REPORT
y
J. J. ABERT,.
IN REFERENCE TO THE
CANAL TO CONNECT THE CHESAPEAKE AND OHIO CANAL
THE CITV OF BALTIMORE.
VVASHINOTON:
I'KINTKI) liY OAI.EH AN1> 8EAT0N.
1838.
ar.y or railï^ay ECOKONíiCit.
Vi'MHINeiTO«. o. c.
¿L,á.. 3,6-^3
J if. -^S", 13 [ ^
REPORT.
To his Excellency T. W. Veazey,
Governor of the State of Maryland.
1. In consequence of the application of your excellency, dated the
23d of April, 1S3S, to the honorable Secretary of War, I was direct¬
ed to receive your instructions, and to carry them into effect. These
referred to a survey of a route for a canal to connect the Chesapeake
and Ohio canal with the city of Baltimore, and will be found more
particularly expressed in two of a series of resolutions passed by the
Legislature of the State of Maryland, in March, 1838, in the follow¬
ing words ;
" Resolved, That the Maryland Canal Company are entitled to no
subscription on the part of this State, under the provisions of this act of
the Assembly, unless they will agree to locate the canal from the Chesa¬
peake and Ohio canal to the city of Baltimore by the most northern
practicable route of the routes by the valleys of the Monococy and
the Patapsco, or by a route diverging from the said Chesapeake and
Ohio canal, at the mouth of Seireca river, exclusively within the lim¬
its of this State, provided such route be found practicable with duo
supply of water."
" Resolved, That the Governor be, and he is hereby, authorized to
direct a survey tobe made of the aforesaid routes, so that the prac¬
ticability of constructing the said canal, by either of the said routes,
may be ascertained at as early a period as possible ; and report the
same to the next General Assembly."
2. From the foregoing it will be perceived that the locality of the
routes of the canal is prescribed ; that, whichever route should be adopt¬
ed, it must be exclusively within the limits of the State of Maryland ;
and that it should be "practicable with due supply of water." .
3. Several surveys having already been made in reference to the
same object, by engineers of much reputation, the possibilities of the
case had become determined; so that my attention was, in the outset,
limited, and relieved from the va.gue action which would have en¬
sued of an unknown and unsurveyed region. These previous sur¬
veys confined those possibilities to three routes, usually known as—
1. The IVestminsler route.
2. The Linganorc route.
3. The Seneca route.
There is a fourth also-^thc route through the District of Columbia
to Georgetown ; but as this is not "exclusively within the limits of
the State of Maryland," it could not be made a subject of investiga-
4
(ion, as it fell without the locality of operations which the Legisla¬
ture had directed to be observed.
4. Of the routes named, the first had been so unequivocally reject¬
ed by the engineers who had preceded me, that I did not consider it de¬
serving of a survey. The second had also been rejected, from its
presumed deficiency in water ; but as it was the only route connect¬
ing with the valley of the Monococy that had a bare possibility in
its favor, and as the Legislature evidently had this valley in their con¬
templation when the resolutions quoted were passed, it appeared to
me proper that it should be surveyed. It has accordingly been done.
5. The third is the route by the valley of the Seneca. Upon this,
and this alone, have the engineers who preceded me differed in
opinion. One, Mr. Trimble, declaring it to be adequately supplied
with water ; tlie other two, Messrs. Fisk and Hughes, being equally
decided that the supply was insufficient. It was this difference of
opinion which gave rise to the legislative action, authorizing renewed
surveys, and which induced your excellency to designate me as a
sort of umpire in the case, with authority to make whatever addition¬
al investigations and surveys might be considered necessary.
6. I will not deny that I felt the embarrassment of my position.
With all of these gentlemen I had been for years on terms of the
most friendly intercourse. All possessed great reputation. Mr. Trim¬
ble, a distinguished graduate of the Military Academy, had been, for
many years, superintending highly important railroad operations,
possessing and deserving the confidence of his employers. Mr. Fisk
had been equally long on those of canals, and was then, and had
been for some time previous, the chief engineer of the Chesapeake
and Ohio canal. Mr. Hughes, his associate, it was well known, was
a gentleman of scientific knowledge, having passed through the courses
of the Military Academy, of a vigorous and inquiring mind, and had
been for many years employed by the United States as a civil en¬
gineer, in which capacity his reports, plans, and estimates, on various
subjects connected with his profession, bear ample testimony of his
abilities. To agree with both sides was impossible ; to differ with
some one, therefore, must be the inevitable result of an honest opin¬
ion.
7. On entering upon the duty, it was soon found proper to extend
the surveys much more in detail than had been at first contemplated,
as well to gather all facts of importance bearing upon the question at
issue, as from the difficulty of accurately connecting ours with the
labors of our predecessors, from the deficiency of permanent marks.
But I hope by this course that all necessary matter has been collect¬
ed, so that the question will be satisfactorily settled.
8. Your excellency was duly apprized, in the outset, that it would
not be in my power to give much personal attention to the surveys.
These were, however, committed to able hands—Mr. Thomas J. Lee
being at the head of one party, and Mr. J. P. Kirkwood of the other.
The intercourse between these gentlemen and myself has been fre-
quent, personally and by letter ; so that no benefit that could be de¬
rived from my advice has been withheld.
9. Recurring to your excellency's letters and instructions, and to
the resolutions of the Legislature, as well as to the general principle
which governs in all canal cases, it will be seen that the point at issue
is " the due supply of water and that this is, in fact, the sole point
upon which I am required to report.
10. It will involve a reasoning upon the general question of the
quantity of water consumed or expended by canals, upon which it is
evident that one might indulge oneself in a long essay, but of matters
familiar to the profession, already treated with great ability by en¬
gineers, and which, in consequence, would leave me, at most, only
the subordinate duty of repeating, in my own language, that which
has been so much better said by others. To the professional man,
therefore, I shall probably say nothing either new or interesting ; and
were I writing a report for his perusal only, I should probably limit
myself to a few results and deductions ; but writing, as I am, for the
judgment of the Legislature, which is not professional, I shall, of ne¬
cessity, be forced into the discussion of details familiar to the profes¬
sion, but not so to those for whom I write. And, to be the better ap¬
preciated by these, I shall endeavor to express myself in that simple
and plain language which, if it should not convince, will at least be
understood.
11. The water required for a canal ought to be sufficient to supply
an expenditure on the following accounts ;
1st. To fill the, canal throughout its whole, extent.
2d. To compensate for losses from evaporation.
3d. To compensate for losses from filtration and absorption.
4 th. To compensate for losses from leakage at the lock-gates.
5th. For the uses of the locks, according to the demands of the
trade upon the canal.
6th. Jlnd for the waste arising from accidents and negligencics.
12. I mean to treat of these several causes of expense of water as
briefly as a clear exposition of each will admit ; and shall endeavor,
in that way, to establish certain general rules, which may be after¬
wards easily applied, by any one who has a knowledge of the rudi¬
ments of arithmetic, to the particular project under examination.
13. But, as accessory structures to canals, feeders and reservoirs
have to be made, some facts and reasonings in reference to losses of
water in these, and of tiie means of filling reservoirs, will likewise
have to be submitted.
14. 1st. The quanlily required lo fill the canal.—This, of n-eces-
sity, depends upon its dimensions—length, breadth, and depth and
is obtained by resolving tbem into the cubic unit of water used in
the calculation. The result is, however, always below the truth ;
because, while the process of filling is going on, losses from evapora¬
tion, absorption, and filtration are taking place. In strictne.ss, there¬
fore, these should be taken into account,particularly in ca.scs in which
tí
the supply not being abundant it would be dangerous, from the delu¬
sion probably consequent, to neglect any item of loss.
15. 2d. Losses from evaporation.—Much has been written on
evaporation by authors,asa philosophical question ; but it is evident,
on an examination of their experiments, that the result obtained can
form no good data for calculating losses of water from a similar cause
on canals. What just comparison can be made between the circum¬
stances of experiments in a laboratory, and those which exist on a
canal ? The one, exposed to all the changes of temperature in differ¬
ent parts of its surface ; to commotion in its waters ; to continual vari¬
ations of humidity in the adjacent bed of air ; and to greater or less
currents of air passing over its surface. From all these, the experi¬
ments of most writers on the subject have been comparatively free,
and, of consequence, their results are not safe data in reasoning upon
evaporation on canals. One can easily be satisfied of this by refer¬
ring to the article on "evaporation" in Hutton's Mathematical Dic¬
tionary, and by reducing to arithmetical results the proportions which
some have endeavored to establish between evaporation and rain,
and the reverse. These proportions, if true in nature, can be so only
in pecidiar localities : as, for instance, Dr. Brownrigg, in his treatise
upon making salt, states the evaporation in some parts of England at
73.8 inches during the months of May, June, July, and August; and
at 140 inches for the whole year ! To what conclusions would these
facts lead us, were we to apply them in the proportions given by
authors between evaporation and rain ?
16. Also, INIr. Dalton found that from the current occasioned by
merely raising a window, the evaporation of his experiments in the
room in which they were made was increased fifty per cent. ! Surely
such results are not to be applied to the condition of water in a canal.
17. That settled proportions exist between evaporation and rain,
is not what I mean to dispute ; but to determine these for an exten¬
sive district of country requires numerous and long-continued obser¬
vations in many places, under circunrstances brought as nearly as
possible to those which actually exist in a state of nature. Propor¬
tions can, without doubt, be correctly established between the evapo¬
ration of a laboratory, and rain as it naturally and actually occurs.
But, then, what are tliose proportions? Merely such as exist in the
evaporation of a laboratory on the one side, and rain in a state of
nature on the other ! Now, for a canal, we want the evaporation
of a state of nature. That determined at salt-works, where artificial
heat is not used, but merely the evaporation from large and exposed
vats by the air, is most probably the nearest approximation to what
actually occurs on a canal, diíTerences of climate and temperature
being considered.
18. I have been furnished by my enlightened friend. Dr. Harlan
of Philadelphia, with some results of evaporation in that city. But
these are liable to the objections already stated ; there is no paral¬
lelism of circumstances with those of a canal, and therefore there can
be no just application of residts.
I
19. I am convinced that losses on this account on canals much
exceed the laboratory rules by which engineers have been governed,
and that this has often been the unexpected cause of disappointment
in the quantity of water anticipated.
20. Evaporations are much influenced by climate. That of Eng¬
land being generally colder and more moist than the climate of
France, evaporation in the latter country should be greater than in
England. In our country, particularly in the Middle States, we have
more hot, dry, clear, and windy weather than in France ; which
would justify the inference of a greater evaporation with us than in
Europe. We have also more rain in the course of the year ; that is,
a greater quantity falls in fewer rainy days.
21. From the considerations heretofore given, I am disposed to
consider the greater part of these rates of evaporation as inapplicable
to the condition of water in a canal.
22. The celebrated engineer, Gauthey, in his interesting work
upon canals, appears to rely in this question upon the experiments
made by Mr. Cotte at Montmorency, near Paris.
The method pursued in making the experiments is not given by
Gauthey, but the result is, that the mean evaporation per year
amounts to 41.575 inches ; and that, for parts of a year, (vol. 1, 2G6,)
the results were : for November, December, and January, 1.338 inches
per month ; for March, September, and October, 3.189 inches per
month ; and for the six remaining months, 5.315 inches per mouth.
These were probably the results of some one year, as they do not
agree with the average per year before stated. The same observer
also found the rain to amount to 18.662 inches per year: from which
he concludes that evaporation is to rain about as 20 to 9, or as 5 to
2.25.
23. Dr. Halley flxes the annual evaporation at London at 48
inches ; and, on an ordinary summer's day at ^-^ths of an inch ; and
the proportion between that and rain as 5 to 3. The experiments of
Dalton and Hoyle make it about 4.41 to 3.
24. By particular observations of the engineer, M. Finn, on evap¬
oration during the suspended navigation f chômage) on the Langue¬
doc canal, (And. p. 223,) he determined that the partial depression,
owing to evaporation, was two-fifths of the total depression of the
water held in reserve ; and that, during 320 days of navigation, the
mean height of the prism of water raised by evaporation from the
surface of the canal was 812 millemetres, or 31.969 inches.
I understand this to refer to the actual exhaustion from the surface
of the canal, exposed, at the same time, to whatever rain might fall
upon it.
25. The quantity held in reserve, of which two-fifths were lost by
evaporation, is not stated; but, if it were, as I suppose it to be, the
full prism of water left on the closing of the navigation, the loss would
then be one-fifth of that prism in 20 days; which would be equiva¬
lent to one prism in one hundred days, or three and one-fifth prisms
during the 320 days of navigation, from this cause alone.
H
26. But it was said that the total abasement of the waters in the
canal, on account of evaporation, was 31.609 inches in 320 days.
