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32X

f-^'

t:x «4 (^ i.

ON THE

GEOLOGICAL FORMATIONS

LAKE SUPEEIOK.

By THOMAS MACFARLANE

(From the Canadian Naturalist for May, 1867 J

Tlic ciystallino rocks of Lake Superior present many features
of interest to the lithologLst, and to the student of primary
geology; and the sedimentary rocks of that region, being ahnost
destitute of organic remains, have been the subject of much
discussion among scientific men, which can, nevertheless, scarcely
be said to have settled unequivocally the question of their age.
Having, as 1 believe, observed certain new facts i^oncerning the
compositior; and association of these rocks, which aie calculated to

throw some light on tlieh* origin and age, I have attempted to
describe them in the following paper.

Four different formations are distinguishable on the north, south
and east shores of the Lake, where I have had an opportunity
of examining their constituent rocks and mutual relations, but the
same formations may be observed elsewhere in this region. These
formations have been designated as follows: The Laurentian
system, the Iluronian series, the Upper copper bearing rocks of
La'ke Superior and the St. Mary sandstones. The two first-
named (and older) formations usually occupy those parts of the
shores which .form high promontoVies and prcciijitous cliffs, and
they constitute, almost exclusively, the areas which have been
explored in the interior. On the other liand, the Upper rocks
and St. Mary sandstones are never found far inland, but occur
close to the shore in comparatively low-lying land and rocks.
They seem to have had, as the theatre of their eruption and
deposition, the bottom of the Lake, at a time when its surface was
at a higher level than it is at present, although not so high as the
general surface of the surrounding Laurentian and Huronian hills.

I. — THE LAURENTIAN SYSTEM.

Under this name it has become usual, in Canada, to class those
rocks which, in other countries, have been regarded as forming
part of the primitive gneiss formation, of the primary or azoic
rocks, or of certain granitic formations.

The most prevalent rocks of the Laurentian series on Lake
Superior present a massive crystalline character, partaking much
more of a granitic than of a gneissic nature. Some of these I shall
endeavour to describe first. To the north of the east end of
Michipicoten Island, on tha mainland, there is a very large area
of reddish-coloured granite, which exhibits, in a marked degree,
the phenomena of divisional planes, and huge detached blocks.
The rock is coarsely granular, has a specific gravity of 2-6G8 to
5Z-676, and consists of reddish orthoclase, a small quantity of
a triclinic felspar, dark green mica (also in small quantity), and
greyish white quartz. The mica is accompanied by a little
epidote, and an occasional crystal of sphene may be detected. A
e.w miles to the east oi Dog River a grey granite occurs exten-
sively, which does not show any divisional planes. The felspar of
this variety is yellowish white, with dull fracture, and is fusible
without difficulty. It is associated with black, easily fusible
mica, in considerable quantity, and with quartz, which is occa-

pinnally bluish tinted. The ppecific jrravity of the rock ih 2-750
to 2-703. Liirijo-f^raincd granite is of very frequent occurrence
on Montreal Kiver and on tlie coast betwixt it and Point-aux-
iMines. It consists principally of ortlioclase, in pieces from one
to several inches in diameter, a comparatively small quantity ot
quartz, and a still smaller proportion of white mica. The
promontory of firos Cap, at the entrance of the Lake from River
St. IMary's, is composed of coa'-se-j^rained and characteristic
syenite. In some places its liornbleiide is soft, seems decomposed,
and is accompanied by epidotq. The rock is seldom free from
quartz, and some of it contains so nmch as to be justly termed
syeiiitic (rranite. A cliloritic <rranite appears to occur at a few
points on the north side of Bachewalmunt.' Buy, and a suiall-
grained f^ranite, consisting exclusively of fcls])ar and quartz,
occurs in large masses at the north-western extremity of the same
Bay. It has not the structure of granulite, and might be properly
named aplito or granitelle.

These rocks are all unequivocally granular, without a trace of
parallel structure. They far exceed in frequency and extent those
which possess a thoroughly gneissic character ; indeed, character-
istic gneiss was only observed at Goulais Falls and at Point-aux-
Mines. The rock of the latter locality varied from the closely
foliated, resembling mica schist, to that of a granitic character.
Granitic gneiss is found on the north shore of Bachewahnung Bay,
between Chippewa Biver and Bachewahnung Yillage, on the road
between the latter and the Bachewahnung Iron Mine, in the
neighbourhood of the BegUy Copper mine, and at other points on
the north shore of Bachewahnung Bay.

Almost equal in frO(|uency to these thoroughly granitic and
gneissic rocks, there are found certain aggregates of rocks which
present different lithological aspects almost at every step, and
which can only be generally described as brccciated and intrusive
gneissic, granitic, or syenitic rocks. There is, however, i:o bo
detected a certain unitnnuity in the manner of their association
with each other, which is of the greatest interest, and several
instances of which it is now proposed to refer to. On the north
shore of the Lake, about twenty-five miles west of Michii)icoten
Harbour, one of these rock-aggregates may be observed. Here
fragments of a dark schistose rock, consisting of felspar and horn-
blende (the latter largely preponderating), are enclosed in a
coarse-grained syenitic granite, and both are cut by veins ot

another pjranitc containiii<^ much less liornblende than the second-
mentioned rock. These veins are, in their turn, intersected by a
vein of tine-fjjrained ,u;ranite, consisting;' of (quartz and felspar, with
traces only of mica or hornblende. The specific fj;ravities of these
different rocks were found to be as follows: —

Ilornblendic schist 2-8.'}()

Syenitic granite 'J'7S7

Granite 2(508

Fine-grained granite 2()3()

That the specific gravity of the last-mentioned rock should be

greater than the one preceding, is attributable to its containing

more quartz. Figure 1 gives a representation of the phenomena

here observ^ed. No chemical analysis of these rocks is required to

Fig. 1.

a. Fragments of honibleudic schist.
h. Euclosing syeutic granite.

c. First intersecting granite.

d. Second Intorsoctinsj; OTauite.

show that the newer they are the greater are their contents in
silica. This is evident as well from their specific gravities as from
their mineralogical composition. The following relations, similar
to these are observable on the north side of the Montreal
lliver, at its mouth. The prevailing rock here is small-grained
granitic gneiss, which contains lighter and darker coloured portions,
according as the black mica which it contains is present in smaller
or larger quantity. A triclinic felspar is also noticeable in it.
Pieces of this rock are seen to be cut ofi" and enveloped in a

fiiior-jrruined uranito, of a much lighter colour than tlio pjiioiss,
and coniparativcily poor in the bhick mica. The specific jrravity
of tlio <rnei,sH is 2-(Ht7, and that of the <rranite, 2'()4H. Veins of
lar;^o-<;rained trranito, containim^ very little mica, traverse both
of the rocks just mentioned. The appearance of these rocks
is shewn in Figure 2. At tlic falls of the Chi]»pewa or

rig- 2-

'mrnm^^.

'//O'/'j"'/'' - • • * ♦. ^

a. Granitic gneiss. | h. Fine-grained grani«e. | c. Large-gmined granite.

Harmony River, which empties into Bachcwahnung Bay, the
predominating rock is highly granitic gneiss, consisting of reddish
orthoclase, quartz and dark-green mica. It is rather small-
grained, and, when observed in mass, shows sometimes a schistose
appearance, the direction of which ranges from N. 10° W. to N.
57'^ E. Occasionally, in the more micaceous portions, broad
felspathic bands occur, with selvages rich in mica, forming the
nearest approach to gneiss. The direction of these bands is
altogether irregular. This is also the case with veins of large-
grained granite which intersect the rock just described. This

granite consists inaijily of red ortlioclasc, witli a coini)arativt'ly
Miiiall ((uantity of (juartz, with wliicli a still sniaiU'i' (juaiitity of
urcenisli mica is associated. The spccitic gravity of the p-aiiitic
i^ni'iss is 2-l)7G, and that of tlie coarse-irraiiied rock of the veins
]i\}\)L On the north-east shore of tlu; JJay, ciosi! to the landing
place of the Jii\i:ley .Mine, rocks are observed consisting' jirincipaily
of granitic gneiss, in liand specimens of which, no parallel structure
can be detected. At some }>laces, however, in larger ma.sscs, a
schistose appearance is observable, with a strike of N. 75'^ E. This
rock, which is syenitic, contains masses and contorted fragments
ot gneiss very rich in hornblende. Both the fragments and
enclosing rock are intersected by veins of large-grained granite,
containing little or no hornblende or mica, Tn the most south-
easterly corner of Bachewalmung Hay, rocks occur, which, altliougli
they are totally devoid t)f any apj)roach to gneissie structure,
and possess ■ very different composition, bear some resemblance in
the manner of their association to those just described. A. dark-
coloured, snuill-grained mixture of felspar and greeidsh-black
mica, with occasional crystals of reddish orthoclase, and, more
rarely, of greenish-white oligoclase, is enclosed in and intersected
l)y another rock consisting of a coarsely granular mixture of
orthoclase and soft dark-green mica, enclosing crystal of orthoclase
(but no oligoclase) from one-quarter to three-quarters of an inch
in 'diameter. Both of the rocks might be called micaceous
syenites, but as they possess a ])delorphyritic structure, they
probably belong to the rock species called minette. The matrix
of the first-mentioned and darkest coloured rock is fusible,
but the orthoclase which it encloses is less readily so. In botli
vocks, where exposed to the action of the waters of the Bay, the
micaceous constituent has been worn away, and the grains and
crystals of orthoclase project from the mass of the rock The
specific gravity of tiic small-grained rock is 2'85, and tliat of the
coarse-grained enclosing rock 2-05. They are both intersected by
narrow vcms of granite, consisting of I'elspar and quartz only, tlie
specific gravity of which is 2.62. At Goulais Falls, about fifty
miles up the Goulais Bivcr, gneiss occurs, which is very distinctly
schistose, contains a considerable quantity — about onc-tliird — of
brownish black riiica, inter huninated with quartzo-felspathic
layers, in which a transparent triclinic felspar is observable. The
gneiss possesses a specific gravity of 2-7-1: to 2"7G. Its strike and
dip are variable ; the former seems, however, to average N. 55® E.,

and the liittcr vnrios fioui IP ) 20^ nortli-wostward. It is
iutert-itratilifd with u (^iiiall-tjraincd ;^'raiiitic giioisH, contaiiiin;:
much lcs!4 mica than tlu; hist — ahout oiio-twentioth oidy, — no
triclinic felspar, mid having a spccitic gravity of 27 1 to 272.
The same fjrranitic gneiss intersects tiie characteristic gneiss in
veins, and both of these roeks are cut by a coars(!-grained granite,
ahnost destitute of ndea, and coinjdetely so of schistose structure.
The strata of the gneiss are much contorted in various phices.
The iiiterse(!tiiig granitic gneiss and granite are alujost eijual in
({uantity to tlie gneis.s itself; and although they occur as irregular
veins, they are, at the point of junction, as firmly united with
tlu' gneiss as any two jiieces of one and the same rock could
well bo. Figure iJ is intended to represent the relations
observable at (Joulais Fulls. Between Goulais Falls and the

Fig. 3.

a. Gneiss. | h. Granitic gneiss. | c. Coarse-gnu ned granite.

