAT.
81
A. Beca^ise metal is an excellent conduc-
tor, and becomes rapidly heated. For the
Bame reason, it becomes rapidly cold, when-
ever it comes in contact with a body coldc?
than itself,
280.
Q. Why does a poker (resting on a fea
der) feel colder than the hearth-rug, which is
further off the fire ?
A. Because the poker is an excellent con-
ductor, and draws heat from the hand much
more rapidly than the woolen hearth-rug^
which is a very bad conductor : though both,
therefore, are equally warniy the poker seems
to be the colder.
281,
Q. Why does an iron pump-handle feel in-
tensely cold in winter?
A. Because it is an excellent conductor,
and draws off the heat of our hand so ra-
pidly, that the sudden loss produces a sen-
sation of intense coldness.
232.
Q. Is the ivon handle of the pump really
tolder than the wooden j^mj? itself?
A. No ; every inanimate substance (ex
posed to the same temperature) possesses
in reality the same degree of heat.
82
CHEMICAL ACTION.
233.
Q. Why does the iron handle seem so
much colder than the wooden j)ump?
A. Merely because the iron is a better con-
ductor; and, therefore, draws off the heat
from our hand more rapidly than wood
:loes.
284.
Q. Why does a stone or marble hearth feel
to the feet colder than a carpet or hearth-
rug ?
A. Because stone and marble are good con-
ductors ; but woolen carpets and hearth -rugs
are very bad conductors.
285.
Q. How does the stone hearth make our
feet cold ?
A. As soon as the hearth-stone has ab-
sorbed a portion of heat from our foot, it
instantly disposes of it, and calls for a fies'h
supply; till the hearth-stone has become of
the sa?ne temperature as the foot placed upon ii
286.
Q. Do not also the woolen carpet and
hearth-rug conduct heat from the human
body?
A. Yes ; but being very bad conductors,
thej^ convey the heat away so slowly^ that
tlie loss is scarcely perceptible.
CONDUCTORS OF HEAT.
83
287.
Q. Is the cold hearth-stone in reality of
the same temperature as the warm carpet ?
A. Yes; every thing in the room is
really of one temperature; but some things
feel colder than others, because they are
better conductors.
288.
Q. How long will the hearth-stone feel
cold to the feet resting on it ?
A. Till the feet and the hearth-stone are
both of the same temperature ; and then the
sensation of cold in the hearth-stone will
go off.
289.
Q. Why would not the hearth-stone feel
cold, when it is of the same temperature as
our feet?
A. Because the heat would no longer
rush out of our feet into the hearth-stone, in
s^rder to produce equilibrium.
290.
Q Why does the hearth-stone (when the
jfiie is lighted) feel hotter than the hearth-
rug ?
A. Because the hearth-stone is an excel-
lent conductor, and parts with its heat very
readily; but the woollen hearth-rug (beiDi^
84
CHEMICAL ACTION.
a had conductor) parts with its heat very
reluctantly.
291.
Q. Why does parting with heat rapidly
inake the hearth-stone feel warm ?
A . Because the rapid influx of heat raises
the temperature of our body so suddenly^
that we cannot help perceiving the increase.
292.
Q. Why does the non-conducting power
of the hearth-rug prevent its feeling so hot
as it really is ?
A. Because it parts with its heat so slowly
and gradually, that we scarcely perceive its
transmission into our feet.
293.
Q. Why are cooking vessels often furnished
with wooden handles ?
A. Because wood is not a good conductor,
like metal ; and, therefore, wooden handles
prevent the heat of the vessel from rushing
into our hands, to burn them.
294.
Q. Why is the handle of a metal tea-pot
made of wood ?
A. Because ivood is a had conductor; there-
fore, the heat of the boiling water is not so
CONDUCTORS OF HEAT.
85
quickly conveyed to our hand by a wooden
handle, as by one made of metal.
295.
Q. Why would a metal handle hum the
hand of the tea-maker ?
A. Because metal is an excellent conduc-^
tor; therefore, the heat of boiling water
would rush so quickly into the metal handle,
that it would burn our hand.
296.
Q Prove that a metal handle would be
hotter than a loooden one.
A. If w^e touch that portion of the metal,
into which the wooden handle is fixed, we
shall find that the wooden handle feels cold,
but the metal intensely hot.
297.
Q. When we plunge our hands into a
basin of water, why does it produce a sensa-
tion of cold ?
A. Because water is a better conductor than
air ; and, as it draws off the heat from oui:
hands more rapidly, it feels colder.
298.
Q. Why does the conducting power of
water make it feel colder than air ?
A. Because it abstracts heat from our hands
so rapidly, that we feel its loss ; but the air
8
86 CHEMICAL ACTION.
abstracts heat so very slowly, that its gradvd
loss is hardly perceptible.
299.
Q. Is water a good conductor of heat ?
A. No ; no liquid is a good conductor c f
heat; but yet water is a much better con
duct or than air.
300.
Q. Why is water a better conductor of heat
than air ?
A. Because it is less subtile ; and the con-
ducting power of any substance depends
upon its solidity, or the closeness of its par-
ticles.
301.
Q. How do you know that water is not a
good conductor of heat ?
A. Because it may be made to boil at its
surface, without imparting sufficient heat to
mdt ice a quarter of an inch below the surface.
302.
Q. Why are not liquids good conductors of
heat?
A, Because the heat (which sliould be
transmitted) produces evaporation, and flies
off in the vapor.
303.
Q. Why are hot bricks (wrapped hi cloth)
CONDUCTORS OF HEAT.
87
employed in cold weather to keep tlie fett
jvarin ?
A Because bricks are had conductors of
heat, and cloth or ^dimi^X still worse ; m con-
sequence of which, a hot brick (wrapped in
flannel) will retain its heat a very long time.
304.
Q Is air a good conductor ?
A. No ; air is a very had conductor ; and
IS heated (like water) by convection,
305.
Q. How is a room warmed by a stove ?
A. The air nearest the fire is made hot
first and rises ; cold air then descends, is
heated, and ascends in like manner; and
this interchange goes on till all the air ol'
the room is warmed.
306.
Q. If air be a had conducto? of heat, whj/
should we not feel as warm witliout clothing,
as when we are wrapped in wool and fur 1
A. Because the air (which is cooler than
our body) is never at rest ; and every fresh
particle of air draws off a fresh portion of
heat.
307,
Q. ^Vhy are woolens and furs used for
dothing in cold weather ?
88
CHEMICAL ACTION.
A. Because they are very had conductor!^
of lieat ; and, therefore, prevent the loarmth
of the hcdy from being drawn off hj the c(M
air.
308.
Q. Do not AYOolens and furs actually r^-
part heat to the body ?
A. No ; they merely prevent the heat of
the body from escaping.
309.
Q. Where would the heat escape to, if
the body were not wraj^ped in wool or fur ?
A. The heat of the body would fly off
into the air ; for the cold air (coming in
contact with our body) would gradually
draw away its heaty till it was as cold as the
air itself.
310
Q. "What then is the principal use of cloth-
mg in winter time ?
A. 1st. — To prevent the animal heat
from escaping too freely ; and
2nd. — To protect the body from the eX"
ternal air (or wind,) which would carry
away its heat too rapidly.
311.
Q Why are beasts covered with fuTy hair
or wool?
CONDUCTORS OF HEAT.
89
A. Because fur, hair and wool, are very
^low conductors of heat; and (as dumb ani-
mals cannot be clad, like human beings)
God has given them a robe of hair or vjool,
to keep them tvarm.
312.
Q Why are birds covered v/ith down or
feathers ?
A. Because down and feathers are very
had conductors of heat ; and (as birds cannot
be clad, like human beings) God has given
them robe of feathers, to keep them warm.
313
Q. Why are wool, fur, hair and feathers^
such slow conductors of heat ?
A. Because a great quantity of air lurks
entangled between the fibres ; and air is a
very bad conductor of heat.
The warmest clothincr is thai which fits the body rather loosely ; because
more hot air will be confined by a moderately loose garment than by one
which fils the body tightly.
314.
Q. Why is moderately loose clothing
warmt ^ than that which fits tightly ?
A. Because air is a bad conductor ; and
the qumtity of air confined between our
bodies and clothing — prevents ;
Isf.- -The^ heat of our bodies from esrof-
ing ; and
8*
90
CHEMICAL ACTION.
2nd. — The external air from coming into
contact with om- bodies. But if our cloth
hig is sufficiently loose to admit of a free
drculatioii of air, we shall feel cold ; and on
the contrary if it fits very tightly it impedes
tlie free circulation of the blood and we
feel cold.
315.
Q. Does not the bad conducting power
of air enable persons to judge whether an
egg be new or stale ?
A. Yes ; touch the larger end of the
shell with your tongue ; if it feels warm^
the egg is stale ; if not^ it is new-laid.
316.
Q. Why will the shell of a stale egg feel
■warm to the tongue ?
A. Because the thick end of an egg con-
tains a small quantity of air (between the
shell and the white;) when the egg is stale
the white shrinks, and the confined air ac-
cordingly expands.
317.
Q. Why do we feel colder in windy wea-
ther than in a calm day ?
A. Because the j)articles of air pass over
us more rapidly; and every fj-esh ])article
t^akes from us some portion of heat.
CONDUCTORS OiP flEAT. 91
318.
Q. Show the wisdom of God in making
the air a bad conductor ?
A. If air were a good « onductor [like iron
ftnd stone) heat Avould be drawn sc rapidly
from our body, that we should be chilled ta
death. Similar evils would be felt also l>y
all the animal and vegetable world.
319.
Q. Why are rooms much warmer, for Ix!;-
ing furnished with double doors and loin-
doios ?
A. Because air is a bad conductor ; and
the air confined between the double door?"
and windows, opposes both the escape of
warm air out of the room, and of cold aii
into the room.
320.
Q. Why is a room warmer when the wm-
dow curtains are drawn or the shutters shut ?
A. Because air is a bad conductor ; and
the air confined between the curtains or
shutters and the window, opposes both the
escape of warm air out of the room, and of
cold air into it.
321.
Q. Why does linen shirt feel colder than
ft cotton one ?
92
CHEMICAL ACTION.
A. Because linen is a much better condut-
tor than cotton ; and, therefore, (as soon as
it touches the bod 7) it draws away the heat
more rapidly, and produces a greater sensa-
tion of cold,
322.
Q. Why is the face cooled hy wiping the
temples with a fine cambric handkerchief?
A. Because the fine fibres of the cam-
bric have a strong capillar?/ attraction for
moisture, and are excellent conductors of heat:
in consequence of which, the moisture and
heat are abstracted from the face by the cam-
bric, and a sensation of coohiess produced.
" Capillary attraction," i. e. the attraction of a thread or hair. Thti
wick of a candle is wet with grease, because the melted tallow runs up
die cotton from capillary attraction.
323.
Q. Why would not a cotton handkerchief
do as well ?
A. Because the coarse fibres of cotton
Iiave very little capillary attraction, and
are very bad conductors ; in consequence of
which, the heat of the face would be in-
creased (rather than diminished) by the u&'e
of a cotton handkerchief.
324.
Q. Is the earth a good conductor of heat?
A. No ; the earth is a very bad conduc-
tor of heat.
CONDUCTORS OF HEAT.
93
325.
Q. Wliy is the earth a had conductor of
heat ?
A. Because its particles are not contma^
^us ; and the power of conducting heat le
pends upon the continuity oj matter .
326.
Q. Why is the earth {below the surface)
warmer in winter than the surface itself?
A. Because the earth is a had conductor
of heat; and, therefore, (although the
ground be frozen,) the frost never pene-
trates more than a few inches helow the sur-
face.
327.
Q. Why is the earth (below the surface)
cooler in summer than the surface itself?
A. Because the earth is a had conductor
of heat ; and, therefore, (although the sur
face he scorched with the burning sun,) the
intense heat cannot penetrate to the loots
of the plants and trees.
328.
Show the wisdom of God in making the
earth a had conductor ?
A. If the heat and cold coidd penetrate the
earth (as freely as the heat of a fire pene-
trates iron,) the springs would be dried up
94
CHEmCAL ACTION.
in summer, and frozen in winter ; and all
vegetation would perish.
329.
Q. Why does the Bible say, that God
^•^giveth snow like wool?''
A. Because snow (being a very had con*
duct or of heat) protects vegetables and seeds
from the frost and cold.
330.
Q. How does the non-conducting joower
of snow protect vegetables from the frost and
cold?
A. It prevents the heat of the earth from
being drawn off by the cold air which rests
upon it.
331.
Q. Why is water from a spring always
cool, even in summer 1
A. Because the earth is so had a conductor,
that the burning rays of the sun can pene-
trate only a few inches below the surface ;
in consequence of which, the springs of wa-
ter are not affected by the heat of sunimer
332
Q. Why is it cool under a shady tree in a
hot summer's day ?
A. 1st, — Because the overhanging fo-
liage screens off the rays of the sun ;
CONDUCTORS OF HEAT.
95
2nd. — As the rays of the sun are warded
ofi', the air (beneath the tree) is not heated
by the reflection of the earth ; and
3rd. — The leaves of the trees, bemg non-
conductors, allow no heat to penetrate them
333.
Q. Why do persons use paper or woolen
kettle-holders ?
A. Because paper and woolen are both
very had conductors of heat ; in consequence
of which, the heat of the kettle does not
readily pass through them to the hand.
334.
Q. Does the heat of the boiling kettle
fiever get through the woolen or paper kettle-
holder ?
A. Yes; but though the kettle-holder be-
came as hot as the kettle itself, it would
neyev feel so hot.
335.
Q. Why w^ould not the kettle-holder fed
so hot as the kettle, when both are of the
same temperature ?
A. Because it is a very bad conductor,
and disposes of its heat too slowly to be per-
reptible ; but metal (being an excellent con-
ductor) disposes of its heat so quickly, that
the sudden influx is pauiful.
90
CHEMIC.VL ACTION.
336.
Q Why is the bottom of a kettle nearly
cold when the water is boiling hot ?
A. Because black soot is a very bad con-
du dor of heat ; and, therefore, the heat of
thj boiling water takes some time before it
gets through the soot which adheres to the
bottom of the kettle.
337.
Q. Why is the lid of a kettle intensely hot
when the water boils ?
A. Because the bright metal lid is an
admirable conductor ; and, therefore, the heat
from the boiling water pours into our hand the
moment we touch it.
338.
Q. Why are ice-houses lined with strata ,
and generally white-washed on the outside ?
A. 1st. — Because straw is a very bad con-
ductor of heat, and, therefore, prevents the
external heat from getting to the ice ; and
2nd. — The white-washed roof and walls
prevent the absorption of heat.
339.
Q Why will a little oil on the surface of
water prevent its freezing ?
A. Because oil is a bad conductor, and pre-
vents heat from leaving the water.
CONDUCTORS OF HEAT.
97
340.
Q. A silver tea-si30on becomes more
heated by hot tea, than one of inferior me-
tal, (as German silver, pewter, etc. ;) why
is this ?
A Because silver is a better conductor
tlian German silver or pewter.
Oermnn silver is composed of tweuty-five parts of nickel, twenty-five cl
Bine, and fifiy of copper.
Pewter is, gener.illy speakincr, an alloy of tin and lead, sometimes with
a Jitle antimony or copper combined, in different proportions, according to
the purposes for which it is designed.
341.
Q. Why does a metal spoon (left in a sauce-
pan) retard the process of boiling ?
A. Because the metal spoon (being an
excellent conductor) carries off the heat from
the water ; and (as heat is carried oflf by the
spoon) the water takes a longer time to boil.
342.
Q. Why does paint preserve wood ?
A. 1st. — Because it covers the surface of
the wood, and prevents both air and damp
from penetrating into the pores ;
2nd. — Because paint (especially white
paint) being a had conductor, preserves the
wood of a more uniform temperature ; and
3rd.- — Because it fills up the pores of the
wood, prevents insects and vermin from
harboring therein and eating up the fibre.
9
98
CHEMICAL ACTION.
343.
Q. Why are the fire-irons intensely hot^
when they rest against the stove which con-
tains a good fire ?
A. Because they are excellent conductors oj
heaty and draw it rapidly from the stove with
which they are in contact.
344.
Q. Why are tin foot-warmers covered with
flannel ?
A. 1st.— That the polish of the tin may
not be injured ;
2nd.— Because the flannel (being a very
bad conductor) helps to keep the tin hot
longer; and
3rd. — Lest the conducting surface of the
tin should feel painfully hot.
345.
Q What disadvantage would it be, if the
polish of the tin were injured ?
A. If the tin foot- warmer were to lose its
polish^ it would get cold in a much shorter
time.
346.
Q. Why are furnaces and stoves (where
much heat is required) built of porous bricks ?
A. Because bricks are bad conductors, and
prevent the escape of heat ; in consequence of
CONVECTION.
99
which, they are employed where great heat
is required.
347.
Q. Why are furnace doors, etc., frequently
covered with a paste of clay and sand ?
A. Because this paste is a very bad con^
ductor of heat ; and, therefore, prevents the
^cape of heat from the furnace,
343.
Q. If a stove be placed in the middle of a
room, should it be made of bricks or iron ?
A. A stove in the middle of a room should
be made of iron ; because iron is an excel-
lent conductor, and rapidly communicates
heat to the air around.
§ II. — Convection,
349.
Q. What is meant by the convection of
heat?
A. Heat communicated by being carried
to another thing or place ; as the hot water
resting on the bottom of a kettle carries heat
to the water through v/hich it ascends.
350.
Q, Are liquids good conductors of heat?
A. No; liquids are bad conductors ; and
are, therefore, made hot by convection.
100
CHEMICAL ACTION.
351.
Q. Why are liquids had conductors of heat ?
A. Because heat converts a liquid into
steam ; and flies off with the vapor instear]
of being conducted through the liquid.
352
Q. Explain how water is made hot ?
A. The water nearest the fire is first heat-
ed, and (being heated) rises to the top ;
while its place is supplied by colder portions,
which are heated in turn, till all the water
is boiling hot
353.
Q. Why is water in such continual fer-
ment^ when it is boiling ?
A. This commotion is mainly produced
by the ascending and descending currents of
hot and cold water.
The eecape of steam from the water contributes also to increase this agi-
tation.
354.
Q. How do these two currents pass eacli
other ?
A. The hot ascending current rises up
through the centre of the mass of water ;
while the cold descending currents pass dowD
by the metal sides of the kettle.
Foi other questions on the subject of l>oil\ng water, see p. 113 etc.
CONVECTION.
101
355.
Q. Wliy is heat applied to the bottom y and
not to the top of a kettle ?
A. Because the heated water always
mcends to the surface, heating the water
through which it passes ; if, therefore, heat
were applied to the top of a vessel, the wa-
fer beloio the surface would never be heated,
356.
Q. As the lower part of a grate is made
red-hot by the fire Sove, why would not the
water boil, if fire were applied to the top of
a kettle ?
A. The iron of a grate is an excellent
conductor ; if, therefore, one part be heated,
the heat is conducted to every other part ;
But water is a very had conductor, and will
not diffuse heat in a similar way.
357.
Q. Prove that water is a had conductor of
heat ?
A. ^Vhen a blacksmith immerses his red-
hot iron in a tank of water, the water which
surrounds the iron is made hoiling hot, while
that heloiv the surface remains quite cold
353.
Q. If you wish to cool liquids, where
should the cold be applied ?
9*
102
CHEMICAL ACTION.
A. To the top of the liquid ; because the
told portions will always descend^ and allow
the warmer parts to come in contact with
tlie cooUng substance.
359.
Q, Does boiling water get hotter by be-
ing kept on the fire ?
A No ; — not if the steam be suffered to
escape.
360.
Q. Why does not boiling water get hotter,
if the steam be suffered to escape ?
A. Because the water is converted into
steam as fast as it boils; and the steam
carries away the additional heat.
361.
Q. Why does soup keep hot longer than
boiling water ?
A. Because the grease and various ingre-
dients floating in the soup, oppose the
ascending motion of the hot particles, and
prevent their rising so freely to the surface
362.
Q. If you wanted to keep water hot for a
long time, how could it be done ?
A. By adding a little starch or flour to
the water.
CONVECTION.
103
363.
Q. Why would a little starch, added to
boiling water, serve to keep it hot ?
A. Because it would oppose the ascend*
5iig motion of the hot particles of water,
and j^i'ovent their rising so freely to the
surface.
364.
Q. Why do Indian mush, rice milky Sfc, re-
main hot longer than water ?
A. Because the ascending motion of the
hot particles is opposed by the mush or
rice, and cannot so quickly reach the sur-
face.
365
Q. How is air heated ?
A. By convective currents."
366.
Q. Explain what is meant by convective
currents?
A. When a portion of air is heated, it
rises upwards in a current, carrying the heat
with it ; other colder air succeeds, and (being
heated in a similar way) ascends also; These
are called convective currents.'^
('* Convective currents so called from the Ljitin words, cum-vectui
\carrieJ with ;) because the heat is " carried with the current.)
104
CHEMICAL ACTION.
367.
Q. Is air heated by the rays of the sun?
A. No ; air is not heated (in any sensible
degree) by the action of the sun's rays pass-
ing through it.
368.
Q. Why then is the air hotter on a sunny
diiy^ than on a cloudy one ?
A. Because the sun heats the surface of
the earth, and the air (resting on the earth)
is heated hy contact : as soon as it is heated
it ascends ; while its place is supplied by
colder portions which are heated in turn
also.
369.
Q. If air be a had conductor^ why does
hot iron become cold by exposure to the air ?
A. Because it is made cold;
1st. — By convection and,
2nd. — By ^'radiation."
370.
Q. How is hot iron made cold by convec-
tion ?
A. The air resting on the hot iron (being
intensely heated,) rapidly ascends with the
heat it has absorbed ; colder air succeeding
ihsiirhs more heat and ascends also ; and thii?
CONVECTION.
105
process is repeated till the hot iron is cooled
completely down.
371.
Q. How is broth cooled by being left ex<
posed to the air ?
A. It throws off some heat by radiatim ;
but it is mainly cooled down by convection,
372.
Q. How is hot broth cooled down by con*
vection ?
A. The air resting on the hot broth (being
heated) ascends; colder air succeeding ab-
sorbs more heat, and ascends also; and this
process is repeated till the broth is made cool.
The particles on the surface of the broth sink as they are cooled down,
and warmer particles rise to the surface ; which gradually assists the cooU
ing process.
373.
Q. Why is hot tea and broth, cooled faster
by being stirred about ?
A. 1st. — Because the agitation assists in
bringing its hottest particles to the surface.
2nd. — The action of stirring agitates the.
air, and brings it more quickly to the broth
or tea : and
3d. — As the hotter particles are more
rapidly brought into contact with the air,
therefore, convection is more rapid.
lilov/ing tea or broth cools it also.
106
CHEMICAL ACTION.
374.
Q. How does blowing hot food make ii
tool?
A. It causes the air (which has been
lieated by the food) to change more rapidly,
and give place to fresh cold air.
375.
Q. If a shutter be closed in the day-
time, the stream of light (piercing through
the crevice) seems in constant agitation. —
Why is this ?
A. Because little 7noteB and particles of
dust (thrown into agitation by the violence
of the convective currents^) are made visible
by the strong beam of light thrown into
the room through the crevice of the shut-
ter.
376.
Q. When potatoes are boiled, why are
those at the top of the boiler, cooked sooner
til an those nearer the fire ?
A. 1st.— -Because the hottest particles of
the water rise to the top of the boiler, and
the coldest particles sink to the bottom ; and
2nd — -Because the top of the boiler is
always enveloped with very hot escaping
Bteam ; in consequence of w^hich, the pota-
toes on the top are subjected to more in-
CHANGE OF STATE
107
tense heat, than those at the bottom of the
boiler.
377.
Q. Why does milk boil more quickly than
water.
A. Milk is a thicker liquid than water,
and consequently less steam escapes through
the thick liquid (milk,) than through the
thin liquid (water;) therefore, the heat of
the whole mass of the milk rises more
quickly.
SECTION III. CHANGE OF STATE.
378.
Q. What does change of state mean ?
A. The change which a substance under-
goes on exposure to heat — Thus, cold water
boils, or if the temperature be reduced, it
freezes. Some solid substances, such as
wax, or metals change their state and liquify
bj heat.
379.
Q Why does melted wax become hard
^hen cold?
A. Because the particles collapse ; and,
being packed more closely together, form a
solid.
The sole difference between a liquid and a solid, is this — In a solid che
panicles are packed more closely together, than ihey are in a liquid. TTie
leiidency of heat is to drive the particles /arf/igr avart from each othei» and
thus to liquify solids.
108 CHEMICAL ACTION.
380.
Q. Why will hot iron bend more easily
than cold ?
A. Because it is not so solid. The parti*
nles are driven farther apart by heat, and
the attraction of cohesion is thereby weak-
c-ned ; therefore, the particles can be made
10 move on each other more readily.
By a still further application of heat, the particles will be driven so far
asunder from each other, that the solid iron "will liquify ; in which state
the particles will move on each other almost without resistance.
381.
Q. Why does hot water freeze more quickly
than cold ? ^
A. Because there is a slight agitation on
the surface of hot water, which promotes ^
congelation, by assisting the crystals to
change their positions, till they take up that
which is most favorable to their solidifica-
tion.
Other caufes may have a minor influence, as for example: In hot water,
♦he particles are subdivided into smnller globules by the heat, and offer
less resistance to the action of cold than larger ones.
382.
Q. Why are some things solid, others
liquid, and others gaseous ?
A. Because the particles which compose
some things are nearer together than they
are in others. Those in which the parti-
cles are closest are solid ; those in which they
CHANGE OF STATE.
109
are farthest apart are gaseous ; and the lest
liquid.
383.
Q. Why does heat change a solid (like
ice) first into a liquid, and then into a gas
A Because heat drives the component
jjarticles farther asunder; hence a certain
quantity of heat changes sohd ice into a
liquid — and a further addition of heat
changes the liquid into steam.
384.
Q. Is steam visible or invisible?
A. Steam is invisible ; but when it comes
in contact with the air (being condensed into
small drops) it instantly becomes visible.
385.
Q. How do you know that steam is irtvi-
sible ?
A. If you look at the spout of a boiling
kettle, you will find that the steam (which
issues from the spout) is always invisible
for about half an inch; after which it be-
comes visible.
336.
Q. Why is the steam invisible for half an
inch ?
A. Because the air is not able to con*
10
110
CHEMICAL ACTION.
dense it, as it first issues from the spout ;
but when it spreads and comes in contact
with a larger volume of air, the invisible
steam is readily condensed into visible drops.
3S7.
Q. Why do steam engines sometimes burst 1
A. Because steam is very elastic; and
this elasticity increases in a greater propor-
tion than the heat which produces it ; un-
less, therefore, some vent be freely allowed,
steam will burst the vessel which confines
it.
§ I. — Latent Heat.
388.
Q. Why does steam burn so much more
severely than boiling water ?
A. Steam condenses as soon as it is ex-
posed to the cold, and gives out all the heat
by w^hich it was produced ; therefore, as one
thousand degrees of heat become latent in
steam, it gives out that amount when con-
densed, which is much greater than boiling
water.
389.
Q. Is there heat even in ice ?
A. Yes ; but it is latent (that is, not per*
ceptible to our senses.)
Latent, fiom the Latin word, Laleo, ^to lie hid.)
LATENT HEAT.
Ill
390.
Q. How do you know there is heat, if
you cannot perceive it ?
A. Thus : The temperature of ice is 32''
by the thermometer ; but if ice be melted
over 0 fire, (though 140'' of heat are ab-
sorbed by the process) it will feel no hotter
than before.
391.
Q. What becomes of the 140° of heat
which w^ent into the ice to melt it ?
A. It is hidden in the water; or (to speak
more scientifically) it is stored up in a laterit
state,
392.
Q. How much heat may be thus secreted
or made latent ?
A. All things contain a vast quantity of
latent heat; but as much as 1140° of heat
may remain latent in water.
393.
Q. How can 1140° of heat be added ti)
water without being perceptible to our feel-
ings ?
A. 1st. — 140° of heat are hidden in wa-
ter, when ice is melted by the sun or fire ;
2nd. — 1000° more of heat are secreted,
when water is converted into steam. Thus,
112
CHEMICAL ACTION.
before ice is converted into steam, 1140° of
heat become latent.
One pint of boiling: water (212° according to the thernjometer) wil
make eighteen hundred pints of steam; but the steam is no hotter to the
touch than boiling water ; both are 212*^, therefore, when water is coo'
verted into s-team, 1000^ of heal become latent. Hence, before ice i&
Verted into steam, it must contain 1140'^ of latent heat.
394.
Q. Why does cold water poured on lime
make it intensely hot ?
A. Because heat is evolved by the chemi-
cal action which takes place, when the cold
water combines with the lime.
N. B. Heat is always evoZfed, when a fluid is converted into a solid form.
Heal is always absorbed^ when a solid is changed into a liquid state. Aa
the water is changed from its liquid form when it is taken up by the lime
therefore, heat is given off.
335.
Q. Where does the heat come from ?
A. It was in the water and lime before ;
but was in a latent state.
396.
Q. Was there heat in the cold water and
lime before they were mixed together ?
A. Yes ; All bodies contain heat ; the
coldest ice as well as the hottest fire.
397.
Q. Explain by illustration what you
mean ?
A. Water is cold, and sulphuric «icid ia
cold ; but if these two cold liquids be mixed
together, they will produce intense heat.
EBULLITION.
113
§ II. — Ebulliiion,
393.
Q. What is ebullition ?
A. Ebullition, or boiling, is occasioned by
the formation of bubbles o£ vapor within the
body of the evaporating liquid, which rise
t^: the surface and then break.
399.
Q. Do all liquids boil at the same temper-
ature ?
A. No ; the boiling point occurs in differ-
ent liquids at very different temperatures.
400.
Q. Why does milk boil over more readily
than water ?
A. Because the bubbles of milk^ produced
by the process of boiling, are more tenacious
than the bubbles of water ; and these bub-
Wes, accumulating and climbing one above
another, soon overtop the rim of the sauce-
pan and run over.
401.
Q. Why does water simmer before it boils?
A. Because the particles of water 7iear
the bottom of the kettle (being formed into
steam sooner than the rest) shoot upwards ;
but are condensed again (as they rise) by t\e
colder water, and produce what is cnlled
simmering."
10*
114
CHEMICxa ACTION.
402.
Q. What is meant by simmering ?
A. A gentle tremor or undulation on the
surface of the water. When water simmers^
the bubbles collapse beneath the surface, and
the steam is condensed to water again ; but
Avhen water boils, the bubbles rise to the sur*
face, and the steam is thrown off.
Collapse, that is, burst.
403.
Q. Why does a kettle sing when the watei
simmers ?
A. Because the air (entangled in the wa-
ter) escapes by Jits and starts through the
spout of the kettle, which makes a noise like
a wind instrument.
404.
Q. Why does not a kettle sing when the
water boils ?
A. Because all the water is boiling hot ;
so the steam escapes in a continuous stream,
and not by fits and starts.
405.
Q. When does a kettle sing most?
A. ^Vlien it is set on the dde of the firt
to boil
406.
Q Why does a kettle sing more when W
EBULLITION.
115
is set oil the side of a fire, than Avlien it is
set in the midst of the fire ^
A. Because the heat is appHed so mu
equally, that one side is made hotter than the
other ; in consequence of which, the steam
is more entangled.
407.
Q. Why does a kettle sing, when the boil-
ing water begins to cool again ?
A. Because the upper surface cools jirst ;
and the steam (which rises from the lower
part of the kettle) is again entangled^ and
escapes by fits and starts.
403.
Q. ^Yhy does boiling water swell ?
A. Because it is expanded by the heat ;
that is — The heat of the fire drives the par-
ticles of water farther apart from each other ;
and (as they are not packed so closely together)
they take up more room ; in other words, the
water swells.
409.
Q What is meant when it is said, that
'^heat drives the particles of water farther
apart from each other?"
A. Water is composed of little globules,
like very small grains of sand ; the heat
drives these particles away from each other ;
116
CHEMICAL ACTION.
and (as they then require more rooin) the
water swells.
410.
Q. Why does boiling ivaier bubble ?
A . Because the vapor (rismg through the
water) is entangled, and forces up bubbles in
its effort to escape.
N. B. All liie air of water is expelled at the commencemeni of its boiling
411.
Q. ^¥lly does a kettle sometimes boil over ?
A. Because the water is expanded by heat ;
if, therefore, a kettle is filled with cold water ,
some of it must run over, as soon as it is ex-
panded by heat.
412.
Q. But I have seen a kettle boil over,
although it has not been filled full of water ;
how do you account for that ?
A, If a fire be very fierce, the air and va-
por are expelled so rapidly, that the bubbles
are very numerous ; and (towering one above
another) reach the top of the kettle, and fall
over.
413.
Q. Why is a pot (w^hich was full to over-
flowing, while the water was boiling hot) not
full, after it has been taken off the fire for
1 sliort time ?
EBULLITION
A. Because (while the water is boiling) it
is expanded by the heat, and fills the pot
even to overflowing ; but, when it becomes
cool, it contracts again, and occupies a inncl>
less space.
414.
Q. Why does the water of a kettle run jui
of the spout when it boils ?
A. Because the lid fits so tightly, that
the steam cannot lift it up and escape , be-
ing confined, therefore, in the kettle, it
presses on the water with great power, and
forces it out of the spout.
415.
Q. What causes the rattling noise^ so often
made by the lid of a saucepan or boiler ?
A. The steam (seeking to escape) forces
up the lid of the boiler, and the loeight of
the lid carries it back again; this being done
frequently, produces a rattling noise.
416.
Q. If the steam could not lift up the lid of
the boiler, how would it escape ?
A. If the lid fitted so tightly, that tlie
steam could not raise it up, the boiler would
hurst into fragments, and the consequences?
might be fatal.
417.
Q. When steam pours out from the spout
118
CHEfflCAL ACTION.
of a kettle, the stream begins apparently halj
an inch off the spout ; why does it not be-
gin close to the spout ?
A. Steam is really invisible ; and the half
inch (between the spout and the ''stream of
mist'') is the real steam, before it has been
condensed by air.
418.
Q. Why is not all the steam invisible as
v/ell as that half-inch ?
A. Because the invisible particles are
condensed by the cold air ; and, rolling one
into another, look like a thick mist.
419
Q. What becomes of the steam ? for it soon
vanishes.
A. After it has been condensed into mist,
it is dissolved by the air, and dispersed abroad
as invisible vapor.
420.
Q. And what becomes of the invisible vapoi ?
A. Being lighter than air, it ascends to tlje
upper regions of the atmosphere, where
(being again condensed) it contributes to form
douds.
421.
Q. Why will a pot (filled with water)
never boil, when immersed in another vessel
full of water also ?
EBULLITION.
119
A. Because water can never be heated
above the boiling point ; all the heat absorbed
by water after it boils y is employed in gene-
rating steam-,
422.
Q. How does the conversion of water
into steam, prevent the inner pot from hoiU
ing ?
A. As soon as the water in the larger
pot is boiling hot (or 212"*,) steam is formed
and carries off some of its heat ; therefore,
212"* of heat can never pass through it, to
raise the inner vessel to boiling heat,
423.
Q. Why do sugar, salt, ^c, retard the pro-
cess of boiling ?
A. Because they increase the density of
water ; and whatever increases the density
of a fluid, retards its boiling.
424.
Q. If you want water to boil without
the vessel containing it coming in contact
with the fire, what plan must you adopt ?
A. We must immerse the vessel (containinjL;
tlie water to be boiled^ in a saucepan con-
taining boiling brine, or syrup.
475.
Q. AVliy would the inner vessel boil, if
the outer vessel contained boiling brine ^
120
CHEMICAL ACTION-
A. Because brine will not boil, till it ia
raised to 218" or 220^ Therefore, 212" of
heat may easily pass through it, to raise th.
vessel immersed in it to boiling heat,
426.
Q. Wh}^ will brine impart to another ves-
sel more than 212°, and water not so much ?
A. Because no liquid can impart so high
a degree of heat, as its own boiling tempe-
rature : As water boils at 212" it cannot
impart 212" of heat : but, as brine will not
boil without 218" of heat, it can impart
enough to make water boil.
427.
Q. Why can liquids impart no extra heat,
after they boil ?
A. Because all extra heat is spent in
making steam. Hence water will not boil a
vessel of water immersed in it, because it
cannot impart to it 212" of heat ; but brine
will, because it can impart more than 212"
of heat, before it is itself converted into
steam.
Ether boils at . . 100 degs.
Alcohol, . . . 173^ "
Wnter, . . . , 212
Water, with one-
fiflhsah, . . 219 "
Syrup boils at . . 21 deg$ •
Oil of Turpentine, . 314 "
Sulphuric acid, . . 472 "
Linseed oil, . . . 640 "
Mercury, .... 656
Ar.y liquid which boils at a lower degree can be made to boil, if in
merged in a liquid which boils at a higher degree. Thus a cup of ether van
be made to boil in a saucepan of water. A cup of water in a saucepan of
hrine or syrvp. But a rvp of water will not boil, if immersed in ether ; nor
a rvp of syrvp in water.
EVAPORATION.
121
§ 111 — Evavoration,
428.
Q What is meant by evaporation ?
A. The dissipation of liquid by its i^on-
version into vapor.
429.
Q. What effects are produced by evapora-
tion?
A. The liquid vaporized absorbs heat from
the body whence it issues ; and the body
deprived of the liquid by evaporation, loses
heat.
430.
Q. If you wet your finger in your mouth,
and hold it up in the air, why does it feel
cold?
A. Because the saliva quickly evaporates ;
and (as it evaporates) absorbs heat fro7n the
finger, making it feel cold.
431.
Q. If you bathe your temples with ether,
why does it allay inflammation and feverish
heat ?
A. Because ether very rapidly evaporates;
and (as it evaporates) absorbs heat from the
hnrning head, producing a sensation of cold.
432.
Q Why is ether better for this purpose
than xoater?
11
122 CHEMICAL ACTION.
A. Because ether requires less heat to con
vert it into vapor ; in consequence of which,
it evaporates more quickly.
N. B. Ether is converted into vapor with 100° of heat; but water rt^
quires 21?^ of heat to convert it into steam,
433.
Q. Why does ether very greatly relieve a
scald or hum ?
A. Because it evaporates very rapidly: and
(as it evaporates) carries off the heat of the
burn.
434.
Q. Why do we feel cold^ when we have
wet feet or clothes?
A. Because the wet of our shoes or
clothes rapidly evaporates; and (as it evapo-
rates) absorbs heat from our body, which
makes us feel cold.
435.
Q. Why do wet feet or clothes give us
cold?''
A. Because the evaporation absorbs heat
hO abundantly from the surface of our body,
that its temperature is lowered belou) its natur
ral standard; in consequence of which,
health is injured.
436.
Q. Why is it dangerous to sleep in a damp
bed?
EVArORATIOiN.
128
A. Because the heat is contmually ab-
sorbed from the surface of our body, to ton-
virt the damp of the sheets into vapor ; hi
consequence of which, our animal heat is
reduced helow the healthy standard.
437.
Q. Why is health injured^ when the tem-
perature of the body is reduced below its na-
tural standard ?
A. Because the balance of the circulation
is destroyed. Blood is driven away from
the external surface by the chilly and thrown
upon the internal organs, which are oppressed
by this increased load of blood.
438.
Q. Why do we not feel the same sensa-
tion of cold, if we throw a macinto'ih* over
our wet clothes ?
A. Because the macintosh (being air
tight) prevents evaporation: and (as the wet
cannot evaporate) no heat is absorbed from
our bodies.
439.
Q. Why do not sailors get cold, who are
frequently wet all day with sea-water ?
A. 1st. — Because the salt of the sea re-
tards evaporation ; and (as the heat of their
*A macintosh is a waterproof-coal.
124
CIIEMCAL ACTION.
body is drawn off gradually) the sensation
of cold is i)revented.
2nd. — The salt of the sea acts as a stimu-
lant, and keeps the blood circulatmg in the
skin.
440.
Q. Why does sprinkling a hot room with
water cool it ?
A. Because the heat of the room causes
a rapid evaporation of the sprinkled water:
and as the water evaporates, it absorbs heat
from the room, which cools it.
441.
Q. Why is it customary, in very hot conn-
tries, to sit in rooms separated by curtains,
instead of walls or doors; and to keep these
curtains constantly sprinkled with water ?
A. Because curtains are bad conductors
of heat ; and the rapid evaporation of water
reduces the temperature of the room ten or
fifteen degrees.
442.
Q. Why does watering the streets and
roads cool them ?
A. Because they part with their heat to
promote the evaporation of the water sprinkled
rm them.
EVAPORATION.
125
443.
Q. Why does a shower of I'aiit toul the
flfr ii) summer-time ?
A. Because the wet earth parts with its
hmt to promote evaporation : and when the
earth is cooled, it cools the air also.
444.
Q. Why is linen dried by being exposed
to the wind ?
A. Because the wind accelerates evapora-
tion, by removing the vapor from the sur-
face of the ivet linen ^ as fast as it is formed.
445.
Q. Why is linen dried sooner in the open
air^ than in a confined room ?
A. Because the particles of vapor are
more rapidly removed from the surface of
the linen by evaporation.
446.
Q. Why are wet summers generally suc-
ceeded by cold winters ?
A. Because the great evaporation (car-
ried on through the wet summer) reduces
the temperature of the earth lower than usual ^
and produces cold.
447.
Q. Why are our eastern and many of oui
western states warmer, and the winters less
j^rere than formerly?
11*
]26 CHE^UaVL ACTION.
A. Because they are better drained and
better rMltivated.
448.
Q. Why does draining land promote
warmth ?
A, Because it diminishes evaporation ; in
consequence of which, less heat is abstracted
from the earth.
449.
Q. Why does cultivation increase the
warmth of a country ?
A. 1st. — Because hedges and belts of trees
are multiplied :
2nd. — The land is better drained : and
3rd. — The vast forests are cut down.
450.
Q. Why do hedges and belts of trees pro-
mote warmth ?
A. Because they retard evaporation y b>
keeping off the wind.
451.
Q. If belts of trees promote loarmthy why
do forests produce cold?
A. 1st. — Because they detain and con-
dense thp passing clouds :
2nd. — They prevent the access of both
v:ind and sun :
EVAPORATION.
127
3rd. — The soil of forests i:^ always covered
w^th long damp grass, rotting leaves^ and thick
brushwood: and
4th. — In every forest there are always
many hollows /z/// of stagnant water.
452.
Q. Why do long grass and rotting leaves
jiromote cold ?
