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UNIVERSITY OF
TORONTO PRESS

Digitized by the Internet Archive
in 2010 with funding from
University of Toronto

http://www.archive.org/details/bulletinofmuseu0/7harv

BULLETIN

OF THE

{ '
Hatvarel

“MUSEUM OF OOMPARATIVE ZOOLOGY

AT

HARVARD COLLEGE, IN CAMBRIDGE.

VOL. Vil.

(Groxtocicat Series, L.)

CAMBRIDGE, MASS., U.S. A.
1880-1884.

613324
|

CONTENTS.

PAGE
No. 1.— Notes on the Geology of the Iron and Copper Districts of Lake Supe-
rior. By M.E. Wapswortu. (6 Plates) . ; : ; : : : 1
No. 2. — The Felsites and their Associated Rocks, North of Boston. By J. S.
DILLER. : - : - - : . 2 3 : : : . 165
No. 3.— On an Occurrence of Gold in Maine. By M.E. Wapswortn . 18)

No. 4.— A Microscopical Study of the Iron Ore, or Peridotite of Iron-Mine
Hill, Cumberland, Rhode Island. By M.E. Wapswortn . : : . 188

No. 5.— Observations upon the Physical Geography and Geology of Mount
Ktaadn. By C. E. Hamuin. (2 Plates) . : : . é : : - 189

No. 6.— Report on the Recent Additions of Fossil Plants to the Museum Col-
lections. By Leo LesquEereux : 2 . - : ‘ - F . 226

No. 7.— The Great Dike at Hough’s Neck, Quincy, Mass. By Joun Exior
WoLrFr. . : : : : ‘ : : ; : : P . 281

No. 8.— On some Specimens of Permian Fossil Plants from Colorado. By
Leo LESQUEREUX . : . : : : - - : : : . 248

No. 9. — On the Relations of the Triassic Traps and Sandstones of the Eastern
United States. By Witzt1am Morris Davis. (3 Plates) . ‘ : . 249

No. 10.— The Folded Helderberg Limestones, East of the Catskills. By
Wiriiam Morris Davis. (2 Plates) . Shell cant) by : : : - Sil

No. 11.—The Azoic System and its Proposed Subdivisions. By J. D.
Wuitney and M. E. Wapswort. ; es - : Gor ake . dol

CONTENTS.

eee ON ao sre GP es ete tote 8 ws ge LD

MEMO DISTRICE <- o s -cs.'s seen = « os . 1=%6

PEePO WeMuMe Ment, Seis eS ee et wl. eh sl)|6(1= 286
PPC SUMMARY. “sl. sic Ss . es se 626,97
PMMpeOUsTGOn OBSHEVATION |). 2: < s)s “s « »- « « « 27,28
er eASrnReAND TRON ORM —~. . si. 6) sw... . 28-36
Tue Basic Intrusive Rocks, ScHists, AND FELSITE . . 36-49
Se SMMMMCMGARENES 7 2. fs OE OMe ww kw 49-52
CRAnvEr GNEISS, AND QUARTZITE . .*. . . . ». » « 52-60
IRORSDAMESANIDSEONE Gc 2 ss) 6 6 se es 60
BERIDORELE AND IOHRPENTINE) 0. . « « « « « « « »« 60=66
GENERAL DiscussION AND RESULTS . ..... .. . 66-76
LUBE 90) 27 24 Bo) ote 9) Sd 0 229 Od 76—132
BETES ed | ee Ae 76-107
LUISHORMCATE SUMMARY. eo es os «6 « « o »« « »« L07=109
ECE ee eee ee ie te 6109-118
THE SANDSTONES AND CONGLOMERATES ... . . .- 118-122
faneVemns Ano Copper Debostrs . . . . . +. = « 123-127
CONCLUSIONS 127-132

PROSE PEEO ee se ee ew ee) «188-187

Pipe nteniONn OF THE PLATES ... . 5 =. . +s « 159-164

i Rabat
ge

na

No. 1.— Notes on the Geology of the Iron and Copper Districts of
Lake Superior. By M. E. Wapswortu.

TuerE are probably no regions of like extent in the United States that
have attracted greater interest or attention than the Copper and Iron
districts of Lake Superior. The most discordant views have been held
concerning their geology, and the origin of their ore deposits. There
are also probably no districts in this country which have been more accu-
rately studied, taking all of the conditions into consideration, than these
were some thirty years ago. The geology, including the origin of their
ore deposits, was then, for the time and methods of study, stated with a
remarkable degree of accuracy, so far as it has been our province to
observe or judge. It would not, then, be our duty to write concerning
these districts, were it not that the almost universal belief of geologists
at the present time regarding one, and in some respects the other dis-
trict, is so entirely at variance with the facts as we interpret them.
Before giving the facts it is necessary to present to the reader some of
the various ideas held regarding the geology of both districts. We shall,
however, in the main confine ourselves to those parts which we have
visited, except so far as observations elsewhere have a bearing upon our
work, or upon the questions which we wish to discuss.

It seems best to take up these views in chronological order, even if it
does impart a dictionary flavor to this paper. First in order, then, we
propose to discuss

The Iron District.

The earliest writer that it is necessary to quote here is Henry R.
Schooleraft, whose Narrative Journal of Travels, etc. was published at
Albany in 1821. He speaks of the granite at Granite Point (p. 158),
and of its being traversed by veins of greenstone trap. He gives the
composition of the former rock, and advances his reasons for considering
that it occupied its present position before the deposition of the over-
lying sandstone. He does not attempt to give the age of the sandstone,
although he thinks “its position would indicate a near alliance to the
‘old red sandstone.’ ”

VOL. VII. — No. 1. 1

4 BULLETIN OF THE

Dr. Douglas Houghton, in his first Report on the Geology of Michi-
gan, remarks upon the “appearance of primary and trap rocks forming
mountain chains, and the great disturbance which has taken place
since the deposition of the red sandstone,” and says that this sandstone
in the vicinity of Granite Point is “scarcely disturbed, resting upon
nobs of primary rocks.’ * In Dr. Houghton’s Fourth Annual Report,
for 1841,t the rocks of this region are described as primary ones, con-
sisting chiefly of granite, sienite, sienitic granites, and greenstone with
metamorphic rocks on their flanks, forming a stratified series consist-
ing of ‘‘talcose, mica and clay slates, slaty hornblende rock, and quartz
rock; the latter rock constituting by far the largest proportion of
the whole group.” He considered that the granite passed “almost in-
sensibly into a serpentine rock.” (/ ¢., p. 482.) In like manner, he
thought that the granites on the southeasterly side of the district
changed going northwesterly into a greenstone, and that the dikes trav-
ersing these granites were identical with the greenstone, having been
injected into the granite. His serpentine bears a close resemblance to
greenstone, and he states that ‘‘ possibly a more close examination may
show it to be a simple series of dikes, lying parallel to the line of cleav-
age of the slate rocks.” (/.¢., p. 494.) Regarding Presque Isle he says :
“This point of land has its origin from the simple elevation of a mass of
trap rock, which rises on the north in abrupt cliffs, varying from twenty
to sixty feet in height. The trap is mostly greenstone, though portions
of it are so largely impregnated with a dark-colored, almost black ser-
pentine, as to deserve the name of serpentine rock. The knob of trap
under consideration is possessed of additional interest, from the un-
equivocal evidence of uplift, as also from the manner in which these
evidences are exhibited. The cliffs of trap occupy the very extremity
of the point, while the neck and central portions are made up of con-
glomerate or trap tuff and sand-rock, resting upon the trap. These
upper rocks also appear upon the immediate coast, in cliffs of from
twenty to sixty feet in height, and in many places they are seen resting
directly upon the trap. The stratification of these sedimentary rocks
has been very much disturbed, and they invariably dip, at a high angle,
in all directions from the trap itself. The character of both rocks, at the
immediate line of junction, is almost completely lost, and the evidences
of change most unequivocally marked. But the most curious feature
of the whole is, that the sedimentary rocks, for a distance of several

* History of Michigan, by J. H. Lanman, (New York, 1839,) pp. 348, 352.
t Joint Documents, Michigan, 1841, pp. 471-607. ,

MUSEUM OF COMPARATIVE ZOOLOGY. 3

hundred feet, have been completely shattered or broken into minute
fragments, which, having retained their original position, were again
cemented by the injection of calcareous matter. This injection has
filled the most minute fissures, and so perfect is it, that, in looking upon
the face of a mural cliff of these rocks, the veins may be easily seen at
a distance of many rods, forming, as it were, a complete net-work over
the cliff, and so minute is it, that a single hand specimen frequently
contains many hundreds of these veins.” (/. ¢., p. 492.)

In this Report is the first mention of iron ore in this district that we
have seen. He gives amongst the minerals of the “ Metamorphic group
of Rocks,” “scaly red oxide of iron” and “hematite.” Regarding the
latter he says: “Although the hematite is abundantly disseminated
through all the rocks of the metamorphic group, it does not appear in
sufficient quantity, at any one point that has been examined, to be of
practical importance.” (/.¢., p. 504.)

In Dr. Houghton’s Fifth Report some remarks were made both
upon this district and upon the copper district, but nothing of special
importance was added.* Mr. George N. Sanders, in a report to the
Ordnance Office,t speaks of collecting “rich specimens of iron ore” on
the Menomonee River. In the same documents for 1845 — 46 ¢ are given
reports for the year 1845, by William A. Burt and Bela Hubbard.§ Mr.
Hubbard evidently considered that the ridges in the Marquette Tron
District were composed in the centre of eruptive rocks, but not outcrop-
ping, being “capped as well as flanked by the metamorphosed rocks.”
He states in regard to the metamorphic rocks that “these rocks are
throughout pervaded by the argillaceous red and micaceous oxydes of
iron, sometimes intimately disseminated, and sometimes in beds or
veins. These are frequently of so great extent as almost to entitle them
to be considered as rocks. The largest extent of iron ore noticed is in
township 47 north, range 26 west, near the corners of sections 29, 30, 31,
32. There are here, too, large beds or hills of ore, made.up almost entirely
of granulated, magnetic, and specular iron, with small quantities of spa-
those and micaceous iron. The more northerly of these hills extends in
a direction nearly east and west, for at least one fourth of a mile, and

* Joint Documents, Michigan, 1842, pp. 436-441.

T Senate Documents, 28th Cong. 2d Sess., 1844-45, XI., Doc. 175, p. 11.

{ 29th Cong. 1st Sess., VII., Doc. 357.

§ See also Senate Documents, 1849-50, 31st Cong. Ist Sess., III. 802-842, and
The Mineral Region of Lake Superior, by J. Houghton and T. W. Bristol, (Detroit,
1846,) pp. 3-39.

4 BULLETIN OF THE

has a breadth little less than 1,000 feet, the whole of which forms
a single mass of ore, with occasional thin strata of imperfect chert
and jasper, and dips north 10 degrees, east about 30 degrees. At its
southerly outcrop, the ore is exposed in a low cliff, above which the
hill rises to the height of 20 or 30 feet above the country on the
south. The ore here exhibits a stratified or laminated structure, and
breaks readily into sub-rhomboidal fragments, in such a manner as will
greatly facilitate the operation of quarrying or mining the ore. This
bed of iron will compare favorably, both for extent and quality, with
any known in our country.” (p. 22.) The sandstone is said to be found
frequently “surrounding, and in contact with, the uplifted masses of
igneous rocks, and is then invariably much altered both in appearance
and textures, and may, under such circumstances, fairly be considered as
metamorphic.” (p. 23.)

In the report of Mr. A. B. Gray to the Ordnance Bureau,* galena and
copper pyrites were said to exist quite abundantly, and that it was prob-
able that rich tin ores would be found. Mr. Samuel Peck is credited with
having first explored the iron region, and called attention to the exist-
ence of that mineral (/. ¢., pp. 15, 16).

Prof. H. D. Rogers t stated that the rocks in the vicinity of the
Chocolate and Carp Rivers (Huronian of Brooks) were “the equivalents
undoubtedly of the Primal sandstone and Primal slate,” or the Potsdam
sandstone of the New York survey.

Mr. William <A. Burt, in his report “with reference to mines and
minerals for 1846,” + (pp. 849 -852,) described “fourteen beds of mag-
netic iron ore” in this district. Mr. Bela Hubbard in his report for the
same year (J. c., pp. 901-905) advances some views upon the passage of
one rock into another, as follows: ‘A feature peculiar to all the rocks of
the country alluded to as granitic, is their occasional trappose character,
and the rare occurrence of mica. The constituents which make up the
greater part are quartz, felspar, and hornblende; the proportions of
which vary extremely. Thus, while the general character is that of true
sienite, the absence of quartz in a distinct form often produces a green-
stone, while frequently the last-mentioned mineral predominates almost
exclusively, constituting a true hornblende rock, which is generally of
a crystalline structure, and usually has a slaty cleavage. Again, quartz

* Executive Documents, 29th Cong. Ist Sess., Vol. VII., No. 211, 1845-46, pp.
2-23. Am. Jour. Sci., (2,) Vol. V., 1848, p. 151.

+ Proc. Bost. Soc. Nat. Hist., April 1st, 1846, IT. 125.

$ Senate Documents, 31st Cong. 1st Sess., 1849-50, III. 371 - 935.

MUSEUM OF COMPARATIVE ZOOLOGY. 5

becomes the predominant mineral, constituting what may be denomi-
nated a quartzite... .. In a few instances tale was found to take the
place of hornblende, constituting a protogine. ... . We accordingly find
the sienites assuming a trappose character, and often undergoing so in-
sensibly the change from a granitic to trappean rock, that it is impossible
to distinguish where one begins, and the other ends. In the operation
‘of these changes, the excess of silica may be called in to account for
the metamorphic rocks of the country, and particularly for the abun-
dance of pure quartz in rocks and veins. . . . . Not only have
changes accompanied the contact of trap with other rocks, such as
have usually been referred to the heat of the injected mass when
in a state of fusion, but equally marked changes have accompanied
the conjunction of the szenites with the sandrock under circumstances
where the same causes cannot be called in; for the latter gives evidence
of having been deposited subsequently to the formation and uplift of
the former, and the szenzte was as often observed to have partaken of the
change as the sedimentary rock. Without going further into detail of
facts of merely scientific nature, it may be sufficient to say that it seems
more reasonable to attribute the metamorphism which has taken place
in both rocks rather to galvanic and chemical action than to igneous
causes, which are so generally called in to account for all these phenom-
ena. The rocks designated upon the maps as metamorphic, occupy,
as it were, beds amid the surrounding primary rocks; and while we
would avoid any theoretic conclusions as to their origin, it may be stated
that, throughout the whole primary region, the limits of each rock,
except in the case of dikes, are seldom distinctly defined, but one passes
into the other by gradual transition; so that often rocks of distinct
name and character can be considered only as members of the same for-
mation, the constituents of which have become differently aggregated.”

Mr. J. W. Foster, in his report to Dr. Charles T. Jackson, dated Sep-
tember 28, 1848,* describes part of the iron region. The rocks are con-
sidered to be older than the sandstone, which is regarded as belonging to
the oldest paleeozoic rocks. Previous to this, Dr. John Locke attempted
to describe the district in part; but his account appears to be of no
value, except from an historical point of view.f We would, however, call
attention to his bathetic description of the “ Pictured Rocks ” (pp. 189 -
191).

* Senate Documents, 2d Sess. 30th Cong., 1848 — 49, III., Doc. 2, pp. 159 - 163 ;
Executive Documents, III., Doc. 12, pp. 159-163.

t Senate Documents, Ist Sess. 30th Cong., 1847 - 48, II. 186-189, Oct. 25, 1847.

a

6 BULLETIN OF THE

Pages 371-801 of a publication previously mentioned* is devoted to
the publication of the reports of Dr. C. T. Jackson and his corps. This
document is one of the curiosities of geological literature, —a rara avis.
Jt was printed in such a manner that in many cases it would be very
difficult, if not impossible, to determine who were the authors of the.
different parts of the text, were it not for the fusillade all along the line.

Dr. Jackson gives (pp. 477-479) some account of his first knowledge
of the iron ore (1844) in this district, but it seems that he never visited
the region himself. Dr. John Locke, in his field-notes for 1847 (2. ¢., pp.
572-605), describes the rock of Presque Isle as ‘a light-green trap, re-
ticulated, with white veins near the junction of the sandstone, with which
the trap is apparently interfused.” He also describes the iron region to
some extent. He considers that the trap rocks are frequently interfused
with the metamorphic ones in the district, and states that certain quartz
veins “deserve close examination for gold, silver, and other rare metals.
Veins of this description, if they prove important, can undoubtedly be
found in the metamorphic rocks.”

It is well known that the early explorers had to contend with very
great difficulties in their work in this region; but probably none ever
suffered such aggravation of spirit as did Dr. Locke, when, on July 27,
1847, his compass ran wild and its poles stood seventeen feet and eight
inches apart, unless it was when he found his provisions were only a few
sticks of wood and a bucket of bean soup.t Mr. J. W. Foster, in his
report to Dr. Jackson, dated May 26, 1849 (/. ¢., pp. 773 — 785), gives
a description of the iron region, as studied by him in 1848. He regards
the iron ores as sedimentary deposits. ‘‘These beds, so far as I have
observed, present a marked similarity in mineralogical characters, and
derive their origin from common causes, and those were aqueous. The
jointed structure and waved stratification of some of the beds prove that
igneous causes have operated, since their deposite, to modify and change
their character.” (p. 776.) ‘‘ Here, they certainly bear upon their sur-
faces strong marks of their mechanical origin. They are regularly
stratified, and often contain thin seams of silex in minute grains, so
that a specimen, on its cross fracture, resembles ribbon-jasper. The
lines of stratification can readily be distinguished from those of lamina-
tion. Like the slates, they are often found contorted and wrinkled, and
the same facts could be adduced in both cases to prove their common
origin.” (p. 779.) This description belongs, for the most part, to the

" * Senate Documents, Ist Sess. 31st Cong., 1849-50, III. 371-9385.

t Senate Documents, 1st Sess. 30th Cong., 1847-48, II., Doc. 2, -p. 190.

MUSEUM OF GOMPARATIVE ZOOLOGY. 7

Menomonee region, but part of the Marquette district is included. The
granites were classed by him as igneous rocks.

Printed in the midst of these reports is one from Messrs. Foster and
Whitney (/. c., pp. 605-626) made to the Land Office and Interior De-
partment, dated November 5, 1849, which gives some account of the Iron
and Copper districts. The iron is stated to occur in the metamorphic
formation. ‘This formation consists of hornblende, talcose, and chlorite
slates, with associated beds of hornblende and felspar rocks, evidently
trappean in their origin.” (pp. 609, 610.)

December 19, 1849, Professor J. D. Whitney gave some account of
this region before the Boston Society of Natural History.* The iron
ore was then stated to be of igneous origin. In a report trans-
mitted to the Interior Department, October 25, 1850,f Messrs. Fos-
ter and Whitney state that the sandstone is of Potsdam age. ‘“ Below
the whole of the silurian rocks we meet with a class of deposites
which were probably detrital in their origin, but which have been
so metamorphosed as essentially to change their structure. They are
destitute of organic remains, and contain imperfect traces of strati-,
fication. They consist of various schists and beds of quartz, marble,
and specular and magnetic oxide of iron. We have termed these vari-
ous groups the azoze system,—a system which, thus far, has not been
fully recognized in Europe, but the existence of which the results of this
survey, as well as that of Canada under Mr. Logan, have fully demon-
strated. Upon the upturned edges of these slates the Potsdam sand-
stone is found reposing in a nearly horizontal position. They form
the nucleus around which the newer rocks have been deposited, and
are extensively developed between the shores of the two lakes. They
are the depositories of the most extensive beds of iron known in the
world.”{ The term “ Laurentian” was first proposed by Sir William
E. Logan, in 1853,§ for the metamorphic rocks underlying the Pots-
dam sandstone north of the St. Lawrence, although it had been used
some years before by Mr. Edward Desor to designate certain drift de-
posits in the St. Lawrence valley, and by the law of priority the name
should have been retained in its original sense.

May 5, 1851, a paper was presented to the American Association ||

* Proceedings, III. 210-212.

+ Senate Documents, 2d Sess. 31st Cong., 1850-51, II., Doc. 2, pp. 147-152.
t See also Bull. Soc. Geol. France, 1850-51, (2,) VIII. 89-100.
§ Report of Progress Geol. Survey of Canada, 1852-53, p. 8.

|| Proceedings, V. 4-7.

.

8 BULLETIN OF THE

by Messrs. Foster and Whitney, entitled, “On the Azoic System,
as developed in the Lake Superior Land District,” in which the dis-
tribution of the azoic rocks in North America was briefly pointed
out. The term Azoic was adopted by them from Murchison and De
Verneuil,* but limited in its signification by Foster and Whitney .
“to a class of rocks supposed to be detrital in their origin, and to
have been formed before the dawn of animal or vegetable life. It
comprises the most ancient of the strata which form the crust of the
earth, and occupies a distinct position in the geological column; being
below the Potsdam sandstone. In this district, the rocks consist, for
the most part, of gneiss, hornblende, chlorite, talcose, and argillaceous
slates ; interstratified with beds of quartz, saccharoidal marble, and im-
mense deposits of specular and magnetic oxide of iron. Most of these
rocks appear to be of detrital origin, but to have been greatly transformed
by long-continued exposure to heat. They are sub-crystalline, or com-
pact, in their texture, and rarely present unequivocal signs of stratifica-
tion. They have been subject to the most violent dislocations. In one
-place, the beds are vertical ; in another, reversed ; and in another, present
a series of folded axes. Intermingled with them is a class of rocks
whose igneous origin can hardly be doubted, and to whose presence the
metamorphism so characteristic of this series is, in a measure, to be
ascribed. They consist of various proportions of hornblende and feld-
spar, forming traps and basalts; or, where magnesia abounds, pass into
serpentine rocks. They appear, in some instances, to have been pro-
truded through the pre-existing strata, in the form of dikes or elvans ;
in others, to have flowed in broad lava streams over the ancient surface ;
and in others, to have risen up through some wide-expanding fissure,
forming axes of elevation.” Gaseous sublimations, intense pressure, and
electro-chemical agencies were thought to have assisted in the metamor-
phism, as well as the plutonic masses. ‘Since the theory of metamor-
phism has been generally adopted, many of the rocks which were for-
merly regarded as igneous are now referred to aqueous agency, and
their transformations traced to the presence of erupted rocks. They
here cited numerous examples of metamorphism, showing that argilla-
ceous schist is transformed into gneiss ; sandstone into compact vitreous
quartz; and limestone into saccharoidal marble, when brought in con-
tact with eruptive masses. They therefore inferred, that these obscurely
bedded rocks, — such as gneiss, and the crystalline schists, — were of
sedimentary origin ; that no rock was to be regarded as igneous, unless it

* Russia and the Ural Mountains, I. 10.

MUSEUM OF COMPARATIVE ZOOLOGY. 9

occur in vast, irregular masses, like granite ; in dome-shaped, or crater-
like summits, as basalt, or trachyte; in long lines, as dykes or elvans
cutting through the incumbent strata; in ramifying veins, like granite ;
or broad lava sheets, like trap. Many eminent geologists maintain that
the lowest stratified rocks are but portions of the Silurian System, and
that, from long-continued exposure to heat, the lines of stratification
have become obscure, and all traces of organic remains obliterated. Our
observations in this district (they remarked) have led us to a different
conclusion.”

“The evidence is ample that the base of the Silurian System reposes
upon their upturned edges, and that the causes by which the metamor-
phism of the former was effected had ceased to operate before the depo-
sition of the latter. Between the two systems there is a clear and well-
defined line of demarkation. It forms one of those great epochs in the
history of the earth, where the geologist can pause, and satisfy himself
of the correctness of his conclusions. On the one hand he sees evidence
of intense and long-continued igneous agency, and, on the other, of com-
parative tranquillity and repose. .... The Azoic Series was characterized
by immense deposits of specular and magnetic oxide of iron. This might,
with great propriety, be denominated the Iron Ace of Geology. ....
It was evident that these strata were everywhere plicated and folded,
and that the observer passed over a repetition of beds, instead of a suc-
cession of beds; but that the strata, throughout the whole region, had
been so shattered by earthquakes, and so metamorphosed, by direct or
transmitted heat, that it was impossible to identify them, except over
limited areas.” Later, attention was called to the point that this con-
tinent was as old as the European, if not older.* The above points
were given in much greater detail in Messrs. Foster and Whitney’s
“Report on the Geology of the Lake Superior Land District. Part IT.
The Iron Region, together with the General Geology.” Transmitted
November 12, 1851.t Such portions of this report as it is necessary to.
note will be touched upon below.

The range of quartzose hills extending from Carp River by Teal Lake
was described to some extent, and was regarded as formed from a
metamorphosed sandstone. Enclosed fragments of jasper and slate,
lines of bedding, and obscure traces of ripple-marks were said to have
been seen in this quartzite (/.¢., pp. 15, 16). Of Presque Isle they
suid: “The outline of this mass is very irregular, and resembles an im-

* Same Proceedings, page 151. “See also entire article, pp. 186-151.
t Senate Documents, Spec. Sess. 82d Cong., III., 1851.

10 BULLETIN OF THE

mense consolidated lava-stream, except that the vesicular structure is
wanting. ‘To the north, the surface of the igneous rock is bare ; but,
on the eastern side, it is covered in places with a rudely stratified mass,
which appears to have been deposited in the inequalities of the pre-
existing surface. It resembles a volcanic sand, or ash, portions of it |
being composed of a scoriaceous -mass of a light-brown color, and reticu-
lated with numerous veins of a white mineral, portions of which are cal-
careous, and others silicious.” (d. ¢., pp. 121, 122; see, also, pp. 18
and 92.)

This rock was thought to be of prior origin to the sandstone. The
sandstone was regarded as Potsdam, and as the same rock as that
on Keweenaw Point. It was pointed out that this sandstone rests
nearly horizontally on the water-worn edges of the nearly vertical
quartzite. (i. ¢, pp. 122, 123.) The iron ores were regarded as of
igneous origin, forming intrusive masses and overflows, principally the
latter, like a lava, but consolidated under pressure of a deep ocean.
Sublimations of the iron occurred while the denudation and deposition
of the eruptive masses that were by the shore-line aided in making the
different formations. After this series of igneous and aqueous ore-
beds were laid down, “the whole series of beds, slaty, quartzose, ferru-
ginous and trappean, were elevated, and, in all probability, folded, per-
haps at the epoch of the elevation of the granite ranges on the north
and south of the ferriferous belt of the azoic system.” (/. ¢., pp.
50-69.) *

Dr. J. J. Bigsby regarded the granite as igneous, and taught that the
metamorphic rocks had been “upheaved and altered by the intrusion
of igneous rocks in instances innumerable.” | Professor Whitney, in his
“ Metallic Wealth of the United States,” (Philadelphia, 1854,) again ad-
vocated the igneous origin of the iron ores in this district, as well as in
some other localities.t

In 1854 there was published by Henry R. Schoolcraft, in Philadelphia,
a work entitled ‘‘Summary Narrative of an Exploratory Expedition to the
Sources of the Mississippi River, in 1820: resumed and completed by the
Discovery of its Origin in Itasca Lake, in 1832. By Authority of the
United States. With Appendices, comprising the Original Report on

* Am. Jour. Sci., (2,) XVII. 11-38, 1854 ; XXII. 305-314.

+ Edinburgh New Phil. Jour., 1852, LIII. 55-62.

t Pp. 87, 429-437, 477, 478. See also Proc. Am. Assoc. Adv. Sci., 1855,
209-216; Mining Magazine, (New York, 1856,) VII. 67-73; Am. Jour. Sci.,
(2,) 1856, XXII. 38-44.

MUSEUM OF COMPARATIVE ZOOLOGY. 11
°

the Copper Mines of Lake Superior, and Observations on the Geology
of the Lake Basins and the Summit of the Mississippi; together with
all the Official Reports and Scientific Papers of both Expeditions.” As
giving us an insight into the early knowledge of the geology of the
southern shore of Lake Superior, this work naturally should be of great
value, especially as it purports to contain the original scientific reports.
In the Preface we learn that he brings the subject down to the date
of publication in some respects, and by comparing the work with the
original, published in 1821, we find that he gives discoveries as if made
by himself in 1820 which were not made until at least nearly twenty-five
years later. This insertion in the body of the text may perhaps be par-
doned, in the light of the Preface ; but when it comes to publishing offi-
cial documents with their original date and official signature, but with
a “tinkered” body, we object. We cannot therefore credit Mr. School-
craft with the discovery of the iron ore of the Marquette district in
1820, although any one reading this work would suppose that he dis-
covered it. It represents to us simply what he wished, in 1854, others
should think he had known and written in 1820. This also applies in
part to his reports on the Copper district, and we shall not mention the
book further.

In 1854 was also published a description of this and the Copper region
by Fr. C. L. Koch.* The trap and granite were regarded as eruptive,
and it was thought that the quartz rock (quartzite) may probably be so.
The schists are supposed to have been metamorphosed through the
agency of igneous masses. The iron rocks he would consider as
upheaved from great depths, or else to have suffered great metamor-
phism by the influence of igneous masses. That they (the iron rocks)
may be simply the quartz rock impregnated with oxide of iron is thought
probable.

In 1855 and 1856 two papers on this and the Copper district were
published by Prof. L. E. Rivot.t As we understand his work, it would
seem that he regarded all the rocks from Sault St. Marie to the Onto-
nagon River as of sedimentary origin, and of the same geological age,
whose differences were entirely owing to peculiar metamorphism, or its
absence, as the case might be. The sandstones were in general, in the
Marquette district, of prior deposition to the other rocks in the places
in which they are now to be found. The traps and their associated
schists, which originally formed the base of the sandstone, had been

* Studien des Gott. Vereins Bergm. Freunde, VI. 1-248,
+ Annales des Mines, (5,) VII. 173-328, X. 365-474,

BB BULLETIN OF THE

-

locally changed and pushed up, dislocating the surrounding sandstones.
The granites and sienites were regarded as probably the products of the
last stage of metamorphism, although they were eruptive in their pres-
ent position. The ‘‘diorites” of the Marquette district were considered
to be the same, in age and general characters, as the traps in the Copper .
district, all being interstratified with the sedimentary rocks with which
they are associated, and into which they gradually pass. The differ-
ences between them and their associated rocks were owing to the degree
and manner of the metamorphism. The whole formation from the Sault
to the Ontonagon was regarded as Potsdam, being overlaid by the
magnesian limestone.

Prof. J. P. Lesley, in his “Tron Manufacturers’ Guide,” (New York,
1859,) opposes the view of Professor Whitney, that the iron ores of
Lake Superior or of any other region are eruptive. It seems strange
that a geologist and mining engineer of his reputation should fall
into the errors that he has, in interpreting the latter's work. After
quoting Professor Whitney’s remarks on mineral veins, he says: ‘‘The
first theory which Mr. Whitney so summarily dismisses as opposed
to all known facts, is in certain principal localities the only one which
apparently embraces all the facts. The so-called veins of specular and
magnetic ore in Northern New York, New Jersey, and Missouri are of
this class, and when Mr. Whitney says that ‘the mountain masses of
Missouri have pre-eminently an eruptive character, and are associated
with rocks which have always been considered as of unmistakably erup-
tive origin,’ we must interpret the expression by the preceding and suc-
ceeding paragraphs as the judgment of the past, and not his own, saying
that the specular and magnetic ores of Lake Superior, New York, and
Scandinavia fall into the same category, and yet are not true veins, but
‘slaty beds impregnated with peroxide of iron, .... exhibiting the
appearance of a secondary action having taken place since their original
formation.’” (/. ¢., pp. 354, 355.)

On referring to Professor Whitney’s work, it can be readily seen that
the remarks on mineral veins by Professor Whitney have nothing what-
soever to do with the above quoted iron-ore deposits, which are not
mineral veins in any sense, and were distinctly separated from them by
him. The expression, “slaty beds, impregnated with peroxide of iron,”
was used in reference to the mine of Hessel, Norway, while the statement,
“ exhibiting the appearance of a secondary action having taken place since
their original formation,” was applied to the azoic ores of New York, and
is copied by Professor Lesley on page 357 of his work in its proper con-

MUSEUM OF COMPARATIVE ZOOLOGY. 13

nection. It will thus be seen that specials have been transformed by
Professor Lesley into generals, entirely out of their original use ; and
remarks about one thing are said to have been made about another.

After copying several pages from Professor Whitney’s ‘“ Metallic
Wealth,” he writes : “It appears from the foregoing that Mr. Whitney
accepts both the eruptive and the sedimentary theories of the formation of
the primary iron ores, and applies the former to unknown, invisible masses,
antecedent to and now deeply buried under all, even the oldest rocks
which appear upon the present surface ; masses of far greater size and depth
than the greatest yet discovered, proportionate to the greater scale of all
volcanic action in that pre-azoic day, and offering their sides and tops to
such erosion and solution as would of course happen in such unsettled
times, and be sufficient for producing the vast sediments of iron which
have been taken for volcanic outbursts of the molten metal. But there
is a fatal difficulty in the way of this hypothesis. These ore-beds are
not breccias. Deposits of the kind imagined would be conglomeritic ;
blocks of pig-iron would be seen scattered through strata of granite.”
Here, again, he has entirely misunderstood Professor Whitney's views,
which were that the great masses of ore in the Lake Superior district were
eruptive where they now are, and were never sedimentary deposits,
while associated with and derived from them are the brecciated and con-
glomeritic ores, as well as other sedimentary beds. If it is necessary, the
“pig-iron ” can doubtless be found at Ovifak, Disko, in the basalt (/. c.,
pp. 333 — 335, 353 — 361, 480 — 489).

In 1861 the rocks of the Marquette iron district were referred to the
Huronian system by Dr. T. Sterry Hunt, on the authority of Mr. Alex-
ander Murray.* Dr. Hunt regarded the Huronian then as the equiva-
lent of the Cambrian of the European geologists.

Dr. Danat states concerning the iron ore of Michigan and elsewhere :
Their alternation with chloritic and other schists and gneissoid rocks
shows that they are metamorphic as well as the schists.” The same
statement is made in the edition of 1874 (p. 74), and doubt is expressed
as to whether they belong to the Laurentian or Huronian (pp. 151, 152,
159, 160). Since the above was written the third edition of the Manual
has been published, but this affirms as strongly as ever that the iron
ore is in stratified sedimentary beds, and that it is distinctly interstrati-
fied with the schists.