point where the line of junction between the Laurentian and
Huronian rocks crosses Goulais River, there are numerous
exposures of gneiss()id rocks, but characteristic gneiss is of rare
occurrence among them. At several places hornblende schist,
in fragments, is observed enclosed in a gneissoid granite. Some
of them are longer than others, and have their longer axes
running N. 50^ to 60'' W. Hand specimens of the enclosing
granite show little or no mark of foliation, but when seen in

place, n faint parallel strticturo is olisorvablo, tlie strike of whieh
is N. M^ to (10^' W. Moth tlio lioriihlciiclic fra^;nicnt.s and
the jiiii'lssoid iiranitt! are cut l»y vins of newer uranite. On the
Honth-east .shore of (Joulais Hay. a heautifiil irroiip of wytMiitie
roeks is exposed, the mutual relati(tns of which are similar to tho.se
above <le.serihed. l''rairnient>of liornhlende rock or sciiist, varyinj^
from half-an-inch to three feet in diameter, arc; enclosed in a
coarse-LTrained .syonitie granite, in which, oeeasiotially, a rou<j;h
])aralK'li.-^m of tln'hornhleiidc individuals is observable, the direction
of which is N. 57*' K., and coincides with that of the longer axes
of the hond)Iendic iVajinuMits. The sitecific j,fravity of the horn-
blendie rock is 2'!t 4 to IMMI, and of tin.' enclosing:; uranite 2"74.
JJoth are intersected by a coarse-grained ur.-mite, havinj^ a spiicilic
gravity (tf 2-01 only, and containint;- little or no liornblende or
mica. The appearance here described are represented by Fit;'. 4.

a, IlorMl)Ien(lo seliist. h, Syenitie pneis^i-jrraiiile. e, Coarso-fjrainofl pranito

The mutual relations of the.'ie brccciatcd and intrusive
rocks in eij;'ht different localities, some of thoni upwards of one
hundred miles apart, have here been described, and it will be
observed that, in every one of the instances mentioned, the oldest
rock is the most basic in constitution, and this appears to be the
ease, without regard to the mineralogical composition or structure
of tiie rocks associated together as above described. It matters
not whether the older rocks be brccciatcd or entire, hornblendic or
micaceous, granular, schistose or porphyritic, it is always most
deficieut in silica. It appears, further, that the newer the rock

«J

wliich (Miclo.sos or iiciiotniti'H oldrr ones, tlu< inoro silicoous it
Ik'i'oiiu'S. Oti rcrcrctico to tlic »^[u'('ilic ^ravitioN nhovo «;ivt'ii ul'
tlif vnri<»uH rocks, it iiii^ht \h p(»sr<l that tlicir relations iin to
lii njrc; ini;^lit lie ('((iially well oxpreshcd l»y sayiiiLr, tlu; (ddor the rock
tlu! heavier ; the more roei'iit. the lighter it is ; and, in tlic
majority oC instances, thi." iij)|>li<'s. Htit, as in the case of thi' rock-
auizrcjate occurriiiu to the west of Mielilpicoten llarl)onr, wlieii
Ave come to the very newest trranitie veins, eiMisistinu cnly uf (irtho-
elasi! and (|nartz, those art; the heaviest whieii contain most of th(!
hitter mineral, its mean speelic gravity heini; 2'«>r), whil(! that ol'
orthoclasc! is oidy 'i'T)'). It is to h(! remendjercid that these newest
veins arc altojxotlHir ditterent in ai>|»earance from certain veins of
hiriie-irrained fxraiiito, witli distinct side joints, which nre occasion-
ally found intersectinti tliesc rocks, and the oriLiin of which lias
been indicated by l>r. Ifunt in lii.s recent valuable report on
mineral veins. Near I'oint-anx-Mines a vein of this nature is
found, the rock of which is jteuniatite, consisting of orthoda.se,
quartz, and <:reenish white mica, together with occasional grains
of ))iirple copp(!r, copper pyrites, jialena, ajid molybdenite.

It may not be out of jtlace here to advance certain considera-
tions reunrdin,:^ these Jiaurentian rocks, and especially concerning
the peculiar rock ngyrei^ates just described. The relations of
those rocks to each other we have seen to be as iollows : — The
older the rock the more basic is its nature, and the riclier it be-
comes in triclinic felspar, hondjlende, and mica. The newer the
rock the more siliceous it becomes, and the more such minerals as
orthoda.se and quartz predominate. It can scarcely be supposed
that this relation i.s an accidental one, for it is observable in every
one of the instances above given, the localities of many of which
are very far distant from each other. It would seem to be the
consequence of an unvarying law winch w^as in operation at the
time when these rock,; were first formed. At first sight, the facts
above described would appear to militate against the idea of the
igneous origin of these rocks, and, in fact, the relation is a similar
one to that which has been observed among the constituent
uiincrals of granite, and which is one of the chief difficulties in
explaining the origin of that rock on the igneous hypothesis. In
granite the quartz is frequently found filling up the interstices
between the other minerals, and sometimes it even retains impres-
sions of the shape of the latter. Nevertheless the felspar and
mica are the most fusible, and the quartz the most infusible of

the constituents of granite. Similarly, the older basic rocks, among
the brecciated and intrusive aggregates above described, are the
most fusible, while the newer rocks, being most siliceous, are most
infusible. At first sight, it is difficult to conceive how a basic and
fusible rock could solidify from a melted mass previous to a more
siliceous one. But the geological relations of these rocks are such
as to afford the fullest proofs of their igneous origin. It may be
urged that such an origin for the oldest and more basic fragments
does not appear proved, but their similarity in mineralogical
composition with the intrusive members of the aggregate is in
favour of such a view. Furthermore, these older fragments
shew, in every instance, such an analogy as regards their relation
to the intrusive rocks that they cannot be regarded as accidental
fragments of other rocks brought from a distance. If their origin
were of this nature, they would not invariably be more basic in
composition than the enclosing rock. The fact of their always
bearing a certain relation, as regards composition, to the enclosing
rock renders it unlikely that their source is similar to that o^
boulders in a conglomerate or fragments in a breccia. On the
contrary, it would appear more reasonable to regard them as the
first products of the solidification of the fluid mass from which
the granites, and other rocks above described, resulted. In
pursuing this subject further, it would appear not unreasonable
to base some such theory as the following upon the facts above
stated. The area now covered by these rocks must at one time
have been occupied by a mass of fused silicates. The temperature
of this fluid magma and of the surrounding crust has been
intensely high, although perhaps very gradually on the decrease,
and the extent of the igneously fluid material mu'st have been
such as to render uniformity in its chemical composition an
impossibility. Variations in its composition, as well as in the
maimer of its solidification, may therefore be supposed to have
obtained in different parts of the fluid area. According to th
proportion of silica and bases present where crystallisation com-
menced and progressed, hornblendic rock, mica syenite, or com-
paratively basic granite, first assumed the solid form, leaving a
part of the fluid or magma beneath or on the outside of it still in a
plastic state, but changed in its chemical composition, and rendered
more siliceous than the original magma. If the solidiflcation com-
menced at a point where the fluid mass was comparatively undis-
turbed, the granular varieties of the rocks above described may have

5 rocks, among
iribed, are the
20US, are most
w a basic and
)us to a more
ocks are such
. It may be
sic fragments
mineralogical
grcgate is in
LT fragments
their relation
as accidental
f their origin
iiore basic in
their always
the enclosinrr
r to that 0^
iia. On the
them as tlie
from which
jsulted. In
mreasonable
facts above
at one time
temperature
has been
he decrease,
have been
position an
1 as in the
ied| to have
ling to th
sation com-
te, or com-
leaving a
it still in a
id rendered
Jation com-
vely undis-
i may have

been produced. If, on the other hand, the solidification took place
while the fluid mass was in motion, the hornblendic and micaceous
schists and gneisses were most probably the results of this process,
and the strike of those would indicate the direction of the current
at the time of their Ibrmation. The rarity or indistinctness of
parallelism in the Laurentian rocks of Lake Superior shews, how-
ever, that no very constant and persistent motion in one direction
took place in the fluid mass which produced tliem. This first
solidification of part of the fluid magma most likely continued for
a long period, and i^pread over a large surface ; but there seems
at last to have arrived a time when, from some cause or other,
these first r(jcks became rent or broken up, and the crevices or
interstices became filled with the still fluid and more siliceous
material which existed beneath theni. Gradually, this material
solidified in the cracks, or in the spaces surrounding the fragments,
and the whole became again a consolidated crust above a fluid mass
of still more siliceous material. Further solidification of this
latter material doubtless then took place, and continued until a
second general movement of the solidified crust opened other and
newer crevices, which became filled with the most siliceous ma-
terial which we see constituting the newer veins among the rocks
above described.

Although the theory here given as to the origin of these rock
aggregates is in thorough harmony with the facts related concern-
ing them, it is doubtless possible to urge objections against it
founded upon the relative fusibility of their constituent rocks.
There is no doubt that the point of temperature at which these
various rocks become fluid under the influence of heat is higher
with the newer than with the older rocks, but it does not follow
that in cooling they solidify, that is, become quite hard and solid
at the same point of temperature at whicii they fuse. Bischof
describes ■•n experiment which proves that the temperature at
which ceri dn substances solidity does not at all correspond with
their fus-j .^. point. lie prep., red a flux, consisting of common
glass anu carbonate of potasli. which fused at a temperature of
800" II., and melted it along with some metallic bismuth in a
crucible. This metal fuses at 200^, and solidifies with a very
uneven surface, on account of its tendency to crystallize. Although
the difference between the fusing point of the bisnmth and of the
flux amounted to 600*^, nevertheless, when the crucible cooled, all
the irregularities of the surface of the metal were found to have

imprinted themselves upon the lower surfjice of the solidified flux,
a very plain proof being thus furnished that at a temperature of
200" li., the flux was still soft enough to receive the impression of
the solidifying metal. If we further observe the various fused
slags which flow from diff"orent furnaces, we shall obtain some idea
of the manner in which the rocks above described may have be-
haved during their solidification. The scoriae of iron furnaces are
usually very acid, containing as much as 60 per cent, of silica.
They generally fuse at a temperature of 1450° C. As they flow
out of the breast of the furnace, they may be observed to do so
very leisurely, to be sluggish an viscid, but nevertheless to con-
tinue fluid a long time, and even in some cases to flow out of the
building in which they have been produced, before solidifying.
On the other hand, slags from certain copper furnaces, or from
those used for puddling iron, are more or less basic, containing
from 30 to 45 per cent, silica. As they flow out they are seen to
be very fluid, and to run quickly, but they solidify much more
rapidly than iron slags. Yet these basic slags fuse at about 1300°
C, or about 150° less than the more acid slags. Those who have
been accustomed to observe metallurgical processes will not find it
difficult to conceive how a very siliceous slag might continue fluid
at a temperature at which a more basic one might become solid.
We conceive, however, that the rocks which we have described
must have solidified under circumstances altogether diff'erent from
those under which furnace slags cool. We suppose that these
rocks must have solidified at temperatures not very far below their
fusing points ; ihat the temperature of the atmosphere, and of the
fluid mass itself, had sunk somewhat beneath the fusing point of
the more basic rocks before solidification began, and that at this
point it was possible for the basic rocks to crystallize, while a more
siliceous magma still remained plastic. This latter supposition
does not appear unreasonable when the experiment above referred
to, and the behavior of furnace slags above described, is taken into
consideration.