Now, taking the rain as given (And. p. 237) for Trebes, a central point
of the canal, and for a moderately rainy year, as stated at 697 mille-
metres, or 27.44 inches, or 24.06 inches for the 320 days, we have the
amount of rain which fell upon the surface of the canal, and restored,
to that extent, losses from evaporation. But as, notwithstanding the
rain, these losses were 31.969 inches, the two sums may be taken as
the total evaporation, or 56.03 inches. As the time of 320 days in¬
cludes that of filling, opening, and closing the canal, I presume ten
months may be taken for its actual navigation ; this would give a sum
of 5.60 inches for the average loss, by evaporation, per month.
27. We have seen that, for an ordinary summer day, for the cli¬
mate of London, Doctor Halley states the evaporation to be two-
tenths of an inch, which would be six inches for a month of 30 days.
Now, taking our climate into consideration, where we have no cool¬
er, and many hotter, days than an ordinary summer day in England,
from the middle of April to the 1st of October, and the actual circum¬
stances to which water in a canal is exposed, we believe but few en¬
gineers will consider the evaporation stated in the deduction just made
as beyond the reality for the climate of the Languedoc canal, and still
less so for the one to which our observations may be applied.
28. But further : In a table of the depth of rain from observations
made by Mr. Brantz, of Baltimore, we find the mean annual fall of
rain, in a series of eight years, to have been 39.89 inches, (Rep. Board
of Engineers, p. 52.) Applying Doctor Halley's rule of proportion
(23) to this, it will give a mean evaporation of 66.48 inches. Then
applying the rule resulting from the observations of Dalton and Hoyle,
(23,) the mean evaporation will be 58.638 inches. And now, to the
same quantity of rain, applying the proportion of Mr. Cotte, (22,) the
mean evaporation will be 88.64 inches. We have already stated our
opinion that evaporation was greater in this country than in Europe.
All the causes of the phenomenon are knorvn to be more active with
us, and we have seen that the results from the proportions given be¬
tween rain and evaporation add their proofs to the opinion. Direct
observations have been made in but few places within my knowl¬
edge.
29. Mr. Sullivan, in his report upon the Chesapeake and Ohio ca¬
nal, states the annual evaporation at Salem (Mass.) at 56 inches;
and the board of engineers, in their report upon the Morris canal, in
1823, state that Mr. S. Williams had ascertained the evaporation at
Cambridge (Mass.) to amount, annually, to 56 inches. Applying
this result to the climate of the Morris canal, the board conclude to
adopt 51 inches for its evaporation. " But, as the canal can be navi¬
gated only during those eight months of the year (from April to De¬
cember) when the evaporation will be the greatest and the rain the
least, and as the instruments in use for measuring evaporation must
always give results below the truth, from their not being exposed to
wind and currents of air, we therefore adopt the whole sum of 51
9
inches as expressive of tlie maximum loss of water by evaporation."
Now, as this was for a navigation of eight months' duration, the loss
hy evaporation was assumed at G.37 inches per month.
30. We have seen that the observations at Montmorency (22) gave
an evaporation of 41.57 ; from which, if we deduct 2.66 for the two
winter months, it will leave 38.91 inches for the remaining ten months.
And we have also seen that the actual canal evaporation in that
country amounted to 56.03 inches, (26 ;) from which one may deduce
a ratio between the evaporation of the laboratory and that which ex¬
ists on a canal : this will be found to be as 1 to 1.44. It will proba¬
bly not be considered unreasonable to take the mean annual evapo¬
ration of the climate of Maryland, within the region of the contem¬
plated canal, as equal to tha' of Cambridge (Mass.) Then, if we
apply to the Cambridge evaporation (29) the proportion just ascer¬
tained, we may find the probable evaporation of tlie climate of our
canal, tor water exposed as it is in acanal. This will be 80.64 inche.s.
Such is the mean annual evaporation, which, if we were to calculate
for los.s from that cause, we should use for a canal near Cambridge
(Mass.) It could not, therefore, be expected that we should use less
for one in the vicinity of Ualtimore. The average would be 6.72
inches per month, and 67.20 inches for the ten months of navigation.
31. If our reasoning be correct, then, as a general rule for a climate
like that of Baltimore, evaporation from large and exposed .surfaces
similar to those of a canal is to rain as 2.02 to 1.
32. We are fully aware that our reasoning upon this matter is
Sjjeculative. The data being of that character, the rea.soning must
partake of the same. Our object i.s not to discredit the use of such
rules, but to show the caution with which they should be applied.
33. But no rule of this kind can be relied upon: if true, it is hut
for some limited locality. Every proportion given by any authority
is thrown into a kind of ridicule by the facts of some localitic.s. In
Cavallo's Philosophy, page 374, it is stated that, from accurate ex¬
periments made by Doctor Dobson, during four years, he determined
the annual evaporation from the surface of the water at Liverpool to
be 36.78 inches; and in page 378, the annual fall of rain at Liverpool
is reported to be 37.48 inches. Now, taking either of these elements
for calculation, we can readily perceive into what error we should
fall, by the ratio or proportions given by any author between evapo¬
ration and rain. " The annual quantity of rain," says Doctor Dob.sori,
"is a very uncertain test of the moisture or dryness of any particular
season, situation, or climate. There may be little or no rain,and yet
the air may be con.stantly damp and foggy; or there may he heavy
rains, with a comparatively dry state of the atmosphere."
34. It is, then, also, a very uncertain test of the evaporation, or the
evaporation of the rain. In so important a matter as a canal, the
water shoidd not be obtained by inference.
35. FiUraiions.—These are the result of a general law of nature,
acting with greater or less force, according to the peeiiliaritie.s of soil,
but acting unceasingly and uriiversnlly; often at great dejjths, as is
i>
10
observed in mines and caves ; in great force, as is known from the
absorption of entire rivers ; through apparently impervious strata, as
has been observed through more than forty feet of the calcareous
rock in which are cut the catacombs of Paris ; and through carefully
constructed masonry, as is to be seen on passing under our various
aqueducts. The idea, therefore, of making a canal which should be
exempt from this general law, would be an absurdity. The effort of
the engineer is to lessen its activity and to supply the losses which
it occasions.
3Ö. Gauthcy, in his work on canals, (p. 267,) gives it as a general
rule, that one may assume for filtration about double the amount of
evaporation. This opiirion follows immediately subsequent to his
statement of M. do Cotte's rate of evaporation. But from the re¬
marks which we have made upon losses from evaporation, and from
the facts we have given, the uncertainty of such a rule must be evi¬
dent. It appears to our judgment that it cannot be otherwise than
incorrect. There are no acting causes common to both, so as to pro¬
duce any uniform relation between them. Filtrations are the result
of the soil through which the canal passes, and the greater or less
eare bestowed upon its construction. Now, it is clear that these have
no connexion whatever with the causes of evaporation, and, there¬
fore, no rule of proportion can be assumed as existing between them.
The evaporation in the same locality would remain the same, whether
the canal were carefully or negligently made, or whether the soil were
close or permeable. Such a rule can, therefore, be applied to a par¬
ticular case only, and to that with propriety, merely because it has
been found to be true from actual observation.
37. Most of the rules of French engineers have been derived from
observations made on the Languedoc canal. Now, this canal, it is
admitted by all who have written upon it, loses less from the usual
causes of waste than any other known canal in the world, owing to
the care which had been infused in its construction, and the vigilance
and intelligence with which it is superintended. Rules derived from
such a source, should, therefore, be received with great caution. They
led the great engineer I have just named into error in his project of
the canal dn Centre, and would have resulted in a complete failure,
if sources of supply of water, in addition to those at first relied upon,
had not been at command.
38. But even in the Languedoc canal I have not been able to find in
my investigations any data to justify the rule, as the annual loss from
filtration given by authors much exceeds the amount which would be
derived by calculation from double the evaporation. Some limited ex¬
periments on parts of the work would seem to sustain it ; but these
appear to me to be wanting in many facts to justify a general rule.
There can be no doubt, however, that all the phenomena connected
with canals have been observed with extreme care on this, the boast
of France and the pride of her engineers. It is esteemed by the lat¬
ter as one of the most interesting works of that kind. We shall have
11
frequent occasion in our remarks to refer to facts connected Avith its
history.
39. It is, among canals, perhaps the only one Avhich furnishes dis¬
tinct results of losses by filtration. The usual method is to combine
these with those of evaporation in one common result, which an ■
swers all general purposes in forming a judgment of the supply of
wafer required. I3iU there can be no doubt, if observations on these
and every cause of loss were separated and made distinctly, it would
lead to much greater accuracy, and would present in a more striking
light the great saving of water which would ensue from the introduc¬
tion of a better system of construction. Where canals have been
made in our country, the supply of water has generally been abun¬
dant, and the demand for it on other accounts so limited, that we have
been able to aíTord the waste of large quantities ; it being a much
cheaper plan than to save it at a great enhancement of cost.
40. Elements to which capital can be applied are not among our
deficiencies, but rather capital in order to bring those elements into
activity. This last is both scarce and in great demand ; it has, there¬
fore, to be used with the most vigilant economy, llcnce has arisen
with us a system of engineering which may be emphatically called
" the American system," which looks less to posterity than to our
own time, and presses with extreme eagerness to an immediate and
profitable result. It is a system in harmony with our condition, based
upon common sense, and is the only one which, in our circumstances,
can be pursued to any extent in the development of our immense but
rather latent resources. While we therefore admire and leant from
the more perfect structures of Europe, we must yet forbear a rigid
imitation of them, as there are but few cases in which a difierent
course would not lead to the bankruptcy of all concerned.
41. The method of engineers, generally, to combine these two
causes of loss of water, and to introduce but one item into their cal¬
culations for both evaporation and filtration, will oblige us to use re¬
sults of that kind, as well as distinct statements of filtration.
42. Hticrne, in his History of Canals, (p. 266,) after detailed state¬
ments of the water consumed in different portions, while he admits
the calculations to be but approximative, comes to the conclusion that
during ten months of navigation the Languedoc canal lo.ses by its
filtrations alone (deduction being made for Ios.ses from evaporation)
about eight times its pri.sm of water, or eight-tenths of its prism per
month. Now, if we were to reverse the rulo of M. Gaulhcy, and
deduce the evaporation from the filtration, (and if the rule be correct
it will admit of such an application,) the loss during the ten months,
from the two causes combined, would bo twelve of its prisms of
water, or prism per month, which would give an evaporation
vastly exceeding that which engineers have used. And were wc, on
the contrary, to take the accredited rate of evaporation, and from
that calculate the filtration, the rc.sult would be much below that
which, from experience, actually takes place.
43. But the difierent parts of the canal observed, show great dif-
12
fereiices iii the ijuaiility lost by filtratiou, while there is no reason to
believe there could have, been much, if any, dilTcreuce in the evapo¬
ration. The latter quantity, therefore, if used as a basis for calcula¬
tion, would have led to great error. The rule, then, of taking twice
the given evaporation to determine the filtrations, is, in our judgment,
extremely unsafe. We will exemplify it farther.
44. The prism of one mile of the Languedoc canal is about 64,207
cubic yards. We have seen that it loses by its filtration eight-tenths
of this per month, or an amount of 51,365 cubic yards. The surface
of one mile is 48,644,893 inches. Now, the period of suspended
Jiavigation being in the winter, when the evaporations are very small,
and inay be supposed nothing, we will apply the whole of the mean
annual evaporation of De Cotic to the ten months of navigation.
This being 41.5 inches, would give for the ten months an amount of
43,269 cubic yards, or 4,326.9 cubic yards per month for the evapo¬
ration. The filtrations, being double this amount, would give 8,653.8
cubic yards. Dut we have seen that the amount, by actual observa¬
tion, is equal to not less than 51,365 cubic yards. If, therefore, we
were to rely on such a rule, it would lead us into shocking error.
45. Still less can we rely upon the rule of the engineer, Ducros,
given by Mr. Sullivan in his report, (Ducros, however, quotes it as
the opinion of the engineer Chausade,) of one and a half times the
evaporation for the amount of filtrations. That these celebrated en¬
gineers, Gauthey and Ducros, may not have had facts on which to base
i heir opinions, we do not pretend to dispute ; but they must have been
isolated facts, under some singular circumstances, and not adapted for
a general rule. We can easily conceive that during periods of ex¬
tremely dry and hot weather, with water very low in the canal, fil¬
tration would be much smaller than usual, and evaporation greater.
The sides and bottom of the canal having been, from long use with
a full volume of water, well compacted, and the interstices closed,
from the reduced pressure arising from a small volume of water, but
little could pass by filtration, while all the causes of evaporation were
acting with increased intensity.