* Am. Jour. Sci., 1861, (2,) XXXI. 392-414; Canadian Nat. and Geol., 1861,

VI. 81-105, VII. 127.
t Manual of Geology, 1862, pp. 83, 84.

14 BULLETIN OF THE

Later, Dr. J. J. Bigsby, while considering the Huronian as distinct
from the Cambrian, still referred the rocks of this district to the Hu-
ronian.* !

In the “ Geology of Canada,” 1863, these rocks are taken as Huro-
nian (p. 66). The rock at Presque Isle was classed as a sedimentary -
serpentine belonging to this formation by Dr. Hunt (pp. 472, 595);
taking his analysis from Professor Whitney’s work,t who regarded it as
closely related to serpentine.

Dr. Hunt states also that the great beds of red hematite are strati-
fied (p. 596), and he considers their deposition as proof of the presence
of vast amounts of organic matter at that day (p. 573).

Dr. J. P. Kimball, under date of December 19, 1864,¢ remarks : “ My
own observations in the Iron region impressing me with the indigenous
character of the larger masses of diorite and granite represented within
the defined area of the metamorphic strata, and their entire distinctness
from intrusive dikes or erupted masses, and concurring in the recog-
nition of these strata by Mr. Murray as Huronian, I am disposed to
regard the entire region as of metamorphic character, all of whose larger
masses of crystalline rocks are indigenous, and to be divisible into the
two formations, Laurentian and Huronian: the former formation proba-
bly forming the surface of the areas known as the granite ranges, while
the latter probably occupies, with minor deviations, the limits laid
down for the crystalline schists comprehended under the name Azoic.”
(J. c., p. 293.) “ Possessing the same stratigraphical conditions as the
schistose rocks, while many varieties of them are represented in the
schists by their exact counterpart as to composition, the crystalline
Huronian rocks must be regarded as essentially metamorphic, while in a
comprehensive view of the whole series it is seen that together with
variable conditions of deposit, it indicates variable degrees of local meta-
morphism. Plentiful evidence exists of the blending of a rock of one
character into that of the other, or the continuity between crystallized
and schistose beds... . . Besides the indigenous crystalline rocks dis-
tributed throughout the Huronian series, exotic or intrusive crystalline
rocks are met with, but only in the form of dikes, and limited to a nar-
row distribution.” (J. ¢. p. 295.) “It may not be inappropriate to
suggest the probability that the larger and more persistent bodies of
greenstone bearing approximately east and west — that is, conformably

* Quart. Jour. Geol. Soc., 1863, XIX. 36-52.

t Am. Jour. Sci., (2,) XXVIII. 18, 1859.
t Am. Jour. Sci., (2,) 1865, XXIX., 290 - 303.

MUSEUM OF COMPARATIVE ZOOLOGY. 15

with the axes of the folds which constitute a regular system of flexures
coextensive with the distribution of the Huronian series in the vicinity
of Marquette, are, in reality, indigenous greenstone, and a portion of the
development of the diorite upon which repose the upper members of the
series, and which, as will hereafter be shown, is uncovered along most of the
ridges of the region.” (/.¢., p. 296.) ‘ The position of the beds of specu-
lar iron ore has already been stated to be at the top of the Huronian series,
_ . .. interstratified with talcose and argillaceous schists. Sharing the
plications of the entire series, these specular schists, as they may prop-
erly be called, are accordingly folded into synclinal basins and anticlinal
crests.” (J.¢., p. 299.) “It has been shown that the iron ores of the Hu-
ronian series in Michigan are essentially schists and heav y-bedded strata,
in which none of the phenomena of aqueous deposits formed by precipita-
tion from water on the one hand, or by detrital accumulation on the
other, are wanting. They exhibit not only stratification, anticlinal and
synclinal folds, but are invariably traversed by systems of joints, and at
many points exhibit a perfect slaty cleavage. The intimate connection
between the greenstones, hornblende rocks, and aluminous and magne-
sian silicated schists of the ferriferous series, has already been indicated |
in general terms, these rocks not only alternating with, but passing into
each other.” (J. ¢., p. 302.) “Chemical reactions in crystalline sedi-
ments resulting from the disintegration of crystalline silicated rocks, and
operated upon by carbonated waters, are amply capable to have pro-
duced the lithological conditions of augitic rocks, clay-slates, schalstone,
and other schists, together with the oxidized ores of iron intercalated
with greenstone among the ancient crystalline rocks of North America
as well as of Europe. . . . . From a stratigraphical point of view, while
evidence is elsewhere often obscure, the Huronian greenstone, schists,
and iron ores of Northern Michigan, in the absence of close attention to
their special chemical conditions, exhibit sedimentary and metamorphic
phenomena adequate to render quite untenable, it is believed, the theory
of the exotic character of any portion of them.” (/.c., p. 303.) The
granite is also regarded as indigenous by Dr. Kimball.

Mr. J. W. Foster, in 1865,* states: “The Iron Region consists
of an assemblage of rocks of various kinds, such as argillite, talcose,
chlorite, and hornblende schists, quartzites, and occasionally dolomites,
all of which are supposed to be of metamorphic origin, intermingled
with rocks whose igneous origin can hardly be doubted, consisting of the

* Geology and Metallurgy of the Iron Ores of Lake Superior, by J. W. Foster
and J. P. Kimball, New York.

16 BULLETIN OF THE

various compounds of feldspar and hornblende, forming greenstone or
dolorite ; or where silica abounds, forming syenite ; or serpentine where
magnesia is in excess... .. It may be stated as a general rule, that
the great iron deposits of the district occur in close proximity to the
igneous rocks, mainly greenstone. This rock forms nearly all of the.
prominent peaks of the region, not in continuous ranges, but in a suc-
cession of dome-shaped knobs, while the iron ores repose upon their
sides, or dip beneath their bases, so that the greenstone appears rather
in the form of intercalated beds than as wedge-shaped masses. The
whole region has been subjected to a powerful denudation, and the
greenstone, being the more unyielding rock, has been left in the form
of knobs, or of ill-defined ridges. I cannot recall an instance where it
forms a true axis of elevation.” (J. ¢c., p. 9.) The limonitic ores (soft
hematites of the miners) are regarded by him and by Dr. Kimball as
formed by the decomposition of the hematite ores in situ (1. c., pp. 24,
81). Dr. Kimball also states in this report (p. 87): “Regarding the
bodies of specular iron ores and earthy red hematites of the Marquette
Region as of combined aqueous and metamorphic origin; and, condi-
tional to this view, apprehending the stratigraphic arrangement of the
general system of aluminous and magnesian silicated schists, among
which these beds are intercalated, generally regular and constant as it
is, the topography of the country affords tangible data for tracing the
hidden conditions of ore beds, and their relation to outcropping rocks.
The region is traversed by a series of folds, or undulations, of the entire
series of rocks, which impart to the surface its contour, modified only
through subsequent agencies of denudation. Thus the crests of the
undulations (7. e. the ridges and hills), originally overlaid by beds of
iron ore, which in its purer conditions readily yielded to the abrasion
of glacial action, were worn down and commonly stripped to the under-
lying rock.”

In “ Coal, Iron, and Oil, or the Practical American Miner,” etc., by
S. H. Daddow and Benjamin Bannan, published in 1866, a decidedly
original view of the origin of the iron ores and their associated rocks, as
well as of the placer gold of California, is given (pp. 532, 533, 546 — 550).
All are thought to have been formed by volcanic action. ‘‘ We are
aware that all our sedimentary rocks were formed in water, and that
the materials forming them are the results of volcanic action. The
logical sequence is, that those volcanoes either existed in water, or
vented their lava into it. Metals are always heavier than their matrix,
or the earthy strata in which they are found; thus, if the lava con-

MUSEUM OF COMPARATIVE ZOOLOGY. 17

tained a large amount of metal, it would be the first to be precipitated
to the bottom of the water into which the lava was vented. The lava
would not run in a solid stream from the crater, and solidify as a stratum
in the water, but the moment it touched the adverse element it would
be shivered to atoms, and thrown back into the atmosphere with the
steam it would create, and the lighter portions would naturally arise in
dust and ashes, and be carried by winds and waves and tides to remote
localities, while the heavier materials would be precipitated in the
vicinity in the order of their density. .... We may refer most of our
great Azoic beds of magnetic and specular ores and red oxides of iron to
this cause, and their formation to these agencies. We may also refer
the alluvial or drift gold in the ‘ placers’ of California and the ‘diggings’
of Australia to the same causes.” (/. ¢., p. 533.)

It is such theories as this, and many others touched upon in this
paper, that give the “funny side” to our work, and serve to enliven
the tedium of it; otherwise they would not be worthy of preservation.
They stand as the caricatures of science, although they were evidently
sober realities to their authors.

A series of papers was published by Dr. Hermann Credner in 1868 —
70, the titles of which will be given in the literature at the end of this
work. He divides the formations as follows: the gneiss-granite, or
Laurentian formation, and the limestone-quartzite-iron-stone, or Huro-
nian formation. The latter is said to unconformably overlie the former,
but the evidence, so far as given, is derived from the dip and strike of
the Jamination, and not from observation of the kind and manner of
their contact. The diorites, iron ores, and all their associated rocks,
except a few, are regarded as interbedded formations. The iron ore is
supposed to have all originally been magnetite, and in part changed
since to hematite and limonite. Near Marquette certain diorites were
seen by him to be eruptive ; therefore they were taken to be of differ-
ent age from the interbedded diorites associated with the iron ore, and
younger than the Huronian.

In Prof. A. Winchell’s Report of Progress of the Geological Survey
for 1870 we find the following remark : ‘‘ The rich masses of magnetic
and hematitic ores of iron are found not to be those erupted outbursts
which the older geologists were inclined to regard them. They are
simply constituents of the system of sedimentary deposits which make
up the Huronian System of Michigan. The diorites of the region appear
to be equally of sedimentary origin, and are found strictly interstratified
with chloritic, siliceous, talcose, argillaceous, micaceous, and hematitic

VOL. VII. — No. 1 2

18 BULLETIN OF THE

schists, in the foldings and convolutions to which these masses of ancient
strata have been subjected.” (7. ¢., pp. 26, 27.)

In 1873 the Report of Major T. B. Brooks on the Iron districts of
Michigan was published, with various accompanying documents by
Messrs. Julien, Wright, Houghton, Lawton, and others.* Mr. Brooks .
refers the date of the discovery of the iron ore to 1844, by Mr. Wil-
liam A. Burt and party, but the first official documents giving an
account of the ore seem to have been the reports of Burt and Hubbard
for 1845,} referred to in the early portion of this paper. Besides the
sandstone, the formations of this district are divided by Mr. Brooks as
follows: “‘ The Iron-bearing Rocks, corresponding, it is assumed, with the
Huronian system of Canada, consist of a series of extensively folded beds
of diorite, quartzite, chloritic schists, clay, and mica slates, and graphi-
tic shales, among which are intercalated extensive beds of several varie-
ties of iron ore... . . Lhe Granitic Rocks, which so far have produced
no useful minerals, and which are believed to be the equivalents of the
Laurentian of Canada.” (/. ¢., p. 66.)

As we shall have largely to deal with Mr. Brooks’s work hereafter, we
shall quote quite fully from it. “ Useful minerals which occur in beds,
like the iron ores of Lake Superior, will usually be overlaid and under-
laid by rocks having different characters, and which maintain those
characters for considerable distances. Next to finding the ore itself, it
is desirable to find the hanging or footwall rock. - Whoever identities
the upper quartzite in the Marquette region, or the upper marble in the
Menominee region, has a sure key to the discovery of any ore that may
exist in the vicinity. With few exceptions, all the rocks in the region
we are describing are stratified, — that is, arranged in more or less regu-
lar beds or layers, which are sometimes horizontal, but usually highly
inclined. This stratification, or bedding, is generally indicated by a
difference in color of the several layers, oftentimes by a difference in
the material itself, but occasionally the only difference is in the texture
or size and arrangement of the minerals making up the rock... .. In
general, a striped rock, whether the stripes be broad or narrow, plain or
obscure, on fresh fracture or weathered surface, is a stratified rock.”

We would invite Mr. Brooks to inspect the volcanic rhyolites, many
of the felsités that are known to be eruptive, as well as many of the
furnace slags to be seen in the Marquette district.. “Sometimes the
power which produced the folds seemed greater than the rocks could

* Geological Survey of Michigan, I. 1-319; II. 298 pp.
t I. 13, 14; II. 235-238.

MUSEUM OF COMPARATIVE ZOOLOGY. 19

bear, and cracks or breaks, and faults or throws, are the result, though
these are not numerous in the Lake Superior region. Cracks so pro-
duced, and filled with material other than that constituting the adjacent
rocks, are called dykes ; or, if the material be crystalline and metallif-
erous, vecns. -As iron ore in workable quantities does not occur in this
form in this region, vein phenomena will not be considered here.” Of
the Huronian series “the prevailing rock is a greenstone, or diorite, in
which, like the copper traps, the bedding is usually obscure ; but the
intercalated schists and slates, which usually bear strong marks of strati-
fication, make it usually not difficult to determine the dip of the beds
at avy point... . Descending to the oldest or bottom rocks of the
Lake Superior country, the granites and associated beds (Laurentian),
we find the bedding indications still more obscure, and often entirely
wanting.” (/. ¢, pp. 74, 75, 76.)

“Tn subdividing the Huronian or iron-bearing series which we have
particularly to study, the rocks have been grouped (1) lithologically, 2. €.,
according to their mineral composition, and (2) stratigraphically, t. ¢., ac-
cording to relative age. As this system was first described and named
by the Canadian geologists, their names have been employed as far as pos-
sible in the body of this report ; the identity in composition of many of
our rocks with theirs, having been established by an examination of a large
number of Marquette specimens by Dr. T. Sterry Hunt.” (/. ¢., p. 82.)
“The several beds or layers of the Huronian system, as developed in the
Marquette region, are numbered upwards from I. to XIX... .. Pre;
IIL, IV., are composed of beds of siliceous ferruginous schist, alternating
with chloritic schists and diorites, the relations of which have not been
fully made out; V. is a quartzite, sometimes containing marble and
beds of argillite and novaculite; VI., VIII. and X. are siliceous fer-
ruginous schists; VII., IX. and XI. are dioritic rocks, varying much
in character ; XIII. is the bed which contains all the rich specular and
magnetic ore, associated with mixed ore and magnesian schist ; XIV. is
a quartzite, often conglomeritic ; XV. is argillite or clay slate ; XVI. is
uncertain, it contains some soft hematite ; XVII. is anthophyllitic schist,
containing iron and manganese; XVIII. is doubtful; XIX. is mica
schist,’ containing staurolite, andalusite, and garnets. This classifica-
tion, it will be borne in mind, applies only to the Marquette region.
.... These beds appear to be metamorphosed sedimentary strata, having
many folds or corrugations, thereby forming in the Marquette region an
irregular trough or basin. . . . . While some of the beds present litho-
logical characters so constant, that they can be identified wherever seen,

20 BULLETIN OF THE

others undergo great changes. Marble passes into quartzite, which in
turn graduates into novaculite; diorites, almost porphyritic, are the
equivalents of soft magnesian schists.” (J. ¢., pp. 83, 84.)

are thought to result, perhaps, from the decom-
position of a ‘ limonitic siliceous schist,” with which they are associated.

The “soft hematites ”

“Tt is not at all improbable that this change may have been brought
about by the alkaline waters of former thermal springs.” (¢. ¢., pp.
90, 91.)

The “diorites” are said to graduate from a heavy, tough, black
variety into a soft, light-colored rock, resembling chiloritic schist more
than anything else, and called by him dioritic schist. ‘The bed-
ding of these rocks is generally obscure, and in the granular varieties
entirely wanting. It is usually only after a full study of the rock in
mass, and after its relations with the under and overlaying beds are
fully made out, that one becomes convinced, whatever its origin, it
presents in mass precisely the same phenomenon, as regards stratifica-
tion, as do the accompanying schists and quartzites. . . . . No reference
is here made to the false stratification or joints, which are numerous and
interesting, but which unfortunately, for want of space, can receive no
other attention here than to warn the observer against mistaking joint
planes for bedding planes, which is sometimos done, even by experienced
observers.” (/. ¢c., pp. 102, 103.) He also states that in no case has he
abserved a Huronian diorite in the Marquette district that does not con-
form “with the schistose and slaty strata with which they are associ-
ated.” (i..¢.,.p: 156.)

The rocks associated with the hard ores and ‘diorites” are called
“magnesian schists (mostly chloritic).” He says regarding them: “ It
would be difficult for a skilled lithologist, and impossible for me, to draw
the line between the chloritic schists here considered and the dioritic
schists.” Regarding the chloritic schist at one locality associated with
“specular slate ore,” it is stated: “ Prof. Pumpelly has suggested that one
may be a pseudomorph after the other. In this connection it may be
remarked that no gradual transition of one into the other was observed,
the division planes being in each instance sharply defined.” (/. ¢., pp.
104, 105.)

Regarding the connections of the ore in the Barnum mine with that
in the Lake Superior mine, he writes: “It shows that such formations
are not vein or dyke-line deposits, but true stratified beds, like the
rocks by which they are enclosed. Their structure is therefore essen-

tially the same as the coal, limestone, sandstone, and slate-beds, which

-

MUSEUM OF COMPARATIVE ZOOLOGY. 21

,

are regarded as sedimentary deposits from water, subsequently more or
less altered by heat, pressure, and chemical waters acting during im-
mense periods of time. The Lake Superior-Barnum deposit evidently
has a bottom, which will be reached within a period, of which it is worth
while for the present generation to take some heed. ... . The time
may come when, having worked out the steep, upturned edges of the
basins, and the flatter or deeper portions of the deposit are reached, ore
properties will be valued somewhat according to the number of acres
underlard by ore, as coal now is. Passing to the east portion of the Lake
Superior mine, I confess myself unable to give any intelligent hypothe-
sis of its structure. . . . . There seems to have been such a gathering
together, crumpling, squeezing, and breaking of the strata, as nearly to
obliterate the stratification... .. The remarkable features are the
great masses of light grayish-green chloritic schist, having a vertical
east and west cleavage, no discernible bedding planes, and holding small
lenticular masses of specular ore, which conform in their strike and dip
with this cleavage, and which seem to have no structural connection
with the main deposits. They appear like dykes of ore, squeezed out of
the parent mass, which we may suppose to have been in a comparatively
plastic state when the folding took place; or they may have been small
beds, contained originally in the chloritic schist, and brought to their
present form and position by the same causes, which produce the cleav-
age in the schist. . . . . The peculiar nature of the hanging wall of the
Lake Superior mine deserves further notice. Instead of the quartzite,
which we have hitherto found overlying all the deposits of rich ore, we
have here a magnesian schist very similar to, if not identical with, that
already mentioned as being associated with the ore.” (/. c., pp. 138 - 140.)

“All the Huronian rocks north, east, and south from the Jackson
mine are below, or older than the ore formation (XIII)., and all the
rocks to the westward and inside of the ore-basin are younger, hence
above it.” (/. c, p. 143.) “The iron-bearing or Huronian series of rocks
are stratified beds, the principal ore formation being overlaid by a
quartzite XIV., and underlaid by a diorite, or greenstone XI. This ore
formation is made up, first, of pure ore; second, of ‘mixed ore’ (7. e.
banded jasper and ore); and third, a soft, greenish schistose, or slaty
rock (magnesian), which occurs in lens-shaped beds which alternate with
ore, thus often dividing the formation into two or more beds of ore. sepa-
rated by rock. Usually the beds of both ore and rock thin out as they
are followed in the direction of the strike from a centre of maximum
thickness, producing irregular, lentiform masses. Since their original

‘

oF BULLETIN OF THE

deposition, if we may assume they were laid down under water, the
whole series, including the iron beds, have been bent, folded, and cor-
rugated into irregular troughs, basins, and domes, which often present
at the surface their upturned edges of pure ore, standing nearly
vertical.” (/. c, p. 245.) “The trouble is to find out when a pit is
exhausted, — it is so common to break through a thin layer of rock, and
find a bed of workable ore behind it.” (J. ¢., p. 262.)

The proof advanced by Mr. Brooks to show the unconformability of
the so-called Huronian to the so-called Laurentian, and the greater age
of the latter, is in substance this: the foliation of the latter was found
in two places to dip in a different direction from that of the lamination of
the “Huronian” schists near by (/. ¢., pp. 126, 156). His proof then
rests entirely on the hypothesis that these planes are the original bedding
planes of these rocks. This hypothesis again assumes that all are sedi-
mentary rocks,——a point still in doubt at the time of his writing, as
regarded one of the rocks at least. It is to be noticed that the two
formations were not seen in contact. He also remarks (/. ¢, p. 156):
“The non-conformability is further proven by the fact that the Lauren-
tian generally abounds in dikes of granite and diorite, which are almost
entirely absent from the Huronian.” Concerning certain rocks in the
Menominee district we find this acknowledgment: “It must be ad-
mitted, however, that the lithological affinities of this series of rocks
of the north belt are decidedly Laurentian, rather than Huronian. The
gneiss and granite outcrop above described, may be almost regarded as
a typical Laurentian rock in its appearance. If future investigations
prove them to be Laurentian, a very troublesome structural problem
would be presented here, as we would have Laurentian rocks conform-
ably overlying beds, unmistakably Huronian. There seem to be fewer
difficulties in supposing that the Huronian rocks of the Menominee
region embrace lithological families not, so far, found represented in
the equivalent series in the Marquette region.” (J. ¢., p. 175.)

Part ILL. of the above-mentioned work is devoted to the report of Dr.
C. Rominger. We take some extracts from this: ‘A locality on the
shore, two miles south of Marquette, where the sandstones in their con-
tact with the Huronian Quartzites can be seen, has been previously de-
scribed in Foster and Whitney’s report on the Lake Superior district.
We find here vertically erected white Quartzite beds of the Huronian
group projecting into the lake, which have preserved their granular sand-
stone structure, and are distinctly ripple-marked. They are surrounded
by brown sandstone aud conglomerate ledges, horizontally abutting

MUSEUM OF COMPARATIVE ZOOLOGY. 23

against them. The sandstones, which are of very irregular discordant
stratification, closely adapt themselves to all inequalities of the cliffs,
which exhibit under the sandstone covering a rounded water-worn sur-
face, indicating their long exposure before they were enveloped by the
sandstones.” (/. ¢., p. 90.)

Of Presque Isle he says: “This landspur is formed by a protrusion
of peculiar rock-masses, differing considerably from the rock-beds of
the Huronian group in the vicinity. Lowest is a black, unstratified,
semi-crystalline magnesian rock, resembling a half-decomposed basalt
or a highly ferruginous serpentine. It forms considerable cliffs at the
north end of the spur ;— more to the south we find it overlaid by a
more light-colored, once-stratified rock, which is involved in the up-
heaval, with its ledges bent and broken up in great confusion.” He
regards this as a dolomite. It is the same rock that Houghton consid-
ered to be sedimentary, and Foster and Whitney as a volcanic ash.
“On the south portion of Presque Isle this dolomite is inconformably
overlaid by a conglomerate and succeeding sandstone layers, which are
identical with the sandstones of the Marquette quarries. The sand-
stone strata some distance off from the protrusive rocks are nearly hori-
zontal.* In immediate contact with them they have a considerable dip,
corresponding to the convexity of the underlying surface. It is pos-
sible that the strata were slightly uplifted after their deposition, but
I am more inclined to explain the existing dip as an adaptation of the
sediments to the surface on which they were deposited. The conglom-
erate beds at the base are five feet thick, and contain numerous frag-
ments of the underlying dolomitic rock and of their enclosed Jaspery
minerals.” (/. ¢., pp. 90, 92.) He regards certain rocks at Light-house
Point and Picnic Island as intrusive diorites, giving evidence therefor,
and also remarks: “The Diorites interstratijied with the Huronian
schistose rocks in the environs of Marquette, and particularly at the
Light-house point, are of an evidently intrusive character.” (J. ¢., p.
93.) The italics are ours,as we are anxious to know how the same
rock can be interstratified and intrusive at the same point.

In a paper by Prof. J. S. Newberry, on “The Iron Resources of the
United States,” f we find the following statement: ‘On Lake Superior

* May we be pardoned for saying that, according to Messrs. Pumpelly and Brooks
(see quotations from them on the Copper district), this is proof positive that the Pots-
dam sandstones abut unconformably against the Presque-islian series, which must
then have formed an island in the Potsdam sea,

T International Review, 1875, I. 754-780.

24 BULLETIN OF THE

it is now easy to see that the ore-beds were once horizontal strata,
deposited in conformity with many other stratified sediments, but they
are folded and broken in such a way that their true nature was for
a long while misunderstood. Like the magnetic ores of the Alleghany
belt, they were once considered eruptive ; but the progress of modern
science has shown that all the so-called Eozoic iron ores are simply
metamorphosed strata, once deposited horizontally like the sheets of
iron ore now found in the unchanged Paleozoic rocks, —such as the
Clinton ore and the ‘black-band’ and ‘clay ironstone’ of the Coal
Measures.”

Col. Chas. Whittlesey,* in 1875, opposed the idea that the granitic
region was Laurentian, but regarded the rocks as eruptive. He accepted
the view of the Huronian age of the schists, however.

In the Transactions of the Wisconsin Academy of Sciences, Arts, and
Letters,t Mr. E. T. Sweet calls attention to the unconformability of the
Laurentian and Huronian with one another at Penokie Gap, Wisconsin.
It will be seen, however, by reference to the paper, that the absolute
contact was not observed.

In 1875 Mr. Brooks again took up the question of the granites in the
Menomonee district, which, according to him,t overlie the iron-bearing
rocks of that region. In order to solve the difficulty he assumes that
they are the youngest Huronian rocks (Formation XX.), and immedi-
ately underlie the copper-bearing series.§

The only reason, so far as we can learn from his paper and the original
observation quoted by us (ante, page 22), for this supposition is, that,
while they are lithologically identical with the “ Laurentian” rocks, he
can dispose of them best by placing them as the youngest of the Huro-
nian rocks. Furthermore, unless he did this, the ‘‘ Laurentian” would
be younger than the “ Huronian ” at this point, a conclusion that would
vitiate his former statements. He therefore deliberately violates the
lithological laws on which his work rests, and makes it simply a ques-
tion of where each rock will fit into his system the best.

From Dr. T. Sterry Hynt’s “ Azoic Rocks,” || we learn that from hand
specimens sent him by Mr. Brooks he established the presence of the
Montalban series, as well as the Laurentian and Huronian (/. ¢., p.

* Proc. Am. Assoc. Adv. Sci., 1875, XXIV. 60-72.
T Vol. III., 1875-76, pp. 40-55.

t+ Mich. Geol. Survey, J. 175.

§ Am. Jour. Sci., 1876, (3,) XI. 206-211.

| Sec. Geol. Survey of Penn. E. Part I.

MUSEUM OF COMPARATIVE ZOOLOGY. 25

223). The greenstones of the Huronian were also said to be indigenous,
i. e. rocks formed zz situ from sediments (/. ¢., p. 221).

We next come to the report of Mr. Charles E. Wright,* in which we
are informed that all the granites of the Upper Peninsula and Wisconsin
that have been examined by the writer are metamorphic. This view is
based upon microscopic characters, and we should object, zm toto, to the
premise. He also states: “Some objections were made last summer
(1876) by Dr. Rominger as to the non-conformability of our so-called
Laurentian and Huronian series, on the ground that he had observed in
several instances ‘a perfect conformability of these supposed distinct
series.’ It seems perfectly natural to me that this should often occur ;
and were I to find ninety-nine places where an apparent conformability
existed, and only one of decided non-conformability, the latter would, in
my estimation, outweigh all the former.” (/.¢, p.11.) He states that
a perfect case of nonconformability exists at ‘‘ Penoka Gap,” Wisconsin,
to which we have before referred; but if we remember correctly Mr.
Wright’s personal statement to us, neither was the junction seen nor
the kind of junction known that the two made with each other. It is
too fast to assume, as has been done by Messrs. Brooks, Irving, and
Wright, that the strike and dip of a foliated rock is the strike and dip
of its stratification. This is especially the case when the view that they
were ever stratified is still a disputed point.

Of the Huronian series the quartzite is said to show frequent ripple-
marks. The soft hematite is thought to have been formed as follows:
“In these mines it appears that the finely divided silica has been more
or less dissolved out by alkaline thermal water, leaving the iron oxide
and other bases behind.” (/.¢, p. 15.) The iron ore is regarded as
sedimentary, and Brooks’s geological ideas are closely followed.

He sustains Mr. Brooks’s division of the granites into Laurentian and
Huronian (Formation XX.), by the statement that he finds salt cubes
in the fluidal cavities of the latter, but not in the former.

Lastly, we have Mr. W. O. Crosby’s paper, ‘On a Possible Origin of
Petrosiliceous Rocks,”t in which he thinks it probable that the jasper
_and its associated iron ores are the representatives of a deep-sea deposit,
like the “red clay ” discovered by the Challenger expedition, below the
depth of 2500 fathoms.

It may not be amiss to incidentally refer to the treatise of Mr.

* First Annual Report of the Commissioner of Mineral Statistics for the State of
Michigan, 1879.
+ Proc. Bost. Soc. Nat. Hist., 1879, XX. 160-169,

26 BULLETIN OF THE

D. C. Davies on Metalliferons Minerals and Mining.* It would be
dificult to imagine a description or a section so at variance with
the facts as the ones that he gives on pages 274 and 275. We
feel that all geologists who have been in this region will be sur-
prised to be informed that ‘“lingulz are abundant in the overlying
sandstone.” On page 149 he has represented the copper-bearing rocks
and sandstone (Potsdam) as resting directly upon, and at a steep angle
dipping away in both directions from, the iron-bearing rocks ; also, the
western copper rocks as dipping east, and resting upon a similar set of
iron rocks. It is to be hoped that the rest of his book is not so errone-
ous as this.

Historical Summary.

In general, then, in looking over the views advocated by past ob-
servers, we find, in brief, the following opinions held.

The rockst of this district were all taken as azoic by Foster and
Whitney, and not considered to be capable of subdivision into geologi-
cal periods. We must also notice that Prof. H. D. Rogers regarded
them as of primal or Potsdam age. On the other hand, we find that
this formation is divided by Murray, Hunt, Kimball, Winchell, Creduer,
Brooks, and Wright into the Huronian and Laurentian. This division
is based upon lithological characters, and an unconformability said to
exist between the two. Rivot considered the whole as Potsdam.

The granite is regarded as an eruptive rock by Foster and Whitney,
Bigsby, and Whittlesey ; and as of sedimentary origin by Rivot, Kimball,
Brooks, Hunt, and Wright. These latter, with Credner, take it as being
older than the schistose rocks associated with the iron ores, and, except-
ing Rivot, with its accompanying gneissoid rocks composing the Lauren-
tian formation. Foster and Whitney and 8. W. Hill regarded the gran-
ite as younger than, and eruptive in, the schists. ~ :

The gneisses and schists were taken by all the observers as being of
sedimentary origin, except possibly Whittlesey, whose language is as
obscure as the formations about which he writes.

The metamorphism of the schists is supposed by Hubbard, Rivot,
Kimball, Hunt, Brooks, and Wright to be occasioned by chemical agen-
cies accompanied, as part thought, by galvanism. Foster and Whitney
and Bigsby considered that the metamorphism was brought about by

* London : Crosby, Lockwood, & Co., 1880.

+ Excepting the sandstone, which will be spoken of in our remarks on the Copper
district.

MUSEUM OF COMPARATIVE ZOOLOGY. 27

the presence of eruptive rocks, and their accompanying chemical agencies.
Foster and Whitney regarded the “diorites” of this region as eruptive
rocks, but Rivot, Kimball, Hunt, Winchell, Credner, Brooks, and Wright,
as sedimentary ones and interstratified with the schists.

The iron ores are regarded as all of sedimentary origin by Foster,
Kimball, Dana, Hunt, Winchell, Credner, Brooks, Newberry, and Wright,
but are believed for the most part to be of eruptive origin by Whitney,
and by Foster and Whitney. These ores were said to be in the upper
portion of the Huronian series by Kimball, Brooks, and Wright, with the
“diorites” underlying them. _

It will thus be seen that, while Foster and Whitney regarded certain
of the rocks in the “ Huronian” as eruptive, Hubbard, Rivot, Kimball,
Hunt, Credner, Brooks, and Wright regarded all, with a few slight excep-
tions, as sedimentary ; and Houghton, Hubbard, Locke, Kimball, Rivot,
and Brooks teach that they pass by gradual transition into one another.

The most important points, then, about which there has been or is
difference of opinion, are the age and relation of the granite and schists,
the origin of the diorites and iron ores, the passage of one rock into
another, and the presence or absence of eruptive rocks. These and other
questions relating to this district admit in many cases of no middle
ground ; one or the other party must be mistaken in their observations
or conclusions, or both. All these questions lie closely to the fundamen-
tal propositions of geology; they reach to the superstructure of the
science.

Methods of Observation.

The object of the writer in visiting the Iron district was to clear up
- some of the preceding mooted points in the geology of that region, if
possible, especially the origin of the iron ores and their relations to the
country rock.

From our personal experience in both regions, we should hold that
the ordinary methods of geological research which are employed in the
study of the comparatively undisturbed and unaltered sedimentary
rocks of the Mississippi Valley are not sufficiently accurate for our pur-
pose in the Lake Superior district, where the rocks are foliated, dis-
turbed, and of mixed eruptive and sedimentary origin. Stratigraphical
laws that hold good in the former region do not in the latter, especially
when it is sought to connect together two rocks of unlike character, or
when the nature and origin of either or both is a point of dispute. In
this disturbed district the presence of a rock in one place will hardly

28 BULLETIN OF THE

prove the presence of the same one in another, except by direct connec-
tion, even if the two do look alike, especially if that sameness is ques-
tioned. If the two rocks are identical in structure and composition,
nothing but the proof of direct, absolute continuity places the question
of their identity beyond dispute here, especially if we have any reason
to suspect the eruptive origin of one or both of them. Lamination,
banding, joint planes, cleavage, pseudo-stratification, and fluidal struc-
ture, are not to be taken as proof of stratification in doubtful rocks.
The very origin and nature of all, except, perhaps, the true fluidal
(not pseudo-fluidal) structure, are yet open questions. Until it is
proved that they are confined to one class of rocks, it is unsafe to use
them to prove that any questionable rock belongs to that class. Doubly
so is it when it is well known that they are not so confined. If they
are not to be used to determine the sedimentary origin of a rock, in like
manner the dip and strike of such structures ought not to be taken to
prove order of superposition, conformability, or non-conformability,
especially as this proceeds upon the supposition that both rocks in
question are sedimentary. That a sedimentary rock is horizontal, or
has a certain dip at one place, is not to be taken as proof of what its
position must be in another locality, unless the conditions remain the
same,

It may be said that every rock carries in itself, or in its relations to
its associates, or both, its history, more or less complete. In order
to read and understand this history, it seems necessary that we should
be able to distinguish between the fragmental and non-fragmental
forms; the characters assumed by a lava flow and its associated
detritus, their relations to one another and to the over and underlying
rocks; the characters of an intrusive rock, its effect upon the country
rock, and the nature and kind of junction that they make with each
other ; the relations that sedimentary rocks have to their over- and
under-lying rocks ; and the alterations to which all classes are subjected.
One of the most common errors made, is by observers taking the ground
that two outcropping rocks that look alike are of necessity the same
geologically, and form a continuous whole, although no direct connection
is proved.