It becomes a question of much interest as to whether these rocks
are to be regarded as constituting one and the same, or several and
distinct, geological formations. There cannot be a doubt as to the
fact that some of them are of more recent origin than others ; but,
on the other hand, many of the veins above described do not pre-
sent such distinct joints as are visible where trap 3r basalt dykes
traverse sedimentary strata. Although the cementing material

oftl

the

are]

uni

majl

othi

Hfied flux,
)eratiire of
pressioii of
ious fused
some idea
' have be-
rnaces are

of silica.

they flow
d to do so
ss to con-
out of the
)lidifying.
i, or from
iontuininff
re seen to
uch more
»ut 1300°
who have
lot find it
inue fluid
me solid,
described
*ent from
lat these
slow their
nd of the
point of
t at this
ie a more

3se rocks
eral and
as to the
rs ; but,
not pre-
t dykes
naterial

of the brecciated rocks above described difi'ers in composition from
the fragments which it encloses, we nevertheless find that the two
are usually so intimately combined with each other as to behave
under the hammer like one and the same rock. There is, in the
majority of cases, no joint to be Ibund at their junction with each
other; and in fracturing tliem, they very often break just as
readily across as along the line which separates them. It would
appear, therefore, that, although these rocks solidified at dilFcrent
times, the dates of their formation were not sufiiciently i'ar
distant from each other to enable the previously existing rock to
cool thoroughly before it became penetrated by or enclosed in the
newer one ; that consequently the older rock, being in an intensely
heated condition, readily amalgamated at its edges with the next
erupted and fused mass, and formed with it a solid compact whole.
Apart from the difficulties which would doubtless attend any
attempt to distinguish separate geological groups among these
rocks, it wculd appear just as unreasonable so to separate them, as
to r<i|gard each distinct stratum of sedimentary rock as distinct
geological formations. According to Naumann, a geological
formation consists of a series of widely extended or very numerous
rocks or rock-members (^Gcbirgs-glieder), which form an indepen-
dent whole, and are by their lithological and palfeontological
characters, as well as by their structure and stratigraphical suc-
cession (^Lagcrungs foJge), recognisable as contemporaneous (geo-
logically speaking) products of similar natural processes. According
even to this definition, it would appear just to class all the rocks
above described, in spite of the distinctly intrusive character of
some of them, as belonging to one and the same geological forma-
tion, — in short, to the Laurentian series of Sir W. E. Logan,
or the Primitive Gneiss formation of Naumann. The last-named
geologist certainly distinguishes a separate granite formation, but
the rocks included in it are generally more recent than the primi-
tive gneiss or primitive schists. Where, as in Silesia, in Podolia on
the Dnieper, in the central plateau of France, in Finland, in Scan-
dinavia, and in the Western Islands of Scotland, granite occurs
in similar intimate association with gneissoid rocks as on Lake
Superior, Naumann always regards it as part and portion of the
primitive gneiss. As early as 182G, Ilisinger, in his work on
Swedish mineralogy, shewed that the granite which occurs in
intimate combination, by lithological transition and otherwise, with
the primitive gneiss of Scandinavia, was of contemporaneous origin

with it ; and in the Pyrenees, La Vendee, Auvergne^ the Black
Forest and Huni?;ary, according to Coquand, Riviere, Rozet, Reng-
ger, and Beudaiit respectively, the gneiss and granite of these
countries cannot be separated into distinct formations, but form one
and the same mass of primitive rock.

II. — THE HURONIAN SERIES.

The rocks of this system, as developed on Lake Superior,
present at first sight rather a monotonous and uninteresting aspect
to the student of lithology. Largo areas are occupied by schistose
and fine-grained rocks, the mineralogical composition of which is,
in the most of cases, exceedingly indistinct. These rocks are, to
a very large extent, pyroxenic greenstones and slates related to
them. On closer examination, they are found to exhibit many
interesting features, and it is possible to distinguish among them
the following typical rocks : —

Dl((b((sc. — The granular varieties among these greenstones
belong to this species. It is developed at several points on
Goulais River, at some distance to the west of the Laurentian
rocks already referred to. It is usually fine-grained, pyroxene is
the preponderating constituent, and chlorite is present in con-
siderable quantity in finely disseminated particles. The felspar
is in minute grains, and, in many instances, it is only on the
weathered surface of the rock that its presence can be recognized.
One variety of this rock from the Goulais River has a specific
gravity of 3-001. Its colour is dark green, and that of its
powder light green. Tlie latter, on ignition, lost 2-29 per cent,
of iis weight, and changed to a brown colour. On digestion with
sulphuric acid, 22-99 per cent, of bases were dissolved from it,
which circumstances would seem to indicate that the felspathic
constituent is decomposable by acids, and is therefore, in all like-
lihood, hibradorite. This rock is underlaid to the south-west by
greenstone schist, striking N. G5° W., and dipping 75*^ north-
eastward, and is overlaid by amygdaloidal diabase and greenstone
slates, striking N. GG'-' W., and dipping 49° north-eastward.
Granular diabase is also met with a few miles higher up the river
from the rocks just mentioned, associated with porphyritic diabase
and diabase schist, the latter striking N. 55° to C5° W., and dip-
ping GO'' north-eastward. Similar rocks were observed on the
hills between Bachcwahnung and Goulais Bay, and at several
points on the north shore of the lake between Michipicoten

the Black
•zet, Reng-
3 of these
t form one

''1

Superior,
ing aspect
■ schistose
which is,
ks are, to
elated to

bit many

)ng them

^enstones

oints on

urentian

"oxene is

in con-

5 felspar

'..^^.

on the

ognizcd.

specific

t of its

er cent.

on with

Vom it,

Ispathic

■

all like- '

west by

'!-'M^m

nortli-

enstone

stward.

le river

iiabase j

id dip-

on the 1

several 1

:)icoten

Harbour and Island. In the neighbourhood of, and on tjie road to,
the Bachewahnung Iron Mine, they are also plentiful. Not unfre-
quently the pyroxene in them assumes the appearance of diallage.

AugiUporphyrii . — The porphyritic diabase above referred to is
a small-grained diabase, in which arc disseminated crystals of
pyroxene, about three-eighths of an inch in diameter. The specific
gravity of the rock is 2901). Its fine powder has a light
greenish grey colour, which changes on ignition to dark brown,
2.01 per cent, of loss being at the same time sustained. Hydro-
chloric acid dissolves from it 2H'48 per cent, of ba*-u s.

Calcareous Diabase. — The amygdaloidal diabase above men-
tioned is the same rock as is termed by Naumann Kalkdiahase.
It is a fine-grained diabase, somewhat schistose, in which oval-
shaped concretions of granular calcspar occur. The latter are
not, however, always sharply separated from the mass of rock,
which is slightly calcareous. The amygdules, if such they can
be called, have their longer axis invariably parallel with each
other, and with the schistose structure of the rock.

Diabase Schist. — This rock occurs much more frequently than
either of those just described. It is, indeed, difficult to find a
diabase among these Huronian rocks which does not exhibit a
tendency to parallel structure, or which does not graduate into
diabase schist. But the latter rock occupies considerable areas
by itself, not only on Goulais River, but also on that part of the
north shore referred to in this paper. The liigher hills to the
north-east of Goulais Bay consist, to a large extent, of this rock.
Apart from its schistose structure, it possesses the characters of
diabase. For example, a specimen of the rock from the north
shore has a specific gravity of 2-985. Its powder, which is light
grey, changes on ignition to light brown, losing 1-43 per cent, of
its weight. On digestion with hydrochloric acid, it loses 14'21
per cent, of bases; and with sulphuric acid, 16-12 per cent. It
is fusible before the blow-pipe. Many of these schists are
pyritiferous and calcareous, and these graduate frequently into
greenstone slate.

Greenstone and Greenstone Slate. — The rocks above mentioned,
being small-grained, are recognizable without much difliculty ;
but, besides these, and occupying nmch more extensive areas,
there occurs finely granular and schistose rocks, many of them
doubtless of similar composition to the above mentioned diabase
and diabase schist. Where the transition is traceable from the

latter rocks to those of a finer grain, the same names arc perhaps
applicable. But since this is not always the case, it would seem
advisable to make use of other terms for them until their compo-'
sition is more accurately deternnned. The names aphanite and
aphanite slate have been applied to rocks such as these, but since
the former term has been applied by Cotta to compact melaphyrc,
it would seem better for the present to continue the use of the
otlier terms, compact i^reenstone and greenstone slate, especially
since the signification of the first of these has been so limited by
Naumann as to denote pyroxenic greenstones only, thus di.stin-
guisliing them from the hornblendic greenstones or Dioritcs.
These pyroxenic grcensioncs, or fine-grained diabases, frequently^
contain more chlorite than the coarser-grained varieties. They
are very frequent on the Goulais lliver, ia the district between it
and Bachewahnung Bay, and in the neighbourhood of the
Bachewahnung Iron Mine. One specimen from a point four
miles north-east of Goulais Bay yields 21 ^-l per cent, of bases to
sulphuric acid. Its powder is dark green, changing on ignition to
dark brown, and losing 1-72 per cent, of its weight. These
greenstones are seldom destitute of iron pyrites. Quartz never
occurs in them as a distinct constituent, and ev3n in veins It is
rare ; but there are a few occurrences of greenstones which are
lighter in colour, more siliceous, and harder than others, and
which have possibly become so by contact with quartzose rocks.
On the other hand, they are frequently found impregnated with
calcaieous matter. By assuming a schistose structure, these
greenstones often graduate into greenstone slate, an apparently
homogeneous rock, generally of a dark greenish grey colour and
slaty texture. The latter character is sometimes so marked, that it
becomes difficult to distinguish it from clay slate. The greenstone
slates however, would seem to differ from the latter rock in the small
quantity of water which they contain, their generally higher
specific gravity, and in their yielding nothing which would form a
good roofing slate. On the other hand, they are related to the
greenstones and diabase schists not only by gradual transition, but
in some of their physical characters. For instance, a greenstone
slate from Dog Eiver, on the north shore, of a dark grey colour,
has a specific gravity of 2-738, and loses 1-C2 per cent, of its
weight on ignition, in which operation the colour of its powder
chnnges from a greenish white to a decided brown. It yields to
hydrochloric acid lG-4-1, and to sulphuric acid 10-29 of bases.

e perhaps
)uld seem
ir compo-
site and
but since
elnphyrc,
30 of the
3.spccially
mited by
IS distin-
Dioritcs.
equeutly
They
itween it

of the
int four
bases to
lition to
These
z never
n& It is
lich are
rs, and
3 rocks.
2d witli
!, these
•arently
ur and

that it
enstone
e small
higher
form a
to the
)n, but
instone
:joIour,

of its
•owder
3lds to
les.