A. Because they are always damp ; and
evaporation, which they promote, is con-
stantly absorbing heat from the earth be-
neath.
453.
Q. Why are France and Germany warmer
now, than when the vine would not rij)en
there ?
A. Chiefly because their vast forests have
been cut down; and the soil is better drained
and cultivated.
454.
Q. What becomes of the water of ponds in
summer-time ?
A. Ponds are often left dry in summer-
time, because their water is evaporated by the
air.
455.
Q. How is this evaporation produced and
carried on ?
128
CHEMICAL ACTION.
A. The heat of the air changes the siu
face of tM ivater into vapor ^ which (blending
with the air) is soon wafted away ; and simi-
lar evaporation is repeatedly produced, till
the pond is left quite dry.
456.
Q. Why are the wheels of some machines
kept constantly wet with water ?
A. To carry off (by evaporation) the heat
which arises from the rapid motion of the
wheels.
457.
Q. Why is the surface of the ground
hardened by the sun ?
A. Because the moisture of the ground is
exhaled by evaporation ; and, as the earthy
particles are brought closer together, the
mass becomes more solid.
458.
Q. Show the wisdom of God in this ar-
rangement.
A. If the soil did not become crusty and
hard in dry weather, the heat and drought
would penetrate the soil, and kill both seeds
and roots.
459.
Q. Why does bread become hard al'tor it
has been kept a few days ?
EVAPORATIO^.
129
A. Because the vapor and gases escape,
leaving the solid particles dry ; so that they
collapse and become more solid and hard»
460.
Q. Why are glue^ g^^, starch and paste
adhesive ?
A. Because the water used wiih them ra-
pidly evaporates, and leaves them solid ; and
they insinuate themselves so intimately
into the pores of the substances with which
they come in contact, that when the water
evaporates, the whole is one solid mass.
They lose their adhesiveness when dissolved in water; and, tlierefire,
must always be suffered to become dry, before they will hold with tenacity
461.
Q. YvTiy is tea cooled faster in a saucer
than in a cup ?
A. Because evaporation is increased by in-
creasing the surface ; and, as tea in a saucer
presents a larger surface to the air, its heat is
more rapidly carried off by evaporation.
It is also cooled by convection — (See Chap. III., Sec. II., § II.)
462.
Q. Why is not the vapor of the sea salt ?
A. Because the salt is always left behind,
in the process of evaporation.
463.
Q. What is that white crust, which ap-
130
CHEMICAL ACTION.
pears (in hot weather) upon ckthes wetted
by sea water ?
A. The salt of the water, left on the
clothes by evaporation.
464.
Q, Why does this white crust always dis-
appear in wet weather ?
A. Because the moisture of the air dissolves
the salt ; in consequence of which, it is no
longer visible.
465.
Q. Why should not persons, who take
violent exercise, wear very thick clothing ?
A. Because it prevents the perspiration
from evaporating. When the heat of the
body is increased by exercise, perspiration
reduces the heat (by evaporation) to a healthy
standard; as thick clothing prevents this
evaporation, it is injurious to health.
466.
Q. Wliy will not lucifer matches ignite
if they are damp ?
A. 1st. — Because the cold, produced hy
the evaporation of the water, neutralizes the
heat produced by the friction of the match
across the bottom of the lucifer box ; and,
2nd. — Because the damp prevents the
free accession of oxygen to the match, with-
r>ut which it cannot burn.
VAPORIZATION.
133
467.
Q, Why does water in a very exposed
place freeze more rapidly, than that which
is under cover, or in a place less exposed ?
A. 1st. — Because evaporation goes on
more rapidly when water is exposed ; and
carries away heat from the general mass ;
and,
2nd. — Any covering will radiate hmt into
the water below, and prevent the mass from
cooling down to the requisite temperature
to cause congelation.
468.
Q. Why does paint often blister from heat?
A. Because the heat, penetrating through
paint, extracts some little moisture from the
wood, and turns it into vapor or steam. As
this vapor requires room, it throws up
blisters in the paint to make room for it?!
expanded bulk.
§ IV. — Vaporization,
469.
Q. What is meant by vaporization ?
A. The conversion of a solid or liquid into
vapor ; as snow or water is converted into
vapor by the heat of the sun.
132
CHEMICAL ACTION.
470.
Q. Explain the difference between eva-
poration and vaporization ?
A. Evaporation is effected by exposure
to the air, without boiling ; whilst vapori-
zation requires the air of sufficient heat to
produce ebullition.
" Ebullition,** boiling.
471.
Q. Why does hot iron make a hissing
noise when plunged into water ?
A. Because the hot iron converts into
steam, the particles of water which come in
immediate contact with it; and, as the
steam flies upwards, it passes by other par-
ticles of water not yet vaporized ; the colli-
sion produces very rapid vibrations in the
air, and a hissing noise is the result.
472.
Q. Why does ivater make a hissing noise
v/hen it is j)oured on fire ?
A. Because the part which comes in con-
tact with the fire is immediately converted
into steam ; and, as it flies upward, meets
other particles of water not yet vaporized ;
the collision produces very rapid vibra-
tions in the air, and a hissing noise is the
result.
VAPORIZATION,
133
473.
Q. Why is water converted into steam hy
the heat of the fire ?
A. Because, when the heat of the fire en-
ters the water, it separates its globules into very
rTzmw/epar/fc/e^; which (being lighter than air)
Oy off from the surface in the form of steam.
474.
Q. Why do doors swell in rainy weather?
A. Because the air is filled with vapor,
which (penetrating into the pores of the
wood) forces its particles farther apart , and
swells the door.
475.
Q. Why do doors shrink in dry weather ?
A. Because the moisture is absorbed from
the wood ; and, as ihe particles are brought
closer together, the size of the door is lessened
— in other words, the wood shrinks.
476.
Q. Why is the air filled with offensive
smells, just previous to a coming rain ?
A. Because the volatile parts which rise
from dunghills, sewers, etc., are prevented
(by the vapor of theazV) from mmg so readily,
as when the sun is shining brightly.
477.
Q. Why do flowers smell sweeter and
stronger, just previous t) rain?
12
134
CHEMICAL ACTION.
A. Because the volatile particles wliici
constitute the perfume of flowers, are pre-
vented (by the vapor of the air) from risino: ;
in consequence of which, they are confined
to the lower regions of the atmosphere.
N B. MaTiy essential oils and other volatile substances, which produce
odors in plants, require the presence of much moisture for their perfect
developement.
478.
Q. Why do horses and other animals
stretch out their necks, and snuff up the air^
just pre vious to a fall of rain ?
A. Because they smell the odor of plants
and hay, and delight to snuiBF in their fra-
grance.
479.
Q. Why does smoke fall, when rain is at
hand ?
A. Because the air is less dense, and can-
not buoy up the smoke so readily as dry and
heavy air.
480.
Q. Wh}^ does a downward current of cold
air bring rain ?
A . Because it condenses the warm vapor ;
which (being condensed) descends in rain.
481.
Q. Why does a drop of water sometimes
roll along a piece of hot iron, without leav-
uig the least trace ?
LIQUEFACTION .
135
A. Because the bottom of the drop is
turned into vapor, which buoys the drop up,
without allowing it to touch the iron.
482.
Q. Why does it roll ?
A. Because the current of air (which is
always passing over a heated surface) drives
'/ alcng.
483
Q. Why does a laum^ ess put a little saliva
on a flat-iron, to know if it be hot enough ?
A. Because when the saliva sticks to the
iron, and is evaporated, she knows it is not
sufficiently hot ; but, when it runs along the
iron, it is.
484.
Q. Why is the flat-iron hotter if the saliva
runs along it, than if it adheres till it is
evaporated ?
A. Because when the saliva runs along
the iron, the heat is sufficient to convert the
bottom of the drop into vapor ; but, if the
saliva will not roll, the iron is not sufficiently
hot to convert the bottom of the drop into
vapor-
§ \r, — Liquefaction
485.
Q. What is meant by liquefaction?
136
CHEAOCAL ACTION.
A. The state of being melted ; as ice is
melted by the heat of the sun.
486.
Q Why is ice melted by the heat of (he
sun ?
A. Because, when the heat of the mn
enters the solid ice, it forces its particles
asunder ; till their attraction of cohesion is
sufficiently overcome, to convert the solid ice
into a liquid.
487.
Q. The temperature of ice is 32° ; if you
pour just enough boiling water over the ice
to melt it, will the temperature of the wa-
ter be increased ?
A. No ; the heat of the water is con-
sumed in melting the ice ; but pour boilhig
water on ice-cold water, and the tempera-
ture is immediately increased.
483.
Q. Why does wax become soft before it
turns liquid ?
A. Because it absorbs heat sufficient to
loosen the contact of its particles, before it
has absorbed sufficient to liquefy the mass.
489.
Q. Why are metals melted by the heat of
fire?
RADIATION.
137
A. Because, when the heat of the lire
enters the solid metal, it forces its particles
asvnder ; till their attraction of cohesion is
vsufficiently overcome, to convert the solid
metal into a liquid.
490.
Q. Why does not wood melt like metal ?
A. Because the heat of the fire decom-
poses the wood into gas, smoke, and ashes ;
and the different parts separate from each
other.
491.
Q. Why does salt crackle when thrown
into the fire ?
A. Salt contains water ; and the crackling
of the salt is owing to the sudden conversion
of this water into steam.
SECTION IV. RADIATION
492.
Q. What is meant by radiation ?
A. Radiation means the emission of rays ;
thus the sun radiates both light and heat ;
that is, it emits rays of light and heat in all
directions.
493.
Q. When is heat radiated from one body
to another?
12^
138
CHEMICAL ACTION.
A. When the two bodies are separated by
a non-conducting medhim ; thus the sun ra-
diates heat towards the earth, because the air
(whicli is a very bad conductor) comes he^
I ween.
494.
Q. On what does radiation depend?
A. On the roughness of the radiating sur-
face; thus, if metal he scratched y its radiating
power is increased ; because the heat has
more points to escape from.
495.
Q. Does a fire radiate heat ?
A. Yes; and because burning fuel emits
rays of heat, therefore, we feel warm when
we stand before a fire.
496.
Q. Why does our face feel uncomfortably
hot when we approach a fire ?
A. Because the fire radiates heat upon
the face ; which (not being covered) feels
the effect immediately.
497.
Q. Why does the fire heat the face more
than it does the rest of the body ?
A. Because the rest of the body is covered
with clothing; which (being a had cnri.
RADIATION.
139
ductor of heat) prevents the same sudden
and rapid transmission of heat to the skin.
498.
Q. Do those substances which ^-adiate heat
absorb heat also ?
A. Yes. Those substances which ) adiaff'
most, also absorb most heat ; and those which
radiate least, also absorb the least heat.
499.
Q. Does anything dse radiate heat besides
the sun and fire ?
A. Yes ; all things radiate heat in some
measure, but not equally well,
500.
Q. What things radiate heat the next best
to the sun and fire ?
A. All dull and dark substances are good
radiators of heat ; but all light and polished
substances are bad radiators.
501.
Q. What is meant by being a "bad radia-
tor of heat?''
A. To radiate heat is to throw o f heat by
rays, as the sun ; a polished tin pan does
not throio off the heat of boiling water from its
Burface, but keeps it in.
CHEMICAL ACTION
£02.
Q. Why is a tin pan (filled with hot water j
as a foot-warmer ?
A. Because polished tin (being a bad ra-
diator of heat) keeps hot averylon^ time;
and warms the feet resting upon it.
503.
Q. Why would the tin foot-warmer get
cold sooner^ if the polish were injured ?
A. Because polished tin throws off its heat
very slowly ; but dull, scratched, painted, or
dirty tin, throws off its heat very quickly.
504.
Q. Why does snow (at the foot of a hedge
or loall) melt sooner than that in an open
field?
A. Because the hedge or wall radiates
heat into the snow beneath, which melts it.
505
Q, How is hot iron cooled by radiation ?
A. While its heat is being carried off by
"convection,'' the hot iron throws off heat
(on all sides) hy radiation also.
506.
Q. Why should the flues (connected with
stoves, etc.,) be always blackened ^Yith black
lead^
A , In order that the heat of the fine moy
RADIATION
141
be more readily difused throughout the
room . Black lead radiates heat more freely
than any other known substance.
In lieaiinnf a room with steam it would be absurd to use black pipti (as
coiiveyijiff the feieam, because ihey would tend to cool the ho vapor,
507.
Q. Why does a polished metal tea-pot make
better tea than a black earthen one ?
A. Because polished m?tal (being a very
bad radiator of heat) keeps the water hot much
longer; and the hotter the water is, the
better it draws" the tea.
508.
Q. Why will not a dull black tea-pot make
good tea ?
A. Because the heat of the water flies of
so quickly through the dull black surlace of
the tea-pot, that the water is very rapidly
cooled, and cannot "draw" the tea.
509.
Q. Do not the poorer classes generally
prefer the little black earthen tea-pot to the
bright metal one ?
A. Yes ; because they set it near the fire
^^to draw ;" in which case, the little black
tea-poi will make the best tea.
510.
Q. Why will a black tea-pot make better
142
CHEMICAL ACTION.
tea than a bright metal one, if it be set neai
the fire to draw ?
A. Because the black tea-pot will ahsorb
heat plentifully from the fire, and keep the
water hot ; whereas a bright metal tea-pot
(set near the fire) would throw off the heat
by reflection.
511.
Q. Then sometimes a black earthen tea-
pot is the best, and sometimes a bright
metal one ?
A. Yes ; when a tea-pot is set on the
stove "to draw^^ black earth is the hest^ be-
cause it absorbs heat ; but, when a tea-pot is
not set on the stove, bright metal is the best ;
because it radiates heat very slowly^ and,
therefore, keeps the water hot.
512.
Q. Would a metal pot serve to keep wa-
ter hot if it were dull and dirty ?
A. No. It is the bright polish of the
metal which makes it a bad radiator ; if it
were duU^ scratched^ or dirty y the heat would
escape very rapidly.
Wate^ in hot weather is also kept cooler in bright raeta than in dull oi
earthen vessels.
513.
Q, Why are dinner-covers made of hrighl
tin or nlver ?
RADIATION.
143
A Because light-colored and highly-
polished metal is a very had radiator of heat ;
and, therefore, bright tin or silver will not
allow the heat of the cooked food to escape
through the cover by radiation.
514.
Q. Why should a meat-cover be very
brightly polished ?
A. To prevent the heat of the food from
escaping from radiation. If a meat-cover
be dull or scratched, it will absorb heat from
the food beneath ; and, (instead of keeping it
hot) make it cold,
515.
Q. Wliy should a silver meat -cover be plain
and not chased ?
A. Because a chased meat-cover woukl
absorb heat from the food ; and (instead of
keeping it hot) make it cold.
516.
Q. Why is meat very subje<3t to taint on
a moonlight night ?
A. 'Because it radiates heat very freely in
a bright moonlight night ; in consequence
of which, it is soon covered with deio%
which produces rapid decomposition,
517
Q. How do moonlight nights conduce to the
rapid grovjth of plants.
144
CHEl\nCAL ACTION.
A. Radiation is carried on very rapidly
on bright moonlight nights; in consequence
of which, dew is very plentifully deposited
on young jolants, which conduces much to
their growth and vigor.
518.
Q. Why is the air (resting on the surface
of the earths colder than that in the higher
regions ?
A. Because the earth radiates more heat
than the leaves of lofty trees ; and, there-
fore, more rapidly condenses and freezes the
vapor of the air.
519.
Q. Why are shrubs more liable to be
frost-bitten than trees.
A. Because they do not rise far above
the surface of the earth ; and (as the air
contiguous to the earth is made colder by ra-
diation than that in the higher regions,)
therefore, the low shrub is often frost-bitten^
when the lofty tree is uninjured.
SECTION V. REFLECTION.
520.
Q. What is meant by reflecting heat ?
A. To reflect heat is to throw it hack in
REFLECTION.
145
rays from the surface of the reflecting body
towards the place whence it came.
521
Q. What are the best reflectors of heat ?
A, All bright surfaces and light colors.
522.
Q Are good absorbers of heat good refleC'
tors also ?
A. No; those things which absorb heat
best, reflect heat worst ; and those which re-
flect heat loorst, absorb it best.
523.
Q. Why are those things which absorb
heat unable to reflect it?
A. Because if anything sucks in heat like
a sponge, it cannot throw it off from its sur-
face ; and if anything throws off heat from
its surface, it cannot drink it in.
524.
Q. Why are reflectors always made of
light colored and highly polished metal ?
A. Because light colored and highly po-
lished metal makes the best of all reflectors.
525.
Q. Why do not plate-warmers blister and
fjcorch the wood behind ?
A. Because the bright tin front throws
(he heat of the fire back again, and will not
ullow it to penetrate to the wood behind.
13
U6
CHEMICAL ACTION.
526.
Q. If metal be such an excellent conduc-
tor of heat, how can it reflect heat, or ihrow
it off?
A. Polished metal is a conductor of heat
only when that heat is communicated by
actual contact : but whenever heat falls upon
bright metal in rays, it is reflected back again,
and the metal remains cool.
527.
Q. What is meant " by heat falling upon
metal in rays,^^ and not " by contact
A. If a piece of metal were thrust into
a fire, it would be in actual contact with the
fire ; but if it were held before a fire, the
heat of the fire would fall upon it in rays,
528.
Q. Why is a plate-warmer made of un-
painted bright tin ?
A. Because bright tin reflects the heat
(which issues from the fire in rays) upon
the meat ; and, therefore, greatly assists the
process of roasting.
Reflects the heat, that is, throws it lack upon the meat.
529.
Q. What is the use of the tin screen or
reflector used in roasting ?
A. It throws the heat of the fire back upon
fhe meat ; and, therefore, both assists the
REFLECTION.
147
process of roasting, and helps to keep th^
kitchzn cool.
530.
Q. How does a tin reflector tend to keep
(he kitchen cool?
A. By confining the heat of the fire to
the hearth, and preventing its disj)ersion
throughout the kitchen.
531.
Q. Why would not the tin reflector do as
well, if it were painted ?
A. Because it would then absorb heat, and
not reflect it at all. A plate-warmer should
never be painted, but should be kept very
clean, bright, and free from all scratches.
532.
Q. Wliy should a reflector be kept so very
clean and free from all scratches ?
A. Because if a reflector were spotted,
didl, or scratched, it would absorb heat, in-
stead of reflecting it; and, consequently,
would be of no use whatsoever as a re-
flector.
533.
Q. Why will not a polished tin pan, bake
bread as well as an iron one ?
A. Because the bright metal reflects the
heat ; and, therefore, will not brown the
lis
CHEMICAL ACTION.
enist which surrounds the bottom and side^i
of the pan ; consequently, the top of the
bread would be burnt before the bottom and
sides of the loaf were brown.
534.
Q. ^Yliy will a kettle be slower boiling if
the bottom and sides are clean and bright ?
A. Because bright metal does not absorb
heat, but reflects it; and (as the heat is
thrown off from the surface of bright metal
by reflection) therefore, a new kettle takes
a longer time to boil.
Reflects heat, that Is, throws it off.
535.
Q. Why do persons xoear lohite dresses in
summer time ?
A. Because white throws off the heat of
the sun by reflection, and is a very bad ab-
sorbent of heat ; in consequence of w^iich,
white dresses never become so hot from the
scorching sun as dark colors do.
536.
Q. Why do not persons wear white dressea
in winter time ?
A. Because white will not absorb heat, like
black and other dark colors j and, there-
fore, white dresses are not so ivarm as dark
ones.
ABSORPTION.
149
537.
Q. Why are shoes hotter for being dusty ?
A. Because dull, dusty shoes will absorb
heat from the sun, earth, and air ; but shoes
brightly polished throw off the heat of the
mn by reflection.
SECTION VI. ABSORPTION.
538.
Q. What is the difference between con-
ducting heat, and absorbing heat ?
A. To conduct heat is to transmit it from
one body to another through a conducting
medium. To absorb heat is to suck it up^ as
a sponge sucks U23 water.
539.
Q. Give me an example ?
A. Black cloth absorbs, but does not con-
duct heat ; thus, if black cloth be laid in the
sun, it will absorb the rays very rapidly ; but
if one end of the black cloth be made hot, it
would not conduct the heat to the other end.
540
Q. Are good conductors of heat good ab-
sorbers also ?
A. No ; Every good conductor of heat is a
had absorber of it ; and no good absorber of
hc-at can Ije ^ good conductor also.
13*
150
CHEMICAL ACTION.
541.
Q. Is iron a good absorber of heat ?
A. No; iron is a good conductor^ but a
very bad absorber of heat.
542.
Q. Why do the fire-irons (which lie upon
Cl fender) remain cold, although they are be-
fore a good fire ?
A. Because they are bad absorbers of heat;
in consequence of which, they remain cold,
unless they come in contact with the stove
or fire.
543.
Q. If a piece of brown paper be submitted
to the action of a burning glass, it will catch
fire much sooner than a piece of white paper
would ; explain the reason ?
A. Because white paper reflects the rays
of the sun, or throws them back ; in conse-
quence of which, it appears more luminous,
but is not so much heated as dark brorun
paper, which absorbs the rays, and readily
becomes heated to ignition.
Besides, brown paper is of a looker and more combustible fabric than
while paper.
544.
Q. Why is the temperature of islands moro
equable than that of continents ?
A. Because the loater around the island
ABSORPTION.
151
absorbs the extreme heat of summer; and
gives out heat to mitigate the extreme cold
of winter.
545.
Q. Islands are warmer in winter than con-
tinents. Explain the reason of this ?
A. Unless the sea be frozen (which is
rarely the case) it is warmer than the frozen
land ; and the warmth of the sea-air helps
to mitigate the intense cold of the land-air.
546.
Q. How does the ceaseless change of air
tend to decrease the loarmth of a nalved
body?
A. Thus: — the air (which cases the
body) absorbs as much heat from it as it
can, while it remains in contact; being then
blown away, it makes room for a fresh coat
of airy which absorbs more heat.
547.
Q. Does the air which encases a naked
body, become (by contact) as warm as the
hodj itself?
A. It would do so, if it remained motion-
less ; but, as it remains only a very short
time, it absorbs as much heat as it can in
the time, and passes on.
152
CHEMICAL ACTION.
548.
Q. Why does fanning the face in summei
make it cool ?
A. Because the fan puts the air in motion,
and makes it pass more rapidly over the face;.
and (as the temperature of the air is always
lower than that of the human face) each puff
of air carries off some portion of its heat.
549.
Q. Why do ladies fan themselves in hot
weather?
A. That fresh particles of air may be
brought in contact with their faces by the
action of the fan ; and as every fresh parti-
cle of air absorbs some heat from the skin,
this constant change makes them cool.
550.
Q. Does a fan cool the air ?
A. No; it makes the air hotter by im-
parting to it the heat out of onr face ; but
it cools our face by transferring its heat to
(he air.
551.
Q. Does /(Qfnnmg make the a/r itself coo/^r?
A. No ; fanning makes the air hotter and
hotter.
552.
Q. How does fanning the face increase
tlie heat of the air ?
ABSORPTION.
A. By driving the air more rapidly over
the liuman body, and causing it, consequent-
ly, to absorb more heat.
553.
Q. If fanning makes the air hotter ^ why
can it make a person feel cooler ?
A. Because it takes the heat out oj Iht
face, and gives it to the air.
554.
Q. Why is hroth cooled by blowing it ?
A. Because the breath causes a rapid
change of air to pass over the broth ; and
(as the air is colder than the broth) it con-
tinually absorbs heat from it, and makes it
cooler and cooler.
555.
Q. Would not the air absorb heat from
the broth just as well without bloiving ?
A. No; air is a very bad conductor ; unless,
therefore, the change be rapid , the air nearest
the surface of the broth would soon become a.s
hot as the broth itself,
556.
Q Would not hot air part with its heat
instantly to the circumjacent air ?
A. No ; not instantly. Air is so bad a
conductor, that it parts wdth its heat very
doiuhj ; unless, therefore, the air be kept in
154
CHEMICAL ACTION.
continual ?notiony it would cool the broth ver^
slowly indeed.
557.
Q. Why does wind generally feel cool?
A. Because it drives the air more rapidly
over our body ; and this rapid change of air
draws off a large quantity of heat.
558.
Q. Why does air absorb heat more quickly
by being set in motion ?
A. Because every fresh gust of air absorbs
1 fresh portion of heat ; and the more rapid
the succession of gusts, the greater will be
the quantity of heat absorbed.
559
Q. If the air were hotter than our body,
would the wind feel cool ?
A. No ; the air would feel insufferably
hot, if it were hotter than our body
560.
Q. Why would the air feel intensely hot,
\ f it were warmer than our body ?
A. Because it would add to the heat of
our body, instead of diminishing it.
561
Q. Is the air ever as hot as the human
hody?
ABSORPTION.
155
A. In some climates it is, and when that
is the case the heat is almost insupportable ,
Q. Why does a kettle boil faster, when
the bottom and sides are covered with soot 1
A. Because the hladz soot absorbs heat very
quickly from the fire, and the metal conducts
it to the water.
563.
Q. Why will not a new kettle boil so fast as
an old one ?
A. Because the bottom and sides of a new
kettle are clean and bright ; but in an old
kettle they are covered with soot, or black-
ened by the fire.
564.
Q. Why do we wear white linen and a
black outer dress, if we want to be warm ?
A. Because the black outer dress quickly
absorbs heat from the sun ; and, the white
linen (being a bad absorbent) abstracts no
heat from the warm body
533.
Q. What colors are warmest for dresses ?
A. For outside garments black is the
warmest, and then such colors as approach
nearest to black, (as dark blue and green.)
White is the coldest color for external clothing.
56
CHEMICAL ACTION.
566.
Q. Why are dark colors (for external
wear) so much warmer than light ones ?
A. Because dark colors absorb heat from
the sun more abundantly than light ones.
567.
Q. How can you prove that dark color?
tire warmer than light ones ?
A. If a piece of black and a piece of
lohite cloth were laid uj)on snow, in a few
hours the black cloth will have melted the snow
beneath ; whereas, the ivhite cloth will have
produced little or no effect upon it at all,
N. B. The darker any color is, the warmer it is, because it is a better
absorbent of heat. The order may be thus arranged : — 1, Black (warmesi
of all )— 2, Violet.--3, Indigo.— 4, Blue.— 5, Green.— 6, Red.— 7 Yellow :
and 8, while (coidest of all.)
568.
Q. Why are black kid gloves unpleasantly
hot for summer wear ?
A. 1st. — Because black absorbs the solar
heat ; and
2nd. — Kid will not allow the heat of our
hand to escape readily through the glove.
569.
Q. Why are Lisle f read gloves agreeably
cool for summer wear ?
A. 1st. — Because thread absorbs perspiru'
Hon: and
ABSORPTION
157
2nd. — It conducts away the heat of our
hot hands.
570.
Q. Are Lisle thread gloves absorbents of
heat ?
A. No; Lisle thread gloves are generally
of a grey or lilac color ; and, therefore, do
vot absorb solar heat.
571
Q. Why does hoar frost remain on to7nb'
stones long after it has melted from the
grass and gravd-walks of a church-yard ?
A. Because tomb-stones (being white)
will not absorb heat, like the darker grass
and gravel ; in consequence of which, they
remain too cold to thaw the frost congealed
upon their surface.
572.
Q. If black absorbs heat, why have ne'>
groes black skins, and not white skins, which
would not absorb heat at all ?
A. Because black will not blister from the
heat of the sun. Although, therefore, the
black skin of the negro absorbs heat more
plentifully than the white skin of a Euro-
pean ; yet the blackness prevents the sun
from blistering or scorching it,
573.
Q How is it known that the black color
14
i58
CHElVnCAL ACTION.
prevents the sun from either blistering os
scorching the skin ?
A* If you put a white glove on one hand,
and a black glove on the other (when the sun
is burning hot,) the hand with the white
love will be scorched, but not the other.
574.
Q Which hand will feel the hotter ?
A. The hand with the black glove will
feel the hotter, but will not be scorched by
the sun ; whereas, the hand with the tvhite
glove (though much cooler) will be severely
scorched.
575.
Q. Why does the black skin of a negro
never scorch or blister with the hot sun ?
A. Because the black color absorbs the heat
— conveys it below the surface of the skin —
and converts it to sensible heat and perspira-
tion.
576.
Q. Why does the white European skin
blister and scorch when exposed to the hot
sun ?
A. Because white will not absorb hen^t; and,
therefore, the hot sun rests on the surface of
the skin, and scorches it.
577.
Q. Wliy has a negro black eyes ?
ABSORPTION.
150
A. Because the black color defends them
from the strong light of the tropical sun.
If a negro's eyes were not black, the sun
would scorch them.
578.
Q. Why is water (in hot weather) kept
cooler in a bright tin pot than in an earthen
one ?
A. Because bright metal will not absorb
heat from the hot air, like an earthen vessel;
in consequence of which, the water is kept
cooler.
Boiling water is also kept hot in bright metal better than m earthen
vessels.
579.
Q. Why does a saucepan, which has been
used, boil in a shorter time than a new one ?
A. Because the bottom and sides are
covered with soot ; and black soot rapidly ab-
sorbs the heat of the glowing coals.
580.
Q. Why should the lid of a saucepan be
clean and bright ?
A. Because it cannot absorb heat, as it
does not come in contact with the fire ; and
(being bright) it will not suiFer the heat to
escape by radiation.
581.
Q. In what state should a saucepan be, in
order that it may boil quickly ?
160
CHEMICAL ACTION.
A. All those parts which come in contact
with the firCy should be covered with soot, or
be black, in order to absorb heat ; but all
the rest of the saucepan should be as bright
as possible, to prevent the escape of heat hy
radiation.
582.
Q. Why should not the bottom and sides
of a kettle be cleaned and polished ?
A. Because they come in contact with the
fire, and (while they are covered with black
soot) absorb heat freely from the burning
coals.
583.
Q. Why should the top of a kettle be
clet n and well polished ?
A. Because polished metal ivill not ra-
diate heat ; and, therefore, (while the top of
the kettle is well polished) the heat is kept in,
and not suffered to escape by radiation.
584.
Q. Show the benefit of smoke in cooking ?
A. The carbon of the fuel (which flies
off in smoke) naturally blackens all culinary
vessels set upon the fire to boil, and thus
renders them fit for use.
** Culinary vessels " are vessels used in kitchens for cooking, as sauo/}
wans, boilers, kettles, etc.. (from the Laliw word " Cullna," akiteken,)
PERCUSSION.
161
585.
Q How does smoke make culinary vessels
(it for use ?
A. By absorbing heat. If it were not
ft>r the smoke (which gathers round a kettle
01 saucepan) heat would not he absorbed, and
the process of boiling would be greatly re-
tarded.
586.
Q. Why is boiling water kept hot in a
bright metal pot better than in an earthen
vessel ?
A. Because bright metal (being a had ra-
diator) will not throw off from its surface the
heat of the boiling water.
CHAP. IV.— MECHANICAL ACTION.
SECTION I. PERCUSSION.
587.
Q. How is heat j)roduced by mechanica)
action?
A. 1. — By Percussion. 2. — By Friction,
and 3. — 1^Y Condensation, or Compression .
588.
Q. ^Yhat is meant by percussion ?
A. The act of striking ; as when a black-
smith strikes a piece of iron on his anvil
Mrith his hammer.
11*
162
MECHANICAL ACTION*
589.
Q. Why does striking iron make it red hot'!
A. Because it condenses the particles of the
meta]^ and makes the latent heat sensible.
530.
Q. Does cold iron contain heat ?
A. Yes ; everything contains heat ; but,
when a thing feels cold, its heat is latent.
591.
Q. What is meant by latent heat ?
A. Heat not perceptible to our feelings.
When anything contains heat without feel-
ing the hotter for it, that heat is called ''la-
tent heat''
592.
Q. Does cold iron contain latent heat?
A. Yes ; and when a blacksmith com-
presses the particles of iron by his hammer,
he brings out latent heat ; and this makes
the iron red hot.
593.
Q. How used blacksmiths to light their
matches before the general use of lucifers ?
A. They used to lolace a soft iron nail
upon their anvil ; strike it tw^o or three
times with a hammer ; and the point be*
came snfficieiithj hot to light a brimstone m.a,fch
PERCUSSION.
163
594.
Q. How can a nail (beaten by a hammer)
ignite a brimstone match ?
A. The particles of the nail being com-
py^ssed by the hammer, can no longer con-
tain so mnch heat in a latent state^ as th^.y
did before ; some of it, therefore, becomes
sensible, and increases the temperature of
the iron.
595.
Q. Why does striking a flint against a
piece of steel produce a spark ?
A. Because it compresses those parts of
the flint and steel which strike together. In
consequence of which, some of their latent
heat is disturbed, and exhibits itself in a
spark.
596.
Q. How does this development of heat
produce a spark and set tinder on fire ?
A. A very small fragment (either of the
steel or flint) is knocked off red hot, and gets
fire to the tinder on which it falls.
597.
Q. Why is it needful to keej) blowing Iho
tinder with the breath ?
A. In order that the increased supply oi*
air may furnish the tinder with more oxygen
to assist combustion.
164
MECHANICAL ACTIOI^
598.
Q. Where does the oxygen of the air comi
from J wliich is blown to the lighted tinder r
A. From the air itself, which is composed
of two gases {nitrogen and oxygen) mixed to-
gether.
Every five gallons of common air contain nearly four gallons of nitro-
gon, and one of oxygen.
599.
Q. What is the use of oxygen gas to light-
ed tinder ?
A. It supports the combustion of the tinder.
Blowing lighted tinder carries oxygen to it
and quickens it, in the same way as a pair
of bellows quickens a dull fire.
600.
Q. Why do horses sometimes strike fire
with WiQiY feet?
A. Because when their iron shoes strike
against the flint stones of the road, very
small fragments (either of the shoe or stones)
are knocked o f red hot, and look like sparks.
601.
Q, What makes these fragments red hot ?
A The percussion condenses the part
gtruck ; in consequence of which, some of
its latent heat is rendered sensible, and ex-
hil)its Itself in these red hot fragnifBnts,
FIIICTION.
165
SECTION II. FRICTION.
602.
Q. What is meant hy friction ?
A The act of rubbing two things together ;
as the Indians rub two pieces of icood to-
gether to produce fire.
603
Q. How do the Indians produce fire hy
merely rubbing two pieces of dry wood to-
gether ?
A. They take a piece of dry Avood, sharp-
ened to a point, which they rub quickly
up and down a flat piece, till a groove is
made ; and the dust (collected in this
groove) catches fire.
60^.
Q. Why does the dust of the wood catch
fire by rubbing ?
A. Because latent heat is developed from
the wood by friction.
The best woods for this purpose are boxwood against mulberryy or laurel
against poplar or ivy
605.
Q. Do not carriage wheels sometimes catch
fire?
A. Yes; when the wheels are dry— or
fit too tightly — or revolve very rapidly.
606.
Q. Why do wheels catch fire in such
cases?
1C6
MECHANICAL ACTION,
A. Because the friction of the wheels
against the axle-tree disturbs their latent heal,
and produces ignition.
607.
Q. What is the use of greasing cart
wheels ?
A. Grease lessens the friction; and, be-
cause there is less friction, the latent heat
of the wheels is less disturbed.
608
Q. Why does rubbing our hands and faces
make them feel warm ?
A. 1st. — Because friction excites the la-
tent heat of our hands and faces, and makes
it sensible to our feeling : and
2nd. — The blood is made to circulate more
quickly ; in consequence of which, the quan-
tum of heat (left in its passage) is increased.
609.
Q. When a man has been almost drowned^
why is suspended animation restored by ruh-
bing ?
A. 1st. — Because friction excites the la^
tent heat of the half-inanimate body : ind
2nd. — It makes the blood circulate more
quickly y which increases the animal heat.
610.
Q. Why do two pieces of ice lubbed to-
gether m elt ?
FRICTION.
1G7
A. Ice contains 140"* of latent heat, and
(when two pieces are rubbed together) some
of this latent heat is made sensible^ and
melts the ice
611.
Q. Are not forests sometimes set on fire
by friction ?
A. Yes ; when two branches or trunks
of trees (blown about by the wind) rub vio^
lently against each other , their latent heat is
developed, and sets fire to the forests.
612.
Q. Why do carpenters' tools (such as
gimlets, saws, files, etc.,) become hot when
used ?
A. Because the friction of the tools
against the wood disturbs its latent heat,
and makes it sensible.
613.
Q. Give an illustration of this ?
A. When cannon is bored, the borers
become so intensely hot from friction, that
rtioy would blister the hands, if touched.
614.
Q. Why do these borers become so iu»
tensely hot ?
A. Because the friction of the borers
against the metal is so great, that it
free a large quantity of latent heat.
l08 MECHANICAL ACTlOxV.
SECTION 1/ I. CONDENSATION OR COMPRESSION.*
615.
Q. What is meant by compression ?
A. The act of bringing parts nearer to-
aether; as a sponge compressed hy hoiwg
squeezed in the hand.
616.
Q. Cannot heat be evolved from common
air merely by compression ?
A. Yes ; if a piece of German tinder be
placed at the bottom of a glass tube, and the
air in the tube compressed by a piston, the
tinder will catch fire.
In a common syringe or squirt, tho handle part (which contains tht
sucker, and is forced up and down) is called " the Piston."
617.
Q. ^¥h.y will the tinder catch fire ?
A. Because the air is compressed ; and its
latent heat being squeezed out, sets fire to the
tinder at the bottom of the tube.
618.
Q. When an air -gun is discharged in the
dark, why is it accompanied with a slight
flash ?
A. Because the air is very rapidly con-
* N. B. The reduction of matter into a smaller compass by an external
or mechanical force is called compression.
The reduction of matter into a smaller compass by some internnl ctctiom
\JBiS by the escape of caloric) is called condensation.
CONDENSATION OR COMPRESSION. 169
densed, and its latent heat developed in a
fl>ash of light,
N B. If a glass lens be fixed in the copper ball, (where the air of tha
gun is condensed,) a flash of light may be distinctly discerned at the stroke
01 \he piston.
619.
Q. Why do detonating salt and joowdor
explode on being rubbed or struck ?
A. Because the mechanical action of
nibbing or striking, produces sufficient heat
to ignite the explosive materials of which
they are composed.
620.
Q. Why does the hole made by a shot or
cannon-ball in a wall or timber, look as if
it were burnt ?
A. Because the shot or cannon balls were
so heated by the discharge, as actually to
scorch the material into which they pene-
trated.
62 1.
Q. Why are shot and cannon-balls heated
by being discharged from a gun or cannon ?
A. Because the air is so rapidly con-
densed, when the discharge is made, that
sufficient latent heat is developed to make
the shot or balls hot.
15
PART IL
NON-METALLIC ELEMENTS.
622.
Q. "What is meant by no7i-mefallic eh
meats ?
A. Those elementary bodies which do
not belong to the class of metals.
Elementary bodies are those which have never been decomposed ; that
is, do not appear to be composed of any compounds, bat are pure sub-
stances in themselves. At present there are reckoned fifteen non-metallio
elementary substances, and forty which belong to the class of metals.
CHAP. L— OXYGEN AND OXIDES.
623.
Q. What is the difference between oxi/'
gen. and an oxide ?
A. Oxygen is a gas, and an oxide is a com-
pound formed by the union of oxygen with
ether bodies.
SECTION I. OXYGEN.
624.
Q. What is oxijgen ?
A. A gaseous hody: which is found largoljf
170
OXYGEN.
171
difiused throughout all nature, being an im-
portant element of air and water, rocks^
mrthsj minerals y etc.
Oxygsn gas is much more troublesome to make than hydrogen. Tha
eheap'sst plan is to put a few ounces of manganese (called black oxide of
manganese,) into an iron bottle, furnished with a bent tube; set the bottle
OB a fire till it becomes red hot, and put the end of the tube into a pan of
Water. In a few minutes, bubbles will rise through the water ; these bub-
^les are oxygen gas.
The bubbles may be collected thus : — Fill a common bottle with water ;
Jsi'ld it inverted over the bubbles which rise through the pan, but be sure
the mouth of the bottle be held in the water. As the bubbles rise into the
bottle the water will run out ; and when all the water has run out, the
bottle will be full of gas. Cork the bottle while the mouth remains under
loater ; set the bottle on its base: cover the cork with lard or wax, and
the gas will keep till it be wantea.
N. B. The quickest way of making oxygen gas, is to rub together in a
mortar half an ounce of oxide of copper, and half an ounce of chlorate of
potassa. Put the mixture into a common oil flask, furnished with a cork
which has a bent tube thrust through i"; Heat the bottom of the flask
over a candle or lamp : and when the mixture is red hot, oxygen gas will
be given off. Note. — the tube must be immersed in a pan of water and
the gas collected as before.
(Chloride of potassa may be bought at any chemist's, and oxide of cop-
per may be procured by heating a sheet of copper red hot, and when cool,
striking it with a hammer ; the scales that peel off are oxide of copper.)
Experiment. — Put a piece of red hot charcoal (fixed to a bit of wire,)
into your bottie of oxygen gas; and it will throw oat most dazzling
bparks of light
Blow a candle out ; and while the wick is still red, hold the candle (by a
piece of wire,) in the bottle of oxygen gas; the wick will instantly ignite,
and burn brilliantly.
(Burning sulphur emits a blue flame, when immersed in oxygen gas.)
625.
Q. "lYlien, and by whom, was oxygen dis^
covered ?
A. It was discovered in 1774, by Scheele,
in Sweden, and Dr. Priestly, in England,
independent of each other. They dfjscribed
it under different names.
626.
Q. Who gave it the name of oxygen ; and
what is the signification of the word ?
172 OXYGEN AND OXIDES.
A. Lavoisier gave it the name, which is
derived from two Greek words o^vg (oxus'
an acid, and yevvaco (gennao) I produce.
This name was given to it, because it was then thoug:ht to be tbe soU
acidifying principle. Modern discoveries have rectified this error, by
proving me existence of acids in the composition of which there if nt
oxygen.
627.
Q. Is oxygen ever found in a liquid or solid
Btate?
A. No : when pure, it is only known in
the gaseous state ; all eflforts to reduce it to
a liquid or solid condition by cold or pres-
sure, have completely failed.
628.
Q, Has oxygen any taste or smell ?
A. It is when pure, colorless, tasteless, and
moderous,
629.
Q. Of what use is oxygen in the atmosphere?
A. It sustains animal life, and supports
combustion
630.
Q. What peculiar property does oxygen
possess with regard to light ?
A. It refracts light less than any other
known body.
631.
Q. Why do we feel braced and light-hearted
on a fine spring or frosty moniing ?