46. But we have seen that this canal loses, during its ten months
of navigation, eight of its prisms of water. (42.) We must suppose,
also, that it contains a prism when its navigation is closed. Now this
prism let into the canal during its period of navigation, must be lost
also before the subsequent two months have passed; and these being
months of little or no evaporation, it must be lost by filtration. The
canal then actually consumes by its filtrations, for its ten months of
navigation, nine of its prisms of water, or nine-tenths of a prism per
month. The prism of this canal for one mile being 64,207 cubic
yards, its loss, therefore, is 57,786.3 cubic yards per month, or 1,926.2
per day, or 80.21 per hour, or about 36.09 cubic feet per minute, from
its filtrations, for every mile. The evaporations by the rule of M. de
Cotte were found to be 4,326.9 cubic yards per month, (44;) which,
treated in the same way, would yield 2.7 cubic feet per mile per
minute. The total loss, therefore, on this canal, from evaporation
13
and filtration combined, is 38.79 cubic feet per mile per minute. But
if we take the evaporation of M. Finn, of one-fifth of a prism in 20
days, (25,) the total loss from the two causes combined will bo about
48 cubic feet per mile per minute.
47. .We have gone into these details, because it was satisfactory to
know what that canal, which, as is. generally admitted, loses the
least of any known canal, actually lost from the causes stated. But
its loss being a minimum, rules derived from it would certainly be
very unsafe guides to follow in judging of other cases, however
valuable they may be in indicating the advairtages to be obtained
from a careful construction.
48. The board of United States engineers, in their report upon the
Chesapeake and Ohio canal, (see Rep. p. 39, 40,) assume as data for
their estimate, the consumption, of once its water prism per month,
on account of losses from evaporation and filtration.
49. From experiments made on the Erie canal,and communicated
to me by that distinguished engineer, Mr. J.*B. Jervis, (to whom I am
also indebted for other highly valuable commutiications,) it would
appear that the least loss, from observations made at various places,
was 100 cubic feet. This was irot the measurement of loss from a
distinct cause, but from all united—leakage of locks, evaporation,
and filtration. The dimensions of this canal are, 40 feet water sur¬
face, 28 at bottom, and 4 feet deep ; which give, for it.s prism of one
mile, 26,595.5 cubic yards. The loss of 100 cttbic feet per mile per
minute is equal to 160,000 cubic yards per mile per month ; or, sttp-
posing the navigation to continue for nine months, (in that climate,)
the total los,s would equal about 54 times its water prism per year ;
adding to this the loss of the prism in the canal at the closing of the
navigation, gives a total loss of 55 of its prisms of water, for all causes,
except the demands of the locks for its trade.
50. This consumption of water is certainly very great. The com¬
missioners, in their annual report of January, 1834, make the follow¬
ing remark :
" The commissioners are inclined to the opinion, that, with proper
care in guarding against the waste of water, 100 cubic feet per mile
per minute^ for leakage, filtration, and evaporation, (all causes of con¬
sumption,) would be a safe estimate for the western and middle sec¬
tions of the Erie canal ; but it is believed it would be found, on a
careful examination, that a much greater quantity would be neces¬
sary on many parts of the eastern section, where the soil is more open,
the levels shorter, and the locks more frequent."
51. Shallow canals lose more than deep onc,s. This is a point now
so well settled by experience, that facts need not be adduced to prove
it. We mean, more in proportion to their dimensions ; that is, in pro¬
portion to their filtrating stufaces. In our own country we have an
example of a deep canal, (the Chesapeake and Ohio canal,) the depth
of which is six feet.
52. Mr. Fisk, the chief engineer of that canal, after repeated and
careful observations over an extent of about 40 miles, represents it.s
14
loss, on account of its evaporation and filtration, at GO cubic feet per
mile per minute. Its dimensions are 60 feet at the water surface, 32
feet at bottom, and 6 feet deep, which give, for one mile, a water prism
of 53,973 cubic yards. And as this canal loses 60 cubic feet per mile
per minute from evaporation and filtration, it will amount to 96,000
cubic yards per month per mile, which is more than one and three-
quarters of a prism.
53. Now, if we suppose the navigation of this canal to continue
during ten months, and add to the loss just stated that of the prism
of Avatcr left in the canal, it will make 18i prisms of water for its
navigable year.
The observations of Mr. Fisk were made upon that part of the canal
between Harper's Ferry and Seneca, which has been the longest in
use. Much of it also passes through low ground, and may therefore
be considered as the drain of the adjacent high grounds ; and where
exposed to the causes of active filtration, it was puddled with great
care. On these accounts*! conceive its loss may be fairly considered,
under our system of construction, as a minimum ; and that the safer
rule for a general estimate, on account of losses from filtration and
evaporation, would be two prisms per month. Its actual loss being,
then, 1.85 prism, our safer rule adds 0.15 of the prism of one mile
per month, which would increase the stated loss per mile per minute
2.25 cubic feet ; or make the whole, exclusive of the prism left in the
canal on the closing of the navigation, 6'2.25 cubic feet per mile per
minute. This prism, left in the canal at the closing of navigation, is,
as has been shown, equal to 53,973 cubic yards, (52,) for one mile.
As its loss is for the whole ten months, it would be 3,374 cubic feet
per mile per minute, making the total loss per mile per minute equal
to 65.624 cubic feet.
54. Leakage at locks.—It is highly important that losses from this
cause should be considered in every estimate of water for a canal.
Unlike filtrations, these are least at first, and increase as the canal is
used. The water passes under the miter sills, between the gate-posts
and the hollow coins, between the gates where they meet, from the
valves, and under the bottom of the gates. All these arc closer when
new, and, from gradual wear and other causes, open more and more
every day, until repairs, and, idtimately, new gates become necessary.
It is also worthy of remark, that in a series of locks, all depending
upon the same source for supplies of water, it is the lock of greatest
leakage which must be considered. If the second lock of a series,
for instance, leaks more than the first, then the leakage from the
first will not keep up the intermediate level, as more than it sup¬
plies is drawn off by the second lock. So, also, if the lock of the
greatest leakage be the third or fourth. And when many locks are
dependent upon the same source, it would be absurd to suppose that
each was constructed, and its gates fitted, with the same care. So
that a slight accident to any one of a series, not sufficient to justify
15
the stopping of the navigation for repairs, increases the leakage,
which the summit has to supply. On these accounts, there can be no
average of the leakage from many locks as the basis of an estimate,
or as proof of what a canal loses from this cause. It must lose that
which leaks from the lock of greatest leakage, and cannot lose less.
Lo.sses from this cause, in long levels, are not so serious nor so sen¬
sible to observation as in short ones. In these last they are both soon
observed and felt.
55. Andreossi (p. 223) reports the result of observations on this
account, of loss experienced on the Languedoc canal, by the engineer,
Mr. Finn. These observations were made upon many locks, and
the mean of the whole is staled to be 10 litres, or 610.28 cubic inches
per second. The objection to this result is, that it is a mean of the
whole, instead of being the loss from the lock of greatest leakage ;
which, as we have already shown, is the actual loss sustained.
56. Ten litres per second is equal to 30,514 cubic feet per day ; or,
for the two locks, one at each end of the summit, 61,028 cubic feet,
(our measure ;) which, in a month of 30 days, would amount to
1,830,840 cubic feet, orto 67,808.88 cubic yards, (say 67,809;) which,
for the ten months of navigation, would be 678,090 cubic yards.
57. The size of the locks of the Languedoc canal is very great, and'
their curved sides give an unusual cubic content. Owing to this
form of construction, (bad in itself, and long since abandoned,)
we cannot well make a comparison of its prisms of lift with the leak¬
age of its locks.
58. There is another reflection proper to be made. All other things
being equal, the leakage must be in proportion to the perpendicular
height of tlie water, or to the pressure to which the orifices or open¬
ings are exposed ; and also the leaking surface (that is, the joints)
must be in proportion to the lift of the lock and the width of the gates.
59. These circumstances render the applications of observations
on canals of extremely doubtful propriety, where we are not fully
possessed of a knowledge of all influencing dimensions and causes.
Upon the same canal, the width of the lock-gates must be the same,
but the lift of the locks need not be, and often does vary considerably.
Now, in the very canal we have named, the second lock from the
sumrnit in one direction has a lift of more than 9 feet, while that of
the first is about 71 feet ; the ninth lock also has a lift of between 11
and 12 feet. It is clear, therefore, that the average from the leakage
of such variable lifts must give a false result (and false to a great
amount) of the absolute quantity really drawn from the summit to
supply the leakage of the locks, which, as we have before remark¬
ed, can never be less than that of the lock of greatest leakage. At
the opposite end of the summit, among the locks depending upon the
summit for its water, there is one of more than 12 feet lift. The
summit is therefore really subjected to the leakage from these two
locks of so great a lift. We will take the two extremes, of 7i and
12 feet, to illustrate our reasoning by an example.
IG
60. The discharge under the two pressures, Ih and 12 feet, being
to each other as the square roots of the pressures, are about as 27 is to
.25, or the discharge from tlie latter is about one-third more than from
the former; which would maire a loss of 904,120 cubic yards for the
ten months, by taking the lock of the greatest leakage.
61. Although we cannot make a just comparison of this loss with
the prism of lift of the locks of this canal, on account of the reasons
heretofore stated, we will see, however, what it would be if the sides
of the lock-chamber were a right line, and the chamber an oblong
square instead of an oval.
62. Taking the dimensions of the first lock from the summit, and
reducing its cube by straiglitening its sides, we shall find its lock-full,
or prism of lift, to be about 346 cubic yards. The corrected prism
of lift being then 346 cubic yards, (Gauthey, p. 48,) and the leakage
at the lock-gates being 1,130 cubic yards per day, it amounts to nearly
3i locks-full (prism of lift) per day for one lock. But the increase
of this leakage, on accouirt of the lock of greatest leakage, will bring
the amount to 1,507 cubic yards per day; or rather more than 4j
prisms of lift, or 8| for the two locks, one at each-end of the summit.
If our views of the case be therefore correct, this uncommonly well
made and carefully attended canal loses this last quantity daily
from its summit by the leakage of its locks.
63. Messrs. Fisk and Hughes, in their report of March 1837, (p 16,
17,) fix the leakage at each set of locks adjacent to the summit at 12
locks-full (prisms of lift) per day. This was the result of very care¬
ful observations upon the locks of the Chesapeake and Ohio canal,
made by Mr. Fisk, its chief engineer. All the locks of this canal are
about the same lift, and the same dimensions in other respects : i. e.
15 feet wide, with a lift of 8 feet. Now, as the workmanship of
these locks is probably the best in our country, and as that of other
canals ought to be as good, we may take them as evidence of the
degree of perfection to which we are willing to go in such matters,
or which we are able to atford. As we believe, also, that the gates
are as carefully attended to on this canal as on any other in our coun¬
try, its results are, on that account likewise, a good criterion. The
observations however, were made during a period of suspended
navigation, when the gates were closed with great care, and kept so
for several weeks, while repairs were being made. Mr. Fisk has
assured me that, in his opinion, the actual leakage of the gates when
in activity exceeds the amount stated, great as it may be considered ;
we have, therefore, the assurance of the chief engineer of the canal,
that it is less than that which really occurs to the canal when in use.
64. We have ourselves frequently, observed the leakage at the
locks of this canal, and we are satisfied that Mr. Fisk has not exag¬
gerated the loss. Twelve locks-full per day, for each lock, is half a
lock-full (prism of lift) per hour. Now, to bring this rate of leakage
more within the judgment of the general reader, and to enable him
to test it by what he may himself have observed on canals, we will
make a comparison in a shape in which the quantity will be more
17
readily comprehended tiiaii that of the rate of cubic feet per minute.
Half a lock-full per hour is 624 cubic feet per minute: the lock-cham¬
ber being 100 feet long by 15 wide, will give a superficies of 1,500
feet. Now, this rate of leakage would not raise the water in a lock
of this size more than one foot in twenty-four minutes, or half an inch
per minute.
65. This leakage is twice and a half as great as that of the locks on
the Languedoc canal. We acknowledge it to be great, but, as the
workmanship of the locks on the Chesapeake and Ohio canal is as
good, and the vigilance of those who attend upon them as active as
we have a right to expect for the canal in contemplation, we can see
no other correct course than to adopt, in our reasoning upon the wa¬
ter for that canal, the leakage just given.
66. The locks in the two cases—the Languedoc and the Chesa¬
peake and Ohio canals—are sufficiently similar in their dimensions to
attribute much of the difference of leakage to differences in the man¬
ner of building. One is the work of a government, the other of an
incorporated company ; one was built by the agents of a government,
the other by contractors ; with one, no expense in materials or skill
in execution was spared ; in the other, too generally, the lowest bid¬
der was taken, who must of course secure his own profit in the kind
of work and quality of materials. In works of this character, no sys¬
tem is so pernicious, or in the end so costly, as that of giving work to
the lowest bidder under the delusive expectation of saving. Good
work cannot be done for less than a just valuation ; and when bids
for less are made, they can result only in the ruin of the contractor,
if he be faithful, or to the prejudice of the work, if he be not. The
former is avoided with extreme care ; the latter more generally oc¬
curs; and its consequences are, enormous expenditures under the
head of "repairs," to which our public works are so frequently subject¬
ed, always exceeding the supposed savings on the accepted bids.