It now remains for us to enter upon the questions before us.

The Jasper and Iron Ore.

The country rock is of a varying nature, but is mainly composed of
schists (largely chloritic), argillites, and quartzite, in that part of the

MUSEUM OF COMPARATIVE ZOOLOGY. 29

district visited by us. Associated with these rocks is the jasper, which
is acknowledged on every hand to be an inseparable part of the iron ore
formation. The origin of one gives the origin of the other. Their
interdependence is such, and has been so regarded, that the relations
of one to the country rock give the relations of the other. The two
have been so fully described in the past, that it is only necessary to
briefly describe them here.

The common form is that of interlaminations of jasper and iron ore,
the laminze varying from extreme tenuity to considerable thickness. In
some places the jasper predominates, in others the ore. In the last case
we have a more or less valuable ore, according to the amount of the sili-
ceous material, which, however, may exist only in a mere trace. The
purer parts form large masses, that are mined, and which graduate into
the jasper, or ore containing so much jasper as to be unfit for working.
The workable parts are frequently lenticular in form, although often
irregular. The irregularity of the ore mass, its passage into the jaspery
ores, and the uncertainty where the next mass will be found, are among
the chief difficulties of the miner. The origin of the jasper and ore
becomes then a problem of great economic importance, as do also the
relations of both to the country rocks. The permanence and extent of
the formation, whether it is in the form of vein deposits, eruptive (intru-
sive or overflow) masses, or sedimentary deposits, are questions in which
the capitalist and miner, whether they will or not, are most deeply
interested. As they have never been regarded as vein deposits, there
remains for us only the question whether the jasper and its associated
ores are eruptive or sedimentary in origin.

Lest there be some misunderstanding as to to the reason for thus dis-
missing the theory of the ores here being vein deposits, we would remark
that the question has been ably and fully discussed before in the works
of previous observers. Furthermore, while veins on a small scale are
occasionally seen, we were unable to find upon either the jasper or its
associated ore a single character belonging either to a vein or an infil-
tration deposit. It therefore seems unnecessary to discuss the vein or
infiltration theory here.

As both the eruptive and sedimentary origin of the jasper and the
ore have been advocated by some of the most eminent geologists in this
country, it is necessary that the question should be answered by the
facts, and not by any preconceived theory or idea. The question now is
what are the facts, and their most probable explanation. The first and
most important thing to be observed in deciding this is the relation of
the jaspery formation to its country rocks.

»

30 BULLETIN OF THE

This relation is well shown in and about the Lake Superior mine at
Ishpeming. On the north side of one of the abandoned pits just east of
the main workings, the junction of the jasper and ore with the chlorite
schist was observed and figured. (Fig. 1.) Specimens were also taken that
show the contact (143, 144, 145, 146, and 147).* The junction of the two
is very irregular, the banding of the jasper and ore following the irregular-
ities of this line, while the schist is indurated and its laminz bear no rela-
tion to the line of contact. Stringers of ore project into the schist, which
near the jasper is filled with octahedrons of magnetite. The schist loses
its green color generally, and becomes apparently an indurated argillite.
The contact and relations of the two rocks are not such as are seen when
one sedimentary rock is laid down upon another, but rather that observed
when one rock is intrusive through another; and in this case the intru-
sive one is the jasper and its associated ore. On the south side of the
same pit the jasper bows in and out in the schist, forming at one place
a projecting knob whose banding follows its contour. Lying against it
is a long arm of jasper, similarly banded, which ends in a rounded knob.
This is represented in plan (Fig. 2), and specimen No. 150 was taken
from the end of the latter projection. In the southwest corner of the
same pit a dike of very fair hematite ore (155) about one foot in
width breaks at an angle of 15° across the argillite (154) and schist,
whose lamination is vertical. (Fig. 3.) Wherever the unbroken con-
tact of the jasper and ore with the schist could be observed, that junc-
tion is seen to be an eruptive one, on the part of the former (156, 157,
and 158). At the School-house mine east of the Lake Superior mine,
the jasper forms a dike with a knob-like ending, the lamination (band-
ing) following the curvature of the sides. The contacts between the
ore and schist were well-marked eruptive ones (168, 169). Overlying
the ore was found on one side a ferruginous and quartzose breccia and
conglomerate composed principally of the ruins of the underlying ore and
jasper (166, 167). A similar but finer-grained rock, mostly a quartzite,
forms the hanging, or better the fallen wall of the New York mine.
This is composed, in like manner, chiefly of the débris of the underly-
ing ore and jasper. Mr. Brooks’s statement regarding the ‘ quartz-
ite” of the Marquette district (p. 18) is undoubtedly true of this rock,
that when he finds the “quartzite,” adjacent to it will be found all that
is left of the ore formation. This, however, is not what Mr. Brooks

* The numbers enclosed in marks of parenthesis refer to specimens collected by
the writer, and deposited in the Lithological Collection at the Museum of Com-
parative Zoology,

MUSEUM OF COMPARATIVE ZOOLOGY. 3 |

intended in his statement, as these detrital rocks apparently form but
a small portion of his “quartzites.” These of course mark old beaches
water-worn after the jasper and ore were ¢z situ, in nearly their present
condition, and, if the logic of the geologists of the Michigan and Wiscon-
sin surveys were carried out, these unconformable detrital formations
would mark a new geological age.

One difficulty found in mining the iron ore has arisen from the schist
being found in large masses, broad at the upper part of the mine, but
tapering out to thin wedge-shaped masses below, which are left without
support when the ore is removed. This renders one wall, and some-
times both, unsafe, no one foreseeing when the support to the treacher-
ous schist will be removed. This structure evidently is consonant with
the theory of the eruptive origin of the jasper and ore. They break
obliquely up through the schist, and send off branches, which, pursu-
ing the same general course, leave wedge-shaped masses between them
and the trunk. The ore when removed allows that which has been
supported by it to fall. This very cutting across the lamination, how-
ever slightly, would tend to let all severed masses slide out, even if
they were cut on one side only. Figure 4, taken from an actual
section in an old working at the southeastern end of the Cleveland
mine, Ishpeming, shows the phenomenon very well, and its cause. The
branches of ore are about two to three inches wide here, the main body
being about twelve inches in thickness, and the relations can be well
studied. In several places near this point the irregular wavy line of
contact between the schist and ore can be seen; and all bodies of this
‘or the jasper were found on close examination not to coincide with the
lamination, however much they may appear to do so.

At the upper portion of the Jackson mine, Negaunee, the jasper and
hematite were seen to cut across and obliquely up through the schists. A
vertical section as shown by the former mining done at this point is given
in Figure 5. The jasper also curves in a similar manner at right angles to
this nearly east and west section. While this (the figure, not the actual
occurrence) could be explained easily by sedimentation, it is fatal to the
view of conformable deposition. In pit No. 3 of this mine (Jackson)
the ore breaks irregularly through the schist, forming a brecciated-look-
ing mass, while in other cases it runs up into the schist ending in irreg-
ular knobs. Figures 6 and 7 show some of the occurrences observed
and figured from the pit walls: Figure 8 represents a section about
forty feet in height at the west end of No. 7 pit in the same mine. The
schist shows bending and dislocation as represented in the curve 6, ¢,

oe BULLETIN OF THE

which shows the direction and manner of the upthrust. The point a
is at such an elevation that we are not able to assert that it is part
of the same formation. It certainly looked the same, and the assist-
ant captain in charge of the pit stated that he knew they were the
same. The entire mass of jasper and ore represented here had been so
acted upon by secondary agencies that it had been mined as “soft hema-
tite.” In the same pit a beautiful brecciated jasper ogeurs in which the
hematite forms the cementing material (269, 270, 271, 272).

In pit No. 4 a wedge of ore and jasper was seen intruding between
and across the lamination of the schist. (Fig. 9.) In the “north pit”
the eruptive character of the ore is well shown; Figures 10, 11, and 12
showing sections exposed on the walls. Overlying the ore at a low angle
is a quartzite containing jasper and ore derived from its underlying ore
(277). At the Home mine in the Cascade range the ore was largely
a sandstone impregnated with hematite (257), strike N. 70° W. with
a northerly dip, which varies owing to the contortion of the strata
from 30° to 70°. Several dikes of jasper run through this sandstone,
in part conforming to the bending of the strata, and in part breaking
across the laminze (258, 259, 260, 261). Specimen 259 shows well the
contact between the two rocks, the jasper and sandstone, which contact
in a less degree is shown by the other specimens. One of these dikes
is represented by Figure 13, in which the width is exaggerated compared
with the length. There is no mistaking the intrusive character of the
jasper and its interlaminated ore here. It is of course almost unneces-
sary to state that this mine, having as its chief ore a ferruginous sand-
stone, was long since abandoned. The quartzite (metamorphosed sand-
stone) which forms the hanging wall of the Pittsburg and Lake Superior
mine, Cascade range, has been cut through by dikes and little stringers
of nearly pure hematite (262, 263, 264), which in its present position is
distinctly intrusive. While in general these little dikes follow approxi-
mately the bedding, they are seen not to exactly do this, but cut the
laminze obliquely through much of their course. This mine contains as
a secondary formation much specular iron (265). Near the bridge over
the Palmer mine the jasper shows well its eruptive character in its junc-
tion with the quartzite, while the banding is seen to be parallel to the
contact line. This jasper holds in it, and as part of itself, the hema-
tite mined here.

It is advocated by Messrs. Credner and Brooks that all the iron was
originally in the state of magnetic oxide, this view being sustained by
the crystals of martite found in various parts of the district.

MUSEUM OF COMPARATIVE ZOOLOGY. 33

It would seem that a microscopic examination of the banded jasper
and ore should give us some facts bearing upon the question. A sec-
tion was made of a finely-banded jasper (136), taken near the Lake
Superior mine. Under a lens this shows a fine contorted banding.
Microscopically this section is composed of a fine granular aggregate of
quartz and hematite, and a more coarsely crystallized portion made up
of octahedrons of magnetite or martite, and of quartz of secondary origin.
The quartz in the first part is largely filled with minute globules and
grains of ore, which also occurs in irregular masses and in octahedrons,
The quartz associated with the more coarsely crystallized portion is
water clear, and shows the usual fibrous granular polarization of second-
ary quartz. Wherever the iron is in a distinguishable crystalline form
it is in octahedrons. The color and streak of the iron in the hand
specimen are those of hematite, but the powder is found to be magnetic.
No. 153, from the same locality, has similar characters. The section
was taken from the most jaspery portion, and shows much of the fine
aggregation of quartz and hematite. The structure of the quartzose
portion is like the devitrification structure of the rhyolites and felsites.
The section has been repeatedly fissured, and the fissures filled in with
secondary deposits of quartz and octahedral crystals of iron. So far as
we have observed, the brecciated jasper and ore have had their fractures
filled in like manner. No. 271, from pit No. 7, Jackson mine, is of similar
character. The jaspery portion is finely banded, and shows an apparent
fluidal structure. We are inclined to regard the structure as fluidal,
but in a rock so deeply colored it is difficult to make satisfactory exam-
inations. This is the only section that shows anything like a well-
defined limit between the jasper and ore bands, under the microscope, as
pointed out by Dr. Wichmann.* The powder of the two last-described
specimens is feebly magnetic. No. 262 was from the Pittsburg and
Lake Superior mine, Cascade range. This shows the intrusion of the
iron ore through the quartzite (p. 32). The ore gives the hematite
streak, is feebly magnetic, and appears to be’in octahedrons. The
quartz is much fissured, showing the effect of heat, and contains micro-
lites and fluid and stone inclusions.

The octahedral form of the iron ore would sustain the view that it
was all originally magnetite. The difficulty lies in proving the crystals
to be primary, and not secondary forms, especially as they are largely
associated with secondary quartz, and also are abundant in the little
fissures (minute veins) traversing the jasper. Our microscopic examina-

* Geol. of Wisc., IIT. 615.
VOL. VII. — NO. 1. 3

34 BULLETIN OF THE

tion of rocks of various ages and characters goes to show that all rocks,
especially the older, have been subject to more or less alteration. This
alteration is accompanied by recrystallization, which often obliterates the
original characters. This change appears to be produced through the
medium of the percolating waters, and consists rather in a chemical
rearrangement of the constituents of the rock amongst themselves,
than in the deposition of any material brought in from extraneous
sources. The jasper and iron ores, as well as all other rocks examined
microscopically from this district, have suffered this alteration to a
greater or less extent ; therefore it is perhaps impossible at present to
be sure of the original state of the iron, or how many changes have
taken place.

Without objecting in any degree to the idea that the ore was origi-
nally magnetic, certain facts indicate that the present magnetic state
of the iron is in some places due to secondary causes ; i.e. the heat of
intrusive rocks erupted since the iron ore and jasper were in place.
While in general the Republic Mountain ore is hematite, exceptions
exist. On the northerly side of the hill a “ diorite” dike was seen (91,
92). It is found that the ore was so affected by the heat of this intru-
sive mass that it is magnetic adjacent to it (90), while a short distance
away it is the normal hematite. Numerous other localities were exam-
ined about the hill where these secondary intrusions occurred, with the
same result; the iron ore was magnetic adjacent to the dikes, but not
magnetic a short distance away. <As a general rule, the magnetite or
the hematite pseudomorphs after it (martite) are found near the “quartz-
ite” of Brooks in this mine. Those who examine the map of Republic
Mountain, prepared by him,* will observe on the northern side of his
“ quartzite,” a queer tongue of it projecting into the hematite. An ex-
amination of this tongue at different places shows the following facts.
It contains numerous rounded and irregular fragments of the iron ore
in it; these fragments oceur on both edges (93, 94, 96), while the cen-
tre of the mass is free from them (95). At this point it varies from a few
inches to two feet in width, and it is seen to break across the lamina-
tion, although nearly coinciding with it. At another part, shown near
the same pit, No. 8, this rock and its contact with the “jasper” and
ore were well marked. The “quartzite” (115, 118) is firmly welded to
the ore, and breaks across the laminz, cutting them, and sending
tongues into the mixed jasper and ore (116, 117,119). The june-
tion is an eruptive (intrusive) one, and not that belonging to the con-

* Atlas, Geol. of Mich., 1869-738, Plate VI.

MUSEUM OF COMPARATIVE ZOOLOGY. 35

tact of one sedimentary rock with another. The ore at the junction is
magnetic. The question whether this is an intrusive or sedimentary
rock has another side than the simple scientific one. It makes a great
difference in the mine whether this is a simple overlying metamorphosed
sandstone, as Mr. Brooks places it, or a later intrusion cutting the ore
below. This latter case opens up numerous questions that the practi-
cal man can only disregard to his cost, sooner or later, but which have
nothing to do with the present discussion.

As this rock seems to belong to the granites, it will be described
under them (p. 54). Should future research show that all of the
“ quartzite” of Republic is the same as the tongue is, it would have a
bearing on the proximity of the magnetite and martite to it.

In like manner, passing to other mines where secondary intrusions are
more abundant, the magnetite becomes a more prominent feature. It
seems, so far as we have seen, that the magnetite and martite are
directly proportioned to the amount and proximity of eruptive rocks,
extravasated since the ore was 7 situ.

East of the Old Washington mine, Humboldt, the actinolite schist
(310) and jasper with its ore (magnetite) were seen within one hun-
dred feet of one another, but dipping in opposite directions ; three hun-
dred feet farther west they both dip in the same direction, while a few
rods away the magnetite (311) with the jasper is seen breaking irregu-
larly through the schist (312), and sending tongues into it.

The intrusive nature of the ore was well marked here, but it was very
difficult to procure any hand specimens showing it (313, 314, 315, 316).
An attempt had been made to mine the ore at this locality. Three rods
to the east the ore and jasper were seen intruding in long tongues and
sheets between the planes of the schist, as well as breaking across the
lamination (317, 318). The same structure is very well marked in the
rocks that form the bluffs between the Old Washington and Edwards
mines. The ore with quartz (325) sends long tongues up between the
laminze of the actinolite schist (326). Although in part these coincide
with the bedding, yet in many places they break obliquely across it,
showing their intrusive character in an unmistakable manner.

It would seem that this intrusion between the planes (intrusive
sheets) in this locality probably took place when the schist was in a
somewhat unconsolidated condition, the intruded rock serving as an effi-
cient agent of metamorphism. The effect produced by the ore and its
relations to the schist are not such as we should expect, or are accus-
tomed to see, when a rock is intruded through one indurated as the schist

36 BULLETIN OF THE

is now. The ore at the New Washington mine is magnetite, and it was
seen in distinct well-marked dikes, as unmistakable as any dike, break-
ing obliquely up through and across the argillaceous schist, No. 340
showing the contact of the two. These dikes were sometimes narrow,
being only about one foot wide, with well-marked junctions with the
schist on both sides. The ore is more strongly magnetic and affected in
its character adjacent to the dikes that later cut through it than in
other portions of its mass (p. 43). The dikes of magnetite, with the
other dikes, have greatly affected the schist through which they pass,
forming an ottrelite schist (p. 45). At the Champion mine the ore
is both magnetite.(356) and hematite (355), and both are frequently
found in a single hand specimen (357, 358, 359). At the Keystone
mine, east of the Champion, a dike of magnetite about six inches in
width was observed.

The Basic intrusive Rocks, Schists, and Felsite.

At Marquette, south of, but near, the lighthouse, a dike (3) of about
seventeen feet in width cuts across the schist (1, 2, 5,), the latter dip-
ping north seventy degrees. The contact of the dike with the schist
is a well-marked intrusive one, the schist being indurated at the point
of contact (4). (Fig. 16.) Microscopically, the rock of this dike (3) is
composed of plagioclase, some orthoclase, quartz, hornblende, biotite,
viridite, magnetite, hematite, and some probable pseudomorphs after
olivine. The feldspar contains numerous microlites and inclusions, and
it appears to be the only original constituent of the rock left im a deter-
minable condition, except the magnetite. The schist (2) is composed
of a fine-grained groundmass of aggregately polarizing quartz, holding
greenish ragged hornblende crystals and grains of magnetite.

Many dikes occur in this vicinity, and their intrusive character has
been noticed by Credner, Rominger, and Julien. Some dikes (8) were
seen running north and south, cutting the east and west ones. The
relation of one of the latter to the adjacent schists is shown in Figure
14. In the quarries near the light-house numerous dikes were seen.
Their lines of junction with the schists (47) could readily be made
out, and hand specimens obtained showing it (45, 46, and 48). (Fig.
15.) Four of these dikes were counted within a distance of two hun-
dred and thirty-two feet, one of which was sixty-six feet in width (49).
The locality is the place from which the stone for the Marquette
breakwater was obtained. These dikes, like the majority running east
and west, nearly, but not quite, coincide with the bedding (45, 46, 47,

MUSEUM OF COMPARATIVE ZOOLOGY. 37

48, 49). A specimen of one of these (45), taken near the edge of the
dike, is composed of plagioclase, orthoclase, magnetite, titaniferous
iron, hornblende, viridite, quartz, epidote, and augite. The augite is
generally nearly altered to hornblende and viridite, only a little of
the distinguishable augite remaining in the centre of the crystals.
The other constituents, except part of the feldspar and the iron, bear
the characters of alteration products. A section adjacent to the
junction with the schist shows much higher alteration. The augite
has disappeared, the iron has been nearly all altered to “leucoxene,”
and secondary orthoclase is abundant. The schist from the same speci-
men (45) is composed of quartz, argillaceous material, chlorite, horn-
blende, magnetite, ‘‘leucoxene,” and a little augite. It would seem that
this has been formed from detrital material of the same nature as the
dikes (basaltic). The close resemblance of the “ diorite” and schist in
mineralogical characters, but not in structure, is shown in another sec-
tion containing the junction of the two rocks (48). No. 49, taken from
the centre of the dike, sixty-six feet wide, running parallel with and
belonging to the same system as the others, is composed of plagioclase,
augite, magnetite, olivine, and some viridite. Long microlites of apa-
tite traverse the mass in various places. The feldspar contains numer-
ous inclusions of the original base, more or less altered, of the same
general structure, relations, and arrangement as is commonly seen in
the feldspars of modern basalts. The portions of the base originally
left in the crystallization of the molten magma in the interstices between
the crystals has been changed to a grayish or brownish fibrous sub-
stance, also to viridite. The augite is comparatively fresh, and cut by
the feldspar crystals. The structure of the rock is that belonging to
the more coarsely crystalline basalts. The altered base is probably the
“inserted substance” of Drs. Zirkel and Wichmann.* It would seem
that some of the above rocks are like the “diorite” of Dr. Wichmann
from this locality (/. c., p. 629). We feel that the lithologist who wag
unacquainted with the field relations of the preceding specimens would
declare it impossible that they could be from the same series, apparently
identical in age, and originally so in composition. South of Marquette
the schists (11) are more argillaceous, forming true argillites, although
chloritic in places. Numerous dikes were seen here, but the rock is
more altered, and perhaps was extravasated earlier than most of the
dikes on Light-house point (9, 10, 12). No. 12 is composed of feld-
Spar, quartz, viridite, opacite, and pseudomorphous remains of horn-

* Geol. of Wisc., II]. 624.

38 BULLETIN OF THE

blende fragments. But little of the feldspar shows the twinning of
plagioclase. The structure of the rock renders it probable that it was
originally an andesite. On Light-house point, lying just north of the
dike (No. 3, page 36) first described, and older than it, is an intrusive
felsite (quartz porphyry). It is to be here noted that Mr. T. B. Brooks
states: “It may be confidently asserted that no porphyry occurs in the
Marquette . . . . Huronian” ;* also that this locality has been studied
by Messrs. Julien, Credner, Rominger, and others, without finding this
felsite.

This felsite is eruptive generally along the lamination planes of the
schist, but at certain points breaks throngh and across those planes.
Figure 16 gives a good idea of its relations to the schist and diabase,
for such we regard the rock of the dike to be. A short distance to the
north, on the opposite side of this immediate spit of land, its eruptive
character is better marked than in the first locality.

The felsite (6) on its weathered surface is colored pinkish and green-
‘ish white, showing fluidal structure, and holding crystals of quartz and
pinkish feldspar. On the fresh fracture the groundmass is felsitic, of
a greenish-gray color, and holds the same crystals. Pyrite is seen in
the fissures. The groundmass is now altered to an aggregate polariz-
ing mass, principally of quartz and mica. The fluidal structure is seen
in the thin section, and greenish and brownish mica is largely segregated
along the fluidal lines. The feldspar is entirely decomposed, having
about the same composition and structure as the groundmass, but hold-
ing more argillaceous material and less quartz. Chlorite and magnetite
were observed. The original quartz grains are filled with fluid and va-
por cavities, and also contain some stone cavities and microlites. North-
west of the light-house a more quartzose felsite (7) was found on the
side of a bluff overhanging a little ravine. This felsite is very much
jointed, breaking into small rhomboidal blocks, and cuts through the
schists nearly, but not quite, coincident with their lamination. . It is
a grayish-white rock containing crystals of feldspar, quartz, and pyrite.
Microscopically, the groundmass is now altered to a fine granular ag-
gregate, as in the preceding, holding quartz, muscovite, greenish mica,
aud pyrite. The feldspar is altered the same as the groundmass, and
contains similar minerals. The original quartz grains contain micro-
lites, stone inclusions, fluid cavities, etc. We regard these felsites,
from their structure, not as the equivalents or precursors of the Ter-
tiary rhyolites, but as identical with them, the present difference be-

* Geol. of Wisc., III. 660.

MUSEUM OF COMPARATIVE ZOOLOGY. 39

tween them being due to secondary alteration, and perhaps their some-
what greater depth at the time of consolidation than the part of modern
dikes reached by us had.

On Picnic Point, north of Marquette, a coarsely crystalline diorite
(50, 51, and 52) occurs, forming the main portion of the point. This
rock contains pebbles and fragments (53, 54) in some places. Some of
the fragments of schist are large, and one long band of it was seen.
This schist is much indurated, especially near its contact with the dio-
rite (58, 59), and forms an irregular junction with it (57). Picnic
Islands, just off the point, are composed, in the main, of the same
rock (60).

On the North Island, a diabase dike (61), about twenty-eight feet
wide, cuts the “ diorite,” running S. 80° E. Another dike was seen
running the same way, on the Middle Island. The “diorite” is some-
what brecciated. On Picnic Point a hornblendic granite (55) cuts up
through the diabase, and includes numerous fragments of it (56). The
general structure and relations of the granite to the “ diorite,” as well
as the rounding off of the “ diorite ” fragments, are shown in Figure 17.
The order is, then, Ist, the schists ; 2d, the ‘‘diorite” ; 3d, the granite
and diabase, — the question of the priority of either not having been
settled.

The “diorite” (50) is a grayish-black rock composed of hornblende
crystals, with reddish feldspar, epidote, and pyrite. Microscopically, it
contains the same minerals with magnetite and apatite, as well as chlo-
rite, quartz, viridite, and other alteration products. The feldspars are
greatly altered, give aggregate polarization, and are filled with altera-
tion products.

The most coarsely crystalline specimen (52) is a grayish-green rock,
composed mostly of short, thick hornblende crystals, showing well-
marked cleavage. With the hornblende a small amount of feldspar
occurs. Under the microscope, besides these, augite, chlorite, quartz,
titanite, hematite, actinolite, and magnetite were seen. The horn- °
blende and chlorite appear to be products of alteration from the augite,
and the hematite from the magnetite. Some of the feldspar can be
recognized as plagioclase, and it would seem that the rock was origi-
nally composed of feldspar, augite, and magnetite, while the other con-
stituents are alteration products. The quartz contains fluid and vapor
cavities.

The diabase dike rock (61) is a dark gray crystalline one, holding
ledge-formed feldspars and weathering brown. In the thin section it is

40 BULLETIN OF THE

seen to be composed of plagioclase, a little orthoclase, augite, olivine,
magnetite, hematite, viridite, and apatite. The feldspar encloses bits
of the original base, part of which is now devitrified, but part remains as
an unchanged globulitic base. This affords additional proof that the
diabases are simply old crystalline basalts. The augite is quite clear
and unaltered except in some places. The olivine is considerably
changed, yet the centre frequently shows the unchanged mineral.
These olivines, like those in modern basalts, are in fragments, grains,
and rounded and penetrated crystals, showing in this way their prior
origin to the crystallization of the rock in situ.

In the sketch of the literature given before, it is seen that Messrs.
Rivot, Kimball, Hunt, Winchell, Credner, Brooks, and Wright regard the
so-called ‘‘diorites” as sedimentary rocks, metamorphosed zz széw, and in
general teach that they gradually pass into the schists on either side ;
i.e. they form one and the same inseparable series of sedimentary
deposits. This passage, by insensible gradations, it is said, was estab-
lished by the field observations of all except Dr. T. Sterry Hunt, who, it
seems, based his conclusions upon lithological evidence ; for we fail to
find the slightest evidence in his writings that he had any personal
acquaintance with the district. On the other hand, Messrs. Foster and
Whitney taught that these rocks were intrusive, basing their conclusions
upon their observations in the field.

Special pains were taken by us in the field to see which of the two
views were correct. Where the conditions were such in the field that
any evidence could be obtained bearing on either side, that evidence was
always of the positive kind, and sustained Messrs. Foster and Whitney.
The evidence of the six observers quoted on the opposite side was of the
negative kind ; i. e. they could not or did not see any distinct junc-
tion between the two rocks ; therefore it was assumed that none existed.
Where the contacts were covered, or broken and obliterated by frost
and atmospheric agencies, the proof on either side is xz; but when
such is not the case, and we have on one side “ diorite” and on the other
schist, the question is, Do they or do they not pass into each other ?
Both rocks are of a greenish hue generally, and to the eye untrained
to observe the minutest changes and differences in rocks, they look
alike. It is therefore to be expected that the majority, at least, of ob-
servers will walk directly over the junction between two rocks, especially
if they believe in the prevailing theories, and declare that they pass
directly into each other by insensible gradations. The only thing such
negative evidence gives in this case is the proof that either the observer

MUSEUM OF COMPARATIVE ZOOLOGY. 41

was unskilled, or else his work was not done with sufficient care, per-
haps both. The line of contact is, when found, a distinct separation
between the two rocks; on one side of which is to be seen schist, on the
other “diorite.”. They no more pass into each other than do oil and
water in the same vessel, although it might not be impossible that some
would not be able to say where one ended and the other began. The
contact of the two rocks is so well marked that hand specimens (171,
172) can be obtained showing it; therefore our proof that they do not
pass into each other, but are entirely distinct formations, can be exam-
ined not only in the field, but also in the cabinet, and if need be under
the microscope.

Such a contact between the schist and “ diorite” can be seen a short
distance east of Ishpeming, where the carriage-road, near the railroad
leading to Negaunee, bends around a low “diorite” knob. This junc-
tion is represented in plan (Fig. 18) by a sketch made on the spot,
and shown by specimens 171,172. The “diorite” at this point appears
to have passed obliquely up through and over the schist. The relation
that the two have, the kind and manner of contact, are those belonging
to an eruptive rock breaking through and partially over another. It is
almost needless to say that the “diorite” is the eruptive rock here.
Many of the “diorite” hills, if not all, are composed of dikes of the
* diorite,” with schist and argillite lying between. The lamination of
these interlying masses is of course generally perpendicular to the pres-
sure, i. e. parallel with the dikes. This can be well seen in the hills
south of Teal Lake, Negaunee, as well as just northeast of the Cleve-
land mine, Ishpeming. At the latter place the “diorite” is seen to
break obliquely through the schist, and the line of junction can be easily
seen. (Fig. 19.) So far as can be told, the “diorite” comes out ob-
liquely over the schists connected with a narrower neck below, as shown
in ideal section. (Fig. 20.) This would indicate, we think, that this
is somewhat near the old surface of eruption. This hill was seen to be
made up of several “diorite” dikes, with schist held between them.
The contact of two of ther with the schist is shown in Figures 21, 22.

At Negaunee, on a little elevation between Main Street and the
Marquette, Houghton, and Ontonagon Railroad, the “ diorite” is seen
to break through the schist, and to send small veins into it. On the
“diorite” ridge south of Teal Lake, the “diorite” is seen (243+, 282,
283) to have cut through and enclosed between it some schists and
argillites. This rock is very columnar, and has the general character
of an eruptive mass. Its junction with the schists is well marked, and

42 BULLETIN OF THE

was observed in various places. One specimen is seen to be composed
of augite, hornblende, feldspar, viridite, titaniferous iron, and epidote
(243+). The augite is much altered, changed to viridite and hornblende.
Another section (283) shows no augite, this mineral being entirely re-
placed by the secondary hornblende. The feldspar is so greatly changed
that only part of it shows its triclinic character. Of a similar character
to No. 283 are Nos. 238+ and 239+, from the “diorite” south of Lake
Superior mine, neither showing any augite, although the hornblende is
doubtless secondary, as in the others. No. 239+ is more coarsely crys-
talline and granitoid in its structure.

The “diorite” (180) lying between the Lake Angeline and Salisbury
mines is seen in the thin section to be composed of plagioclase, horn-
blende, biotite, epidote, viridite, and titaniferous iron with its alteration
product. Of these only the feldspar and titaniferous iron are appar-
ently original constituents.

The diabase (175) forming the southeast side of the Salisbury mine
is a dark gray crystalline rock, holding ledge and tabular formed crystals
of feldspar, and weathering to a rusty brown. It makes a most beauti-
ful section under the microscope when studied in polarized light. It is
composed of plagioclase, orthoclase, augite, magnetite, olivine, viridite,
and hematite. The plagioclase cuts through the augite, leaving it in
cuneiform and irregular masses. The olivine is in rounded and irregu-
lar grains of prior origin to the crystallization of the rock, and is held
both in the feldspar and in the augite. It holds a similar relation here
to the feldspar that it does to the enstatite in the Presque Isle peridotite.
While the central portions of the olivine are sometimes clear and un-
changed, the grains are generally altered to a greenish or brownish ser-
pentine. A little fissure traverses the section, cutting and connecting a
number of the olivines. This fissure can be readily traced under the
microscope on account of its having been filled throughout its extent with
the greenish serpentinous material derived from the olivine. The feld-
spar is in some cases nearly filled with stone inclusions, arranged parallel
to the crystalline faces. These inclusions are evidently inclusions of a
devitrified base. This dike is said to ascend by steps, not in a straight
line. ; . *

Near Deer Lake, northwest of Ishpeming, a “ diorite” dike running
N. 45° W. (231) was seen entting a breccia and conglomerate (229,
230). This “diorite” is so altered that it resembles a chlorite schist,
and in the thin section is seen to be composed of chlorite, quartz, and
mica. It holds some ferruginous masses resembling the product of

MUSEUM OF COMPARATIVE ZOOLOGY. 43

the decomposition of titaniferous iron, as well as one or two that proba-
bly resulted from the decomposition of olivine or brown hornblende.
The quartz contains fluid inclusions. The groundmass is now composed
entirely of scales, plates, grains, and microlites belonging apparently to
chlorite, mica, and quartz, and with the exception of the ferruginous
decomposition product no trace of the original structure and constitu-
ents remain. We regard the rock simply as a more highly metamor-
phosed condition of the “diorites” of the region ; but were it not for
its field relations we should not be able to tell its history from micro-
scopic examination. In such a case as this, with our present knowl-
edge, the microscope fails to give us any idea of its origin, whether
eruptive or sedimentary. Probably every lithologist, in examining this
section, would pronounce the rock to be sedimentary, yet we know it
to be eruptive, and probably in its original state a basalt. This well
illustrates the danger of deciding upon the origin of such highly altered
rocks by microscopic analysis alone, and calls attention to the necessity
of carefully ascertaining their relations in the field.