OXYGEN.
173
A, 1st.— Because there is 7nore oxygen in
the air on a fine frosty morning, than there
is on a wet day ; and
2nd. — -A brisk and frosty air has a ten-
dency to brace the nervous system.
632.
Q. Why do dogs and cats (confined to a
room) feel lazy and droiozyy at the approach
of rain ?
A. 1st. — Because the air does not con-
tain its full proportion of oxygen ; and
2nd. — The damp depresses their nervous
system, and makes them drowsy,
633.
Q. When sheep lie under a hedge, and
seem unwilling to go to pasture, rain is at
hand ; Explain the reason of this ?
A. 1st. — As the air does not contain its
full proportion of oxygen, they feel uneasy ;
and
2nd. — As the damp air relaxes their ner-
vous system, they* feel listless and drowsy.
634.
Q. Wiiy do horses neigh, cattle low, sheep
bleat, and asses bray, at the approach of
rain?
A. 1st. — As the air does not contain its
15^
174
OXYGEN AND OXIDES.
full proportion of oxygen, they feel a diffi-
culty in breathing ; and
2nd. — As damp relaxes their nerves , they
feel languid and uneasy.
635.
Q. Mention some other animals ^ which in-
dicate the approach of rain in a similar way?
A. When pigs squeak, as if in great pain
~ -frogs croak with a loud, hoarse noise —
owls screech — woodpeckers cry — peacocks
scream — guinea-fowls squall — or ducks and
geese are unusually noisy, rain is close at
hand.
636.
Q. Why do candles and fires burn with a
bluer flame in wet weather ?
A. Because the air contains less oxygen in
wet weather, and, therefore, the heat of the
fire is less intense. The flame is blue, be-
cause the fuel is not thoroughly consumed.
637.
Q. What is meant, when it is said, that
the oxygen of the air ''supports combustion?^'
A. It means this : It is the oxygen of the
air which makes fuel burn.
638.
Q. How does the oxygen of the air make
fuel burn ?
OXIDES.
175
A. The fuel is decomposed (by heat) into
hydrogen and carbon; and these elements
combining with the oxygen of the air pro*
duce combustion.
639.
Q. What are the uses of the oxygen of
the air ?
A. To support combustion and sustain life.
640.
Q. What is meant, when it is said, that
Dxygen sustains life?'^
A. It means this : If a person could not
inhale oxygen, he would die.
641.
Q. What good does this inspiration of
oxygen do ?
A. 1st. — It gives vitality to the blood :
and
2nd. — It is the cause of animal heat.
SECTION II. OXIDES
642.
Q. What are oxides ?
A. The compounds formed by the union
of oxygen with other bodies, bear the gene-
ral name of oxides.
643.
Q. AVhat is rust ?
176
OXYGEN AND OXIDES.
A. The oxidation of iron in moist air.
" OxidatioTij^^ impregnation with oxygen.
644.
Q. Why does iron rust ?
A Because water is decomposed when it
comes in contact with the surface of iron ;
and the oxygen of the water combining with
iron, produces an oxide, which is generally
called rust.
Water is composed of Oxygen and Hydrogen, in the following propoi-
Hons : 8 lbs. of Oxygen, and 1 lb. of Hydrogen=9 lbs. of waier.
645.
Q. Why does air rust iron ?
, A. Because the oxygen of the air combines
with the surface of the metal, and produces
oxide of iron ; which is generally called
" rust.''
An oxide of iron, copper, etc., is oxygen in combination with iron cop«
per, etc.
646.
Q. Does iron rust in dry air ?
A. No ; iron undergoes no change in dry
air.
647.
Q. Why does hot iron scale and peel off,
when struck with a hammer ?
A. Because the oxygen of the air very
readily unites with the surface of the hot
iron, and forms a metallic oxide (or rust,)
which scales off when struck with a hnm
mer.
OXIDES.
177
648.
Q. Why do stoves and fire-irons become
rusty in rooms, which are not occupied ?
A. Because the air is damp ; and moist
ftir oxidizes iron and steel.
Oxidizes, that is, rusts
649.
Q. In what part of the year is it most
difficult to keep stoves and fire-irons bright ?
A. In autumn and winter,
650.
Q. Why is it more difficult to keep stoves
and fire-irons bright in autumn wadi winter
than in spring and summer ?
A. Because the capacity of the air for
holding water is constantly on the decrease,
after the summer is over; in conse-
quence of which, vapor is deposited on
everything with which the air comes in
contact.
651.
Q. Why does greasing iron prevent its
becoming rusty ?
A. Because grease prevents the humidity
of air from coming in contact with the sur-
face of the iron.
652.
Q. Why does painting iron prevent it froin
rusting ?
178
OXYGEN AND OXIDES.
A. Because paint prevents the moist air
from coming in contact with the iron.
653.
Q. Why will bright iron lose its polish hy
l)eing put into a fire ?
A. Because the oxygen of the air very
r-eaclily unites with the surface of hot iron,
and forms a metallic oxide; which displays
itself, in this case, by a dull leaden color,
instead of a red rust.
654.
Q. Why do not stoves rust so frequently
as pokers and tongs ^
A. Because stoves are generally cohered
with plumbago, or black lead.
655.
Q. T^Tiat is plumbago, or black lead ?
A. A mixture of charcoal and iron.
Plumbago (strictly speaking) is a chemical union of carbon and iron, io
the following proportions : — 91 parts carbon, and 9 iron But the EIACH
LEAD sold in shops is a nnixiure of charcoal and iron filings.
N. B. A most excellent varnish to prevent rust is made of one pint of fa(
oil varnish, mixed wMth five pints of highly rectified spirits of turpentine,
rubbed on tlie iron or steel with a piece of sponge. This varnish may be
upplied to bright stoves, and even mathematical instruments, wiihoul ii>
jurnig their delicate polish.
656.
Q. Why does ornamental steel (of a pur-
ple or lilac color) rust more readily than
polished white steel ?
A. Because the lilac tinge is produced by
'partial oxidation ; and the process which
OXIDES.
179
fuims rusts, has, therefore, already com-
menced,
657.
Q, How can lilac sImI be kept free from
rust ?
A. By keepmg it in a very dry place.
658.
Q. If dry air contains oxygen^ why doea
it not rust iroriy as well as moist air ?
A. Because moisture is always needed,
in order to bring into action the affinity of
oxygen for steel.
659.
Q. When a black subsoil is dug or ploughed
up, it turns of a reddish brown color after
a short time ; Why is this ?
A. Because the soil contained a certain
compound of iron, called the protoxide/'
which is black. This protoxide of iron,
absorbing more oxygen from the moist air,
IS converted into another compound, called
the *'per-oxide of iron,'' which is of a red-
dish rusty color.
Tnere are Iwo oxides of iron, the one containing more oxygen than th«
other The protoxide which contains the least oxygen is black ; the per-
oxide.^ which contains the most oxygen is red,
660.
Q. Do any other metals (besides iron)
combine rapidly with oxygen ?
180
OXYGEN AND OXIDES.
A. Yes; copper, lead, mercury, and even
isilver to some extent.
661.
Q. Why does copper tarnish ?
A. The tarnish of copper is caused by its
oxidation; that is, the oxygen of the air
combines with the surface of the copper,
and, (instead of rusting it) covers it with a
dark tarnish.
662.
Q. Why does lead become a darker hue,
by being exposed to the air ?
A. Because the vapor of the air com-
bines with the lead, and oxidizes its surface ;
but instead of becoming rusty, the surface
assumes a darker hue.
663.
Q. Why does lead lose its brightness, and
become dull, by being exposed to the air ?
A. The dullness of the lead is caused by
the presence of a carbonate of the oxide.
When the oxide is formed, it attracts car-
honic acid from the air, and (combining with
it) produces a carbonate, which gives the
dull tint to old lead.
664.
Q. Why is it difficult to keep silver bright?
A. Because the vapor of the air oxidizefl
its surface, and farnishrs it.
OXIDES.
181
665.
Q. Why does salt turn silver black?
A. Because it precipitates an oxide of
silver on the surface of the spoon, the color
of which is black.
Marking ink " is made of soda and the nitrate of silver ; the bla3k
tfi&rk being Que to the oxide, precipitated on the cloth.
666.
Q How can the black stain of silver^
made by salt be removed ?
A. By washing the silver in hartshorn
or common ammonia; by which means,
the oxide will be re-dissolved, and the
blackness entirely disappear.
667.
Q. Why do silver tea-pots and spoons tar-
nish more quickly than bullion ?
A. Because alloy of some baser metal is
used, to make them more hard and lasting ;
and this alloy oxidizes more quickly than
silver itself.
668.
Q. Why does German silver turn a dingy
yellow in a few hours ?
A. Because German silver has a great
affinity for oxygen ; and shows its oxida-
tion by a sickly yellow tarnish^ instead of
rust.
16
1S2 OXYGEN AND OXIDES.
669.
Q. If quicksilver (or mercury) will tar
nish like copper and lead — why does it pre-
serve its hrilliancy in barometers and thermo-
meters ?
A. Because the air is excluded ; and no
moisture can come in contact with it, to
oxidize (or tarnish) it.
670.
Q. Is gold affected by the atmosphere ?
A. Not readily; gold will never com-
bine with oxygen of itself, (that is, with-
out aid.)
671.
Q. Which of the metals is capable of re
sisting oxidation altogether ?
A. Plat'inum ; in consequence of which,
the graduated arcs of delicate " instru
ments-for-observation," are made of plati-
num instead of any other metal.
672.
Q Why is platinum used for the gradu»
ated arcs of delicate mathematical instru-
ments, instead of any other metal ?
A. Because it will never oxidize ; but
retains its bright surface in all weathers, free
from both rust and tarnish.
OXIDES. 183
673.
Q For what other scientific purpose is
plat mum now used?
A. For crucibles in which acids are em-
ploj'ed : and for galvanic batteries.
674.
Q. Why are crucibles (in which acids are
employed) made of platinum ?
A. Because the acid would act upon other
metals, or upon glass ; and prevent the ex-
perimenter's success.
675.
Q. Before platinum was discovered,
which of the metals was employed for the
same purpose ?
A. Gold.
Plat'innm (a white metal,) so called from " plata," the Spanish word
fnT silver. It was introduced from South America into England, by Mr.
Wood, ^A. D. 1749.)
676.
Q. Which of the metals have the greatest
affinity for oxygen ?
A. Those called potas'sium and so'dium.
Potas'sium and so''dium derive their names from potash ai.d soda.—
Potas^sa is the oxide of potas''ijium ; and soda is the oxide of so''diuni.
677.
Q. How is the affinity of potas'sium and
so'dium for oxygen shown ?
A. They decompose loater as soon as they
are brought into contact with it.
184 HYDROGEN AND WATER.
678.
Q. What effect has potas'sium on water ?
A. It catches fire the moment it is thrown
into water, and bm-ns with a vivid flame
which is still further increased hy the 00111-
bustion of hydrogen^ separated from tlie
water.
N. B. Water is composed of oxygen and hydrogen ; and potas siuai
separates the two gases.
679.
Q. What effect has so'dium on vmter ?
A. It does not take fire as potas^sium
does ; but undergoes very rapid oxidation.
CHAP. II.— HYDROGEN AND WATER.
680.
Q. What is the distinction between hy-
drogen and water ?
A. Hydrogen is an inflammable ga^; and
water is composed of hydrogen and oxygen,
SECTION I. HYDROGEN.
681.
Q. What is hydrogen ?
A. An inflammable gas. The gas used
in our streets is hydrogen driven out of zocl
HYDROGEN. 185
hy heat. Hydrogen is the principal ingre-
dient of water.
Coal ^as (more properly speaking) is carburetted hydrogen; that is car-
bon and hydrogen.
Hydrogen derives its name from two Greek words v6odp udcr (water,>
I3>fi Xnt aa) gennao (I produce.)
682
Q When was hydrogen gas discovered ?
A. After the middle of the eighteenth
century, and was termed inflammable air.
683.
Q Has hydrogen any taste or color ?
A. It has, when pure, neither taste, color
nor smell. When it has any odor, it arises
from impurities.
684.
Q. Does hydrogen support life ?
A. No ; it destroys it, rather by excluding
oxygen than by its own injurious effects.
685.
Q. Does hydrogen gas like oxygen sup-
port combustion ?
I A. No ; it is highly combustible, but does
not support combustion ; uniting with oxy-
gen it forms water.
686.
Q. What are the peculiar characteristics
of hydrogen gas ?
A. Lst. — It is the lightest of all known
substances;
16*
186
HYDROGEN AND WATER.
2nd. — It will burn immediately on being
ignited ; and
3rd. — Alighted candle (immersed in this
gas) will be. instantly extinguished.*
687.
Q. For what uses are hydrogen gas em-
ployed ?
A 1st. — Owing to its levity it is used to
inflate balloons.
2nd. — Burned with oxygen, it constitutes
the hydrogen blowpipe ; and
3rd.- — It is a powerful chemical agent.
Chemical agent^^^ a substance employed to effect chemical changes.
688.
Q. What is a blow-ipiipe ?
A. A tube, usually bent near the end,
terminated with a finely pointed nozzle, for
blowing through the flame of a lamp or
gas-jet; and producing thereby a small
conical flame possessing very intense heat.
689.
Q. Describe the hydrogen blowpipe ? i
A. A mixture of oxygen and hydrogen,
* Hydrogen gas may be made thus : — Put Fome pieces of zinc or iron
filings into a glass ; pour over them a little sulphuric acid (vitriol,) diluted
with twice the quantity of water ; then cover the glass over for a few
minutes, and hydrogen gas will be given off.
Experiments. — If a flame be put into the glass, an explosion will be
ttiade.
If the experiment be tried in a phial, which has a piece of tobacco p-pa
.'un through the cork, and a light held a few moment* to the top of the
pipe, a flame will be made.
If a ialloon be held over the phial (so that the gas can inflate it,> »hf
balloon will ascend in a very few minuses.
WATER.
187
when Ignited^ produces an intense Keat, and
constitutes the hydrogen blowpipe.
690.
Q. Who invented the hydrogen blowpipe ?
A Dr. Hare, of Philadelphia.
691.
Q. Can you describe the Drummond light!
A. It is the ignited flame of a mixture of
dxygen and hydrogen, projected against lime ;
the lime becomes intensely luminous, and
forms the well known Drummond light.
SECTION II. ^WATER.
\ 692.
Q. What is water ?
A. Water is a fluid, composed of oxygen
and hydrogen, in the proportion of e^'glit
parts of oxygen to one part^of hydrogen^^^
Q. Why is water fluid?
A. Because its particles are kept separate
by latent heat ; when a certain quantity of
this latent heat is driven out water becomes
solid, and is called ice.
By increasing its latent heat, the particles of water are again subd ivule<|
into invisible steam.
694.
Q. Why is pump-water called ^'hard wa^
188 IIYDIIOGEN AND WATER.
A. Because it is laden with foreign mat-
ters, and will not readily dissolve substances
immersed in it.
695.
Q What makes pump-water hard ?
A. When it filters through the earthy
it becomes impregnated with sulphate of lime ^
and many other impurities from the earths
mid minerals with which it comes in contact,
696.
Q. What is the cause of mineral springs ?
A. When water trickles through the
ground, it dissolves some of the substances
with which it comes in contact ; if these
substances are metallic, the water will par-
take of their mineral character.
Some water is imbued with Ume ; some with salt, etc., etc.
697.
Q. Why is it difficult to wash our hands
clean with hard water ?
A. Because the soda of the soap combines
with the sulphuric acid of the hard water — »
and the oil of the soap with the lime — and
floats in flakes on the top of the water,
N B Sulphate of lime consists of sulphuric acid and lime.
698.
Q. Why is it difficult to wash in salt
water ?
WATER.
189
A. Because it contains muriatic acid; and
(lie soda of soap combines with the muriatic
acid of the salt watery and produces a cloudi-
ness.
699.
Q. What is the cause of petrifactiom ?
A. While water rolls under ground, its
impurities are held in solution by the pre-
sence of carbonic acid; but when the stieam
reaches the open air, its carbonic acid
escapes, and these impurities are precipita-
ted on various substances lying in the course
of the stream.
These impurities are especially carbonate of lime and iron.
700.
Q. Why does water clean dirty linen ?
A. Because it dissolves the stains, as it
would dissolve salt.
701.
Q. Why does soap greatly increase the
cleansing power of water ?
A. Because many stains are of a greasy
nature ; and soap has the power of uniting
tvith greasy matters, and rendering them
soluble in water.
702.
Q. Why is rain-wafer soft ?
A. Because it is not impregnated with
?arths and minerals.
190 HYDROGEN AND WATER.
703.
Q. Why is it more easy to wash with soft
water, than with hard ?
A. Because soft water unites freely with
Boap, and dissolves it; instead of decomposing
it, hard water does.
704.
Q. Why do wood ashes make hard water
soft?
A. 1st. — Because the carbonic acid of wood
ashes combines with the sulphate of lime in the
hard water, and converts it into chalk ; and
2nd. — Wood ashes convert some of the
sohible salts of water into insoluble, and
throw them down as a sediment ; in conse-
quence of which, the water remains more
pure.
705.
Q. Why has rain-water such an unpleasant
smell, when it is collected in a rain-water
tub or tank ?
A. Because it is impregnated with fig-
composed organic matters, washed from roofs,
trees, or the casks in which it is collected.
706.
Q. Why does melted sugar or salt give a
flavor to water ?
A. Because the sugar or salt (being dis-
WATER.
191
united into very minute particles) floats
about the water, and mixes with every part.
707.
Q. A¥hy does hot water melt sugar and
salt quicker than cold water ?
A. Because the heat (entering the pores
of the sugar or salt) opens a passage for the
water.
708.
Q. Why is sea-water brackish ?
A. 1st. — Because the sea contains mines
of salt at the bottom of its bed ;
2nd. — It is impregnated Avith bituminous
matter, which is brackish ; and
3rd. — It contains many putrid substances
of a brackish nature.
709.
Q. lyiiy is not rain-water salt, although
most of it is evaporated from the sea ?
A. Because salt will not evaporate ; and,
therefore, when sea-water is turned into
vapor, its salt is left behind.
710.
Q. Wliy does running water oscillate and
whirl in its current ?
A. 1st. — Because it impinges against its
hanks, and is perpetually diverted from its
forward motion ; and
102
NITIIOGEN AND AIR.
2n(l. Ijecause the centre of a river llowy
faster tlian its sides.
711.
(}. Why do the sides of a river How more
tardily than its centre ?
A. Because they ruh against the hanks,
ttnd are delayed in their current by this
friction .
CHAP III.— NITROGEN AND AIR.
SECTION I. NITROGEN.
712.
Q. What is nitrogen ?
A. An invisible gas which abounds in
animal and vegetable substances ; The fol-
lowing are its peculiar characteristics :
1st. — It will not burn ;
2nd. — An animal cannot live in it ;
3rd. — It is the principal ingredient in
common air.*
Nearly four gallons out of every five being nitrogen gas.
Nitrogen, that is, generator of nitre ; also, called azou, from the Greek
words a (a) privative, or to deprive of, and Wl (zoe) life.
713.
Q. When and by whom was nitrogen dis-
covered?
* Nitrogen gas may easily be obtained thus: — Put a piece of burning
phosphorus on a little stand in a plate of water ; and cover a bell glass over
It. (Be sure the edge of the glass stands m f^e trater.) In a few minutes
the oxygen of the air will be taken up by the burning phosphorus ; and
nitrogen alone will be left in the bell gUss.
N. B. The white fume which will arise and be absorbed by the water in
this experiment is phosphoric acid ; that is, phosphorus cnmhinei with
ixygen of the air.
AIR.
193
A. In the year 1772, by Rutherford.
714.
Q. Is nitrogen capable of sustaining com-
hmtion ?
A. No; nitrogen, like hydrogen, is tn-
capable of sustaining combustion or animal
existence, although it has no positive poison-
ous properties.
715.
Q. Has nitrogen any color 1
A. No ; nitrogen has neither color, taste,
nor smell.
SECTION II. AIR.
716.
Q. What are the elements of atmospheric
air ?
A. Oxygen and nitrogen mixed together
in the following proportions ; four gallons
of nitrogen and one of oxygen, will make
five gallons of common air.
717.
Q. Is not the air we breathe almost
wholly composed of nitrogen ?
A. It is ; about four- fifths of the air is
nitrogen and the other one-fifth is oxygen.
But nitrogen is a gas which cannot support animal life— whereas, tho
nir or atmosphere which we breaihe is a thin transparent Jluid which eur-
'oiinc'C' the earth, and xup-portf nnimal life by respiration
^7
194
NITROGEN AND AIR.
718.
Q. Why is there so much nitrogen in th^'.
air?
A. In order to dilute the oxygen. If the
oxygen were not thus diluted, fires would
burn out too quickly, and life would be too
rapidly exhausted.
719.
Q. Is air material^ that is, is it composed
of matter ?
A. It is ; we do not see the air in the
room, because it is transparent ; but we feel
it when we run or fan ourselves, and we hear
through the medium of the air ; therefore,
it is material, or composed of matter ; for
matter is that which is perceived by our
senses.
720
Q. Is air invisible ?
A. No ; for although we cannot perceive
it immediately around us, when we look up
into the firmament illuminated by the sun,
the air appears of a beautiful azure. This
is the mass of the atmosphere. Distant
mountains appear of a blue color, owing to
our viewing them through the atmosphere.
721.
Q. Why can we not see the air imine*
CARBON.
195
diately around us of the samo beautiful
azure ?
A. So small a portion of air reflects little
or no color, while a mass would be capable
of reflecting a beautiful tint ; so it is with
B. small quantity of sea-water dipped up in
a glass ; it would appear perfectly colorless,
yet the deepest part of the ocean appears
of a dark green, approaching to a black.
CHAR IV.— CARBON.
722
Q. What is carbon ?
A. A solid substance generally of a dark
or black color, well known under the forms
of charcoal, lamp-black, coke, etc.
723.
Q. Carbon occurs in nature crystallized in
two forms ; What are they ?
A. The Diamond and Graphite.
Graphite., known by the names of plumbago, or black>lead, is used fOP
making pencils for drawing and writing.
724.
Q. What is a crystal?
A. The geometrical form possessed by a
vast number of mineral and saline substan-
ces, whose particles combine with one ano-
ther by the attraction of cohesion, accord-
ing to certain laAVS, the investigation of
196
CARBON.
which belong more properly to the science
of crystallography.
725.
Q, What peculiar properties does the din
mond possess ?
A. It possesses a degree of hardnes^\
superior to that of any other mineral ; it
scratches all other bodies but is scratched
by none.
It acquires positive electricity by friction,
but does not retain it for more than half an
hour.
It possesses either single or double re-
fraction according to its crystalline form.
When exposed to the sun's rays for a
certain time, or to the blue rays of the
prismatic spectrum, it becomes phospho-
resc( nt.
(For a description of graphite^ see under metals.)
726.
Q. Can you give an example of carbon
in its uncrystdlized state ?
A. Lamp-black, the soot produced by the
imperfect combustion of oil or resin, is pure
carbon in its uncrystallized or amorphous
Btate.
" Amorphous " — shapeleBs, without form.
727.
Q. What is charcoal ?
CARBON.
197
A. Wood which has been exposed to a
red heat till it has been deprived of all its
gases and volatile parts.
728.
Q. Why does charcoal remove the taint of
meat ?
A. Because it absorbs all putrescent effluvia^
whether they arise from animal or vegeta-
l le matter.
729.
Q. What other kinds of charcoal are there?
A. Cokey the charcoal of pit-coal, and
Anthracite y which is a mineral charcoal.
Anthracite differs from pit-coal, in containing no bitumen, and, therd-
fore, burning without flame or smoke.
730.
Q. Why is a charcoal fire hotter than a
wood fire ?
A. Because charcoal is very pure carbon;
and, as it is the carbon of fuel which pro-
duces the glowing heat of combustion,
therefore, the purer the carbon, the more
intense will the heat of the fire be.
731.
Q. Why does coal make such excellent
fuel?
? A. Because it contains a large amount of
carbon and hydrogen gas, in a very compact
Rnd convenient form.
17*
198 CARBON.
732.
Q. Why will not stones do for fuel as well
as coal ?
A. Because they contain no hydrogen and
little or no carbon.
733.
Q. Why will not iron-cinders bum ?
A . Because they contain impurities, which
are not so ready to combine with oxygen,
as carbon and hydrogen are.
734.
Q. Of what are oil, tallow, and wax, com-
posed ?
A. Principally of carbon and hydrogen
gas. The solid part is carbon, the volatile
part is hydrogen gas.
735.
Q. Why arc timbers which are to be ex
posed to damp charred ?
A. Because charcoal undergoes no change
by exposure to air and water; in conse-
quence of which, timber will resist weather
much longer after it has been charred.
736.
Q. Why should sick persons eat dry foasfj -
rather than bread and butter ?
A. Because the charcoal surface of the
CARBON.
199
toast helps to absorb the acids and impuri-
ties of a sick stomach.
There are other reasons which belong lo the science of med.cine.
737.
Q. Why should toast and water intendal
for the sick be made of burnt bread ?
A. Because the charcoal surface of burnt
bread prevents the water from being af-
fected by the impurities of the sick room.
73S,
Q. Why does a piece of burnt bi^ead make
impure water fit to drink ?
A. Because the surface of the bread
(which has been reduced to charcoal by be-
ing burnt,) absorbs the impurities of the loa,-
ter, and makes it palatable.
739,
Q. Why are water and wine casks charred
inside ?
A. Because charring the inside of a cask
reduces it to a kind of charcoal ; and char-
coal (by absorbing animal and vegetable
impurities,) keeps the liquor sweet and
good.
740.
Q. Why is water purified by being filtered
through charcoal ?
A, Because charcoal absorbs the impuri*
200
CARBON.
ties of the water, and removes all disagree-
able tastes and smells, whether they arise
from animal or vegetable matter.
SECTION I. CARBONIC ACID.
741.
Q. What is carbonic acid gas?
A. A gas formed by the union of carbon
and oxygen ; it used to be called fixed air.
3 lbs. of carbon and 8 lbs. of oxygen will form 11 lbs. of carbonic acid.
742.
Q. What gas is generated by a lighted
candle or lamp ?
A. Carbonic acid gas, — formed by the
union of the carbon of the oil or tallow with
the oxygen of the air.
743.
Q. Under what circumstances does carbon
most readily unite with oxygen ?
A. 1st. — When its temperature is raised :
Thus if carbon be red hot, oxygen will most
readily unite with it : and
2nd. — ^When it forms part of the fluid
blood.
744.
Q. Why do oxygen and carbon so rea-
dily unite in the blood ?
A Because the atoms of carbon are so
CARBONIC ACm.
201
looseh/ attracted by the other materials of the
blood, that they unite very readily with the
oxygen of the air inhaled,
745.
Q Is carbonic acid whoksome
A. No ; it is fatal to animal life : and
(whenever it is inhaled) acts like a narcotic
poison — producing drowsiness, v/hich, some-
times ends in death.
746
Q. How can any one know, if a place be
infested with carbonic acid gas ?
A. If a pit or well contain carbonic acid,
a candle (let down into it) will be instantly
extinguished. The rule, therefore, is this — •
where a candle will burn, a man can live ; but
what will extinguish a candle, will also destroy
life.
Q. Why does a miner lower a candle into
a mine, before he descends ?
A. Because the candle will be extinguished
if the mine contains carbonic acid gas : but
if the candle is not extinguished, the mine is
mfe^ and the man may fearlessly descend.
748
Q. Why does a crowded room produce
head'-ache ?
202
CARBON.
A. Because we breathe air vitiated hy
the crowd.
749.
Q. Why is the air of a room vitiated by
9 rowd?
A Because it is deprived of its due pro-
portijn of oxygen and laden with carbonic
ncid.
750.
Q. How is the air of a room aflected
thus by a crowd ?
A. The elements of the air inhaled are
separated in the lungs : — the oxygen is con-
verted in the blood into carbonic acid ; and
the carbonic acid (together with the nitro-
gen) is thrown back again by the breath
into the room.
751
Q. Is all the nitrogen rejected by tho
lungs ?
A. Yes ; all the nitrogen of the air is
always expired.
752,
Q. Why is a crowded room unwholesome 1
A. Because the oxygen of the air is oh-
sorbed by the lungs ; and carbonic acid gas
(which is a noxious poison) is substituted
for it.
CARBONIC ACID.
203
753.
Q. Mention the historical circumstances,
BO well known in connection with the
Black Hole of Calcutta:'
A. In the reign of Greorge II., the Raja
(or Prince) of Bengal,* inarched suddenly
to Calcutta, to drive the English from the
country; as the attack was unexjDected, the
English were obliged to submit, and one
hundred and forty-six persons were taken
prisoners.
754.
Q. What became of these prisoners ?
A. They were driven into a place about
eighteen feet square, and fifteen or sixteen
feet in height, with only two small grated
windows. One hundred and tw^enty- three
of the prisoners died in one night; and (of
the twenty-three who survived) the larger
portion died of putrid fevers, after they
were liberated.
755.
Q. Why were they suffocated in a few
hours, from confinement in .this close, hot
imso7i'hole ?
A. Because the oxygen of the air ^vas
soon consumed by so many lungs, and its
* The Sur Raja, at Dowlat ; a young: mun of violent passions, who Karf
but just sueceeded to the throne A. P. 1758.
204
place supplied by carbonic acid, exhaled bj
the hot breath.
756
Q. Why did the captives in the black koh
die sleeping?
A. 1st. — ^Because the absence of oxygen
quickly affects the vital functions, depresses
the nervous energies, and produces a lassi-
tude which ends in death ; and
2nd. — Carbonic acid gas (being a narcotic
poison) produces drowsiness and death, in
those who inhale it.
757
Q. Why are the jungles of Java and Hin-
dostan so fatal to life ?
A. Because vast quantities of carbonic acid
are thrown off by decaying vegetables in
these jungles; and (as the wind cannot
penetrate the thick brushwood to blow the
pernicious gas away) it settles there, and de-
stroys animal life.-
758.
Q. Why do persons in a crowded church
feel drowsy?
A. 1st. — Because the crowded congrega-
tion inhale a large portion of the oxygen of
the air, which alone can sustain vit^ality
and healthy action : and
CARBONIC ACID.
205
2n(i. — The air of the church is impreg-
nated with carbonic acid gas, which (being
a strong narcotic) produces drowsiness in
those who inhale it.
759.
Q. Why do persons who are much in the
open ail enjoy the best health ?
A , Because the air they inhale is much
more pure.
760.
Q. Why is country air more pure than the
air in cities ?
A. 1st. — Because there are fewer inhabi-
tants to vitiate the air :
2nd. — There are more trees to restore
the equilibrium of the vitiated air : and
3rd. — ^The free circulation of air keeps
it pure and wholesome : (in the same way
as running streams are pure and whole-
some, while stagnant waters are the con-
trary.)
761.
Q. Why does the scantiness of a country
population render the country air more pure?
k. Because the fewer the inhabitant;^ the
less carbonic acid will be exhaled ; and thus
country people inhale pure oxy^m, inste.'uj
18
20G
CARBON.
of air impregnated with the narcotic poison,
called carbonic acid gas.
762.
Q. Why do trees and flowers help to make
country air wholesome ?
A. 1st. — Because trees and flowers ab-
sorb the carbonic acid, generated by the lungs
of animals, putrid substances, and other ob-
noxious exhalations : and
2nd. — Trees and flowers restore to the
air the oxygen, which man and other ani-
mals inhale.
763.
Q. Why is the air of cities less whole-
some, than country air ?
A. 1st. — Because there are more inhabi-
tants to vitiate the air :
2nd. — The sewers, drains, bins, and filth
of a city, very greatly vitiate the air :
3rd. — The streets and alleys prevent a
free circulation : and
4th. — There are fewer trees to absorb
the excess of carbonic acid gas and restore
the equilibrium.
764.
Q. Why are persons, who live in close
rooms and crowded cities, generally sickly ?
A. Because the air they breathe is not
CARBONIC ACID.
207
pure, but is (in the 1st place) defective in
oxygen; and (in the 2nd) is impregnated
with carbonic acid gas.
765.
Q. Where does the carbonic acid of close
rooms and cities come from ?
A. From the lungs of the inhabitants,
the sewers, drains, and other like places, in
which organic substances are undergoing
decomposition.
766.
Q, What becomes of the carbonic acid of
crowded cities ?
A. Some of it is absorbed by vegetables ;
and the rest is blown away by the wind, and
diffused through the whole volume of the
air.
767.
Q. Does not this constant diffusion of
carbonic acid affect the purity of the whole
air ?
A. No ; because it is wafted by the win J
from place to place, and absorbed in its pas
sage by the vegetable world.
763.
Q. What is choke damp ?
A. Carbonic acid gas accumulated at the
208
CARBON.
bottom of wells and pits, which renders
them noxious, and often fatal to life.
769.
Q. Why is not this carbonic acid taken
up by the air and diffused, as it is in cities ?
A. Because (being heavier than common
air) it cannot rise from the well or pit: and
no wind can get to it, to blow it away.
770.
Q. Why are persons sometimes killed by
leaning over beer vats?
A. Because vats (where beer has been
made) contain a large quantity of carbonic acid
gas, produced by the ''vinous fermentation'*
of the beer ; and when a man incautiously
leans over a beer vat, and inhales the car-
bonic acid, he is immediately killed thereby.
771.
Q. Why are persons often killed, who en-
ter beer vats to clean them?
A. Because carbonic acid (being heavier
than atmospheric air) often rests upon the
bottom of a vat: when, therefore, a person
enters the vat, and stoops to clean the bottom^
he inhales the pernicious gas, which kills
him.
772.
Q. Why are persons sometimes killed by
having a charcoal fire in their bed-rooms ?
CARBONIC ACID.
209
A. Because the carbon of the burning char-
coal unites with the oxygen of the air, and
forms carbonic acid gas, which is a narcotic
poison.
773.
Q. If carbonic acid settles at the bottom
of a room, how can it injure a person lying
on a bed, raised considerably above the floor?
A. Because all gases diffuse themselves
through each other, as a drop of ink would
diffuse itself through a cup of water. If,
therefore, a person slept for six or eight
hours in a room containing carbonic acid,
quite enough of the gas will be diffused
throughout the room to produce death.
The heat of the fire assists the process of diffusione
774.
Q. What are the chief sources of carbonic
acid ?
A. 1st. — The breath of animals.
2nd. — The decomposition of vegetable
and animal matter.
3rd. — Lime-stone, chalk, and all calca-
reous stones, — in which it exists in a solid
form.
775.
Q. From which of these sources is carbo-
nic acid most likely to accumidate to a noxious
extent ?
18*
210 CARBON.
A. From the fermentation and putrefac-
tion of decaying vegetable and animal mat-
ters.
776.
Q. How can this accumulation of carbonic
acid be prevented ?
A. By throwing quick-lime into places,
where such fermention and putrefaction are
going on.
777.
Q. How will quick-lime prevent the accu-
mulation of carbonic acid ?
A. Quick-lime will absorb the carbonic
acid; and produce a combination called
" carbonate of lime.'^
778.
Q. Does not heavy rain as well as quick-
lime, prevent the accumulation of carbonic
acid ?
A. Yes; an abundant supply of water will
prevent the accumulation of carbonic acid,
by dissolving it.
N. B. Red heat (as a pan of red hot coals, or a piece of red hot iron/
will soon absorb the carbonic acid gas, accumulated in a pit or well.
779.
Q. What effect has carbonic acid on the
water in which it is dissolved ?
A. It renders it slightly acid to the tasto.
CARBONIC ACID. 211
780.
Q. Why does gunpowder explode ?
A, Because of the instantaneous produc-
tion and expansion of carbonic acid, sulphur-
ous acid, and nitrogen.
Gunpowder consists of 76 parts of nitre, 13 of charcoal, and 11 of sai
phur.
781.
Q. Why is boiled water flat and insipid ?
A. Because the whole of the carbonic acid
is expelled by boiling, and escapes into the
air.
782.
Q. Why does fresh spring water sparkle^
when poured from one vessel to another ?
Ao Because fresh spring and pump war
ter contain carbonic acid ; and it is the pre
sence of this gas which makes the watc
sparkle.
Much of the froth and bubbling of ale, beer, water, etc., when the)
are " poured high," is due to simple mechanical action.
783.
Q. Why is beer flat if the cask be left open
too long ?
A. Because too much of the carbonic acid
gas (produced by fermentation) is suffered to
escape.
784.
Q. Wliy are beer and porter made stale by
being exposed to the air ?
212
CARBON.
A. Because too much of the carbonic acid
gas (produced by fermentation) is suflfered tc
escape.
785.
Q. Why does beer turn flat if the vent peg
be left out of the tub ?
A. Because the carbonic acid gas escapes
through the vent hole.
786.
Q. Why does saUceratus make cakes light,
particularly if they are mixed with sour
milk?
A. Because the acid of the milk disen-
gages the carbonic acid contained in the sal-
seratus.
787.
Q. Why does wood decay ?
A. Because the oxygen of the air unites
with the carbon and hydrogen of the wood,
and forms carbonic acid and water.
788.
Q. Why do persons throw lime into bins
and sewersy to prevent their offensive smell,
in summer time ?
A. Because they contain large quantities
of carbonic acid gas, which readily combines
with lime ; and producing carbonate of limtj'
neutralizes the offensive gases.
CARBONIC ACID.
213
789.
Q. Why is quick-lime formed hy buniiiig
limestone in a kiln?
A. Because the carbonic acid (which ren
dered it mild) is driven off by the heat of
the kiln; and the lime becomes gxiich or
caustic
790.
Q. What is mortar ?
A. Quick-lime mixed with sand and
water.
791.
Q. Why does mortar become hard after a
few days ?
A. Because the lime re-imbibes from the
air the carbonic acid w^hich had been expelled
by fire ; and the loose powder again becomes
as hard as the original lime-stone.
792.
Q. Explain in what way mortar is ad-
hesive ?
A. When the carbonic acid is expelled
the hard lime-stone is converted into quick-
lime^ which, (being mixed with sand and
water) becomes a soft and sticky plaster ; but
as soon as it is placed between bricks, it m-
bibes carbonic acid again y and hardens into
lime-stone.
214
CARBON.
793.
Q. Wherein does lime-stone differ in ap-
pearance from quick-lime ?
A. Lime-stone is a hard, rocky substance ;
but quick-lime is friable.
794.
Q. How is the carbonic acid of water pro
duced ?
A. From the presence of lime, which is
frequently held in solution by hard water ;
when the carbonic acid escapes by exposure
to the air, the lime is deposited as a carbonate,
795.
Q. Why is hard water more agreeable to
dririk than soft water ?
A. Chiefly because it contains carbonic
acid.
796.
Q. Why is water fresh from the pump
more sparkling than after it has been drawi?
some time.
A. Because water fresh from the pump
contains carbonic acid, which soon esc-apes
into the air, and leaves the water flat and
stale.
797.
Q. Why should hard water (used for wash
ing) be expoped to the air ?
CARBONIC ACID.
21b
A. Because it is made more soft by ex-
posure to the aii.
Most spring water holds lime in solution as a bicarbonate, in conscq'^enco
of the presence of abundant carbonic acid. Carbonic acid escapes by ex-
posure to air — and the lime is, consequently deposited as a carbonate.
798.
Q. Why is hard water made more soft by
exposure to the air ?
A. 1st. — Because the mineral salts
(which cause its hardness) suhsida ; and
2nd. — Because the carbonic acid of the wa-
ter makes its escape into the air.
799.
Q. What is choke-damp ?
A. Carbonic acid gas accumulated at the
bottom of wells and pits. It is called choke
damp, because it chokes (or suffocates) every
animal that attempts to inhale it.
It suffocates without getting into the lungSj by closing the ouier orifice
spasmodically.
800.
Q. Why are rotting leaves hot?
A. Because the fermentation of rotting
leaves produces carbonic acid gas, which pro*
duction is always attended with heat. In
fact, rotting is a species of slow combustion.
N. B. The carbim of the leaves unites with the oxygen ol the air to pro-
dace carbonic acid gas, and the new combinations disturb latent he^t, and
make it g^r.aible.
216
CARBON.
§ — Effervescence .
801,
Q From what is the word effervesence de^
rived ?
A. From the Latin word effervesco (to
boil.)
802.
Q. Can the capacity of water for dissolv-
ing carbonic acid be increased ?
A. Yes. Carbonic acid may be forced
into water by pressure to a considerable ex-
tent.
803.
Q. To what practical uses has this capa-
city of water (for dissolving carbonic acid)
been applied?
A. Effervescing draughts are made upon
this principle.
804.
Q. Explain the cause of effervescence in
these beverages ?
A. The carbonic acid of the beverage
(being prevented by the cork from escaping)
is forced into the liquor by pressure, and ab-
sorbed by it ; but when the cork (or pres-
sure) is removed, some of the carbonic acid
flies off in bubbles or effervescence.
EFFERVESCENCE.
217
805.
Q. Why does aerated water effervesce
when the cork is removed ?
A. While the bottle remains corked, car-
bonic acid is forced into the water by pres-
sure, and absorbed by it; but, when the
cork {or pressure) is removed, some of the
(carbonic acid flies off in effervescence.
806.
Q. Why does soda water effervesce ?
A. In soda water there is forced eight
times its own bulk of carbonic acid gas,
which makes its escape in effervescence, as
soon as the cork is removed.
807.
Q. Why does ginger pop fly about in froth,
when the string of the cork is cut ?
A. Because it contains carbonic acid gas.
While the cork is fast, the carbonic acid is
forced info the liquor ; but when the pressure
is removed the gas is given off in effervescence.
N. B. All vinous fermentation produces carbonic acid..
808.
Q. Why does bottled ale froth more than
draught ale ?
A. Because the pressure is greater in a
bottle than in a tub which is continually
19
218
CARBON*
tapped ; and effervescence is always in
creased hy pressure.
809.
Q, What produces the froth of hottlei
porter ?
A. Carbonic acid generated by the vinoitn
fermentation of the porter : This gas is ab-
sorbed by the liquor ^ so long as the bottle is
well corked ; but is given off in froth, when
the pressure of the cork is removed.
810.
Q. What gives the pleasant acid taste to
soda water, ginger beer, champagne, and
cider ?
A. The presence of carbonic acid, gene-
rated by fermentation ; and liberated by
effervescence, when the pressure of the cork
is removed.
811.
Q. Why does the effervescence of soda wa-
rer and ginger beer so soon go off?