An intelligent and skilful contractor will not offer to do work for
less than its proper value ; the uninformed, the inexperienced, or the
unfaithful, may; and from the system pursued, in the hands of the.se
latter our public works are generally thrown. No boast is so replete
with false reasoning, so delusive to society, as that frequently made,
of having let work at prices much reduced from those of the engi¬
neer's estimate.
If the engineer be competent, his estimate is no more than a fair
cost of the work; then, if that work be let for Jess, it can only be to
the prejudice of the work.
67. Our works must also partake of the degree of skill and expe¬
rience in our mechanics, which is well known to be rather below the
standard required for similar structures in Europe.
68. On these accounts, therefore, as well as the necessity of econ¬
omy in first cost, it may easily be conceded that our canal structures
are not carried to that degree of perfection which is found in other
countries. By the way, upon this matter of economy in first cost it
may be well to say a word or two. It should not be understood as
3
18
meaning numbers of dollars, in comparing mile with mile, or lock
with lock ; but in the quantum of labor which the same amount of
money will command in the two countries. In our country, the wa¬
ges of mechanics and of laborers are so much higher than in Europe,
that the same amount of service cannot be obtained for the same
cost ; and, of consequence, works of the same cost in money must be
inferior, because of the less labor upon them. Unless this idea is
maintained, wo always deceive ourselves in making comparison
with similar works in Europe. While, therefore, I readily admit
that the work of the Chesapeake and Ohio canal is probably the
best of that kind in our country, yet it may, however, be said that it
is inferior to similar works in Europe.
G9. We may, then, without violatioir of probability, place this dif¬
ference in the leakage of the locks to différences in the quality of the
structures; and we may, also, from the character of the work on the
Chesapeake and Ohio canal, assume its lock-gate leakage as a fair
basis tor estimates in our country.
70. But to return to the subject. Twelve locks-full (prisms of
lift) for the lock at each extremity of the summit, is 24 locks-full
per day. Each lock being 100 feet long, 15 feet wide, with a lift of
5 feet, will give 7,500 cubic feet for its prism of lift, or lock-full of
water. This will equal 180,000 cubic feet per day, or G,6G6.6 cubic
yards; which, for a month of thirty days, will be 199,999.8—say
200,000 cubic yards.
71. Accident may increase the leakage of a lock so much as to
make the process of filling it tediotis ; and yet the injury may not be
sufliciently great to justify the stopping of the navigation in order to
make repairs.
72. The leakage arising from the defective shutting of a valve
would increase the loss considerably beyond the amount we have as¬
sumed ; yet, it would not, in our judgment, be fair to embrace sucli a
case in a general estimate of leakage, while we are willing, however,
to admit its probability in the course of a season with some one of
the many locks that may be dependent upon the same source for
their supply of water. But, at the same time, the probability of such
accidents should not be disregarded by the engineer; and while he
cannot fairly include them in his estimate of the quantity of water
actually required, it becomes his duty to show a surplus in order to
meet them, or to point out the deficiency and its consequences.
73. Locks.—Muchhas been written upon locks, themannerin which
they should be arranged, and their lift, in reference to convenience
and to the water they consume. The general result of the whole is,
that the most favorable lift is from 7 to 8 feet ; that they should be
as far from each other as the nature of the ground will admit, and so
far as not to impede the navigation by the abstraction, from an inter¬
mediate level, of a lock-full of water ; avoiding,'if possible, aggregate
locks, or locks immediately adjacent to each other ; and, that among
a series of locks dependent upon the same source for supplies of wa¬
ter, the lift should never increase as they descend. It may decrease
19
advantageously, but this is a nicety belonging to the engineer in ar¬
ranging his plan. The illustration of all these positions would lead
to remarks purely professional, inapplicable to the object of the re¬
port, and therefore uninteresting. We shall on these accounts avoid
it, leaving what may be necessary, if any should be, to the particular
case which the plan may develop.
74. The simple question upon which it may be proper to say
something at present, is, on the supposition of well-arranged locks at
proper distances from each other, what quantity of water will the
passage of a boat require ?
75. Engineers have given various opinions on this subject: one
prism of lift, one and a half,' one and three-quarters, two—all de¬
pending upon the degree of presumed regularity in the trade. The
matter is familiar to them. We hope they will not suppose it our
object to instruct them on a subject upon which they are known to
be so well informed. We desire only to make it equally plain to
others.
76. To aid in the illustration, wc will make use of the following
diagram :
Summit level.
An alternate passage means one wherein the two boats pass each
other on the summit-level, or pass the locks alternately.
1st. When a boat in the level K arrives at the lock A, the lock has
to be filled in order to raise the boat to the summit. The same pro¬
cess has to be gone through when a boat in the level Y arrives at the
lock B, in order to raise this second boat to the summit also. These two
boats on arriving alternately at the locks A and B find them already
filled by the process we have just described, and immediately pass
into them. Then, on descending to the adjacent levels, K and Y, each
boat exhausts the lock-full (prism of lift) which had been used to
raise the other. This is the case of two locks-full for an alternate
passage, or one lock-full for each boat, and is the least quantity
which can be exhausted per boat, under the most favorable circum¬
stances.
77. One boat making the passage would consume no more. On
arriving at a lock, the lock would be filled in order to raise the boat,
and would remain filled after the boat had passed out into the upper
level. Then, on descending at the opposite end, it would exhaust a
prism of lift or lock-full.
78. We have said that one prism of lift per boat is the least which
can be exhausted under the most favorable circumstances ; for, if
the lock A or B were full on a boat presenting itself to be raised,
the case becomes altered; then the lock must be emptied to admit
the boat, before it can be raised ; and after this, by which one lock-
20
fall is drawn off, another lock-full must be drawn off, to lower the.
boat at the opposite end of the summit. We see, therefore, that the
case of one lock-full per boat is on the supposition of a regularity
in the passages and attention to the locks that is hardly possible in
practice; in fact, it may be considered as never occurring.
79. 2d. We will now suppose the case of two boats passing in
succession. For the first, the lock has to be filled ; it then passes to
the sLiminit. 13ut for the second, this lock-full has to be let off, that
the boat may enter the lock ; which has then to be filled again in
order to raise the boat : the two boats, therefore, are raised to the
summit by the exhausting of one lock-full of water. On arriving
at the other end, one lock-full for each boat is exhausted, to enable
the two boats to descend: in all, three locks-full, or prisms of lift,
for the passage of two boats in^ succession. This is a case of one
lock-full and a half for each boat, and which also requires the most
favorable circumstances ; for, as in the first case, if the lock were
filled when the first boat presented itself to be raised, it Avould have
to be let off before the boat could enter; which adds another lock-
full to the quantity exhausted by the successive passage of the two
boats, or two locks-full for each.
3d. Suppose three boats to present themselves at the same lock in
succession. The first is to be raised by filling the lock; the second,
by exhausting that used to raise the first, and filling again ; the third,
by exhausting that used to raise the second, and filling again. The
three boats are therefore raised by exhausting from the summit two
locks-full. But on arriving at the opposite end, one lock-full is ne¬
cessary to let each boat down. The passage of three boats in suc¬
cession will then require five locks-full, or six, if the lock be full on
the approach of the first boat.
4th. If we suppose a passage of four boats in succession, seven
locks-full, or one and three-quarters to each boat, will be required ;
or two for each, if the lock be full on the approach of the first boat.
80. We have seen, therefore, that as small a quantity as one lock-
ftdl for the passage of a boat is scarcely a possible case ; that a lock
and a half for each boat is the least that can be used in the succes¬
sive passing of two boats ; that a lock and three-quarters is the least
that can be used in the successive passing of fourhoats; and that,
in every case, if the lock be full on the approach of a boat, two locks-
full will be required for the passing of the summit by every boat.
81. To generalize the case for any number of successive passages,
it is that the least quantity of water which can be used is twice as
many locks-full, less one, as the number of boats, (or two locks-full
for each boat,) when the first boat finds the lock full on its approach.
82. Our trade is not only periodical, but is at all times in fleets,
from the nature of business and the social habits of boatmen. Who
ever observed on our canals an alternate direction of every boat?
They are generally—I may say universally—in groups or fleets ; three,
four, or five, in one direction; then three, four, or five in another.
Passages may balance each other on the same day in different di-
21
vections; but this does not constitute alternate passages. If five
boats pass in one direction in one hour, and five in the opposite di¬
rection in the next hour, it does not constitute the alternate passages
upoir which the estimate of one lock-full of water for each boat is
founded. These are successive passages for the whole number of
boats, except one. An alternate passage is, when two boats pass in
opposite directions, before either is succeeded by another boat; or,
when any number of boats pass alternately, without any o?ie to fol¬
low another until after a boat from the opposite direction has passed.
When fleets from opposite directions meet at a lock, alternate pas¬
sages are adopted by the rules of most canal companies; but wheir
they meet on a level, they pass each other in fleet, and the locks at
each end in fleet. On meeting at a lock, equality of rights demands
alternate passages; but on meeting on any level of the canal, equal¬
ity of rights demands no such sacrifice of time; nor is it necessary,
nor would the trade submit to it, nor has any attempt to exact it
ever been made.
S3. But the passage of fleets in different directions, or of a fleet
and a boat, has its influence upon the quantity of water required.
We will see what it is; (our reasoning, is applied to the passage of
a summit;) but we will first, however, again explain why it is that
one alternate passage, which is the passage of two boats in différent
directions, consumes less water than a consecutive passage, or the
passage of two boats in the same direction.
84. In the first case, each boat is raised to the summit,by merely
filling the lock. The water has not yet been exhausted or drawn off,
or let down below the summit ; it has only been let into the lock. On
passing to the opposite ends of the summit, the locks are found as
they were left, filled with water: each boat, on descending, takes only
the lock-full, which it found ready, down with it. As these two boats,
therefore, were raised without drawing off any water from the sum¬
mit, and were let down with one lock-full each, the two consumed
but two locks-full in the passage. This is the al/.er7iale passasse o(
the engineer.
85. In any other order of pas.sing, as has been before explained,
and which must be successive, the two boats cannot consume lc.ss
than three locks-full, or one and a half each. .Now, as it can only
be two single boats meeting each other which can make an alternate
passage, it can therefore only be the two first boats of two fleets;
the remaining boats of the fleet make consecutive pa.s.sages. The
case, therefore, of two fleets meeting on a level, or passing in oppo¬
site directions, resolves itself into that of a fleet meeting one boat ; or,
into one alternate passage and consecutive passages for the balance
of the fleet. It matters not whether this alternate pas.sage be with
the first or any other boat of the fleet ; the effect is the same.
8G. 1st. The smalle.st fleet is that of two boats. If a fleet of two
boats meets one boat, it constitiite.s one alternate pas.sage and the con¬
secutive passage of one boat. The quantity of water consumed is,
therefore, til i-ee locks-full for the three boats, or one lock-full per boat.
22
2d. If a fleet of three boats meets one, it is one alternate passage
and the consecntive passing of two. The four boats, therefore, con-
.sume five locks-full of water, or one lock-full and a quarter each.
3d. If a fleet of four boats meets one, it constitutes one alternate
and three consecutive passages ; or, tlie five boats will consume seven
locks-full of water ; which is one lock-full and two-fifths each.
4th. If a fleet of five boats meets one, it constitutes one alternate
and four consecutive passages ; or nine locks-full for the six boats ;
being one lock-full and a half each.
5th. If a fleet of six boats meets one, it constitutes one alternate
and five coirsecutive passages, and will consume for the seven boats
eleven locks-full of water ; or one lock-full and four-sevenths to each
boat.
6th. If a fleet of seven boats meets one, it constitirtes one alternate
and six cori-secutive passages ; or the eight boats will consume thir¬
teen locks-full of water, or one lock-full and five-eighths for each
boat.
7th. If a fleet of eight boats meets one, or if (which gives the same
result) eight boats pass in one direction while one passes in the oppo¬
site direction, the nine boats will require fifteen locks-full of water,
or one and six-ninths or one lock-full and two-thirds each.
Sth. And a fleet of nine boats meeting one, or nine passing in one
direction and one in another, the ten boats will require seventeen
locks-full, or one lock-full and seven-tenths for each.
87. We see by the foregoing, therefore, that more than one lock-
full must always be used ; that the second supposition requires one
lock-full and one-quarter for each boat ; the fourth one and one-half ;
and the eighth nearly one lock-full and three-quarters.
88. Now, this is all the rigid result of theory, on the supposition of
the most favorable circumstances, which can never be obtained in
practice. Irregularities will creep in : they are unavoidable ; and, as
previously explained, these irregularities soon throw every case into
that of a maximum exhaustion, or two locks-full of water for each
boat. We are not theorizing, but endeavoring to exhibit practical
effects ; we must pay attention, therefore, to such practical results as
are highly probable.
89. There is another, and not inconsiderable cause of waste, which
is, with most propriety, to be placed to the account of lockage, as. it
is occasioned by the passing of boats : we mean that of the column
forced over waste-weirs, over lock-gates, and down the feeding-flumes,
by the wave from the motion of the boat. In an active trade, this
will be found to be a very serious cause of waste : to which may be '
added that arising from the fact of the lower gates, after a boat has
entered, always being somewhat open until forced to by the current
created by letting water in at the upper gates, by which much water
is lost.