One mile northwest of Deer Lake, west of the road, a high hill was seen
composed principally of “‘ diorite” (232) running about north and south.
The contact of this “diorite ” with the country rock is well marked on
both sides. On the west side it cuts a conglomerate, and on the east
a finer-grained fragmental rock (233). The contact is an irregular
eruptive one, and the country rock is indurated near it. At the south
pit of the Jackson mine, from which “soft hematite” is taken, a
diabase dike forty feet wide was observed running N. 30° W., and cut-
ting the ore. It was said that in mining its course had been found to
be variable. This diabase is a grayish brown, coarsely crystalline rock
composed of plagioclase, orthoclase, augite, brownish decomposed olivine,
magnetite, and ferrite (278). The plagioclase is but very little decom-
posed, and is beautifully striated. The diabase (280) near its walls was
very much decomposed, and its olivine, augite, and magnetite form a
dark brown decomposed mass cut through by the feldspar crystals, which
are kaolinized, forming feebly polarizing masses. Were it not known
that it is part of the diabase, it could only be recognized as such from
the position and arrangement of its kaolin pseudomorphs relative to
the remaining portion of the section.

In the Washington mine several dikes of “ diorite” and melaphyr cut
the ore, which is strongly magnetic in contact (327, 328) with them.
The melaphyr (329, 342) encloses a horse of jasper and cuts the “ dio-
rite.” It (329) is composed of plagioclase, a little orthoclase, augite,

44 BULLETIN OF THE

magnetite, and viridite. The structure is that belonging to basalts, and
the rock is comparatively little altered considering its age. The feld-
spars contain inclusions that appear to have been portions of the origi-
nal base, but which, as well as the base adjacent, has been altered to
a grayish-white globulitic and fibrous material. This shows largely
the structure of the original globulitic base, but wants the black color.
The fibrous alteration product of the base has been confounded with
the true original micro-felsitic base of the andesites by lithologists
generally ; as is the inevitable result of studying the constituents of
rocks without regard to the origin of these constituents. A very little
of the original globulitic base was found unchanged in some ‘of the
feldspars. Numerous microlites extend through the groundmass that
belong apparently to apatite. This is probably from the same dike that
No. 1110 of Mr. Brooks's collection, described by Dr. Wichmann, was
obtained.* The ‘long, small rod-like crystals” in which the plagioclase
is said to occur is the usual ledge form which belongs to basaltic plagio-
clase. The “inserted substance, which has not been individualized,” is
doubtless the altered globulitic base. No biotite or hematite were seen
in No. 329, which was selected with direct reference to procuring as
unaltered a specimen as possible, as well as one removed from the influ-
ence of the ore and jasper (342) through which the melaphyr cuts. <A
section showing the junction of the two rocks (342) was made. The
melaphyr here becomes a dense black opaque mass, containing a few ledge-
formed plagioclase crystals and some decomposed (viriditic) augite. This
part is probably an altered tachylitic glass, such as occurrs in similar
positions in basalts. The junction with the jasper is well marked, and
more regular than one would expect to find it. The globulitic structure
shows well in the melaphyr at this immediate line of contact. The
“jasper” is composed here of quartz and magnetite. The quartz is in
part fine granular, and filled with magnetic dust ; while the remainder
is coarsely granular, having the same structure as the granite (greisen)
southwest of Republic Mountain (No. 128, p. 53). These quartz grains
were formed by the fissuring of a quartz mass, not built up of detrital
quartz grains, as is the case with a true quartzite according to the defi-
nition employed by us. The quartz contained numerous fluid and stone
inclusions, as well as microlites, magnetite, and lenticular scales of proba-
ble muscovite. :

The “diorite” (334, 335) cutting the magnetite yielded specimens
showing a well-defined contact (337, 338, 339). No. 335 is a greenish-

* Geol. of Wisc., III. 625.

MUSEUM OF COMPARATIVE ZOOLOGY. 45

gray rock composed of hornblende, holding patches of quartz, which con-
tains crystals of tourmaline. The rock holds an abundance of magnetite,
in part at least torn from the ore through which it passed. The quartz
contains fluid and other inclusions. The schist at this locality is an
argillaceous one (340) resembling that found at Republic Mountain,
Ishpeming, and Negaunee ; but it has been so affected in places by the
combined action of the magnetite and other dikes that it has become an
ottrelite schist (336). This rock has a dark gray groundmass, holding
crystals of ottrelite and minute ones of tourmaline. In the thin section
the groundmass is of a clear grayish-white color, and holds ottrelite,
tourmaline, and magnetite. This groundmass is composed of a clear talc-
like mineral in flakes and scales, apparently orthorhombic. In it occur
magnetite grains and irregular masses of this mineral, as well as greenish
micaceous scales. The ottrelite in the section is of a green color, shows
dichroism, varying from a light to dark green, and contains scales of the
talc-like mineral, magnetite, ete. In polarized light it shows a banding
generally of lighter and darker shades of the same color. Its edges are
broken, step-like, and irregular ; and it shows cleavage parallel to the
basal and lateral planes. In microscopic characters it and the masonite
of Warwick, R. I., are closely alike. The tourmaline is in elongated
erystals containing grains of magnetite. All the minerals in this rock
are of later origin than the magnetite.

South of the Champion mine dikes of diabase (346) and “diorite”
(345) occur in the granite and gneiss. A “diorite” that was undis-
tinguishable from that in the gneiss (345) was found at the east end
of the Champion mine, in the “ Huronian.” This “ diorite” contains
patches of quartz, which hold crystals of tourmaline in radiated groups.
The “ diorite” (345), running north and south in the “ Laurentian,” cuts
both the granite and the gneiss, and is composed of hornblende, biotite,
quartz, and magnetite. Traces of some of the larger and more porphy-
ritic feldspar crystals remain in a kaolinized mass, containing flakes of
biotite and grains of quartz. Were the origin of this rock unknown, it
would pass for a sedimentary hornblende schist, so far as the section in-
forms us of its nature. The diabase (346) is comparatively fresh, and
is undistinguishable from the diabases seen in the “Huronian.” It is
composed of augite, plagioclase, a little orthoclase and quartz, mag-
netite, viridite, and some decomposed olivine.

Another dike (343), cutting the gneiss at this locality, is seen to be
composed of hornblende, quartz, feldspar, and magnetite.

On the northerly side of Republic Mountain a garnetiferous “ diorite ”

46 BULLETIN OF THE

(91, 92) was observed cutting across the iron-bearing rocks, bending and
breaking them at the junction between the two. The “ diorite” holds
fragments of the iron-bearing rocks in it, and cuts very irregularly
through the schists. Its intrusive character is distinctly marked by the
relation which it holds to the country rock. It renders the rock adja-
cent to it magnetic for a little distance from the junction. A section
taken from a specimen (92) free from garnets is seen now to be com-
posed almost, if not entirely, of secondary minerals, —a confused aggre-
gation of greenish hornblende, orthoclase, quartz, and biotite, with
traces of magnetic iron. The character of the hornblende is the same
as that seen to occur in those rocks whose hornblende is derived from
the augite by alteration.

To the southeast of this locality, not far from the granite, the iron-
bearing rocks were again found in contact with a similar garnetiferous
* dioritic ’ dike ; the former being much contorted and broken, the iron
being also magnetic near the contact. A tongue of the “diorite” pene-
trated the ferruginous rock, and the relations were such that it was
evident that the contortion was owing to the intrusion of the “dio-
rite.” The “diorite” (121) marked on Mr. Brooks’s map of Republic
Mountain, lying between the quartzite and Smith’s Bay, is seen under
the microscope to be very much altered, and composed of hornblende,
biotite, plagioclase, orthoclase, quartz, and magnetite, with a little hema-
tite. Of these minerals, it would seem from their structure and rela-
tions, that only the magnetite and part of the feldspar were original
constituents.

The basic intrusive rocks mentioned in the preceding pages have, in
general, been regarded as diorite, Mr. A. A. Julien especially doubting
the presence of any diabase in the region.* They would pass, according
to the ordinary definitions, macroscopically and microscopically, for dio-
rite, quartz diorite, diabase, chlorite schist, hornblende schist, etc., yet
we regard them ail simply as more or less altered forms, according to
age and conditions, of rocks that were originally the same in origin,
structure, composition, and name, — basalt. Of course, the supposed
altered andesite (p. 38) would be an exception. The reasons for so
regarding them have been briefly pointed out in this and preceding
papers.t Excepting the melaphyr of the New Washington mine, we re-
gard them all, then, as the alteration form of basalt known as diabase.

* Geol. of Mich., Il. 42, 193.
+ Proc. Boston Soc. Nat. Hist., XIX. 217-237, 309-316; Bull. Mus. Comp.
Zodlogy, Cambridge, V. 275 - 287.

MUSEUM OF COMPARATIVE ZOOLOGY. AT

At Republic Mountain, on the southwest side, a garnetiferous “diorite ”
was seen in direct contact with the jasper, which was much twisted and
contorted. The ore associated with the jasper was magnetic. The
“diorite” was found to be intrusive here and elsewhere about Republic
Mountain, breaking through and uplifting the overlying rock, whose
lamin it is seen to cut obliquely. It also sends stringers and dikes
into the schist and jasper. As the “ diorite” passed approximately along
the lamination of the schists, and is foliated parallel to its walls, it is easy
to see how those who believed that, if a rock was “striped,” it was prima
facie evidence that it was a sedimentary one, should overlook the eruptive
characters. Most of the ‘diorites” here contain garnets, this mineral
being found principally along the edges of the intrusion, while the cen-
tre was nearly, if not entirely, free from it. The schist, in like manner,
near the “ diorite,” also frequently contains garnets, both rocks appearing
to have mutually reacted upon each other. Under the microscope, one
of these “ diorites ” (124) is seen to be composed of actinolite, garnet,
quartz, and biotite. The arrangement, form, and relations of these indi-
cate that none of them are original constituents of the rock, but all are
the products of alteration.

A dike of dark micaceous “ diorite ” (123), some ten inches in width,
was seen near this place, which contained garnet crystals varying from
one half an inch to two inches in diameter, averaging about three
fourths of an inch. These garnets, like the others observed, are dode-
cahedrons. Microscopically it is seen to be composed of biotite, quartz,
feldspar, and magnetite (?) with the enclosed garnet crystals. The
black grains have the microscopic characters of magnetite, although the
powder is not magnetic. The biotite is the predominating mineral, and
all the present constituents, except, perhaps, the supposed magnetite,
appear to be secondary products. The garnet is filled with the magnet-
ite (?). These black inclusions, so far as we are aware, have been taken
for magnetite,* except some observed by Professor Pumpelly.t In po-
larized light the garnet is seen to contain abundantly the same grains ot
quartz and feldspar that the groundmass does ; it also holds some biotite.

The “ magnetic siliceous schist ” of Mr. Brooks (126) near the granite
(128, 129, 130) southwest of Republic Mountain (p. 53), is seen micro-
scopically to be composed of actinolite, hornblende, magnetite, and
garnet. The two first form the major portion of the section. The
garnet is filled with needles of actinolite. Southeast of Republic Moun-
tain, the same rock (No. 100, p. 53) contains longer and better formed

* Geology of Wisc., III. 608. ft Am. Jour. Sci., (3,) X. 20,

48 BULLETIN OF THE

erystals of actinolite. Besides actinolite, the chief constituent, it also
contains magnetite, garnet, and a little hematite. The garnet contains
inclusions of actinolite. The garnetiferous rock (97) adjacent to the
granite (p. 52) is composed of actinolite, quartz, garnet, and a little
secondary hematite.

Southeast of the Old Washington mine a dike was seen breaking
irregularly through the schists. Near the centre of the dike, the rock
(305) resembles a chlorite schist, but is composed of actinolite, mag-
netite, quartz, biotite, and muscovite, none of which appear to be
‘original constituents, except perhaps the magnetite. A specimen near
the exterior (306) was more massive, but contained the same min-
erals. Part of the iron showed the decomposition of titaniferous iron.
No. 307, from the edge of the dike, closely resembles a chlorite schist,
and contains garnets and well-formed crystals of tourmaline. No. 308
comes from the edge of the dike, and is so filled with garnets as to
resemble eklogite. Neither of the four specimens would macroscopi-
cally be taken as belonging to the same rock if their relation was not
known. This is probably the rock described by Dr. Wichmann as eklo-
gite.* The schist at the point of contact is much indurated and quartz-
ose, and the garnets make an irregular columnar mass adjacent to it
(309). They are so crowded and drawn out at right angles to the schist
that their structure very closely simulates the prismatic structure of a
basaltic dike. Such structure and arrangement of minerals, in a ring,
parallel to the surface of the enclosed fragment, is frequently seen about
quartz grains and other foreign materials included in the volcanic rocks
of the Cordilleras. Several other dikes of the same rock were seen
near this. All were very much contorted, breaking very irregularly
through the schist, and showing intrusive characters.

The actinolite schist south of Humboldt was seen to pass into a quartz-
ose rock made up principally of alternate layers of quartz and actinolite
(319, 320). This shows very conclusively the sedimentary origin of the
schist here. The banded magnetic schist of Mr. Brooks southeast ot
the Champion mine (No. 348, p. 57) is seen microscopically to be com-
posed of a thick mat of actinolite holding garnet, quartz, and magnetite.
The magnetite is surrounded in many cases by thin films of hematite,
derived from the magnetite, and extending between the actinolite crys-
tals. The same hematite films extend around the garnet and penetrate
along its fissures, giving it a deep red color, but leaving the centre often
clear. Only a little quartz was observed.

* No. 1091, Geol. of Wisc., III. 649.

MUSEUM OF COMPARATIVE ZOOLOGY, 49

These garnet-bearing, actinolite, intrusive rocks we cannot at present
definitely place in that position which seems to us proper. In order to
do that, it is necessary to have part at least of the original structure or
constituents preserved ; this we did not find. So far as we can judge,
they are probably altered basalts or andesites, most probably the former ;
this conclusion is, however, liable to be overthrown by new evidence
at any time. The reason for this decision is in the main their rela-
tion in minerals, position, and structure to the other highly altered
“ diorites,” especially at Republic Mountain. The actinolite schists
were in all probability formed from detritus of the same composition
as the dikes, and therefore under like conditions are mineralogically
about the same.

In the Lake Superior mine, a banded greenish quartz rock resembling
prase was observed. In the thin section it is seen to be composed of
quartz containing magnetite and innumerable little scales of greenish
mica. The green color is due to the latter. Some fluidal inclusions
were observed. The quartz shows the granular aggregate polarization
observed in connection with the devitrification or alteration quartz in
rhyolites and felsites. The relation of this rock to the ore and jasper
was that of an intruding, fracturing, uplifting mass, breaking across the
lamination but not reaching the surface. Above and adjacent to it in
the disturbed jasper and ore “soft hematite” was found. This rock, we
think, would make a very pretty object when polished.

The “ Soft Hematites.”

One of the best localities that we have seen to study the formation of
the “soft hematite” is at the Salisbury mine, Ishpeming, just south of
the Lake Angeline mine. A “diorite” hill lies between the two mines,
‘which, when erupted, we believe upheaved the jasper and hematite lying
on both sides of it. At the west end, on the north side of the hill, the
Lake Angeline mine is situated, and it is still an open question whether
the ore formation does or does not extend eastward along the flanks of
the hill. On the southern side, towards the northern end of the hill,
the Salisbury mine is located. This is a “soft hematite,” which is held
by Mr. Brooks to belong to a different formation, in general, from the
hematite. We regard it as the same formation as the jasper and its
associated ore, but which has been acted upon by thermal waters. All
the writers on the “soft hematites” of this district have regarded
them as formed from the decomposition of ferruginous schists by thermal

VOL. VII. — No. 1. 4

50 BULLETIN OF THE

waters, and on this point we are in accord. In general they regard them
as peculiar to certain formations making a bed or set of beds in the
stratigraphical series below the ore formation proper, while we regard
them simply as local modifications of the ore formation of the region
occurring under certain conditions; i. e. the conditions that led to the
shattering of the rock and gave the opportunity for the formation of
thermal springs. On one side of the Salisbury mine is the “ diorite,”
while on the other comes a strong dike of diabase (p. 42). The “dio-
rite” runs about east and west, while the strike of the diabase is about
N.50° E. The latter is seen to be the younger rock, and the marks of its
passage through the “diorite” hill can be seen a long distance off. The
relation of the two rocks is shown in the plan (Fig. 23), while the supposed
relation of the “ diorite” to the schist and ore is given in Figure 24.

The Salisbury mine is located in the acute angle a, formed by
the two intrusives, at the point where the fracturing, breaking, and
shattering of the prior or ore formation was greatest, and where hot
springs would then most likely occur. The general structure of this
region, the character of the ore and its associated kaolin, all confirm, in
our mind, this view. As the ore deposit formed under such conditions
is necessarily limited, it has become a matter of great importance to the
company working this mine to find a continuation of this ore, or a new
locality, before the old is completely worked out. The mining captain
informed me that.the State Geologist, Dr. Rominger, in conformity with
his views and those of Messrs. Brooks, Kimball, and others, that the
diorite, diabase, jasper, hematite, and limonite are distinct sedimentary
formations, advocated the sinking of pits at the points 6, c, d, where
the formation would, by its foldings, again be brought up, and give the
same ore. The point 6 is located at the obtuse angle of the junction
of the diabase and diorite, therefore we should not expect so much shat-
tering of the rock, nor so great likelihood of thermal springs. Soft
hematite” would be expected to occur to some extent, but with too
much of the undecomposed jaspery rock to make it profitable mining.
Such was found to be the case ; therefore the theory of Messrs. Romin-
ger, Brooks, and others failed here. If the Lake Angeline ore formation
extends east along the northerly side of the “diorite” hill, the most
likely place to find a deposit of “soft hematite,” if our views are cor-
rect, would be at the point h, in the acute angle formed by the dia-
base with the “diorite,” as it breaks through the latter. Unfortu-
nately this point is not on the property of the Salisbury mine, and it
slumbers in its primeval mud.

MUSEUM OF COMPARATIVE ZOOLOGY. 51

The McComber mine, Negaunee, is a mine of “soft hematite” ; this,
in connection with others lying along the same line, is near the “ dio-
rite.” Part of these mines, however, lie between two hills of the “ dio-
rite.” Two deposits occur on the McComber property, separated by a
dike of the ‘‘diorite.’ The ore here, like that in the Salisbury mine,
seems to occur only where the rocks have been shattered and acted upon
by water. The jasper has decomposed (244+), yielding a hydrous
silicate of alumina (Kaolin, Brush) (245+, 2464-), quartz, hydrous and
anhydrous oxide of iron, etc. The minerals associated with the ore are
evidently water deposits, —barite (253), rhodochrosite (249+, 250+,
251+, 252+), manganite (247+, 248+), etc. Figure 25 shows the forma-
tion of the ore under a jasper cap, the water working in by the means
of fissures on both sides.

The Pendill mine, worked for a similar ore, contains much botryoidal
limonite (254). In one part the ore was worked out upon the top and sides
of an oven-shaped mass, the ore following the curvature of the oven.
This is similar to a form observed in the Lake Superior mine, associated
likewise with limonite. In the Jackson mine “soft hematite” occurs in
places, and it is seen to be associated with and to pass directly into the
jasper and “ hard ore,” showing that they were originally the same. Water-
deposited quartz (vein-stone) was found in places in this “soft ore,” and
a specimen was taken for microscopic examination (276), for the pur-
pose of seeing whether it contained fluid cavities or not. It is found to
be full of inclusions, most of which contain bubbles. These bubbles
were, in the majority of cases, seen to exhibit motion of greater or less
rapidity. ‘Some were seen containing double inclusions, and vapor cavi-
ties were observed. All would indicate that the water by which the
quartz was deposited was at a higher temperature than the rock has
at present. This then would seem to confirm the views of all the
writers quoted, as well as of ourselves, that these ores are derived from
the decomposition of the ferruginous, siliceous rocks. That this is the
correct view of their origin it would seem Dr. Hunt denies.*

The various soft ores are partly true hematites and partly limonites,
mixed with more or less impurities, but of course, in general, have none
of the characters of an erdinary bog-iron ore.

Our theory, of course, depends upon-the relation of the “ diorites”
to the jasper and ore, which near Ishpeming and Negaunee is some-
what uncertain ; yet there is but little doubt that the “diorite” is the
later. The dip of the jasper increases as it approaches the “diorite,”

* Geol. of Wise., III. 660,

52 BULLETIN OF THE

sometimes standing nearly vertical. It was not observed in contact with
the “diorite,” but we feel that the constant uptilting of the jasper and
associated schists when near these intrusive rocks is good evidence that
the “diorite” eruption was later than that of the jasper. The uptilting
of the jasper was well seen on a hill north of the Jackson mine, where
it was found, standing nearly vertical, within one hundred feet of the
“ diorite.”

Granite, Gneiss, and Quartzite.

The relation of the granite and its associated foliated rocks to the
schists of the Iron district is a problem of great geological importance.
The diverse views have been given on preceding pages, and it is not
necessary to repeat them here. The first-mentioned rocks have been
accepted by the Canadian geologists (in part at least), as well as by
most American ones, as the direct equivalents of the Laurentian
formation of Canada, while the latter is in the same way accepted
as the equivalent of the Huronian. Without going into the question
of the expediency or right of establishing geological ages upon any
other basis than that of organic remains, it is a fair question of in-
quiry whether the “‘ Laurentian” of Lake Superior is older or younger
than the “ Huronian.” Whose observations were the nearest correct,
— those who claim that the granite is intrusive in the schists, or
those who hold that it unconformably underlies them? On one side
we have the statement of direct intrusive contact ; on the other, the
evidence afforded by the fact that the strike and dip of the foliation of
the two rocks are unlike, the two formations never having been seen
in contact. ;

It is now time to give the facts observed by us.

North of Republic, by the side of the railroad, a few rods from the
depot, the granite (82) (Laurentian of Brooks) shows its intrusive char-
acter by its containing fragments of schist (83) in it, and by its cutting
the main body of schist. These schists are micaceous, hornblendic, and
chloritic, with a nearly north and south strike, the foliation of the
granite coinciding with it. Northwest of the track, near the above-
mentioned locality, the inclusions in the granite are well marked, the
foliation of the granite striking S. 20° E. Southeast of Republic Moun-
tain, separated from the supposed ‘“ Huronian” by a narrow ravine,
the granite was observed in contact with a garnetiferous actinolite rock,
beautifully banded and contorted (No. 97, p. 48). While this appears to
us to be identical with the “‘Huronian” rocks, a few rods away, resembling

MUSEUM OF COMPARATIVE ZOOLOGY. 53

the actinolite schists of Wichmann (100, p. 47), Mr. Brooks believes* it
to be “ Laurentian,” for no reason that we can see except that it is associ-
ated with the granite. This rock has been tilted and contorted by the
granite which is found in contact with it. The line of junction and the
manner of contact show that the granite was the later rock and an erup-
tive one. The foliation of the granite is parallel to the plane of contact,
or at right angles to the pressure. It contains fragments of schist (98),
while some highly quartzose schists or quartzites (99) were seen within a
few feet of it. These rocks were apparently older than the granites, and
had been affected by them. On the southwest side of Republic Mountain
the granite was seen about one rod from the “ Huronian” schists. This
is probably the locality figured by Mr. Brooks,t but the foliation of both
appeared to us to be conformable in this way: the schists appeared to
have been partially uptilted by the granite, which seemed to have been
extravasated obliquely out from under them, very much as the perido-
tite was under the sandstone at Presque Isle. The foliation is parallel
to the plane of pressure, and at right angles to that pressure.

The granite near the edge is fine-grained, resembling a quartzite
(128), but a little distance away it is coarser and more granitoid (129).
Borne upon the face of the granite next to the schists is a plate of rock
about two inches thick (130). This is welded closely to the granite,
and has been uplifted and altered by it. Its constituents have been
drawn out in the direction of the supposed motion of the granite, and re-
semble in the field the altered garnetiferous “ diorite” (123) described on
page 47. The rock is micaceous, of a dark gray color, and contains elon-
gated brownish-gray masses resembling altered garnets. Microscopically
it is seen to be composed of biotite, muscovite, quartz, and the garnet(?)
masses. The last are now composed of a finely fibrous aggregately po-
larizing material holding quartz grains, magnetite, and apparently hex-
agonal or orthorhombic opaque disks. Their nature is unknown, but
they most probably belong to the margarophyllites.| Whether this
rock was originally the same as No. 123 cannot be told, although in
many respects it closely resembles it. Should it be, the granite there
is younger than the “ Huronian diorite.”

The granite (129) is seen in the thin section to be composed of quartz
with some green mica. Not the slightest trace of feldspar was found.
The quartz is broken up into grains, which exactly fit to one another
without any cementing material. The granular structure arises not

* Geol. of Wise., IIT. 661. ¢ Am. Jour. Sci., (8,) X. 20.
Geol. of Mich., I. 126:

54 j BULLETIN OF THE

from original water-worn grains, but from the fissuring of an originally
continuous siliceous mass. The quartz contains fluid cavities, micro-
lites, and little flakes of mica. No. 128, nearer the Huronian, at the
edge of the granite, is microscopically seen to be in finer quartz grains.
This rock also contains greenish mica, clusters of actinolite crystals, and
garnet grains. The quartz grains contained the same inclusions as
those in No. 129. Some magnetite was observed. The actinolite crys-
tals were often seen to extend through two or more of the adjacent
quartz grains, not having been broken by the process of fissuring the
quartz.

Specimen 130 consists of two parts, —the schist already described,
and the granite to which it is welded. This granite is here composed
of quartz, biotite, and grains of garnet. The quartz is in the same fis-
sured grains as that in Nos. 128 and 129, and contains microlites, minute
crystals of greenish mica, and fluid cavities. The majority of the fluid
inclusions lie in the secondary fissures, but part are in the solid quartz.
The biotite is seen to frequently extend from one quartz grain into an-
other without having been broken by the fissuring of the quartz. The
garnet contains actinolite crystals, and the same black grains that it
did in the adjacent schist (130). The biotite and garnet are evidently
derived from this schist, and are in fragments. This section, more
than either No. 128 or 129, shows the effect of the schist in adding
foreign ingredients to the granite, and also the action of the granite on
the schist by tearing off and dissolving portions of its material. Such
phenomena are the usual accompaniments of the mutual reaction of
two rocks when one is intruded through the other. The three sections
128, 129, and 130 well illustrate the differences that can be observed in
the same rock within a distance of a few feet.

It seems appropriate to describe with the granites last given the
“quartzite ” (page 34) of Mr. Brooks at Republic Mountain. The rock
(95, 115, 116, 117, 118, 119) is greenish gray, macroscopically containing
quartz, actinolite, and epidote. Under the microscope it (115, 118) is
seen to contain quartz, actinolite, hornblende, greenish mica, epidote,
magnetite, and hematite. The quartz is in similar grains to that in
Nos. 128 and 129, and contains numerous microlites and mica inclu-
sions, as well as fluid cavities. This rock, it would seem, belongs to the
granites adjacent to Republic Mountain, and is an offshoot from them.
In microscopic characters they are closely allied, but we only offer this
for what such characters are worth in such questions as these. One thing
we know. This (“quartzite”) granite is eruptive in its present place,

MUSEUM OF COMPARATIVE ZOOLOGY. 55

and if it is part of the same formation that the adjacent granites are,
then the latter are younger in their present position than the iron ore
of Republic Mountain.

The preceding rocks (128, 129, 130) naturally fall under the name of
gretsen, but as they seem simply to be the modified edge of the ‘“ Lau-
rentian” granite, we prefer to apply the name granite to them. The
practice of giving a different name to every little local modification in
rocks has been a constant source of confusion in lithology. This prac-
tice has perhaps never been carried to greater extent than it has been
in this district.*

South of Ishpeming, on the line of the Chicago and Northwestern
Railroad, a gray gneiss (192, 193) was seen dipping W. 33°, cut by the
common reddish granite (194), which sends veins through it. Figure 26
was taken here from the side of a little cliff (195). The gneiss, at the
points in which it is cut by the granite, is less schistose, and becomes
more granitoid in its structure. A few rods west, on the north side of
the railroad track, this granite is seen in contact (197) with and cutting
a quartzite that resembles the ordinary “ Huronian” quartzites. The
granite is here in large masses, but shows its intrusiye character when
in contact with the gneiss, quartzite, or schists. About one eighth of a
mile nearer Ishpeming the granite (202) was seen in contact (200) with
and contorting schists (201, 203). This shows its intrusive character on
both sides of the schist, the contact being well marked in many places.
On the same elevation a fine-grained granite (204) was seen to be intru-
sive in a dark green nodular schist, containing large irregular masses
of feldspar (205). These schists and granites are in the area mapped
as “ Huronian” by Mr. Brooks.

The granite breaking through the “ diorite” at Picnic Point has been
referred to (page 39). This appears to be the same as the reddish
granite that occurs at the mouth of Dead River (62, 63). The lamina-
tion of this latter granite strikes S. 80° E. The reddish granite of the
entire region appears to be lithologically the same. That breaking
through the “diorite” at Picnic Point (56) is seen to be, under the
microscope, a crystalline aggregate of feldspar, quartz, and hornblende,
with magnetite. The feldspar is in part clear orthoclase, but mostly a
pinkish decomposed one without definite polarization. This, according
to the present imperfect method of microscopic analysis, is presumably
orthoclase, but we believe it may or may not be so. This feldspar is
now composed of a fibrous decomposition product, kaolin (?), with ox-

* See Geol. of Mich., Vol. II.

56 BULLETIN OF THE

ide of iron and quartz. Contrary to the views of Dr. Wichmann and
Prof. Zirkel, we regard these as the products of decomposition of the
feldspar and its enclosed foreign materials, and not originally formed
products. Likewise we find the same alteration products in distinguish-
able plagioclase as well as in orthoclase.* The quartz occurring in the
feldspar appears to be a secondary -product, as also is part of that occur-
ring independently in the rock. Many minute microlites occur in the
decomposed portion of the feldspar as a secondary product. The quartz
contains fluid cavities and microlites. No salt cubes were seen in the
fluid inclusions. It will be remembered that Mr. Charles E. Wright
pointed out that what he supposed to be the younger ‘‘ Huronian” gran-
ite contained such cubes in the fluid inclusions, while the ‘ Laurentian ”
granite did not. Here we have an eruptive granite in a district mapped
as ‘ Huronian ” that so far reveals no salt cubes. Of course, the evidence
is negative ; in another section, or possibly in some overlooked portion
of this section, they might be found. So long as Mr. Wright has used
this as a means of diagnosis, we point to the results here simply for
what they are worth to those who rely upon microscopic analysis only.
The hornblende is of a green color, and is broken and torn. Consid-
erable magnetite, pyrite, and secondary hematite was seen. Some mi-
nute crystals and grains, supposed to be zircons, were also observed, as
well as secondary epidote. Titanite is quite abundant. The granitet
at the mouth of Dead River (62, 63) is seen microscopically to be simi-
lar to the one just described (56). Its feldspar is not so much decom-
posed, and the orthoclase and plagioclase are readily distinguishable,
the latter being quite abundant. The hornblende has been almost en-
tirely altered to chlorite and biotite (?). The quartz contains microlites
and fluid and vapor cavities. Some minute crystals of zircon were seen
‘in the feldspar as well as in the quartz. The decomposed feldspar is
almost filled with microlites. Epidote is abundant as a secondary pro-
duct. The rock also contains magnetite.

Specimen 82 (p. 52) is a pinkish-gray granite. Under the micro-
scope it is seen to be composed of orthoclase, plagioclase, quartz, biotite,
muscovite, and magnetite. The feldspar is fresher than in the preced-
ing granites, and contains numerous mica inclusions, mostly muscovite.
The quartz holds microlites and both glass and stone cavities. The
muscovite generally cuts through or is mortised into the biotite, the
same as the feldspar is in the augite of the diabases. The musco-

* Geol. of Wisc., IIT. 601.
+ Chloritic gneiss of Brooks. Geol. of Wisc., II]. 662.

MUSEUM OF COMPARATIVE ZOOLOGY, oT

vite is quite subordinate to the biotite, and the plagioclase to the
orthoclase. The red granite south of Ishpeming (No. 194, p. 55) is
composed of orthoclase, plagioclase, quartz, viridite, magnetite, and
hematite. The feldspar is somewhat altered, the plagioclase showing
the same microlites and hematite alteration products as the orthoclase.
Part of the feldspar shows very beautifully the polarization characters of
microcline. The original mica in the rock is now altered to a viriditic
material. The quartz contains inclusions of feldspar, biotite, microlites,
magnetite, and fluid, vapor, glass, and stone cavities. The gneiss, in which
this last granite is eruptive, is a dark gray foliated rock (192, 193) com-
posed of biotite, quartz, vrthoclase, plagioclase, magnetite, and a little
pyrite. The feldspar is much decomposed, and contains microlites,
as well as the lenticular, colorless folize, so common in the decomposed
feldspars in the granites of this region, which we suppose belong to mus-
covite. The quartz contains the same little disks, as well as fluid and
vapor cavities. Numerous microlites of apatite, as well as some grains
that may belong to zircon, occur in the rock. The characters of the
rock appear rather to be those of an eruptive than of a sedimentary one ;
but as its relations to anything older than itself were not determined,
nothing definite can be said upon this point. In a section made of an
intrusion of the granite through the gneiss (195), both show their re-
spective characters as given above.

One half-mile southwest of Humboldt the granite is intrusive in a
mica schist. The granite at this point is white, and not of the usual
pinkish color. Southeast of the Old Washington mine the pinkish gran-
ite (323) was found intrusive in a hornblendic gneiss. We have termed
these rocks granite because the foliation appears to be a fluidal struc-
ture parallel to the contact planes, and because they pass into regu-
larly non-foliated granites at a distance from their junction with the
schists.

Southeast of the Champion mine the granite (350, 351) is found in-
trusive in a schist (349, 352, 353, 354). The schist is indurated and
much changed where the intrusive tongues of granite enter it (347).
There can be no question that the granite is intrusive, and younger than
the schists. They have both been mapped by Mr. Brooks as “ Lauren-
tian.” Four hundred feet east occur his Huronian magnetic schists
(348), having exactly the same strike and dip as the schists in contact
with the granite. Furthermore, if we could prolong the magnetic
schists in the line of their strike, so far as we could ascertain, the non-
magnetic schists would be included directly in them as a component

58 BULLETIN OF THE

part. The difference now between the two rocks is perhaps due to the
action of the granite upon the schist. Microscopically this schist (353)
is composed of biotite, quartz, magnetite, and a muscovite-like mineral.
The quartz contains inclusions of the other minerals, and fluid cavities
with bubbles in exceedingly active motion compared with the usual rate
of movement. The fluid cavities-are not numerous. The part filled
with quartz and the muscovite-like mineral appears to be a portion of
the original fine sediment (mud) that held the coarser material. The
alteration and crystallization of this argillaceous detritus give with the
original quartz grains the present texture, approaching closely a gneiss.