SUi<'eo)iii Sldfc. — In many places bands of such dark coloured
slate as that just described are interbedded with others which
are lighter coloured and more siliceous. Such banded slates may,
for instance, be observed on the north-cast shore of Goulais Bay.
Here the darker slate is very evenly foliated, ot a dark greenish-
<^vvy colour, and has a specific gravity of 2-li85. Its powder is
light green, changing on ignition to light brcvn, and losing 2'02
per cent, of its weight. It yields to sulphuric acid 10-75 of bases.
The rock of the lighter bands is highly siliceous, and in fusibility
c((nal to orthoclase. The powder has a reddish gvoy colour,
which changes on ignition to brownish grey, U-54 per cent, of loss
being at the same time sustained. Hot sulphuric acid removes
only :}'79 per cent, of bases. A similar association of slates is
found at a point bearing 41" 30' E.from the east end of IMichipi-
coten Island. Here, a series of lighter and darker coloured bands
of very decided slate occur, striking N. 78° to 80 ° W., and
dipping 50 '^ to 52 ° northward. They are overlaid by a band
of dark green slate, which contains granitic pebbles, and this band
is again overlaid by light coloured slates. Small bands may be
observed to leave the dark green slates and to join with those of a
lighter colour. The latter are not only lighter in colour, but harder
and less dense, and occasionally show ou their cleavage planes a
silky lustre. A specimen gave a specific gravity of 2*681, and its
powder, which was almost quite white, lost 1-12 per cent, on
ignition, becoming slightly brown. It fuses only in fine splinters,
and, generally, the fusibility of these slates is the greater the
darker their colour.

Chlorite. Schhsf. — Some of the greenstone slates occasionally
contain an unusually large quantity of chlorite, and sometimes so
much as to form chlorite schist. This schist forms the side rock
of the Palmer Mine on Goulais Bay.

Qnartzite. — This rock is of less frequent occurrence than I had
anticipated. It is most frecpient on the west and south-west side
of the hills between Bachewahnung and Goulais Bay, and in the
district north-eastwards from Sault Ste. Marie.

Jlemafite. — This mineral often occurs in such quantity as to
constitute rock masses. It will however be referred to under the
economic minerals of the series.

Greenstone Breccia, — The occurrence of angular fragments of
other rocks in the greenstones above described is by no means rare,
and the resulting breccias are common between Bachewahnung

and Goulais Bays. In the majority of nstanccs where the matrix
is granular, the fragments are angular ; on the other hand, where
the matrix becomes schistose, the fragments are generelly roumlcMl,
and there results the slate conglomerate so characteristic of the
Iluronian series.

Slate Coiighnnmtfe. — This rock is extensively developed at the
mouth of the Dore lliver, some distance to the west of ^lichipi-
coten Harbour. Its matrix is the greenstone slate above described.
The boulders and pebbles which it encloses seem, for the most part,
to be granite, and are rarely quite round in form. The most
of them are oval or lenticular shapud, and then their outlines are
scarcely so distinct as in the case ci those which approach more
closely to the round I'orm. Very trc(|uently those of a lenticular
form are drawn or flattened out to such an extent that their
thickness decreases to a quarter or half-an-inch, and they are
sometimes scarcely distinguishable from the slate, except by their
lighter colour. Part of the rock exhibits merclv a succession ol'
lighter and darker coloured bands, the former of which sometimes
resemble in form the flattened pebbles above-mentioned. On
account of the presence of these lighter bands, it is often impos-
sible to select a piece which may be regarded as the real matrix of
the rock. As in the case of some of the rocks above described,
the light bands are more siliceous and less den.se than the darker
' .les. The latter are, not unfre(|ucntly, calcareous. A specimen
of this character had a density of 2-7()8 to 2-802. Its powder
was light green, which changed on ignition to light brown, with a
loss of 2-75 ])er cent. On treatment with sulphuric acid, it effer-
vesced strongly, and experienced a loss of 3(585 per cent. Iron
pyrites impregnates the matrix (piite as frequently as calcareous
nuitter. The direction of the laniination in the matrix is parallel
with the longer axis of the lenticular pebbles, and where the boulders
are large (they seldom exceed twelve inches in diameter) and
round, the lamination of the slate winds round them, and resumes
its normal direction alter passing them. Occasionally a flattened
pebble is seen bent half round another, and, among the very thin
pebbles, twisted forms are not uncommon. The nature of the
pebbles, especially of those which have been flattened, is sometimes
very indistinct. The quartz is generally easily recognized in the
larger boulders, but the felspar has lost its crystalline character,
and the mica is changed into dark green indistinct giains, where it
has not altogether disappeared. Besides the granitic pebbles,

r»

there are others vvliieh scorn to consist of quartzitc. An idea of

tlic structure of this rock is attoniptcid to be i^iven in fij^ure 5.

Fig. 5.

es,

a. Graiiit J Ixnildov.s, and long drawn masses. h. Schistose matrix.
The manner in which those rocks are occasionally associated
with each other is calculated, as in the case of the Laurentian
rocks, to suggest to the observer some definite ideas regarding
their origin . Equally instructive is the manner in which they
adjoin tiio Laurentian areas at several points on the north shore,
between Michipicoten Harbour and Island. I paid some attention
to that point of junction which lies to the west of Eagle River,
the precipitous cliifs to the east of which consist principally of
diabase schist and greenstone slate. A few miles to the west of
those cliifs, and at a point bearing N. 29 ® E. from the east end of
Michipicoten Island, the Laurentian granite is penetrated by
enormous dykes of dense basaltic greenstone (having the peculiar
dolcritic glitter when fractured), which contain fragments of
granite. This greenstone is also seen in large masses, which c;i,n
scarcely be called dykes, overlying the granite and enclosing huge
masses of that rock, one of which I observed to bo cut by a small
vein of the greenstone. Fronj this point to Eagle River those
two rocks alternately occupy the space along the shore, seldom in
such a manner as to show any regular superposition of the green-
stone on the granite, but almost always more or less in conflict
with each other. The greenstone, however, becomes more frequent
towards the east, and at Eagle River it has almost wholly replaced
the granite, and assumed a lighter colour and an irregular schistose

structure. The strike of these .seliists is, at places, quite incon-
Htant ; they wind in all directions, and whi»t appear, at first si^rlit,
to be quartz veins, accompany tlieir contortions. On closer
inspection, however, of the laruost of these, they are seen to be of
granite, ^ ut whether twisted fragments of that rock or really veins
of it, is, at first glance, very uncertain. Observed superficially,
they have the appearance of veins, but they do not preserve a
straight course, and bend with the windings of the enclosing schist.
They often thin out to a small point and disappear, and, a few
feet or inches furt' n* on in the direction of the strike, reappear
and continue fiu' a short distance. Sometimes a vein thins out at
both ends and forms a piece of granitic material of a lenticular
shape, always lying parallel with the lamination of the enclosing
slate. Figure G is a representation of the phenomena here
described.

a. rragmeutvS and contorted pieces of granite.
1). Slates enclosing same.

At another point of junction, on the north shore, to the east of
that above described, there is a large development of similar
basaltic greenstone. Its constituents, with the exception of iron
pyrites, are indistinguishable ; it has a greenish black colour, and
a specific gravity of 3. Its powder has a dark green colour, which
changes on ignition to dark brown, with a loss of 1-79 per cent, of
its weight. It yields to sulphuric acid 18*41 per cent, of bases.

of
lar
on
nd
ch
of

It exliibits nuniorou.s (livi.sionnl pianos and u tcMidoncy to Hlaty
Ktructure, the direction of which is not, however, parallel with
that of the divisional pianos. It contaitis nuniorons IVa^nionts
and lonj; drawn contorted masses of liranite, which are l)est dis-
cernible on the worn surface of tlie rock, and not readily so where
it is fresljly fractured. To tlie eastward it chan^'es to a much
liarder li<;ht <^rey siliceous rock, liavinsj; a s])ecific j^rnvity of 27()i)
oidy. Tn fine powder this rock is white, but on ijiuition becomes
brownish, and loses tlS.'i per cent, of its wci<2;ht. It yields only
4-02 per cent, of bases to sulphuric acid. At one place it seems
to contain frajiments and twisted pieces of the dark ^rcenstci e, and
further eastward it assumes the character of a breccia, t "anite
frajjjments being enclosed in the slaty rock, which is at some points
darker, at others liy-liter, coloured. The fragments arc sometimes
quite angular, and Sv-^metimes rounded off, and not sliarply separ-
ated from the matrix. Their longer dimensions arc invarialdy
parallel with the lamination of the matrix. The distance over
which the transition extends renders it impossible to give any ac-
curate sketch of the phenomena described.

Similar relations are observable at the junction of the two
formations in the north-east corner of Bachewahnung Bay. Here
the greenstone is compact, but still possesses the glittering basaltic
fracture. The Laurentian rock is a highly granitic gneiss, and
pieces of it are enclosed in the dark greenstone, which at one place
seems to underlie the granite. A reddish grey felsitic rock, witli
conchoidal fracture, is observed at the point of junction. East-
ward from it banded traps occur, striking N. 55° W., together
with greenstone — breccia, and conglomerate. On ascending the
hills behind this point another breccia is observed, of whicli the
matrix is greenstone and the fragments granite.

With regard to the succession of these rocks, it will doubtless
be found a matter of very great difficulty to establish any such,
even if any order of superposition of a tolerably regular character
should exist among them. That this is not very likely to be the
case, will appear from the considerations yet to be advanced re-
garding the origin of these rocks. As to their general strike, it is
scarcely possible to give any such, but within certain limits a
tolerably constant strike may be observed. In the Huronian area,
betwixt Goulais River and Bachewahnung Bay, although there are
occasional north-easterly directions, the strike generally ranges
from N. 40° to N. 80° W. On the north shore it is generally

•>'J>

cnHt and went, H»'Mom (hn-iiitiii^ iiioro than 20° to tlio nortli or
Nouth of tliOH(! points. TIu) rollowinu (dwcrvationH were luado in
tho n((ij;hlionrlioo(l of Kn^do lUvor, iit [wjints wlicrc tlu- AntvH iip-
poaicd most regular: N. H.'t" K., dip 4')^ northward; N. 80^^ W.,
dip HI" nortliward; N. 45*^ K., dip .'Jt'^ tiortli-wcstward.