90. It is somewhat singular that, while two locks-full per boat is
the maximum of theoretical reasoning on this subject, it is yet, how¬
ever, the result of common irregularities of trade and of slight in-
23
attention on the part of lock-keepers. Does any one doirLt that these
irregularities and inattentions are of common occurrence ? If so, let
him pass a few weeks on any of our carrais, and his doubts will be
removed. The maximum of theory, then, being no uncommon result
in practice, would it be proper—would it be safe for an engineer to
estimate a less rate for his lockage ? We think riot; and wc there¬
fore adopt it as the rate by which our judgment of water exhausted
from this cause will be governed.
91. A distinguished writer on this subject has introduced, in his
calculations of the water consumed in the passing of locks, a deduc¬
tion of the quantity displaced by the submersion of the boat. Although
we cannot dispute the corrcetne.ss of the consideration, yet, when a
view so rigorous has to be taken in order to prove the sniPiciency of
water for a canal, it becomes, in onr judgment, a worse tlian doubtful
project.
92. There is also a serioir.s loss of water arising from a cause hardly
atlribiitable to either of the heads named, and particularly to be no¬
ticed in wide canals: Ave mean that occasioned by high Avinds, Avhich
dash the AvaA'CS over the toAving-paths, doAvn the fceding-ilurne.s, and
over the lock-gates.
9,3. Under all these considerations, therefore, Ave repeat the opinion
that Ave adopt tAvo locks-full of Avater for the passage of the summit
hy each boat; and avo cannot, Avitliont a reproach from onr own
judgment, adopt less.
.94. Feeders.—It i.s a Avell-known fact, attested by niiivcr.sal ex|)e-
rience, that the loss of Avater from feeders i.s greatly disproportionale
to that from canals : Ave mean simple feeders, Avhich are .small canals
to pass Avater, and too .small for the usual canal-craft. Various cause.s
are assigned for this peculiarity : the greater velocity, by which the
Avater being more agitated, occasions increased evaporatioir ; the
smallnessof the column, Avhicli, becoming .sooner and more heated by
the sun, produces, on this account, also a greater amonntof evapora¬
tion ; the less consolidation of the bottom and sides, from the dimin¬
ished volume of Avater causing Ic.ss pressure, from Avliicli fiitratious
arc the greater ; the purer and clearer condition of the Avater, carrying
little or no sediment or dissolved earth, hy Avhich in canals the fil¬
trating pores of the exposed surface become gradually closed. These,
and others more philosophical and abstract, are given as accounting
causes. Be they, lioAvever, correct, or not, the fact is as stated, and
it should he taken into consideration in reasoning upon feeders.
9.9. The best constructed and oldest feeders knoAvn are those of the
Briare and Languedoc canals of France. Of lhe.se it has been re¬
marked, that, Avith the exception of covering, no other precautions to
prevent losses of Avater can avcU he imagined.
9G. The noted feeder of the Briare canal is called "the feeder of
Saint Privé." Its length is about 11 miles, and its average dimen¬
sions about 12 feet at Avater-surface, 9 feet at bottom, and ,3 feet
deep. After frequently-repeated and most exact gauging, it Avas
found to lose three-fourths of the Avater it received; or, in other
24
words, it delivered into the canal but one-foiirth of the water which
it received from its source of supply. This los.s is equivalent to about
0.68 per rnilc of the quantity received.
97. To the Languedoc canal there are two feeders : the Plaine and
the Mountain feeder. The entire development of these is 88,225
yards, rather more than 50 miles. Of this development 32,876 yards
are artificially constructed; the balance being the old beds of streams,
in which, whatever may be the filtration, it has long since arrived at
its minimum. Of the 32,876 yards, 20,254 yards are made through
a comparatively impermeable granite : that is, about one-fourth of
the whole length. Various concurring circumstances are stated by
Huerne and others as well adapted to reduce the filtrations of those
feeders. Nor is the loss tiiey experience alluded to as extraordinary ;
yet, from a critical comparison of the water received and delivered,
the actual loss per year is more than 100 times the water-prism,
(Huerne, p. 270,) or more than 10 prisms per month for a navigation
of 10 months. Now, this loss must be chiefly on that part which is
not made through the. comparatively impermeable granite, and may,
tiierefore, be charged upon 68,000 yards, about three-fourths of the
whole distance, which would make about 125 of its water-prisms
during the navigable year, or 12i prisms per month.
98. The size of a feeder may be assumed at 12 feet water-surface, 8
feet at bottom, and 3 feet deep. This would give a cube or prism
per mile of 158,400 cubic feet, or 5,866.6 cubic yards. Now, 12è
times this prism would be 73,332.5 cubic yards per month, or 45.8
cubic feet per minute.
99. Eeservoirs.—We shall view these under the limited aspect re¬
quired by our object: their ability to retain water, and the quantity
which it is probable they will receive in proportion to the rain upon
a given surface. Upon this last peculiarity, climate has, without
doubt, a great influence. In northern climates, the ground is longer
and harder frozen ; the accumulation of snow upon its surface pro¬
portionally greater, which passes into the reservoir from gradually
melting by the warmth of spring, losing less by filtration, as less will
pass through the frozen surface of the soil. On the.se accounts, there
can be no doubt that more water will be collected in reservoirs in
more northern climates, for, in more southern, a greater portion of
that which falls on the surface of the soil will pass off by filtrations.
These considerations would make more lakes in a northern climate,
more and larger springs in a southern ; which inference we believe
to be actually sustained by the general physical peculiarities of the
globe.
100. The point first to be established is, what proportion of do wn¬
fall-water upon a given surface can be collected in a reservoir ? Upon
this we have searched in vain among the works of European en-
, gineers for the result of direct observation. All is estimate, conjec¬
ture, speculation: the general result of which, however, is, that
about one-third of the water which falls may be collected in a suit¬
able reservoir. The form of the surface of the soil has not so much
influence as many would suppose, except in the rapidity of the
drainage. Numerous streams are found in a rolling country—exten¬
sive swamps in a flat ; and the greater evaporation which water in
the latter experiences from longer exposure, about compensates for
the less filtration of the former from a more rapid flowing off. Of
course, we have not in mind extreme cases of either.
101. Sutcliff, (p. 84,) speaking of the Rochdale canal, after a cal¬
culation on the subject, says : " which plainly proves that, notwith¬
standing the close texture of the soil, little more than one-third of the
rain which falls upon them (the commons) can be got into the sum¬
mit-level ; and, were these commons cultivated, I do not think that
more than one-sixth part of the rain that would fall upon them could
be drained off."
102. When the Chenango canal, in the State of New York, was
about being made, and which was to depend principally upon water
collected in reservoirs for its supply, the engineer, Mr. J. B. Jervis,
estimated one-fifth of the downfall-water as the quantity which could
be collected; but, with a view of ascertaining the matter more accu¬
rately, he had experiments made in the valleys of two streams, Mad¬
ison brook and Eaton brook, which will be found in the report of the
New York canal commissioners of January, 1S36.
103. Arrangements for gauging were established in each brook,
and the results of the daily gauging at each place, and also that of
the rain which fell at the same time, will be found in the following
tables.
Tabler No. 1.—Eaton-brook valley.
1835.
1
Rain gauge.
Falling water
on an area of
6,800 aerea.
Am'nt of same
passing sluice
from same area.
Per centagc
of drainage
to fall. 1
Months.
June - - -
July ....
August - - . .
September - - - -
October . . . -
November - - . -
'December - - - -
Inches.
6.72
2.74
2.80
1.34
3
2.20
.96
Cubic feet.
165,876,480
67,634,160
70, •596,240
33,076,560
74,052,000
54,304,800
23,096,640
Cubic feet.
59,407,394
27,994,240
13,547,058
9,586,513
20,694,651
23,772,020
38,525,544
.358
.414
.192
.29
.272
.438
1.541
June to December, inclusive
-
489,236,880
191,528,020
.392
June to October, inclusive -
-
411,235,440
131,229,856
.319
'Drained the enow of iVovember.
4
2ti
Table No. 2.—Madison-hrook valley.
V
tiD
Falling water
Am'nt of same
QJ
M S'
* 2
1835.
3
on an area of
passing sluice
«-> B
S'S-
W)
6,000 acres.
from same area.
ß
•a
s o 3
PH
Months.
Inches.
Cubic feet.
Cubic feet.
•Snow on ground, which fell in No¬
vember and December, 1834
-
87,120,000
January . . - -
2.17
47,262,600
23,192,079
.491
February . . - -
2.50
54,450,000
35,377,594
.649
fMarch - - . -
1.03
22,443,400
43,284,656
1.928
tApril ... -
5
108,900,000
80,776,974
.741
|May - _ -
1.98
43,124,400
58,013,176
1.345
^June , . - .
8.05
175,329,000
20,138,006
.115
iJuly -
3.87
84,268,600
23,141,302
.274
t August . - - .
3.06
66,646,800
23,726,060
.356
t September- -
.88
19,166,400
19,158,957
.999
t October -
3.86
84,070,800
19,544,880
.232
^November - - -
2.10
45,738,000
18,232,372
.399
^December - - - -
.76
16,552,800
19,401,364
1.172
35.26
January to Dec., inclusive, and snow
-
855,092,800
383,986,420
.449
January to May, do do
-
363,300,400
240,644,479
.662
June to October, Inclusive -
-
429,501,600
105,708,206
.246
104. The foregoing are the only tables of observations of the
kind that I have met with. They exhibit, in a striking degree,
the remark previously made, that greater quantities of water can be
collected in a cold than in a warm climate, or in a climate having a
longer winter or a greater number of months, with the ground so
frozen as to lessen the filtration.
105. On examining the first table, we find that, during the months
of November and December, the whole quantity of falling water
could have been collected to within two-hundredths. It is also evident,
from the second table, that the month of May must be taken as the
latest of the months affected by the winter collection. The drainage
of this month and the one preceding exceeds the falling water of
both months ; the latter must therefore, evidently, owe its great
drainage to the accumulated deposite of the winter. These facts
justify us in placing for the summer drainage of that climate, or for
the drainage period in which the deposites and other effects of win¬
ter are not felt, only the months of June, July, August, September,
•Shows the quantity of water furnished by the snow on the ground when the gauging
commenced.
-[■WUh melting snow.
^tDrainage equalized by reservoir. *
27
and October. By the first table, the average drainage of these five
months is 31.9 per cent.; and, by the second average drainage for
the same month, is 24.6 per cent.
106. Then, taking the two winter months of the first table, the
average drainage is 98.9 per cent. ; and again, using the same winter
months of the second table, wc have an average drainage of 75 per
cent.
107. Although we feel bound to say that these tables are too lim¬
ited to justify the establishing of any general rule, and that, for such
a purpose, observations extending through many years, with the most
exact measurements, can alone justify such a course ; yet, at the same
time, we must acknowledge the facts to be highly interesting, and
deserving the confidence due to such limited observations from the
just eminence of the engineer under whose directions they were made.
108. There is another remark due to the subject. The valley of a
stream is not only the drain of the quantity of downfall-water, which
runs into it from the surface, but also of that proportion which, fil¬
trating through the soil, finds its outlet in the bed of the stream. A
deep valley, therefore, must always collect a greater proportion of
downfall-water than a shoal one, although the extent of drainage be
the same, as more is caught by filtration before it passes below the
bed of the valley. Hence, the depth of the valley, in comparison
with the edge of the drained basin, becomes an essential element in
such a question. Nor can the running water of a stream be included
in the result of drainage, because the stream itself is the result of the
drainage ; and to calculate the stream and the drainage also, is to in¬
volve the same quantity twice. It is only, therefore, at points where
streams come in beyond the limit of the basin of which the drainage
is included, that quantities discharged by streams can be included in
or added to the quantity of water obtained.
109. We have found that in the first table the drainage per sum¬
mer month was less than one-third ; and, by the second table, during
the same period, rather less than one-fourth. Then, taking the two
winter months of the first table, or all the winter months of the sec¬
ond, the mean exceeds these proportions.
110. The tables of Mr. .lervis, therefore, plainly indicate a differ¬
ence in the quantities collected during the summer and winter months;
they also evidently show that seven months of the year is the num¬
ber in which the quantity collected may be considered as influenced
by the winter condition of the soil for the climate in which the obser¬
vations were made. For the climate in which the canal is situated
that is to be the subject of our report, if we were to allow four months
as the number influenced by the conditions of winter, we presume
that wc will meet the case rather above than below its reality.
111. Before we go farther, it will be proper to consider the rate of
rain to be accepted. Through the politeness of my friend, Dr. Har¬
lan, of Philadelphia, I have been supplied with an extensive collec¬
tion of rain-tables for various parts of the country; but, after giving
to these the most deliberate consideration, I have come to the con-
28
elusion that the most appropriate table for our subject is the one near¬
est the locality of the contemplated canal, which is that of Mr. Brantz,
of Baltimore.