East of the same mine the gneiss (344) was found dipping N. 60°
W. 67°, and is finely foliated. This gneiss is cut through by intrusive
granite, and by dikes of diabase and “‘diorite ” (343, 345, 346). The
latter cut the granite as well as the gneiss. (See page 45.) The gneiss
is composed of biotite, quartz, and the same muscovite-like mineral as the
schist, No. 353, which in fact it closely resembles. The quartz con-
tains microlites, scales, and grains of the other minerals and fluid cavi-
ties. The same decomposed material cementing the quartz grains is
found in this as in the schist. So far as we can tell by microscopic ob-
servation, we regard this rock as sedimentary, and perhaps only a more
highly metamorphosed condition of the adjacent schist. As its relations
to any rock older than itself were not observed, of course no definite
statement can be made. The supposed sedimentary material forming
the cement and the base out of which the mica, in part at least, has
crystallized, can arise from the decomposition of feldspar crystals in
their original position, and a material undistinguishable from it is seen
frequently to have been formed thus in eruptive rocks.’ We base our
conclusion that the rock is sedimentary upon the general structure of
the rock, especially upon the form and relations of the quartz grains to
the rest of the constituents.

The term quartzite is, we believe, when employed in its proper use,
restricted t> an indurated sandstone, and in this sense we employ it.
We believe this to be more in accordance with the generally accepted
use of the term, although, in practice, Messrs. Zirkel, Lasaulx, Hawes
(a pupil of Lasaulx), and other lithologists, employ it also to designate
quartz veinstones and other forms of chemically deposited quartz. Dr.
Wichmann, it would seem, employed it only for rocks which have no in-
terstitial or cementing substance remaining uncrystallized between the
quartz grains. He classes them under the head of non-fragmental rocks,
saying that his other class comprises all those “ which have been formed

MUSEUM OF COMPARATIVE ZOOLOGY. 59

mechanically out of the materials of older rocks,” yet he describes a
quartzite that he regards as having been a fragmental rock. In fact,
his lines between fragmental and non-fragmental rocks seem to have
been drawn from the realms of fancy, as a large proportion of his non-
fragmental rocks are evidently, both from field and microscopic charac-
ters, as truly sedimentary as those classed as fragmental ones. If we
understand Dr. Wichmann aright, we presume that the St. Peters

sandstone when indurated, as we have frequently seen it, would form a
; quartzite, while the Potsdam sandstone, if it were indurated in like
manner, would form a — sandstone, unless some of it had its cement-
ing material entirely crystallized.*

The reddish and grayish quartzite, near the northern railroad track
west of Ishpeming, is composed of quartz in rounded grains held by a
chloritic cementing material. Considerable hematite was observed as a
decomposition product. The quartz contains microlites, trichites, and
fluid cavities. The quartzite forming the fudlen wall of the New York
mine (186) is a very dark greenish-gray rock, composed of rounded
grains of quartz, and crystals and fragments of magnetite cemented by a
chloritic material. The interstitial substance in this appears to have
been entirely changed to chlorite. The quartz contains microlites, tri-
chites, and fluid inclusions more abundantly than the rock last men-
tioned. A fragment of jasper was observed in this rock. Another
specimen of the same rock (187) is composed of macroscopically evi-
dent fragments of jasper and magnetite, and quartz grains. Under the
microscope the section was seen to be composed of quartz, jasper, magnet-
ite, and chlorite. The quartz has the same inclusions, but part of the
microlites appear to be zircon. These rocks, as we have before pointed
out, were evidently derived from the underlying ore-bed (page 30).

The quartzite (197, 198) found to be older than the intrusive “ Lau-
rentian” granite (page 55) is a dark gray rock composed of quartz
grains, biotite, and fibrous microlitic cementing material. The quartz
contains fluid inclusions and little crystals of zircon. The crystals of
zircon are the same as those observed in the gneiss in that vicinity
(193), and it is not improbable that the quartzite is derived from it. In
this case the order of succession is, Ist, the gneiss; 2d, the quartzite ;
3d, the eruptive red granite (gneiss of Mr. Brooks).

The quartzite overlying the ore at the north pit of the Jackson mine
at Negaunee is made up of the ruins of the underlying ore. It is com-
posed of quartz, jasper, magnetite, hematite, and a fibrous microlitic

* Geol. of Wisc., III. 613, 615, 649, 655.

60 BULLETIN OF, THE

interstitial material. The quartz contains microlites and fluid inclu-
sions.

The rock through which the “ diorite” (page 43, No. 232) passes, is a
highly indurated feldspathic sandstone (233), in which the feldspar pre-
dominates greatly over the quartz. It has a greenish, compact, felsitic
base, holding grains of quartz. This would easily pass for a quartz por-
phyry or felsite, with those who advocate the passage of sedimentary
rocks into felsite. It is best classified as a porodite.* Microscopically
it is seen to be composed of fragments of feldspar with some quartz
grains. The feldspar is decomposed greatly, forming micaceous scales,
but shows in some cases its triclinic character. It was most probably
formed from the detritus of a granite.

Potsdam Sandstone.

The sandstones at Marquette resting upon the azoic schists are in
the upper portions fine-grained (14, 15), but below they become con-
glomeritic. The coarser sandstone (12 a, 13) is composed principally
of quartz and feldspar; the feldspar is the pinkish variety belonging to
the azoic granites in the vicinity. Many of the quartz grains are seen
toe be crystals with unworn facets; it is therefore probable that they
came from veins, and the sandstone making was quite rapid. The other
sources of the quartz were probably the granites and quartzites un-
derlying them. Coarse pebbles occur in portions of the rock belonging
to the adjacent formations: quartzite, ferruginous quartzite, argillite,
chlorite, ‘“diorite,” etc. (16, 17, 18, 19, 20, 21, 22, 23, 24, 25). The
inclosed pebbles were evidently when deposited nearly, if not quite, in
the same condition as they and the rocks from which they were derived
are to-day ; as was pointed out by Foster and Whitney. South of the
Carp River, in the locality figured by Messrs. Foster and Whitney, the
sandstone strata are seen to abut against and overlie the vertical edges
of the quartzite (29, 30, 31, 32, 33, 34). The dip was about 8. 20° W.
16° to 18°. The Sandstone at Presque Isle contains the same materials
as that south of Marquette, but has suffered a local modification described
in connection with the peridotite of that point ;— to which we now pass.

‘ Peridotite and Serpentine.

The chief rock at Presque Isle, north of Dead River, is a peridotic

one, composed of olivine, enstatite, and diallage, which is the composition

* Bull. Mus. Comp. Zodlogy, V. 280.

MUSEUM OF COMPARATIVE ZOOLOGY. 61

of lherzolite. In places, this rock is much altered, forming a serpentine
(65, 66, 67, 68, 69, 70, 71, 72, 73, 74). We find every gradation, from
the rock only partly altered to that which is so completely changed to
serpentine that only traces of the enstatite, diallage, and olivine remain.

Under the microscope, the rock (65) is seen to be made up of rounded
grains and crystals of olivine, held in and often completely surrounded
by the enstatite and diallage. These minerals evidently crystallized later
than the olivine, and play the same 7é/e here that the augite does in dia-
base, the glass in basalt, and quartz in granite. The olivine is traversed
by fissures, along which the usual serpentinous alteration has taken place.
In many, the alteration is confined to the vicinity of the fissures and the
periphery of the olivine, but others are changed throughout. Much
black dust comes in the altered portions (magnetite?), as a residue
Jeft over in the decomposition of the olivine and the formation of the
serpentine. In many cases this black residuum forms a rectangular or
irregular network or grating throughout the changed olivine. The
enstatite is altered along the cleavage planes and network of fissures
by which it is traversed. It does not become changed to the serpentine
so readily as the olivine. All contain inclusions of black octahedral®
crystals that are presumably magnetite, as the powder is magnetic, and
no trace of chromic oxide was found by chemical tests. Besides the ser-
pentine, there occur, as other alteration products, feldspar (1), viridite,
and dolomite (?). The hand specimen (65) is a grayish black (almost
black) rock, showing under the glass a little serpentine, enstatite, and
magnetite. It weathers somewhat brownish.

In other specimens from the same rock, but more altered, we only
find traces of the original structure. The formation of the serpentine
along the fissures, and the network of magnetite, usually are well marked
after the enstatite, diallage, and olivine are entirely altered. The serpen-
tine, unless it suffer alteration itself, generally shows under the microscope
its original structure, as it was formed along the fissures. One section
(71) shows simply greenish pseudomorphs after olivine enclosed in a car-
bonate, presumably dolomite. Another section (74) is composed now of
serpentine and magnetite, and, if it were not absolutely known whence
it came, its derivation could only be told by the arrangement of the mag-
netite. Certain of the specimens are largely composed of the dolomite
observed in No. 71, and microscopic as well as field examination renders
it most probable that Dr. Rominger’s stratified dolomite (72) is simply
a more highly altered portion of the peridotite. No. 71 came from the
east side and out of the same upper formation as No. 72. This is a

62 BULLETIN OF THE

reddish brown and greenish serpentine, traversed by a fine network of
dolomitic veins. The microscopic characters of the decomposed perido-
tite were given to some extent ‘by Dr. Wichmann, who, it would seem,
had only the serpentine, under which name he describes the rock.*

The geological history of this rock is very mteresting. Dr. Houghton
thought that it was an eruptive rock, and younger than the sandstone
which was uplifted by it, believing it to be a greenstone impregnated
with serpentine. He states that, near the line of junction, the sedi-
mentary rock has been greatly shattered, and its fissures filled with
injections of calcareous matter. Dr. John Locke thought the “light
green trap” was interfused with the sandstone at this point.

Messrs Foster and Whitney considered that the rock was an immense
consolidated lava flow, although it wanted the vesicular structure, while
the part filled with the white veins was regarded as a volcanic sand or
ash deposited on the lava stream. Younger than this azoic lava was the
sandstone deposited upon it (Potsdam). Chemical analysis was given of
it, but no name assigned to the rock. Later, this was regarded as
closely related to serpentine by Professor Whitney, who gave three
‘analyses of it.f Later, Dr. Hunt, accepting Professor Whitney’s analy-
ses, regarded this rock as a somewhat impure sedimentary serpentine
belonging to the Huronian series.

Dr. Rominger later regarded this rock as a half-decomposed basalt or
highly ferruginous serpentine ; the part filled with the veins was taken
to be an older sedimentary rock, a dolomite, upheaved and broken by
the trap, and overlaid by the conglomerate and sandstone. This sand-
stone is supposed to have been deposited in the inequalities of the
underlying rock following its contours. He thought it most probable
that the sandstone was deposited at its present inclination, although it
may have been slightly upheaved since. The conglomerate beds at the
base of the sandstone are said to contain numerous fragments of the un-
derlying rock, We regard this peridotite as an eruptive rock, younger
than the sandstone overlying it, and agree in this particular with Dr.
Houghton. The portion filled with veins, that was taken by him as
a sedimentary rock belonging to the sandstone, or a mixture of sand-
stone and trap; as a volcanic sand or ash, by Messrs. Foster and Whit-
ney; and as a dolomite, older than both the trap and sandstone, by Dr.
Rominger,— we regard as simply the upper portion of the intrusive mass
modified by its contact while heated with the overlying sandstone, and
by the percolating waters since.

* Geol. of Wisc., III. 619, + Am. Jour. Sci., 1859, (2,) XXVIII. 18.

MUSEUM OF COMPARATIVE ZOOLOGY, 63

As we differ so strikingly in most particulars from the geologists
quoted, it is necessary to give our reasons therefor. Only part of a day
could be spent at Presque Isle; therefore, many things that ought to
have been examined could not be. On the southeastern side, the sand-
stone dips quite irregularly from twenty to thirty degrees southerly. The
strata follow the curve of the underlying peridotite, forming in places
anticlinals. The distinction between the sandstone and its underlying
rock was everywhere seen by us to be well marked. The surface of the
peridotite is in rounded knobs, the whole mass itself in general outline
forming one immense knob. ‘The sandstone and conglomerate were ex-
amined, and found to conform in their stratification to the contour of the
whole mass, having the same waving outline; also, for from two to three
feet above the peridotite, they are indurated, changed, and show charac-
ters that we regard as evidence of heat action and of hot waters. They
are filled with vein and chalcedonic quartz, and hardened and reddened
the same as is the sandstone immediately underlying the melaphyr over-
flows in the Copper district (75, 76, 77,78, 79). Certain portions have been
changed, so that they resemble a volcanic ash, although they are simple
ferruginous sandstones (78). Above the limit of baked sandstone and con-
glomerate comes the unaltered ordinary red sandstone (81). Microscopie
sections of the indurated conglomeritic sandstone show that much of the
quartz is a secondary water deposit since the deposition of the fragments
composing the rock. We searched carefully for the pebbles or fragments
of the underlying rock in the conglomerate, which Dr. Rominger states
are abundant, but could find none. We have been unable to find either
macroscopically or microscopically a single trace, so far, of the peridotite
or of its veined portion (dolomite of Rominger) in the conglomerate or
sandstone. The peridotite forms abundant pebbles now upon the beach,
_ which, had the conglomerate been formed upon it, should have been
included. The conglomerate and sandstone contain the same material
in pebbles, etc. that the sandstone and conglomerate do in the Mar-
quette quarries and near Carp River. Had the sandstone and conglom-
erate been laid down upon the irregular surface of the peridotite, they
should have abutted against its unconformable portions, the same as
they do against the quartzite at Carp River; instead of this, the strata
conform to the curves of the peridotite, like layers of blankets, forming
anticlinals and synclinals. The dip in many places, especially on the
southeastern side, is too steep and irregular, while the strata are con-
tinuous, to have been formed at that angle by sedimentation. The
induration of the sandstone and conglomerate, and of the enclosed peb-

64 BULLETIN OF THE

bles, as well as the deposition of the silica, do not occur where the
sandstone has been seen to come in contact with the ‘“ Huronian”
schists and quartzites. From the above facts we feel that we are justi-
fied in dissenting from the views of most of those who have written
upon this locality.

At the eastern portion of Presque Isle, either a fault or a protrusion of
the peridotite up through the sandstone exists. This locality we were
able to examine only a minute or two, on account of an approaching
thunder-storm, while we were in a row-boat, but it deserves further care-
ful examination. The best serpentine that we saw upon Presque Isle was
observed at this place. In the thin section, the more serpentinous
portions of the peridotite are frequently seen to contain dolomite, and
fragments effervesce freely in hot hydrochloric acid. The upper portion,
supposed to be dolomite by Rominger, extends as a sheet of variable
thickness over all the peridotite separating it from the overlying sand-
stone. This, so far as we can tell, is the upper portion of the peridotite, af-
fected by direct contact with the sandstone, and by the action of hot waters
since, at the time the silica was deposited in the conglomerate. This
part is filled in with impure dolomitic veins, which, it seems, caused Dr.
Rominger to pronounce the rock a dolomite, although the veins have
the characters of being secondary water deposits, as they were described
by Messrs. Foster and Whitney, and not igneous injections, as they were
thought to be by Dr. Houghton. The unmistakable peridotite has in
places the same structure. The peridotite is much fissured, breaking up
into rounded masses, cemented by segregated serpentine. We regard
the peridotite as eruptive, and feel that its field and microscopic charac-
ters both point to the same conclusion. The manner of eruption was
probably something like the laccolites described by Mr. G. K. Gilbert ;
on the sides the strata were arched and bent upwards, but on the eastern
end either a fault or protrusion exists. This place would afford an
excellent chance to study the relations of the sandstone to the peridotite,
if the contact of the two can be seen.

If we are right in our observations and conclusions, this locality has
an important bearing upon the origin of the serpentine here, showing
that it is a metamorphosed eruptive rock, and of younger age than at
least some one hundred feet of the sandstone. It further shows that,
so far as this is concerned, lithology fails in giving the age of a rock,
this having been indorsed as good ‘‘ Huronian” ;* also that an eruptive

* Mr. Brooks thinks ‘‘it is not certain that this is of Huronian age.” (Geol. of
Wisce., I1I. 659.)

MUSEUM OF COMPARATIVE ZOOLOGY. 65

rock may be so changed as to be taken by observers for a sedimentary
stratified one, even a good dolomitic limestone. The origin of the ser-
pentinous part by direct change i situ of a peridotite (eruptive), as well
as by the filling of fissures in the peridotite by serpentinous material
derived from the surrounding rock, would seem in the main to be
consonant with the observations of Bonney, Becke, Berwerth, Dathe,
Doelter, Drasche, Hochstetter, Koch, Lemberg, Sandberger, Streng,
Tschermak, Zirkel, and others. Peridotite, which we provisionally
classed with gabbro under basalt, in a preliminary publication ‘On the
Classification of Rocks,” * it would seem from further and more extended
study, should be classed as a distinct species; and some other rocks
may possibly belong with it. This species would represent a more basic
one than basalt, containing generally between thirty-five and forty-five
per cent of silica, or, more nearly, forty to forty-three per cent. The
reasons for this view it is intended to give fully in another publication,
but they would be out of place here. :

The following analyses (incomplete) of this peridotite were made and
published by Prof. Whitney : —

1 & II, III, EV.
SiO, 88.24 36.95 37.25
Al203 1.48
Fe203 6.75 12.90
34.50 16.50
FeO 14.14 19.52
MgO 14.83 33.07 28.67 14.83
CaO 1.42
NaO Be a 97 1.16
H.0 9.53 10.40 10.89
100.00 98.86

Analysis I. is taken from Foster and Whitney’s Report on the Geology
of Lake Superior, II. 92. Analyses II., IIL, and IV., from the Ameri-
can Journal of Science, (2,) XXVIII. 18.

Three miles and a half northwest of Ishpeming, or one mile and a half
west of Deer Lake, serpentine occurs abundently on the land of Mr.
Julius Ropes, postmaster of Ishpeming.t This rock, although quite
hard, forms very beautiful specimens when polished (234, 235, 236, 237,

* Bull. Mus. Comp. Zodlogy, V. 279.

+ First Annual Report of the Commissioner of Mineral Statistics of the State of
Michigan, pp. 204-206.

VOL. VII. — NO. 1. 5

66 BULLETIN OF THE

238, 239, 240, 241, 242, 243, 244, 245, 246). Associated with and
comprising probably part of the same formation is a greenish and grayish
limestone (247, 248, 249, 250, 251). In one place much chrysotile was
seen, which had formerly been regarded as asbestus (252).

No. 235 is a beautiful green serpentine, giving a colorless section
holding magnetite. Under the microscope this shows a most beautiful
fibrous aggregate polarization. Other sections (241, 242, 243, 245)
show a more coarsely fibrous aggregate polarization, and are composed
of serpentine and magnetite. The magnetite is seen here to be arranged
in the same way that it was in the more decomposed peridotite of Presque
Isle, forming a network corresponding to the outlines of the grains and
fissures in the olivine, as well as occasionally a network in the altered
olivine itself. Although we find no trace of either olivine or enstatite in
this serpentine, this structure gives a strong probability that this rock
was originally in nature and origin a peridotite. Every microscopic
character in this serpentine indicates that it is formed by direct altera-
tion 7m situ from another rock, and, so far as we can now tell, that was
an olivine one. Whether this is of the same age and origin as that at
Presque Isle or not can only be determined, if at all, by studying its
relations to its associated rocks.

General Discussion and Results.

The historical part of this paper we have endeavored to bring down
to the date of its completion. As the historical portions of both the
Iron and Copper districts were, in the main, written in 1879, the lat-
ter material has been added as best it could be done. On March 6,
1880, through the courtesy of Prof. T. C. Chamberlain, Chief Geolo-
gist of the Wisconsin Survey, we received an advance copy of that por-
tion of the third volume of his survey publications which gives Dr.
Arthur Wichmann’s microscopic analyses of some of the rocks in the
Iron district and Appendices A and B, or from pages 600 to 663,
This detached portion has been referred to repeatediy in the preceding
pages, but no connected account was or need be given of it. On April 8
the complete volume was received, but as the preceding portion of our
work was, with the exception of a few pages, already prepared for the
press, and in part struck off, it became necessary to incorporate all
mention of it in this portion of the paper at this date (April 10,
1880).

The observations and figures given in the preceding text show conclu-
sively that the statements of Messrs. Dana, Kimball, Hunt, Brooks, and

MUSEUM OF COMPARATIVE ZOOLOGY. 67

others, that the iron ore is interstratified in the associated schists,
are incorrect, and only return to the view advocated by Mr. Foster in
his early publication. So far as geological science has now advanced,
the facts observed can only be explained by the eruptive origin of both
the ore and jasper, as they make the same formation. The only escape
from this conclusion is the supposition that the ore and jasper have been
rendered plastic 2m stu, while the chloritic schist has not been. Such a
supposition Mr. Brooks was forced in part to adopt.* That the ore and
jasper have been thus rendered plastic, while the schists, quartzites, and
other associated rocks have not been, is too absurd, chemically or geo-
logically, to be tolerated for a moment as an hypothesis. Should it or
any other theory be proved to be correct in actual fact, then it is to be
admitted ; but when one resorts to theories that are not sound scientifi-
cally, merély to escape from a dilemma that a. former theory brings him
to, he is neither philosophical nor scientific. Theories must conform to
facts, not the facts to the theory. We can point out facts whether they
can be explained or not, but the theory must conform to our present
knowledge. The ore and jasper show that they are the intrusive bodies
by their breaking across the lamination of the schists and other rocks, by
the changes that take place in the latter at the line of junction, by horses
of schist being enclosed in the ore, by the curvature of the lamination
produced by the intrusion of the ore and jasper, etc. Not the slightest
sign of the plasticity or intrusion of the schists relative to the ore or
jasper was seen. That the present lamination of the schist existed prior
to the intrusion of the ore and jasper is shown by the effect of the latter
upon and its relations to it. That this lamination is the original plane
of deposition is for part of the schists not known; but whether it is or
not, it has been taken to be such by the observers quoted in the estab-
lishment of their theories, and they must abide by it. The lamination,
however, coincides with many of the well-stratified rocks adjacent, and
in some of these the ore and jasper were unmistakably intrusive. The
schists that retained well-marked stratification planes showed in some
places extraordinary contortions, one specimen (293) showing a syn-
clinal and anticlinal fold, requiring, were the top eroded, the counting
of the same layer four times in the width of two inches. This is only
one case out of numerous ones observed (292, 292+, 302). In the fine-
grained detritus composing some of the schists it is quite likely true that
the lamination does not coincide with the original bedding ; but if it does
not, then the breaking of the ore across any chosen plane whatsoever,

* Geol. of Mich., I. 139, 140.

68 BULLETIN OF THE

except the lamination plane, can be shown more easily than in the for-
mer case.

The ore and jasper seem to have been erupted in huge bosses and
overflows, as well as intruded into the schist in the form of long arm-
and wedge-like masses or sheets. On account of the banded character
of the jasper, and the intrusion generally being nearly in line of the lami-
nation in the large mass, they have an apparently stratified character
to those who believe any “striped” rock is a sedimentary one; but when
examined in detail, and in places where the relations can be seen, they
prove to be eruptive. Those who advocate the sedimentary origin only,
take the jasper and ore as a whole, and, because it is apparently to them
stratified, assume without further question or examination that it is so.
We have gone upon the principle, that the relations of rocks to one an-
other show the origin of each one except the oldest, and this must be
the arbiter in every case when the other characters are doubtful or are
questioned. It happens then that this is largely a question of methods
and principles of observation.

The natural work of mining is to obscure or destroy the geological
evidences; furthermore, the natural changes that have taken place in
the constitution of the rocks, the decomposition, the uplifts, fractures,
foldings, and other accidents which they all have suffered, tend to in-
crease the difficulty of finding such proof. Of necessity the characters
show best upon the walls of abandoned open pits which the rain had
washed clean, but they were also found in the present workings. Like-
wise they are best studied in comparatively small masses, partly because
their relations are easier seen, and partly because the miner generally
leaves no others that can be studied. We were enabled, however, to
observe the intrusive relations, not only of small masses, but of some
containing thousands of tons. The small masses were, however, either
scen to be joined, or had been joined until cut off by mining, to the main
body. The view that they have been rendered plastic em stu is not sus-
tained by the facts, and when we take into consideration the associated
rocks is absurd on its face. The facts, then, sustain the views and ob-
servations of Messrs. Foster and Whitney, and show that the work of
the other observers "has been superficial and inaccurate. We are
well aware that objections from a metallurgical or chemical stand-
point have been raised against the theory of the eruptive origin of
hematite and silica together, in such forms as we now find them. If the
ore was magnetic at the time of eruption, and has since been altered,
this objection is then done away with. The secondary changes that

MUSEUM OF COMPARATIVE ZOOLOGY. 69

have occurred in the rock since eruption, as shown by microscopic exam-
ination, may also help. It is well known that there are facts in every
science that it is not able to explain at any one given time ; but the
facts exist the same, and the science in time rises to meet them. So in
this case the fact is they are eruptive, and the burden of chemical ex-
planation rests upon the chemist, not upon us. He must explain it
sooner or later, unless he disproves our observations. Crystals of hema-
tite crystallizing from the molten magma of trachytes and rhyolites
have long been known, and are described in all the standard works
on micro-lithology. These then offer the same problem, and prove that
hematite can be crystallized directly out of the same molten magma,
and at the same time with the silica and silicates. It is the business of
the chemist to meet the facts, and not for us to make the facts con-
form to his knowledge or theories. It is our business to state what we
see and find, and his to explain it if he can, but not to deny it for the
simple and:sole reason that he cannot cope with it in the present state
of his knowledge. The eruptive origin of the iron also has a bearing on
the theory that its presence indicated a vast amount of organic life in
the “ Huronian” epoch.

We have found that a large proportion of the rocks said to be inter-
stratified, and to pass by insensible (or any other) transitions into the
adjacent rocks, are eruptive, and do not so pass into the country rock.
The assumption that they were stratified was based on their foliation
being parallel to their walls, on their being intrusive approximately par-
allel to the lamination of the schists, their general resemblance to the
country rock of similar chemical composition, the inability of the observ-
ers to find their lines of junction, and the lack of knowledge of the same
observers of the characters of eruptive as well as of sedimentary rocks.
Their decision in this, as before, was based on a mere superficial glance
over the surface, and the assumption that, because a rock looked as
thongh it was stratified, i. e. had any marks that they thought indicated
stratification, it must of necessity be stratified. No effort was made to
find out the real relations of the rocks to one another. No attempt
was made to see whether one rock was laid down on another as a sedi-
mentary bed, or whether it was an overflow or intrusion. They were
“striped ” or foliated, jointed or showed cleavage planes, and that was
enough ; any further observation was superfluous. They assumed that
Messrs. Foster and Whitney’s work was erroneous without making the
necessary observations to prove it so, and the geological world accepted
it without question because it agreed with the fashionable theories.

70 BULLETIN OF THE

The intrusive rocks belong in general to the basalts, but are of course
old, and in the majority of cases greatly altered. One probable ande-
site as well as intrusive felsites (rhyolites) was discovered. These rocks
had never been noted before by the previous observers. One class
of the intrusive rocks can be referred to the basalts only with doubt, as
the necessary proof of their original composition is thus far wanting,
i. e. the actinolite rocks. The evidence is very strong that in the other
basic intrusives all the varieties are produced by the alteration of their
constituents, and that they were not erupted in their present state.

It is to be noticed that, while we have found olivine abundantly in the
diabases, Dr. Wichmann states that ‘olivine diabase is not present
amongst the recks from the iron region of Lake Superior.” *

The “‘ soft hematites” are doubtless produced by the decomposition of
the jasper and its ore, brought about by the fracturing of the rocks by
the intrusives and by the secondary action of water, presumably hot,
on account of the microscopic characters of the quartz deposited by it.
Besides the “soft hematites” there occur the quartzites and conglom-
erates derived from the ore and jasper, as well as the sandstones and
schists impregnated by iron, which are sometimes mined to a slight ex-
tent.

We have heretofore seen that the view that the ‘ Huronian ” uncon-
formably overlies the ‘‘ Laurentian” has been only supported by the
fact that the foliation of the latter did not conform in its dip to the
lamination of the former. This proof is of no value unless it can be
shown that both rocks are stratified and i situ. That the latter is not
so, we have seen in numerous localities. Heretofore the two systems
have not been observed in contact, but recently statements have been
published that their junctions have been seen in other regions.t The
statement is made that both rocks are stratified, but no proof is adduced
to show on what the conclusion is founded, and, although the contacts
were said to show beautifully, nothing was published indicating that the
kind and manner of the junction was observed. It would seem that
even here the decision concerning the unconformability was based on
the foliation only.

So far as the Marquette district is concerned we have shown very
much stronger and more abundant evidence to prove that the “ Lauren-
tian” granite is younger than the “ Huronian,” and an eruptive rock, than
has been advanced by Mr. Brooks (the only one who has advanced any-
thing called proof) to show that it is older. Further, the inability of the

* Geol. of Wisc., III. 627. t Ibid., III. 98, 108, 117.

MUSEUM OF COMPARATIVE ZOOLOGY. 71

later observers to distinguish the eruptive rocks, even in the “ Huro-
nian,” detracts from their evidence concerning the ‘ Laurentian.” The
granite that Mr. Brooks placed as Formation XX. of the ‘“ Huronian,”
merely because that was the easiest way to dispose of it, unless he
wished to acknowledge that his “‘ Laurentian” granite or gneiss was in-
trusive in the “ Huronian,” bids fair to absorb now all the “ Laurentian”
region, if we can judge from what Mr. Brooks writes. He says: “ Dr.
Rominger considers certain granitic and gneissoid rocks north and south-
west of Marquette, which I did not study but regarded as Laurentian,
to belong to this series. I have but little doubt but that the younger
Huronian rock made ott in the Menominee region (the granitic bed
XX.) will yet be identified in the Marquette region, and will be found to
be more or less gneissic. The very rocks mentioned above may pos-
sibly be Upper Huronian ; the granites, etc., southwest of Michigamme
lake very probably are.”* Although this granite is in the region mapped
as “ Laurentian” by Mr. Brooks, he does not tell us how to separate it
from the “ Laurentian,” or where the dividing line is to be found. How
does he know that it is not the same as the other “ Laurentian” rocks?
He has never made any examination to see whether it is or not, and
in the above-quoted remark of his he virtually acknowledges that he
knew nothing of the rocks that he mapped as “ Laurentian” in the
district since examined by Dr. Rominger.

We tried to find some point where we could trace rock continuously
from well marked and mapped “ Laurentian” into the “ Huronian,” but
were unable, with the time and opportunity at our disposal, to do more
in that direction than we have already pointed out. The evidence is
strong, but not so conclusive as we could have wished ; yet what would
it have availed us if we had found such a locality? We should have
been told: “Oh! that is Fornfation XX. that you found; we knew
nothing about the region, so we mapped it as Laurentian.” May we
suggest that hereafter geological maps of Lake Superior be colored as
“ Huronian,” and “Formation XX.”? Let us substitute the last term
for the “ Laurentian” at once, and have done with it before Formation
XXII. is born. At another locality, the granite that Mr. Brooks as-
signs to “ Formation XX.” Professor Irving places under the ‘‘ Kewee-
nawan.” t

While at Lake Superior the followers of Dr. Hunt thus place a
troublesome granite cutting the “Huronian” as the latest formation
in it (except one), in Eastern Massachusetts a granite said to cut and

* Geol. of Wisc., III. 529, 530. t Ibid., III. 193-195.

72 BULLETIN OF THE

to be intrusive in the Primordial slates, as well as in the “ Huronian”
so called, is for this reason placed by them at the base of the ‘‘ Huro-
nian.” Furthermore, the diabases that are intrusive in all, even the
youngest rocks known here, are for that reason considered to be the
equivalents of the ‘ Norian,” and regarded as older than the “ Huro-
nian.” Now, if the granites are intrusive in the Primordial or Braintree
slates, as we know the felsites are intrusive in the granites, and as we
know the diabases are in all, we naturally should, as we have done,
regard these rocks as crystalline eruptive ones, owing their crystalline
character to crystallization from the molten magma, and geologically
younger than the Primordial, i. e. Palseozoic rocks. But we see now
that we were mistaken. Why not go to the Cordilleras and say of the
basalts, These are “ Norian” or ‘ Naugus Head”; of the rhyolites, These
are ‘“‘ Huronian” ; of the trachytes and nevadites, These are “ Lauren-
tian,” or “Formation XX.” ; of the andesites, t Why not station
one’s self by a volcanic crater, and determine, as the eruption takes
place, whether Formation V., XV., or XX. is rushing by 4

It seems, then, that in different localities different methods of inter-
preting the same facts are resorted to, but for the same purpose and
result, —the rocks come out ‘“Huronian” every time. Taking into
account the methods pursued; the hypothesis, yet unproved by any
careful, accurate work, that lithological evidence is conclusive; the
assumption that foliation, banding, etc. of necessity prove stratifica-
tion; the practice of inserting faults in the formations wherever it
becomes convenient to do so in order to carry out the theory ; that Dr.
Hunt, in order to sustain his views, has, in Eastern Massachusetts,
directly stated that the granite cuts the felsite, when the reverse is
exactly the case, dike after dike of the latter cuttimg the former, as
pointed out by us before,* and since most conclusively shown by Mr.
J.S. Diller; that the Norian rocks are probably in all cases eruptive
basaltic rocks (gabbros); that the Keweenawan system has no founda-
tion except in erroneous observation, as it conformably overlies the
Potsdam sandstone, as we shall show later ;— taking these and other
things into consideration, we feel that the very basis on which the Lau-
rentian, Huronian, and other such geological epochs were established, is
yet an open question for discussion. Even in Canada the evidence is
very far from being clear that the relations of the Laurentian and Huro-
nian are what they are supposed to be. The agreement of hundreds

* Bull. Mus. Comp. Zool., V. 282.
t Proce. Bost. Soc. Nat. Hist. XX., 354.