In tho forc^'niiiii; d(>si'ription an atlcuipt has hcciii made to
(U'linoatc! with li(U'lity thi-niost important loatur(\s(d' tlie lliironinn
lltrmation as dcvclojx'd on I^nko Snpcrior. It is now proposed to
fi'ivc a i'air uustraim'd interprt'tation (»r tlu; cijaraclm's stampc'd
upon tho rocks of that series. The fact (d' the Laurentian ^^ranite
beii -^ pierced, as above described, by lluronian rocks, and liie fact
of tlieir endosinii fraj^ments of such Liranite, prov(!s incontcstal)ly
tliat .some (d'thcni are of eruptive o"i,i>in, and of later aj;e tlian the
liaurentian series. The enclosure of the hu«;o sharj)ly angular
fragments of granite in the very basic grecn.stone, above described,
stands in intimate connection with the enclosure of smaller and
contorted granite (Vagmcnts n a matrix of similar chemical com-
position, but different (slaty structure. The appearanccH visible
near Kagle Jtiver, of which figure (> is an illustration, prove that
enclosed granitic fragments sometimes undergo modifications of
form through contact with certain Iluroidan rocks. In Foster
and Whitney's Lake Superior Kejuirt (Part II., pp. 44 and 45),
analogous phenomena are described, but the exactly opposite con-
clusion is arrived at, viz., that the gratiitc is in the form of veins,
and is the newest rock. There would seem to bo only the two methods
of explaining the facts described : cither the granite forms veins
penetrating the schistose greenstones, in which case the latter are
the oldest rocks, or it is in the form of contorted fragments, in
which case the enclosing rocks nnist be of eruptive origin. The
fact that the granitic fragments do not cut but run parallel with
the slates which enclo.se them, is the strongest argument against con-
sidering them to be veins. The supposition that tliey are long drawn
and contorted fragments seems to be most in harmony with the
facts stated, and with what is known as to the relative ages of the
Laurentian and Huronian rocks. The true explanation most
likely is, that the basic greenstone, after envolophig the granitic
fragments, continued for some time in motion, and, previous to
solidification, softened and rendered plastic the fragments, which
then became drawn out in the direction of the flow of the igneous
mass, and forced to accompany its sinuosities, and that the motion
of the fluid mass previous to and during solidification developed in

2:i

45),

con-

.•cins,

tliods

veins

er nvo

its, in

The

with

t coii-

rawn

h the

)f the

most

;itiitic

us to

v'hich

icons

otion

ed in

tlio <;ro(MistoiuMts schistose strncturo. T\w otlu^r fads, dosciilMMl
iihovo as observable at a considerable distance east of Kaj^le lliver,
shew that soniethini; more than a mere moditieation of form is
eansed l)y the action of basic p'constone npon granite fragments.
Not only ar(! the latter there observed to be enclosed in, softened by,
and twisted around with the L'reenstone, but tlie phenomena (»bscrv-
i>d fully justify tlu^ supposition that tliey have been dissolved in
it, that is to say. acifually fused in and incorporated with its ma-
terial. The frai^UKMits are seim to be firmly joined toi;ether with
tlio enclosinur rock, espeeially wluu'e the; latter becomes more
siliceous. Furthermore, tlieir sharp an,u;lcs are often rounded off,
indicatinii; plainly that these parts were first melted away by the
fluid f^reenstone. Moreover, the product of tiiennion of tiie lattcir
with the dissolved parts of the granite is plainly visil)le. It is the
siliceous slate rock described above as forming:; in places the matri.K
of the breccia. Tiiis siliceous rock, the specific j^ravity of whi(rh
is much lower than that of the lireenstone, is further seen to be
twisted about witli the latter in such a manner as, in its turn, to
envelope parts of the <j;reenstone, thus shewinjj; that motion assisted
the incorporation of tiie two. The reddish grey fclsitic rock,
mentioned as occurrinjr at the junction of the two formations in
tlie nortli-e!..-it corner of Bachevvahnunj>; Bay, has doubtless had a
similar origin to t'uit of this siliceous rock, and it is not unlikely
tliat the banded traps and fdates, so frequently found amonij;
lluronian rocks, are attributable to a similar mode of formation.
Closely connected with the breccias just alluded to, so far as rc-
,u;ards the cause of its peculiar structure, is the Tluronian slate
conglomerate. It is impossible to examine closely this rock with-
out bcin<i; impelled to the conclusion that its origin is not very
different from th;;t of the breccias ; that its matrix lias been a
fused mass, flowing slowly but constantly in the one direction ;
and that its boulders are merely fragments which have been lialf
melted and rounded off by contact with the igneous rock. The
oval, twisted, lenticular and long drawn forms of the boulders are
such as could never have been produced by ordinary attrition, and
they frequently furnish examples of such intimate amalgamation
with the matrix as are never found in aqueous conglomerates.
Further, tlie fact of the boulders being frequently drawn out into
what are simply bands of liglit coloured slate, not only disproves
the sedimentary origin of the conglomerate, but indicates the
manner in which the association of greenstone slate and siliceous slate

;i})ovc (lissoribod li;i vo hw.n formed, Tlicy li.'ivc Himply boon produood
wlioro no tumultiiouH motion wfiH at hand tliorou^lily to irujorporato
tlio material of the ^reenstono with that derived from the Koftened
fraLMiKiiitH, but when; a Hteady eontinuouH motion, always in the
one dirciotion. drew out the materials of the diffcirent HlatoH into
loni,' bands Huh by side with caeh oth(;r. It thus .seems to ns
r(!asonal>l(!, and (juito compatible with a weientific interpretatifm of
the facts above ;,'iven, to explain tlio ori;;in of by far the <,Teater
iiiiird)er of the above (snumcrated lluronian rocks upon a purely
if^noouH theory ; and it has occurred to us t})at many of the in-
stances oi' local metamorphism, recor<led by j.'eolo^ists, in which the
contact of an i;^n(!ou8 rock caused tl <; silicification or lamination
of anotluir, mi;.d)t be capable of thoroii^di explanation in a maruier
similar to that in which we have tried to account fiir the ori;^in of
till! breccias, con<:lom(!rates, riiliceous ^rcsenstones and ban<led slates,
wlii(;h constitute such a larire ]»art of the lluronian series.

The lluronian seri(!S, whatever its niod<' of origin may have
b(!(!n, must undoubtedly b(! re^'arded as an ind(!pend(!nt ^^[(lolo^'ical
formation. It has b(;(!n represcsnted as bein;^ " a, mixture of the
St. Alban's ^T-oup of the upper Taconic with thcTriassic rocks of
Lake Superior, the trap native-copper bearing rockn of Point
Kc(;wecnaw, and the dioritie dyke containin^i; the copp(!r pyrites of
Bruce mine on Lake llunni"''' but surely such a description
is based upon a misconception of Sir VV. E. Lo-j-an's views on the
subject. Until its discovery by Sir William, the liiuMnian formation
was unknown to jreolo^^ists as a s<!parate and independent system, and
even now it is ordy in comparativelv few countries besides Canada
that it has been shown to exist On a former occasion, in the
columns of the NuturaliM f [ endeavoured to shew that the
Azoi(r schists of T(!ll(!mark(;n, in Norway, were almost identical
in litholo^'ical characters with the lluronian rocks, and \)r. J. J.
I{i;^sby % shortly afterwards insisted upon the fact of their being
the same Ibrmations. J)r. Higsby is of opinion that the lluronian
also occurs on the l'j»pcr Loire, in France, and that it is a totally
distinct i'ormation from the Cambrian, with which it has hitherto
b(!cn customary to associate it. The Huronian forms part of
what Nauinann calls the primitive slate ibrmation.

* Marcou; TIio Taconic and Lower Si) ariun Kocks of Vermont and
Canada. '

t Vol. vii, p. IK?.
t Quart. Joura. Gcol. Soc. Vol. xix, p. 41).

V.H of

)tioii

II tlio

ation

, i»nd

un.'ida

in t.Iio

the

tical

J.J.

)eiii,^

)rii!iii

otiilly

luuto

i-fc of

it uiid

Hosidos tli(! black and t^roonirih black dykon which occur in th<^
nci^^hboiirhood of, and Htatid in oonncction with, Huronian rocks,
tiioro arc others which occur at a iistancc from Huronian anuiH,
and whos(! rockn differ soni<!what IVoin thoHC of that formation.
This in th(; cnno, for instance, witli a Hct of dykes which occur on
the W)uth-c;ist sliorc of Oouhiis H.-iy, cuttin;^ Laurent ian rocks.
Th(!y are tliere separated from iho. j^neissoid rocks by very distinct
joints. They vury in thickness from nine to Hevcnty f(!(!t, nnd
strike N. T'i*^ to 75S W. Tn the widiist veins the rocik is firu!
^'rained at tlie nnh and sjiiidl f^rained in the ccmtre, so thiit i-\o.u
there it is difficult to determin(! its cf)nstitu(;ntH. 'fhey seem,
however, to be dark f^reen pyroxene and j^(!yish felspar, with
magnetic and minute; ^'rains of iron pyrites. 'I'hc ro(;k has a
specific ^'ravity of 2974. Its powdcsr, from which a ma^^net (ex-
tracts ma'.Mietite, has a ^ey colour, which chancres on i^niition io
a dirty brown, with a lo.ss in weif^ht of 1(17 per cent. Ifydro-
chloric acid produces no eflervescencc, but removes 21 74 f>er cent,
ofba.ses. Sulphuric acid removes 20-83 per cent. The presence
of maf^netite and absence of chlorite would .seem to indicate; that
th<*- rock inclines mon; to the nature of dolerite; than diabase. A
similar vein of fine LT.iined rock pen(!tratcs the syenite of (Jros
Cap, on the summit of that hill, striking!; N. 40 ^ W. A v<!ry
larjjje ma.ss of small grained doleritic rock likewise t)ccurs at the
mouth of the Montreal River, on its south bank. It probably
forms a dyke of very \tn-<n', dimensions in the <(ranitoid pu-i.-s
there. It consists, seeminj^ly, of black aujrite, white; or •^•(;yish
white felspar (on some; of the cleavatrc; planes of which parallel
Htrisc are distinctly obs(;rv.ible), and majrnijtite. Its spee^ilif
gravity is 3-090. Its powdtir yields magnetite to the magnet, and
does not eff'ervesco on treatment with sulphuric acid, which re-
moves 11 -IS per cent, of bases. Other dykes of this nature cut
the reddish granite of the nf)rth shore opposite Micliipicot(!n
Island, and, nearer to Michipicoten Harbour, a sixty feet dyke of
diorite cuts the grey granite;. It is fine; graine;el at the; .sifle-s, but
granular anel e;ve;n porpliyritic in the; e-cntre;. Its diree;tie)n is N.
tllj * E. About a mile furtlieir east arie)tbe;r dyke occurs, which
se;ems te) ejontain fragments of granite. (Jlose te) the laneling plae;e;
e)f the Be;gle;y Mine, in Bae;he;wahnung Hay, a dioritic dyke, bear-
ing N. 80* E., cuts gne;i.s.se)id rocks Kurthe-r invcstigatiein is
necessary to determine what relation, if any, these dykes bear to
the Huronian series.

21)

III. Ui'PER Copper-bearing Series.

The name ol' the Upper Copper-bearing Rocks of Lake Superior
was fiiven to this series by Sir W. E. Lopjan, to distinguish it from
the Iluronian or Lower Copper-bearing Rocks. The geographical
and geological position, lower altitude, regular bedding, and pecu-
liar lithological character of these Upper Rocks cause them to be
easily recognised and readily distinguished from the Huronian.
They have been separated into an upper and lower group, the
latter of which seems, however, to be confiiieil to the north-west
parts of the lake. Along its eastern shore, between Sault St.
Marie and Michipicoteti, there are frequently found, betwixt the
water and the high Pluronian or Laurentian hills, narrow strips
or patches of the rocks of the upper group, which often jut out as
small islands into the lake, and doubtless extend out great distances
beneath its waters. Such limited strips of these rocks are found,
for instance, skirting the base of Gros Cap, along the south shore
of Bachewahnung Bay and at Cape Gargantua. But besides
these and much more important for the study of the upper group
of the Upper Copper-bearing series, there are occasional xtensive
developments of its rocks, many thousand feet in thickness, such
as at Cape Mamainse, ]Michipicoten Island, and Point Keweenaw
on the south shore. These rocks have been generally described
in the Geology of Canada as sandstones, conglomerates, stratified
traps and amygdaloids. In referring to them more minutely, the
following rock-varieties may be distinguished as belonging to the
upper group of the series : —

Graiinlar Mclophijre. — A large number of the rocks of this
series which have hitherto been described as traps and greenstones,
belong to this species. The simplest variety of it is seen at the
north-west end of Michipicoten Island, and consists of two
minerals only, a felspar and a greenish black mineral. The
felspar is the principal constituent, possesses a red, almost pink,
colour, which it loses on ignition, and being readily fusible and
but slightly decomposed by acids, is most probably oligoclase, or
closely allied to that species in composition. The dark coloured
mineral is easily fusible and has the appearance of augite. Some
of it appears soft and decomposed, and has most probably been
converted into delessite. These two minerals are combined into a
small grained, distinctly compound rock, which does not effervesce
with acids, and whose red colour is visible at a considerable

distance. It is veiy seldom however that this rock is observe*!
with such a bright colour, or with constituents so distinctly
separated. Much more frequently the felspar has a dark reddish-
brown colour, and the grains of augite or delessite have a very
indistinct contour. This is the case with some of the melaphyres
of Mamainse and CJros Cap. When the brown coloured felspar
predominates, and the augitic or chloritie constituent becomes
scarcer and even more indistinct, rock-varieties are developed
belonging to the sj)ecies Porphyrite, hereafter to be described.
When, on the other hand, the dark greenish constituent gains the
upper hand, and is recognisable as consisting almost exclusively
of delessite, it gives rise to the variety of melaphyre next
described.