A. Because the carbonic acid (which pro-
duced the effervescence) very rapidly es-
r-apes into the air.
812.
Q. Why does the cork of a champagne
bottle fly off the instant it has been loosened
from the neck of the bottle ?
EFFERVESCENCE.
219
A. Because the vast quantity ot carbonic
acid gas contained in the liquor can no longer
be confined ; and, seeking to escape, drives
out the cork with great violence ,
813.
Q. When the cork of a champagne or soda
water bottle is drawn, why is a loud report
made?
A. Because champagne and soda water
both contain a great amount of carbonic acid
gas; which, being suddenly liberated, strikes
against the air, and produces the report.
814.
Q. Why does hartshorn take out the red
spot in cloth, produced by any acid ?
A. Because hartshorn is an alkali; and
the peculiar property of every alkali is to
neutralize acids.
SodT, pota?h, magfnesin, etc , are alkalies.
Upon this principle effervescing drinks are made of carbonate of soda
(an alkali) and citric or tartaric acid. Effervescence is produced, by th*
giving off of carbonic acid during the process of neutralization.
N. B. The carbonic acid is formed by the carbon (of the carbonate o*
•oda) combining with the oxygen of the acid.
815.
Q. What is an alkali ?
A. The converse of an acid ; as bitter is
the converse of sweet , or insipid the converse
of pungent.
220
CARBON.
SECTION II. CARBURETTED HYDROGEN.
816
Q. What is marsh-gas or fire-damp ?
A, Carburetted hydrogen gas accumulated
on marshes, in stagnant waters, and coal*
pits; it is frequently called ^^inflammable
air."
817.
Q. What is carburetted hydrogen gas ?
A. Carbon combined with hydrogen
818.
Q. How in%y carburetted hydrogen gas be
procured on niarshes ?
A. By stirring the mud at the bottom of
any stagnant pool, and collecting the gas (as
it escapes upwards) in an inverted glass
V vessel.
819.
Q. What is coal gas ?
A. Carburetted hydrogen extracted from
coals by the I eat of fire.
820.
Q. Why is carburetted hydrogen gas
called fire-damp or inflammable air ?
A. Because it very readily catches fire ana
exjjlodes, when a light is introduced to it.
Provided atmosphere air be present
CARBURETTED HYDROGEN.
221
821.
Q. Why is carburetted hydrogen gas fre-
:pently called marsh-gas ?
A. Because it is generated in meadows and
marshes from putrefying vegetable sub-
stances
See Ignis faluus.
822.
Q. What gas is evolved by the wick of
a burning candle ?
A. Carhuretted hydrogen gas : The carbon
and hydrogen of the tallow combine into a gas
from the heat of the flame ; and this gas is
called carburetted hydrogen or inflammable
air.
823.
Q. Why do coal-mines so frequently ex-
plode ?
A. Because the carburetted hydrogen ga.s
(which is generated in these mines by the
coals) explodes, when a light is incautiously
introduced.
824.
Q. How can miners see in the coal-pits if
tliey may never introduce a light ?
A. Sir Humphrey Davy invented a lan-
tern for the use of miners, called "the Safety
Lamp/' which may be used without danger.
19*
222
CARBON.
825.
Q. Who was Sir Humphreij Davy?
A. A very ingenious chemist, born in
Cornwall, 1778, and died in 1829.
826.
Q What kind of thing is the safety lampf
A. A kind of lantern, covered with a fine
gauze wire, instead of glass or horn.
827.
Q. How does this fine gauze wire prevent
an explosion in the coal-mine ?
A. By preventing the flame of the lamp
from communicating with the inflammable
gas of the mine.
N. B. The interstices of the gauze wire must not exceed the seventh of
an inch in diameter
828.
Q. Why will not flame pass through very
fine wire gauze ?
A. Because the metal wire is a very ra-
pid conductor of heat ; and when the flame
(of gas burning in the lamp) reaches the
wire gauze, so much heat is conducted away
by the wire, that the flame is extinguished.
829.
Q. Does the gas of the coal-pit get through
the wire gauze Into the lantern ?
A. Yes; and the inflammable gas ignites,
and burns inside the lamp : As soon as this
PHOSPHORUS.
223
is the case, the miner is in danger, and should
withdraw.
830.
Q. Why is the miner in danger if the gas
ignites and burns in the inside of the safety
lamp ?
A. Because the heat of the burning gas
will soon destroy the wire gauze ; and then
the flame (being free) will set fire to the
mine.
N. B. When the carburetted hydrogen gas takes fire from the miner'n
candle, the miner sometimes perishes in the blast of tJie Jlame, and some-
times suffers suffocation from the carbonic acid which is thus produced.
CHAP, v.— PHOSPHORUS AND PHOSPHU-
RETTED HYDROGEN.
SECTION I. PIIOSPHORirS.
831.
Q. What is phosphorus ?
A. A pale amber-colored substance, re-
sembling wax in appearance. The word is
derived from two Greek words which mean
^'to produce or carry light, cpog cpsQeiv [phoH-
pherein.]
832
Q. How is phosphorus obtained ?
A. By heating bones to a white heat;
by which means, the animal matter and
224 PIIOSPIIURETTED HYDKOGEN, ETC.
charcoal are consumed and a substance called
''phosphate of lime,'' is left behind.
833.
Q. What is the phosphate of lime?
A. Phosphorus united to oxygen and
Ume ; when sulphuric acid is added, and the
mixture heated, the lime is attracted to the
acid, and pure phosphorus remains.
If powdered charcoal be added, phosphorus may he procured by dis-
834.
Q. When, and by whom was phosphorus
discovered ?
A. This element was discovered in 1669,
l3y Brandt of Hamburg.
835.
Q. Is phosphorus inflammable ?
A. It is so exceedingly inflammable it
sometimes takes fire by the heat of the hand;
it therefore requires great care in its ma-
nagement as a blow or hard rub will very
often kindle it.
836.
Q. Of what is the ignitable part of Lu-
cifer matches made ?
A. Of phosphorus; above two hundred
and fifty thousand pounds are used every
year in London alone, merely for the muini-
fncture of Lucifer matches.
PHOSPHORUS.
228
837.
Q. Why will Lucifer matches ignite by
merely drawing them across any rough
fiurface ?
A. Because they are made of phosphorus ^
which has an affinity to oxygen at the low-
est temperature ; insomuch that, the little
additional heat, caused by the friction of
the match across the bottom of the lucifer-
box, is sufficient to ignite it; and at the
same time to ignite the sulphur with which
the match is tipped.
838.
Q. What peculiar property has phospho-
rus ?
A It is luminom in the dark ; and even
in day-light appears to be surrounded by
a ligtit cloud.
839.
Q. Why are putrefying fish luminous ?
A. Because the carbon of the fish, unit-
ing with oxygen, forms carbonic acid ; and
the phosphoric acid of the fish (being thus
deprived of oxygen) is converted into phos-
phorus : as soon as this is the case, the
phosphorus begins to unite with the oxygen
of the air, and becomes luminous.
Carbonic acid is a compound of carbon and oxygen.
Phoephorfc acid is a ?ompound of phosphorus and oxygen. If y Because a "watery vapor'' is made,
by the combination of the hydrogen of taU
low with the oxygen of the air ; and this
V
FLAME.
257
*' vapor'' is condensed by the cold glass held
above the flame.
964.
Q. Why does the hand, held above a can-
dle, suffer more from heat, than when it is
placed below the flame, or on one side of it.
A. Because the hot gases and air (in
their ascent) come in contact with the hand
placed above the flame ; but when the hand
is placed belovj the flame, or on one side, it
only feels heat from radiation.
" Radiation," — tliat is, emission of rays. The candle flame throws oul
rays of light and heat in all directions; but when the hand is held above
the flame, it not only feels the heat of the rays but also of the ascending
current of hot air, etc.
965.
Q. Why is a rush-light extinguished more
readily than a cotton wick candle ?
A. Because a hafd rush imbibes the
melted fat or wax much more slowly than
porous cotton ; as it imbibes less fat, it sup-
plies a smaller volume of combustible gases^
and, of course, the light is more easily ex-
tinguished.
966.
Q. Why is it more difficult to blow out a
cotton wick than a rush-light ?
A. Because porous cotton, imbibes the
melted fat or wax, much more readily than
hard rush; as it imbibes more fat, it sup-
22^
258
COMBUSTION.
plies the flame with a larger volume of
combustible gases ; and, of course, the light is
with more difficulty extinguished.
967.
Q. Why is a gas flame more easily ex-
tinguished when the jet is very slightly
turned on, than when it is in full stream?
A. Because there is less volume of com-
bustible gases in the small flame, than in
the full blaze.
968.
Q. Why does an extinguisher put a can-
dle out?
A. Because the air in the extinguisher
is soon exhausted of its oxygen by the flame;
and when there is no oxygen flame goes
out.
969.
Q. Why does not a candle set fire to a
piece of paper twisted into an extinguisher,
and used as such?
A. 1st. — Because the flame very soon
exhausts the oxygen contained in the paper
extinguisher; and
2nd. — The flame invests the inside of the
paper extinguisher with carbonic acid gaSt
which prevents it from blazing.
FLAME.
259
970.
Q. Why is a long wick never upright ?
A. Because it is bent by its own weight.
971.
Q. A long wick is covered with an ^^fflor^
escence at the top. What does this aris^o
fiom ?
A. The knotty or flowery appearance of
the top of a wick arises from an accumula-
tion of particles partly separated but still
loosely hanging to the wick.
972.
Q. \Yliy do common candles require snuff-
ing?
A. Because the heat of the flame is not
sufficient to consume the wick; and the longer
the wick grows the less heat the flame pro-
duces.
973.
Q. Why do wax candles never nee J
snuffing ?
A. Because the wick of wax candles is
made of very fine thread, which the heat of
the flame is sufficient to consume. The
wick of tallow candles (on the other hand,)
is made of coarse cotton, which is too sub-
stantial to be consumed by the heat of ih^
flame, and must be cut off by snuffers.
260
COMBUSTION.
974.
Q. Why does a pin stuck in a rush-light
p.xtinguish it ?
A. Because n> pin (being a good conduc-
tor) carries away the heat of the flame from
the wick, and prevents the combustion of
the tallow.
975.
Q. What is the smoke of a candle?
A. Solid particles of carbon, separated
from the wick and tallow, but not con-
sumed.
976.
Q. Why are some particles consumed and
not others ?
A. The combustion of the carbon depends
upon its combining with the oxygen of the air ;
now as the outer surface of the jflame pre-
vents the access of air to the interior parts,
much of the carbon of those parts passes
off in smoke.
977.
Q. Why does a candle flicker, especially
just previous to its being burnt out ?
A. Because it is unequally supplied with
combustible gases. When a candle is
nearly burnt out, there is not sufficient tal-
low or y/ax to keep up the regular supply
FLAME.
of combustible gas ; in consequence of
which, the flame flickers, that is, blazes^
when it is supplied with gas, and goes
out for a moment when the supply is do
fective.
PART 111.
METALS.
CHAP. L— METALS AND ALLOYS.
SECTION I. METALS.
978.
Q. If you heat steel red hot\n the fire, and
then plunge it suddenly into cold water it
becomes hard and hrittle ; why is this ?
A. Because the sudden chill violently ex-
pels the latent heat, which would have
settled in the steel, had it been allowed to
cool slowly.
The malleability and toughness of metals depend - upon their power of
; absorbing heat.
979.
Q. What is Uock tin ?
A. Tin purified by heat, and run into
moulds, which ^orm blocks of great size.
980.
Q. What is sheet tin, such as is used in tlie
manufacture of pans and other utensils ?
A. It is sheet iron dipped into melted tin
a portion of which adheres to the surface
262
METALS.
263
as tiij, and another enters into the iron and
alloys with it.
The ancients are supposed to have made use of tin, and there is good
reason for believing that it was obtained by the Phenlcians, from Corn-
wall and Spain, at least 1000 years before Christ.
981.
Q. How is steel made from iion?
A. The iron is surrounded with charcoal,
and placed, during six or eight days, in a
furnace intensely heated ; the carbon unites
with the iron, and forms what is called
'^carburet of iron" (or steel.)
982.
Q. What is meant by shear steel ?
A. Shear steel derives its name on ac-
count of its being used for making shears,
for dressing woolen cloth. Shear steel is
broken and welded frequently in order to
prepare it.
Welded, that is, hammered together again.
983.
Q. What is the white lead, used for paint ?
A . It is prepared by placing sheets of
load over earthen pots, which contain weak
acetic acid, and stand u]3on tan or dung.
The lead being corroded with the acid,
unites with the carbon and oxygen evolved
from the dung.
264 METALS AND ALLOYS.
SECTION II. ALLOTS.
984.
Q What are the component parts of the
coins of the United States.
A They are made oi gold, silver, and cop-
pe??
90 parts of gold, ^ of silver, and 7^ copper.
985.
Q. What are the component parts of the
\\lver coins of the United States ?
A. Silver and copper.
90 parts silver, 10 copper.
986.
Q. What is jeweller's gold ?
A. An alloy of gold and copper, with
silver — this gold is liable to tarnish, but its
brilliancy can easily be restored, by im-
mersing the metal in ammonia.
987.
Q. What is Dutch gold?
A. It is properly an alloy of copper and
zinc ; but the name is generally applied to
the bronze and copper leaf which is made in
Germany, and sold like gold leaf, in books.
988.
Q. What is German silver ?
A. German silver, or white copper, some-
ALLOTS. 265
times called Argentan, is an alloy of copper,
zinc, and nickel.
The be«t is made of 50 parts copper, 25 zinc, and 25 nickel.
989.
Q What is brass ?
A It is an alloy composed of copper and
tmc.
Good brass contains about 2 parts copper, to 1 of zinc.
990.
Q. ^h^ii^ bell metal?
A. An alloy of copper and tin. The pro
portions should be 78 of copper, to 22 of
tin. Large bells contain more copper than
small ones.
991.
Q. Wliat is pewter ?
A. An alloy of tin and lead.
In the following proportions: 1 part lead, 20 parts tin.
992.
Q. What is Britannia metal, such as coffee
and tea-pots, etc., are made of?
A. It is an alloy of tin with lead, copper,
antimony, etc., according to its quality.
993.
Q . How is iron galvanized ?
A. By plunging it into melted zmc;
when an alloy is formed on the surfoce,
which prevents oxidation, or (rust,)
23
266 GLASS, PORCELAIN, EARTHENWAKE.
994.
Q. What is common solder ?
A. Solder is a mixture of lead and tin.
Fine solder^ 2 parts tin, and 1 lead
Coarse '< i *< u 4 u
CHAP. IL— GLASS, PORCELAIN, EARTHED
WARE.
995.
Q. What is glass ?
A. Glass is a mixture of silex and an
alJcaliy usually the carbonate of potash or
soda, with lime or oxide of lead, according
to the quality of glass to be manufactured.
These substances are melted together at a
high temperature, which expels the carbonic
acid. The mass is left to cool, until it is in
a proper state for working.
996.
Q. How is glass worked ?
A. Articles of blown glass, such as bot-
tles, etc., are made thus: The workman has
an iron tube, five or six feet long, with a
mouth piece of wood, to prevent the heat of
the tube from injuring his mouth ; this tube
he mserts into the pasty glass, a,nd collects
a lump large enough to form a bottle ; he
then rolls it on a marble slab into a pear-
shaped ball ; this is inserted into a metal
OLASS, PORCELAIN, EARTHENWARE. 261
mould which opens and shuts on hinges,
he then blows through the tube so as to ex-
pand the cooling glass into the shape of the
mould. The mould is then opened and the
bottle is taken out at the end of the tube ; it
is then touched y/ith a rod of cold iron, which
cracks off the bottle at its mouth piece.
997.
Q. How is plate glass made ?
A. It is cast on a flat metal table, and
after careful annealing, it is ground and
polished by machinery.
" Annealing,^^ a process which renders glass less brittle or liable to
break. This extreme brittleiiess is prevented by placing the glass in an
oven, where it will cool very slowly. It requires some hours, or even days,
to oool. This is called annealing.
998.
Q. How is plate glass ground ?
A. One plate of glass is attached to a ta-
ble, another smaller one is firmly fixed in a
wooden frame. The smaller one is made
to move ( )ver the low^er plate by means of
machinery. At first, moistened sand is
thrown between the plates; as they become
smoother, wet emery of different degrees of
fineness h used, instead of the sand; lastly
it is polished with putty of tin.
Putty of tin " is made thus: 1 i is heated above its melting point:
it then oxidizes rapidly, becoming <-'• iverted into a whitish powder used
in the arts for polishing under the n^.i}e of putty powder^ or putty of tin.
9 ) 9.
Q. For what purpo,-es is plate glass used ?
268 GLASS, PORCELAIN, EARTHENWARE.
A. For mirrors and large window panei^
icoo.
Q. How are mirrors made ?
A. They are made of plate glass, covered
with an alloy of mercury and tin.
The alloy is formed of 30 parts raercury, 70 tin
1001.
Q. What is porcelain ?
A. All kinds of china ware, such as are
used for dishes, cups, etc., are denominated
porcelain — some kinds are much finer and
more beautiful than others.
1002.
Q. Of what is porcelain composed ?
A. The chief materials used in its manu-
facture are a certain clay derived from de-
composed feldspar, calcined flints finely
ground, together with a portion of feldspar
reduced to powder.
" Feldspar,'*^ a kind of mineral. " Calcined,^^ heated i otensely hot so
M to crumble.
1003.
Q. How are these materials mixed to
gether ?
A. They are put into a kind of mill^
which is a large cylindrical vessel or tub,
into which a small stioam of water is con-
stantly suffered to tri( ide, the mass is now
ground or mixed irlj a kind of pap oi
GLASS, PORCELAIN, EARTHENWARE. 269
doLigli. This dough is kneaded or worked
with the hands until the mass is quite
smooth and of a uniform color. It is now
ready for moulding.
1004.
Q What is moulding .
A Forming the dough or paste into the
ahape required, such as bowls, plates, cups,
etc
1005.
Q. How are these articles moulded ?
A. The operation is performed on a ma-
chine called a potters' lathe. A small piece
of the clay or dough is placed upon this
lathe, and owing to the rapid rotary motion
of thp machine, the workman is able to
shape a vessel by keeping his hands con-
stantly wet ; he moulds it to a proper size
by means of pegs and guages. It is now
suffered to dry partially ; it is then placed
upon another lathe, when it is shaped more
evenly and accurately, and nicely smoothed
and burnished with a smooth steel surface.
The vessels are then put in a kiln and
baked.
1006.
Q. How long is porcelain usually baked?
A, It requires forty hours or more.
23*
270 GLASS, PORCELAIN, EARTHENWARE.
1007.
Q. How is the gloss given to our china
plates ?
A. This is called glazing. Glaze is made
in various ways, according to the quality of
the articles to be glazed.
Gypsum, silica, and a little porcelain clay
are ground together and diffused through
water. Sometimes a little lead is added.
Each article is dipped for a moment in this
mixture and withdrawn, the water sinks
into the substance, leaving the powder
evenly spread on its surface. They are
once more dried, and put in a kiln which is
fired at an extremely high temperature. It
is then finished, unless it is to be gilded or
otherwise ornamented.
1008.
Q. How is stoneware, such as is used for
jugs, jars, etc., made ?
A. This is a very coarse kind of porce-
lain, made from clay containing oxide of
iron and a little lime.
1009.
Q. How is stoneware glazed ?
A. By throwing common salt into the
heated furnace ; this is volatilized by the va-
por of water which is always present, and
GLASS, PORCELAIN, EARTHENWARE. 271
the silica of the clay of which the ware is
coiDj^osed. This fuses over the surface of
the ware, and gives a thin but excellent
glaze.
Volatilize ^''^ to fly off. " Fwses," melts or liquefies by heat.
1010.
Q. What is earthenware ?
A. This is composed of a species of clay
mixed with silica. It is moulded in the
same manner as porcelain, dried and baked
in a kiln ; after that, it is glazed with a mix-
ture which contains the oxides of lead and
tin, after which it is reheated.
Articles g^lnzed with this mixture, are very improper for culinary vea
ldl3, aa the lead in the glaze is affected by acids.
PART IV.
ORGANIC CHEMISTRY.
1011.
Q. What are the elements which compose
organic substances generally ?
A. All organic substances, with com-
paratively few exceptions, are composed of
carbon, hydrogen, oxygen and nitrogen.
Sulphur and phosphorus are occasionally associated with these, anl
also certaiti compounds containing chlorine, iodine, etc.
CHAP. I.— SUGAR.
1012.
Q. Of What is sugar composed ?
A. Of carbon^ hydrogen and oxygen.
1013.
Q. Is sugar a vegetable substance ?
A. Yes ; it is found in the juice of many
plants and in the sap of several trees ; but
Lt is extracted in the greatest abundance
from the juice of the sugar-cane, which is
cultivated for that purpose in our Soutlieri)
States.
SUGAR.
273
1014.
Q. From what other sources is sugar ob-
tained ?
A, From the sugar maple which grows
tibundaiitly in the United States, and ivom
beet root.
The sugar maple is a species of maple, the botanical name of whicfc it
ttcer saccharinum ; it thrives better in New York and Pennsylvania thao
elsewhere.
1015
Q. How is sugar made from the sugar
cane ?
A. The cane is crushed, and the ex-
pressed juice mixed with a small quantity
of slacked lime, and heated to near the
boiling point; the clear liquid thus pro-
duced is rapidly evaporated in an open pan,
after which it is transferred to a shallow
vessel and left to crystallize, during which
time it is frequently agitated, in order to
liinder the formation of large crystals ; it
is then drained from the syrup, or molasses.
This is what is called raw or Muscovado
sugar ; after which it is refined.
1016.
Q. How is sugar refined ?
A. By re-dissolving it in water, and add-
ing a certain quantity of albumen in the
shape of blood or white of egg, and some-
274
SUGAK.
times a little lime-water, and heating tliQ
whole to the boiling point.
1017.
Q. What effect has the albumen on the
sugar ?
A. It coagulates, and forms a kind of net-
work of fibres, which enclose and separate
from the liquid all the impurities suspended
in it.
1018.
Q. What is the next process towards
making sugar ?
A. It is then filtrated through charcoal,
evaporated and put into conical earthen
moulds, where it solidifies. It is then
drained and dried, and the product is the
ordinary loaf sugar.
1019
Q. What is grape sugar ?
A. It is the sugar of fruits, and is abun-
dantly diffused throughout the vegetable
kingdom. It is called grape sugar, because
it exists naturally in the juice of grapes.
FERMENTATION.
275
CHAP n — FERMENTATION AND PUTRE-
FACTION.
SECTION I. FERMENTATION.
1020.
Q What is fermentation ?
A. Fermentation is the change effected in
he elements of a body composed of carbon^
hydrogen and oxygen.
1021.
Q. What new compounds are produced by
the change called fermentation ?
A. Alcohol and carbonic acid,— The alco-
hol is still further changed (unless the pro-
cess be checked) into acetic acid or vinegar.
1022.
Q. What are the elements of grape sugar?
A. Carbon, oxygen, and hydrogen, all in
equal proportions.
1023.
Q. What changes does sugar undergo by
fermentation ?
A. It is first decomposed, and then its
elements re-unite in different proportions,
producing alcohol, carbonic acid, and water.
OfsuGAK, one portion is alcohol; and another carbonic acid; as may
>e seen by the following table :
Carh, Oxy. Hyd.
Every atom of anhydrous sugar contains ... 12 12 12
Two atoms of alcohol contain 8 4 12
Four atoms of carbonic acid contain 4 8 0
12 12~^ 12
N B. Anliydroas sugar," is sugar dried at 300°.
276 FERMENTATION AND PUTREFACTION.
1024.
Q. How does sugar form alcohol by fer
mentation ?
A. Two-thirds of its carbon and one-third
ol* its oxygen re-unite with the hydrogen,
*ind generate alcohol.
1025.
Q. How does sugar form carbonic acid by
fermentation ?
A. The remaining one-third of its carbon
and twO'thirds of its oxygen re-unite, and
generate carbonic acid.
1026.
Q. What becomes of the alcohol which is
thus generated by fermentation ?
A. It mixes with the water, and forms
the intoxicating j)art of beer and wine.
1027.
Q. What becomes of the carbonic acid,
which is generated by fermentation ?
A. It makes its escape into the air.
1028.
Q. Why is barley malted ?
A. Because germination is produced by tho
artificial heat; and in germination, the starch
r)f the grain is converted into sngar.
1029
Q, What is alcohol ?
FERMENTATION.
277
A. The spirit of beer and wine, obtained
by fermentation,
1030.
Q. Of what elements is aj/coM composed?
A . Of carbon, oxygen, and hydrogen
Of Ai/^OHOLj 4 parts are carbon, 2 oxygen, and 6 hydrogen.
1031.
Q. What is the origin of the term proof
npirit 7
A. It IS derived from the old method of
testing spirit, which was thus : The spirit
to be tested was poured over gunpowder, and
ignited ; if the powder exploded, the spirit
was said to be above proof ; if it did not ex-
plode, it was said to be below proof.
1032.
Q. What is meant, at the present day,
by spirit above and below proof?
A. If we say that spirit is ten over proof,
we mean, that one hundred gallons of it will
require ten gallons of water to reduce the
spirit to proof strength. So on the converse .
if we say that spirit is ten under proof, we
mean that ten gallons of water must be taken
from the spirit to raise it to proof strength.
The strength of spirit is now tested by an instrument called the hydro
meter.
1033.
Q. What wines contain the most spirit,
and what the least ?
24
278 FERMENTATION AND PUTREFACTION.
A, Champagne IS' one of the weakest wines,
then hock, then sherry, and Port is one of
the strongest. Pour glasses of Port are
nearly equal to five of sherry.
Champagne contains about 12 r)er cent of alchchoi
Hock " " 13 "
Claret « " 16*'* " "
Sherry « " 19 «
Port " « 23^ «
1034.
Q. Why is it not needful to put yeast into
grajf?^ juice, in order to j)roduce fermenta-
tion?
A. Because grape juice contains a suffi-
cient quantity of a nitrogenized substance
(like yeast) to produce fermentation.
Nitrog-enized, that is, containing nitrogen.
1035.
Q. Why do not grapes ferment, while they
hang on the vine ?
A. Because the water of the juice evapo-
rates through the skin, and allows the
grapes to shrivel and dry up, after they are
ripe.
I'ermentat.ion cannot occur unless the sugar be dissolved in a sufSciea
\ ianti*y of water.
1036.
Q What is gluten ?
A. A tough, elastic substance, comj^osed
of carbon, oxygen, hydrogen, and nitrogen.
1037.
Q. Does malt contain gluten ?
FERMENTATION.
279
A. Yes. The infusion of malt, callecl
sweet- wort'' contains an abundance of
gluten ; and the yeast (which converts itb
sugar into alcohol) converts this gluten into
yeast.
1038.
Q. How is barley malted .
A. It is moistened with water ^ and heaped
up; by which means, great heat is produced,
which makes the barley sprout.
(See " spontaneous combustion.")
1039.
Q. Why is not the barley suflfered to grow
as well as sprout ?
A. Because plants in the gerrn contain
more sugar than in any other state ; as soon
as the germ puts forth shoots, the sugar of
the plant is consumed, to support the shoot.
1040.
Q. How is barley prevented from shooting
in the process of malting ?
A. It is put into a kiln, as soon as it
sprouts, and the heat of the kiln checks or
destroys the young shoot.
1041.
Q. What is yeast ?
A. The foam of beer (or of some similar
liquor) produced by fermentation.
280 FERMENTATION AND PUTREFACTION.
1042.
Q. Why is yeast used in brewing ?
A. Because it consists of a substance call*
ed gluten, undergoing putrefaction ; in
which state it possesses the peculiar pro-
perty of exciting fermentation.
If the gluten were not in a putrefying state, it could not produce r«jer-
mentation.
1043.
Q. Why is yeast needful in order to make
malt into heer ?
A. Because the presence of a putrefying
body containing nitrogen is essential, in
order to convert sugar into alcohol.
1044.
Q. What effect has yeast upon the sweet-
wort ?
A. It causes the sugar to be converted
into alcohol and car bonic acid ; and its glu-
ten into yeast.
1045.
Q. Why is porter much darker than ale or
beer?
A. Because the malt of which porter in
made, is dried at a higher temperature, ap^d
slightly charred.
Small beer is a weak wort fermented, and contains 1^ per cent, of ^
tohol.
Ale is a stronger wort, and contains 7 per cent, of alcohol.
Porter contains 4^ per cent, of alcohol.
Brown Stout contains Of per cent, of alcohol.
Burton Ale contains 8^ per cent, of alcohol.
N. B. Wort " is tlie fermentable infusion of malt or grain.
FERMENTATION,
281
1046.
Q. What is the /ro/A or of fenneiited
liquors ?
Putrefying glutinous substances (of a
nature similar to yeast,) which rise to the
smfacG from their lightness.
1047.
Q Why is beer flat if the cask be left open
too long ?
A. Because too much of the carbonic acid
gas (produced by fermentation) is sulfered
to escape.
1048.
Q. Why are beer and porter made stale by
being exposed to the air ?
A. Because too much of the carbonic acid
gas (produced by fermentation) is suffered
to escape.
1049.
Q. Why does beer turn flat if the vent peg
be left out of the tub ?
A. Because the carbonic acid gas escapes
through the vent hole.
1050.
Q. Why does milk turn sour by keeping?
A, Because it undergoes a fermentation ;
during which ^'lactic acid'^ is formed, which
(urns the milk sour.
The lactic acid is formed from the sugar of milk by fei mentation.
24*
282 FERMENTATION AND PUTREFACTION.
1051.
Q. Why does milk turn sour in hot wea
ther much sooner than in cold ?
A. Because heat very greatly accelerates
the process of fermentation ; during which
lactic acid is formed, which turns the milk
sour.
1052.
Q. Why can you never boil stale milk with-
out curdling it ?
A. Because stale milk is in an incipient
state of fermentation, which the heat of
the fire greatly accelerates ; The lactic
acid which is formed during fermentation,
mixing with the casein of the milk, coagu-
lates it.
1053.
Q. Why does a small portion of corrosive
sublimate keep paste from turning sour ?
A. Corrosive sublimate being a powerful
antiseptic, prevents fermentation, which is
the cause of the paste turning sour
1054.
Q. What is bread ?
A. It is a kind of food prepared gene-
rally from the flour of wheat mixed with wa-
ter to a dough, and submitted to the actioii
of heat to bake. This kind of bread is call-
ed mfermented or unleavened bread.
FEEMENTATION.
283
1055.
Q. What is leavened bread ?
A. It is flour mixed to a dough with v. a-
ter, to which is added a little leaven, (or
dough which has been fermented) or yenjf^
1056.
Q. What effect has the yeast on the
dough ?
A. It assists in the fermentation of the
dough, by which means, carbonic acid is
generated in the mass, and makes the
bread porous and light. It is then placed in
the oven, and this gas expanding by heat
rises the dough still more, and puts a stop
to any further fermentation.
1057.
Q, How does fermentation make the dough
rise ?
A. During fermentation, carbonic acid gas
is evolved; but the sticky texture of the
dough will not allow it to escape; so it
forces up little bladders all over the dough.
1058.
Q. Why is new bread indigestible ?
A. Because the change called "panary
fermentation,'' is not completed.
" Panary," from the Latin word Panis (bread ;) " panary fermentatiOA*
liM»ons the fermentation that dough undergoes in order to become bread.
The sugar of the dough is converted into
284 FERMENTATION AND PUTREFACTION.
alcohol and carbonic acid by fermentation :
the dough being adhesive prevents the es-
cape of these products, till the mass is
baked; when the gas expands, bursts
lb rough the mass, leaving a number of
holes or bladders, to show where it was
confined.
So long as the bread is warm, the pro-
cess of fermentation is going on ; and,
therefore, bread should never be eaten till
it is twent/j-four hours old.
105 9.
Q. Wliy does baking dough convert it
into bread ?
A. When dough formed of flour, is baked,
its starch is changed into a gum called
dextrin.
A similar change is produced upon the
farinaceous portion of the dough. The
yeast (added to the dough) converts part
of the starch and sugar into alcohol and
carbonic acid; of these, the alcohol evapo-
rates in the oven, and the carbonic acid
forces the dough into bubbles, in its eifort
to escape, rendering the bread light and
full of holes.
In 100 lbs. of bread, and 100 lbs, of dough we have,
Starch, Sugar, Dextrin,
In dough, 68 lbs. 5 lbs. Oh 100
?n Uread, 53^ " 3^ «< 18 m 10(7
FERMENTATION.
285
Whereby it will be seen, that 16 J lbs. of starch have been converted
ilto the gum called dextrin, by baking.
Dextrin is a gummy matter similar to that which composes the cells of
Wood (called cellulin) only it is soluble in cold water.
Diastase is a peculiar vegetable principle of malt, extracted bv watefv
which converts starch into dextrin or sugar.
1060.
Q. Why is dough placed before the fire
A. 1st. — Because the heat of the fire in-
creases the fermentation ; and
2nd. — ^It expands the gas, confined in the
little bladders; in consequence of which,
the bladders are enlarged, and the dough
becomes lighter and more porous,
1061,
Q. Why will dough not rise in cold wea-
ther unless it be placed near the fire ?
A. Because it gets cold and then the air
in the little bladders condenses — the paste
falls — and the bread becomes close and
heavy.
1062.
Q. Why is well made bread full of holes
or bubbles?
A. Because the fermentation of the dough
throws up little bubbles filled with carbonic
acid gas ; and when the dough is baked,
these bubbles are made permanent in the
bread.
286 FERMENTATION AND PUTREFACTION.
SECTION II. PUTREFACTION
1033
Q. What is the difference, between fermefu
tation and putrefaction ?
A . Fermentation is a change effected in
llie elements of a body composed of car-
bon, oxygen, and hydrogen, without nitro*
gen. Putrefaction is a change effected in
the elements of a body composed of car*
bon, oxygen, hydrogen, and nitrogen.
1064.
Q. What new compounds are produced
by the change called putrefaction ?
A. The carbon, oxygen, hydrogen, and
nitrogen, of the original substance (being
separated by decomposition) re-unite in the
following manner. 1. Carbon and oxygen
unite to form carbonic acid. 2. Oxygen and
hydrogen unite to form tvater. 3. Hydro-
gen and nitrogen unite to form ammonia.
Hartshorn is a solution of ammonia in water.
N. B. When bodies containing sulphur and phosphorus putrefy, the
sulphur Oiud phosphorus unite with hydrogen, and form sulphuretted and
pkosphuretted hydrogen gases.
1065.
Q. What becomes of these several pro
ducts of putrefaction ?
A. They are all elastic bodies, and es*
cape into the air.
N B. Water is elastic and gaseous when in the condition of vapor.
PUTREFACTION.
287
1066.
Q. What is the cause of the offensiv^^
mell which issues from putrefying bodies ?
A. The evolution of ammonia^ or of snU
phuretted and phosphuretted hydrogen gases ;
all of which have pungent and offensive
odors.
1067.
Q. What change is produced in gluten
by putrefaction ?
A. Its elements are loosened from their
former conditions of combination, and re-
arranged (with the addition of oxygen from
the air) into a new series.
1068.
Q. Why do boiled eggs discolor a silver
spoon ?
A. Because they contain a small portion
of sulphur, which unites toith the silver (for
which it has a great affinity) and tarnishes
Ur^h tn» tfvhite and yolk contain sulphur— the latter more abundantly.
1069.
Q. What causes the offensive smell of
stale hard boiled eggs ?
A. The hydrogen of the egg combining
with the sulphur and phosphorus, form suU
288 FERMENTATION AND PUTREFACTION.
phuretted and phosphuretted hydrogen ; both
of which gases have an offensive odor.
Of an ecrcr 55 parts are carbon, IG nitrogen. 7 hydrogen, and the re^
maining '22 are oxygen, phosphorup, and sulphur.
1070.
Q. Decaying vegetables are first of a
brownish tint, why do they afterwards turn
of a blackish color ?
A. Because the hydrogen of the decaying
vegetables is separated from the mass by
the process of decay, and leaves a larger
proportion of carbon behind.
Vegetable fibre contains 52^- per cent of carbon.
When partially decayed 54 " *' "
When black with decay 56 " " "
1071.
Q. Why are decaying vegetables always
moist?
A. Because the hydrogen and oxygen of
the vegetables, are given up by decay, and
form into water.
Decaying vegetables combine into the following new forms : 1st. — The
oxygen and hydrogen form into water; and 2nd. — The carbon unites
with the oxygen of the air, and produces carbonic acid gas.
1072.
Q. Why does meat putrefy sooner in hot
damp weather, than in cold ?
A. Because the carbon of the meat
unites with the oxygen of the air more
readily when hot than cold ; and
Because the damp deposited on the sur-
face of the meat, is of itself one of the
PUTREFACTION.
289
compounds of putrefaction, and leaves an
excess of hydrogen in the meat.
Thus the original proportions and com*
Li nations of the meat are altered and de-
composed.
Patrefac lion is simply the decomposition of the original elements, and
leir ' e-uniou in a new order. The new order i^ as follows : —
1st — Carbon and oxygen unite to form carboni? acid ;
2nd. — Hydrogen and oxygen " " water;
3rd. — Hydrogen and nitrogen " " ammonia.
N B. Carbon unites with oxygen with a readiness proportioned to itt
heat ; when red hot, the combination is most easily effected.
The chief reason why salt preserves meat is because it absorbs the wa»
.er from it, and deprives it of hydrogen.
1073.
Q. Why does meat putrefy most rapidly
in very changeable weather ?
A. Because moisture is more freely de-
posited on the meat in very changeable
weather ; and this moisture is a chief com-
pound of putrefaction.
1074.
Q. How can the taint of meat be re-
moved ?
A. Either by washing with pyroligneous
acid — or by covering it for a few hours
with common charcoal — or by putting a few
lumps of charcoal into the water in which it
is boiled,
,1075.
Q. Why do these things destroy the
frfint of meat ?
25
290 FERMENTATION AND PUTREFACTION.
A. Because they combine Avith the putre^
tent particles, and neutralize their offensive
taste and smell.
1076.
Q. Why does stagnant water pvtrefy?
A. Because leaves, plants, insects, etc.,
are decomposed in it.
1077.
Q. Why is stagnant water full of vjorms,
eels, etc?
A. Because numberless insects lay their
eggs in the leaves and plants floating on the
surface ; these eggs are soon hatched, and
produce swarms of worms, eels, and in-
sects
1078.
Q. Why is flowing water free from these
impurities ?
A. 1st. — Because the motion of running
water prevents fermentation ;
2nd. — It dissolves the putrid substancei
which happen to fall into it : and
3rd — It casts on the bank (by its cur»
rviut) such substances as it cannot dissolve.
1079.
Q. Birds, after they are killed, keep
longer in their feathers, tlian when they ai^
plucked. Why is tliis
PUTREFACTION.
291
A. Because the feathers prevent the air
or damp from getting so readily to the bird,
to produce decay.
1080.
Q. Why does unseasoned wood decay much
raore rapidly than wood well seasoned ?
A. Because the albumen which the sap
contains produces a species of fermenta-
tion ; during which the cellulin and lig-
neous matter of the wood are turned into
carbonic acid and water.
Albumen," a substance resembling the white of an egg.
"Cellulin," the substance which composes the cells of wood, as wax
composes the cells of a honey comb.
*' Ligneous matter," or vegetable fibre, is the hard or woody part of
wood.
1081.
Q. Why is wood placed in a stream of
running water to season it ?
A. Because the running water washes
away the sap ; and thus prevents fermenta-'
lion and decay.
1082.
Q. Why will solutions of salts prevent
the decay of wood steeped therein?
A. Because the salts unite with the
albumen of the sap, coagulate it, and prevent
foraientation.
292 COMPONENTS OF THE ANIMAL BODY.
CHAP. Ill —COMPONENTS OF THE ANfMAL
BODY.
1083.
Q. What is albumen ?
A. Tlie serum, or fluid portion of the
blood, (which, after exposure to the air, is
separated from the more solid part) the
vitreous and crystalline humors of the eye, the
hrain, spinal marrow, and nerves, all contain
albumen.
It exists most abundantly, and in its
purest natural state, in the white of an egg ;
from whence it derives its name {album ovi)
which is the Latin for the white of an egg.
1084.
Q. Why will milk burn very easily, when
boiled ; water will not do so ; explain this?
A. 1st. — Because milk contains solid or-
ganic substances, capable of burning; which
water does not ; and
2nd. — Because the heat of the fire coagu-
lates the albumen of the milk, which falls 1c
the bottom, and adheres to the boiler.
1035.
Q. Why are lamb and veal more tcndei
than beef and mutton ?
A. Because they contain more albumen,
and less muscular fibre.
Aibumen is a substance like the white of an egg
COMPONENTS OF THE ANI^UL BODY. 293
10B6.
Q. Why do lamb and veal taint more quick-
ly than beef and mutton ?
A. Because they contain a large quantit}^
of albumen, which is very liable to putrefac-
tion.
1087.
Q. Why is meat tough which has been
boiled too long ?
A. Because the albumen becomes hard like
the white of a hard boiled egg.
The best way of boiling meat to make it tender, is thus : Pat yo jr joint
in very brisk boilinidly through the lungs in contact
with it. Running acts upon the capillary
vessels as a pair of bellows on a common ^r^.
1124.
Q. Why does inhaling air rapidly make,
the body feel warm ?
A. Because more oxygen is introduced into
the body. In consequence of which, the
combustion of the blood is more rapid — the
blood itself more heated — and every part of
the body is made warmer.
1125.
Q. How does the combination of oxygen
with the blood produce animal heat ?
A. The principal element of the blood is
carbon ; and this carbon (combining with
the oxygen of the air inhaled) produces car-
bonic acid gas, in the same way as burning
fuel.
1126.
Q. What becomes of the nitrogen of the
air, after the oxygen enters the blood ?
A. It is thrown out from the lungs im
changed, by the act of breathing; to be
again mixed with oxygen and converted into
common air.
1127.
Q. Can you explain how we breathe ?
304
ANIMAL HEAT.
A. By a muscular action^ we make an en
larged space in the chest; the pressure of the
external atmosphere forces air into this
space, so as to fill it. By a second muscular
fiction the lungs are compressed, and the air
forced out and escapes. The air whicl)
escapes is chiefly nitrogen.
1128.
Q. Why does the vitiated air (after the
oxygen has been absorbed) come out of the
mouthy and not sink into the stomach ?
A. Because a mechanical provision is
made in the upper part of the windpipe and
gullet for this purpose.