112. The usual method of taking the average of several years' rain
does not appear to me deserving of imitation ; because it is well
known to every engineer that, during abundant years, a vast amount
of water is allowed to run to waste, that is, is discharged by waste-
gates from the reservoirs. To introduce this in the average of quan¬
tities collected, would be to introduce a quantity never preserved,
never applied to any of the uses of the canal, and which must there¬
fore lead to erroneous conclusions. It was probably owing to sim¬
ilar reflections that the board of engineers, in their report on the
Chesapeake and Ohio canal, used only from Mr. Brantz's tables the
rain of 1822. Under these considerations, we shall adopt for our ob¬
ject the rain of 1822 of Brantz's table; but, that those who diifer
with us on this point may have the means of calculation on a differ¬
ent basis, we give the entire table for nine years.
113. Table of the monthly depth, in inches, of rain at Baltimore.
[From ?TÎr. Brantz's tables.]
Months.
1817.
1818.
1819.
1820.
1821.
1822.
1823.
1824.
Mean.
January
2.25
0.90
0.70
2.80
3.30
1.80
5.60
2.30
2.85
February -
2.80
2.00
1.90
2.20
5.40
4.80
0.70
5.90
3.225
March
4.50
3.00
4.55
3.30
1.70
1.30
7.10
4.30
3.71
April
1.50
2.10
2.70
1.10
2.10
2.10
1.80
4.70
2.20
May
2.60
6.45
4.10
4.40
5.10
1.50
2.10
2.95
3.65
June
9.10
1.15
1.30
4.60
1.80
1.50
1.60
5.03
3.66
July
3.50
4.10
2.20
2.20
7.50
4.35
3.60
3.37
3.85
August - ■
10.40
2.00
4.30
8.00
0.30
0.80
4.10
4.50
4.30
September -
3.30
3.20
3.00
1.50
10.70
2.25
5.80
2.94
4.45
October
1.80
3.10
0.70
7.80
3.40
2.50
2.80
1.77
2.975
November -
3.70
2.00
1.10
2.70
5.60
5.10
3.10
2.27
3.20
December -
3.60
2.60
2.20
1.90
3.30
1.20
6.25
2.25
2.80
Amount -
48.65
32.60
28.75
42.50
50.20
29.20
44.55
42.28
39.89
114. By the foregoing table it appears that, in 1822, the fall of rain
was equal td 29.2 inches, say 29 inches ; which would give for one
acre 3,898 cubic yards. We have before remarked that the general
opinion among engineers is, that one-third of the downfalUwater can
be collected; but, by the tables of Mr. Jervis, about two-fifths can be
collected ; and, in his opinion, two-fifths may be counted on with safety.
The point, therefore, upon which one's judgment may hesitate,
is in the adoption of one-third or two-fifths. \Ve acknowledge that
the facts in Mr. Jervis's tables have more weight with us than con¬
jecture. It is only that his observations were of so limited a period,
and that the excessive drainage of some months induces us to suspect
error in the observations, that we do not at once adopt them ; as.
29
for instance, table 2—while the drainage of February and March ex¬
ceeds the whole downfall-water of these two months, that of April
and May, immediately succeeding, nearly equals the downfall-water
of those two months ; the drainage of these four months exceeds the
downfall of the four; and the downfall of the two or three preceding
months is not, taking the months of the same year as stated, so exces¬
sive beyond the drainage satisfactorily to account for it, with a rea¬
sonable allowance for evaporation and filtration. There may be no
error; the facts may be as stated; but, being very singular, and cer¬
tainly new, we do not think they would justify the adoption of a gen¬
eral rule until verified by repeated subsequent observations. Now,
excessive drainages are involved in the average result of both tables,
which in No. 1 is 0.392, and in No. 2 is 0.449, the mean of which
is 0.4205, or say two-fifths. I'reating the table of Mr. Brantz, for
1822, according to our reasoning about summer and winter months,
allowing four for the latter, the result would also be about two-fifths,
or forty per cent.
115. But, from the remarks which we have made on the tables of
Mr. Jervis, we feel unwilling at present to adopt what they would
justify. Observations are now being made, in reference to the same
subject, on the summit-pass of the Chesapeake and Ohio canal. These
will probably confirm Mr. Jervis's results, or, in conjunction with
them, furnish the profession with more positive data than it has hith¬
erto possessed in reference to this highly interesting question. Until
then, we feel some doubt about the propriety of deviating from the
rule hitherto generally received, that one-third or 33 per cent, of
downfall-water can be collected in well-arranged reservoirs. Mr.
Jervis's tables would justify the assumption of two-fifths, or 40 per
cent. After all, the difference between the two is no more than seven-
hundredths.
116. Applying the rule, then, which we have decided to adopt, viz:
one-third of the downfall, to the rate of rain of 1822, it will give,
as the quantity which can be drained into a reservoir from each
acre of its basin, 1,299 cubic yards.
117. The next question refers to the loss which water experiences
from evaporation and filtration, after having been collected into res¬
ervoirs. Sutcliff, on this subject, and referring to the reservoirs of
the Rochdale canal, says, " In the summer months, they sink one
inch per day when the cocks are .shut close, and yet I think no reser¬
voirs are more water-tight than they. But I will only estimate upon
the reservoirs wasting half an inch per day, and confine it to those
on Blackstonedge, as that at Hollingswork gives a certain quantity of
water con.stantly to the mill-owners, which makes it difficult to as¬
certain hovr much it wastes," &c. It is really to be regretted that
this question had not been more nicely determined, the opportunity
being very favorable, as the quantity which the mills consume ad¬
mits of accurate calculation. We must, however, under the circum¬
stances of the case, be content with his rate of loss of half an inch
per day, or fifteen inches per month.
30
118. For the same object, Andreossi applies to the reservoir.9 oí'
the Languedoc canal twelve millemetres per day, equivalent to 0.472
of an inch. The coincidence between the two is sufficient to justify
us in adopting for the reservoirs a loss of half an inch per day.
These rates are given by both authors as actual states of loss from
exposed surfaces, under the effect of rain upon them.
119. We have collected much information upon reservoirs in our
own country, but it was not of a kind, either in the character of its
facts or their accuracy, to be of use in the points which we have been
discussing ; and a reference to it would, in consequence, merely extend
the volume of our report without elucidating its object.
120. Having concluded that an average rate of one-third of the
downfall-water can be collected into suitably-arranged reservoirs ;
having shown that the drainage between winter and summer months
varies considerably ; and having also decided that for the climate of
the contemplated canal four months may be assumed as the number
affected by the condition of winter, it now becomes necessary to
ascertain the effect of these considerations upon the rain assumed.
121. By the second table of Mr. Jervis, which extends through the
whole number of months in the year, it appears that the summer
drainage was equal to 0.246 ; say 0.25, or one-fourth of the downfall-
water. Applying this quantity to eight • summer months, and in¬
volving the remaining four for the balance of the remaining average
of one-third, it will justify for these latter (the winter months) an
amount of drainage equivalent to 50 per cent, of the downfall-water ;
rather more than the correct fractional quantity. Now, applying
these considerations to Brantz's tables for 1822, we have the fol¬
lowing results ;
Fall of water.
Drained.
Quantity
Quantity drained
drained.
per square acre.
Months.
Inches.
Per cent.
Inches.
Cubic feet.
January - . .
1.8
0.50
0.9
3267.0
February
4.8
0.50
2.4
8712.0
March . - -
1.3
0.60
0.65
2359.5
April -
2.1
0.25
0.525
1905.7
May -
1.5
0.25
0.375
1361.2
June -
1.5
0.25
0.375
1361.2
July -
4.35
0.25
1.0875
3947.6
August -
0.8
0.25
0.2
726.0
September
2.25
0.25
0.5625
2041.9
October
2.5
0.25
0.625
2268.8
K ovember
5.1
0.25
1.275
4628.2
December
1.2
0.50
0.6
2I7S.0
T otal
29.2
0.333
9.575
.34757.1
31
122. The total quantity which, by the foregoing table, may' be col¬
lected in one year from one acre, is 34757.1 cubic feet, or 1287.3
cubic yards; and of this quantity it appears, that during the four
months of December, January, February, and March, there may be
collected 16516.5 cubic feet, or 611.72 cubic yards; and during the
summer months of April, May, June, July, August, September,
October, and November, 18240.6 cubic feet, or 675.57 cubic yards.
From which it will be perceived that the four months of winter
drainage, being nearly equal to the whole drainage of the eight sum¬
mer months, shows the necessity of so planning and arranging the
reservoirs that the winter drainage may be collected and preserved to
meet the deficiencies of the summer supply.
123. These remarks naturally lead us into considerations of the di¬
mensions of the reservoirs—a matter, however, which more properly
belongs to the plan of the canal after its practicability has been de¬
termined. But, generally speaking, these dimensions should be
adopted to fill the canal on the opening of navigation, and to maintain
its trade and waste by supplying any deficiency from the summer
drainage and probable drought.
124. The dimensions of reservoirs have great influence upon their
usefulness. Deep and narrow valleys should always be selected for
such purposes. The losses they experience are in proportion to the
surface ; the less the exposed surface in which the same quantity of
water can be confined the better. The reader will the more readily
appreciate thi.s remark, when he understands that the surface of one
mile square is sixteen times as great as a surface of one-quarter of a
mile square ; and if, therefore, by the fortunate position of a narrow
and deep valley, a reservoir could be constructed that should not ex¬
pose more than a quarter of a mile square oí surface, and contain as
much as under other circumstances would have to be spread over one
mile square, the same mass of water would in the one case lose only
one-sixteenth of what it would in the other. From which it may
also be inferred, that, from the want of suitable positions for reser¬
voirs, a canal may be impracticable, although the extent of surface
drained would yield a sufficiency of water.
125. Dimensions.—As the contemplated canal is, in fact, an ex¬
tension of the Chesapeake and Ohio canal to Baltimore, which would
make that city one of its great terminations on navigable waters, it
appears to me there can be but one opinion in reference to its dimen¬
sions, trunk, and locks ; and that these should be the same as those
of the canal of which it forms so important a part. But, in conse¬
quence of the new summit to this part, the lift of the locks may be
reduced, in order to adapt them the better to the probable supply of
water. Such, also, appears to be the opinion of engineers Trimble,
Fisk, and Hughes. The first adopts a lift of 5, the two others of 4è
feel. Preferring, of the two, the lift of 5 feet, we shall assume that
in our calculations. Accordingly, therefore, our reasoning will be
applied to a canal 60 feet at water surface, 32 feet at bottom, and 6
feet deep ; to locks, 100 feet by 15, with a lift of 5 feet, the prism of
32
lift of which will be 7500 cubic feet, equal to 277.7 cubic yards. In
adopting, however, this reduced lift, it is solely from the consideration
that it may be necessary in order to accommodate the canal to the
supply of water—experience having proved that, in most points of
view, the best lift for a lock is from 7 to S feet.
126. FraclicabilUy.—The question of practicability, with due sup¬
ply of water, depends upon the quantum of trade. A canal may be
made, and there may be water enough to fill it; but if there should
not be enough to sustain a reasonable degree of trade, we believe the
common sense of mankind would at once decide that such a canal
was impracticable.
127. For the probable extent of this trade we will refer to the ex¬
tremely interesting remarks, under the head of "general considera¬
tions," in the report of the board of engineers upon the Chesapeake and
Ohio canal ; and a slight degree of observation upon the facts daily de¬
veloping is sufficient to demonstrate that the views of the board will
soon be realized. These, however, embrace the great trade East and
West, in which this canal cannot participate until the great commu¬
nication is completed ; but, whenever completed, the extension to
Baltimore must come in for a share. Its practicability, therefore,
should have reference to its capability.
128. But, although participation in the great trade to the West may
.not soon be realized, yet we know that the line to the great mineral
region of the Allegantes is now within a year or two of being com¬
pleted, and that it will be in full operation by the time the contem¬
plated extension to Baltimore can be made. This extension will,
therefore, have in the outset to subserve an extensive and established
trade ; in reference to which, its capability should be tried.
129. The Allegany is the great bituminous coal region of our
country with which this canal has to communicate. It would be su¬
perfluous to reason upon the amount of trade from such a region.
Our periodicals are full of facts upon the subject, with which every
one who can read has already become acquainted. That the demand
for this mineral will soon bring the canal to the maximum of its ca¬
pability, no one can doubt ; and, using that principle as data, we may
determine its practicability with due supply of water. The maximum
of the ability of a canal depends upon the number of boats which can
be passed through its locks. A medium, we shall place at half that
number ; a minimum, at one-fourth ; and, in our judgment, the canal
which does not possess a minimum ability is impracticable. Our re¬
marks have no reference to profits. We will admit at once that a
minimum ability would not furnish a profitable income upon the in¬
vestment—that it would be a mere barren practicability ; but there
may be cases in which it would be to the advantage of the State to
construct a canal, there being no other route practicable, regardless
of any probability of profit from its revenue. This is a matter for the
State to decide. I have to do only with the question of " practica¬
bility, with due supply of water."