MUSEUM OF COMPARATIVE ZOOLOGY. 73
of geologists in every quarter of the world does not establish any-
thing, if that agreement is based on the same theories and methods,
unless the theories and methods are correct. The evidence is clear
enough in New England and at Lake Superior that the theory is un-
proved, and the methods and observations incorrect or superficial. It
seems to us that a striking commentary on the value of lithological
characters is afforded in the Marquette district by the letters and the
comments upon them given on pages 657 to 660, inclusive, of the third
volume of the Geology of Wisconsin.

We frequently are informed that microscopic analysis will make up
for all deficiencies in field work; that one can tell in this way whether
a granite or any other rock is eruptive or metamorphic ; that Formation
XX. is to be distinguished in this way from the Laurentian granite,
etc., etc.*

The study of rocks microscopically enables us to investigate their
structure, constitution, and alterations, — the structure of their constitu-
ents and the various relations that these bear to one another, as well as
the order of their formation. It gives us the internal history of a rock
more or less complete, —a thing that no other known method will do.
It enables us to tell the species, arrange, and generally to classify our
rocks. With the exception of such as are greatly altered, it enables us
to distinguish the fragmental from the non-fragmental forms. When we
are familiar with the microscopic characters of unchanged sedimentary
rocks and of unaltered volcanic ones, they having been known to be
such from field evidence, we have a basis for recognizing rocks, con-
cerning whose field relations we know nothing, as belonging to one or
the other of these classes, the same as by the unaided eye we recognize
a coarse granite or conglomerate. This of course only applies to rocks
concerning whose nature and origin there is no dispute; or to those
which under the microscope show such undoubted evidence of their
origin that it cannot be rejected. If a rock is clearly seen under the
microscope to be made up completely of fragments, no one would doubt
that it was a fragmental rock, even if it looked to the unaided eye as
though it were a non-fragmental one. Jn like manner, when a rock has
the microscopic characters of an eruptive one, we feel that it is right to
regard it as such, even if it was supposed (not proved) to be a sedimen-
tary one by the collector in the field. Both of these are of frequent
occurrence in the work of a lithologist. Take now the great interme-
diate class of rocks, those that are so altered that their original charac-

* Geol. of Wisc., II. 73; III. 194, 255.

74 BULLETIN OF THE

ters are greatly or entirely changed, and the case is different. We can
only proceed in safety when we know their field relations, or those of
rocks that are like them. In order to know the microscopic characters
of a sedimentary granite (if such a rock exists), it is necessary to study
one that is known beyond question to be sedimentary, and to compare
it with the most highly altered eruptive ones known. By this method
of proceeding, always taking as the basis rocks whose relations to their
fellows were known, diagnostic points,of great value would be found,
and a more just idea of the relations of the fragmental and non-frag-
mental forms obtained. The field evidence would have to be the
arbiter in all cases. Ifa rock is eruptive, or if it is sedimentary, it
is so, whatever may be its microscopic characters. In this class of
rocks lithology is at present weak, and assumptions take the place
of facts.

Although in no case in this paper have we attempted to give any
elaborate microscopic analyses, but only a few of the more general facts,
we have shown plainly enough the fallacy of determining the geological
relations of highly altered rocks by microscopic analysis alone. Any
one who takes pains to read pages 533 to 599, inclusive, of the third
volume of the Geology of Wisconsin, will doubtless be convinced that
different observers, under the present method of microscopic analysis
and classification, reach widely different results in the study even of the
same specimens. He can further compare our description of the Picnic
point rocks with that given on page 567, and also with Mr. Brooks’s state-
ment that granite dikes ‘have never been observed in the Marquette
series ” (J.¢., p. 452). It is of course worthy of remark, that of the litholo-
gists who have microscopically studied the rocks of Lake Superior, Messrs.
Pumpelly, Wright, Irving, Hawes, Rutley, Julien, Tornebohm, and Wich-
mann, not one, so far as we can learn, had at that time any especial per-
sonal acquaintance with the characters of modern unaltered eruptive
rocks, except possibly the two last named. Yet it is essential that one
should be thoroughly acquainted with the unaltered forms of rocks be-
fore attempting to solve the most difficult lithological problems on the
globe, i. e. those relating to the altered forms. As descriptions of what
these observers saw in the individual specimens examined by them, their
work is undoubtedly of great value; but beyond that there is a great
chance for differences of opinion concerning their conclusions, or the
basis upon which these were established.

The sedimentary rocks of the Marquette district generally give evi-
dence of being shore deposits, and although they may have been deeply

MUSEUM OF COMPARATIVE ZOOLOGY. 75

buried under later formations, yet in themselves we consider that they
give no evidence of it.

The general structure of the country would seem to be as follows.
The schists, sandstones, etc., having been laid down in the usual way,
were then disturbed by the eruption of the jasper and ore; this
formed the knobs of jasper, the banding belonging to the fluidal struc-
ture, and not to sedimentation. Besides occurring in bosses, the jasper
was spread out in sheets, and intruded through the rock in wedge-
shaped masses, sheets, and dikes. Much of the original rock still re-
mained horizontal, and new sedimentary deposits continued to be formed
out of the jasper and the other rocks. Next came the eruption of * dio-
rite,” which completed most of the local folding and tilting of the strata.
Finally, the granite eruption took place on both sides of the ‘ Huronian,”
uplifting and contorting the strata near it, and perhaps laterally com-
pressing the enclosed iron-bearing rocks. No basis exists so far, then, for
the scheme of formations laid down by Mr. Brooks, as it was founded on
the supposition that all the rocks were sedimentary. The other results
of our work are: the showing more clearly the age, origin, and nature
of the peridotite at Presque Isle, and the formation of serpentine from
it in situ ; the finding of ottrelite schist as a metamorphosed rock from
the ordinary schist ; the showing that tourmaline and olivine are more
abundant here than heretofore known; the finding of granite and fel-
site within the Marquette district, etc., ete.

Concerning the serpentine (peridotite) of Presque Isle Mr. Brooks re-
marks, “It is probably Huronian, and presents some of the phenomena
of an eruptive mass.” * Later he says, “It is not certain that this is of
Huronian age.” TF

Although in deference to the common custom we have employed the
term jasper in writing of the silicious eruptive rocks associated with the
ore, in reality it is not properly called so. It is often uncolored, and
has then generally been designated by observers as a quartz schist, they
believing it to be sedimentary. The rock further has been denominated
felsite or petrosilex, but physical and chemical characters remove it from
these old rhyolitic rocks. It is more acidic than the rhyolites, the silica
being above eighty per cent. We also found other eruptive rocks of like
acidic character, and, so far as our observations have now gone, it seems
probable that rocks of this class are much more abundant than we should
at first suppose. They would naturally be taken at first sight for
quartz schists, quartzites, and other sedimentary rocks, and no further

* Geol. of Wise., III. 532. Tt Ibid., 659.

76 BULLETIN OF THE

investigations be made to ascertain their relations to the associated
rocks. We would propose, therefore, that all the acidic eruptive rocks,
whose chemical and physical constitution carries them above the rhyo-
lites, should be designated as Jaspilites from tacmis and AiGos in accord-
ance with a suggestion of Professor Whitney.

Finally, so far as our work has gone, it shows that Messrs. Foster and
Whitney were right in their observations and conclusions, so far as it
relates to the geological structure of the country, or to the origin of the
rocks and ores, except the peridotite. To them and to them alone be-
longs the credit of having done their work accurately, and as thoroughly
as the circumstances would allow, while the more recent observers
and writers, Kimball, Credner, Rivot, Hunt, Dana, Brooks, Lesley, Win-
chell, Newberry, Wright, and others, have held and pushed theories in
direct opposition to the facts, until a geologist who took a different view
was regarded either with pity or derision. As regards the general geol-
ogy of the country, we feel that Messrs. Foster and Whitney’s writings
remain to-day the best and most accurate exponents. Considering the
difficulty of exploring the country thirty years ago compared with the
present, it is surprising how much they saw, how accurate their ob-
servations were, and how little has been added to our knowledge since ;
also how our knowledge and science have again retrograded, until geol-
ogists have gone back to the views of Messrs. Houghton, Hubbard, and
Locke.

The Copper District.

The earliest writer to advance any especial views regarding the cop-
per and its origin, so far as we are aware, was Henry R. Schoolcraft.*
He considers it probable that the masses of copper about the Onto-
nagon River were thrown out of volcanoes by volcanic action. The
mountains are said to be of granite (Porcupine Mountains) so far as
observed, and the sandstone to have been upheaved into a nearly vertical
position at their base by the elevation of the granite. He considers that
native copper will never be found in sufficient abundance to pay for
mining, but that probably “valuable mines of the sulphuret, the car-
bonate, and other profitable ores of copper,” will be discovered.t

In 1823, in describing a supposed vein of malachite on Keweenaw
Point, he concludes “that the entire peninsula consists of a spine of

* Am. Jour. Sci., 1821, (1,) III. 201-216. Quart. Jour. Sci. and Arts, London,
1822, XII. 422, 423.
t See also Senate Papers, 2d Sess., 17th Aug., 1822, Doc. 5.

MUSEUM OF COMPARATIVE ZOOLOGY. 77

granite, with sandstones, amygdaloid, and secondary trap, deposited
around its base.” *

Dr. John J. Bigsby regarded the Lake Superior sandstone as being
most probably of the age of the Old Red.t Commander H. W. Bay-
field, in his paper entitled “ Outlines of the Geology of Lake Superior,” ¢
regards the hills of Keweenaw Point as formed of syenitic granite, of
the same character as that at Granite Point, and opposes the idea that
the first-mentioned point is an amygdaloid district. He regards the
trap and granite as the prior formed rocks, and that the sandstone is
composed of their débris. This sandstone, which he takes to be Old
Red sandstone, is said to have been tilted by a secondary upheaving, or
subsidence of the granite.

In Dr. Douglas Houghton’s report on the copper of Lake Superior to
the Secretary of War,§$ we find the following statement: “ After having
duly considered the facts which are here presented, I would not hesitate
to offer, as an opinion, that the trap-rock formation was the original
source of the masses of copper which have been observed in the country
bordering on Lake Superior ; and that at the present day, examinations
for the ores of copper could not be made in that country with hopes of
success, except in the trap-rock itself; which rock is not certainly known
to exist upon any place upon Lake Superior, other than Keweena
Point.” The chief ore of copper that he had observed was the mala-
conite, although a small amount of native copper had been seen in
place.

Dr. Douglas Houghton states, in his first Report on the Geology of
Michigan,|| that the red sandstone ‘in the Trap regions of Lake Superior,
as in the vicinity of the Porcupine Mountains,... . is seen dipping
irregularly at a high angle from the elevated district of country, and is
there of a deep reddish-brown color.” He evidently at that time re-
garded the sandstone as belonging to one formation, from the St. Mary’s
River to the Porcupine Mountains.

Dr. Houghton in his Fourth Annual Report on the Geology of Michi-
gan,J divides the sandstones of Keweenaw Point as follows, going from

* Am. Jour. Sci., 1824, (1,) VII. 43-49.

T Quart. Jour. Sci., 1824, XVIII. 1-34, 228-269; Am. Jour. Sci., 1824, (1,)
VIII. 60-88.

t Trans. of the Lit. and Hist. Soe. of Quebec, 1829, I. 1-43.

§ Nov. 14, 1831. Discovery of the Source of the Mississippi, Henry R. School-
eraft, New York, 1834, pp. 287 - 292.

|| Lanman’s Hist. of Mich., p. 353.

{] Joint Documents, Mich., 1841, pp. 472-607.

78 BULLETIN OF THE

below upwards: “conglomerate rock,” ‘‘ mixed conglomerate and sand
rock,” and ‘red sandstone and shales.” He regards the first as a “ trap-
tuff,” and as made up of “rounded masses of greenstone and amygda-
loidal trap, of which the former make up by far the larger proportion, and
scarcely a pebble of any other rock than trap, enters into its composition.” .
The second is composed of the same materials as the first, and is conform-
able with it. The only difference is that part of it is made up of sand
composed of finely comminuted greenstone. The last, or ‘the red sand-
stone and shales,” he considers to differ widely from the preceding rocks,
and to be made up of detritus of the granitic and metamorphic rocks,
containing, however, some sand that appears to be comminuted trap.
This red sandstone extended, according to Houghton, as far east as
Grand Island, where it was unconformably overlaid by the “Gray Sand
Rock ” (e. g. the material of the Pictured Rocks), which rested upon the
uplifted edges of the former. It will thus be seen that he had changed
his views since his first report.

All these rocks were said to be traversed by dikes injected parallel to
the bedding, varying in width from fifty to four or five hundred feet.
He considered that the sedimentary rocks were all deposited prior to
the injection of the traps, which rocks he finds very abundant in the
conglomerates, and comparatively rare in the red sandstones. These
dikes pass from a compact greenstone on the southeast side to an amyg-
daloid on the northwest. He considers that they were ‘in an intense
state of ignition while in contact with the sedimentary rocks, as is
clearly shown by the very great changes that have taken place in the
rocks last alluded to. In fact, I am disposed to refer the origin of much
of the amygdaloid rock to the fusion of the lower portions of the sedi-
mentary rocks referred to, for the reason, that as we pass south from
this junction, the amygdaloid rocks wholly disappear, their place being
supplied by greenstone ; and again so intimately are they blended, that
it is frequently impossible to determine where the amygdaloid ceases
and the upper sedimentary rocks commence. Fragments of the sedi-
mentary rocks, the characters of which can be clearly recognized, are not
of rare occurrence, imbedded in the amygdaloid rock, a circumstance
which although by no means conclusive, should not be overlooked in
considering this subject. I would not wish to convey the idea that the
amygdaloid rocks have their crigin exclusively from the altered sedimen-
tary rocks, but simply that the change in the structure of the trap, from
greenstone to amygdaloid, may and no doubt does depend upon the
proximity of the sedimentary rocks to the trap, while the latter was in

-

MUSEUM OF COMPARATIVE ZOOLOGY. 79

a state of ignition.” (J. c., p. 490.) He states that the sandstones have
evidently been deposited in shoal water, on account of the abundant
ripple-marks occurring in them.

Three species of fucoids, tolerably well defined, were said to have
been found in the red sandstone. The veins are considered to be of a
date posterior to the uplifting of the beds, and cut across all three of
the sedimentary rocks and the traps. They are taken as true veins, and
their mineral contents are said to change in the same vein as the rock
changes. The gangue is said to be principally quartz with occasional
calcite, and the ore to be most abundant at or near the junction of the
trap and conglomerate. He regards this district as being in its general
characters and in its veins like Cornwall. Conglomerates were noticed
with a cement of copper, but only in the immediate proximity to con-
siderable veins. He conceived the veins “to be veins of sublimation,
or in other words to be simply filled from below by the metal in a va-
porous state, and that all the compounds had their origin from copper
in a native form.” * In 1843, he considered that the sandstone east of
Keweenaw Bay was older than the Trenton, while the western sand-
stones and conglomerates were formed during the period in which the
trap was upheaved, and were probably contemporaneous with the New
Red Sandstone.t

It will be seen here that Dr. Houghton had entirely changed his
views regarding the relations of the sandstone. In 1841, the sandstone
of Keweenaw Point was said to be older than the St. Mary’s sand-
stohe ; in 1843, to be younger. ;

Later, Dr. Houghton “said he could not speak definitely as to the
contemporaneousness” of this sandstone with that of Connecticut and
New Jersey, “but he was sure of the similarity of their structure.” ¢
Prof. B. Silliman, Jr. at the same time stated that although he had
found the copper and silver from this region “ fused into perfect union
at their two surfaces,” they were not alloyed.§

Prof. John Locke, in an article in 1844,|| entitled ‘ Observations
made in the Years 1838, ’39, ’40, ’41, °42, and ’43 to determine the Mag-
netical Dip and the Intensity of Magnetical Force, in several Parts of the

* Am. Jour. Sci., 1841, (1,) XLI. 183-186; 1844, XLVII. 106. Trans. of the
Assoc. of Am. Geol. and Nat., 1840-1842, pp. 35-38.

¢ Am. Jour. Sci., 1843, (1,) XLV. 160.

t Am. Jour. Sci., 1843, (1,) XLV. 332 ; 1844, XLVII. 107, 132.

§ Am. Jour. Sci., 1843, (1,) XLV. 332.

|| Trans. Am. Phil. Soc., Phila., 1X. 283-315, Apr. 19, 1844.

80 BULLETIN OF THE

United States,” presents the metamorphic theory of the origin of the
rocks of Keweenaw Point as follows: “The rocks of Copper Harbour,
and indeed of the whole Kewenon peninsula, are decidedly metamor-
phic, showing every degree of change produced by igneous agency, from
unchanged sandstone to compact greenstone. The stratification is, -
mostly, more or less evident, presenting in the various superimposed
layers, an inexplicable variety, some layers bearing evidence of serni-
fusion and a correspondent degree of induration and endurance, while
others seem scarcely to have been altered, still remaining soft and yield-
ing readily to atmospheric agency, and especially to the assaults of the
waves from the lake. Whether these differences have been produced
by an unequal distribution of the heat, or by an original difference in
the layers of the strata, some being of a nature more susceptible of
change by heat, I was unable to determine... . . Copper Harbour
itself seems to have been formed by the removal of a softer stratum
of metamorphic sand rock, while Porter’s Island is a part of the barrier
formed by the outcropping of a harder layer.” (J. ¢, pp. 311, 312.)

In 1845,* Lieut. D. Ruggles published a communication in which
he advanced the view that the trap was projected in dikes through the
New Red Sandstone, and that the veins were formed and filled ‘‘ by vol-
canic or igneous action, under the pressure of incumbent waters.” If
we can judge from his statements about the copper and his description
of the filling of the veins in the “Lead Region” of Illinois, Wisconsin,
and Iowa, he believed that these veins were filled by the projection of
metallic copper, enveloped in a dense atmosphere of oxygen “ from the
fountain of igneous action, through fissures in the rock strata, resulting
from concurrent disturbing causes.” When the vein was “under the
pressure of an immense mass of water,” the oxygen entered into com-
bination with the copper to form the black oxide of copper, but when
only under atmospheric pressure the oxygen escaped by sublimation,
leaving the copper to its own resources.

Dr. Chas. T. Jackson, writing in 1845,t regarded the sandstones as
probably Permian or New Red, but attributed to Dr. Houghton the
belief that the formation is Old Red, and also held that the trappean
rocks were injected dikes. The veins were taken as veins of igneous
injection, although doubt is expressed, and he says: ‘‘ When these veins
occur near the trap dykes, analcime and Prehnite also abound, and were
formed, without doubt, through the igneous agency of the trap on the
contents of the vein and the ingredients of the wall rock.” We may

* Am, Jour. Sci., (1,) XLIX. 62-72. t Ibid., pp. 81-93.

MUSEUM OF COMPARATIVE ZOOLOGY. 81

infer from this, that he regarded the fissures to be of anterior formation
to the traps. He states that “the trap rocks of Lake Superior pass
through the red sandstone and conglomerate rocks, and are interfused
with them, producing at or near their junction a very porous amygda-
loid, which is always found at the lower side of the dyke where it is
next to the sandstone.” He also remarks that he finds the copper and
silver “united together side by side by fusion without any alloying of
the silver”; “the two metals are completely soldered together at their
points of contact.” This paper was also presented to the Association
of American Geologists and Naturalists, at their sixth meeting, April
1845, published in their Proceedings (pp. 53-60), and discussed by
Prof. C. U. Shepard (pp. 60, 61). He considered that the copper
was derived from the sandstones by the action of the trap dikes upon
them. The copper was originally in the primitive rocks, “ whose lateral _
slopes were occupied with cupreous strata derived from the degradation
of the surrounding primitive ; and that whenever the trap had slid out
beneath these deposits, or in other ways come in contact with them,
they would, as elsewhere, bring to the surface rich masses of copper ;
but he was inclined to the opinion that they would not give rise to deep
and permanent mines.’’ He’ considered that the sandstones belonged to
the New Red. In an earlier portion of the Proceedings (pp. 30, 31), Dr.
Jackson remarked that “at the junction of the great dykes with the
sandstones of Nova Scotia, Maine, and on Lake Superior, a more violent
ebullition took place than that which accompanied the eruption of the
trap ranges in Connecticut, for the sandstone and trap are blown into a
perfect scoria at the former localities ; amygdaloid resembling the most
porous lavas, and immense quantities of trap tuff containing lumps of
metallic copper, evince the powerful action of trap on the sandstones
of Nova Scotia, and on Kewenaw Point, Lake Superior. .... On
Kewenaw Point we have an intimate mixture of copper and trap rock
in the amygdaloid, and I at first supposed if the amygdaloid resulted
from the interfusion of sandstone and trap, that the copper might have
been reduced from copper ores pre-existent in the sandstones; but the
absence of such ores in the sandstone in contact with or near the trap
appears to discountenance the idea, and I am more disposed, since I
have explored that region, to coincide with the opinion of Dr. Houghton
in the belief that the copper of that region is a part of the primary
copper of the globe brought up by the viscid trap.” At a meeting of
the Boston Society of Natural History,* November 6, 1844, he re-

* Proceedings, I, 203.
VOL. VII.— NO. 1 6

82 BULLETIN OF THE

marked: “There can be no doubt, however, that the metals found in
the Lake Superior amygdaloidal trap, have been fused at as high a
temperature as was required to liquify the rocks in which they are
found, for they bear evident marks of entire fusion, and are as vesicular
as the common lavas of Vesuvius, Etna, and Peak of Teneriffe.’* In -
one of the later paperst he states: “It is obvious, both from the crys-
talline forms and the mode of occurrence of this copper, that it was
deposited from a state of igneous fluidity ; and, from the circumstance
that the walls of the vein are encrusted with Laumonite, it would
appear that the spar vein itself is of igneous origin. Many other in-
stances of a similar kind indicate that the calcareous spar veins, which
traverse the conglomerate and sandstone rocks, are true veins of igneous
origin.” F

Mr. Bela Hubbard { regarded the sandstones on both sides of Kewee-
naw Point as Potsdam in age, and held that the traps were eruptive in
it. He regarded, however, the conglomerate and the “mixed conglom-
erate and sand rock” lying to the northwest of the Point as of later
origin than the trap and composed of its débris. Concerning the ‘‘ mixed
conglomerate and sandrock” he states: “As the finer strata of this
rock have been mistaken by some for the red sandrock, hereafter de-
scribed, it is important to observe that a very marked difference exists
between the two rocks; for, while the latter is made up of materials
derived from the several rock formations of the country, and into which
quartzose grains enter most largely, the former is wholly derived from
the trap rocks.” The “red sandrock” is said to be in nearly horizon-
tal strata, but having on the coast a slight dip inland, which becomes
“more apparent as it approaches the basin of Portage Lake. In its
approach to the trap, however, it is found more or less tilted from its
original horizontal position, and is also very much altered by its contact
with that igneous rock. The evidences both of the deposition of this
extensive formation, in calm and shallow waters, and of the subsequent
changes induced in it by the trap rocks, when in a fused or heated state,
are very apparent.”

Prof. H. D. Rogers§ stated that ‘at the Eagle River mine, and

* See also Proceedings of same Society, II. 110-114, Mar. 4, 1846. Am. Jour.
Sei., (2,) II. 118, 119.

t Proc. Bost. Soe. Nat. Hist., 1846, II. 112.

¢ Mineral Region of Lake Superior, by J. Houghton, Jr. and T. W. Bristol. See
also Senate Documents, 1849-50, 31st Cong., Ist Sess., III. 802-842, and 1845 -

46, 29th Cong., 1st Sess., VII., No. 357, pp. 2-29.
§ Proc. Bost. Soc. Nat. Hist., April 1, 1846, II. 124, 125.

MUSEUM OF COMPARATIVE ZOOLOGY. 83

elsewhere, the metalliferous rock is not, as sometimes supposed, a real
trap rock, but a mixture of trappean matter, and that of the red sand-
stone formation, more or less baked and modified by intense igneous
action. These semi-fused materials, in crystallizing, have very fre-
quently resulted in the following curious arrangement : the crystalline
metallic copper occupies the centre of globular and variously formed
concretions ; calcareous spar usually, but not always, invests the cop-
per; and very generally the exterior of the kernel is pure crystalline
chlorite. ... . These nodular lumps are dispersed through a base
which exhibits a sort of pasty mixture of softened red shale and true trap-
pean matter ; and many of them are so surrounded as to indicate them
to be true segregations from this semi-igneous, semi-aqueous compound.”
He regarded the sandstone as equivalent to the New Red sandstone of
the Atlantic States, and making the same formation throughout the
peninsula of Upper Michigan. In a report on the sale of mineral
lands by Mr. Relfe we find the following statement: “In the con-
glomerate rocks which overlay the trap, are to be found all the varie-
ties of copper ore of the richest qualities, offering to the smelter a
greater yield than has ever been obtained from the copper ores of
England or other countries that have contributed so largely of this
important article.” *

Sir Wm. Logan in the Report of Progresst regarded the copper-bear-
ing traps of Lake Superior as of a higher antiquity than the Potsdam
Sandstone, and attributes the same view to Dr. Houghton in 1841.
Logan’s statement seems to be erroneous regarding Dr. Houghton’s
views in this respect. He considered the traps older than rocks which
Logan regards as Potsdam sandstone, but of whose age he expressed no
opinion in his Report for 1841, to which Logan refers. In 1843, as
we have seen before, Dr. Houghton not only took the copper-bearing
rocks to be of the age of the New Red sandstone, but also considered
Logan’s Potsdam sandstone as belonging to some formation older than
the Trenton. In this way he had reversed his view of the order of
succession in 1843, which Logan attributed to him as late as 1847.
(l. c., p. 34.)

Mr. Bela Hubbard in his report for 1846 § states concerning the trap

* Reports of Committees, 29th Cong., 1st Sess., Vol. III., Doc. 591, pp. 2, 3,
1845 - 46.

+t Geol. of Canada, 1846-47.

$ 1849 and 1851, Reports of Progress. North Shore of Lake Huron, p. 20; Brit.
Assoc., pp. 59-62, 1851.

§ Senate Documents, 1849-50, III. 371-935, p. 887.

84 BULLETIN OF THE

of the Porcupine ranges that, “ while we desire to avoid any theoretical
conclusions as to the mode of their formation, we cannot but observe
that the character of the entire trap formation is rather that of a succes-
sion of overflows, than of simultaneous uplift in mass ; in other words,
it may be considered as made up of beds of the different kinds superim- _
posed upon each other.” He also regards the “ eprdote veins” as in the
main contemporaneous beds whose mineral contents were deposited
with the bed.

Dr. D. D. Owen, in his Report of a Geological Reconnoissance of the
Chippewa Land District of Wisconsin, etc.,* of the date of April 23d,
1848, regarded the sandstone of Lake Superior as younger than the Car-
boniferous age, basing his conclusions, as Dr. C. T. Jackson had done,
on lithological and mineralogical characters only. (/. ¢., pp. 57, 58.)
In his final report (Oct. 30th, 1851, pp. 187-193), this view was aban-
doned, and the‘sandstone regarded as Potsdam.

Dr. C. T. Jackson t remarked in 1848 that the sandstone agreed in
its characters with those of the oldest of the sandstone formations. On
. Jan. 2d, 1850, (1. ¢., _p. 228,) he stated that he wished to correct the
record, as the preceding view of the age of the sandstone should be
accredited to his assistants, Messrs. Foster and Hill, and not to himself.

Mr. James T. Hodge $ seems to regard the veins as filled by igneous
injection and sublimation. The silver was injected after the copper
had cooled and occupied the spaces left by the contraction of the latter
on cooling.

Dr. Charles T. Jackson ‘in his report (pp. 392, 398, 399, 471 -473),§
transmitted November 10th, 1849, stated that the suites was
formed by ‘the interfusion of the red sandstone and trap,” and the
trap rocks are distinctly stated to have burst through and between the
strata of the pre-existing sandstone. He calls attention to the mooted
question whether the trap rocks originated froran the molten interior of
the earth, or were derived from the re-fusion of the lower stratified rocks
(p. 397). The sandstone and conglomerate are said to have been de-
rived from granite, gneiss, or mica slate and porphyry. The porphyry
is thought to have resulted “ from the semifusion of the finer materials
of the sandstone. It is‘evident at once, from inspection of the pebbles

* Senate Documents, Ist’Sess., 30th Cong., 1847-48, VII., Doc. 57, 134 pp.

+ Proce. Bost. Soc. Nat. Hist., IIl. 76, 77, Nov. 1st, 1848.

{ Proc. Am. Assoc. Ady. Sei., Aug. 20th, 1849, II. 301-308.

§ Senate Documents, 1849-50, III. 371-935. See also Proc. Am. Ass. Adv. Sci.,

II., 1849, Aug. 20, pp. 283-301; Bull. Geol. Soc. France, (2,) Vol. VII., 1849 — 50,
pp. 667-673, and Am. Jour. Sei., (2,) Vol. X., 1850, pp. 65-77.

MUSEUM OF COMPARATIVE ZOOLOGY. 85

of the conglomerate, that they have been ground into their present
shape by long attrition under water, or upon some ancient shore.

. They originated from some nether rock, or were transported
to their present location by drift agencies.” Dr. Jackson will then
stand next in order of time to Rev. J. G. Cumming in suggesting the
idea of drift agencies in the earlier geological periods.* May we sug-
gest that these conglomerates are the lateral moraines of the ancient
glaciers which scooped out the basin of Lake Superior, and that the
coldness of the waters at the time of the melting of these glaciers pre-
vented the existence of lifethen. In this way we account for the Lake
basin, the conglomerates, and the absence of fossils, three difficult prob-
lems. As we now know the geological structure of the country to be dif-
ferent from that supposed by Dr. Jackson, there exists an excellent field
here for speculation concerning the number of glacial periods during
the time of the deposition of the rocks of Keweenaw Point, the con-
nection of glaciers with volcanic action and the eccentricity of the
earth’s orbit. It is very probable that the ice by its weight carried the
sedimentary strata downwards, the same pressure aiding in their igneo-
aqueous fusion (solution), while the thickness of the ice mass would
cause the geothermal couches to rise, thus enabling us to account for
the lavas. This leads us to the consideration of the effect that glaciers
may have in forming lake bottoms by their pressure bending the under-
lying strata, the displaced material being erupted along the sides of the
depression. We can thus account for the proximity of volcanoes to
large bodies of water, and explain the cause of the highest mountains
being adjacent to the deepest oceans, their successive elevations cor-
responding to the different glacial epochs. If the Atlantic is to be
filled with a solid mass of ice to account for the loess of the Rhine, and
the Southern oceans to be filled in like manner to explain the geographi-
cal distribution of the New Zealand fauna, why cannot Lake Superior
also be filled, when it will cost so little and explain so much?

Dr. Jackson further considers the sandstone as belonging to the New
Red, stating that it has been absolutely proved not to be Potsdam. He
seems to have receded from his former views regarding the filling of the
fissures by vein material and not to have adopted any others in their
places. He would, however, consider that the copper and silver ‘“ were
produced by igneous agency... .. The copper and silver occur on

* History of the Isle of Man, 1848, p. 89. See also F. B. Hough, Proc. Am.

Assoc. Adv. Sci., 1851, VI. 262-264; and the Quart. Jour. Geol. Soc., VI. 96, 97,
1850, R. Godwin Austin ; XI. 185-205, 1855, A. C. Ramsay.

86 BULLETIN OF THE

Lake Superior mineral lands in the trap rocks only, and the valuable
veins are limited to a narrow belt of the amygdaloidal variety of that
rock.” (/.¢., p. 471.) Mr. J. W. Foster (May 26, 1849, /. ¢., pp..773 -
785) regarded the sandstone ‘as resting at the base of all the fossil-
iferous rocks.”
In Foster and Whitney’s Report to the Land-Office (J. c., p. 607), it
is stated that “‘ what is generally known as the trap range, consists of a
belt of igneous rocks, composed for the most part of hornblende and
felspar, which in places have broken through the sandstones, tilting them
up at high angles; but oftener are found in alternating beds, having
the same dip as the detrital rocks. The associated sandstone and con-
glomerate belong to the silurian system, and rest at the base of all
fossiliferous rocks.” Concerning the copper it is stated: “Some of these
accumulations of copper are mere beds, the result of segregation, while
others are contained in fissures, formed subsequent to the containing
rock, and associated with a veinstone entirely dissimilar.” (J. c., p. 608.)
The final report of Messrs. Foster and Whitney on the Copper Lands
was presented April 15, 1850.* Regarding the trap range of Keweenaw
Point, it is stated that “this range does not appear to have been the re-
sult of one, but of successive overflows ; for we not only find the igneous
materials arranged in parallel bands, and exhibiting great diversity in
external characters, but we also find numerous intercalations of con-
glomerate of inconsiderable thickness, but extending for miles in a linear
direction — these mixed products being associated in regular beds, having
a common bearing and inclination, so that the inexperienced observer is
inclined to refer the whole to a common origin. This deception is still
further increased by observing lines of pseudo stratification in the trap
conforming to those of the associated sedimentary rocks.” (0. ¢., p. 61.)
The southern trap range of the Point is said to consist of “a vast
crystalline mass, forming an anticlinal axis, flanked on the north by the
bedded trap and conglomerate, and on the south by conglomerate and
sandstone.” (J. c., p. 64.) Towards Portage Lake none of this trap
was protruded, but it was thought that the same fissure extended along
this line from the “head of Keweenaw Point to the western limits of
the district.” (/.¢., p. 68.) Regarding the relations of the sandstone to
the trap on Keweenaw Point and Isle Royale, they say: ‘As a general
observation, the wpper portions of these sandstone belts are much
more changed by heat than the lower.” (/. ¢., p. 63.) ‘‘The upper por-
tions of the sheets of trap are highly vesicular, resembling pumice.

* Executive Documents, 1st Sess., 31st Cong., 1849-50, IX., Doc. 69, 224 pp.