N. B. The lungs are a holloiv, spungy mass, capable of confining air,
and of being dilated by it. They are so situated in the thorax (or chest,)
that tlie air must ent^r into ihem, whenever the cavities of the thorax are
enlarged. The process of breathing is performed thus : When we inhale,
the thorax {or chest) is expanded ; in consequence of which, a vacuum is
formed round the lungs^ and heavy external air instantly enters (through
the mouth and throat) to supply this vacuum.
When we exhale, the thorax contracts again ; in consequence of which,
it can no longer contain the same quantity o( air as it did before; and some
of it is necessarily expelled. When this expulsion of air takes place, the
lun&:s and muscular fibres of the wind-pipe and gullet contract in order to
assist the process.
1129.
Q. If (both in combustion and respira-
tion) the oxygen of the air is consumed, and
the nitrogen rejected — ^Why are not the pro*
portions of the air destroyed ?
A. Because the under surface of vegetable
leaves (during the day) gives out oxygen ;
ANIMAL HEAT.
305
and thus restores to the air the very ele-
ment of which it has been deprived.
1130.
Q. Whence do leaves obtain the oxygen
whicL they exhale ?
A. From the carbonic acid absorbed by
the roots from the soil, and carried to the
leaves by the rising sap.
N. B. Carbonic acid (it must be remembered) is a compound of carbon
and oxygen.
1131.
Q. How do plants contrive to absorb car-
bonic acid from the soil ?
A. It rises (by capillary attraction)
through the small fibrous roots, after it has
been dissolved in the soil by water.
1132.
Q. If leaves throw off the oxygen of the
carbonic acid, what becomes of the carbon.
A. It is retained to give firmness and
solidity to the plant itself.
1133.
Q. Show how God has made animal life
dei)endent on that of vegetables ?
A. Animals require oxygen to keep them
alive, and draw it from the air by inspira-
tion : The under surface of leaves gives otii
oxygen ; and thus supplies the air with the
very gas required for the use of animals.
26*
306
ANIMAL HEAT.
1134.
Q. Show how God has made vegetable lile
dependent on that of animal.
A. Plants require carbonic acid, which is
tlmr principal food ; and all animals exhale
(ho same gas from their lungs. Thus plants
supply animals with oxygen, and aiimols
supply plants with carbonic acid.
SECTION I. FOOD,
1135.
Q. What is fuel of the body ?
A. Food is the fuel of the body. The
carbon of the food, mixing with the oxygen
of the air, evolves heat, in the same way
that a fire or candle does.
1136.
Q. How is food converted into blood ?
A. After it is swallowed, it is dissolved
in the stomach into a grey pulp, called
Chyme ; it then passes into the intestines,
and is converted by the "bile" into a milky
substance, called chvle.
1137.
Q. What becomes of the milky substance
called chyle ?
A. It is absorbed b}^ the vessels called
^'lacteals,^^ and poured into the veins on the
kft side of the neck.
FOOD.
307
1138.
Q , Wliat becomes of the chyle, aftei it is
poured into the veins ?
A. It mingles with the bloody and is itself
converted into blood also,
1139.
Q. How does the oxygen we inhale mingle
with the blood ?
A. The oxygen of the air mingles with
the blood in the lungs, and converts it into
a bright red color.
1140
Q. How does oxygen convert the color of
blood into a bright red ?
A. The coloring matter of the blood is
formed by very minute globules floating in
it ; the oxygen (uniting with the coats oj
these globules) makes them milky — and the
dark coloring matter of the blood (seen
through this milky coat) appears of a bright
red.
Exp. — If you put some dark venous blood into a milky ^lass, and hold it
up towards the light, it will appear of a bright florid color like artenal
blood.
1141.
Q. What color is the blood before it is
oxidized in the lungs ?
A. A dark purple. The oxygen turns it
to a blight red.
Oxidized, that is, impregnated with oxygen.
308
ANBIAL HEAT.
1142.
Q. Why are persons so pale, who live iu
dose rooms and cities?
A . Because the blood derives its redness
from the oxygen of the air inhaled ; but, as
the air in close rooms and cities is not fresh,
it is deficient in oxygen, and cannot turn the
biOod to a beautiful bright red.
1143.
Q. Why are persons, who live in the open
air and in the country, of a ruddy com
plexion ?
A. Because they inhale fresh air which
has its full proportion of oxygen ; and the
blood derives its bright red color from the
oxygen of the air inhaled.
1144.
Q. Why is not the air in cities so fresh as
that in the country ?
A. Because it is impregnated with the
breath of its numerous inhabitants, the odor
of its sewers, the smoke of its fires, and many
other impurities.
1145.
Q. Why do we feel lazy and averse to
activity in very hot weather?
A. 1st. — Because muscular activity in-
FOOD.
309
creases the heat of the body, by quickening
the respiration; and
2nd. — The food we eat in hot weather
(not being greasy) naturally abates our dry
sire for bodily activity.
1146
Q. Why are the Esquimaux so passion-
ately fond of train oil and whole blubber ?
A. Because oil and blubber contain large
quantities of carbon and hydrogen, which are
exceedingly combustible ; and, as these
people live in climates of intense cold, the
heat of their bodies is increased by the
greasy nature of their food.
1147.
Q. Why do we like strong meat and greasy
food when the weather is very cold ?
A. Because strong meat and grease con-
tain large portions of carbon and hydrogen ;
which, (when burned in the blood) produce
a larger amount of heat than any other kind
of food.
1148.
Q. Why do persons eat more food in cold
weather than in hot ?
A. Because the body requires more fuel
in cold weather to keep up the same amount of
mimal heat; and as we put more coals on a
SIO
ANIMAL HEAT.
fire on a cold day, to keep our room warm ,
so we eat more food on a cold day, to keep
our body warm
1149.
Q Why do we like fruits and vegetables
most in hot weather ?
A. Because they contain less hydrogen
and carbon than meat ; and, therefore, pro-
duce both less blood, and blood of a less com
hustiblc nature.
1150.
Q. Why do we feel a dislike to strong
meat and greasy food in very hot weather ?
A. Because strong meat and grease con-
tain so much carbon and hydrogen, that they
would make us intensely hot; we therefore,
instinctively refuse them in hot weather.
1151.
Q. Why do the inhabitants of tropical
countries live chiefly upon rice and fruit ?
A. Because rice and fruit (by digestion)
are m^ainly converted into water; and hy
tooling the blood) prevent the tropical heat
from feeling so oppressive.
1152.
Q. Why is the^ blood of a less combus-
tible nature, if we live chiefly upon fruits
and vegetables?
HUNGER.
311
A. Because fruits and vegetables supply
die blood with a very large amount of wa-
ter; which is not combustible, like the car-
hon and hydrogen of strong meat.
1153.
Q. How do fruits and vegetables cool the
hlood^
A. 1st. — They diminish the amount of
carbon and hydrogen in the blocxJ, which are
the chief causes of animal heat; and
2nd. — They supply the blood with a
large amount of water, which exudes through
the skiUy and leaves the body cool.
SECTION II. HUNGER,
1154.
Q. Why does cold produce hunger ?
A. 1st. — Because the air contains more
oxygen in cold weather; and, therefore,
fires burn more fiercely, and animal combustion
is more rapid ; and
2nd. — As we are more active in cold
w Bather, our increased respiration acts like
a pair of bellows on the capillary combus-
tion
1155.
Q. AVhy does rapid digestion produce a
-^.raving appetite?
312
ANIMAL HEAT,
A. This is a wise providence to keep our
bodies in health ; they give notice (by hun-
ger) that the capillary fires need replenishing,
m order that the body itself may not be
consumed
1156.
Q. Why do we feel a desire for activity
in cold weather.
A. 1st. — Because activity increases the
warmth of the body, by fanning the combus-
tion of the blood ; and
2nd. — The strong food we eat creates a
desire for muscular exertion.
1157.
Q. Why does reading aloud make us feel
hungry ?
A. Because it increases respiration; and
as more oxygen is introduced into the lungs,
our food- fuel is more rapidly consumed.
1158.
Q. Why do we feel less hungry in the
night than in the day ?
A. Because we breathe more slowly during
sleep ; therefore, less oxygen is introduced
into the kmgs, to consume our food- fuel.
1159.
Q. Why does hard work produce hunger ?
A. Because it produces quicker rcspira-
HUNGER.
313
hon; by which means, a larger amount of
oxygen is introduced into the lungs^ and tho
capillary combustion increased. Hunger is the
no ice (given by our body) to remind us
t\
pHed with strong food, this desire for mus-
cular action ceases, and the person grow/?
slothful.
1163.
Q. Why does singing make us hungry?
A. Because it increases respiration; and,
as more oxygen is introduced into the lungs.
our food-fuel is more rapidly consumed.
1164.
Q. Why are the ill-fed mstinctively averse
to cleanliness?
A. Because cleanliness increases hunger^
which they cannot allay by food.
1165.
Q. Why does a man shrink when starved?
A. Because the capillary fires feed upon
the human body; wheli they are not sup-
plied with food-fuel. A starved man
shrinks, just as a fire does, when it is not siip-
plied ^vith fuel.
SLEEP
315
1166.
Q. When a man is starved what parts of
the body go first ?
A. First the fat, because it is the most
combustible ; then the muscles ; last of all
the brain; and then the man dies, like a
tandle luhich is burnt out.
1167.
Q. Why does want of sufficient nourish-
ment often produce madness?
A. Because after the fat and muscles of
the body have been consumed by animal
combustion, the brain is next attacked; and
(unless the patient dies) madness ensues.
CHAP, v.— SLEEP.
1168.
Q What is sleep ?
A. Sleep is the rest of the brain and ner-
vous system.
1169.
Q. Why have dreamers no power of judg-
ment or reason ?
A. Because the ^^cerebrum^^ (oi front of
the brain) is inactive and at rest.
1170.
Q. Why can we not seey when we are
asleep with our eyes open ?
316 SLEEP.
A. Because the ''retina of the eye'^ is
inactive and at rest.
A 1171.
Q. Why can we not hear in sleep ?
A. Because the nerve of hearing (seatoil
within the tympanum of the ear) is at rest.
1172.
Q. Why can we not feel when we ar(i
nmeep ?
A. Because the ends of the nerves (called
papillse) situated in the skin, are inactive
and at rest.
1173,
Q. Why can wo not taste when we are
adeep ?
A. Because the nerves at the end of the
tongue (called papillae) are inactive and at
rest.
1174.
Q. Why have persons in sleep no will of
CHAP. II.— WINDS.
1244.
Q. What is wind?
A. Wind is air in motion.
1245.
Q What puts the air in motion, so as to
produce wind?
A. The principal causes are the valuations
of heat and cold, produced by the succession
of day and night, and of the four seasons.
1246.
Q. What is the cause of wind ?
A. The sun heats the earth, and the earth
heats the air resting upon it ; as the warm
air ascends, the void is filled up by a rush
of cold air to the place; and this rush of air
we call wind.
1247.
Q. Does the wind always blow ?
A. Yes ; there is always some motion in
the air ; but the violence of the motion is
perpetually varying.
1248.
Q. Does the rotation of the earth upon
its axis effect the motion of the air ?
A. Yes, in two ways. 1st. — As the earth
moves round its axis, the thin moveable air
5^ left somewhat behind : and, therefore,
WINDS.
337
seems (to a stationary object) to be blowing
in the opposite direction to the eai th's mo-
tion ; and
2nd. — As the earth revolves, different
portions of its surface are continually pass-
ing under the vertical rays of the sun.
1249.
Q. When are the rays of the sim called
*^ vertical raysV^
A. When the sun is in a direct line above
any place, his rays are said to be "vertical*^
to that place.
1250.
Q. Illustrate the manner in which the
earth's surface passes under the vertical sub
A. Suppose the brass meridian of a globe
to represent the vertical rays of the sun ;
as you turn the globe round, different parts
of it will pass under the brass rim, in con-
stant succession.
1251.
Q. Why is it noon-day to the place over
which the sun is vertical ?
A. Because the sun is half-way between
rising and setting to that place.
1252.
Q. Show how \h\s rotation i he earth
effects the rtir?
29
WINDS.
A. If we suppose the brass meridian to
be the vertical sun, the whole column of air
beneath will be heated by the noon-day rayp;
that part w^hich the sun has left, will be-
come gradually colder and colder ; and that
part to which the sun is approaching^ will
grow constantly warmer and loarmer.
1253.
Q. Then there are three qualities of air
about this spot ?
A. Yes ; the air over the place which
has passed the meridian, is cooling; the air
under the vertical sun is the hottest ; and the
air which is over the place ahout to pass un-
der the meridian, is increasing in heat.
See fi§r. 1. The column A (which the sun has passed) is cooling — B is
ander the vertical sun ; and C is increasing in heat
1254.
Q. Does air expand by heat as well as
water ?
A. It does ; and this expansion is the
eause of winds.
1255.
Q. How does this variety in the heat of
air produce wind ?
A. The air always seeks to preserve an
equilibrium ; so cold air rushes into the void
made by the upward current of the ivarm air,
839
1256.
Q. Why does not the wuid always blow
me way, following the direction of the sun 1
A. Because the direction of the wind is
gubject to perpetual interruptions from hills ^
and valleys^ deserts ^ seas, etc.
1257
Q. How can hills and mountains alter the
course of the wind ?
A. Suppose a wind (blowing from the
north) comes to a mountain ; as it cannot
pass through it, it must either rush hack again,
or fly off at one side, (as a marble, when it
strikes against a ivalL)
125a
Q. Do mountains affect the wind in any
other way ?
A Yes ; many mountains are capped with
snoio, and the wartn air is condensed, when it
comes in contact with them ; but so soon
as the temperature of the wind is changed, its
direc t 'on may be changed also. {See Fig. 1 )
PIG 1.— THB SUN.
340
WINDS.
Suppose A, B, C to be three columns of air. A, the column of air wriicn u
tooling down ; B, the column to which the sun is vertical; and C, the
column which is to be heated next. In this case the cold air of A, will rush
towards B C ; because the air of B and C is hotter than A. But, suppose
now C to be a snow-capped mountain : As the hot air of B reaches C, it ia
chilled ; and (being now colder than the air behind) it rushes back again
towards A, instead of following the sun.
1259.
Q. How can the ocean affect the direction
of the wind ?
A. When the ocean rolls beneath the
vertical sun, the water is not made so hot as
the land; in consequence of which, the ge-
neral direction of the wind is directed from
tracts of ocean towards tracts of land.
1260.
Q. Why is not the water of the sea made
so uot by the vertical sun, as the surface of
the land?
A. 1st, — Because the evaporation of the
sea is greater than that of the land ;
2nd. — The constant motion of the water
prevents the increase of temperature at the
surface ;
3rd. — The rays of the sun strike into the
water ; in consequence of which, the im-
mediate surface is much less affected ; and
4th. — Water is a bad conductor of heat.
1261.
Q. Why does the evaporation of the sea
prevent its surface from being heated by the
vertical sun ?
WINDS.
A. Because its heat is uhsorhed in the ge-
neration of vapor and carried off into the air
1262.
Q. W[\y does the motion of the sea pre-
vent its surface from being heated by the
vertical sun ?
A. Because each portion rolls away, as
soon as it becomes heated, and is succeeded
bj aiiotlur ; and this constant motion pre-
vents the sur face of the sea from being more
heated than the water helovj the surface.
1263.
Q. Why are those winds, which blow
over large continents, or tracts of land, gene
rally dry ?
A. Because, in their passage, they absorb
very little water, as they do not blow over
large oceans.
1264.
Q. Why do our hands and lips chap in
frosty and windy weather ?
A. 1st. — Because the wind or frost ab-
sorbs the moisture from the surface of the
skin ; and
2nd. — The action of wind or frost pio-
duces a kind of inflammation on the skin.
1265.
Q. Do clouds affect the ivind?
S42
WINDS.
A. Yes. As passing clouds screen tlic
direct heat of the sun from the earth, they
diminish the rarefaction of the air also; and
this is another cause why neither the strength
iior direction of the wind is uniform.
1266.
Q. Would the wind blow regularly from
east to west^ if these obstructions were re-
moved
A. Without doubt. If the whole earth
were covered with water, the winds would
always follow the sun, and blow uniformly
in one direction.
1267.
Q. Do winds ever blow regularly ?
A. Yes; in those parts of the world
which present a large surface of w^ater, as
in the Atlantic and Pacific oceans.
SECTION I. TRADE WINDS.
1268.
Q. What are the winds which blow over
the Atlantic and Pacific oceans, called ?
A. They are called "Trade Winds.''
1269.
Q Why are they called ''Trade Winds?''
A. Because they are very convenient to
merchants, who have to cross the ocean.
TRADE WINDS.
343
iiuismuch as they always blo^v in one di-
rection.
1270.
Q. In what direction do the trade winds
blow ?
A That in the northern hemisphere blows
from the north-east; that in the southern
hemisphere from the south-east.
1271.
Q. Why do they not blow from the full
north and south ?
A Because currents of air flowing from
the poles ^ give them an easterly direction.
This effect is due in some measure to the rotation of the earth o'l its
1272.
Q. What is the cause of these currents of
air from the poles to the equator ?
A. The air about the equator constantly
ascends, in consequence of being rarefied by
the heat of the sun ; as the hot equatorial
air ascends, cold air from the north and
south flows towards the equator, to restore
the equilibrium.
1273.
Q. Is there an upper as well as a lower
current in the atmosphere ?
A. Yes ; the upper current of rarefied air
is from the equator to fie poles ; where it is
341
WLNTjS.
conden»*5ed — and then returns again to the
equator, forming the lower current.
1274.
Q, These lower currents (from the poles to
I he equator) have an ^(^^fcr/y tendency. Ex-
plain the cause of this ?
A All the atmosphere revolves with the
mrth ; but when a current of air from the
poles flows towards the equator, it comes to
a part of the earth's surface which is moving
faster than itself in consequence of which,
it is left behind, and thus produces the effect
of a current moving in the opposite di-
rection.
Thus, to a person in a carriage, the hedges and trees seem to be running
in an opposite direction.
As the circumference of the earth at the equator is much larger than the
circumference of ihe earth at the poles, therefore, every spot of the earth'g
equatorial surface must move much faster than the corresponding one at
the poles.
N. B. As the earth revolves on its axis from west to east, therefore, the
Bir which is carried with it will seem to blow fro7n the weat : As, how-
ever, the current of air from the poles seems to blow in the opposite di*
rection, it will seem to blow from the east (or to be an easterly wind.)
1275.
Q. By what means are the north-east and
fiouth-east trade loinds produced ?
A . By a combination of the two moticms
of the 'polar currents ; which produces the
hitermediate directions of the north-east and
wuth-east.
TRADE WINDS
345
1276.
Q Are both these motions of the polaf
i^urrents real ?
A. No. The motion from the east to
west is only apparent. As the earth re-
volves from west to east^ the air carried with
it will be a west wind ; but the polar cm^
rents seem to h\ow in the opposite dirpxtion.
merely because they have not acquired the
same velocity.
1277.
Q. Do trade winds blow from the north-
east and south-east a// ih^ year round?
A. Yes, in the open sea; that is, in the
Atlantic and Pacific Oceans, for about SO""
each side of the equator.
1278.
Q. What do the north-easterly and south-
easterly trade winds produce when they
meet near the equator ?
A. A region of calms in which thick
foggy air prevails, with sudden showers and
thunder-storms.
1279.
Q. Is this region of calms ^x^c? in its po-
sition ?
A. No; it shifts its place according* to
the sun's distance, and position in regard to
S46
WINDS.
the equator ; being sometimes entirely to tlw
north of the equator, and occasionally reach-
ing as far as 2"* south of it.
1280.
Q. Do the trade winds blow uniformly
from north-east and south-east in the Indian
Ocean?
A. No; nor yet in those parts of the
Atlantic and Pacific which verge on the con-
tinents.
1281.
Q. How do the trade winds in the Indian
Ocean blow ?
A. From April to October, a south-west
wind prevails ; but from October to April,
a north-east.
SECTION 11. MONSOONS.
1282.
Q. What are these periodical currents of
air (which affect the neighborhood of the
Arabian, Indian, and Chinese Seas) called
A . They are called Monsoons.
1283.
Q. How far do the limits of the Monsoons
extend ?
A. They extend from the African shore
to tjie longitude of New Guinea; and are
MONSOONS.
347
felt northward as far as the parallel of lati
tude, which crosses the Loochoo Isles.
The Loochoo Isles are about 24° norlh latitude, and 130° east longitude.
1284.
Q. Are the monsoons as powerful as tlie
trade winds ?
A. They are far more so, and veiy often
amount to violent gales.
1285.
Q. Why do not the trade winds in the
Indian Ocean blow south-west from April to
October?
A. Because the air of Arabia, Persia, In-
dia, and China, is so rarefied by the enor-
mous heat of their summer sun, that the
cold air from the south rushes towards these
countries, across the equator, (during these
six months y) and produces a south-west wind.
1286
Q. To what distance does this south-vjest
wind prevail?
A. From 3° south of the equator, to the
shores of the Arabian, Indian, and Chinese
Seas
1287.
Q. Why do the trade winds (in the hu
dian Ocean) blow north-east from October to
April ?
A. Because the southern part oj the torrid
348
zone is most heated, when the sun has left
the northern side of the equator for the
southern; and the cold air from the north
(rushing towards the southern tropic) is di-
verted into the direction of north-east, where
it continues for the other six months of the
}^ear
1288.
Q. Why are the monsoons more useful to
the mariner than the fixed trade winds?
A. Because the mariner is able to avail
himself of these periodic changes, to go in
one direction during one half of the year,
and to return in the opposite direction during
the other half.
1289,
Q. How is the change of the monsoons
marked ?
A. By an interval of alternating calms
and storms.
1290.
Q. Show the goodness and wisdom of God
in the constant tendency of air to equili-
brium ?
A. If the torrid zone were not tempered
by cold air from the polar regions, it would
become so hot, that no human being could
. endure it. If (on the other hand) the polar
reo;ions were never vv^'^rmed by hot air from
MONSOONS.
the torrid zone^ they would soon become in-
sufferably cold.
1291.
Q In what other way does the mingling
of the polar and equatorial atmosphere act
hnieficially ?
A. In the equatorial regions, the great
abundance of vegetable life is productive of a
very large amount of oxygen; in the colde''
regions, artificial fires and dense masses of
animal life, produce large quantities of car-
bonic acid. The mingling of the polar and
equatorial atmosphere assists in supplying
each of these regions with the very gas in
which it would be otherwise deficient.
1292.
Q. Why does the expansion of air cause
wind ?
A. The heat of the sun heats that part
of the surface of the earth over which it is
vertical ; the heat of the earth thus ac-
quired by absorption, is imparted to the
lowest stratum of air, which, becoming ex-
panded, rises and gives place to another,
and in this manner an ascending current is
established.
The colder and heavier air rushes in from
the colder regions north and south to fill
30
350
WINDS.
the vacuum tlius occasioned, thus producing
wind.
" Stratu7n^'^ layer. The lowest stratum of air, is that portion of an
which is in cuntact with the surface of the earth.
1293.
Q. How does the mingling of the poker
and equatorial atmosphere serve to su]:)ply
each region ^vith the gas it most requires ?
A. The plants of the equatorial regions re-
quire carbonic acid; — The animals of the
colder regions require oxygen ; — The cur-
rents of air from the Poles carry carbonic acid
to the equatorial plants ; and the currents
of air from the Equator carry oxygen to the
animals which abound nearer the Poles.
1294.
Q. Why does vjind dry damp linen ?
A. Because dry wind (like a dry sponge)
imbibes the particles of vapor from the sur-
face of the linen, as fast as they are formed.
1295.
Q. Why are the west winds in the At-
lantic States generally dry ?
A. Because they come over large tracts of
land, and therefore, absorb very little water;
and being thirsty, they readily imbibe
moisture from the air and clouds, and there-
fore bring dry weather.
N. B. The remarks about the winds in this work, do not apply to thi
*Vf;stern Statee, particularly Texas and California,
MONSOONS.
351
1296.
Q. Why is the noiih wind generally coM?
A. Because it comes from the polar re-
gions, over mountains of snow and seas of
ice.
1297.
Q. Why are north winds generally drij?
A. Because they come from colder re-
p;ions, and being warmed by the heat of our
climate, absorb moisture from every thing
they touch; in consequence of which, they
are generally dry.
1298.
Q. Why are south winds generally warm?
A. Because they come over countries
vv^armer than our own, where they are
much heated.
1299.
Q. Why are winds which blow over a
vast body of water generally rainy?
A. Because they come laden with vapor :
if, therefore, they meet with the least chul^
8ome of the vapor is deposited as rain.
1300.
Q. Why is the rising sun in summer,
sometimes accompanied with a bi^eeze ?
A. Because the heat of the rising sun
stops the radiation of heat from the earth,
and warms its surface.
352
WINDS.
1301.
Q. How does this warmth produce a
breeze?
A. The air (resting on the earth's siir-
iace) being warmed by contact ascends^ and
colder air rushing in to fill up the void, pro-
duces the morning breeze.
1302.
Q. Why is there often an evening breeze
during the summer months ?
A. Because the earth radiates heat at sun-
set and the air is rapidly cooled down by
contact ; this condensation causes a motion
in the air, called the evening breeze.
1303.
Q. Why are tropical islands subject to a
sea breeze every morning ; (that is, a breeze
blowing from the sea to the land ?)
A. Because solar rays are unable to heat
the surface of the sea, as they do the earth;
therefore, the air resting on the sea is less
heated than the air resting on the earth; and
the colder sea air blows inland to restoie
the equilibrium.
1304.
Q. Wliy is a fine clear day sometimes
m^ercast in a few minutes ?
A. Because some sudden change of tev^
MONSOONS.
353
perature has condensed the vapor of the air
into clouds.
1305.
Q. Why are clouds sometimes dissipated
vory suddenly ?
A. Because some dri/ loind (blo^v^ing over
the clouds) imbibes their moisture, and carrier
t off in invisible vapor.
1306.
Q. Why does wind sometimes bring rain
and sometimes fine weather ?
A. If the wind be colder than the clouds,
it will condense their vapor into rain ; but
if the wind is warmer than the clouds, it will
dissolve them and cause them to disappear
1307.
Q. Why is a land breeze unhealthy ?
A. Because it is frequently laden with
exhalations from putrefying animal and vege-
table substances.
1308.
Q. Why is a sea breeze fresh and healthy?
A. Because it passes over the sea, and
is not laden with noxious exhalations.
It is partieularlj' healthy^ thereforp, to walk on the sea-beach before ten
7 clock in the morning ; hut unhealthy after sun- set
1309
Q. What is the cause of a sea breeze ?
A. When the land is more heated by (h^
30^
354
WINDS.
sun than the sea is, the land air becomes
hotter than that over the sea; in conse-
quence of which, the cooler sea air glides
inland to restore the equilibrium.
1310.
Q. Why does a sea breeze feel cool ?
A. Because the sun cannot make the
surface of the sea so hot as the land; there-
fore, the air which blows from the sea is
cooler than the air of the land.
1311.
Q. Why are tropical islands subject to a
land breeze every evening, (that is a breeze
blowing from the land towards the sea ?)
A. Because the surface of the land cools
down faster (after sun-set) than the surface
of the sea: in consequence of which, the
air of the cold land is condensed — sinks down
— and spreads itself into the warmer sea
air — causing the land breeze.
1312.
Q. Why is the land breeze cool?
A. Because the surface of the land is
cooled at sun-set quicker than the surface of
the sea ; therefore, seamen feel the air fi f uri
the land to be chill.
1313.
Q Explain th ^ cause of sea leaves ?
MONSOONS.
355
A. The wind (acting on the suiface of
the sea) piles up ridges of water ^ leaving be-
hind an indentation: as the water on all
sides rushes to fill up this indentation, the
disturbance spreads on all sides, and billow
rolls after billow.
1314
Q. Why does wind generally feel cold ?
A. Because a constantly changing surface
comes in contact with our body, to draw
off its heat.
1315.
Q. How fast does wind travel ?
A. A gentle breeze goes at about the
rate of five miles an hour. A high wind
from twenty to sixty. A hurricane from
eighty to one hundred miles an hour.
1316.
Q. How is the velocity of winds ascer-
tained ?
A. By observing the velocity of the
clouds ; and by an instrument for the pur-
pose, called an Anemometer.
Pronounce An-e-mom-'-e-ter. From two Greelc words avsr^aT ajiemoa
(wind,) and i^erpov metron (a measure.) This term is applied more fre-
quently to an instrument which measures the force of wind.
1317.
Q. How is the velocity of the clouds
curtained ?
S56
CLOUDS.
A. By obsenang the speed of their slia-
(low along the ground ; which is found (in
a high w^ind) to vary from twenty to sixty
miles an hour.
CHAP. III.— CLOUDS.
1318.
Q What are clouds ?
A. Moisture evaporated from the earthy
and again partially condensed in the upper
regions of the air.
1319.
Q. What is the difference between a fog
and a cloud ?
A. Clouds and fogs differ only in one re-
fipect. Clouds are elevated above our heads :
but fogs come in contact with the surface of
the earth.
1320.
Q. Why are clouds higher on a fine day?
A. Because they are lighter and more
b^ioi/ant.
1321.
Q. Why are clouds lighter on a fine day?
A. 1st. — Because the vapor of the clouds
IS less condensed : and
2nd. — The m itself (on a fine day) re-
to ins much ol its vapor in an invisible form
CLOUDS. 35
1322.
Q. Wliy do clouds float so readily in the
air?
A. Because they are composed of Vhry
minute globules (called vesicles;) which (be-
ing lighter than air) float like soap bubbles.
1323.
Q. Are all clouds alike ?
A. No. They vary greatly in density ^
height J and color.
1324.
Q. What is the chief cause of fog and
clouds ?
A. The changes of the wind.
Many local circumstances also favor the formation of clouds.
1325.
Q. How can the changes of the wind affect
the clouds ?
A. If a cold current of wind blows sud-
denly over any region, it condenses the in-
visible vapor of the air into cloud or rain:
but, if a warm current of wind blows over
any region, it disperses the clouds, by absorb*
mg their vapor.
132S.
Q. What countries are the most cloudy ?
A. Those where the winds are most vana*
ble, as Great Britain.
358
CLOUDS-
1327.
Q. Wliat countries are the least cloudy ?
A. Those where the winds are least vw^ich
hie as Egypt.
1328.
Q. What distance are the clouds from the
earth ?
A. Some tkin^ light clouds are elevated
above the highest mountain- top; some heavy
ones touch the steeples, trees, and even the
earth ; but the average height is between
07ie and two miles.
N. B. Streaky, curling clouds, like hair, are often five or six milefl
high.
1329.
Q. What clouds are the lowest?
A.. Those which are the most highly elec*
trifled; lightning clouds are rarely more
than about seven hundred yards above the
ground ; and often actually touch the earth
with one of their edges.
1339.
Q. What is the size of the clouds ?
A. Some clouds are tiomty square mdes in
surface, and above a mile in thickness; while
others are only a feia yards or inches.
1331
Q. How can persons ascertain the thick*
M.ess of a cloud ?
CLOUDS.
359
A. As the tops of high mountains are
generally above the clouds, travellers may
pass quite through them into a clear blue fir-
mament ; when the clouds will be seen he-
math their feet.
1332.
Q. What produces the great variety in the
shape of the clouds ?
A. Three things: 1st. — The cau^e and
manner of their formation :
2nd. — Their electrical condition ; and
3rd. — Their relations to currents of wind.
■ 333
Q. How can electricity affect the shape of
*ilouds ?
A. If one cloud be full oj ekctriaty and
another not, they will be attracted to each
other, and either coalesce — diminish m size
— or vanish altogether.
1334.
Q. What clouds assume the most fantastic
tdiapes ?
A, Those that are the most hignly electrt-
fied.
1335.
Q. What effect have winds on the shape
of clouds?
A. They ?iome times absorb them entirely
3G0
CLOUDS.
sometimes increase their volume and density ^
and sometimes change the position of their
parts.
1336.
Q. How can winds absorb clouds altogether?
A Warm, dry loinds will convert the sub-
stance of clouds into invisible vapor, which
they will carry away in their own current.
1337.
Q. How can winds increase the bulk and
density of clouds ?
A. Cold currents of wind will condense
the invisible vapor of the air, and add it to the
clouds with which they come in contact.
1338.
Q. How can winds change the shape of
clouds, by altering the position of their
parts
A. Clouds are so voluble and light, that
every breath of wind changes the position
of their vesicles or bubbles.
1339.
Q. What are the general colors of the
(huds ?
A. White and gray, when the sun is above
the horizon ; but red, orange, and yellow, at
mn-rise and sun-set.
The blue sJcy is not cloud at all.
CLOUDS.
361
1340.
Q. Why are the last clouds of evening
generally of a red tinge ?
A. Because r^cZ rays (being the least re-
j '-angible of all) are the la^t to disappear.
Suppose P, A, to be the red rays ; P, B, the yellow ; P, C, the bhie. If
the earth turns in the direction of P, A, D, it is quite manifest that a spec*
tator will see A, (the red rays,) some time after P, C, and P, B, have passed
froir sight.
Q, What is meant by being ^^less refran-
gible V
A. Being less able to be bent. Blue and
yellow rays are more easily bent below the
horizon by the resistance of the air ; but red
rays are not so much bent down; and, there-
fore, we see them later in the evening.
As at A, in jRg. 2.
1342.
Q. Why are morning clouds generally of a
red tinge ?
PIG. 2.
1341.
81
362
CLOUDS.
A. Because red rays are the least refran-
gible of all ; and not being hent so much as
blue and yellow rays, we see them sooner
of a morning.
Thus (figr. 2,) if the earth turned in the direction of D, A, P, a specta^
fit D, would see A, (the red rays) long before he saw P, B, ard P, C
1343.
Q, Why is not the color of clouds always
alike ?
A. Because their size^ density ^ and situa-
tion^ in regard to the sun, are perpetually
varying ; so that sometimes one color is re-
flected and sometimes another.
1344.
Q. What regulates the motion of the
clouds?
A. Principally the 2/;mc?5; but sometimes
electricity will influence their motion also.
1345.
Q. How do you know that clouds move
by other influences besides wind ?
A. Because (in calm weather) we often
see small clouds meeting each other from op-
posite directions.
1346.
Q. How do you know that electricity af.
fects the motion of the clouds ?
A. Because clouds often meet from oppo
site directions; and, having discharged their
CLOUDS.
363
opposite electricities into each other, vanuh
altogether,
1347.
Q What are the uses of clouds ?
A. 1st. — They act as screens, to arrest th <
radiation of heat from the earth ;
2nd. — They temper the heat of the sun\%
rays ; and
3rd. — They are the great store-houses of
rain.
Radiation of heat," that is, the escape of heat, when no conductor
carries it away.
1348.
Q. Why is wind said to blow up the clouds?
A. Because a dry, warm wind (which has
traveled over seas) having absorbed a large
quantity of moisture, deposits some of it in
the visible form of clouds, as soon as it reaches
a colder region of air.
1349.
Q. Why does wind sometimes drive away
the clouds ?
A. Because it has traveled over dry
dimes or thirsty deserts, and become so dry,
that it absorbs vapor from the clouds, and
causes them to disappear.
1350.
Q. What is the cause of a red sun-set ?
A. The vapor of the air, not being
364
CLOUDS.
actually condensed into clouds, but only on thu
point of being condensed.
1351.
Q. Why is a red sun-set an indication of
a fine day to-morrow ?
A. Because the vapors of the earth aro
not condensed into clouds, by the cold of sun-
set. Our Lord referred to this prognostic
in the following* words : When it is even-
ing ye say it will be fair weather, for the
sky is red/' (Matt. xvi. 2.)
1352.
Q. What is the cause of a coppery yellow
sun-set?
A. The vapor of the air being actually
condensed into clouds.
1353.
Q. Why do vapors {not actually condensed)
refract red rays, while condensed vapor re-
fracts yellow ?
A. Because the beams of light meet with
very little resistance ; in consequence of
which, those rays are bent down to the eye,
which require the least refraction, such as
red.
See fig 2, where it is evident that the red ray, P, A, is less bent than the
yellow ani blue rays, P, B, P, C.
1354.
Q Why do condensed vapors refract ycU
CLOUDS.
865
ioiv rajs, whereas, vapors not actually con-
densed refract red ?
A. Because the beams of light meet with
ffiore resistance from the condensed vapor ;
in consequence of which, those rays are
bent down to the eye, which are more re
fr acted than the red, such as yellow.
See fig. 2, where it is evident, that the yellow ray, P, B, is more ben
than the red ray, P, A.
1355.
Q. Why is a yellow sun-set an indication
of wet ?
A. Because it shows that the vapors of
the air are already condensed into clouds; rain,
therefore, may be shortly expected.
1356.
Q. What is the cause of a red sun-rise ?
A. Vapor in the upper region of the air
just on the point of being condensed.
1357.
Q. Why is a red and lowering sky at sun-
rise an indication of a wet day ?
A. Because the higher regions of the aii
ore laden with vapor on the very point of
condensation, which the rising sun cannot
disperse. Hence our Lord's observation,
''In the morning ye say, it will be foul
weather to-day, for the sky is red and low-
ering." (Matt. xvT. 3.)
366
CLOUDS.
1358.
Q. Why is a graij morning an indication
of a fine day ?
A. Because only the air contiguous to the
earth is damp and full of vapor. There are
10 vapors in the higher regions of the air,
o bend down to the eye even the red ray^
of any beam of light.
1359.
Q. What difference (in the state of the
air) is required, to make a gray and red sun-
rise 1
A. In a gray sun-rise, only that portion
of air contiguous to the earth is filled with va-
por; all the rest is clear and dry. But in
a red sun-rise the air in the upper regions is
so full of vapor, that the rising sun cannot
disperse it.
1360.
Q. Why is a gray sun-set an indication of
wet?
A. Because it shows that the air on the
surface of the earth is very damp at sun-set ;
which is a plain proof that the air is satu-
rated with vapor; in consequence of which,
wet may be soon expected ; hence the pro*
verb —
Evening red and morning gray,
VVill set the traveler on his way ;
But evening gray and morning red,
Will bring down rain upon his head "
CLOUDS,
367
1361.
Q. What is meant by an aurora borealis,
or northern h'ght ?
A. Luminous clouds in the north of the ski/
at night time. Sometimes streaks of bluef
purple, green, red, etc,, and sometimes
flashes of light, are seen.
1362.
Q. What is the cause of the aurora bo*
realis^ or northern light ?
A. Electricity in the higher regions of the
atmosphere.
1363.
Q. Why does a haze round the sun indi-
cate rain ?
A. Because the haze is caused by very
fine rain falling in the upper regions of the air;
when this is the case, a rain of five or six
hours^ duration may be expected.
1364.
Q. Why is a halo round the moon a sure
indication of rain?
A. Because it is caused by fine rain fall-
ing in the upper regions of the air. The
larger the halo, the nearer the rain-clouds^
and the sooner may rain be expected.
1365.
Q. Why do we feel almost suffocated in a
hot cloudy night ?
368
CLOUDS.
A Because the heat of the earth cannot
escape into the upper region of the air ; hut
is pent in by the clouds, and confined to the
surface of the earth.
1366.
Q Why do we feel sprightly in a clear,
bright night ?
A. Because the heat of the earth can
readily escape into the upper regions of the
air, and is not confined and pent in hy thick
clouds.
1367.
Q. Why do we feel depressed in spirits on
a wety murky day?
A. 1st. — Because the air is laden with
vapor, and has (proportionally) less oxygen.
2nd. — The air being lighter than usual,
does not balance the air in our body ; and
3rd. — Mr'ist air has a tendency to depress
the nervous system.
1368.
Q. What is meant by the ^^air balancing
the air in our body
A. The human body contains air of a
given densit}^ ; if, therefore, we ascend into
"^arer air, or descend into denser, the balance
is destroyed, and ive feel oppressed.
MODIFICATION OF CLOUDS. 369
1369
Q. Why do we feel oppressed, if the air
around is not of the same density as that in
our body ?
A. Because if the air be more dense than
our body, it will produce a feeling of op^
pression; if it be less dense, the air in our
body will produce a feeling of distension.
SECTION I. MODIFICATION OF CLOUDS.
1370.
Q. Into how many classes are the differ-
ent sorts of clouds generally divided?
A. Into three classes : — viz. Simple, In-
termediate, and Compound.
1371.
Q. How are simple clouds sub-divided ?
A. Into 1. — Cirrus; 2. — Cumulus; and
3. — Stratus clouds.
1372.
Q. What sort of clouds are called cirrus?
A. Clouds like fibres, loose hair, or thin
streaks, are called " cirrus clouds.'^
1373.
Q. Why are these clouds called cirrus ?
A. From the Latin word ciirus a lock
of hair, or curl.") Cirrus clouds are the
most elevated of all.
• 870
CLOUDS.
1374.
Q. What do cirrus clouds portend?
A. When the streamers point upwards ^
the clouds are fallings and rain is at hand :
hut when the streamers point downwards,
drought may be expected.
1375.
Q. What sort of clouds are called cum-
ulus ?
A. Cumulus clouds are lumps, like great
sugar-loaves — volumes of smoke — or mountains
hwering over mountains.
1376.
Q. Why are these monster masses called
cumulus clouds ?
A. From the Latin word cumulus ('^a
mass or pile.'')
1377.
Q. Wliat do cumulus clouds foreshow ?
A. When these piles of cloud are fleecy^
and sail against the wind, they indicate rain ,
but when their outline is very hard, and
they come up with the wind, they foretell
fine weather.
Cumulus clouds should be smaller towards evening than they are al
noon. If they increase in size at sun-set, a thunder-slorrr. may be expected
ill the night.
1378.
Q. What sort of clouds are called stratus?
MODIFICATION OF CLOUDS. 371
A. Creeping mists, especially prevalent in
a summer's evening: these clouds rise at
sun-set in low, damp places; and are always
nearer the earth than any other sort of
cloud.
1379.
Q. Why are these mists called stratus
clouds ?
A. Fiom the Latin word stratus laid
low," or " that which lies low.")
1380
Q. What produces cirrus clouds?
A. Moisture in a visible form, deposited
in the higher regions of the atmosphere by
ascending currents of heated air.
1381.
Q. What produces cumulus clouds ?
A. Masses of visible vapor passing from
the places where they were formed, to other
places where they are about to be either
lissolved, or deposited as falling rain.
1382.
Q. What produces stratus clouds .
A. Beds of visible moisture, formed by
some chilling effects, acting along the di-
'^ect surface of thp rarth.
372 CLOUDS
1383.