Delessitlc Melaphi/re. — This rock has a greenish-grny colour,
and consists of a granular mixture of felspar and delessite, with
small portions of nuignetite and undecomposed augite. In some
instances mica is also found as a constituent. The delessite,
besides occurring in small grains, often fornjs larger rounded
particles and amygdules, without however imparting to the rock
n a very marked amygdaloidal structure. The rocks enclosing the

cupriferous beds of the Pewabic and Quincy Mines, and that from
the Quincy adit are examples of this variety, and have already been
described by me in this journal.* The delessite which enters
so largely into their composition can scarcely have been one
of the original constituents, and has probably resulted from
the gradual alteration of augite, since authenticated instances
are on record of the conversion of that mineral into delessite and
green-earth. The specific gravity of these rocks varies from 2.83
to 2.89. When ignited they lose 1.82 to 3.09 per cent, of their
weight, the powder changing from light greenish-grey to a light
brown colour. Digested with hydrochloric acid from 32.44 to
35.72 per cent, of bases are removed from them, the greater part
of which belongs to the chloritie constituent. While the variety
of melaphyre first above described is seldom found with
amygdaloidal structure, the delessitlc melaphyres are exceedingly
prone to be developed as amygdaloids. In this case the rock
contains amygdules of small size but very numerous, and they are
either tilled with delessite alone, or are lined with a coating or
rind of that mineral, in which latter case calcspar generally

Vol. iii., Second Series, p. "i.

of the cavity. Quartz or
ainygdaloids the matrix of

agate
which

fills out the centre
comparatively rare in
delessitic melaphyre.

Compact Melaphyre. — When the small grained melaphyres
above described become so fine-grained as to render the recognition
of their constituents impossible, there results the fine-grained traps
which are so numerous on the south-west coast of Mamainse and
on Michipicoten Island. These rocks vary from reddish, bluish,
greenish, or greyish black, to decided black in colour, and possess
not unfrequently conchoidal fracture and resinous lustre. Their
specific gravities vary from 2.67 to 2.898, and they fuse before
the blowpipe to glasses of black or brownish black colour.
Occasionally their material becomes less homogeneous, and presents
the appearance of an intimate mixture of reddish grey and green
coloured specks, which may perhaps represent partially developed
constituents. They exhibit various phenomena as regards
divisional joints. Some possess a rudely columnar structure,
others have planes of separation forming various angles with the
plane of bedding, several shew a tendency to separate into flags,
w' ile a few instances are observable of curved shaly separation,
(Krummschaah'ge Ahsonderung) . Transitions can frequently be
traced from these compact melaphyres to others approaching in
character to porphyrite. For instance, to the west of the entrance to
the harbour on the south side of Michipicoten Island, there is found,
forming part of a bed of undoubted compact melaphyre, a rock of
a greenish-grey colour, with conchoidal fracture. It had a specific
gravity of 2.589, and could only be glazed at the edges before the
blowpipe. To the east of the same harbour entrance, another
rock occurs intermediate in character betwixt compact melaphyre
and porphyrite. It is black, impalpable, with imperfectly con-
choidal fracture. It bears some resemblance to pitchstone, but
difl'ers from that rock in its specific gravity, which is 2.774, and
in being readibly fusible to a black glass. It possesses a slightly
resinous lustre, and contains an occasional crystal of colourless
triclinic felspar. It exhibits planes of separation at right angles,
or nearly so with the inclination of the bed, and agate veins are
observable, which seem to accompany the divisional joints. This
latter phenomenon is also seen in some of the beds of compact
melaphyre, and in one of these, curved joints are visible, standing
at right angles to the plane of bedding and filled out with calcspar.
Brecciated quartz veins occasionally permeate these rocks, and

agatic geodes are very frequent among them. The latter are
sometimes so frequent as to form amygdaloids, but they are
nmch larger, and never so numerous as are the cavities in the
amygdaloids of which delessitic melaphyre is the matrix. There
is further this peculiarity with the amygdules of the compact
melaphyres, that they contain little or no delessite, agate occupying
its place, with occasionally calcspar filling the centre of the geode.

TufaceoiiH Melaphyre. — Interstratified with the rocks above
described, and much more frequently associating with, and gradu-
ating into the delessitic melaphyres than the other varieties, there
are occasionally found beds of comparatively soft, dark brown,
porous rock, with almost earthy fracture and seldom destitute of
amydaloidal structure. These frequently carry metallic copper,
and constitute the ' ash beds ' so extensively worked in the mines
of the south shore. Although they are generally of a dark brown
or chocolate colour, as in the case of the ' Pewabic lode,' there are
rocks of this species which are bluish-brown and green coloured.
The matrix is generally fusible, and in places impregnated with
grains of metallic copper, sometimes of a very minute size. The
larger grains of the metal are frequently found in the amygdules,
either alone or accompanied by green-earth, calcspar, quartz,
delessite, laumontite, and prehnite. Besides the rounded grains
or ' shot copper ' of the amygdules, these rocks often contain
huge masses of metallic copper, with which small quantities of
native silver are associated. Large irregular patches and veins
of calcspar, and smaller masses of epidote are frequently met with
in these tufaceous melaphyres.

Porphyrite. - The transitions, which are frequently observable
on the south side of Michipicoten Island, from compact melaphyre
to porphyrite have been referred to above. Undoubted porphyrite
is to be found at the south-west corner of the Island. It possesses
a fine-grained greenish red matrix, containing small flesh-coloured
crystals of felspar, some of which have striated cleavage planes.
The specific gravity of the rock is 2.619, and the matrix is
fusible at the edges. In the upper part of the bed the matrix of
the rock becomes coarser grained, shewing distinctly felspar and
a darker coloured mineral as constituents, with the small felspathic
crystals still scattered through it. The felspar predominates in
the matrix and determines the colour of the rock, which is dark
red. Its specific gn'vity is 2.626, anc. it is fusible, although not
readily, before the blow pipe. It separates into blocks, with very

}'■:

I*.

tlocided divisional phmcs, but of no regular form. Similar rocks
aic found at the south-east corner of the Island, where also rocks
rescniblinjj; pitchstone and pitchstooe porphyry are extensively
developed. The black shining impalpable trap, which has the
appearance of })itclistone, has a specific gravity of 2.573. It is
fusible to a brown glass, and sometimes contains small colourless
felspar crystals. Where these accumulate, there results the rock
resembling pitchstone porphyry. The crystals in this rock are
frequently recognisable as triclinic. The matrix is fusible to a
brown blebby glass, and the specific gravity of the rock as a whole
is 2.t)31 to 2.678. Since the specific gravity of the rock in which
no crystals occur is lower than that usually ascribed to melaphyre,
and since it is greater than that of true pitchstone, it would
appear reasonable to class both these rocks with the porphyrites,
or with these porphyries which contain no quartz, to which they
probably bear the same relation as true pitchstones bear to felsitic
or quartzose porphyries.

Melaphi/re Breccia. — Among the newest of the beds of compact
melaphyre, developed on Michipicoten Island, there are sometimes
observable beds of a breccia consisting of fragments of dark
brown melaphyre, cemented together by a reddish-brown trappean
sand. Occasionally the fragments appear rounded, and present
more of the character of a conglomerate. Similar rocks are seen
in the Point Keweenaw district.

Porpliyrltic Conghmerate.- At the south-west corner of Michipi-
coten Island there is visible a conglomerate bed, the boulders of
which consist principally of porphyrite, in which a few minute
felspar crystals are discernible. Some of the boulders are granitic,
and occasionally pebbles occur consisting of or containing agate.
These are enclosed in a matrix consisting of coarse-grained and
red-coloured porphyritic or trappean debris. In the upper part
of the Mamainse group similar conglomerates are found, but in
one instance the matrix seems to consist of the same crystalline
materi;d as the boulders and fragments, and is very firmly cemented
to these. The most interesting example of this rock is that of the
Albany and Boston mine, near Portage Lake. Here the matrix
of coarse-grained porphyritic sand is accompanied by calcspar, and
in some places fine metallic copper.* Other porphyritic conglo-
merates occur to the south of Portage Lake, some of the boulders

* This Journal, Vol. ill., Second Series, p. 9.

ii i

of which consist of quartzose porphyry, and the matrix of some
of which contains quartz as well as calcspar.

Frhite-tuff. — Ovcrlyinfi^ the Albany aud Boston conjnjiomerate a
bed of so-called ' fluckan ' occurs, which is a fine-grained, dark-
red shaly rock, in which pieces of a greenish blue colour are
sometimes seen. Both substances are fusible before the blow-pipe,
and contain occasionally small grains and flakes of copper.

Polyganovs Conglomtrafe. — This name is applied by Nauniann
and Zirkel to those fragmentary rocks whose boulders consist of
two or more different rocks. Conglomerates of this nature are
especially frequent among the inferior rocks of the Mamainse
group, and among those of Keweenaw Point. The boulders of
these Mamainse conglomerates are chiefly of granite, gneiss,
quartzite, greenstone, and slate, and some of tlie newer beds con-
tain boulders of melaphyre and amygdaloid in abundance. Tlie
matrix is generally a dark red sand tone.

Sundstone. — Among the melaphyres and conglomerates of
Mamainse and Point Keweenaw an occasional stratum of sand-
stone is found of the same character as that which forms the
matrix of the polygenous conglomerates.

The manner in which the rocks above described are associated
with each other, is much more regular than the architecture of
the Laurentian and Huronian rocks. They are regularly inter-
stratified with eacli other, and even among the melaphyres and
porphyrites distinct bedding is observable. They do not
seem to have been disturbed to such a degree as to occasion the
formation of anticlinal and synclinal folds, and in each of the
principal areas of distribution a tolerably persistent strike and dip
can be observed.