MUSEUM OF COMPARATIVE ZOOLOGY. 87

Fragments of amygdaloid, sometimes rounded, at others angular, are
found enclosed in the pumice-like trap, as though they had become
detached and afterwards reunited to the mass, while in a molten state.
Numerous short and irregular fissures, extending to no great depth, are
observed on the upper surface of the trap, in which sandstone has been
deposited... . . Between the sandstone above and the trap below, it is ex-
tremely difficult to determine where the one begins, and the other ends.
Fragments of amygdaloid, angular or partly rounded, are included
in the sandstone — more numerous near the base than at the top of the
deposits. Where the sandstone is imposed on the trap, there is little
evidence of its having been metamorphosed ; but, on the other hand,
where the trap rests oz the sandstone, the line of junction is clear and
well defined. The trap is less vesicular ; and the upper portion of the
sandstone belt, for the distance of three or four feet, is converted into a
ribbon jasper, having a compact texture. These phenomena have been
observed at numerous places both on Isle Royale and Keweenaw Point.
The beds of sandstone are not shattered, nor does the igneous rock pene-
trate in the form of dikes or ramifying veins. All the phenomena indicate
that the igneous rocks were not protruded in the form of dikes between
the strata, but that they flowed like lava sheets over the pre-existing
surface ; and that the sand was deposited in the fissures and depressions
of the igneous belt, in some cases while the mass was in an incandescent
state.” (l.c., p. 87.) The conglomerate is regarded as a volcanic tuff,
and the sandstone as Potsdam in age. The conglomerate of Keweenaw
Point and Isle Royale “consists of rounded pebbles of trap, almost in-
variably of the variety known as amygdaloid, derived probably from the
contemporaneous lavas, and rounded fragments of a jaspery rock which
may have been a metamorphosed sandstone, the whole cemented by a
dark-red iron sand. This cement may be regarded as a mixture of vol-
canic ash and arenaceous particles, the latter having been derived from
the sandstone then in the progress of accumulation. . ... The trap-
pean pebbles often attain a magnitude of eighteen inches in diameter.
Their surfaces do not present that smooth, polished appearance which
results from the attrition of water... .. The conglomerate appears
to have been formed too rapidly to suppose that the masses were
detached and rounded by the action of waves and currents, and
deposited with silt and sand on the floor of the ancient ocean ; for,
while the contemporaneous sandstone remote from the line of volcanic
foci does not exceed three hundred or four hundred feet in thickness,
the united thickness of the conglomerate bands in the vicinity of the

88 BULLETIN OF THE

trappean range on Keweenaw Point exceeds five thousand feet. As we
recede for a few miles from the line of the volcanic fissure, these amyg-
daloid pebbles disappear, and are replaced by arenaceous and argil-
Jaceous particles.” (/. c, pp. 99, 100.) ‘ Although the conglomerate
attains a thickness of five thousand feet, yet it by no means follows that
the ancient sea in which it was deposited extended to that depth. Ripple-
marks and clay-cracks have been observed in the upper portions of this
group ; the one indicates comparatively shoal water, and the other the —
ebbing and flowing of a tide, or a change in the level of the water. The
inference, therefore, is, that during the deposition of the conglomerate,
the bed of the sea was subject to repeated elevations and depressions,
caused by volcanic action, and that its water obeyed the same tidal laws
which govern the existing oceans. These conglomerates, then, may be
regarded as local deposites formed along the courses of the volcanic
fissures by the joint agency of fire and water. When the former causes
operated with intensity, the materials consisted of spherical masses of
lava and scorize. When they acted feebly, or were quiescent, the ma-
terials became argillaceous or arenaceous.” (/. ¢., p. 109.) “We have
seen that, during the deposition of the sandstone, numerous sheets of
trap were ejected, and flowed like lava-streams ; and that the igneous
and aqueous products were so intermingled as to present the appearance
of having been derived from a common origin; and that subsequently
the unbedded trap broke through these parallel fissures, lifting up the
sandstones, conglomerates, and bedded traps, and causing the whole
mass to dip at high angles.” (/. ¢., p. 110.) The sandstone on both
sides of Keweenaw Point, and the trap, were regarded as making one
geological formation.

While the sandstone is stated to dip near the southern range of trap
above Béte Grise Bay 78° southeast (/. ¢., p. 112), farther up Keweenaw
Bay the prevailing dip was said to be about 5° to the northwest (/. c.,
p. 116). The veins were regarded as probably filled by materials ‘‘ once
held in aqueous solution and precipitated by electro-chemical agency,”
while the theories of sublimation and injection were controverted (/. ¢.,
pp- 174, 175). The veins were fully described so far as then known, as
well as the order of deposition of the minerals and associated copper,
etc., etc.*

Prof. Louis Agassiz, in discussing the “ Geological Relations of the

* See also Bull. Geol. Soc. France, (2,) VII. 1850-51, pp. 89-100; Proc. Am.

Assoc. Ady. Sci., 1851, V. 22-88, 186-151; and Am. Jour. Sci., (2,) 1851, XII.
222 - 239. %

MUSEUM OF COMPARATIVE ZOOLOGY. 89

various Copper Deposits of Lake Superior,” * wrote concerning the copper
ores: “They seem to me clearly to indicate that the native copper is
all plutonic ; that its larger masses were thrown up in a melted state ;
and that from the main fissure through which they have found their
way, they spread in smaller injections to considerable distances ; but
upon the larger masses in the central focus, the surrounding rocks
could have little influence. New chemical combinations could hardly
be formed between so compact masses, presenting, in comparison with
their bulk, a small surface for contact with other mineral substances
capable of being chemically combined with the copper. But where,
at a distance, the mass was diffused in smaller proportions into innumer-
able minute fissures, and thus presented a comparatively large surface
of contact with the surrounding rocks, there the most diversified com-
binations could be formed, and thus the various ores appear in this char-
acteristic distribution. The relations which these ores bear to the rocks
in which they are contained, sustain fully this view, and even the cir-
cumstance that the black oxide is found in the vicinity of the main
masses, when the sulphurets and carbonates occur at greater distances
from them, would show that this ore is the result of the oxidation of
some portion of the large metallic masses exposed more directly to the
influence of oxygen in the process of cooling. Indeed, the phenomena
respecting the distribution of the copper about Lake Superior, in all
their natural relations, answer so fully to this view, that the whole pro-
cess might easily be reproduced artificially on a small scale ; and it ap-
pears strange to me that so many doubts can still be expressed respecting
the origin of the copper about Lake Superior, and that this great feature
of the distribution of its various ores should have been so totally over-
looked.” '

Prof. J. D. Dana remarked : “ The copper occurs in trap or sandstone,
near the junction of these two rocks, and has probably been produced
through the reduction of copper ores by the heat of the trap when first
thrown up.” f— This view is retained in his later editions of the same
work. t ;

Dr. C. T. Jackson later advocated his former view that the sandstone
of Keweenaw Point was of the same age as the New Red sandstone of
Europe, but in addition he claimed that this sandstone (New Red) was

* Lake Superior: its Physical Character, Vegetation, and Animals, (Boston,
March, 1850,) pp. 427, 428.

T System of Mineralogy, 3d ed., May, 1850, p. 508.

$ 4th ed., 1854, Part II. p. 17; 5th ed., 1868, p. 15.

90 BULLETIN OF THE

t

a member of the Upper Silurian.* Later, Mr. Jules Marcou advocated
the view that this sandstone was of the age of the New Red, and opposed
the ideas of Messrs. Foster and Whitney.f— At the meeting of the Brit-
ish Association for the Advancement of Science, July, 1851, Sir W. E.
Logan ¢ advanced the idea that the sandstone and its associated traps .
were older than the Potsdam, and of Cambrian age. This view was
based on the idea that the azoic rocks north of Lake Huron were the same
as the traps of Keweenaw Point.§ Dr. D. D. Owen, as mentioned before,
in his ‘Geological Survey of Wisconsin, Iowa, and Minnesota” (pp. 187-
196) regarded the sandstone as of the same age as the Potsdam of Wis-
consin, but Col. Chas. Whittlesey (Ibid., pp. 459-461) was inclined
to think it was older. Dr. J. J. Bigsby || believed the sandstone to be
Cambrian (or Silurian). Later, Dr. C. T. Jackson advocated the igneous
origin of the calcite veins in this region. Mr. Jules Marcou, in his
“ Geological Map of the United States, with Text,” held that the sand-
stone was of the age of the New Red, and apparently regards the trap as
having been injected in the form of dikes. The copper veins were also
thought to be dikes, with the copper of like igneous origin. This work
gave rise to a long controversy, in which the age of the sandstone was
quite thoroughly discussed ; but in only a few cases shall we refer to the
various articles elicited by it. Those interested in the literature of the
Marcou- Anon.- Agassiz - Barrande - Blake - Dana - Hall- Hunt - Logan - Mur-
chison-Whitney controversy will find the principal articles, that have
any bearing on the geology of Lake Superior, given under the names of
the different authors in the list of articles at the end of this paper.

The same views regarding this district that were given in Messrs.
Foster and Whitney’s Report on the Copper Lands were again pre-
sented in brief in Professor Whitney's ‘‘ Metallic Wealth of the United
States.” * * Dec. 5th, 1855, Dr. Jackson explained the deposition of
the copper in the veins ‘as the result of the chemical action of
protoxide of iron in the trap-rock, which decomposed the vapor of
chloride of copper, as it rushed from the interior of the earth through
the crevices ; if, as is probable, these wonderful native copper lodes, are

* Proc. Bost. Soc. Nat. Hist., Oct. 2 and 16, 1850, III. 335-339. See also Bull.
Soe. Geol. France, (2,) 1849-50, VII. 209, Elie de Beaumont.

+ Bull. Soe. Geol. France, 1850-51, (25) VIII. 101 - 105.

t Trans. of the Sections, pp. 59 — 62.

§ See Am. Jour. Sci., (2,) 1857, XXIII. 305-314.

|| Edinburgh New Phil. Jour., 1852, LIIT. 55-62.

§ Proc. Bost. Soc. Nat. Hist., 1853, 1V. 308, 309.
** Philadelphia, 1854, pp. 247-305. Am, Jour. Sei., (2,) 1857, XXIII. 305-314.

MUSEUM OF COMPARATIVE ZOOLOGY. 91

the products of sublimation and of galvanic segregation of the metal
from vapor.” He defined the ash bed as a ‘“‘ comparatively soft scoria, or
rotten amygdaloid, formed by the mixture of molten trap-rock and fine
sandstone, which have been, as it were, melted together into a very
spongy kind of scoria, the aqueous vapor having rendered it remarkably
vesicular.” * He regarded the trap as having been “ poured out, at dif-
ferent times, through a fissure, and spread over the materials of the
sandstone and conglomerate at the bottom of the sea, thus producing
alternating beds of these rocks,” while in July, 1856, he seems to have
regarded the trap as forming dikes in the sandstone, and combining with
its ingredients to form the zeolites.— Prof. L. E. Rivot ¢ regarded the
traps as interstratified sedimentary beds metamorphosed in situ. The
sandstone formed the upper portion of, and was conformable with,
the copper series ; all to the Sault St. Marie making one geological
horizon, including the granites and iron-bearing rocks. All were taken
to be of the Potsdam age. The veins were considered to have been pro-
duced by elevation and fracture since the deposition of the entire series,
and the copper deposited in the wet way.

In 1856 a “ Report on the Exploration of Lakes Superior and Huron,”
was presented to the Legislative Assembly of Canada by Count de
Rottermund. It probably proved satisfactory, as we do not learn that
the Assembly asked for any further information from him. In the nar-
rative portion we are informed: “I procured a boat with four hands
and proceeded to Portlock Harbour. . . . I met Mr. Salter with whom
I returned to the Bruce Mines. There we parted our provisions and
separated.” (J. c., p. 1.)

He attempts a classification of the formations visited, and states that
“this classification demands great attention, and very minute discrimi-
nation, to avoid the solecism of giving names according to individual
fancy, not used in the scientific world. Such are the names applied to
formations in Canada of Huronian, Sillery, Laurentine, Richelieu, pecu-
liar to the localities which they indicate, substituted for Jurassic, Car-
boniferous, Cambrian, Devonian, ete., which are so well classified, defined,
and admitted throughout the scientific world.” (/. ¢., pp. 4,5.)

His theory of the origin of the copper is too lengthy for insertion ; it
must be read to be appreciated. The result is summed up as follows :
“On Lake Superior the copper, in its native state is due to the de-

* Proc. Bost. Soc. Nat. Hist., 1855, V. 279 — 281; 1859, VII. 31.
te bide, 1V Ie. 23,24°
$ Annales des Mines, (5,) 1855, VII. 173 - 328 ; 1856, X. 864-474.

92 BULLETIN OF THE

posit of certain species of organic matters which have a tendency to
increase the electro-chemical action, and which decomposed the sulphu-
rets, oxides, etc., which the abundant deposit of matter containing traces
of tale serpentine and chlorites, has brought together or concentrated
in a certain limited space. For nearly all the rocks contain in the
crystalline cleavage, and also in the veins these matters which appear
sometimes to be a sort of cementation, if, indeed, it be not the state
of combination of detritus, of disintegration of primitive rocks which
have arrived at the state of sandstone and greywacke.” (J. ¢., p. 13.)

This report is not without interest to the archeologist as the follow-
ing proves: ‘I have in my possession locks of hair enveloped in copper,
which the natives carried about them as marks of their bravery. When-
ever they killed their enemy they used to cut off a lock of hair and carry
it about them as a species of decoration. In places where there is no
copper they cut off with the hair a small portion of the skin, which is
called the scalp.” (/. ¢., p. 16.)

The student of Indian customs can, of course, now greatly aid the
miner in his prospecting, if he will carefully map the districts inhabited
by the non-scalping, copper-bearing Indians, for hereafter it will be of
no avail to look for copper outside of their habitat.

Alb. Miller, in 1856, published a paper relating to the copper of this
district.* His facts were taken mostly from the report of Foster and
Whitney, and it is unnecessary to repeat them here. He regarded the
copper as being deposited in the wet way, by the aid of galvanism, and
reduced by organic matter and the oxide of iron. The copper, it is sup-
posed, might have existed in the trap and its minerals, in minute
amounts, until brought to the points where it is now found. The stn-
dent interested in the origin and deposition of the copper will do well
to read the writings of Foster and Whitney, Whitney, Miiller, Bauerman,
and, lastly, those of Marvine and Pumpelly.

Principal J. W. Dawson remarks ¢ concerning the deposition of the
native copper: ‘The whole of the appearances indicate that the depo-
sition of copper belongs to the period of aqueous infiltration, by which
the veins and vesicles were filled after the consolidation of the trap ;
and the copper, like the cale spar and zeolites, occurs both in true veins
and in the cavities of beds of vesicular trap and tufa. Its deposition
must, therefore, be explained, not by igneous causes, but by electro-

* Verhandlungen der Naturforschenden Gesellschaft in Basel, 1854-57, pp.
411 - 438.
t Feb. 10, 1857. Canadian Nat. and Geol., II, 1-12.

MUSEUM OF COMPARATIVE ZOOLOGY. 93

chemical agencies, decomposing some soluble salt, most probably the
sulphate, of copper. Such changes may have been aided by the remain-
ing heat of portions of the volcanic masses, by the presence in them of
large quantities of iron in low states of oxidation, and by the further
oxidation of that metal evidenced in the red jasper and red laumonite
of the veins, and the red conglomerate and sandstone associated with
the trap..... The main fact in relation to the origin of the metallic cop-
per, is that it is a product, not of the fusion of the trap, but of subse-
quent processes, by which the fissures of that rock were filled by mate-
rials regarded as of aqueous origin.” (/. ¢., pp. 8, 9.)

In 1857, Dr. J. D. Dana* stated that the veins occur “ mostly in the
trap rock which intersects a red sandstone, probably identical in age
with the red sandstone of Connecticut and New Jersey.” April 6, 1859,
Dr. Jackson inclined to the view that the zeolites had been formed
‘under the heat of the trap rocks, and the influence of heated saline
waters.” t+ Prof. James Hall, in his Paleontology of New York, says :
“In the region of Lake Superior, the sandstone, of the age of the Pots-
dam sandstone, has accumulated to a degree unparalleled in any other
known locality of that rock. In this region there are not only massive
accumulations of trappean matter, but outflows which have spread over
the strata during their deposition; the beds of stratified amygdaloid
trap alternating with the shale and sandstone, often equalling or exceed-
ing the sedimentary matter.”

In 1861, Dr. T. Sterry Hunt, following Logan, referred the sandstone
with its accompanying trap to the Quebec group.§ Prior to this, || Prof.
W. B. Rogers supported the view that this sandstone was of Potsdam
age, and was opposed in this by Dr. Jackson.

In his Manual of Geology,{] Dr. Dana refers the sandstone partly to
the Potsdam and partly to the Calciferous epoch. In the edition of
1874, it is regarded as Calciferous. Dr. Dana further remarks concern-
ing the copper, that “the native copper of the Lake Superior region is
intimately connected in origin with the history of the trap and sandstone.
The copper occurs in irregular veins in both of these rocks near their
junction ; and whenever the trap was thrown out as a melted rock, the

* Man. of Min., 2d ed., p. 305.

f Proc. Bost. Soc. Nat. Hist., 1859, VII. 45-47.

t Vol. IIL. p. 79, 1859.

§ Am. Jour. Sci., (2,)®1861, XXXI. 216-220, 392-414; 1862, XXXIII. 320-
327. Canadian Nat. and Geol., 1861, VI. 81-105, 199-207.

|| Proc. Bost. Soc. Nat. Hist., Nov. 17, 1860, VII. 394-399.
{7 1862, pp. 172-174.

94 BULLETIN OF THE

copper probably came up, having apparently been derived from copper-
ores in some inferior Azoic rocks through which the liquid trap passed
on its way upward. The extent to which the rock and its cavities are
penetrated and filled with copper shows that the metal must have been
introduced by some process before the rock had cooled.” * ;

In the Geology of Canada, 1863, the copper-bearing rocks are con-
sidered, by Sir W. E. Logan, to be of the Calciferous and Potsdam
formations, but overlaid by the Eastern sandstone, which was regarded
as Chazy (pp. 67-86). Dr. Hunt seems to regard the ‘‘ash-bed” of
Copper Falls as a conglomerate, and further says, regarding the Port-
age Lake deposits: ‘‘Certain of the sedimentary beds thus impregnated
with native copper, are often designated as volcanic tufa or volcanic
ash. From whatever source derived, however, the amygdaloidal rocks
were deposited from water; and the copper which is disseminated in
them, as well as in the sandstones and conglomerates, was separated by
chemical processes from aqueous solutions, either contemporaneously
or by subsequent infiltration. There appears to be no doubt that the
traps which are interstratified with the sandstones and amygdaloids of
this region, are eruptive rocks; and the sedimentary material of which
the amygdaloids and tufas are composed may perhaps have been, to a
greater or less extent, erupted in the form of volcanic mud, as many
geologists suppose. This origin of the sediment has probably, however,
no connection with the source of the copper.” (pp. 698, 699.) He
takes the entire formation, as before, to belong to the Quebec group.

In 1866, Mr. Thomas Macfarlane regarded the rocks at Portage Lake
as melaphyrs.t In 1868 (/. c., p. 256), he appears to regard the sand-
stone as being of the Permian age, basing his conclusions upon the litho-
logical characters of the melaphyrs, while those who had regarded it as
Triassic have based their views upon the lithological characters of the
sandstone. One method is about as valuable as the other, a flow of
basalt lava or a deposit of sand not being apt to be dated per se. Colonel
Whittlesey, in describing the continuation of this formation in Wiscon-
sin, makes the copper-bearing trap a formation below, but conformable
with the Potsdam sandstone.t Mr. H. Bauerman§ suggests, besides the
hypothesis of Miller, the following to account for the occurrence of the

* Edition of 1862, p. 195; see also edition of 1874, p. 186.

t Geology of Canada, 1866, pp. 149-164. Canadian Nat. and Geol., (2,) III.
1-18.

+ Proc. Am. Assoc. Adv. Sci., 1867, XVI. 97-107.

§ Quart. Jour. Geol. Soc., 1866, XII. 448 - 463.

MUSEUM OF COMPARATIVE ZOOLOGY. 95

copper: ‘The presence of copper in the sandstones suggests another
origin — namely, that it may have originally been deposited with the
quartz-ore sediment as a finely divided sulphide from sea-water under
the influence of organic matter, and by subsequent oxidation and solu-
tion have been removed and collected in the rocks below. .... The size
of the accumulated masses of metal appears to be mainly dependent
upon the size gf the cavities in which they are deposited, whether in
the amygdaloids or in the main fissures ; and their absence in the com-
pact traps is probably only due to the non-occurrence of such cavities.
In almost all cases the introduction of the metal has been preceded
by the deposit of minerals produced from the decomposition of the
rock, such as quartz, calcite, chlorite, and zeolite; and in the larger
cavities it is often followed by transparent crystals of calcite, which are
formed over branching masses of copper, or even show sigus of simulta-
neous deposition, being filled with fire-spangles of metal arranged par-
allel to the diagonal striations or lines of growth on the rhombohedra.
Similar alternations in the formation of zeolites, more particularly
analcime, have been described by Whitney.” He is inclined to regard
the deposition of the copper in the amygdaloids as having taken place
prior to the filling of the veins, the former serving as feeders to the
latter. (/.¢., pp. 460, 461.)

In a paper read before the Boston Society of Natural History, June
5, 1867,* Mr. Alexander Agassiz remarks: ‘Foster and Whitney, in
their Report of the Lake Superior mineral district, represent the sand-
stone on the south side of the trap range of Keweenaw Point as dip-
ping south and resting conformably upon the beds of trap of the north
side of the anticlinal axis of Keweenaw Point. This anticlinal axis
formed by the Bohemian Mountain, as asserted by Foster and Whit-
ney, is not found further south as far as I have had occasion to examine.
In two of the ravines cut through the sandstone by creeks flowing in
an easterly direction from the crest of the range towards Torch River,
near the head of Torch Lake, we find good exposures of the sandstone
resting unconformably upon the trap which has still the same northern
dip as further west, of about 42°. The sandstone within a distance
of one hundred feet from the trap, dipping north 42°, lies horizontally,
or rather has at the ontside an inclination of 13° or 2° south.” At the
falls of the Douglass Houghton Creek, he says: ‘The creek winds its
way through a deep ravine cut out of the sandstone, and at the junction
of the sandstone and trap, falls a depth of one hundred and seventy-

* Proceedings, XI, 244-247,

96 BULLETIN OF THE

two feet. The chloritic bed is well developed on the south side of
the creek, while the north side is more greenstone, and all along the
whole length of the ravine up to the falls, a distance of one and one-
half miles, the horizontal beds of sandstone are readily traced, dipping
slightly north near the falls, and being horizontal at the opening of the
ravine into Torch River valley, plainly showing that they rest uncon-
formably upon the trap range. On examining this gsandstone more
carefully, we find that the strata are made up of alternating layers of
sandstone of reddish or yellowish grain, and of beds of loose sandstone
containing boulders; some of the beds of boulders resembling what is
common on sea-shores as a mixture of mud and shingle. On breaking
open several of the small boulders taken iz situ from the beds we find
that they consist mostly of reddish trap, but frequently we come across
perfectly well water-worn boulders of grayish trap containing amygdales,
identical with the trap of the copper range a short distance west from
these beds of sandstone, plainly showing that the sandstone was depos-
ited upon the shores of the ridge of trap forming Keweenaw Point, and
has not been uplifted by it as is stated by Foster and Whitney. The
case is totally different with the sandstone north of the range that lies
conformably upon the trap, but the sandstone of the southern side of
the mineral range in the vicinity of Torch Lake is plainly of a different
age, lying, as it does, unconformably upon the former.”

In some respects it would seem that Mr. Agassiz, in common with
many geologists, had misunderstood the views of Messrs. Foster and
Whitney. Their idea was that the traps and sandstone comprised the
same formation. The present visible portion of the eastern sandstone
had, like the western one, been laid down since the trappean overflows.

After the deposition of the entire series a fissure was formed running
along the Point from its head to the western limits of the district. This
was attended in the northeastern portion by the protrusion of trap
forming the Bohemian Mountains, but towards Portage Lake the fissur-
ing was accompanied only by the elevation of the sandstone and trap
west of the line, while that east of it remained nearly horizontal. As no
stratified rock can rest conformably on the intrusive mass which uplifts
it, so the sandstone was not supposed to rest conformably on the Bohe-
mian trap. They also did not in their final report regard the sandstone
along this fissure at the Douglass Houghton fall as dipping southerly,
although Mr. Foster had stated so in a previous report to Dr. Jackson.*
That Messrs. Foster and Whitney had this idea was probably inferred

* Senate Doc., 1849 — 50, III. 783.

MUSEUM OF COMPARATIVE ZOOLOGY. 97

from the fact that the printer placed the eastern side of their section on
the left hand, as was also done with that of the Copper Falls mine.*
Their idea then would be perfectly consonant with the presence of
trappean pebbles in the eastern sandstone as well as in the western, only
they would have been deposited prior to the faulting, instead of after its
as Mr. Agassiz’s view would demand.

Mr. Robert Bellt regards the Upper Copper-bearing rocks as being of
Permian or Triassic age. This conclusion was based on the lithologi-
cal characters, and was objected to by Sir Wm. Logan in the same
report (pp. 472-475). -

Prof. R. Pumpelly in 1871 published a paper on “The Paragene-
sis and Derivation of Copper and its Associates on Lake Superior,” $ a
subject which had been treated of before by Messrs. Whitney, Miiller,
and Bauerman. He remarks: “The eastern limit of the ‘range’ is
formed by a strongly marked and generally vertical plane of demarka-
tion between the highly inclined cupriferous series of rocks and the
sandstones which slope gently to the S. E. This sudden break is con-
sidered, with probably the best of reasons, by Foster and Whitney, and
afterwards by Rivot, to be a longitudinal fracture accompanied by a dis-
location of at least several thousand feet. Foster and Whitney looked
upon the sandstone as the equivalent of the Potsdam, while the Geol-
ogists of the Canadian Survey refer it to the Chazy, and both authorities
agree in considering it to be younger than the cupriferous rock, and of
the same age as the sandstone beds, which are conformably superim-
posed over the trappean series on the west side of Keweenaw Point.”

Prof. Pumpelly, it would seem, believed that the copper was de-
posited in the places in which it is now found by being precipitated
from solution through the agency of protoxide of iron. He further
considered that the copper was derived by concentration from the sedi-
mentary members of the series. He remarks that “it is still an open
question whether the trap which formed the parent rock of the mela-
phyr was an eruptive or a purely metamorphic rock. If it was erup-
tive, it was spread over the bottom of the sea in beds of great regularity,
and with intervals which were occupied by the deposition of the beds
of conglomerate and sandstones.” (/. c., p. 352.) The general tenor of
this and his other papers shows that at this time, and for some years
afterward, he leaned strongly towards the theory of the sedimentary

* Copper Lands, pp. 63, 68.

t Geology of Canada, 1866-69, p. 321.

¢ Am. Jour. Sci., (3,) II. 188-198, 243 - 258, 347-355.
VOL. VII.—NO. 1. 7

98 BULLETIN OF THE

origin of the entire trappean series. At this time he also regarded
the traps, with all the sandstone as far east as at least the Pictured
Rocks, as belonging to the Quebec group. It will be seen that he
afterwards abandoned these views.

Later, Prof. Pumpelly in conjunction with Major T. B. Brooks pub- .
lished a paper entitled, “‘On the Age of the Copper-bearing Rocks of
Lake Superior.” * They state that their observations ‘ demonstrate a
wide difference in age between the Cupriferous series of sandstones, con-
glomerates, and melaphyres on the one hand, and the Lower Silurian
sandstone, with which they have generally been considered as nearly
identical in age, on the other.” At the western edge of the eastern
sandstone on Keweenaw Point “its nearly horozontal strata abut against
the steep face of a wall formed by the upturned edge of beds of the
Cupriferous series of melaphyre and conglomerate, which dip away from
the sandstone at angles of 40°-—60°, according to geographical position.
This sharply defined and often nearly vertical plane of contact, having
been seen by the earlier geologists at several points along a distance of
many miles, and having been found to be often oceupied by a thick bed
of chloritic fluecan, which was looked upon as the product of faulting
motion, was considered as a dislocation. This idea seemed to gain cor-
roboration in the fact that, on the western side of Keweenaw Point, sand-
stones bearing considerable resemblance to those of the eastern horizontal
beds occur, apparently conformably overlying the Cupriferous series.
Both sandstones came to be considered as identical in age, and as form-
ing the upper member of the group. There were many circumstances
which made it difficult for us to accept this conclusion. One obstacle
lay in the enormous amount of dislocation required ; for imstance, at
Portage Lake, where the strata of the Cupriferous series, with an actual
thickness of several miles, dip away from the supposed longitudinal fault
at an angle of about 60°.” The Cupriferous series is regarded by them
as conformable to the Huronian, while the line of fault is taken to be an
old shore cliff, with the sandstone deposited against its base. They also
state that it would be difficult to account for the absence of this series
in localities eighteen miles from where they were found miles in thick-
ness, unless they represented a sinking area along whose shores the Silu-
rian sandstone was deposited. They also claim that this series was worn
through near Lake Gogebic, and the Silurian sandstone deposited in the
trough. It is to be noticed that according to them the Cupriferous
series are four miles distant from the locality in which the Silurian

* Am. Jour. Sci., (3,) III. 428 - 432, 1872.

MUSEUM OF COMPARATIVE ZOOLOGY. 99

sandstone is said to have been seen. ‘Their geological reasoning could
only hold good in a region where uncontorted sedimentary rocks alone
occur; therefore we are justified in believing that at this time both
Pumpelly and Brooks regarded the copper-bearing traps as metamor-
phosed sedimentary rocks. We are not aware that the latter has ever
changed his views.

In 1873, Dr. T. Sterry Hunt* used the term Keweenian group in
speaking of the copper-bearing rocks, and suggests that perhaps the
copper may have been derived from the oxidation of copper ores in the
Huronian schists, while the dissolved metal accumulated in the basins
at their base, — a view almost identical with that announced by Shepard
twenty-eight years before. ‘‘We may here remark that the late re-
searches of Messrs. Brooks and Pumpelly seem to establish that the
great copper-bearing series of Keweenaw occupies a place between the
Huronian schists and the nearly horizontal red and white sandstone of
the region which is itself below the Trenton limestone. In all this they
have confirmed the previous conclusions of Houghton, Whitney, Hall,
and Logan.” It may be remarked here, also, that if Prof. Whitney’s
writings have taught anything, it is that the sandstone from Sault St.
Marie to the further side of Keweenaw Point, including the copper-
bearing rocks, are one and the same formation; therefore Dr. Hunt’s
statement is incorrect in this particular at least. In proof of this, one
can read his own statement of Prof. Whitney’s ideas on page 79 of the
“Azoic Rocks.” | As we have shown before, Houghton regarded the
copper-bearing rocks as eruptive in, and therefore younger than, the
sandstone of Keweenaw Point, which in 1843 he took as belonging to
the “New Red.” This is the last published statement that we can find
of Houghton’s on this point.

Mr. Brooks, in his Report on the Iron Districts of Lake Superior, } re-
gards it as proved that the copper-bearing rocks are conformable with
the Huronian ; the proof was obtained, not from contacts, but from
their common dip and strike. He also states: “Against and over the
copper series on the north, abut the horizontally bedded lower Silurian
sandstones. .... As the non-conformability of the copper-bearing
rocks and sandstones is doubted by some geologists, it should perhaps
be stated that the actual contact was not seen. But the sandstones were
observed lying horizontal, and affording not the slightest evidence of

* Trans. Am. Inst. Min. Eng., I. 331-342. -

Tt Sec. Geol. Survey of Penn. E, Azoic Rocks, Part I.
¢ Geol. of Mich., I. 184, 185.

100 BULLETIN OF THE

disturbance, within a few miles of highly-tilted copper rocks, which
gave every evidence of having been elevated before the deposition
of the sandstones. So far as my observation has extended, this rule is
general; that is, no Lake Superior sandstone, which is unmistakably
lower Silurian, has ever been found in any position other than nearly
horizontal” ;——-Will Mr. Brooks visit Presque Isle ?— ‘‘and no rock which
was unmistakably of the Copper series has been seen which was not
considerably tilted. The fact that certain sandstones belonging to the
copper series are very similar, if not lithologically identical with some
of the lower Silurian sandstones, has helped to complicate this question.
An interesting locality for study in this connection is the west fork of
the Ontonagon River, just south of the Forrest Copper Mine. J am not
sure but that it affords an exception to the rule above stated, as at that
point sandstones, apparently Silurian, dip south at an angle of 45°.”

In Prof. Pumpelly’s Report of the Survey of the Copper District,*
we find but little written by him of geological interest excepting that
which had been published elsewhere, and referred to in the preceding
pages.t The sandstone beds on the eastern side of Keweenaw Point are
said to slope gently to the southeast (/.c, p.1). The chief portion
of the geological work, and about all of any value, seems to have
been done by Mr. A. R. Marvine, who, judging from his work, appears
to have possessed the power of observing well and accurately in the
field. Only certain portions of his work can be pointed out here:
“The conglomerate beds of Keweenaw Point have been generally con-
sidered as mere local deposits, rapidly fading out in either direction.
The table would seem to show, on the contrary, that for conglomer-
ates they are unusually persistent, and that while a bed may thin
out and lose its character as a conglomerate, it may still exist even
as a mere seam. .... We gather from those facts that when the beds
composing the trappean range were being originally formed, the agen-
cies, whatever they were, which formed what are now the melaphyrs,
ceased to act not only over limited but over extended areas, in one in-
stance at least over fifty (50) miles, and for periods of time long
enough to allow of the accumulation of beds of conglomerate from a few
to over 75 feet —in one instance over half a mile — in thickness.”
(7. c., pp. 60, 61.)

Mr. Marvine points out the fact that much of the amygdaloidal charac-
ter of these rocks is owing to chemical action upon approximately homo-

* Geol. of Mich., Part II., 1873.

+ Am. Jour. Sci., 1872, (3,) II. 188-198, 243-258, 347-355; III. 428 - 482.