Q. How are the intermediate clouds sub*
divided ?
A. Into two sorts. 1. — The Cirro- Cu-
mulus ; and 2. — The Cirro-Stratus.
1384.
Q What are cirro-cumulus clouds ?
A. Cirro-cumulus clouds are cirrus clouds
springing from a massy centre; or heavy
masses, edged with long streaks generally
called mares' tails.
A system of small round clouds may be called cirro-cumulus.
1385.
Q. What do cirro-cumulus clouds gene-
rally forebode?
A. Continued drought, or hot, dry wea«
ther.
1386.
Q. What are cirro-stratus clouds ?
A. They compose what is generally
called a "mackerel sky.'' This class of
clouds invariably indicates rain and wind ;
hence the proverb —
Mackerel's scales and mares' tails.
Make lofty ships to carry low sails."
1387.
Q. What produces cirro-cumulus clouds ?
A. Cumulus clouds dissolving away into
MODIFICATION OF CLOUDS.
373
cirim produce the intermediate class, called
tf'rrO'Cumuhis.
1388.
Q What produces cirro-stratus clouds ?
A, Cirrus clouds accumulating into demei
UJ asses produce the intermediate class, called
[iiro'Stratm.
1389.
Q. How are compound clouds sub- divided?
A. Compound clouds are also subdivided
into two sorts. 1. — The Cumulo-Stratus;
and 2. — The Nimbus clouds.
1390.
Q. What is meant by cumulo-stratns
clouds ?
A. Those clouds which assume all sorts
of gigantic forms ; such as vast towers and
rocks — huge whales and dragons — scenes
of battle — and cloudy giants. This class
of clouds is the most romantic and strange
of all.
1391.
Q. What do the cumulo-stratus clouds
foretell?
A. A change of weather ; either from fine
to rain, or from rain to fine.
1392.
Q. What are nimbus clouds?
32
371
CLOUDS.
A. All clouds from which rain falls. —
Nimbus is the Latin word for '^clouds which
bring a storm,
1393.
Q. By what particular character may the
nimbus (or rain-cloud) be at once distin-
giiished.
A« By the want of a defined outline : its
edge is gradually shaded oflF from the deep
gray mass into transparency,
1394.
Q. What appearance takes place in the
clouds at the approach of rain ?
A. The cumulus cloud becomes stationary,
and cirrus streaks settle upon it, forming cu-
mulo-stratus clouds; black at first, but after-
wards of a gray color.
1395.
Q. Why do clouds gather round mountain
tops?
A. Because the air (being chilled by the
cold mountain tops) deposites its vapor
there in a visible form or cloud.
SECTION II. DEW.
1396.
Q. What is dew?
A. Dew is the vapor of the air cmdenscd
DEW. 375
by coming in contact with bodies colder
than itself.
1397.
Q. Why is the ground sometimes covered
with d^w?
A. Because the surface of the earth (at
sun-set) is made so very cold by radiation,
that the warm vapor of the air is chilled by
contact and condensed into dew.
1398
Q. What is the difference between dew
and rain ?
A. In dew^ the condensation is made near
the earth's surface.
In rain the drops fall from a considerable
height.
1399.
Q. What is the cause of both dew and
ram ?
A. Cold condensing the vapor of the air
when near the point of saturation.
1400.
Q. Why do mist and fog vanish at sim*
rise ?
A. Because the condensed particles are
again changed into invisible vapor by the
heat of the sun.
376
CLOUDS.
1401.
Q, Why is the earth made colder than
the air after the sun has set ?
A. Because the earth radiates heat very
freely, but the air does not; in consequence
of which, the earth is often five or ten de-
grees colder than the air, (after sun-set;)
although it was much warmer than the air
during the whole day.
1402.
Q. Why is the earth warmer than the air
during the day.
A. Because the earth absorbs solar heat
very freely, but the air does not ; in conse-
quence of which, it is often many degrees
warmer than the air, during the day.
1403.
Q. Why is the surface of the ground
colder in a fine clear night than in a cloud?/
one ?
A. Because, on a fine, clear star-light
night, heat radiates from the earth freely, and
is lost in open space ; but on a dull night,
the clouds arrest the process of radiation.
1404.
Q. Why is dew deposited only on a fine,
clear night?
A. Because the surface of the ground ra^
Hates heat most Ji f^ehj on a fine night ; and
DEW.
377
(being cooled down by this loss of heat)
chills the vapor of the air into dew.
1405.
Q. Why does abundance of dew in the
morning, indicate that the day will be fine?
A. Because dew is never deposited in
Jnll cloudy weather, but only in very clear
calm nights; when the cold currents of air
are not mixed with those of a warmer
temperature.
1406.
Q. Why is there no dew on a dull, cloudi/
night ?
A. Because the clouds arrest the radiation
of heat from the earth; and (as the heat can-
not freely escape) the surface is not suffi-
ciently cooled down to chill the vapor of the
air into dew.
1407.
Q. Why is a cloudy night warmer than a
fine one ?
A. Because the clouds prevent the radia-
tion of heat from the earth ; in consequence
of which the surface of the earth remains
warmer.
1408
Q. Why is dew most abundant in situa-
tions most exposed ?
378
CLOUDS.
A. Because the radiation of heat is ni>t
arrested by houses, trees, hedges, or any
otlier thin2f.
1409.
Q. Why is there scarcely any dew under
« shadj^ tree ?
A. 1st. — Because the thick foliage of a
tree arrests the radiation of heat from the
earth: and
2nd. — A leafy tree radiates some of its
own heat towards the earth; in consequence
of which, the ground underneath a tree is
not sufficiently cooled down to chill the va-
por of the air into dew.
1410.
Q. Why is there never much dew at the
^oot of walls and hedges ?
A. 1st. — Because they act as screens, to
arrest the radiation of heat from the earth ;
and
2nd. — They themselves radiate some por-
tion of heat towards the earth ; in conse-
quence of which, the ground at the foot of
walls and hedges is not sufficiently cooUd
down, to chill the vapor of the air into
dew.
1411.
Q. Dud very rarely flies by night. Wliy
•8 this ?
DEW.
379
A. 1st. — ^Because the dews of night
moisten the dust and prevent its rising into
the air : and
2nd. — As the surface of the earth is
colder than the air after sun-set, the cur-
rent of the wind will incline downward ;
and tend rather to press the dust down than
to buoy it up.
1412.
Q. Why is there no dew after a windy
night ?
A. 1st. — Because the wind evaporates the
moisture, as fast as it is deposited ; and
2nd. — It disturbs the radiation of heat ;
and thus diminishes the deposition of dew
1413.
Q. Why are volleys and hollows often
thickly covered with dew, although they
are sheltered.
A. Because the surrounding hills pre-
vent the repose of air from being disturbed;
but do not overhang and screen the valleys
sufficiently to arrest their radiation.
1414.
Q. Wliy does dew fall more abundantly
en some things than on others ?
A. Because some things radiate boat
380
CLOUDS.
more freely than others ; and, therefore, be-
come much cooler in the night.
1415.
Q. Why are things which radiate heat
most freely always the most thickly covered
with dewl
A. Because the vapor of the air is chilled
into deio, the moment it comes in contact
with them.
1416
Q. What kind of things radiate heat most
freely ?
A. Grass, wood, and the leaves of plants,
radiate heat very freely ; but polished
metal, smooth stones, and w^oolen cloth,
part with their heat very tardily.
1417.
Q. Do the leaves of all plants radiate heat
equally well ?
A. No. Rough, woolly leaves (like those
of a holly-hock) radiate heat much more
freely than the hard, smooth, polished leaves,
of a common laurel.
1418
Show the wisdom of God in making
grass, the leaves of trees, and all vegetables,
excellent radiators of heat ?
A. As vegetables require much moisture,
%xvSl would often perish without a plentiful
DEW.
381
deposit of dew, God wisely made them to
radiate heat freely , so as to chill the vapor
(which touches them) into dew,
1419.
Q. Will polished metals smooth stones, and
woolen cloth, readily collect dev. ?
A. No. While grass and leaves of plants
are completely drenched with dew ; a piece of
polished metals or of woolen cloth (lying on the
same spot,) will be almost dry.
1420.
Q. Why -wonldi polished metal and woolen
cloth be dry, while grass and leaves are
drenched with dew ?
A. Because the polished metal and woolen
cloth part with their heat so slowly y that the
vapor of the air is not chilled into dew as it
passes over them.
1421.
Q. Why is a gravel walk almost dry when
a grass plat is covered thick with dew ?
A. Because grass is a good radiator, and
throws off its heat very freely; but gravel is
a very had radiator, and parts with its heat
very slowly.
1422.
Q. Is that the reason why grass is satv
rated with devj, and the gravel is not ?
382
CLOUDS.
A. Yes. When the vapor of warm air
comes in contact with the cold grass, it is
instantly chilled into dew ; but it is not so
freely condensed as it passes over gravel, be-
cause gravel is not so cold as the grass.
1423.
Q. Why does dew rarely fall upon hard
rocks and barren lands ?
A. Because rocks and barren lands are
so compact and hard, that they can neither
absorb nor radiate much heat ; and (as their
temperature varies but very little) very little
dew distils upon them.
1424.
Q. Why does dew fall more abundantly
on cultivated soils than on barren lands ?
A. Because cultivated soils (being loose
and porous) very freely radiate by night the
heat which they absorbed by day ; in con-
sequence of which they are much cooled down,
and plentifully condense the vapor of the
passing air into dew.
1425.
Q. Show the wisdom of God in this
arrangement ?
A. Every plant and inch of land, which
needs the moisture of dew, is adapted to coU
DEW.
383
led it ; but not a single drop is wasted wheie
its refreshing moisture is not required.
1426
Q. Show the wisdom in having polished
metal and woolen cloth bad radiators of heat?
A. If polished metal collected dew as
easily as grass, it could never be kept dry and
free from rust. Again, if woolen garments
collected dew as readily as the leaves of
trees, we should be often soaking wet, and
subject to constant colds.
1427.
Q. Show how this affords a beautiful illus-
tration of Gideon's miracle, recorded in the
book of Judges, vi. 37, 38?
A. The fleece of wool (which is a very bad
radiator of heat) was soaking wet with dew,
when the grass (which is a most excellent
radiator) was quite dry.
1428.
Q. Was this not contrary to the laws of
nature ?
k. Yes ; and was, therefore, a plain de--
^onstration of the power of God, who could
thus change the very nature of things at his
will
1429.
Q. Why do our clothes feel damp after walk
ing in a fine evening in spring or autumn ?
384
CLOUDS.
A. Because the vapor (condensed by the
cold earth) lights upon them like dew.
1430
Q. When is dew most copiously distilled ?
A. After a hot day in summer or autumn,
especially if the wind blow over a body of
water.
1431.
Q. Why is dew distilled most copiously
after a hot day ?
A. Because the surface of the hot earth
radiates heat very freely at sun-set, and (be-
ing made much colder than the air) chills the
passing vapor and condenses it into dew.
1432.
Q. Why is there less dew when the wind
blows across the land; than when it blows
over a body of water ?
A. Because the winds which blow across
the land are dry and arid ; but those which
cross the water are moist and full of vapor.
1433.
Q. How does the dryness of the wind pre-
vent dew-falls?
A. As winds which blow over the land
are very dry, they imbibe the moisture
of the ^lir ; in consequence of which, there
\8 very little left to be condensed into dm.
DEW.
385
1434.
Q. How does the moisture of the wind
promote dew-falls;
A. As winds which blow over water are
rit mated with vapor, they require very little
1 eduction of heat to cause a copious deposition
uj dew.
1435.
Q. Does not atr radiate heat, as well as
the earth and its various plants ?
A. No. The air never radiates heat; nor
is the air made hot by the rays of the sun.
1436.
Q. Why is evening dew injurious to health ?
A. Because it is always laden with nox-
ious exhalations from earth; especially in
marshy countries.
1437.
Q. Is honey 'dew a similar thing to dew 1
A. No. Honey-dew is a sweet liquid shed
by a very small insect (called the aphis) and
deposited in autumn on the under surface
of favorite leaves.
1438.
Q. Does honey-d.ew injure leaves, or do
them good ?
A. It injures them very much, by filling
^he pores with a thick, clammy liquid ; in
386
CLOUDS.
consequence of which, the leaf can neither
transpire nor absorb its needful food.
1439.
Q. What effect has honey-dew upon tlie
appearance of a leaf?
A. After a little time, the leaf (being
smothered and starved) begins to turn a dingy
yellow.
1440.
Q. Are not ants very fond df honey-dew ?
A. Yes ; and crawl up the loftiest trees
in order to obtain it.
1441.
Q. Why is a dew-drop round ?
A. Because every part of it is equally ba*
lanced; and, therefore, there is no cause why
one part of the drop should be further from
the centre than another.
1442.
Q. Why is the dew-drop (on a broad leaf)
sometimes flattened?
A. Because two or more drops of dew roll
together, and make one large spheroid (or
flattened drop.)
1443.
Q. Why will dew-drops roll ''bout cabbage*
plants, poppies, etc., without wetting the
s^iu'face ?
DEW.
387
A. Because the leaves of cabbages and
poppies are covered with a very fine waxen
powder ^ over which the dew-drop rolls with-
out wetting the surface, as a drop of rain
would over dust.
1444.
Q. Why does not a drop of rain wet the
dmt over which it rolls ?
A. Because dust has no affinity for water,
and, therefore, repels it.
144'
Q. Why does not the dew-drop wet the
powder of the cabbage-plant ?
A. Because the fine powder which covers
the cabbage leaves has no affinity for water,
and, therefore, repels it.
1446.
Q. Why will dew-drops roll over a rose,
etc., without wetting the petals?
A. Because the leaves of a rose contain
an essential oil, which has no affinity for wa*
ter, and, therefore, repels it.
M47.
Q. Why can swans and ducks dive under
water without being wetted ?
A. Because their feathers are covered
with an oily secretion, which has no affinity
for water and, therefore, repels it.
3P8
CLOUDS.
SECTION III. RAIN, SNOW, IIAIL.
1448.
Q. Wliat is Rain ?
A. Rain is the vapor of the clouds or air,
condensed and precipitated to the earth.
1449.
Q. Does rain-water possess any fertilizing
properties, besides that of mere moisture ?
A. Yes ; rain-water contains an abun-
dance of carbonic acid, and a small quantity
of ammonia ; to which much of its fertilizing
power may be attributed.
Ammonia is a compound of nitrogen and hydrogen. Common hartshorn
is only ammonia and water.
1450.
Q. Why are there more rainy days from
September to March, than from March to
September ?
A. Because the temperature of the air is
constantly decreasing, and its capacity for
holding vapor decreases also ; in conse-
quence of which, it is frequently obliged to
part with some of its vapor in rain.
1451.
Q. In what part of the world does rain
fall most abundantly ?
A. Near the equator ; and the quantity of
rain decreases as we approach the poles.
Be it remembered, that there are fewer rainy days^ although more mm
%ctunlly falls during the wet season of the equator, than falls in tueWe
ffioi ihs at a)»y other part of the globe.
RAIN, SNOW HAIL.
389
1452.
Q. Why is there less rain frora March to
SeptfMber, than from September to March ?
A. Because the temperature of the air is
const aiitly increasing; on which account its
capacity for holding vapor is on the increase
end very little is precipitated as rain.
1453.
Q. Why does rain fall in drops?
A. Because the vapory particles in theii
descent attract each other ; and those which
are sufficiently near unites and form into
drops.
1454.
Q. Why does not the cold of night always
cause rain ?
A. Because the air is not always near
saturation ; and unless this be the case, it
will be able to hold its vapor in solution,
even after it is condensed by the chilly
night.
1455.
Q. Why does a passing cloud often drop
rain ?
A. Because the cloud (traveling about on
tlie wind) comes into contact with something
that chills it; and its vapor being condensed
falls to the earth as rain.
33*
390 CLOUDS
1456.
Q. Why are rain-drops sometimes much
larger than at other times ?
A. Because the rain-cloud is floating near
the earth ; when this is the case the drops
are large, because such a cloud is much
jiore dense than one more elevated.
The size of the rain-drop is also increased according to the rapidity with
which the vapcrs are condensed.
1457.
Q. Does not wind sometimes increase the
nze of rain-drops ?
A. Yes ; by blowing two or more drops
into one.
1458.
Q. Why do clonds fall in rainy weather ?
A. 1st. — Because they are heavy with
abundant vapor ; and
2nd. — The density of the air being di-
minished ^ is less able to buoy the clouds up.
1459.
Q. How do you know that the density of
the air is diminished in rainy weather ?
A. Because the mercury of a barometer
falls.
1460.
Q. Why is min-water more fertiliziig than
pvmp'Vjater ?
RAIN, SNOW, HAIL.
391
A. Isfc. — Because it contains more car-
bonic acid ; and
2nd.- -It contains also a small quantity
of ammonia, with which it supplies the
young plants.
It '.s probable that the ammonia of rain-water i& merely that whick
asr^pes from putrefying animal matters, beaten back by the force of th6
shower.
1461
Q. Why does rain purify the air ?
A. 1st. — Because it heats down the noxious
exhalations collected in the air, and dissolves
them ;
2nd. — It mixes the air of the upper re-
gions with that of the lower regions; and
3rd. — It washes the earth, and sets in mo-
tion the stagnant contents of sewers and
ditches.
1462.
Q. Why are mountainous countries more
rainy than flat ones ?
A. Because the air (striking against the
sides of the mountains) is carried up the in-
clined plane, and brought in contact with the
cold air of the higher regions ; in conse-
quence of which, its vapor is condensed, and
deposited in rain.
1463.
Q. Why does a sponge swell when it is
wetted ?
392
CLOUDS.
A. Because the water penetrates the poreh
of the sponge by capillary attraction, and
drives the particles further from each other ;
in consequence of which, the hulk of the
sponge is greatly increased.
1464.
Q. Why do fiddle-strings snap in wet wea-
ther?
A. Because the moisture of the air (pene-
trating the string) causes it to swell; and (as
the cord thickens) its tension is increased, and
the string snaps.
1465
Q. Why does paper pucker when it is
wetted?
A. Because the moisture (penetrating the
paper) drives its particles further apart ; and
(as the moisture is absorbed unequally by
the paper) some parts are more enlarged
than others ; in consequence of which, the
paper blisters or puckers.
1466.
Q. Why do candles and lamps spirt, when
ram is at hand ?
A. Because the air is filled with vapor
which penetrates the wick; where (being
fo) med into steam) it expands suddenl}', nnd
]U'-)dnces a little explosion.
RAIN, SNOW, HAIL.
393
1467.
Q. In which part of the day does the most
rain fall ?
A. More rain falls by night than by day;
because the cold night condenses the air^ and
diminishes its capacity for holding vapor m
solution.
1468.
Q. Does more rain fall in summer cr m
lointer?
A. There are more rainy days from Sep-
tember to March ; but heavier rains between
March and September.
1469.
Q. What beneficial effect has rain upon
fallen leaves ?
A. It hastens the putrefaction of the fallen
leaves ; and this makes the earth fertile.
1470.
Q. Why do swallows fly low, when rain
is at hand ?
A. Because the insects (of which they are
in pursuit) have fled from the cold, upper re-
* onions of the air, to the warm air near the
earth ; and, as their food is low, the swal-
lows fly low.
1471.
Q Why do these insects seek the lowei
894
CLOUDS.
regions of the air in wet weather, more than
in fine weather ?
A. Because (in wet weather) the upper
regions of the air are colder than th
lower; and, as insects enjoy warmth, they
seek it near the earth.
1472.
Q. Why do sea-gulls fly about the sea in
fine weather ?
A, Because they live upon the fishes, which
are found near the surface of the sea in fine
weather.
1473.
Q. Why may we expect stormy rains,
when sea-gulls assemble on the land ?
A. Because the fishes (on which they
live) leave the surface of the sea in stormy
weather, and are beyond the reach of the
sea-gulls; in consequence of which, they are
obliged to feed on the worms and larvce.
which are driven out of the ground at such
times.
*^Larvx,^^ little grubs and caterpillars
14 74.
Q. Why do petrels fly to the sea during a ^
Btorm ?
A. Because they live upon sea insects,
which are always to be found in abundance?
abmit the spray of swelling waves.
RAIN, SNOW, HAIL. 395
tH. II. Petrels are birds of the duck-kind, which live in the open iea
They run on the top of the waves, and are called Petrels, or rather Peter
els, from "St. Peier," in allusion to his walking on the sea, to go
fetuB.
1475
Q. What is snow ?
A. The condensed vapor of the air frozen
and precipitated to the earth.
1476.
Q. AVhat is the cause of snow ?
A. When the air is nearly saturated with
vapor, and condensed by a current of air
below freezing point, some of the vapor is
condensed, and frozen into snow.
A few years ago, some fishermen (who wintered at Nova Zembla,)
after ihey had been shut up in a hut for several days, opened the window,
and the cold external air rushing in, instantly condensed the air of the hut,
ind its vapor fell on the floor in a shower of snow.
1477.
Q. Why does snow fall in winter time ?
A. Because the sun's rays are too oblique
to heat the surface of the earth ; and (as
the earth has no heat to radiate into the air)
the air is very cold.
1478.
Q What is the cause of sleet ?
A. When flakes of snow (in their descent)
pass through a bed of air above freezing point,
they partially melt : and fall to the earth aa
half melted snow, or sleet.
1479
Q. What is the use of snow?
396
CLOUDS.
A. To keep the earth warniy and tc
nourish it.
1480.
Q. Does snow keep the earth warm ?
A. Yes, because it is a very had cm-
iudoi ; in consequence of which, when the
earth is covered with snow, its temperature
very rarely descends below freezing point,
even when the air is fifteen or twenty de-
grees colder.
1481.
Q. Why is snow a had conductor of heat
and cold?
A. Because air is confined and entangled
among the crystals ; and air is a very had
conductor : when, therefore, the earth is
covered with snow, it cannot throw off its
heat by radiation.
1482.
Q. Tell me the words of the Psalmist
(cxlvii. 16) respecting snow; and explain
what he means ?
A. The Psalmist says — "The Lord giv-
eth snow like wool;'' and he means, not
only that snow is as white as wool, but that
it is also as warm as wool.
1483.
Q. Why is iiml loarm?
RAIN, SNOW, HAIL.
397
A. Because air is entangled among the
fibres of the wool ; and air is a very had
rondvctor.
1484.
Q Why is snow warm ?
A. Because air is entangled among the
crystals of the snow ; and air is a very bod
conductor.
1485.
Q. Why does snow nourish the earth?
A. Because it supplies moisture contain-
ing carbonic acid; which penetrates slowly
into the soil, and insinuates itself through
every clod, ridge, and furrow.
I486.
Q. Why is there no snow in summer timel
A. Because the heat oj the earth melts it
in its descent, and prevents it from reach-
ing the surface of the earth
1487.
Q. Why are some mountains always covered
with snow ?
A. 1st. — Because the air on a high
mountain is more rarefied ; and rarefied air
retains much heat in a latent state : and
2nd. — Mountain- tops are not surrounhd
by earth, to radiate heat into the air; and,
therefore, tlie snow is not melted in its de-
34
SOS
CLOUDS.
ecent, but falls on the mountain, and lieti
there.
1488.
Q. Why is snow white ?
A. Because it is formed of an infinite
number of very minute crystals and prisms^
which reflect all the colors of the rays of
light from different points ; and these co-
lors, uniting before they meet the eye, cause
snow to appear white.
The same answer applies to salt, loaf-sugar, etc.
1489.
Q. What is hail 1
A. Rain, which has passed in its descent
through some cold bed of air, and has been
frozen into drops of ice.
1490.
Q. What makes one bed of air colder than
another ?
A. It is frequently caused by electricity
unequally distributed in the air.
1491.
Q Why is hail frequently accompanied
^vith thunder and lightning?
A. 1st. — Because the congelation of water
into hail disturbs the electricity of the air ;
and
2nd. — The friction (produced by the fall
of hail) excite.^ it still more.
MIST, FOG, FROST.
1492.
Q. Why does hail fall generally in
mer and autumn?
A. 1st. — Because the air is more highly
dectrified in summer and autumn than j\
^"inter and spring : and
2nd.— The vapors in summer and au-
tumn (being rarefied) ascend to more ele-
vated regions, which are colder than those
nearer the earth.
1493.
Q. What two things are essential to caose
hail ?
A. Two strata of clouds having ofpOcute
electricities, and tivo currents of wind. The
lower cloud (being negative) is the one r/;^-
cipitated in hail.
1494.
Q. When is the vapor of the air or
clouds precipitated in hail, rain, or snow ?
A. When the air is saturated with onpo} ,
and a cold current condenses it ; it is ti:on
no longer able to hold all its vapor in y^Shi
tion, and some of it falls as rain.
SECTION IV. MIST, FOG, FROST.
1495.
Q. What is the cause of mist ^
400
CLOUDS.
A. Currents of air from the water com-
ing in contact with colder land currents.
1496.
Q. Why are the currents of air from the
land colder than those blowing over water ?
A . Because the earth radiates heat after
sun-set, more freely than water, conse^
quently the air which comes in contact with
the land is colder than that which comes in
contact with the water.
1497.
Q. Why are windows often covered with
thick raist^ and the frames wet with stand-
ing water ?
A. Because the temperature of the ex-
ternal air always falls at sun-set, and chills
the windoW'glass with which it comes in
contact.
1498.
Q. How does this account for the mist
and water on a window ?
A. As the warm vapor of the room
touches the cold glass it is chilled and con-
densed into mist ; and the mist (collecting
into drops) rolls down the window-frame in
little streams of water.
1499.
Q Does the glass of a window cool down
MIST, FOG, FROST. 401
more rapidlij than the air of the room
itself?
A. Yes ; because the air is kept ivarm hy
fires, and by the animal heat of the people
in the room; in consequence of which, the
ftir of a room suffers very little diminution
rf heat from the setting of the sun.
1500.
Q. Whence arises the vapor of a room?
A. 1st. — The very air of the room con-
tains vapor ;
2nd. — The breath and insensible perspira-
tion of the inmates increase this vapor; and
3rd. — Hot dinners, the steam of tea, and
so on, increase it still more.
1501.
Q. What is meant by " the insensible per-
spiration
A. From every part of the human body,
an insensible and invisible perspiration issues
all night and day; not only in the hot
weather of summer, but also in the coldest
day of winter.
1502.
Q. If the perspiration be both inse/inble
and invisible how is it known that tJicre is
%ny such perspiration
If you put your naked arm ii.io n
34*
402
CLOUDS.
dean, dry glass tube, the perspiration will
condense on the glass like mist.
1503.
Q. Why are carriage windows very soon
Cuvered with thick mist?
A. Because the warm vapor of the car-
riage is condensed by the cold glass, and
covers it with a thick mist.
1504.
Q. Why is the glass window cold enough
to condense the vapor of the carriage ?
A. Because the i?iside of a carriage is
much warmer than the outside; and the
glass window is made cold by contact with
the external air.
1505.
Q. Where does the warm vapor of the
carriage come from ?
A. The warm breath and insensible per-
spiration of the persons riding, load the air
of the carriage with warm vapor.
1506.
Q. What is the cause of the pretty frost-
work, seen on bed-room windows in winter
time ?
A. The breath and insensible perspiritton
of the sleeper (coming in contact with the
loo-cold window,) are frozen by the cold
MIST, FOG, FROST.
403
glass, aud form those beautiful appearances
Been in our bed-rooms on a winter morn-
ing.
1507.
Q. Why is the glass of a window colder
than the walls of a room ?
A. Because glass is so excellent a radia^
tor^ that it parts with its heat more rapidly
than the walls do.
1508.
0. Why is a tumbler of cold water made
quite dull with mist, when brought into a
room full of people.
A. Because the hot vapor of the room is
condensed upon the cold tumbler, with which
it comes in contact ; and changes its invi-
sible and gaseous form into that of a thick
mist.
1509.
Q. Why is a glass made quite dull by
laying a hot hand upon it ?
A. Because the insensible perspiration of
the hot hand is condensed upon the cold
glass, and made perceptible.
1510.
Q. Why are wine-glasses made quite duU^
when they are brought into a room full of
compini/?
CLOUDS.
A. Because the hot vapor of the room
(coming in contact with the cold wine-
glasses) is condensed upon them, and covers^
tliem with vapor, like dew.
1511.
Q Why does this misty appearance go
after a little time ?
A. Because the glass becomes of the
isame temperature as the air of the room ;
and will no longer chill the vapor which
touches it, and condense it into mist.
1512.
Q. Why is a vnne-glass (which has been
brought out of a cellar into the air) covered
with a thick mist in summer time ?
A. Because the vapor of the hot air is
condensed into a thick mist by contact with
the cold glass.
1513.
Q. Why does breathing on a glass make
it quite dull ?
A. Because the hot breath is condensed
by tlie cold glass; and therefore, covers it
with a thick mist.
1514.
Q. Why are the walls of a house covered
with wet in a sudden thaw ?
A Because the walls (being thick) can-
MIST, FOG, FROST.
405
not change their temperature, so fast as the
air; in consequence of which, they retain
their cold after the thaw has set in.
1515.
Q. How does ''retaining their coW^ ac
count for their being so wet?
A. As the vapor of the warm air touches
the cold walls, it is chilled and condensed
into water; which either sticks to the walls
or trickles down in little streams.
1516.
Q. Why does a thick well-built house con*
tj^act more damp of this kind than an ordi
nary one?
A. Because the walls are much thicker ;
and (if the frost has penetrated far into the
bricks) they will be some time before they
are reduced to the same temperature as the
air.
1517.
Q. Why are balusterSy etc., damp after a
thaw?
A Because they are made of some very
close-grained varnished wood, which can-
not change its temperature so fast as the air.
Balusters — corruptly called banisters.
1518.
Q. How does this account for the baluS'
lers being damp?
406
CLOUDS.
A. The vapor of the warm air (coming
in contact with the cold balusters) is chilled
and condensed into water upon them.
1519.
Q. Why is our breath visible in winter and
not in summer?
A. Because the intense cold condenses
our breath into visible vapor ; but in summer
the air is not cold enough to do so.
1520.
Q. Why are our hair and the brim of our
hat often covered with little drops of pearly
dew in winter time ?
A. Because our breath is condensed as
soon as it comes in contact with our cold
hair or hat, and hangs there in little dew-
drops.
1521.
Q. What is the cause of fog ?
A. If the night has been very calm, the
radiation of heat from the earth has been
very abundant; in consequence of whicli,
the air (resting on the earth) has been
{hilled, and its vapor condensed into a thick
mist,
1522.
Q. Why does not the mist become dew?
A, Because the chill of the air is so rapid.
mST, FOG, FROST.
40T
lliat vapor is condensed faster than it can
be deposited; and (covering the earth in a
mist) prevents any further radiation of heat
from the earth.
1523.
Q. When the earth can no longer radiate
heat upwards, does it continue to condense
the vapor of the air ?
A. No; the air (in contact with the earth)
becomes about equal in temperature with the
surface of the earth itself ; for which reason
the mist is not condensed into dew, but re-
mains floating above the earth as a thick
cloud.
1524.
Q. This mist seems to rise higher and
higher, and yet remains quite as dense be-
low as at first. Explain the cause of this ?
A. The air resting on the earth is first
chilled, and chills the air resting on it ; the
air which touches this new layer of mist, be-
ing also condensed, layer is added to layer ;
and thus the mist seems to be rising, when
(in fact) it is only deepening.
1525.
Q. Why do mist and dew vanish, as the
sun rises ?
A. Because the air becomes warmer at
sun -rise, and absorbs the vapor.
408
CLOUDS.
1526.
Q. What is the cause of a London fog ?
A. These fogs (which occur generally in
the winter time) are occasioned thus: — Some
current of air (being suddenly cooled) de-
sands into the warm streets, forcing back the
t^nioke in a mass towards the earth.
1527.
Q. Why are there not fogs every night ?
A. Because the air will always hold in
solution a certain quantity of vapor, (which
varies according to its temperature ;) and,
when the air is not saturated^ it may be
cooled without parting with its vapor.
1528.
Q. When do fogs occur at night ?
A. When the air is saturated with vapor
during the day. When this is the case, it
de|)osits some of its superabundant moisture
in the form of dew or fog as soon as its
capacity for holding vapor is lessened by
the cold night.
1529.
Q. Why is there very often a fog over
marshes and rivers, at night-time ?
A.. Because the air of marshes is al-
most always near saturation; and, there-
fore, the least depression of temperature wiW
MIST, FOG, FROST.
409
compel it to relinquish some of its moisture
in the form of dew or fog.
1530,
Q. Why does vapor sometimes form into
chmdsy and sometimes rest upon the earth
as mist or fog ?
A. This depends on the temperature of
the air. When the surface of the earth is
warmer than the air, the vapor of the earth
(being condensed by the chill air) becomes
mist or fog. But, when the air is warmer
than the earth, the vapor rises through the air^
and becomes cloud.
1531.
Q. Why do hills ^ etc., appear /fl^rg^r in
weather ?
A. Because the air is laden with vapor ^
which causes the rays of light to diverge
more ; in consequence of which, they pro-
duce on the eye larger images of objects.
1532.
Q. Why do trees, etc., in wet weather ap-
pear further off than they really are.
A. Because the fog or mist diminishes the
light reflected from the object ; and as the
object becr^mes more dim, it seems to be fur
fher of,
35
410
CLOUDS,
1533.
Q. WTiat is the difference between a Jfiist
and a fog ?
A. Mist is generally applied to vapors
condensed on marshes, rivers, and lakes.
Fog is generally applied to vapors con-
densed on land; especially if those vapors
are laden with smoke.
1534
Q. What is the reason why condensed
vapor sometimes forms into clouds, and some-
times into fog?
A. If the surface of the earth is hotter
than the air, the vapor of the earth is chilled
by the cold air, and becomes fog; but if the
air is hotter than the earth, the vapor iHses
through the air, and becomes cloud.
1535,
Q. If cold air produces fog, why is it not
foggy on a frosty morning ?
A. 1st. — Because less vapor is formed on
a frosty dar/; and
2nd. — The vapor is frozen upon the
ground, before it can rise from the earth,
a.Tid becomes hoar-frost.
1536.
Q Why are fogs more general in avr
tnmn than in spring ?
MIST, FOG, FROSl. 411
A. The earth in spring is not so hot as it
is in autumn ; in consequence of which, its
vapor is not chilled into fog as it issues into
tlie air.
1537.
Q Why are fogs more common in valleys
lhan on hills ;
A. 1st. — Because valleys contain more
moisture than hills; and
2nd. — They are not exposed to sufficient
wind to dissipate the vapor.
1538.
Q. How does wind dissipate fogs ?
A. Either by blowing them away ; or else
by dissolving them into vapor again.
1539
Q. 'Wh.dii is hoar-frost ?
A. There are two sorts of hoar-frost :
1. — Frozen dew; and 2. — Frozen fog,
1540.
Q. What is the cause of the ground hoa^^ .
frost, or frozen dew ?
A. Very rapid radiation of heat from the
earth ; in consequence of which, the surface
is so cooled down, that it freezes the dew con-
densed upon it.
412
CLOUDS.
1541.
Q Why is hoar-frost seen only after a
very clear night ?
A. Because the earth will not have
thrown off heat enough by radiation to
freeze the vapor condensed upon its surfacej
unless the night was very clear indeed.
1542.
Q. What is the cause of that hoar-frost
which arises from frozen fog ?
A. The thick fog which invested the
earth during the night (being condensed by
the cold frost of early morning,) is congealed
upon every object with which it comes in
contact.
1543.
Q. Why is there little or no hoar-frost
under shrubs and shady trees ?
A. 1st. — Because the leafy top arrests
the process of radiation from the earth ;
2nd. — Shrubs and trees radiate heat to-
wards the earth ; and, therefore, the ground
beneath is never cold enough to congeal the
ittle dew which rests upon it.
Q. Why does hoar-frost very often covet
the ground and trees^ when the water of
rivers is not frozen ?
ICE.
413
A. Because it is not the effect of cold in
the air, but cold on the surface of the earth
(produced by excessive radiation,) which
freezes the dew condensed upon it.
1545.
Q. Why is the hoar-frost upon grass and
vegetables much thicker than that upon lofty
trees ?
A. Because the air (resting* on the surface
of the ground) is much colder after sun-set
than the air higher up ; in consequence of
which, more vapor is condensed and frozen
there.
CHAP. IV.— ICE.
1546.
Q. What is ice ?
A. Frozen water. When the air is re
duced to thirty-two degrees of heat, water
will no longer remain in a fluid state
1547.
Q. Why is solid ice lighter than water ?
A. Because water expands by freezing,
and as the bulk is increased, the gravity must
be less.
Nine cubic inches of water become ten when lit>zen.
1548.
Q. Why do ewers break in a frosty night?
35*
414
ICE.
A. Because the water in them freezes ^
and {expanding by frost) burst the ewers to
make room for its increased volume.
1549
Q Why does it not expand upwards (like
)oiling water,) and run over?
A. Because the surface is frozen first; and
the frozen surface acts as a plug, which is
more difiicult to burst than the porcelain
ewer itself.
1550.
Q. Why do tiles, stones, and rocks often
split in winter
A. Because the moisture in them freezes;
and (expanding by frost) splits the solid mass,
1551.
Q. In winter time, foot-marks and wheeU
ruts are often covered with an icy net-work,
through the interstices of which the soil is
clearly seen ; why does the water freeze in
net-work ?
A. Because it freezes first at the sides of
the foot-prints ; other crystals gradually
shoot across, and would cover the whole
surface, if the earth did not absorb the wa-
ter before it had time to freeze.
1552.
Q. In winter time, these foot-marks and
ICE.
415
wheel-ruts are sometimes covered witii a per-
fect sheet of ice, and not an icy net-work ;
why is this ?
A. Because the air is colder and the earth
harder than in the former case ; in conse^
quence of which, the entire surface of the
foot-print is frozen over before the earth
has had time to absorb the water.
1553.
Q. Why is not the ice solid in these ruts?
— Why is there only a very thin jUm or net-
work of ice ?
A. Because the earth absorbs most of the
water, and leaves only the icy film behind.
1554.
Q. Why do water-pipes frequently bm^st
in frosty weather ?
A. Because the water in them freezes ;
and {expanding by frost) burst the pipes to
make room for its increased volume.
1555.
Q. Does not water expand by heat as well
as by cold ?
A. Yes ; it expands as soon as it is more
than forty- two degrees, till it boils ; after
which time, it flies off in steam. {See Fig. 3 )
416 ICE.
FIG. 3.
Free7ing water, 32®. 212^, boiling watot.
Here A B, measures the bulk of a portion ol water at forty- two dsgree*
It goes on increasing, in bulk to C D, when it boils.
It also goes on increasing in bulk to E F, when it freezes.
1556.
Q. When does water begin to expand from
cold?
A. When it is reduced to forty- two de-
grees. Water is wisely ordained by God to
be an exception to a very general rule — it
contracts till it is reduced to forty-two de-
grees, and then it expands till it freezes.
The general rule is this — That cold condenses and contracts the volume
of nenrlv everything ; but water is not contracted by cold after it freezes,
(which It does at 32®.)
1557.
Q. Why does water expand when it
freezes ?
A. Because it is converted into solid crys-
tals which do not fit so closely as particles of
water do
1558.
Q. Why is the hottora of a river nevei
frozen ?
ICE.
417
A. Because water ascends to the surface,
so soon as it becomes colder than forty-two
degrees ; and, (if it freezes) floats there till
it is melted.
1559.
Q. Show the wisdom of God in this won-
derful exception to a general law 7
A. If ice were heavier than water ^ it would
sink ; and a river would soon become a solid
block of ice, which could never be dissolved.
The general rule is — That all substances beoome heavier houl conden-
iation ; but ice is lighter than water.
1560.
Q. Why does not the ice on the surjace
of a river chill the water beneath and make
it freeze ?
A. 1st. — Because water is a very bad con-
ductor y and is heated or chilled by convection
only;
2nd. — If the ice on the surface were to
communicate its coldness to the water be-
neath, the water beneath would communi-
cate its heat to the ice, and the ice would in-
stantly melt ; and
3rd. — The ice on the surface acts as a
shield, to prevent the cold air from penettat-^
ing through the river, to freeze the water
below the surface.
418
ICE.
1561.
Q. Why does water freeze at the surjact
arst?
A. Because the surface is in contact with
Oie air, and the air carries away its heat.
1562.
Q. Why does the coat of ice grow thicker
and thicker if the frost continues ?
A. Because the heat of the water (imme-
diately below the frozen surface) passes
through the pores of the ice into the cold air.
1563.
Q. Why are not whole rivers frozen (layer
by layer,) till they become solid ice ?
A. Because water is so slow a conductor,
that our frosts never continue long enough to
convert a whole river into a solid mass of
ice.
1564.
Q. Why does not running water freeze so
fast as still water?
A. 1st. — Because the motion of the cur*
rent disturbs the crystals, and prevents their
forming into a continuous surface ; and
2nd. — The heat of the under surface is
communicated to the upper surface by the
•"oiling of the wnier.
ICE*
419
1565.
Q. When running water is frozen, why is
rhe r:e generally very rough?
A. Because little flakes of ice are first
formed and carried down the stream, till they
meet some obstacle to stop them ; other flakes
of ice (impinging against them) are arrested
in like manner ; and the edges of the differ-
ent flakes overlapping each other, make the
surface rough.
1566.
Q. Why do some parts of a river freeze
less than others ?
A. Because springs issue from the bot-
tom ; and (as they bubble upwards) thaw
the ice, or make it thin.
1567.
Q. When persons fall into a river in win-
ter time, why does the water feel remarka-
bly ivarm ?
A. Because the frosty air is at least ten
or twelve degrees colder than the water is.
Tao -Titer below the surface at least 42° ; but the air 32°, or even
less.
1568.
Q. Why is shallovj water frozen more
quickly than deep water ?
A. Because the whole oolume of ^vater
must be cooled to forty-two degrees, before
420
ICE.
he surface can he frozen; and it takes a
longer time to cool down a deep bed of wa-
ter than a shallow one.
1569.
Q. Why is sea-water rarely frozen ?
A. 1st. — Because the mass of water is so
great, that it requires a very long time to
cool the whole volume down to forty-two
degrees.
2nd. — The ebb and flow of the sea inter-
fere with the cooling influence of the air; and
3rd. — Salt water never freezes till the
surface is cooled down twenty-five degrees
below freezing point.
1570.
Q. Why do some lakes rarely (if ever)
freeze ?
A. 1st. — Because they axe very deep ; and
2nd. — Because their water is supplied by
springs, which bubble from the bottom.