1 SO. Bare barren practicability, then, might be considered as pos-
33
sessed by a canal which could supply with its water all causes of
waste, and be able to sustain a minimum trade. Bare practicability
is not, however, the question to be decided ; it is "practicability, with
due supply of water." "Due supply" can have no other meaning
than "adequate supply," and adequate supply must have reference
to the probabilitie.s of trade. If we suppose, then, that the commer¬
cial advantages of Baltimore would enable her to direct about one-
half of the entire trade of the Chesapeake and Ohio canal to her own
stores—and, without doubt, the object of the canal is to give Baltimore
all that it can command of its trade—it will then be necessary to
show that the canal will be able to pass at least that quantity, or we
shall fail in proving an adequate supply of water. I'he point, then,
of "practicability, with due supply of water," depends upon the ques¬
tion whether or not the supply will be adequate to what we have
previously distinguished as a medium trade, or half the entire power
of the locks with a full supply of water. Half the number of passages
of a full supply will, therefore, be taken as the test of "practicability,
with due supply;" and if it should appear that there is water enough
for such a number of passages, adding tliereto allowances for waste,
I shall not he.sitate to give it as my opinion that the canal "is practi¬
cable, with due supply of water."
131. Now, we will suppose that 12 boats per hour may be passed
through a lock of 5-feet lift, and that the average of daylight during
the ten mouths of navigation is 12 hours. As there is a lock at each
extremity of the summit-level, there would be 21 passages per liour,
or 2S8 per day, lor the maximum ability of the extension to Balti¬
more. A medium ability, or that which I have considered "practica¬
ble, with due supply of water," would then be 141 passages both
ways, or 72 passages eacii way. We will, however, for greater se¬
curity, and for facility of calculation, assume SO passages each way
per day. The engineers who have previously reported on this mat¬
ter, have assumed 100 passages each way; in taking but SO for our
guide, wc may be considered as treating the question with great lib¬
erality. Our reader will boar in mind that wc assume 80 passages
per day as no more than half the ability of a lock of 5-feet lift, with a
full supply of water; and that we consider it necessary to show water
enough for this number of passages in each direction, or 160 in the
two directions, or we shall fail in proving the "practicability of the
canal, with due supply of water," and which, wc have said, should de¬
pend upon its ability to direct about one-half (rather more) of the trade
of the Chesapeake and Ohio canal to Baltimore, which trade we have
considered equivalent, or that it will be, to the full ability of its lock
for twelve hours.
132. We have now terminated our remarks upon wliat wc con¬
sider the preliminary questions of the case. They iiave extended
themselves, however, into greater length than we had anticipated.
We shall therefore endeavor to generalize them, and to reduce them,
so that their application will be more convenient.
1 33. Wc have shown that the Languedoc canal, during ten months
34
of navigation, loses by its filtration more than eight times its prism
of water. It will not, we believe, be considered unreasonable to sup¬
pose that the prism which the canal contains at the closing of its nav¬
igation is lost during the remaining two months, and, of consequence,
on the opening of navigation, this prism has to be supplied from the
feeders; which will make more than nine prisms of water for the ten
months of navigation. To this item must yet be added the losses from
evaporation, and the leakage from the locks.
134. With such facts, we presume the inference will not be dis¬
puted, that this canal, the one which loses the least from all causes
of waste of any known canal, cannot lose less, during its ten months
of navigation, than ten prisms of water, or one prism per month.
135. But would it be wise to adopt, as an estimate for another
canal, the losses which one of the character of this experiences? We
should answer in the negative. IMoreover, if our views of its evap¬
oration be correct, as previously e.xplained, (25,) to the nine prisms
stated (in 133) as its loss from evaporation, should be added three
and one-fifth prisms. Then, if we suppose the leakage from the lock-
gates, and all other causes of waste, merely adequate to make up this
last fraction, the whole will give, for its total loss from all causes,
thirteen prisms of water for its ten months of navigation, or one and
three-tenths of a prism per month. We have seen (44) that the cube
of this canal, for one mile, is 64,207 yards ; Avhich, treated for the
losses we have just enumerated, will make the same equal to 52.2
cubic feet per mile per minute, which, in our judgment, is not beyond
the reality. The evident disposition in all the authorities to which
we have referred to vaunt the advantages and lessen the defects of
this canal, is continually involving the latter in minimum considera¬
tions, and, consequently, unsafe rules.
136. The board of United States engineers, in their report on the
Chesapeake and Ohio canal, supposed the losses from filtration and
evaporation will be one prism per month-—less than what we have
already seen actually takes place with the Languedoc canal. The
opinion of the board appears to have been founded upon observation
in reference to the Narbonne canal, which, after a use of six years,
lost one and two-thirds of its prism of water ; and, considering the
summit of which they were treating, (more tenacious in its soil than
that of the Narbonne canal,) the inference drawn was, that the for¬
mer would lose once its prism per month.
137. The Narbonne canal may be supposed to have reached its
minimum loss in six years ; and the rates given are for filtration and
evaporation only ; that of leakage at lock-gates is not taken into the
account. Nor is there in our canals that care of construction, and ex¬
tent of excellence in puddling, which the board evidently took into
consideration in the estimate of loss of water which they gave.
138. Moreover, in the second report on the same canal, (page 54,)
the board, reasoning upon a different summit, much more abundantly
supplied with water than that taken into consideration in the first
report—not requiring so close a calculation to show its bare practi-
35
cability, and which they recommend to be adopted in preference
to the first—take great pains to show that there will be 120,000 cubic
yards per mile per month for the various causes of loss, exclusive of
lockage. Now, as the prism of the canal of which they were treating
is no more than 39,785 cubic yards in a mile, we see that the sum¬
mit which they ultimately and unequivocally recommend, and for
which they furnished a plan and estimated the cost, had a supply of
water, exclusive of lockage, of between three and four times its prism
per month, " destined (as the board themselves express it) to feed the
canal, exclusive of lockage or, in other words, to supply water for
all other causes of consumption.
139. Also, in the general opinion given in the first report of the
loss of one canal prism of water for each month of navigation, con¬
sideration does not appear to have been given to the prism left in the
canal, and lost while the navigation is suspended, or for the lock-gate
leakage.
140. On these accounts we cannot forbear expressing it as our opin¬
ion that an allowance of one prism of water per month of navigation,
for all causes of exhaustion except lockage, will prove to be insuffi¬
cient, and is, therefore, an unsafe rule.
141. The loss on the Erie canal, which we have found, at the least
of the ascertained rates, to exceed five times its prism per month, is,
without doubt, singularly great. The observations were made in
1834, when its losses should have approached a minimum. It would
be considered out of place to discuss, in this report, the probable causes
of so great a loss of water ; nor have we, in fact, that accurate knowl¬
edge of the canal which would justify the attempt ; but, as a mere
opinion, we feel disposed to place much to the account of defective¬
ness in the original construction. Be that as it may, however, we
should not hesitate to pronounce a canal as practicable that should
possess a less supply; nor should we feel ourselves as doing justice to
the profession of the engineer if we were to require resources of wa¬
ter to equal the standard of the Erie canal before we would give an
opinion in favor of their sufficiency.
142. The loss for filtration and evaporation on the Chesapeake and
Ohio canal has been found to be about twice its prism of water per
month of navigation. Now, as this canal is the same in its dimen¬
sions as that to which our remarks are to be applied, the climate also
similar, and in some degree its soil, we consider it the fairest guide
for our opinion, and shall therefore adopt the results it has yielded.
143. Our reasoning, then, will furnish the following data for cal¬
culating the quantity of water that will be exhausted:
1st. The canal has to be filled.
2d. Twelve locks-full per day should be allowed for the leakage of
each lock at the end of the summit-level.*
• Annales des Ponts et Chaussées vol. 10, p. 162.—Eight locks-full per day is allowed
for losses on this account.
3ß
3d. Two prisms of the canal per month for losses from filtration,
absorption, and evaporation.
4th. Two locks-full of water per boat, for the passage of the sum¬
mit.
5th. Twelve and a half prisms of the feeders per month for loss in
feeders.
I feel less confidence in the adequacy of this, than of any other
item. It is taken from the experience of the Languedoc canal, in
which particular care has been bestowed upon the construction of
the feeders. I desire it, therefore, to be distinctly understood, that I
contemplate well-constructed feeders, carefully puddled throughout.
Gth. One-third of the downfall-water as the quantity which can be
collected in the reservoirs.
7th. To allow a loss of half an inch in depth for each day for the
water when collected. The loss on this aqconnt will extend through
the whole year.
8th. And, for the locality of the canal in contemplation, to adopt a
rate of rain of 29 inches per year.
144. But, after all, every candid and experienced engineer must
acknowledge that these rates can be viewed only as a minimum ;
less would be inadequate to the object. Any unforeseen event, there¬
fore, that creates additional loss, at once throws the supply into a
state of inadequacy, and produces a comparative failure in the canal.
On these accounts it is the duty of every engineer, after having stated
all the causes that can be appreciated which consume water, to show
a proper surplus to meet unforeseen contingencies.
145. In matters admitting of much greater accuracy, because
founded on more correct data—for instance, the expenses of construct¬
ing the canal—does not every engineer, after having included every
item which experience has suggested, then add his twelve or fifteen
per cent, for accidents and unforeseen contingencies.? Yet, in a mat¬
ter of that kind, the error of a short estimate involves no greater evil
than the expending of more money than had been at first contem¬
plated. But, in the water for a canal, the error for a short estimate
may probably make the whole expenditure of money useless. How
much more important is it, then, that surplus water should be at com¬
mand. The reflection becomes of greater weight when we bear in
mind that, in every instance, the water consumed by canals has ex¬
ceeded the amount anticipated. Even after the long considered and
most cautiously pursued measures in reference to the Languedoc
canal, the additional reservoir of Larapey had to be added.
146. The engineer should, therefore, show that his arrangements
will procure a large surplus of water, or that a surplus is at command,
by additional and appropriate arrangements, should it be required.
147. Having now completed the preliminary remarks, which ap¬
peared to me to be essential to a correct understanding of the subject,
I shall proceed to apply them to the particular cases of the survey.
148. For the reasons already given, (4,) the field operations were
at first confined to two routes, namely, the Linganore and the Seneca
37
routes. These were the two upon which reports had already been
made; and in reference to which the Executive of Maryland had
founded a decision upon their " practicability, with due supply of
water." No other survey south of these, and exclusively within the
limit of the State of Maryland, had then been made; and the impression
was general, that no pass existed south of these and within the limits
specified, the characteristics of which would vary in advantages over
those which had been previously surveyed. But, from a knowledge
of the country acquired by a summer's residence there, I was in¬
duced to entertain doubts of the correctness of this impression, and
accordingly directed the engineers that, in addition to the renewed
surveys of the routes in question, they should also carefully exam¬
ine the ridge of highland elsewhere, and determine positively whether
or not any better way of passing it existed. The result exceeded my
expectations. I was early informed by Mr. Kirkwood, that a route
existed passing the ridge a few miles south of the former surveys,
and much lower. He was required to bestow Iiis best attention upon
it. We were thus involved in the survey of three distinct lines, in¬
stead of two, as had been at first contemplated. In fact, it may be
said that four lines were surveyed, as the data for two suppositions
of the original Seneca route were collected.
149. I had also required the engineers to limit their operations to
what might be considered the summit-section of each route ; by which
I mean that section which would receive its supply of water from the
summit, and which includes the summit-level, and the extension of
the canal each way, to points at which ample secondary supplies
would be received. By this plan all the debatable ground was cov¬
ered; and, by thus limiting the field-work, it would be terminated
soon enough to make a report upon the point of principal interest—
in fact, upon the sole point involved by the resolutions of the Legis¬
lature—in the time anticipated by the. Legislature. Had the field-
work been extended this season to the canal on one side, and the
city of Baltimore on the other, it would have been a mere repetition
of matter upon which no difference of opinion exists in reference to
the practicability of the route ; and which, from the delay it would
have occasioned, would probably have put it out of my power to
have made a report in time for any action of the Legislature at its
next session.
150. Of the three lines mentioned, I shall give but a summary
description,referring for a more detailed knowledge of them to the joint
report of the engineers, Kirkwood and Lee, herewith appended, and
from which the following facts are taken. The map attached to this
report will enable the descriptions to be the better understood.
The Lingunore roule.