The general strike of the rocks of the Mamainse group is N.
203 to 50° W., and the dip 20'^ to 45» south-westward. They
are beautifully exposed along the west coast of Mamainse, and
the highest strata of the group form the south-west extremity of
the cape. The lower part of the group consists of granular and
delessitic melaphyres, polygenous conglomerates and sandstone. In
the upper part compact melaphyres and porphyritic conglomerates
predominate. The total thickness of the group, according to an
approximative measurement, is 16,208 feet, of which the conglo-
merates occupy 2,188 feet. The succession of the beds along the
coast is quite regular ; but on attempting to follow them inland,
they are found to thin out and disappear, while others take their

places. This is especially the caso with the conglomerates. Were
the beds continuous throughout, the section above given ought to
be repeated on the south coast, and round to Anse-aux-CrCpcs.
But there, although some of the mclaphyre beds have the same
strike and dip sis on the west coast, there in not the same regularity,
nor the same |ilcntiful development of conglomerates. There
are moreover evidences of great disturbances and of a conflict
between the rock of some of the igneous beds and a sandstone,
which here appears in highly contorted and sometimes vertical
strata. On coming round the south coast of Mamainse, from
Anse-aux-Cr6pes, strata of sandstone are observed very nmch
disturbed and dipping inland. As near as it can be ascertained,
their strike is about N. 85" W., dip 25° to 40° northward. The
sandstone is red coloured, and contains streaks and spots of a
cream coloured fel,<pathic substance, which also forms bands crossing
the stratification. Many thin cracks filled with calcspar also
traverse the beds. The same saiidstone continues for about a
hundred and forty yards further to the w')st, becoming still more
disturbed, and containing between its layers the felspathic
substance. The strike, where the beds are at all regular, is N. 10°
W., and dip 52° eastward. Further west it changes to N. 52°
E., with dip vertical, and in places 75° >S. W. Here the sandstone
becomes utterly broken up into a breccia, which has pieces from
one inch to a foot in diameter invariably angular, and a matrix
consisting of the white felspathic substance above mentioned, with
occasionally calcspar. Further westward the measures are
concealed for two hundred yards ; then strata of bluish-grey
calcareous sandstone are exposed, striking N. 40'^ E., and dipping
75° S. E. From this point for three hundred yards further north-
westward, disturbed sandstone occupies the coast where the
measures are not concealed. It is followed by a breccia similar
to that already mentioned, with angular fragments of sandstone,
and then by beds of trappean rocks, striking N. 75° W., and
dipping 40° S. W. Rocks of this nature occupy the coast, where
not concealed, for one and a half miles further north-westward.
Here sandstone again becomes visible, in strata almost vertical,
but nevertheless much bent. It is covered by a breccia consisting
of sandstone fragments with a trappean matrix, and this again is
surmounted by regular trap. In many places there would seem
to be the clearest evidence that the trap lies unconformably upon
the upturned and contorted edges of the sandstone. Besides the

breccia above mentioned, other rocks of a peculiar nature are
found at the junction of the sandstone and trap. One of these
is indistinguishable from quartzose plirphyry, and another seems to
consist of fragments of trap bound together by this same (juartzose
p^^phyry. There are good grounds for supposing that the latter
rock is the product of the action of the more basic trap upon the
sandstone, and results from the igneous amalgamation of the two
rocks last named. These confused rocks occupy about a quarter
of a mile of the coast. To the north-westward, although the
sandstones occasionally protrude, they become nmch less frequent,
while the overlying melaphyres become much more regular, and
gradually assume the same strike and dip as the strata on the
west coast. The hills to the north of Anse-aux-Crepes consist of
the same beds of melaphyre and conglomerate as were observed
on the west coast, with similar strike and dip.

The eruptive origin of the melaphyres and traps of this group
ip «^;videnced not only by their crystalline character, and by some
oi their relations in contact with undoubted sedimentary rocks,
but also by their occurring as intrusive masses in the gneiss of
Point-aux-Mines, and in the granitoid gneiss of Chippewa Falls.
At the latter place the melaphyre is in the form of a d\ke, and at
l*oint-aux-Mines it is seen to form a dome-shaped mass, completely
surrounded by gnessiod rocks. Furthermore, the lower members
of the Mamainse series are intersected by numerous dykes, con-
sisting of compact melaphyre. In some of them, the constituents
of that rock are distinguishable, but most of them are almost
impalpable, vary from a reddish-brown to a dark green colour, and
frequently exhibit at their sides bands of slightly different colours,
which run parallel with the side-walls of the dyke.

The average strike of the Upper Copper-bearing rocks of Michi-
picoten Island is N. 68'^ E., and the dip 25° south-eastward. An
approximative estimate of their thickness is as follows: —

Granular, delessitic and compact melaphyres,

and conglomerates 10,000 feet.

Compact melaphyres with agate amygdules. 4,500 "
Resinous traps, porphyrites and breccias. . . 4,000 "

18,500 feet.

If we compare the rocks of Michipicoten Island with those of
Mamainse, it would appear that the inferior rocks of the latter
group do not come to the surface at Michipicoten Island, and that

the higher rocks of thn Michipicotcn p;roup have not been de-
veloped at Miinininsi', or lie bcnejitli the wuti-rs of the hike to the
Houvh-west of the promontory. It would therefore iippear just, iti
eHtiiuatiii<^ the thicknes.s of the Upper Copper-heariiit^ rocks of the
eastern part of Lake Superior, to add to the jMaiuainse series tlio
abov3 nieiitioiu'd 40(10 feet of resinous traps or porphyrites, which
would make the whole thickness at least 2(^,000 feet. The rocks
of the west and soutii shores of Mi<'hij>icotcn Island present the
most reji;ular appearance, and it might be expected tliat those of
the soiith shore would, from their strike and dip, repeat them-
selves on the east side. But, as in the case of Maniainse, such an
expectation is disap})ointed. On examining the roeks of the east
shore, the upper beds, consisting of the porphyrites above men-
tioned, secni regular enough, but beneath these come breceiatcd
melaphyro, delessitie melaphyre cut by a porphyritic rock, and
others in which the evidences of bedding arc very indistinct.
Among these rocks the two following may be particularised as
occuring in large masses. The first has an impalpable flesh-red
or reddish-grey matrix, wherein occur numerous grains of dark
grey quartz, and also light-coloured soft particles, which
seem liable to removal by atmospheric agencies, giving
the rock where this has taken place a porous appearance.
It also contains light red and ash-grey crystalline grains of
felspar, and ' Miers which appear earthy and decomposed.
The matrix is fusible, in fine splinters only, to a white enamel.
The rock has an uneven fracture, a specific gravity of 2.493, and
is probably a porphyritic quartz-trachyte. The other rock, which
occupies a very considerable area, partakes more of the character
of felsit'"': jiio'-phyry, although the felspar crystals are very often
indistinct. It contains, besides these, numerous grains of greyish
(juartz, sometimes one-eighth of an inch in diameter, and a fine-
grained, dark red, difficultly fusible, matrix. The specific gravities
of three different specimens were found to be 2.548, 2.579, and
2.583. The bedding of the rock, if it possesses any, is very
obscure ; but it shews in places a tendency to separate into flags.
It has a very rough uneven fracture, and is probably also
((uartzose trachyte. At the north-east corner of the Island it
seems to overlie, unconformably, beds of trap, which here assume
something like the ordinary strike and dip, viz., N. 72"^ E., dip
25*^ 8. E.

The islands which lie opposite the mouth of the harbour on the

■! 'i

south shore are coniposoci of a peculiar rock, which is nowhere
visible on the main island. It consists of a reddish-brown ini-
palpable matrix, with a hardness but slij^htly inferior to that of
orthoclase, in which minute spots of a soft yellowish-white material
arc discernible. There are also li;j;hter flesh-coloured grains ol)-
servablo, which seem to be incipient felspar crystals. The njatrix
is difficultly fusible to a colourless blebby fi;lass, and the specific
gravity of the whole rock, where freshly broken, is 2.409. A
piece slightly bleached to a greyish-white, from its adjoining
a crack in the rock, gave a specific gravity of 2.477. Some parts
of it exhibit a slightly porous structure, but this was not the case
with either of the pieces whose specific gravity were determined.
The rock has a very uneven fracture, and is probably trachytio
phonolite. The occurrence of these traciiytic rocks on Michipi-
coten Island is very interesting, for they are the only ones of the!
region which have in other countries been found in connection
with undoubted volcanoes.

The general strike of the strata of the rocks of Point
Keweenaw, at least in the neighbourhood of Portage Lake is N.
30° to 40° E., and the dip 55^^ to 70° north-westward. The
melaphyres predominate, although polygenous and porphyritic
conglomerates are also frequent. The copper-bearing tufaceous
melaphyres seem to be more plentiful here than in the other
areas, or at least the mines to which they give rise are more
extensively worked.

At the other points in the east shore of the lake, where rocks
of the character of melaphyre have been observed, the area
occupied by them is very limited, and confined to narrow strips of
beach and rocky ground, between the lake and the much more
elevated Laurentian or Iluronian rocks. In the most westerly
cove on the south shore of Bachewahnung Bay, red sandstone is
observed striking N. 12'^ W., and dipping 15" south-westward.
It is interstratified with conglomerate, the boulders of which are
principally of quartzite, dark green slate and red-jasper conglo.
merate, which have doubtless been derived from the Huronian
hills in the rear. They range in diameter from one to twelve
and even eighteen inches. The matrix is generally red sandstone,
but the interstices are sometimes filled out with quartz. A short
distance along the shore to the north-east exposures occur of a
reddish-brown melaphyre tuflf, containing amygdules of calcspar
and quartz, the matrix of which is very soft and decomposed-

Tho bodM nprear to strike N. S" K., and dip 25"^ to 20-' weMt-
wnrd. They would thonsforo 800!n lt» bo cont'oriiinbh^ with tlio
H<'uidst(>!»n mid coiij;l(mierato. Kurtlicr Morth-oa.stwiir»l tlio rock
becomes more cumpuet, of ii reddish <j;ie(;n eoloiir, niid exhibits
curves of ij^neous flow. The ;.'eo(h's become imieh less tVe(pient
and consist almost exclusively of «;j^ate. The next rock to the
north-cast is a li;j;ht red sandstone, striking N. 05'^ W., and
dippinf^ Uf)"^ to •10-' N. K. Its contact with the trap is not
visible, but its dip is such as to lead to the supposition tliat it has
been disturbed bv that rock. There is u ijrreat thickness of this
sandstone exposed here, in strata fre(juently vertical, striking
generally cast and west, or to the north of west, and exhibiting
dips varying from ilf)-' N. to 57" S., and at least two anticlinal
axc8. From what has been stated here and also concerning the
south shore of Maniain>^c, it would appear that there is evidence
of the existence of a sandstone of greater age than the bedded
nielaphyrcs and conglomerates, and it would appear not unreason-
able to suppose that it belongs to what has been called tlie Lower
group of the Upper Copper-bearing series.

The trap rocks which surround the south-west base of Gros
Cap, although comparatively seldom amygdaloidal, are readily
distinguished as melaphyres. They arc sometimes coarse-grained,
cansisting of reddish-grey felspar, soft dark-green iron-chlorite
(delessite), and occasional .-^pots of yellowish-green epidote. From
this they graduate into finer-grained varieties, but they very
seldom become impalpable, or their constituents altogether indis-
tinguishable. Sandstone was not observed in contact with the
traps, but a large uiass of (juartzose porphyry is seen at a short
distance from the shore.

Another large development of traps and sandstones occurs to
the north of Pointe-aux-Mines, where an occasional bed of
tufaceous melaphyrc is also found.