1571.
Q. Why does the depth of water retard its
freezing?
A. Because the whole volume of vmter must
be reduced to forty-two degrees, before the
mrface will freeze ; and the deeper the wa-
ter, the longer it will be before the whole
volume is thus reduced.
ICE.
421
1572.
Q. Whj do springs at the bottom of a
lake prevent its freezing ?
A. Because they keep continually send-
ing forth fresh water, which prevents the
lake from being reduced to the necessary
dogree of coldness.
1573.
Q. It is colder in a thaWy than in a frost.
Explain the reason of this ?
A. When frozen water is thawed, it absorbs
heat from the air, etc., to melt the ice ; in
consequence of which, the heat of the air is
greatly reduced.
1574.
Q. It is warmer in a frost than in a thaw.
Explain the reason of this ?
A. When water freezes, it gives out la-
ient heat, in order that it may be converted
into solid ice; and, as much heat is liberated
from the water to the atmosphere, the air
feels warmer.
1575.
Q. Salt dissolves ice. Explain the reason
of this?
A. Water freezes at 32"*, but salt and wa-
ter will r.ot freeze till the air is twenty-fivo
36
422
ICE,
flegrees colder; if, therefore, salt be added
to frozen water, it dissolves it.
Unless the thermometer stands below 7°
1576.
Q. Will any thing dissolve ice except ^a//?
A. Yes ; any acid, such as sulphuric acid,
ftitric acid, etc.
1577.
Q. Why is a mixture of salt and snow
colder than snow itself ?
A. Because salt dissolves the crystals of
snow into a fluid ; and whenever a solid is
converted into a fluid, heat is absorbed^ and
the cold made more intense.
1578.
' Q. Why does frost make the earth crack?
A. Because the water absorbed by the
earth in warm weather, expanding by the
frost, thrusts the particles of earth apart
from each other, and leaves a chink or crack
between.
1579.
Q. Show the wisdom of God in this
arrangement ?
A. These cracks in the earth let in au%
dew, rain, and many gases favorable to
vegetation.
1580.
Q, Why does the earth crumble in spring?
ICE.
428
A. Because the ice of the clods dissolves ;
and the particles of earth (which had been
thrust apart by the frost) being left unsup-
portea, tumble into minute parts, because
their cement of ice is dissolved.
1581.
Q. Why does mortar crumble away in
frost?
A Because it was not dried in the warm
weather; therefore, its moisture freezes, ex
pands, and thrusts the particles of the mor-
tar away from each other ; but as soon as
the frost goes, the water condenses, and leaves
the mortar full of cracks and chinks.
1582.
Q. Why does stucco peel from a wall in
frosty weather
A. Because the stucco was not dried in
the warm weather ; therefore, its moisture
freezes, expands, and thrusts its particles
away from the wall ; but, as soon as the
water condenses again by the thaw, the
stucco (being unsupported) falls by its mm
weight.
1583.
Q. Why cannot bricklayers and plasterers
work in frosty weather ?
A. Because frost expands mortar, and
424
ICE.
causes the bricks and plaster to start from
their position.
1584.
Q. Why do bricklayers cover their work
with straw in spring and autumn ?
A. Because straw is a non-conductor;
and prevents the mortar of their new work
from freezing, during the cold nights of
spring and autumn.
1585.
Q. Why are water pipes often covered
with straw in winter time ?
A. Because straw (being a non-conductor)
-prevents the water of the pipes from freezing,
and the pipes from bursting.
1586.
Q. Why are delicate trees covered with
straiv in winter ?
A. Because straw (being a non-conductor)
prevents the sap of the tree from being
frozen.
1587.
Q. Can water be frozen in any way
sides by frosty weather ?
A. Yes ; in very many ways. For ex-
ample — a bottle of water wrapped in cotton,
and frequently wetted with ether will soon
freeze.
ICE.
425
1588.
Q. Why would water f reeze if the bottle
were kept constantly wetted with ether ?
A. Because evaporation would carry off
the heat of the water, and reduce it to the
freezing point.
1589.
Q. Why does ether freeze under the r^-
ceiver of an air-pump ^ when the air is ex-
hausted?
A. Because evaporation is very greatly in-
creased by the diminution of atmospheric pres-
sure; and the ether freezes by evaporation.
FREEZING MIXTURES.
0 1. If nitre be dissolved in water, the heat of the liquid will be reduced
sixteen degrees.
2. If five ounces of nitre, and five of sal-ammoniac (both finely pow-
dered) be dissolved in nineteen ounces of water, the heat of the liquid will
be reduced forty degrees.
3. If three pounds of snow be added to one pound of salt, the mixture
will fall to 00 (or thirty-two degrees below freezing point.)
The two following are the coldest mixtures yet known —
1. Mix three pounds of muriate of lime with one pound of snow.
2. Mix five pounds of diluted sulphuric acid with four pounds of snow
1590.
Q. Is salt and snow really colder than
enow?
A. Yes, many degrees colder; so that
by dipping your hand into the mixture ^zr^^^,
and into snow afterwards^ the snow will seem
to be comparative!) warm.
36*
426
ICE.
1591.
Q. Can we be made to feel the heat ol
ice or snow ?
A Yes ; into a pint of snow, put half ^^
pint of salt ; then plunge your hand into
the liqaid, it will feel so intensely cold, thai
the snow itself will seem tvarm in compari-
son to it.
#
PART VL
OPTICS.
CHAP. I.— LIGHT
1592.
Q. Wliat is light?
A. Rapid undulations of a fluid called
ether, made sensible to the eye by striking
on the optic nerve.
1593.
Q. How fast does light travel ?
A. Light travels so fast, that it would
go eight times round the earth while a per-
son counts ^^one.^^
1594.
Q. Wha^t is ether?
A. A very subtle fluid, which pervades
and surrounds every thing we see.
N. B. This theory of light is not altogether satisfactory, but has been
retained as the most plausible hitherto projected.
1595.
Q. How can undulations of ether produce
light?
A. As sound is produced by undulations
Oj air striking on the ear, so light is pro
427
428
LIGHT.
duced by undulations of ether striking on
the eye.
1596.
Q. How does combustion make undula-
tions of light ?
A. The atoms of matter (set in motion
by lieat) striking against this ether, produce
undulations in it; as a stone thrown into a
Btream produces undulations in the water.
1597.
Q. Does all light travel equally fast ?
A. Yes ; the light of the sun — the light
of a candle — or the light from houses, trees,
i\xA fields,
1598.
Q. Where does the light of houses, trees
aad fields y come from ?
A. The light of the sun (or of some lamp
or candle) is reflected from their surfaces.
1599.
Q. Why are some surfaces brilliant (like
glass and steel,) and others dull, like lead ?
A. Those surfaces which reflect the most
tight y are the most brilliant; and those which
absorb light are dull.
1600.
Q What is meant by reflecting light 1
LIGHT
429
A. Throwing the rays of light back again
from the surface on which they fall.
1601.
Q. What is meant by absorbing light ?
A. Retaining the rays of light on the
surface on which they fall ; in consequence
of which, their presence is not made sen-
sible by reflection.
1602.
Q. Why can a thousand persons the
same object at the same time ?
A. Because it throws off from its sur-
face an infinite number of rays in all direc-
tions ; and one person sees one portion of
these rays, and another person another.
1603.
Q. Why is the eye pained by a sudden
light?
A. Because the nerve of the eye is bur
dened with rays before the pupil has had
time to contract.
1604.
Q. Why does it give us pain if a candle
be brought suddenly towards our bed at
night-time ?
A. Because the pupil of the eye dilates
very much in the dark, in order to admit
more rays- When, therefore, a candle is
m
LiQm.
brought suddenly before us, the enlarged
pupils overload the optic nerves with rays
^hich causes pain.
1605.
Q. Why can we bear the candle-light af
ter a few moments ?
A. Because the pupils contract again al
most instantly; and adjust themselves tc
the quantity of light which falls upon them.
1606.
Q. Why can we see nothing, when we leave
a well-lighted room, and go into the darker
road or street ?
A. Because the pupil (which contracted
in the bright room) does not dilate instan-
taneously ; and the contracted pupil is not
able to collect rays enough from the darker
road or street to enable us to see objects
before us.
1607.
Q. Why do we see better when we get
used to the dark ?
A. Because the pupil dilates again, and
allows more rays to pass through its aper-
ture ; in consequence of which, we see
more distinctly.
Thus, when the lamp tnat lighted
The trav'ler at first goes out,
He feels awhile benighted
A.nd lingers on ui fear and doubt
LIGHT.
43i
But soon the prospect clear.ng,
In cloudless starlight on he treads,
And finds no lamp so cheering
As that light which heav'n sheds. — Thmnas Moore,
1608.
Q. If we look at the su7i for a few mo-
ments, why do all other things appear dark?
A. Because the pupil of the eye becomes
so much contracted by looking at the sun,
that it is too small to collect sufl&cient rays
from other objects to enable us to distin-
guish their colors. {See "Accidental co-
lors.")
1609.
Q. If we watch a bright fire for a few
moments, why does the room seem dark?
A. Because the pupil of the eye becomes
so much contracted by looking at the fire,
that it is too small to collect sufficient rays
from the objects around to enable us to dis-
tinguish their colors.
1610.
Q . Why can we see the proper colors of
f^very object again, after a few minutes ?
A. Because the pupil dilates again and
accommodates itself to the light around.
1611
Q. Why can tigers ^ cats, and owls, see in
the dark ?
A. Because they have the power of ?n
432
LIGHT.
larging the pupil of their eyes so as to collect
several scattered rays of light; in conse-
quence of which, they can see distinctly
when it is not light enough for us to see
any thing at alh
1612.
Q. Why do cats and owls sleep almost all
day?
A. Because the pupil of their eyes is
very broad, and daylight fatigues them ; so
they close their eyes for relief.
1613.
Q. Why do cats keep winking when they
sit before a fire ?
A. Because the pupil of their eye is
very broad, and the light of the fire is pain-
ful ; so they keep shutting their eyes to re-
lieve the sensation of too much light.
1614.
Q. Why do tigers, cats, owls, etc., prowl
by night for prey ?
A. Because they sleep all day when the
strong light would be painful to them; and
as they can see clearly in the dark, they
prowl then for prey.
1615.
Q. Why do glow-worms and fire-flies, gli»-
len by night only ?
LiaHT.
433
A. Because the light of day is strong
tiiat it eclipses the feeble light of a glow-
worm or fire-fly ; in consequence of which,
glow-worms are invisible by day.
1616.
Q Why can we not see the stars in the
i ay 'time?
A. Because the light of day is so pow-
erful that it eclipses the feeble light of the
stars ; in consequence of which, they are
invisible by day.
1617,
Q. Why can we see the stars even at
mid-day^ from the bottom of a deep well ?
A. Because the light of the stars is not
overpowered by the rays of the sun, which
are lost in the numerous reflections which
they undergo in the well.
The rays of the sun will enter the well very obliquely ; whereas, many
stars will shine directly over the well.
1618.
Q. What is the use of two eyes^ smce they
present only one image of any object ?
A. To increase the light — or to take in
more rays of light from the object looked
at, in order that it may appear more dis-
tinct.
1619.
Q. Why do we not see things double, with
two eyes ?
37
134
LIGHT.
A. 1st. — Because the axis of both eyea
s IB turned to one object; and, therefore, the
same impression is made on the retina of
each eye : and
2nd. — Because the nerves (which receivf
the impression) have one point of union be-
fore they reach the brain. -
This is not altogether satisfactory, although it is the explanation g«*fia
rally given. The phenomenon probably is rather psychological than ma-
terial.
1620.
Q. Why do we see ourselves in a glass ?
A. Because the rays of light from our
face strike against the surface of the glass,
and (instead of being absorbed) are re-
flected, or sent back again to our eye
1621.
Q. Why are the rays of light reflected by
a mirror ?
A. Because they cannot pass through the
impenetrable metal with which the back of
the glass is covered ; so they rebound back
just as a marble would do, if it were thrown
against a wall.
1622.
Q. IVhen a marble is rolled towards a
wall, what is the path through which it runt
called ?
A The line of incidence.
LIGHT. 435
1623,
Q. When a marble rebounds back again
what is the path it then describes called ?
A> The line of reflection.
(See Fig, 4.) If A B, be the line of incidence, then B C, is the line
reflection ; and vice versa.
1624.
Q. When the light of our face goes to
Uie glass, what is the path through which
it goes called ?
A. The line of incidence.
1625.
Q. When the light of our face is reflected
back again from the mirror, what is this re-
turning path called ?
A. The line of reflection.
K 1626.
Q. What is the angle of incidence ?
A. The angle between the line of inci*
dence and the perpendicular.
1627,
Q. What is the angle of reflection ?
A. The angle between the line of refj^o
Hon and the perpendicular. {See Fig. 4.)
436
LIGHT.
S B S
Let S S, be any surface, P B, a perpendicular to it. If a marble were
\hrown from A to B, and bomided back to C ; then A B P, would be
called the angle of incidence, and C B P, the angle of reflection*
1628.
Q. Why does our reflection in a mirror
8eem to approach us, as we walk towards it;
and to retire from us, as we retire ?
A. Because the lines and angles of inci-
dence are always equal to the lines and an-
gles of reflection ; in consequence of whii^.b,
the image will always seem to be as far he-
hind the mirror as the real object is hefon it.
riG. 5.
K 0 C C
LIGHT.
437
Siippose A to be a mirror — C A, E A and D A, F A^ the lines of inci-
dence ; then G A, K A, and H A, L A, are the lines of retietlion. When
the arrow is at C D, its image wiil appear at G H, because line C A=G A,
and line D A,= H A ; and also the an<^le C A B,=a)igle G A U, and an-
^le D A B,=H A B. For a similar reason, if the arrow were at E F, the
image would seem to be at K L.
Q. Why can a man see his whole person.
reflected in a little mirror^ not six inches in
length ?
A. Because the lines and angles of inci-
dence are always equal to the lines and an-
gles of reflection; in consequence of which,
his image will seem to be as far behind the
mirror as his person is before it.
Take the last figure ; C D, is much larger than the mirror A ; but tha
head of the arrow C, is reflected obliquely behind the mirror to G ; and
ihe barb D, appears at H. Why ? Because line C A ,=G A, and hn;t fixed star in 4,500,000 years. Had
it begun, therefore, when Adam was created, it would be no further on ita
journey than a coach (which has to go from the Land's End, Cornwail, to
the Tiost norllief i oa ts of Scotland) after it has passed about three-qaar««'^
of a mile.
1651.
FIG. 16.
B
LIGHT.
449
1652.
Q. Why does the moon (which is a sphere)
appear to be a fiat surface ?
A. Because it is so far o f that we cannot
distinguish any difference between the
\engt\ of the rays issuing from the edge and
those which issue from the centre.
FIG. 17.
A
c
The rays A D, and C D, appear to be no longer than the ray B D ; but
if all the rays seem of the same length, the part B, will not seem to be
nearer to us than A and C ; and therefore, ABC, will look like a flat or
siraight line.
The rays A D, and C D, are 240,000 miles long.
The ray B D, is 238,910 miles long.
1653
Q. Why do the sun and stars (which are
spheres) appear to be fiat surfaces ?
A. Because they are at such an immense
distance, that we can discern no difference of
length between the rays which issue from
the edge and those which issue from the
centre of these bodies.
The rays A D, and C D, appear no longer than B D ; and as B appeari
to be no nearer than A or C, therefore, A, B, C, must all seem equally dis-
tant ; and ABC, will seem a flat or straight line. {See Figure 17.)
1654.
Q. Why does distance make an object in-
mihle ?
A. Because no visible perpendicular can
v)e inserted! between the h'nes which form
38*
450 LIGHT.
the angle; or because the lines actuall}
cross before they meet our eye.
FIG. 18.
Here the tree A D, would not be visible to.the spectator C, even if he
were to approach as far a
LIGHT. 451
the eye, they may be received upon a glass
lens of a convex form, which will have the
effect of collecting them into a space less in
magnitude than the pupil of the eye. If
the eye be placed where the rays are thm
collected, all the light will enter the pupil
1658.
Q. Why do telescopes enable us to see ob-
jects invisible to the naked eye ?
A. Because they gather together more
luminous rays from obscure objects than the
eye can ; and form a bright image of them
in the tube of the telescope where they are
magnified.
As many times as the dimensions of the ohjett-glass exceed the dimen
pions of the pwpil of the eye, so many times the penetrating powers oi me
telescope will exceed that of the naked eye.
1659.
Q. When a ship (out at sea) is approach-
ing the shore, why do we see the small masts
before we see the bulky hull ?
A. Because the earth is round ; and the
curve of the sea hides the hull from our eye»«
after the tall masts have become visible.
PIG. 19.
J^A
Her 5, ciily that part of the ship above the line A O, can bo seen bf Ikd
Ipectaior A ; the rest of the ship is liidden by the swell of the curve 1) fc
152 LIGHT.
1660.
Q. Horn is transparent ; why are not horr.
shavings transparent also ?
A. Because the surface of the shaving
has been torn and rendered rough; and the
rays of h'ght are too much reflected and re-
fraded by the rough surflice to be trans-
mitted through the shaving, so as to pro-
duce transparency.
1661.
Q. Why does wetting a cornelian make it
more transparent ?
A. Because the pores of the cornelian are
then filled with water ; and as the density of
the mass is rendered somewhat more uni-
form than when those pores were filled with
air, the stone becomes more transparent.
Transparency depends on the uniformity of the parts.
If the parts of any substance are not pretty uniform, the rays of light are
refracted and absorbed so frequently, that no part of them can emerge on
the opposite side.
SECTION I. THE EYE, THE SEAT OP VISION,
1662.
Q. What is meant by the retina of the
eye V
A. The net work, which lines the hach
of the eye, is called the retina.
THE EYE, THE SEAT OF VISION.
453
PIG. 20.
The net-work A B C, is called the retina, and the
projecting part D E F, is called the cornea.
N. B. This net-work is composed of a spreit*J'»t!f
out of the fibres of the nerve of vision.
1663.
Q Does light admitted through the pu-
pil to the retina produce vision ?
A. Yes ; provided the light enter in suf-
ficient quantity.
1664.
Q. What is that portion of the eye called
which in some persons is blue, in others gray
or hazel ?
A. It is called the iris.
1665.
Q. In the centre of the iris is a circulai
Uack spot, what is this called ?
A. It is called the pupiL But this spot
is not a black substance but an aperture^
which appears black only because the cham-
ber within it is dark. It is properly speal^-
ing the window of the eye, through which
light is admitted, which strikes on the
retina,
1666
Q. Why are some persons near-sighted ?
A. Because the cornea of their eye is pti
454 LIGHT.
pmninerd, that the image of distant objecln
is formed before it reaches the retina; and,
therefore, is not distinctly seen.
1667.
Q. What is meant by the cornea of the
A. All the outside of the visible part of
the eye-ball.
PIG. 21
The curve A B C, is called the cornea.
If this curve be too prominent (or convex,) tha
eye is near-sighted.
If too flat (or concave,) the eye is far-sighted.
1668.
Q. What sort of glasses do near-sighted
persons wear ?
A. If the cornea be too convex (or pro-
jecting,) the person must wear double con-
cave glasses, to counteract it.
1669.
Q. What is meant by " double concaiH
f^lasses?^^
A, Glasses hollowed-in on both sides.
FIG. 22.
I ^ Figure 22 is double conca'"?, or conca^ e on boih lides.
THE EYE, THE SEAT OF VISION.
455
1670.
Q Where is the image of objects formed,
If the cornea be too convex ?
A. If the cornea be too convex, the image
of a distant object is formed in the vi-
treous humors of the eye, and not on the
retina,
PIG. 23.
Thus the image is formed at D E, and not on A B
C, (the retina.)
1671.
Q. What is the use of double concave spec-
tacle glasses ?
A. To cast the image further hack, in order
that it may be thrown upon the retina and
b^^rome visible ?
1672.
Q. Why are old people far-sighted 1
A. Because the humors of their eyes are
dried up hy age; in consequence of which.
the cornea sinks in, or becomes flattened.
1673.
Q. Wliy does the flattening of the cornea
prevent persons seeing objects which are
near?
A. Because the cornea is too flat, and the
image of near objects is not completely
45 G LIGHT.
formed, when their rays reach the retina; in
consequence of which, the image is imper-
fect and confused.
FIG. 24.
The perfect image is made at D E ; and not on
ABC, (the retina.)
1674.
Q. What sort of glasses do old people
wear ?
A. As their cornea is not sufficiently con-
vex, they must use double convex glasses, to
enable them to see objects near at hand.
1675.
Q. What sort of glasses are ''double con-
vex spectacle-glasses ? ' '
A. Glasses which curve outwards on hc*^
sides.
FIG. 25.
I I Figure 25 is double convex, or convex on both sides.
1676.
Q. What is the use of double convex spec-
tacle glasses ?
A. To shorten the focus of the eye, and
bring the image of distant objects upon the
retina.
THE EYE, THE SEAT OF VISION.
457
1677.
Q. Why do near-sighted persons bring ob-
jects close to the eye, in order to see them ?
A. Because the distance between the
front and hack of the eye is so great, that the
image of distant objects is formed in front
of the retina ; but when objects are brough t
near to the eye^ their image is thrown fur-
ther hack, and made to fall on the retina.
1678.
Q. Why do old people hold objects far off,
in order to see them better ?
A. Because the distance between the
front and hack of their eyes is not great enough;
when, however, objects are held further off,
it compensates for this defect ; and a per-
fect image is formed on the retina.
1679.
Q. Why are hawks able to see such an
immense way off?
A. Because they have a muscle in the
eye, which enables them to fi^atten their cor
nea, by drawing back the crystalline lens.
{Seefig^ 21.)
This muscle is called the Marsupium.
1680.
Q. Why can hawks see objects within
half an inch of their eye, as well as those
a long way off?
39
458
LIGHT.
A. Because their eyes are furnished with
a flexible bony rim, which throws the cor-
nea forward y and makes the hawk near-
sigJttcd.
SECTION ir DECEPTIONS OF VISION.
1681.
Q. Why cannot we count the posts of a
fence, when we are riding rapidly in a rail-
road car ?
A. Because the light from each post falls
upon the eye in such rapid succession, that
the vibration continues for a certain time ;
just as the string of a bow vibrates after it
has been struck, so the vibration of the re-
tina, after the object has been withdrawn
produces a perception of its presence.
1682.
Q. How can the apparent magnitude of
the sun, at the time of his rising, and again
at noon-day, be measured ?
A. This may be accomplished by extend-
ing two threads of fine silk, fastened in a
fram3, parallel to each other. The frame
should be placed in such a position, and at
such a distance from the eye, that when
presented to the sun or moon in the horizon,
the threads will exactly touch its upper and
DECEPTIOJ^^S OF VISION.
459
lower limb, or in other words, be just Buf-
iciently separated to admit of the disc of
the smi or moon to appear between th3n>
and touch.
Now, if the sun or moon be viewed in the
same manner at noon-day, it will be found
that they are just far enough apart to ad-
mit of the disc between them, showing that
the apparent increased magnitude at rising
and setting, is an optical deception, or ror
ther, an error in judgment.
1683.
Q. Can you relate how Captain Score^hy,
when navigating the Greenland Se2/«, Lr yellow and
^ine.) 5.' 'Blue, 6. — Jnc//^o (a shade of blue j) and 7. — Violet (<>r blue
Uid red.)
1696.
Q. How is it known, that a ray of light
consists of several different colors ?
A. Because, if a ray of light be cast
upon a triangular piece of glass (called a
prism,) it will be distinctly divided into
seven colors: 1. — Red; 2. — Orange; 3.
Yellow; 4. — Green; 5. — Blue; 6. — Indigo;
and 7. — Violet.
1697.
Q. Why does a prism divide a ray of light
into various colors ?
A. Because all these coWPs'^ave differ-
ent refractive susceptibilities. Bed is re-
fracted hasty and blue the most ; therefore,
the blue color of the ray will be bent to the
top of the prism, and the red will remain at
llie bottom.
PIG. 28.
B
REFRACTION. 465
Here the ray A B, (received on a prism at B,) would have the blue
part bent up to C ; the y^'ow part to D; and the red part no further
than E.
1698.
Q. What is meant by the refraction of a
ray?
A. Bending it from its straight line.
Thus t).e ray A B, of the last figure is refracted at B into three couifi»
C, D, and E.
1699.
Q. What is the cause of a rainbow ?
A. When the clouds opposite the sun are
very dark, and rain is still falling from them,
the rays of the bright sun are divided by the
rain-drops, as they would be by a prism.
FIG. 29.
Let A, B, and C, be three drops of rain ; S A, S B, and S C, three ray«
of the sun. 8 A, is divided into three colors; the blue and yellow ura
bent above the eye D, and the red enters it.
The ray S B, is divided into the three colors ; the blue is bent above t>.«
eye, and the red falls below the eyeD ; but the yellow enters it.
The ray S C, is also divided into the three olors. The b'ue (whicJi h
bent most) enters the eye ; and the other two below it. Thuy f»y«
466
REFRACTION >
eees the Llae of C and of all drops in the posit>on of C ; the yellow of b
and of all drops in the position of B ; and the red of A, and of all dropf
in the position of A j and thus it sees a rainbow.
1700.
Q. Does every person see the same colors
from the same drops ?
A, No ; no two persons see the same rain
hoto.
To another spectator, the rays from S B, might be red instead of yel-
low; the ray from S C, yellow ; and the blue might be reflected from
Bome drop below C. To a third person, the red msy issue from a drop
above A, and then A would reflect the yellow, and B the blue, and so on.
1701.
Q. Why are there often two rainbows at
one and the same time ?
A. In one rainbow we see the rays of
the sun entering the rain drops at the top,
and reflected to the eye from the bottom.
In the other rainbow, we see the rays of
the sun entering the rain drops at the bot-
fom^ and reflected to the top, whence th(^y
reach the eye
FIG. 30.
REFRACTION.
467
Here the lay S A, (of the primary rainbow) strikes the drop at A — ia
tefracted or bent to is then reflected to C, where A is refracted again,
Kiid reaches the eye of the spectator. {See below.)
Here the ray of S B, (of the secondary rainbow) strikes the tfrop at B
-is refracted to A — is then reflected to C — is again reflected to D, wlien
t is again refracted or bent till it reaches the eye of the spectator.
Q. Why are the colors of the second bow
all reversed ?
A. Because in one bow we see the rays,
which enter at the top of the rain-drops,
refracted from the bottom :
But in the other bow we see the rays
which enter at the bottom of the rain-ciroj^s
Rafter two reflections,) refracted from the top.
(See Figure 32.) Here A B C, represent three drops of ram in Tci
fcECONDARY (or Upper) RAINBOW.
The least refracted line is red, and blue the most
So the RED (or least refracted rays) of all the drops in the ]iosiii,:n of A
— the YELLOW of those iii the position of B — and the blue (or the most to*
fracted rays) of the lowest drops, all meet the ey? D, and form s iB\n
bow to the spectator.
The reason why the primary bow exhibits the stronger colors i« tb.J»-«
)ecan?e the col' rs are se-»n after "'-tc. reflection and
orange is blue,
yellow is indigo,
green is reddish violet,
blue is orange red.
indigo is orange yellow,
violet is yellow green,
black is white,
white is black.
1752.
1754.
COLOR.
483
ments, every thing seems tinged with a
violet c jlor — why is this ?
A. Because violet is the ''accidental color"
of yellow; and, as the sun is yellow, we shall
see its ''accidental color" violet when we
turn from gazing at it.
1755.
Q. Does not the dark shadow (which seems
to hang over every thing after we turn from
looking at the sun) arise from our eyes be-
ing dazzled ?
A. Partly so ; the pupil of the eye is very
much contracted by the brilliant light of the
sun, and does not adjust itself immediately
to the feebler light of terrestrial objects ;
but, independent of this, the '^accidental
color of the sun being dark violet, would
tend to throw a shadow upon all things.
{See Q. 1751.)
1756,
Q. ^Vhy does every thing seem shadowed
with a black mist when we take off our com-
mon spectacles ?
A. Because the glasses are white; and
black being its "accidental color," every
thing appears in a black shade when wo lay
our glasses down.
COLOR.
(The law of an accidjntal color is this — Th« accidental color is alwayt
half the g| ectniin. Thus, if we take half the iength of the spectrum by a
pair of compasses, and tii one leg in any color, the other leg will hit
upon its accidental color.)
N. B. The spectrum means the Beven colors (red, orange, yellow, green,
blue^ indigo, and violet,) divided into seven eqital bands, and placed sido
by gide in the order just mentioned.
1757.
Q. Why is black glass foi' spectacles be^i
for wear in this respect ?
A. Because white is the accidental color
of black ; and if we wear black glasses, eveiy
thing will appear in white light when we
take them off.
1758.
Q. Why are potatoes wliich grow exposed
to the air and light, green ?
A. Because chlorophyll is formed in them
under the influence of the sun's light.
PART VIL
UHAP I.— TRANSiVIISSION OP SOUND
1759.
Q, How IS sound produced ?
A. The vibration of some sonorous sub-
Btance produces motion in the air, called
sound-waves, which strike upon the drum of
the ear and give the sensation of sound.
1760.
Q. How fast does sound travel ?
A. About 13 miles in a minute, or 1142
feet in a second of time.
Light would go 480 times round the whole earth, while sound is going
13 miles.
1761.
Q. Why are some thinj^s sonorous and
others not ?
A. The sonorous quality of any substance
depends upon its hardness, and elasticity.
1762.
Q, What are sonorous bodies ?
A. Bodies which produce sound are called
Bonorxis bodies.
41* 485
486 TRANSMISSION OF SOUND.
1763.
Q. What kind of surfaces are best adapted
for the transmission of sound ?
A. Smootli surfaces, such as ice, water oi
hard ground.
1764.
Q. What plan do savages adopt to hear
the approach of an enemy or beasts of prey?
A. They place their ears to the ground y
and by this means can distinguish clearly
the approach of an enemy,
1765.
Q. Why do windows rattle when carts pas«
by a house ?
A. 1st. — Because glass is sonorous ; and
the air communicates its vibrations to the
glass, Avhich echoes the same sound : and
2nd. — The window-frame being shaken^
contributes to the noise.
Window frames are shaken, 1. — By sound-waves impinging against
them; 2. — By a vibratory motion communicated to them by the walls of
the house.
1766.
Q. Wliy are copper and iron sonorous and
not lead ?
A. Copper and iron are hard and elastic ;
but as lead is neither hard nor yet clastic^
it is not sonorous.
TRANS^IISSION OF SOUND. 487
1767.
Q. Of what is hell-metal made ?
A. Of copper and tin in the following
proportions : — In every five pounds of bell*
metal there should be one pound of tin, au»1
four pounds of copper.
1768.
Q. Why is this mixture of tin and cop-
per used for hell-metal ?
A. Because it is much harder and more
elastic than any of the pure metals.
1769.
Q. Why do we haar a hell if it be struck ?
A. The bell vibrates, and in its agitation,
compresses the air to a certain distance
around it, at each vibration. The com-
pressed air instantly expands, and in doing
so repeats the pressure on the air next in
contact with it, and so on; as a pebble
thrown into still water makes waves all
around it ; diminishing in force, the more
distant they are from the original stroke.
The air thus agitated, reaches the ear where
a similar impulse is given to a very deli-
cate membrane and the mind then receives
the impression of sound,
1770.
Q. How can a bell which is solid be said
to vibrate ?
488
TRANSMISSION OF SOUND.
A. Although the metal of which the bell
is composed is solid, yet it actually changes
its form every time it is struck, and its par-
ticles are thereby thrown into motion.
1771.
Q Why is the scAind of a bell stopped by
lunching the bell with our finger?
A. Because the weight of our finger stops
(he vibrations of the bell ; and as soon as
the bell ceases to vibrate, it ceases to make
sound-waves in the air.
1772.
Q. After striking a finger glass, why is
the sound silenced, upon touching the glass
with your finger ?
A. Because the pressure of your finger
stops the vibrations of the glass ; and, so
soon as the finger-glass ceases to vibrate, it
ceases to make sound-waves in the air.
1773.
Q. Why does a split bell make a hoarse,
disagreeable sound ?
A. Because the split of the bell causes a
double vibration; and as the sound-waves
dash and jar, they impede each other's mo-
tion^ and produce discordant sounds.
1774.
Q, Wliy can persons, living a mile or
TRANSraSSION OF SOUND. 489
two from a town, hear the hells of the town
churches sometimes and not at others ?
A. Because fogs, rain, and snow, ol)-
fetruct the passage of sound ; but when the
air is cold and clear, sound is propagated
more easily.
1775.
Q. Why can we not hear sounds (as those
of distant church bells) in rainy weather so
well as in fine weather ?
A. Because the falling rain interferes
with the undulations of the sound-waves, and
breaks them up.
1776.
Q. Why can we not hear sounds (as those
of distant church bells) in snowy weather
so well as in fine weather ?
A. Because the falling snow interferes
with the undulations of the sound-waves,
and stops their progress.
1777.
Q. Why can we hear distant clocks most
distinctly in clear, cold weather ?
A. Because the air is of more uniform
density, and there are fewer currents of aii
of unequal temperature to interrupt tn€
Bound- waves.
Besid ;s, dense air can propagate sound-waves more readily than
190
TRANSMISSION OF SOVND.
177a
Q. Why can persons (near the poles) hera
the voices of men in conversation for a mile
distant in winter- time ?
A. Because the air is very cold, clear, and
si ill ; in consequence of which, there are
but few currents of air of unequal tem-
perature to interrupt the sound-waves.
Captain Ross heard the voices of his men in conversation a mile and a
half from ihe spot where they slood.
1779.
Q. Why are not sounds (such as those of
distant church bells) heard so distinctly on
a hot day as in frosty weather ?
A. 1st. — Because the density of the air
is less unifoim in very hot weather :
2nd. — It is more rarefied, and, conse-
quently, a worse conductor of sound : and
3rd. — It is more liable to accidental cur*
rents, which impede the progress of sound,
1730.
Q. How do you know that rarefied air can^
not transmit sound so well as dense air ?
A, Because the sound of a hell, (in the
receiver of an air-pump) can scarcely he heard^
after the air has been partially exhausted ;
and the report of a pistol (fired on a high
^^\ouIltain) would be scarcely audible.
TRANSMISSION OF SOUND. 491
1781.
Q. Wliy does the sea heave and sighy just
previous to a storm ?
A. Because the density of the air is very
mddenly diminished ; and (as the density of
the air is diminished) its power to transmit
sound is diminished also ; in consequence
of which, the roar of the sea is less au-
dible, and seems like heavy sighs.
1782.
Q. Why is the air so universally quiet y
just previous to a tempest ?
A. Because the air is suddenly and very
greatly rarefied ; and (as the density of the
air is diminished) its power to transmit
sound is diminished also.
1783.
Q. Why can we not hear sounds (such as
those of distant clocks) so distinctly in a
thick mist or haze as in a clear night ?
A. Because the air is not of uniform
density when it is laden with mist ; in
consequence of which, the sound-waves are
obstructed in their progress.
1784.
Q. Why do we hear sounds better by
mght than by day ?
A. 1st. — Because night air is of more
4.92 TEANSmSSION OF SOUND.
uniform density and less liable to accidental
currents: and
2nd. — Night is more still from the sus-
pension of business and hum of men.
1785.
Q. Why is the air of more uniform den*
nty hy night than it is by day ?
A. Because it is less liable to accidental
currents ; inasmuch as the breezes (created
by the action of the sun's rays) generally
cease during the night.
1786.
Q. How should partition walls be made^
to prevent the voices in adjoining rooms
from being heard ?
A. The space between the laths should
be filled with shavings or saw-dust ; and then
no sound would ever pass from one room
to another.
1787.
Q. Why would shavings or saw-dust^ pre-
vent the transmission of sound from room
to room ?
A. Because there would be sever ao difcr-^
ent media for the sound to pass through :
1st — the air; 2nd — the laths and paper;
Brd — the saw-dust or shavings ; 4th — lath
and paper again ; 5th — the air again : and
TRANSMISSION OP SOUND
493
every change of medium diminislies the
strength of the sound-waves.
1788.
Q. Why can deaf people hear through
an ear-trumpet?
A Because the ear-trumpet restrains the
spreau of the voice and limits the diameter
of the sound-waves ; in consequence of
which, their strength is increased.
1789.
Q. What is a stethoscope ?
A. It is an instrument which resembles
a small trumpet. The wide mouth is ap-
plied to the body and the other is held
to the ear of the Physician, who can hear
distinctly the action of the lungs and judge
whether they be healthy or the reverse.
1790.
Q. Why does sound seem louder in caves
than on a plain ?
A. Because the sides of the cave con-
line the sound-waves, and prevent their
spreading; in consequence of which, their
{frength is greatly increased.
1791.
Q. "Why are mountains more quiet than
plains ?
A. Because the air of mountains is i^^ry
42
494 TRANSMISSION OF SOUND.
rarefied ; and, as the air becomes rarefied^
Bound becomes less intense .
1792.
Q. How do you know that the rarity of
air diminishes the intensity of sound?
A. If a bell be rung in the receiver of
an air-pump, the sound becomes fainter and
fainter as the air is exhausted ; till at last
It is almost inaudible.
1793.
Q. A person situated at the extremity of
a wire 600 feet in length will hear the same
sound twice. Explain this ?
A. The air is not so good a conductor of
sound as the iron wire ; therefore, as it
passes along the wire almost instantaneously^
it requires some time to travel the same dis-
tance through air.
1794.
Q. Can sound be heard through wafer ?
A. Yes ; a bell rung under water can be
heard above ; and if the head of the audi-
tor bo under water at the time, it can
be still more distinctly heard. It is not
however, so loud and clear as when rung
in the air.
1795.
Q. If from an eminence you look dowD
TRANSMISSION OF SOUND.
495
upon a long column of soldiers marching to
a band of music in front, those in the rear
will step a little later than those some dis-
tance before them. Can you explain the
n)ason of this ?
A. Each rank steps, not when the sound
is made, but when in its progress down the
column at the rate of 1142 feet in a
second of time, it reaches their ears. Those
who are near the music hear it first, w^hile
those at the end of the column must wait
until it has traveled to their ears at the
above rate.
1796.
Q. Why does a rail- way train make more
noise when it passes over a bridge, than when
it runs over solid ground
A. Because the bridge is elastic, and vi-
brates much more from the weight of the
train, than the solid earth ; in consequence
of which, it produces more definite sound-
waves.
The brid?:e acts as a sounding board ; and the watc '^r earth oelow the
bridge repeats the sound.
1797.
Q. Why can sounds be heard (in a calm
day) at a s^r eater distance on the sea than on
land^
A. 1st. — -Because the air over the sea is
496 TRANSMISSION OP SOUND.
generally denser and more laden with
moisture, than the air over the land ;
2nd. — The density is more uniform ; and
3rd. — VTater being more elastic than land,
is a better propagator of sound.
SECTION I. MUSICAL SOUNDS.
1798.
Q. What are musical sounds ?
A. Regular and uniform successions of
vibrations.
1799.
Q. What is the difference between a mu-
9ical sound, and a mere noise ?
A. All mere noises are occasioned by
irregular impulses communicated to the ear :
but in order to produce a musical sound, the
impulses, and consequently, the undulations
of the air, must be all exactly similar in
duration and intensity, and must recur after
exactly equal intervals of time.
1800.
Q. Do all persons hear sounds alike ?
A. No ; that faculty seems to depend
upon the sensihility of the auditory nerves.
" Auditory^"* — having the power of liearing.
1801.
Q. What are the boundaries of human heat
ing?
MUSICAL SOUNDS.
497
A The whole range of human hearing,
from the lowest note of the organ, to the
liighest known cry of insects, as of the
cri(5ket, includes about nine octaves,
A-i ears, however, nre by no means gifted with sf> great a range of hear*,
fcg ; man J persons, vhough not at ail deaf, are quite insensible to the high
^ t )te2 of some insects.
1802.
Q How many vibrations of a nmsical
chord are necessary to produce a definite
sound ?
A. When the vibrations are less than six-
>een in a second of time, a continued sound
cannot be communicated to the ear.
1803.
Q. How manT/ vibrations is the human ear
able to appreciate ?
A. The human ear is capable of appreciat-
ing as many as twenty -four thousand vibra-
Hons in a second of time; and, is consequently
able to hear a sound which only lasts the
twenty 'four thousandth part of a second !
1804.
Q. Why are some notes boss, and some
treble?
A. Because slow vibrations produce oass
or deep sounds; but quick vibrations produco
shrill or treble ones,
42*
198 TRANSMISSION OF SOUND
1805.
Q, Why do musical glasses give sounds ?
A. Because the glasses vibrate as soon as
they are struck, and set in motion the sound-
waves of the air.
1806.
Q Why do flutes y etc., produce musical
rounds ?
A. Because the breath of the performer
causes the air in the flute to vibrate; and this
vibration sets in motion the sound-waves
of the air.
1807.
Q. Why does a flddle-string give a musi-
cal sound ?
A. Because the bow drawn across the
string causes it to vibrate; and this vibration
of the string sets in motion the sound-vmves of
the air, and produces musical notes.
1808.
Q. Why does a drum sound ?
A. Because the parchment head of the
drum vibrates from the blow of the drum-
stick, and sets in motion the sound-waves
of the air.
1809.
Q. Why do piano-fortes produce musica]
Hounds ?
ECHO.
499
A. Because each key of the piano (being
struck with the finger) Hfts up a httle ham-
mer which knocks against a string; and the
vibration thus produced sets in motion the
sound-waves of the air.
1810.
Q, Why is an instrument flat when the
strings are unstrung ?
A. Because the vibrations are too slow ;
m consequence of which, the sounds pio-
duced are not shrill or sharp enough.
SECTION IT. ECHO
1811.
Q. What is echo?
A. Echo is reflected sound.
1812.
Q. What is the cause of echo ?
A. Whenever a sound-wave striken
against any obstacle (such as a wall or hill,)
it is reflected (or thrown back ;) and this re-
flected sound is called an echo.
The same laws govern echo as light.
1813.
Q. Wliat places are most famous for echo?
A. Caverns, grottoes, and ruined abbej^s;
the areas of halls; the windings of long pas-
500
TRANSMISSION OF SOUND.
sages ; the aisles of cathedral churches i
moui) tains and icebergs.
1814.
Q. Why are caverns, grottoes, and ruins,
famous for echoes ?
A. 1st. — Because the sound-waves can-
not pass beyond the cavern or grotto ; and,
therefore, must flow hack; and
2nd. — The return-waves (being entangled
by the cavern) are detained for a short time,
and come deliberately to the ear.