151. This route passes the ridge through ihe valleys of IMiddle
run and Grimes's Spring branch. Its summit is 236,070 feet below
the ridge at Grimes's tobacco-house, and 530,179 feet above tide,
according to the survey made by the engineer, J. Trimble. The
length of the summit-section is 12 miles 714 yards, and it will first
38
derive its secondary supplies of water from the Patapsco on the one
side, and from Talbot's branch on the other. It would require a tunnel
3 miles 197 yards long, and will command a drainage of 26.98 square
miles. It will admit of an arrangement of three reservoirs, namely:
1. One on Gillies' falls, with a dam 48 feet high, a surface of 71.Si
acres, containing 3,475,470 cubic yards of water, and receiving the
drainage of 11,202.7 acres. 2. One on Warner's branch, with a dam
38 feet high, a surface of 26,24 acres, containing 1,072,056 cubic yards
of water, and receiving the drainage of 3,346.447 acres. 3. One on
Beaver dam, with a dam 40 feet high, a surface of 20.707 acres, con¬
taining 890,851 cubic yards of water, and receiving a drainage of
2,718.89 acres. It will also require three feeder lines, in all 3,437
yards long.
152. The total quantity of surface drained being 17,268.05 acres, at
the rate of 29 inches of rain, and supposing one-third to be collected, it
will yield 22,441,394 cubic yards of water, which is the extent of
the supply which can be commanded for the summit-section of this
route. We will now ascertain its adequacy to the wants of the canal.
153. There will be required-—
1st. To fill the canal - - 669,575.96 cubic yards.
2d. For lock leakage - - 1,999,995.00 " "
3d. For filtration and evaporation 13,391,519.20 " "
4th. For the trade of the canal - 26,666,640.00 « "
5th. Loss in feeders - - 1,432,183.725 " "
6th. Loss from reservoirs - 1,896,180.000 " "
Total quantity required - 46,056,093.885 " "
Total quantity available - 22,441,394.298 " "
Deficiency, 23,614,699.587 " "
154. This route is, therefore, impracticable. It will be seen that
the supply is even inadequate to the wants of the locks for the trade,
exclusive of every other consideration.
TAe Seneca route.
155. The course of the survey led to two surveys in reference to a
part of this route, varying its termination in the valley of the Seneca.
líí case.—It will require a tunnel 547.66 yards long ; the summit-
level will pass 122.47 feet below the ridge at H. Griffith's; will be
41.26 feet above the Patuxent river, at Etchinson's mill ; and will be
496.26 feet above tide, according to the data of the engineer's (Trim¬
ble) survey. Our operations, as before remarked, not extending, in
any route, to the termini of the canal, we have to avail ourselves of
the labor of our predecessors, in order to ascertain the reference to
tide-water.
The secondary supplies will be derived from the Wild-cat branch
of the Seneca, and the Seneca itself, as the canal progresses, on one
side ; and the Cat-tail branch of the Patuxent, the Patuxent itself, and
39
GO forth, on the other. The total length of the summit-section will be
14 miles 1,193i yards. It admits of the arrangement of two reservoirs.
1st. On Cabin branch, with a dum 30 feet high, with a surface of
31.253 acres, containing 1,008,420 cubic yards, and having the drain¬
age from 2,903.68 acres.
2d. On the Patuxent, with a dam 42 feet high, with a surface of
58.05 acres, containing 2,622,312 cubic yards, and having a drainage
from 8,452.080 acres. The feeders from these reservoirs will be
2,485 yards long.
156. The total quantity of surface drained being 11,445.76 acres, it
would yield, at the rates stated, (152,) 14,875,247.7 cubic yards of
water for the available supply of this route,
157. The demands for water will be—
1. To fill the canal - - 792,211.971 cubic yards.
2. Lock leakage - - 1,999,995. " "
3. Filtration and evaporation - 15,844,239. " "
4. Canal trade - - - 26,666,640. " "
5. Loss from feeders - - 1,763,313.250 " "
6. Loss from reservoirs - - 1,345,095. " "
Total quantity required - 48,415,494.221 "
Total quantity available - 14,875,247.700 "
Deficiency - - - 33,540,246.521 " "
158. This route is, therefore, impracticable. The available quan¬
tity amounts to but little more than half the amount required for the
locks, exclusive of every other consideration.
159. 2of case.—The summit-level in this is the same as in the first
case J the secondary supplies also the same, with the difference that
Darby's branch is the first used in the valley of the Seneca. The
reservoirs are also the same. The summit-section is 11 miles 73J
yards in length ; the difference between this and the summit-section
of the first case being the sole cause of difference in the demand of
water between the two, it is not necessary to repeat the statement, in
reference to water, in detail.
The total quantity required is - 44,295,172.107 cubic yards.
Total quantity available - - 14,875,247.700 " "
Deficiency - - - 29,414,924.407 " "
160. This route is, therefore, impracticable; and, as in the first
case, it will be perceived that the quantity of available water is but
little more than half the quantity required for the mere use of the
locks, in passing the trade.
161. I have now applied the general rules which have been deter¬
mined, to the peculiarities of those lines which had been the subjects
of previous report, and in reference to which the decision of the Ex¬
ecutive of Maryland had been given, that they were impracticable in
reference to due supply of water. It will be seen that I agree with
40
that opinion, and consider thcni impracticable also. Whether I am
right or wrong, is for others to decide. I believe myself to be right,
and have fairly exposed all the rea.soning upon which my opinions
are founded. The facts to which my reasoning has been applied
were not collected by myself, as before remarked, (8 ;) this duty was
committed to the engineers Kirkwood and Lee, and without inter¬
ference beyond general directions, and a reference to former reports
on the same subject. The preliminary observations which have gov¬
erned my opinions were digested and written out before the surveys
were completed, and, of course, before I could have any anticipation
of the opinion they might induce in reference to these surveys. My
object was, to establish certain general principles, and, being satisfied
with their correctness, to follow them out, no matter to what conclu¬
sions they might lead, or with whom they might compel me to dlfier.
Difierence of opinion with some one was inevitable, as engineers of
deservedly great fame had already given diametrically opposite
opinions on the same subject. With both, it was impossible to agree.
But such differences are not unusual. In matters which, like these,
do not admit of mathematical precision, they are difficult to avoid.
We find accounts of them in the works of foreign engineers ; and,
therefore, the less surprising in our country, where a more limited ex¬
perience has done so much less in settling rules for practical operations.
If I have had any advantages over those who have preceded me in
this matter, it has been solely in the more time at my disposal, and
the greater means in my power to apply to the e.xeciition of the sur¬
veys, which have probably enabled me to collect more, and with
greater care, the facts upon which an opinion can be founded.
162. It was remarked (148) that three distinct lines had been sur¬
veyed. Having reported upon two, it now remains to bring the per
culiarities of the third and last to notice : we shall call this, by way
of distinction, " the Brookville route," as it passes near that village.
Brookvillc roule.
163. The summit-section of this route is 16 miles 1,506| yards
long, connecting, on the one side, with the Seneca, at the mouth of
Whetstone branch, and on the other with the Patuxent, at the mouth
of Hawling's river. Refemng to a bench-mark of Mr. Trimble's sur¬
vey, near Mr. Griffith's, with which the survey of this line was con¬
nected, its summit-level is 375 feet above mean tide, and 120 feet
below what has been heretofore denominated "the Seneca route,"
and between S and 9 miles south of it. The greater depression over
any other surveyed route, by which this line (the Brookville route)
is made to pass the intervening ridges, gives to it great advantages,
particularly in reference to supplies of water. It will require two
tunnels : one in passing the Rockville ridge, 2,800 yards long ; and
another in passing the Mechanicsville ridge, 2,600 yards long ; after
which it enters the valley of Reedy branch, a tributary of Hawling's
river. The total length of tunnelling will, therefore, be 5,400 yards,
or 3 miles 120 yards.
41
164. The line will admit of an arrangement of six reservoirs, viz :
1st. One on the Seneca, with a dam 40 feet high, a surface of 152.66
acres, containing 4,314,955 cubic yards, and receiving the drainage
from 10,908.16 square acres.
2d. One on Goshen branch, with a dam 20 feet higli, a surface of
94.123 acres, containing 2,065,266 cubic yards of water, and receiv¬
ing the drainage from 4,613.13 square acres.
3d. One on Hawling's river, with a dam 45 feet high, a surface of
96.648 acres, containing 2,548,450 cubic yards of water, and receiving
the drainage from 6,515.2 square acres.
4th. One on the Patuxent, with a dam 50 feet liigh, a surface of
336.685 acres, containing 11,039,352 cubic yards of water, and re¬
ceiving the drainage from 21,863.04 acres.
5th. One on Cat-tail branch, with a dam 40 feet high, a surface of
331.383 acres, containing 7,444,741 cubic yards of water, and re¬
ceiving a drainage from 17,648 square acres.
6th. One on Big branch, with a dam 30 feet, high, a .surface of 40.404
acres, containing 900,463 cubic yards of water, and receiving the
drainage from 2,497.92 square acres.
165. The dams in some of these reservoirs will admit of being
raised higher, if necessary, so as to contain more water without any
unfavorable extension of surface.
166. The total development of all the feeder-lines of the reservoirs
amounts to 15 miles 903 yards. The feeders, however, so iiniteas to
form but two points of connexion with the summit-level.
167. The total extent of drained surface being 64,015.44 acres, it
will yield at the rate of 29 inches of rain ; and, on the supfiosition that
one-third of the same can be collected, an amount of 83,229,611.09 cu¬
bic yards of available water.
168. We will now see what amount of water will be required, on
the supposition of 10 months or 300 days of navigation.
1st. To fill the canal - - 909,774.500 cubic yards.
2d. Leakage at locks
3d. Filtration and evaporation
4th. For the trade
5th. Loss from feeders -
6th, Half an inch per day loss from
reservoirs, for 365 days
Total required
Total quantity available
Surplus . . -
1,999,995.000
do.
18,195,490.020
do.
26,666,666.666
do.
11,376,199.999
do.
17,206,399.000
do.
76,354,523
do.
83,229,611
do.
6,875,088
do.
169. The Brookville route may therefore bo pronounced " practica¬
ble, with due supply of water " In this, as well as in the other cn.ses,
the rate of loss frotn the reservoirs was not applied to the maximum
surface when full, as given in the preceding description of the several
routes, but to a reduced average surface, on the supposition of a pro-
6
42
portionate reduction of the water in the reservoirs from the use of the
canal.
170. In the investigation of the peculiarities of this route, some
facts weie collected leading to the probability that, from G to S miles
still further south, a route might be ascertained that would reduce the
tunnel length. These facts developed themselves only in the plotting
of the experimental lines, and at a time when it was not possible to
to pur.siie further investigations in the field, which would have requir¬
ed an entire snrv.'y of a new line, with an entire new arrangement of
reservoirs and feeders, and a siirvev of all their numerous details.
,i7l. It will be seen that I have limited rny report to the single ques¬
tion involved in the résolutions of the Legislature—"practicability,
with due supply of water." An estimate of probable cost can be
made, if desirable.*
173. These surveys having cost more than had been anticipated by
myself, it is proper that I should explain the causes of it. In the first
place.it was not contemplated that il would bo necessary to survey any
01 her than the Liiigimore and Seneca routes ; but, in the prosecution
of these, a third (ihe Brookville route) manifesting itself, and with such
advantages over eitlier of the others, it was also surveyed. This last
route involved as many details, and as much labor nearly, as the other
two ; so that the actual cost will he found not to have increased beyond
the original estimate more than in proportion to the actual increase of
labor beyond what had at first been anticipated.
173. In conclusion, I consider it a duty to acknowledge my obliga¬
tions and thanks to Messrs. Kirkwoodand Lee, the principal engineers
under me, and to whom the surveys were committed, for the intelli¬
gence, the zeal,the industry, and economy with which their operations
were characterized.
Respectfully submitted :
J. J. ABERT.
DECE.mber 10, 1S38.
• The estimate is now beinj made.
Lawrence
CorifTwr
Jones
Sappinton
Slzane
Teener
744
Mountz
'■Sicrnt Mül
'Owens
Lingan,g, 2Ells
To oh
OlcLMOl
Bens -87-.^^
TrospectM-Sj
'orsey
Gosntl
Yfarfield
Tatapsco River
MAF
COFS^TRir
I1I8B Oír
^rrdtm
Brown
Welsh
COOKHVILLK
BASIN OF THE CAT TAIL BRANCH
MARYLAISTD CANAL
W.JRton^ So. Wcosh
BamSt
495*
'am
EtchinsonsJfrU,
i461
•ews
■J)am
Rarb^
j Rant. /'
•iaÁ^lphó^Tactnry
Magruder
Adwi
Waters
RordsMvU
Rarcy
Scale of Mile s
'reen's Bridge
luldis 3ranch
lUandm^^
factory-
Waters
Benson-
ßraetcb.
22^
JVîdowt
'am
frame-
Triée
•Ram
tagruder-
Whetsto,
OthoMagruder^
Clapper
insltij
Tomfrey
Rouglass
é.fol. Owen
-Berkwifh
OwerisMilt
References
Lines of Rrainage are expressed thus
Canat Litre
Litiganore, Rttute ■
Feeders
Canal Line
BrooTcvMe
The SeigTits of prominent paints are referred to mid tide at the City of Baltimore
and are given in feet
Compiled byT.JRee from amuü Surveys made inl838