Besides the rocks above described, there are found on the low
ground betwixt Goulais and Bachewahnung Bays, betwixt the latter
and Pancake Bay, and on many of the islands of the east shore,
large areas of red sandstone, almost horizontal, which are supposed
to be the continuation of that occurring at Sault St. Marie, and
usually called the St. Peter Sandstone. The true relations of this
rock to those of the upper group of the Upper Copper-bearing series
have not yet been made out. It closely resembles, in litliological
character, the sandstone described above as occurring in almost

;{7

lihits

iictit

tint

iitid

not

liiis

til I'm

vortinil ntriitii on tli.. south shore of* Hachowahiiuiii; Buy. 'Mic
(Hstiirl)imc(> of tho latter is reasonahly attributiible to the neij;h-
hourini; tiicl.'i'hyreM, in whieh cuho the Haudstoiie would Iki th«
earlii-r nx-k. On the other liund, as Sir W. K. Lopm observes,
'• the e(uitr;ist between th«! «reneral iuo«h'rat<' dips of these saiid-
•' stones and tlie hiirher inclination of tlu; ij,'iU'oiis .strata at
" (iar^jjaiitua, Maniains*-. and (Jros Cap, eonibined with the faet
" that the sandstones always k«.'ep to th<' lake side of these, whilo
*' none of the many dykes whieh eiit the trappean strata, it is
" believed, are known to intersect the sandstones (at any rate on
*' tho Canadian side of tho lake), seem to support the suspicion
" that the sandstones may o"(!rli<! uneonformably those rocks
" which, associated with the trup, constitute the copperbearinji;
*' series."-'^ Tho followin;:; facts ure confirmatory of this view.
Tn the bay immediately south (vf Point-aux-Mines, where the
Mamainse series adjoins the Iiaure;itian rocks, the lowest member
of the former is uneonformably (nerlaid by thin bedded bluish and
y(!llowish-<i;rey sandstones, strikin;^ N. 50*^ E., and dippinj:; 1^*^
north-westward. The lowest layer is a conglomerate, with t;ran;tie
and trappean boulders, and a bluish, fine-j:;rained and slaty matrix.
It is about six feet thick, and is followed by thirty feet of the thiu
bedded sandstones, some parts of which might yield good flag-
stones. Some of the surfaces of these arc very distinctly rippli;-
marked. Above these come thin, shaly, rapidly disintegrating
layers, in which are found .spheroidal concretions from five to ten
inches in diameter. It h not j)os,sible to a.scertain the total
thi(fkness of the.se sandstones, since they descend beneath the level
of the lake. They are similar in lithological chnractcr to the
sandstones which occur on the north side of Point-aux-Mines.
Although there is no doubt that these sandstones uneonformably
overlie the melaphyre series, still their lithological characters are
very different from those of the horizontal red sandstone above
referred to. The latter is evenly small-grained, is coloured red by
iron oxide, and contains here and there small pieces of red shale,
which liuvc evidently furnished the colouring matter. It
frequently consists of evenly bedded red and yellowish-grey
layers, and exhibits sometimes the phenomenon named by
Naumann, discordant parallel-structure, and byLyoll, diagonal or
cross stratification.

Geology of Canada, p. 85.

m «

(h-l 0^^

In enquiring next as to what geological formation iu Europe
most closely resembles the Upper Copper-bearing series of Lake
Superior, the opinion expressed by Delesse ought not to be lost
sight of, viz., that the constituent mineral^iave the same meaning
and importance for eruptive rocks whiclS-wganic remains have
for those of sedimentary origin. Therefore, where the pala3onto-
logical evidence does not entirely contradict it, that derived from
lithological resemblance ought to be allowed its full weight. The
melaphyres of the upper rocks being interbedded with conglomer-
ates and sandstones, the age of the latter may be ascertained
approximatively by enquiring under what circumstances and
during what period the melaphyres of Europe were developed.
Upon this point Naumann thus expresses himself : " With regard
" to the eruption-epochs of the melaphyres, there appears, indeed,
" to have been many of them, but the most occur in the period
" of the Rothliegende, or in the first half of the Permian forma-
" tion, and all are probably more recent than the Carboniferous
" system This applies at least to the melaphyres on the south
'' side of the Hundsriick, to those of the Thuringian Forest, of the
" neighbourhood of the Hartz, of Lower Silesia, Bohemia, and
*' Saxony. Many of these melaphyres were deposited soon
*' after the commencement, others towards the end, of the
" Rothliegende period, and generally the latter, in many coun-
" tries, shews a decided coincidence, both as regards time
" and space, with the formation of the melaphyres." Zirkel,
in his recent work on " Petrographie," gives a description
of the melaphyre deposits of Germany, of which the fol-
lowing is a translation: " In districts which are older than the
" Carboniferous formation melaphyre rocks are but seldom found.
" The melaphyres of the southern Hundsriick and of the Pfalz,
" whose stratigraphical relations are better known than their
" mineralogical composition, appear in the Carboniferous system
" or the lower Rothliegende. This melaphyre region extends
" from Diippenweiler to Kreuznach, a distance of twelve miles,
" with a breadth between St. Wendel, Birkenfeld, Kirn, and
'* firrumbach of several miles. Very few irregular masses are known,
" but, on the other hand, numerous veins have been observed with
" thicknesses varying from four to sixty feet. They possess
" mostly a vertical dip, cut sharply the Carboniferous strata, and
" often extend on their strike considerable distanw;. The mass
" of the vein frequently encloses fragments of the side rock, slate-

clay or sandstone. But most frequently in this region, the
melaphyres present themselves in the form of beds, which arc of
very variable dimensions, (often only five to ten feet, sometimes
two hundred feet thick,) and lie, for the most part, evenly
inserted between the strata i»f the Carboniferous system. Some
of these can be traced for a distance of two miles. Cesides
these a melaphyre layer appears in this rcj^ion, extending over
many square miles. It is superinq)osed upon the upper strata
of the Carboniferous system, andui>on it rest the Conglomerates,
sandstones and slate-clays of the Uothlicgendc. This great
covering of melaphyre is at its edges accompanied by melaphyre-
tuffs, which are in many places developed as melaphyre-amygda-
loids. In very few instances only has it been observed that
these melaphyres liave exerted altering influences upon the side-
rock. Within the limits of the Rothliegende melaphyres are very
frequent. According to Naumanu the melaphyre of Ilfeld in
the Hartz, must be regarded as a thick layer bedded into the
Rothliegende. It nevertheless in places lies immediately over
the Carboniferous system, on account of its extending beyond
the edges of the lower strata of the Ilothliegende. Naumann
also mentions a mass of melaphyre which in Tyrathal covers the
junction of the Greywaeke with the Ilothliegende, and in its
' further extension overlies also the latter formation. The
* melapb^.e-amygdaloid of Planitz, near Zwickau in Saxony,
' forms also a covering regularly inserted into the Rothliegende,
' above its inferior strata. On the western declivity of the
' Oberhohndorfer Hill, near Zwickau, the melaphyre which here
' contains numerous green-earth and calcspar amygdules, shews an
' interesting intercalation with the brownish-red slate-<'lays of the
' Rothliegende, irregular lumps and patches of which being as it
' were kneaded into the niass of the melaphyre. The melaphyric
' rock of the Johann-Friedrich and Zabcnstadter Adit, in Mansfeld,
' is evenly interstratified in the Rothliegende. G. Leonhard
' mentions that in the Rothliegende of the neighbourhood of
' Darmstadt, at Gcetzenhain and Url^erach, the melaphyre forms
' distinct outbursts of considerable size in the form of domes
' {Kuppcn,) which consist in the centre of solid melaphyre, and
towards the periphery of amygdaloidal rocks, and shews in
places both flagstone-like and columnar separation. In Silesia
the melaphyres appci'r in two places : in the country between
LoBwenberg and Lachn, where they, according to the investi-

I' I
I* J

r •

" gations of Beyrich, occur in several courses, striking from
" north-west to south-east, intersecting the Rothliegende, and
" in still more extended measure at the edge of the great
" bay opening towards south-east in the Grauwaclve at Landeshut,
" in which the carboniferous formation and the llothliegende
" have been deposited, and in which they form, according to Zobel
" and V^on Carnal, a range extending from Schatzlar to Neurode.
" In north-eastern Bohemia, according to Emil Forth, and
" Jok<?ly, malaphyres are found as numerous, and sometimes very
" thick layers, in the Rothliegende. Jok61y describes, in the
*' district of Jicin, five beds of nielaphyre in variou:-! parts of the
** Rothliegende, which exhibit very distinctly observable strati-
" graphical relations. They prove to be, for the most part, true
" nielaphyre streams, which have flown like lavas, and in visible
" connection with undoubted vein-like outbursts. According to
" Perth, the neighbourhood of the nielaphyre veins is fre(|uently,
'' for great distances round, a field of melaphyric ash and
" scoriae."-'^

From these quotations it is plain that, in Europe, nielaphyres
only made their appearance during the Carboniferous and Fermian
periods, and especially characterised the latter. The occurrence
of porphyritic conglomerates in Germany is similarly limited. On
this point Zirkel says : " As porphyritic eruptions principally fall
'* in the period of the Rothliegende, so the whole of the clastig
" rocks of the porphyry family stand in close connection with .he
" deposition of is strata, to which they have also contributed a
" considerable amount of material. For instance, coarse porphy-
" ritic conglomerates form members of the Upper Rothliegende
" in the Oschatz-Frohburg basin, in the Dohlen basin, at Wieser-
•' stiidt in the Hartz, and in the north-western part of Thiiringia.
" At Badeii, in the Black Forest, the deepest strata of the
" Rothliegende consist of porphyritic breccia and the middle
" strata of conglomerates." f Even polygenous conglomerates,
such as those above-mentioned, are especially frequent among the
carbi niferois and permiani strata of Europe. Naumann thus
briefly characterises the Rothliegende of Germany, which he
considers as equivalent to the English lower New Red Sandstone
and the French gres rouge : " The Rothliegende appears in so

* Zirkel; Petrographie. ATol. ii., p. 71.
t Zirkel ; Petrographie. Vol. ii., p. 529.

•' niaiiy of the couutrios of Germany, and in such great thickness,
"' that, in its mode of de^'elopment there, av>' recognise tlie normal
'• type of this remarkahle sandstone formation. The pigment of
" the sandstone, consisting principally of iron-oxide, the frequent
'• occurrence of conglomerates, the often repeated change in the
" size of grain of its rocks, the association with porphyries and
" melaphyres, the very frequent layers of claystones and porphy-
'• ritic conglomerates, the great poverty, and often contplete
" absence of organic remains. — all these are characters by which
'' the Ilothliegende is distinguished as quite a peculiar sandstone
" formation."'!'' That not om of the peculiarities here emphasised
by Naumann are absent from the upper group of the Upper
Copper-bearing rocks of Lake Superior, will be evident to any
one who has observed thorn or carefully gone through the
description above given. It therefore becomes a matter of .uich
importance, and deserving of the most careful study, to ascertain
whether this resemblance is a mere coincidence, or whether there
is reason for supposing that any part of these I 'pper CopiHir-bearing
rocks "Wft-of Permian age.

* >"auniann; Leliibueb dor Oeognosic. Vol. ii., p. 5H4.

CTCTbO"