1815.
Q. Why are halls, winding passages, and
cathedral aisles famous for echoes ?
A. Because the sound-waves cannot flow
freely forward; but perpetually strike
against the winding walls, and are beaten
hack.
1S16.
Q. Why are mountains and icebergs fa-
mous for echoes ?
A. Because they present a harrier to the
sound-waves, which they cannot pass, and are
sufficiently elastic to throw them back.
1817,
Q. ^Vliy do not the tmlls of a room or
oluirch j)roduce echo.
A. Because sound travels with such velch
ECHO.
501
tity that the echo is blended with the original
sound; and the two produce but one impres-
sion on the ear.
Sound travels ihirteen miles in a minute ; and no echo is heard, unless
the surface (against which the sound strikes) is sixty-five feel from ihe
place whence the sound originally proceeded.
1818.
Q. Why do very large buildings (as cathe-
drals) often reverberate the voice of the
speaker ?
A. Because the walls are so far off from
the speaker^ that the echo does not get back
in time to blend with the original sound ;
and, therefore, each is heard separately.
1819.
Q. Why do some echoes repeat only one
syllable ?
A. Because the echoing body is very near.
The further the echoing body is off, the
more sound it will reflect; if, therefore, it be
very near, it will repeat but one syllable.
1820.
Q. Why does an echo sometimes repeat
two or more syllables.
A. Because the echoing body is far off;
and, therefore, there is time for one reflec«
tion to pass away before another reaches the
ear
502
MISCELLANEOUS.
N. B. All ihe syllatles must be uttered, before the echo of fjt, first syL*
ble reaches ihe ear — if, therefore, a person repeats seven syllables i;i twc
Beennds of time, and hears thetn all echoed, the reflecting object is 1143
feel distant ; (because sound travels 1142 feet in a second, and the words
lake one second to go to the reflecting object, and one second to return.)
1821.
Q. Why are two or more echoes sometimes
heard ?
A. Because separate reverberating sur
laces receive the sound and reflect it in suc-
cession.
Seventeen miles above Glasgow, (Scotland,) near a mansion called
Rosneaih, is a very remarkable echo. If a trumpeter plays a tune and
Btops, the echo will begin the same tune end repeal it all accurately : — ai
soon as this echo has ceased, another will echo the same tune in a lowei
lone ; and after the secorkd echo has ceased, a third will succeed with equal
fidelity, though m a much feebler tone.
At the Lake of Kilkarney, in Ireland, there is an echo which plays an
excellent second " to any simple tune played on a bugle.
MISCELLANEOUS.
1822.
Q. Why do all fruits, etc., (when severed
from the tree,) fall to the earth?
A. Because the earth attracts them.
1823.
Q. Why do the hubbies in a cup erf tei
range round the sides of the cup ?
A. Because the cup attracts them.
1824.
Q. Why do all the little bubbles tend to-
wards the large ones ?
k.. Because the large bubbles (being the
superior masses) attract them.
MISCELLANEOUS.
1825.
Q. Why do the bubbles of a cup of tea foU
low a. tea- spoon ?
A. Because the tea-spoon attracts them.
1S26.
Q. Why are the dides of a pond covered
with leaves, while the middle of the pond is
quite clear ?
A. Because the shore attracts the leaves
to itself.
1827.
Q. Why can you fill a dry glass beyond
the level of the brim ?
A. Because the mass of water in the glass
holds the overplus back by the attraction of
its particles.
1828.
Q. Why is a lump of sugar (left at the bot-
tom of a cup) so long in melting ?
A. Because (as it melts) it makes the tea
above it heavier ; and (so long as it remains
at tlie bottom) is surrounded by tea fully
mtxtroted with sugar ; in consequence of
wliich, the same portions of liquid will hold
no more sugar in solution.
1829.
Q. What is capillary attraction ?
A. Tlie power which very minute tubes
504
mSCELLANEOUS.
possess, of causing a liquid to rise in them
above its level.
Capillary^'''* from the Latin word " capillaris,*' {like a hair;) the tubes
referred to are almost as fine and delicaie as a hair. Water ascenda
through a lump of sugar, or piece of sponge, by capillary attraction.
N« B. The smaller the tube, the higher will the liquid be attracted by )X.
1830.
Q Why does water melt salt ?
A. Because very minute particles of wa-
ter insinuate themselves into the pores of
the salt, by capillary attraction; and force
the crystals apart from each other.
1831.
Q. Why does water melt sugar ?
A. Because very minute particles of wa-
iter insinuate themselves into the pores of
the sugar, by capillary attraction; and force
the crystals apart from each other.
1832.
Q. Why is vegetation on the margin of a
river, more luxuriant than in an open field ?
A. Because the porous earth on the bank
draws up water to the roots of the plants by
capillary attraction.
1833.
Q. Why do persons (who water plants)
very often pour the water into the saucer y
and not over the plants ?
A. Because the water in the saucer is
MISCELLA]S.ROTTS.
505
drawn up by the mould (throiigli the hole
at the bottom of the flower-pot) and is trans-
ferred to the stem and leaves of the plant
by capillary attraction.
1834.
Q. If you leave a little tea in your cup,
and rest your spoon on the bottom of the
cup, why does the tea rush to the spoon?
A. Because the spoon attracts it, by what
is called capillary attraction.
1835.
Q. If a drop of loater be spilled on a
table-cloth, why will it spread in all direc-
tions ?
A. Because the threads of the cloth ab-
sorb the water by capillary attraction.
1836.
Q, Why are old people unable to walk ?
A. Because their muscles become rigid.
1837.
Q. Why is it more easy to simm in the
sea than in a river ?
A. Because the specific gravity of salt wa-
ter is greater than that of fresh ; and, there-
fore, it buoys up the swimmer better ?
1838.
Q. How do cooks ascertain if their br\m
bo salt enough for pickling?
43
506
MISCELLANEOUS.
A Tliey put an egg info their hrine. II
the egg sinks, the brine is not strong enough ;
if the egg floats, it is.
1839.
Q. Why will an egg sink, if the brine be
not strong enough for pickling 1
A. Because an egg will be the heavier ;
but if as much salt be added as the water
can dissolve, an egg will be lighter than
the strong brine, and consequently jSoat on
the surface.
1840.
Q. Why will an egg float in strong brine,
and not in water ?
A. Because the specific gravity of salt
and water is greater than that of water only.
1841.
Q. Why do persons sink in water when
they are unskillful swimmers ?
A. Because they struggle to keep their
head out of water.
1842.
Q Why can quadrupeds swim more easily
than man ?
A. 1st. — Because the tru?ik of quadru-
peds is lighter than water ; and this is tho
greatest part of them ; and
MISCELLANEOUS.
507
2nd.— The position of a beast (\^•bell
8\^imming) is a natural one.
1843.
Q. Why is it more difficult for a man to
swim than for a heast ?
A, 1st. — Because his body is more heavy
III proportion than that of a beast; and
2nd. — The position and muscular action
of a man (when swimming) differ greatly
from his ordinary habits ; but beasts swim
in their ordinary position.
1844.
Q. Explain how this is ?
A. When the head is thrown back boldly
into the water, the mouth is kept above the
surface, and the swimmer is able to breathe.
But when the head is kept above the sur^
face of the water, the chin and mouth sink
beneath it, and the swimmer is suffocated.
This may be illustrated thus: — If apiece of wood be of such specific
gravity, that o\\\y two square inches can float out of water ; it is manifest
tljat if two other inches are raised out, the two former inches must b*;
plunged in. The body (in floating) resembles this piece of wood. — If twci
equ^re inches of the fa-^, float out sic, antidote for, 324.
tannic, 318.
tarf.iric, 319.
Aftryle, 525.
Action, cliemical, a source of heat,
43.
mechanical, 161.
heat produced by, 161.
Activity agreeable in cold weather,
312.
Adhesive, glue, 129.
gum, 129.
paste, 129.
starch, 129.
Aeiated water, 217.
Air, 193.
a had conductor, 85, 87, 89, 90,
91, 104, 153.
absorbs heat, 151.
a non-conductor, 31.
apple? contain more than chest-
nuts, 46.
alm:)Spheric, 193.
between the fibres of wool, 89.
blovv^ obliquely into the fire, 75.
chamber, 52.
CO. J, condenses vapor, 134.
comes down the chimney, 69.
composed of nitrogen, 193.
why, 194.
condensed bv cold. 320.
Eooled. 329 32^>.
Air, ctt. rents of 343, 514.
in a room, 61.
ovei land, 400.
danip, iron rusts in, 177. 173.
den'-ity of, dnninished, 390.
previous to a storm, 331
draws away heal from us, 88.
effeL-t o( cold upon, 329.
effect of heat on, 332.
expanded by heal, 43, 338.
expulsion of, 45.
c;«uses wind, 349
filled with odor before rain, 133^
fire burns better in the, 241.
supplied with, 'iS.
oy a tube, 69
gun, 168.
heal '^xpands, 332.
o/ affects mercury, 333.
swells, in a bladder, 43.
heatr-l, 103
how, 323.
a conductor, 23.
by convection, 87.
horses snuff up, before rain, 13t
hot, houses heated with, 51.
c a sunny day 104.
hotter ihan our bodies, 15-4.
in an apple, 4(>.
our bodies, 369.
an e^rg, 529.
lightning purifies the. \f}
linen •tried in the, 125.
mateiial, 191.
moisture of, dissolves salt, \^
more subtile than water, 86.
motes, if dust in, 1U6.
never at rest, 87.
mdintes heat, 335.
nitric ocid purifies the, 38.
not heated by the sun, 10-1,
invisible, 194, 195.
of aro.jm always iu motioUj ffl
151.
ciri^^s nnpure, 206, SOS
eoui.'ry pure, 205.
531
532
INDEX.
Air of uiiif.irni (U-iiKity ni iiiplii, 402.
on llii- eurf.irr ..(' liw ciirili, 144.
one (.•fjld- r ili iii .iiioilicr,
optn, bed f..i Ih' nil, '^05.
out of (Joora ii. ,-<•, •ill.
over waiter, .'51 !.
purted liy liRlilnint;, 31.
pro|K)riion3 of IkjI, destroyed,
3(U.
Tire, wlieru t)icr« are few iu-
habiJHnl?, 'JO.'),
quiet before a siorm, 491 .
ruin coo).«» tlie, 125.
rarefiiciion of, (>(J.
rarefied, ai>ceiiils, GG.
Ji(iuri8lie8 the fire lit-
tle, 240.
refracts Iig:lit, 4(il .
resisis the passjige of liphtning,
31.
rusts iron, 170.
seeks an f(|uilil)rium, 338.
trees rcncUr it wliolesuine, 206.
undulations of, 45.
vapor of", .'Ji)9.
viliuicd by n crowd, 202.
Vlbumen, 292, 291.
effects of, CD sugar, 274.
Mcoliol, 27G.
formed by fermentation of
sugar, 270.
generated by fermentation,
276.
of what composed, 277.
Kle and porter frotii, 49.
bc.tfle. cork forced out of, 49.
bottled froths, 217.
porter darker tVian, 250.
A.lkuli, 219.
detrimental to combustion, 236,
)iart.4.
Ancients, acquainted with electri-
city, S'.
Angle of incidence, 435.
redt'ction, 4.15.
Animal heat. 297.
li''e dependent on vegeia-
■)le, 305.
Animals good conductors, 25.
the Uesh of olU, tough, 293.
Anthracite, 197.
Antidotes for |>oi8on8, 324.
Appetite, rapid dige.-5iion produces,
811.
! Apple, coiitnin« more I ina: i ehcm,
I iiiit,4U.
■oft when roHnted, 46.
■plits wiieii roanted, 45.
lApplcH, unripe, Sour, 318.
I Argund laii.ps do not «moke, 217.
I Allies make In.rd water soft, I'.W
j Atmosphere, 327.
polar and equal r a
349, 350. •
I Atimwpheric air, 193, 327.
< Attica and cellars unxufe in a Bt^rm^
Aurora liorealig, 367.
cauf^c of, .357.
colors o(, 13.
Avenue of trees, 445.
i
n.
liaU, hole nuide by, 169.
Balls of fire, why dangerous, 20.
run along the ground, 20
I produce luiM hiff, 20.
! lightning looks like, 19.
(' cannon, hesited, H>r.
■ Balusters damp after a thaw, 405.
Balloon, a.^cen.sion iji, 330.
I inflated, 49.
I lij.s. 50.
iBaik of a tree torn by ligiitning, 33
; Barley malted, why, 276.
1 how, 279
; not sofTcred to spn ut, 279.
' prevented from Hhooiing, 278
Barometer, 332.
a weather glass, 3.34.
I and thermometer, differ
ence between, 333.
indicates the approach of
storm, 335.
tube of, open, 33-1.
uumed, 299.
rubbing warms it, 168.
temperature of, 123.
Boiled eggs discoior silver, 2S7.
water fl it, 211.
BliVer of kitchen ranges bursts, why,
59.
B^iiAng brine hotter tlian water, 120,
rattling mnde by, 117.
walcr bubbles, 116.
forms steam, 119.
Boiling * «.er heat of, consumed in
melting ice, 133.
in a fermeni, 100.
kept on the fire, 102,
swells, 11.1.
Books discoiored by age, 522.
Bottled ale froths, 217.
pc-ter froths, 218,
Bottom ot'-\ kettle cold, 93.
' saucepan covered witb
sooi, IGO.
Brass, 265 .
Bread, VS
bdkiiii( dc ugh converts it into,
284 ■
becomes iiard by being kept
128.
full of holes, 285.
leavened, 233.
new, indigestible, 283.
Breath, condensed on our h-iir, 406.
visible in winter, 406.
Breathing, how performed, 303, 304.
rapidly makes us warjn,
303.
Bricklayers cover their work with
straw, 424.
stop work in frosty wea-
ther, 423.
Brewing, yeast used in, why, 280.
Bricks and flag-stones locseiied after
a frost, 52.
turn green, 528.
Bright and dark spois in a clear fiie
232.
iron in the fire, 178.
metal a bad radiator, 161.
Brine boils, 120.
egg floats in strong, 500.
how made, 50G.
Britannia metal, 2G5.
Broth cooled by blowing, 153.
convection, 105.
f-tirring, 105.
Brown paper adhesive, 10.
igniies sooner than
white, 150.
Bubbles follow the spoon, 503.
in tea, 502.
small tend to the large, 502
Brushing the hair excites it, 11.
Bullion, spoons tarnish sooner than,
181.
Burn, ether relieves a, 122.
Burnt bread purifies water, 199.
Bursting of ache-^inut fhel' iMinses ■
534
Suiter, 323.
hard ',n cold weather, 322.
C,
CJiikes crisp, 523.
Caloric, liow distributed, 8.
Calcutta, black hole of, 203.
Calms, region of, 345.
»"!ambric handkerchief feels cool, 92.
U indie, body consumes like, 298.
bu-ris when lighted, why,
252.
extrnguished, 258.
fiame of blown out. 256.
conical, 256.
extinguished, 251.
hand above, 257.
hot, 253.
inside hollow, 255.
lower part purple,
254.
on glass, 256.
outside yellow, 254.
parts of, 254.
points upwards, 255.
produces light, 254.
yellow, 254.
flickers, 260.
requires snuffing, 259.
spirts in damp weather, 302.
tallow of, decomposed, 253.
wax, requires no snuffing,
259.
wick of, 221.
Cannon balls heated, 169.
borers hot, 167
Capillary attraction, 503.
vessels, 297.
combustion in, 298.
throughout the bo-
dy,'297.
Carbor., 195.
gives firmness to plants, 305.
Carbonic acid gas, 200.
absorbed by lime,
210.
plants,
207.
accumulation of,
210.
causes death,
201, 203, 204.
forced into wa-
ter, 216.
formed by sugar,
876.
Carbonic acid gas, geneiated by com
bustion, 242.
heavier than aif
203.
how diffused, 207
209.
fatal, 300.
found, 201.
In beer vats, 206.
in blood, 298.
in the soil, 519.
lime combines
with, 212.
of cities whence
derived, 207.
of water, 214
plants absorb, 305.
produced by fer-
mentation, 210,
276.
renders water acid
210.
sources of, 209.
Carburetted hydrogen, 220, 2-21.
inflammable, 220
on marshes, 220.
Carpenters* tools hot, 167.
Carriage in a tlmnder storm, 26,
wheels catch fire, 165.
Cart v/heels, grease on, 166.
Caseine, 295.
in some vegetables, 205
Cats and owls sleep in the day, 432
hair not smooth, 12.
prowl by night for prey, 432.
rub their ears, 11.
wink before a fire, 432.
Cattle good conductors, 25.
Cause of fog and clouds, 357.
lightninof, 14.
Caverns famous for echoes, 500,
Ceilings black, 510, 511.
Cellars cool in summer, 331.
warm in winter, 331.
Chandelier, lustres of, 479.
Champagne, 218.
contains carbonic acid
gas, 219.
cork flies when looaea-
ed, 218.
Change of state, 107.
Charcoal, 196.
fire hot, 197.
in chambers, 208
purifies meat, 197.
water, 199.
Chemical action a source of K«il 43
INDEX.
555
l^emicttl aoXioA in combustion, 229.
changes produced by com-
busiion, 230.
Chemistry, organic, 272.
Chextiv'it, apples contains more air
than, 46.
cracks when roasted, 44.
oursting of shell, causes a
report, 45.
will not crack when slit,
45.
in anney, air comes down, 69,
contracted prevents
smoking, 76.
cowl on, 73.
will not prevent
smoking, 73.
draught slack in, 76.
farm house smokes, 75.
flue high, 74.
funnel or flue of, 69.
long, smokes, 50.
of manufactories long, 71.
opening of, contracted, 72.
too large, 76.
out of repair smokes, 75.
pots increase the draught,
77.
raised above the roof, 69.
use of, 77.
smoke ascends, 50, 68.
smokes if it needs sweep-
ing, 75.
the air in it be
cold, 50.
the flue be too
short, 70.
in gusty weather,
76.
«moky, 68.
remedy for, 69.
vestry, smokes, 73.
wind in the, 51.
strikes against the
sides of the, 74.
ChloriJd of lime, 516.
China cup broken by hot water, 55.
Chlorine gas, antidote for. 326.
Choke damp, 207.
Church bells, dangerous to ring, 22.
heard at a distance, 489.
congregation drowsy, 204,
hottest place in, 65.
St. Bride's, destroyed by
lightning, 34.
yards, eflluvia of. 226.
Ohyle, 306
Chyle converted into biood, 307.
Cider, 218.
Cinders lighter than coal, 235.
red hoi sooner than coal, 235
will not blaze, 238.
Circle of fire, 460.
Cirro-cumulus cloudp, 372.
Cirro-stratus clouds, 372.
Cirrus clouds, 360, 370, 371
Cities, air of, impure, 2CG,
Citric acid, 319.
Cleanliness, ill-clad averse to, 301
ill-fed averse to, 314.
Clear weather ftgreeab.'e, 368.
Close rooms unhealthy, 206.
Clothes damp in the evening, 383.
Clothing, furs used for, 87.
laborers shouW not wea?
too thick, 130.
loose, warm, 89
use of, 88.
warm needed at night,302
wet with sea water, 130 ,
w-oolens used for, 87.
Clouds, 356.
affect the wind, 342.
cirro-cumulus, 372.
cirro-stratus. 372, 373.
cirrus, 369, 370, 371.
cumulo-stratus, 373.
cumulus, 370, 371.
division of, -369.
edges luminous, 470,
electricity affects, 359.
in the, 13.
electrified, of fanciful
shapes, 359.
fall in rainy weather, 390.
float in the air, 357.
forests detain and condense
the, 126.
gather round mountain tops.
374.
general colors of, 360.
not always
alike, 362
height of, 15, 358.
lightning, 11.
higher on a fine day, 353
how discharged, 14.
in a negative state of elec-
tricity, 18
positive state of electn*
city, 18.
lighter on a fine day, 35ft
lightning passes frou, to tk«
earth, 13.
530
INDEX.
Clouds, moditicul ion of, 369.
motion of, 362.
nimbus^ 373, 374.
red in ihe evetiitig:, 381 , 469.
nnori'.iiig, 331, 469.
size of, 35S.
stratus, 370, 371.
subdivision of, 369, 372, 373.
suddep.ly dissipated, 353.
thickness of, 358.
ihunder-bolts never drop
from, 41.
uses of. 3G3.
Variety of shape. 359.
vary in form, 357.
velocity of, 355.
what are lowest, 358.
winds absorb, a59. 360.
blow up, 363.
chans^e the shape of,
360.
drive away, 360.
iii'jrcasc me bulk of,
360.
UlDudy nights warm, 377.
Coal, bhck, why, 478.
blazing, burns quickly, 231.
cinders red hot sooner than,
235.
lighter than, 235
gas, 220.
good for fuel, 197.
mines explode, 221.
Ooins, silver of U. S., 264.
gold of U. S., 264.
Coke, 197.
Cold, air condensed by, 329.
condenses vapor, 134.
blooded, frogs and fishes. 301.
car.not penetrate the earth, 93.
dead body, 302,
expands water, 416.
forests produce, 126.
iron contains heat, 162.
long grass promotes, 127.
rolling leaves promote, 127.
water on lime, 112
weather, activity agreeable in,
312.
meat and grease de-
sirable Ml, 309,
more food eaten in,
3!)9.
when applied to liquids, 102.
Cfj>WeT in a thaw than in a frost. 421.
oi>l of door.s than in, ft3.
Coldness of the air increases the hre,
239.
Collapsinfrof a bladder, 330.
Color, 177.
none in the dark, 480.
Colors, of Aurora Borealis, 13
clouds, 360.
not always aiike,
G€2.
dark absorb heat, 156.
warmest, 155.
Column of soldiers marching tc mu-
sic, 495.
Combining and mixing, diflerencti
between, 35,
Combustion, 228.
alkaiies detrimental to, 230.
capillary ve.ssels, 298.
chemical action in 2<^9.
changes produced
by, 230.
elements of, 229,
lermentation prodnces, 249.
heal evolved by, 228
in the human body, 299. 300
intensity of, unequal, 232.
of fuel, 229.
oxygen supports, 174, 175.
produces light, 428.
spontaneous, 248.
cause of, 248.
sunshine detrimental to, 7.
Common solder, 266.
Components of the animal body, 292..
Compression, 168.
heat evolved by, 168
Condensation, !68.
Condensed air descejids, 330.
Conductor, lightning chooses the
best, 35.
man better ihan a tree, 33.
Conduction of heat, 79,
Conductors, of heat, good, 79, 80j 8lj
82, 83, 84, 85
92, 97, 98, ^i. '
cambric 92.
fire irons, 98.
linen, 92.
metals, 79, 80, 81-
85, 97, 99.
metal spoon, 97.
solid bodies. 79,
stone, 82,83,81
Conductors, oi neat, 6ar/, 80, 82, 84.
85, 86, 87, 88,
90, 91, 92, 93, <>V
06 9€ P7 98.
INDEX. 537
OoaAxLttC'tL ah. bad, 8li, 87 89, 90,
90, 01.
bricks, 87, 98.
coUon, 92.
curtains, 124.
down, 89.
earth, 92, 93.
leatliers, 89.
far, 87.
nair, 88
leaves of trees,
95.
'iquids!, 86.
oil, 96,
paper, 95.
porous bodies, 80.
snow, 94.
soot, 96.
straw, 90.
water, 86.
white paint, 97.
wood, 60, 82, 84.
wool, 80, 81, 82,
84,87,95,98.
l>>Bductors, oi liglilnmg, good, 21,
23, 24, 25,
28, 32.
animals, 25.
bell- wire, 24.
cattle, 25.
copper, 28.
heated air, 23.
human body,
32.
inside of a
man, 32.
mass of bodies,
32.
metal, 24.
outside of
tree, 32.
running wa-
ter, 21.
soot, 23.
trees, 25.
vapor, 24.
walls, 23.
wet clothes,
28.
Conductors, oi lightning, badj 31,27.
air, 31.
bed, 27.
mattrass, 27.
Conducto:^^ lightning, 28.
best metal for, 28.
influence of, 29, 30,
pointed 29
Conductors, ightning, productive «f
harm, 3u.
too small, 30.
use cf, 2t>.
Conductors of heat not absorbers,
149.
Convection, 99.
air heated by, 67.
iron cooled by, 104.
Convective currents, 103, 328.
Cooking, smoke in, 160, 161.
vessels with wooden hLTi-
dies, 84.
Cool under a shady tree, 91.
Copper and iron sonorous, 486.
best conductor, 28.
better than iron, 28.
tarnishes, 180.
Cork forced out of ale bottle, 49.
of a champagne bottle, 218.
Corns ache before rain, 509
Cornea, 454.
too convex, 455.
flattened, 455.
Cornelian transparent when wet,
452.
Corrosive sublimate, antidote for,
325.
keeps paste from souring,
282.
Cotton handkerchief feels v/arm, 99,
Countries least cloudy, 357.
most cloudy, 357
Country air pure, 205.
Course of the wind, 342.
Covering radiates heat, 131.
Cowl, use of, 51.
on a chimney, 73.
not prevent smcke, 73c
Cultivation increases warmth, 126.
Cup, china, broken by hot water, 55
in a pie, 52.
full of juice, 53.
makes it boil over, 53
Currents, convective, 103.
of air, 343, 344.
in a room, 61.
water pass each other
100.
Curtains bad conductors of heat,121
rooms separated by, 124.
warmer with, 91.
sprinkled with water, 124
Crov/d unsafe in a storm, 24.
Crowded room produces head-ache,
201,
unwholesome 209
INDEX.
Crystal is wliat, lOo.
Cultivated soil radiates heat, 382.
Cuinulo stratus clouds, 373.
Curriuius elouds, 370, 371.
Cariair juice is made into jelly, 520.
i>.
Ts-yi] bci unhealthy, 122, '23.
O^oduces decay, 249.
> opper sticks, 60.
Weather, distant sounds not
heard, 4S9.
i>^rk colors ahsorb heat, 156.
warmest, 155.
phosphorus luminous in the,
225.
Oavy, Sir Humphrey, 222.
Dead body cold, 302.
taller than a living one,
317.
Decanter, stopper of, sticks, 59,
Decay, damp produces, 249.
of wood, 212.
prevented, 291.
Decaying vegetables, 2SS.
mnist, 288.
Deceptions of vision, 458.
Deserts dazzle from sun.«hine, 476.
Detonating salt and powder explode,
169.
Dew, 374.
abundant, when, 376.
and rain, 375.
after a moist wind, 384 , 3S5.
cause of 375.
deposited on a clear night,376.
drop does not wet cabbage,
387.
a rose, 367.
rolls, 386.
round, 386.
sometimes flattened, 386.
dry wind prevents, 384.
ground covered with, 375.
m the morning, 377.
evening injurious, 3S5.
most abundant when, 384.
near walh, 378.
none after a windy night, 379.
on a cloudy night, 377.
some things covered with,380.
under a siiady tree, 378.
valleys covered with, 379.
lainond, 195, 196.
Oiirc-tion, rapid, produces appetite,
311
Oi:nter covers. 112, 143.
Dinner coverf not chased, Xi'J.
Discharge of a cloud, 14
Distance makes an ob'ect invisJ;!*,
419.
of thu uder clouds told, 40, 42.
Distant sounds not heard in damp
weather, 489, 491.
Divers sulTer pain in their ears, 500
eyes. 508.
Diving bell, descending in, '330'.
Door and fire on the sume side, 74.
opposite to the fire, 75.
shrinks in dry weatlier, 133.
swells in rainy weather, 133.
Double-concave glasses, 454.
use of, 455
convex glasses, 456.
use of,
Doughjbaking converts it into bread
284.
effect of yeast on, 283.
fermentation makes it rise,
283
placed before the fire, why
285.
will not rise well if it be cold
285.
Down, bad conductor, 89.
Draining land, dimini^^hes evapora*
lion, 126.
promotes warmth, 126.
Draught, chimney-pot hicreases the,
77.
depends on the speed ot
smoke, 71.
of a short flue slack, 70, 71.
slack in a chimney, 76.
through a key-hole, (i3.
an open window, 64
window crevices 64
under a door, 64.
Draughts, effervescing, 216.
Dreamers no power of 'UQgmeal
. 315.
Drum, sound of, 498
Drummond light, 187
Dry gla^s filled ah.ove Me Lrini^ 'tC^
weatlier, a thunder-storm .'oJ-
/ows, 42
soil bard in. 128.
winds, 341.
wood burns belter than green
48, 235.
snaps more than green
Dunghill, heat of, 248
Dui^t no affinity for water, 3S1
rfircly flies at night, 37?,
INDEX.
539
Diiaty ahots hot, 149.
Dutch gold, 2t>4.
Dwelling: parts of, dangerous in a
stonn^ 22.
E.
Bar-trumpets, vise of, 493. ,
Earth a bad conductor, 92. i
below the surface cool in sum-
mer, 93
warm in winter, 93.
colder than the air, 376.
crumbles in the spring, 422.
heal cannot penetrate, 93.
rotundity of, 451.
warmer than the air, when,
376.
wet, promotes evaporation,
125.
FiUrlhenware, 271.
Ebullition, 113.
Echo, 499, 501, 502.
cause of, 499.
caverns famous for, 50u.
hali?, etc., famous for, 500,
501.
mountains famous for, 500.
places famous for, 499.
Effects of evaporation, 121.
lightning, 33.
Effervescence, 216.
cause of 216.
so3n subsides, 218.
Effervescing draughts, 216.
Effluvia of church-yards, 226.
Egg fresh or stale, 90.
shell of a stale, warm, 90.
tarnishes silver, 525.
thick end cold when fresh, 529.
Elbow-joint, electric shock felt at,
30.
Electric shock felt at the elbow-joint,
SO.
Electrical cloud, how discharged,14.
Klectriciij a source of heat, 9.
affects clouds, 359.
in the clouds, 13.
invisible, 12.
known to the ancients, 9.
negative, 18.
odor of, 12.
positive, 18.
produced by friction, 9.
produces itching, 11.
Electrified clouds of fanciful shapes,
35S
Elemenlf, non-metallic, 170.
Elements of comlastion, 229.
fuel, 229.
Esquimaux fond of train oil, 309.
Ether, 427.
un{lu!ations of, produce lightj
allays heat, 121.
better th-ni water j 121 ,
freezes in an exhu'istel t=g
ceiver, 425.
relieves a burn, 122.
Evaporation, 121.
carried, on, 127.
draining land diminish
es, 126.
effects of, 121.
heat produces, 85.
macin.tosh prevents 123.
of sea, 340.
of water, 124.
produces cold, 125,425.
reduces lem.nerature»
124
wet earth promotes,
125.
'Evenmg breeze, 352.
clouds red, 469.
Ewers break in a frosiy night, 413.
Expansion, 43.
of air, 45.
liquids and gases, 43.
metals, 64.
Explosion of gunpowder produces: j
report, 45.
Eyes, do not see double with two
433.
negroes have black, 153.
use of two, 433.
Eye pained by light, 429.
pupil of, dilates in the dark, 423
431.
does not dilate instantly
430, 431.
soon contracts in the lifk
430, 431.
seat of vision, 452.
F.
Fanning, 152.
heats the rar, 15S
the face, 152.
Farm house chimnt y smoker, 75
Fat persons swim easily, 507.
Feathers bad conducior, 89.
Feeling, sensraion of, 317.
lost, ?V
Feet cold by a good fir^, ^7.
540
INDEX.
Fermentation, 275.
and putrefaction, 275.
compounds produced
by, 275.
makes dou^h rise,283.
of sugar, 275.
produces carbonic
acid, 210.
coif;bustion,249.
fibr.ne, 295.
?;edle strings snap in wet weather,
302.
pound of, 498.
f ingcr ?lass, vibrations of, 488.
Fire, 229.
a little water makes it burn,
243, 244.
blazing, 230, 231.
brio ht and dark spots in, 232.
burns bstler in the open air,
241.
winter than sum-
mer, 239.
briskly in windy wea-
ther, 241.
less fiercely in a frost,
241.
carriage wlieeU catch, 165.
cii.Mrcoal, in chambers, 209.
coldness of air increases, 239.
covered, 239,
dangerous in a thunder storm,
23.
door opposite to, 75.
dull if the flue be short, 70.
revived, 245.
stirring quickens a, 245.
flame of a good, yellow, 251.
forests on, 167.
goods catch, of themselves,
248.
greasy rags sometimes catch,
250.
heat of, 247.
horses strike, with their feet,
184.
hydrogen gas of, 238.
in adjoining rooms smokes, 72,
intensity of, 245.
irons good conducl'^rs, 98.
kindled at the bottom of the
grate, 234.
light of 237.
neighbors house on, 244.
on a ^rosty night, 238.
burns clear, 239. '
pjipei chars if laid flat on, 242. 1
Fire, placed near the floor, 78
poker laid across revives it, ?6
powdered sulphur will
quench, 245.
produced by friction, ld5
produces heat, 230.
red hoi, 230, 231.
room with two, 72.
small opening near tns, pr«
vents smoke, 72.
sparks of, burst from woc*
Latent hear, 110, 182.
developed from woc: k
with, 424.
delicate trees covered with,
424.
ice houses lined with, 96.
in a barrel of liquor, 511.
water pipes covered with, 421
Street, hou.ses in, 446.
seenr\ smaller m the
distance, 447.
Striking iron makes it red hot, 192.
Strings flat when unstrung, 4^
Stucco peels in frosty weather, 423
Substances, all, radiate heat, 1S^.
are gaseous, 108.
liquid, 109,
Kolid,
554
INDEX.
SubslaiMJcs which ladiate heat ab-
sorb it, 139.
Bwddcn change of temperature, 352
8ugar, 272
and salt retard boiling,' 1 19.
a vegetable substance, 272.
ferrnentfition of, 275.
flavors water, 190.
forms alef)bo!, 276,
carboi'ic acid, 276.
from the suijar cane, 273.
grape, 274, 275.
how obtained, 273.
refined. 273.
loaf, 274.
long in melting, 503.
lump of, in tea, 512.
Sulphur, powdered, will Qiiench
fire. 245.
Bulphuric acid and water, 112.
Summer lightning, 17.
Sun and m'>on, magnitude of, 458.
stars appear flat surfaces,
449.
appears Inrge in the horizon,443.
does not heat the air, 328.
fades artificial coh)rs, 481
ground hardened by, 128.
heat of, 7.
ice melted by, 136.
red in a fog, 470.
rise gray or red, 366.
red, 365.
indicates rain, 385.
light on water, 441.
reflection of, in a well, 439.
set coppery yellow, 364.
gray indicates rain, 366.
red, 363.
indication of a fine day,
364.
yellow indicates rain, 3G5.
btinshine detrimental to combustion,
7, 2-40.
Surfaces, some brilliant others dull,
428.
Swallows fly low before rain, 393.
Swans and ducks dive, 387.
Sweet- wort, eft'ect of yeast upon, 280.
T.
Taint of meat removed, 289, 29Q,
317.
Tallow, 198.
of a candle decomposed, 253.
Tamarinds sour, 319.
Tannic acid, 318.
Tartaric acid, 3! 9.
Taste, power of , 317
Tea, green, unwholesome, 326.
Tea, hot, cooled by stirring, 105
faster in a ?aucci
129.
pot of black earthen, 141,141
polished metfil, 14 1.
S(mchniig poisons flies, 326.
Telescopes, 451.
use of, 150.
Temperature of IsUmds, 150, 151,
the body., 84, 123.
reduced by evapora
tion, 124.
Thaumatrope, 46!).
Theatre utisafe in a storm^ 24.
Thermometer, 333.
mercury rises in, M
Thickness of clouds. 358.
Thunder a deep growl. 40.
an irregular roar, 39.
bolts never drop from thduc«
sound, 497.
number of appreciated ,
497.
which soonest heard; 33,
Vinegar sour, 320.
Violet, accidental color cf, 483.
is l)lue. why, 477.
Vision, how pioiluced, 453.
the eye the seal of, 452.
Void of air in a room supplied, 63.
Volatile oils, 321.
W.
Walls of a house damp in a lhafv,
404 , 4')d.
556
mDEX
Willis aria tfe to lean agJisiis^t in a
stor ji, 23.
Wariu, breavhing rapif^.y makes us,
302.
fiannf j keeps ub, M'i
running makes us, '^^^2.
Warmer in u frost than sn a thaw,
421,
Warmth, belt^ of trees promote, 126.
cuhivaiion ircreases, 126.
draining of land promotes,
126.
hedges promote, l'2fi
of man}- of th e Stales, 125.
Water, 187.
a bad conductor, 88, lOi.
a better conductor than air,
85.
aerated, 217.
a ilitle, makes a fire burn,
243^ 214.
and Bir rot wof-d, 528
potassium, 1P4.
lime combine, 36.
sulphuric aci(!, 112.
wine casks charred, 199.
boiled, flat, 211.
boilmgj bubbles, 116.
heal of consumed, 136.
in a ferment, 100.
kept on the fire, 102.
swells, 115
bottle of, wetted with ether,
424.
burnt bread purifies, 199.
carbonic acid of, 214.
forced into, 2i6
renders,
acid, 210.
cleans linen, 13 .
clothes wet wi. i sea, 123,
13;J.
con\rerted into steam, 102,
131.
currents of, 100.
curtsuu? sprinkled with, 124.
depih of, ret-'iTUs freezing,
4-20.
drop of, rolls over hot iron,
13i, 1.35.
etht;r allays hf:at better than,
12t.
expanded, 117.
es'jands froin rolri. 416.
he:.C, 415.
extinguishes I. fire, 243, 244.
Water, fluid, 187.
freezes first at tiic surface ot
rivers, 416.
sooner when exposed.
131.
than mi)k.fl2e
fresh, sparkles. '214.
fuel for fire, 243.
hard, agreeable to drir-ic, 5 \i
exposed to the air, 2U
made soft by ashes, IDO
unsuitable for washing
188.
heat separates, 115.
hot, breaks glass, 55.
china cup broken by, 55.
iron converts, into steam.
132, 133.
melts sugar, 191.
soon freezes, 108,
how heated, 100.
hydrogen and, 184
image in, inverted, 437,438*
rain, not salt, 191.
smells badly, 190.
soft, 189.
razor dipped in hot, 56.
running, 191.
pure, 290.
runs out of the kettle spcut,
117.
salt, 188.
sea, brackish, 191.
latent heat in. 111.
less subtile than air, 86.
melts salt, 504.
sugar, 504 .
milk boils sooner than, 107.
not so hot as land, ^0.
of a river feels warm in win
ter, 419.
oil prevents freezing, 96.
particles of hot, ascends, 101,
pipes burst in frosty wea-
ther, 415.
ponds of, evaporated, 127.
pot of, in a saucepan, 119.
produces a sensation of co
85.
pump, hard, 187, 188
shallow, soon freezes, 419.
spilled on a table cloth, 505
simmers, 1 13.
soapy, lathers, 321.
soda. 217, 218.
sodium and, 184.
soft suitable for washing, 19ft.
INDEX >
557
Water, spring, cool in summer, 94.
sparkles, 211.
slagiianl pu'refies, 290.
full of worms, 290.
Watering the streets cools Ihem, 124.
WaXj 198.
melted, hard when cold, 107.
softened by heat, 136.
Waxing thread strengthens it, 522.
Wsst wir.ds in Atlantic Stales gene-
rally dry, 350.
fiel clothea conduct lightning, 28.
give us cold, 122.
in a thunder storm, 28.
earth promotes evaporation, 124.
feel cold, 122.
finger feels cold, 121.
kindling will not light a fire,
235.
summer, 125.
weather oppressive, 368.
rarely precedes thun-
der storms.
wheels, 128.
Wheels constantly wet. ^■23.
White, accidental color of, 483.
dress cool, 148.
fire, how produced, 518.
lead, 263.
of egg clarifies coffee, 528.
skin blisters, 158.
Wick, candle, 221.
long bent, 259.
red hot kindled, 252.
smouldering, rekindled, 251.
Will-o'-the-wisp, 226.
flies from us, 227.
Wini, 336.
accelerates evaporation, 125.
against the sides of a chim-
ney, 74.
always in motion, 336.
cause of, 336.
changes of, affect clouds, 357.
eloud-.5 affect the, 342.
cold, 154.
course of, 342.
dissipates fog, 411.
does not always blow one
way, 339.
dries damp linen, 350.
expansion of air, causes, 349.
forests prevent the access of,
196
fcnerally cold, 355,
ills and mountains affect,339.
in the chimney, 51.
47*
Wind, lightning followod by, .9.
linen dried by, 125.
oc<"an affects the, 340.
sometimes brings rain, 353.
velocity of, 355.
Winds absorb clouds, 359, 360.
blow regularly. 3-12.
up cloud. ^, 3&3.
chansre the shape of cL ad»,
360.
drive away clouds, 383.
dry, 341.
increase the bulk of clo« la,
360.
north, generally cold, 351.
dry, 351,
south, ofenerally warm, 351.
west, m Atlantic states dry.
350.
which blow over water rainy,
351.
Windy weather c )ld, 90.
Wind-mill, sails / /, 512.
Window blazes at sun-set, 438.
glazipr mending, 10.
rattling of, 486.
reflects noon-day sun, 438,
Wine ca'ks, old, offensive, 318.
stain removed, 522.
turns sour, why, 320.
Wire gauze, flame will not pf&a
through, 222.
Wisdom of God manifested, 91, 93,
128. 348, 380, 382, 417, 422.
Wooa. bad conductor of heat, 60.
blazes when very near the
fire, 244.
burns longer than paper, 234.
decay of, 212.
prevented, 291.
decomposed by heat, 137.
dry burns better than green,
48, 235.
snaps more than green, 48*
green snaps little, 48.
latent heat developed from,
165.
paint preserves, 97.
paper burns more readily than
233.
pores of 47.
porous snaps, 47.
seasoned, how, 291.
sparV^ of fire burst from, 47.
two )ieces burn better thai
oi v , 238.
558
INDEX.
A ool, fur bet ween ihe ^bres of, 89.
war Hi. 31>«.
Woolen OH rp^^t n bad conducior of
hr;it.
kenle holder, 95.
preve Us heal from e.«cap-
used for clothing, 87.
Work produces hunger, 312, 313.
f^GTit 5»f*fiflac!org of heat, 80
Y.
Yeast, 279.
Converts m?»It into beer. 280.
effecis of upon dou<;h,2^^3.
fe wee t won, 280
in prnpe juice, not needftt'
278.
used in brewin?, w^Tf 260
Yellow flame bright, 251.
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