MUSEUM OF COMPARATIVE ZOOLOGY. 101

geneous rock long after it was formed, and “ the amygdules which mark
this change were thus slowly developed, and are not the mere fillings of
pre-existing cavities.” Besides this pseudo-amygdaloidal structure true
amygdaloidal structure was also pointed out. Concerning the sedimen-
tary origin of these rocks he remarks: ‘‘ But the strongest proof would
seem to be in the structure of the so-called scoriaceous amygdaloids. In
these, patches or balls of amygdaloidal material are associated, even sur-
rounded by an imperfectly stratified material, which is undistinguishable
from the true fine-grained sandstones. This association is such that it
seems as if it could in no wise be accounted for by metamorphism acting
on sedimentary beds, but only by supposing a peculiar mixture of the
materials at the time of deposition, which mixture is not such as
sediments assume. .... The fact that in sandstones which are in-
tercalated between two trap beds the upper parts, for several inches
from the hanging wall, are often changed as if by heat, while at the
bottom contact there is no such change, cannot be offered as an ob-
jection to the metamorphic theory, for it would be in just such regions
that metamorphism would naturally occur. But the fact that sandstone
material seems to have entered amygdules near the upper part of beds
covered by sandstones; that it may fill a well-defined crack extending
down into an underlying melaphyr, . . . . or that melaphyr may nearly
surround pebbles apparently caught up from an underlying conglom-
erate ....3 these facts, as does the peculiar structure of the scoria-
ceous amygdaloids above noticed, seem to point to a very different origin
for the melaphyrs than a sedimentary one. . . . . As a whole, then, the
structural features of these beds remarkably resemble those of true lavas.
They have been affected, however, and to a very great extent, by meta-
morphism, and this metamorphism has taken place in such a manner,
has so heightened and carried on the original structure, as it were, that
the ordinary proof of their igneous origin, such as contact changes in
adjacent sandstones, presence of amygdules, etc., fail, and it seems nat-
ural to consider this metamorphism as a vera causa for the whole struc-
ture. Certain extraordinary features, however, as noticed above, seem
wholly incompatible with this idea, and when considered as true igneous
rocks in which great and peculiar metamorphism has taken place, all the
phenomena presented seem to be satisfactorily and naturally accounted
for. . . . . These changes, however, have been both very many and very
great ; so great, in fact, that, as seen above, when once examined they
seem almost sufficient to have developed all the peciliarities of the beds
from sedimentary deposits. The practical importance of the recognition

102 BULLETIN OF THE

of this metamorphism and of a proper understanding of its methods and
effects, will be apparent when it is recollected that to it is due all the
economical value the beds possess. The beds as originally formed prob-
ably contained the elements of its minerals, together with its copper and
silver, more or less disseminated through their mass, as much so re-
mains till the present day, or else they were so contained — at least in
part — in overlying rocks, and in this form they could have been of no
economic value; nor could any process taking place at that time have
concentrated the minerals in the manner in which they now occur.” He
opposes the theory that the copper was deposited in its present position
by igneous action.

The metamorphic action is thought to have resulted from the agency
of percolating waters. “‘ All the phenomena tend to prove that it is by
means of some such chemical actions as these, continued through long
periods of time, that the metamorphism of these beds has been effected.
It is such metamorphism which has developed the amygdaloidal mela-
phyrs, formed segregations, modified and filled the veins and amygdules,
placing in them their minerals in the present relative positions ; and, in
the general process, the copper, like the other ingredients, was selected
from its disseminated and therefore useless condition, and concentrated
in veins, amygdaloids, and conglomerates till it reached a percentage of
richness that gives to the deposits an economical importance. This
action has taken place certainly not at a high temperature, and possibly
at a temperature no greater than that of the beds at present, while it
may have been largely aided by that electric action which chemistry
almost always induces, and which is known to be active at the present
day. In fact the presence of the latter is proof that chemical action is
even yet going on.....

“Where observed, the hanging-walls of the sandstones were generally
smooth and gently undulating, but occasionally quite uneven, while the
upper two to twelve inches were somewhat changed, being harder or
softer, or lighter or darker-colored than the mass of the bed... . . The
foot-walls are sometimes smooth and undulating ; the surface of the
underlying bed, when not an amygdaloid, as was sometimes the case,
seeming to have been worn smooth, as if by attrition ; or else the sand-
stone seemed to fill inequalities in the underlying amygdaloid. The
sandstones were not observed to be changed near the foot-wall. In one
remarkable instance, a crack or fissure was observed extending down
into a melaphyr, which was filled by the overlying sandstone. The con-
clusion is inevitable, that the melaphyr had formed, hardened, and
cracked before the sandstone was deposited. ....

MUSEUM OF COMPARATIVE ZOOLOGY. 103

“ The veins of the district were of course formed long after the con-
solidation of the beds, and probably when they were being lifted into
their present position. They have subsequently been filled with the
various minerals which now occupy them, wholly by infiltration and
chemical, probably aided by attendant electric, action, and in a system-
atic and natural sequence.” (/. ¢., pp. 108 — 115.)

Regarding the junctions of the sandstone and amygdaloid in two local-
ities he says: “Junction, very irregular. For two feet the underlying
sandstone is changed and indurated, being, in places, hardly distinguish-
able from the overlying melaphyr, except for enclosed pebbles which are
not changed. Some pebbles rest upon the hanging-wall, which are quite
enclosed in the overlying amygdaloidal melaphyr.... . Junction, slightly
undulating. No change or metamorphism in the adjacent beds. Extend-
ing from the junction down into the underlying melaphyr — about
eight feet being exposed —is a fissure or crack with sharply defined
edges and two abrupt bends, giving widths of two and four inches. This
crack is filled with sandstone similar to that above, but somewhat finer
and slightly decomposed or softened. There is an appearance of irregu-
lar, but rudely curved stratification, about parallel, as a whole, with
the formation.” (/. c., pp. 118, 119.)

It is to be seen, then, that Mr. Marvine arrived at the same con-
clusions regarding the Copper-bearing rocks as did Messrs. Foster and
Whitney, and supported these views by the same evidence that they
had more fully and thoroughly given in their report.

In Part III.* we have the report of Dr. C. Rominger on the Pale-
ozoic Rocks. Regarding the sandstone he says: “ The lower Silurian
age of the Lake Superior sandstone is unequivocally proved by its
stratigraphical position. In its whole extent it is visibly overlaid by
calcareous ledges, containing fossils peculiar to the Calciferous forma-
tion, or, in other cases, by the Trenton limestones. The recognition of
a separate rock-series, identifiable with the Calciferous formation, at
once nullifies the other mentioned opinions of Geologists, and leaves no
choice but to see in the Lake Superior sandstone the equivalent of the
Potsdam sandstone. .... The thickness of the Sandstone formation is
difficult to ascertain. Its lower portions are so intimately connected
with the sandstones and conglomerate beds of the copper-bearing Trap-
pean series, that I could draw only an arbitrary division line between
the two groups, which would swell the thickness of the sandstone group
to many thousand feet, while east of the Copper range, the whole sand-

* Geol. of Mich., I. 1873.

104 BULLETIN OF THE

stone series reposing on the Huronian and Granitic rocks does not ex-
ceed the thickness of 300 feet.” (/. ¢, pp. 80, 81.)

“The sandstones lining the eastern shore of Keewenaw Point extend
approximating to the centre of the Peninsula, retaining their horizontal
position, and also their lithological characters to such a degree that the
different strata can be parallelized without difficulty with those of the
more eastern localities. Near the centre the horizontal sandstone ledges
are found at once abutting against the uplifted edges of a different rock-
series — the Copper-bearing rocks — which form the most elevated central
crest of the Peninsula.” (/.¢., p.95.) “The discordance of the strata
on the east side of the axis of elevation, and their conformability on the
sloping west side, finds its explanation in the hypothesis of a gradual
submarine upheaval of the trap range, in its subsequent rupture, and
the final emergence of the western margin from the water, while the
eastern portion of the fissured earth’s crust remains submerged.” (/. ¢.,
p. 98.)

In 1874, Prof. Roland Irving discusses the question of the age of
the copper-bearing rocks of Wisconsin, which were regarded as iden-
tical with those of Keweenaw Point. He advocates the same views
as those held by Pumpelly and Brooks, and bases his conclusions on
similar grounds. The Laurentian, Huronian, Copper-bearing rocks,
and Lower Silurian sandstones were never seen in direct contact with
one another with one exception. That exception is the junction of a
trap supposed to belong to the Copper-bearing series with the Potsdam
sandstone. The sandstone, he states, is for three hundred feet from the
trap “ broken in every conceivable manner, the misplaced layers dipping
in all directions, and in its immediate vicinity making a sort of brecciated
mass of fragments of trap and sandstone. .... These trappean beds
carry here no intercalated beds of sandstone and conglomerate.” He ob-
jects to the most probable explanation in this case, the protrusion of this
trap through the sandstone, as the trap seems to be unlike the Copper-
bearing rocks, except in the fact that it is an old basalt; but thinks
some deep-seated force shoved the old formation, on whose flanks the
sandstone was deposited, upwards, and so produced this dislocation.*

Concerning the relation of the western sandstones to the eastern and
to the trap rocks in the Ontonagon district, Dr. Rominger says: “ The
age of these beds is intermediate between the trap and the horizontal
sandstone deposits; but between all three of the indicated groups so great

* Am. Jour. Sci., (3,) VIII. 46-56; Trans. Wisc. Acad. Sci., 1873-74, II.
107 -119.

MUSEUM OF COMPARATIVE ZOOLOGY. 105

lithological affinities exist, that it is most natural to consider them as
the consecutive products of one and the same epoch, in the commence-
ment of which the just-formed strata were displaced by volcanic action,
which subsided toward the end and left the last deposits undisturbed.” *

In 1878, Prof. Pumpelly published a paper entitled the ‘ Metaso-
matic Devolopment of the Copper-bearing Rocks of Lake Superior.” f
This is devoted principally to a description of the microscopic characters
of these rocks and their alterations, and, although we differ in nomen-
clature, we regard it as one of the very best papers published upon mi-
croscopical lithology. His geological ideas remain the same, however, as
he states that the greater age of the Keweenaw series over the Potsdam
sandstone is proved by abundant evidence of non-conformability. He
regards them “ more nearly conformable to the underlying highly tilted
Huronian schists. _They are thus the product of the earliest eruption
of basaltic rocks to which a proximately definite age can be assigned.
They were preceded by very extensive eruptions of acid rocks, especially
porphyries. These basaltic rocks have been subjected to a wide-reaching
alteration, which has produced marked changes in the internal condition
of the beds, and has filled the’ fissures with a rich variety of minerals,
whose constituents were derived from the products of this alteration.”
(1. c., pp. 253, 254.) These old basaltic rocks were considered to be
melaphyrs and diabases.

It is to be seen that he now adopts the views of the origin of the
traps held by Messrs. Foster and Whitney, and later by his assistant,
Marvine. The reasons for this radical change of base are not stated:
we have simply the assertion that the traps are basaltic overflows, made
as though no one had ever held a different opinion.

Later, Dr. T. Sterry Hunt says that it seems probable from our pres-
ent state of knowledge that the traps are of volcanic origin. He re-
gards them as unconformable with the Huronian, as he takes the
Copper-bearing rocks as the equivalent of his Taconian. This, of course,
requires the intercalation of his Montalban between them and the
Huronian.t

Dr. J. D. Dana in his Manual of Mineralogy and Lithology,$ says
concerning the occurrence of the native copper with disseminated silver :
“This mixture of copper’ and silver cannot be imitated by art, as the

* Geological Survey of Michigan, 1873-1876, III. 154.

t Proc. Am. Academy, XIIT. 253-309.

¢ Sec. Geol. Survey Penn. E, Azoie Rocks, Part I. p. 236.
§ New York, 1878, p. 131.

106 BULLETIN OF THE

two metals form an alloy when melted together. It is probable that
the separation in the rocks is due to the cooling from fusion being so
extremely gradual as to allow the two metals to solidify separately, at
their respective temperatures of solidification — the trap being an igne-
ous rock, and ages often elapsing, as is well known, during the cooling of
a bed of lava, covered from the air.” We may remark here that Hunt’s
edition of Ure’s Dictionary, 1878, states that the West Canada copper
mines are the most important in America. Such carelessness of state-
ment should hardly be allowed in a work of its purported character.

Mr. A. R. C. Selwyn, in the Canadian Naturalist,* opposes the use of
the numerous names based upon purely theoretical lithology ; i. e. No-
rian, Montalban, Taconian, Keweenian, etc., in the crystalline rocks.
He includes the Copper-bearing rocks in the Huronian. His views, how-
ever, were objected to by Mr. Thomas Macfarlane.t Mr. Selwyn’s paper
was again published in the Report of Progress of the Canada Geological
Survey for 1877-78 (A, 15 pp.). ‘

In the third edition of Prof. J. D. Dana’s Manual of Geology (p. 778)
we are given his views concerning the deposition of the copper at Lake
Superior as follows: ‘“ When eruptions of melted rock have taken place,
they have often brought not merely the heat of great depths to the
surface, but also, various mineral materials encountered on the way up,
and especially some of the metals or their ores.

“The fissures were in general deeper than those that gave origin to
veins of segregation, for the latter did not reach to where melted rock
could fill them, and hence had to be filled by what they could
get through the slower process. They consequently must have de-
scended to regions of very high temperature. As in a volcanic conduit,
whatever at these depths, in the heated subterranean region adjoining
the opened passage-way, was ready to pass into a state either of vapor
or liquidity, would have been forced, by the pressure to which it was
subjected at those depths, to escape, if possible, by the way made for
the liquid rock, and would have ascended either along side of the latter,
or within its mass; and at the same time, a portion would have been
liable to be forced into the wall rock of the fissure wherever it was not
of too close a texture to receive it. The mineral material that could take
adyantage of such an opportunity, or be aided in it by the heat of the
ascending melted rock, would be that, as just implied, which was most
easily fused or vaporized; and this includes certain metals and their

* 1879, (2,) IX. 17-32.
{ Remarks on Canadian Stratigraphy, Can. Nat. and Geol., (2,) IX. 91-102.

MUSEUM OF COMPARATIVE ZOOLOGY. 107

ores, especially those of copper, silver, and antimonial, arsenical, and
sulphurous ores of lead, or of lead with silver or copper. The fusing
points of pure copper and silver are below 2,500° F., that of copper
being, according to Riemsdyk’s experiments, at the Utrecht mint, in
1869, 2426° F. and that of silver, 1904° F.; and hence these might have
passed into the melted rock in the liquid state; but whether this was
the fact, or whether they were in vapor, or in some vaporizable or solu-
ble compound, is not definitely known.

“The above is a general explanation of the initial movement in the
making of copper mines like those of Lake Superior, in which the
metal is in the native state, and the silver mines of Nevada, Mexico,
Bolivia, Chili, Transylvania, and of many other regions, which afford
various ores of silver with often some native silver. The igneous rock
of the Lake Superior region is largely doloryte, and copper is in fissures
and cavities in the igneous rock, and in the sandstone of the walls.”

In the third volume of the Geology of Wisconsin the copper-bearing
rocks are regarded as older than the sandstone, but younger than the
Huronian. The traps, with their associated sandstones and conglom-
erates, are called the AKeweenawan series, while the supposed unconform-
able sandstone is regarded as Potsdam. The evidence advanced is good,
so far as it goes, but it proves nothing until it shall be shown that the
old basalts studied in each particular case are not dikes, but overflows
identical in age with those on Keweenaw Point, and that they are not
earlier or later eruptions. In this respect the strongest evidence ad-
vanced by the Wisconsin geologists is fatally defective. Their methods
of observation fail in giving the proof necessary to establish their con-
clusions, which may or may not be correct, so far as their work goes.

Historical Summary.

The theories advanced concerning the Copper district are so various
and conflicting, in many cases even in the writings of the same author,
that we cannot hope to do justice to them in a brief summary.

The principal points to which we have directed attention thus far are :
Ist, the origin of the traps and their interbedded sandstones and con-
glomerates ; 2d, the relation that the traps bear to the eastern and
western sandstones; 3d, the age of the eastern sandstone; 4th, the
origin of the veins and the copper deposits.

Concerning the origin of the traps, it has been seen that they were
said to be in dikes, generally intruded through the series of sandstones

108 BULLETIN OF THE

and conglomerates, by Houghton, Jackson, Shepard, Hubbard, and Mar-
cou. They were thought to be in lava overflows by Hubbard, Foster
and Whitney, Jackson, Bigsby, Hall, Hunt, Pumpelly, and Irving.
They were regarded as metamorphosed sedimentary rocks by Locke,
Rivot, Pumpelly, and Brooks, while the amygdaloidal portion was said -
to have been formed from fused sandstone by Houghton and Jackson,
and from sedimentary material, possibly volcanic mud, by Hunt. The
latter author at first taught that the traps were eruptive, but separated
the amygdaloids from them.

The traps were supposed to be of a prior age to the sandstones by
Bayfield (who thus long antedated the views of Pumpelly and Brooks),
Logan, Whittlesey (who regarded them as conformable with the sand-
stones), Alexander Agassiz, Pumpelly, Brooks, Hunt, Rominger, Irving,
and Selwyn. They were said to be younger than the sandstone by
Houghton, Jackson, and Marcou. They were taken to be of the same
geological age as the sandstones by Hubbard, Foster and Whitney,
Jackson, Bigsby, Rivot, Logan, Hall, Dana, Pumpelly, Hunt, and Rom-
inger.

The traps were assigned to a geological age distinct from the eastern
sandstone, and given the name Keweenawan by the Wisconsin geologists,
Keweenawian by Brooks, and Keweenian by Hunt. Logan and Selwyn
assigned them to the Huronian, the latter doing so principally on ac-
count of the erroneous observations of Pumpelly and Brooks.

The eastern sandstone of Keweenaw Point was regarded as Old Red
by Bayfield and Bigsby ; as New Red, by Houghton, Ruggles, Jackson,
H. D. Rogers, Shepard, Owen, Marcou, and Dana; as Potsdam, by Hub-
bard, Foster and Whitney, Owen, Logan, Hall, W. B. Rogers, Rivot,
Rominger, and Irving; as partly Potsdam and partly Calciferous, by
Logan and Dana; as Calciferous, by Dana; as Chazy, by Logan; as
Quebee, by Logan, Hunt, and Pumpelly ; as Permian, by Macfarlane ;
and as Permian or Triassic, by Bell. The sandstone was also thought
to be older than the Potsdam by Logan and Whittlesey.

Dr. Houghton at first regarded the sandstone and trap from the Sault
St. Marie to the Porcupine Mountains as the same formation ; later, he
thought that the sandstone west of Grand Island was unconformably
overlaid by that east of that island ; still later, the sandstones east of
Keweenaw Bay were said to be older than the Trenton, while the Cop-
per-bearing rocks were thought to be New Red.

The veins were thought to have been formed anterior to the traps by
Jackson, and at the time of their eruption by Dana and Marcon, but by

MUSEUM OF COMPARATIVE ZOOLOGY. 109

the majority of the observers posterior to the consolidation of the entire
series of rocks. They were believed to have been filled by injection by
Houghton, Ruggles, Jackson, Agassiz, and Marcou; by injection and
sublimation, by Hodge ; by sublimation, by Houghton and Jackson ; and
in the wet way, by Foster and Whitney, Rottermund, Miiller, Bauer-
man, Dawson, Pumpelly, Marvine, Hunt, and others. Houghton re-
garded the district as identical with Cornwall. The copper was
supposed to have been thrown from volcanoes by Schoolcraft, while
H. D. Rogers and Dana teach that it was deposited during the cooling
of the trap. Ruggles, Agassiz, and Marcou regard it as injected in
dikes from the molten interior, while Bauerman and Pumpelly teach
that it was originally deposited in the sandstone from the sea-water
through the reducing agency of organic matter. This view seems to be
shared by Hunt, who likewise, in common with Shepard, thought that
copper was derived from the débris of ores in the older rocks, and depos-
ited in the sandstones. Prof. Shepard thought that it was concentrated
from the sandstones, and brought to the surface by the action of the
traps. Whether Dr. Hunt teaches that the copper was derived directly
from the sandstones and deposited in the veins, or was brought up by
the extravasated traps, which, according to his theories, must have
originally formed the lower portion of the Keweenawan series, and was
thence concentrated in the veins, we cannot tell, for, as is frequently
the case in his writings, his English admits of more than one construc-
tion. Miiller, Banerman, and Marvine think that the copper may have
been an original constituent in the traps in a finely divided condition.
Prof. Dana teaches that it was derived from ores in the older rocks
by the action of the traps, and holds, with Houghton, Jackson, and
Shepard, that it was brought up by the trap. Foster and Whitney,
Dawson, Miiller, Bauerman, Pumpelly, Marvine, and others, would refer
the concentration to electro-chemical action. Benjamin Silliman, Jr.,
and Jackson said that the copper and silver, when found joined, had
been fused together ; while Hodge explained the phenomenon by sup-
posing that the copper was injected first, and by its contraction left
vacant spaces into which the silver was injected later. Such, in brief,
are some of the various theories advanced.

The Traps.

In order to ascertain the origin of these rocks, we have to examine,
first, their relation to one another, and, second, to the interlaminated
sandstone and conglomerate.

110 BULLETIN OF THE

The relations of these rocks can be well studied in an adit about one
mile long, extending from the western sandstone through alternating
beds of sandstone, conglomerate, and trap, to the ash-bed at the Cop-
per Falls mine. We find here that the sandstone, when underlying
the trap, has its upper portion adjacent to it baked and indurated; .
showing the usual characteristics of a ferruginous sandstone when
subjected to a certain amount of heat. This indurated sandstone has
frequently been subjected to secondary water action since it was buried
under the trap, and hence has lost some of its hardness and other signs
of baking. No fragments of the trap were found in the immediately
underlying sandstone, but tongues of trap extend down into it in some
places, and indurate it. The surface of the trap underlying the sandstone
is water-worn, forming smooth, rounded knobs and irregularities, upon
which the sandstone was deposited. The immediately overlying sandstone
shows none of the baking and induration that the underlying one does.
In no case, so far as we saw, was there any difficulty in separating the
sandstones or conglomerates from the traps. The upper side of the
sandstone was especially distinctly separated from the overlying trap,
while on the under side, on account of the composition of the sandstone,
the junction was not so obvious. While the trap always affected its
underlying sandstone, and frequently included masses of it, in no case
did it produce any effect on the overlying one. The sandstones or con-
glomerates at their base contain fragments and pebbles of the under-
lying trap; but this detritus diminishes as we recede from the trap, and
is generally wanting after a thickness of two or three feet has been laid
down. ‘The trap is found to be cellular and amygdaloidal on its upper
side, but on the lower to be compact and more coarsely crystalline. If
the traps had been intrusive between the beds of sandstone, both the
upper and underlying sandstone would be alike affected adjacent to the
trap. If the trap was formed from the sandstone metamorphosed
in situ there ought to be some gradual passage between the two, and
the fragments of sandstone enclosed in the trap should more especially
show such passage. On the contrary, nothing of the kind could be
found, but the sandstone fragments were greatly indurated, and the
traps adjacent to them filled with quartz (646, 647, 648). Specimens
469, 478, 479, 480, 482, and 483 from the Calumet and Hecla, and 621
from the Copper Falls mine, are examples of the contact of the sand-
stone with the underlying trap, and 477 and 478 from the Calumet and
Hecla, and 577, 578, 579, 610, 611, 612, 613, and 620 from Copper Falls,
show the contact with the overlying trap. The only explanation of

MUSEUM OF COMPARATIVE ZOOLOGY. 111

these facts, which were first pointed out by Messrs. Foster and Whit-
ney, and later by Mr. Marvine, is that given by them, that the traps are
lava flows, and that they were successively laid down upon one another,
or covered by sandstone and conglomerate. They are seen to have the
same characters, except so far as they have undergone secondary changes,
that modern basaltic lavas have. These old basalts have been denomi-
nated melaphyrs and diabases by Prof. Pumpelly, to whom lithologists
are indebted for their knowledge of their microscopic characters. While
we would use the terms that Prof. Pumpelly has, we object to the ap-
plication he has made of them. Many of his diabases we should call
melaphyrs, and many of his melaphyrs we should class as diabases.
We of course differ in our definitions of these terms, for while he would
regard melaphyr and diabase as distinct rock species, we hold that they
are only altered forms of basalt. The greenstone ridge back of the
Cliff and Phoenix mines we regard as an excellent example of diabase
(791, 792), with which we class all the heavy-bedded crystalline traps
of that region, while the thin-bedded scoriaceous or amygdaloidal highly
altered traps we class as melaphyr, but in the majority of cases Prof.
Pumpelly regards them as the reverse. The diabases are yarely if ever
mined, the melaphyrs frequently.

In a recent paper “On the Carboniferous Volcanic Rocks of the
Basin of the Firth of Forth — their Structure in the Field and under
the Microscope,” * Prof. Geikie points out the difference microscopically
between lava flows and intrusive masses, and evidently thinks that
they can always be as readily separated in the cabinet, microscopically,
as they can be in the field. While it is doubtless true that this sepa-
ration can be made in the rocks studied by Prof. Geikie, his distinc-
tions fail in the Lake Superior district. The difference in structure
pointed out by him seems to be entirely owing to the rate of motion
and pressure at the time of crystallization, and the rapidity with which
the lava solidified. When lava flows in thin sheets, or, if we con-
fine our examination to the upper portion of a thick sheet, we find
characters that readily distinguish the sheets from the dikes ; but when
we come to study the middle and lower portions of the thick sheets,
where there was little or no motion combined with the pressure of the
overlying mass, the rock is undistinguishable from rock of the same
composition in dikes; and the diagnostic characters given by Prof.
Geikie would assign it to an intrusive rock, not to an overflow. In the
before-mentioned Emerson adit at the Copper Falls mine, some mela-

* Trans. Royal Soc. of Edinburgh, XXIX. 437-518.

112 BULLETIN OF THE

phyrs were seen that were apparently in the form of dikes intruded
since the lava flows (624, 626, 627, 628).

The form of lava locally known as “ ash-bed” has attracted considera-
ble attention. It has been described in various ways, generally being
regarded as fused sand and trap. Latterly Prof. Pumpelly bas described
this as “volcanic scoriz buried in the littoral sand.”* At the present
time the ash-bed can be best studied at the Copper Falls mine, where it
is largely mined for the copper it contains. After a careful study of it,
we conclude that the ash-bed is a very scoriaceous, and, comparatively
speaking, somewhat thin lava flow. It does not possess the ordinary
characters of the other flows of Keweenaw Point, but seems to be largely
made up of clinkers and scoriaceous masses. It appears to have flowed
in a more or less fragmental condition, forming a black, rough, loosely
aggregated, scoriaceous, cinder and lava sheet, similar to those described
by Prof. Whitney in his ‘ Report on the Geology of California,” and
by Prof. Palmieri in his “ Account of the Eruption of Vesuvius of
1871-72.”

At the time of the flow, or since, the interstices were filled with de-
trital mud. .The various parts of the flow seem to be connected in the
main, and do not form to any great extent true pebbles.

That the rounded fragmentary portions derive their structure from
the cooling of a fluid mass, and not by water action on the melaphyrs,
is shown by their cellular structure in the interior, and solid crust on
the exterior, the same as similar modern lavas have. Watey-worn peb-
bles of melaphyr, as seen at some of the old burrows of the Hancock
mine in a detrital deposit (832, 833), which to the casual observer
resembles the ash-bed, have the cellular structure extending throughout
the mass, and are destitute of any crust.

The same flow exists at the Petherick and Old Phenix mines, while
a similar formation is mined at the Atlantic. Besides the true ash-beds,
there seem to be confounded with them certain sedimentary deposits
composed of rounded water-worn pebbles of melaphyr held by littoral
sand. These forms pass into a more siliceous conglomerate or sand-
stone, or not, according to the length of time that elapsed before the
succeeding flow. They are abundant west of Houghton, and, so far as
I could find, are the only formations existing at the Hancock mine that

* Proc. Am. Acad., XIII. 283.

t 1865, Vol. I. p. 267.

¢ Annali del reale Osservatorio meteorologico Vesuviano, (Napoli, 1873,) p. 28.
The same, translated by Robert Mallett, (London, 1$73,) p. 103.

MUSEUM OF COMPARATIVE ZOOLOGY. 113

could have led Prof. Pumpelly to state that an ash-bed was worked
there.* Specimen 814 is a good example of the end of a lava mass,
which still retains its original ropy and fluidal surface structure. This
came from the ash-bed at Copper Falls, and gives conclusive evidence
that it had never been water-worn. Tongues of the ash-bed were seen
extending down into its underlying trap, while the overlying trap sends
tongues down into the ash-bed (Fig. 27).

From their nature all the various lava flows are liable to be limited in
any direction, either from their thinning out, the flow meeting obstruc-
tions, or from denudation since deposition, but before being buried under
conglomerate or the succeeding flow. They were evidently poured out
on a shore line, whose position probably varied relatively to the traps.
The intervals between the different flows seem to be brief in some cases,
while in others considerable time must have elapsed. Figure 28 shows
the relation of the trap to the sandstone at one point in the Emerson
adit at Copper Falls, exhibiting the irregular surface of the latter before
the lava flow.

The Sandstones and Conglomerates.

As we followed the Hungarian River, a tributary of Torch Lake, up-
ward, starting from the low sandy plains near the lake, the sandstone
was first observed forming high bluffs on both sides of the river, and
dipping N. 45° W. 10°. It occurs in coarse and fine layers often en-
closing pebbles. As the river is ascended the layers of pebbles were
seen to curve in various directions with an irregular dip, but which in
general inclined to the northwest. Some of the pebbles appeared to be
of quartzite similar to that at Carp River, Marquette (522). The Hun-
garian Falls are formed by the river being precipitated over several
ledges of the sandstone and conglomerate. Several specimens were
taken, showing the different varieties of pebbles composing the con-
glomerate (523, 524, 525, 526, 527, 528, 529, 530). No. 523 is an old
trachyte composed of a reddish-brown groundmass, holding white kao-
linized feldspars, dark brown decomposed hornblende crystals, and a
little mica. It is closely allied to some of the modern rocks from the
Cordilleras. The groundmass is now kaolinized, forming a dirty-white
mass holding secondary quartz and feldspar, as well as long narrow
ferrite masses. These latter appear to have been formed from the horn-
blende fibres, so frequently seen in the allied rocks from the Cordilleras.
The groundmass has now through its alteration a spherulitic structure.

* Proc. Am. Acad., XIIT. 283.
VOL. VII. — No. 1. 8

114 BULLETIN OF THE

No. 524 is a more compact rock of like character. Its groundmass is
kaolinized and holds the quartz and feldspar alteration products. It
is filled with grains and masses of ferrite probably derived from horn-
blende. The feldspar is so decomposed that it cannot be told whether
it is plagioclase or orthoclase. Nos. 526 and 529 are like No. 523,
while No. 530 is more allied to No. 524.

No. 527 has a more coarsely crystalline, granitoid structure, showing
under the lens a reddish and grayish brown groundmass, holding elon-
gated brownish-black hornblende crystals. In the thin section it is
seen to be composed of feldspar, magnetic iron, hornblende, and some
quartz. The feldspar is greatly altered, and is now composed of inter-
growths of feldspar and quartz, giving rise in it to a structure resem-
bling that of graphic granite, or much of that figured as belonging to
the Eozodn Canadense. The quartz is all secondary, and the hornblende
altered to reddish or yellowish brown ferruginous masses.

No, 528 is a fine-grained granitoid trachyte (granite porphyry), but
in the thin section the feldspar is seen to be so altered and filled in with
secondary quartz, containing full and bubble-bearing fluid, and vapor
cavities, that the section resembles that obtained from some fragmental
rocks. No. 525 isa rock of similar character.

Nos. 538, 539, 541, and 544 are good examples of some of the sand-
stones on the river below the melaphyr. No. 538 is seen in the section
to be composed of quartz and trachytic detritus.

Below and at the base of the falls the dip remains the same as before,
N. 45° W. 10°, but above this locality the inclination varies, rising from
15° to 18° between the first and second falls. In some places a qua-
quaversal dip was seen. Some five falls exist in the river, and at the
last or upper fall the melaphyr was found. The dip of the sandstone
has now increased to some 20°, but still dips northwest, and the first
trappean flow is seen to overlie and greatly indurate and alter it. This
immediately underlying sandstone (537) is filled in with little reticulated
veins of calcite, a kaolin-like material, etc., and in general resembles the
baked sandstone found underlying the trap on the western side of Ke-
weenaw Point. Microscopically, it is seen to be composed of the débris
of the trachytes previously described. This sandstone was seen within
three inches of the melaphyr, and although there may have been some
sliding motion between the two, as the contact was not seen, yet the
induration of the sandstone, its dip, and its relations to the melaphyr,
prove that it underlies the latter, which flowed over it. This, then,
with evidence obtained on the Douglas Houghton River, settles the

MUSEUM OF COMPARATIVE ZOOLOGY. 115

long-disputed question of the relative age of the traps and eastern sand-
stones of Lake Superior. The dip of the melaphyr is about the same as
that of the sandstone. Immediately above this thin lava sheet, a con-
glomerate comes in, forming the fifth fall. The base of this conglom-*
erate is composed of a fine-grained detritus formed from the melaphyr
and trachyte, and holds numerous pebbles of the melaphyr, as well as
of the other rocks (531, 532, 533, 534, 535, 536). Immediately over-
lying this conglomerate is another melaphyr flow, and we have here on
the eastern side a repetition of the same alternate bands of melaphyr
and sandstone that occur on the western side.

It is to be remembered that Mr. Agassiz, in conjunction with Mr.
L. G. Emerson, the well-known mining engineer of Hancock, and at one
time assistant on Prof. Pumpelly’s geological survey, found below the
Douglass Houghton Falls pebbles of the melaphyr (amygdaloid) in
the sandstone ; and from this the conclusion was drawn that the sand-
stone was younger than the trappean formation. At the time of our
visit to this locality, we had no knowledge of Mr. Agassiz’s observa-
tions,* except from the general statement of Prof. Pumpelly.t It will
be seen that no localities were given by Prof. Pumpelly, although he con-
firms Mr. Agassiz’s statements. The falls were said by Mr. Agassiz to be
located at the junction of the sandstone and trap, while on both sides
of the ravine the horizontal sandstone beds were traced up to the falls.
Our examination showed that immediately below the falls sandstone
and conglomerate exist, dipping N. 45° W. 25° (504, 505). While the
majority of pebbles were of the usual character, one grayish granitoid
pebble (506) containing epidote was obtained. This has suffered the
same graphic alteration in its feldspar that No. 527 has. Much of the
feldspar is seen to be triclinic. Otherwise than its containing more
quartz, its characters are in the main like No. 527. The sandstone, at
its junction with the overlying trap, is much indurated and altered, and
specimens were obtained showing the junction of the two (507, 508, 509,
510, 511). As the sandstone underlies the trap, it is of necessity the
prior-formed rock. We suppose that this was the locality at which
Messrs. Agassiz and Emerson obtained their specimens of melaphyr in
the conglomerate. If so, it is easily enough explained, for conformably
underlying this sandstone is another sheet of melaphyr, then more sand-
stone, again more melaphyr, and so on, all conformably underlying one
another as much as they do anywhere within the trappean belt, or can

* Proc. Bost. Soc. Nat. Hist., XI. 244-246.
t Geol. of Mich., Part II. p. 3.

116 BULLETIN OF THE

do, on account of their origin. Whether this is the spot or not, it is
evident from the language of Mr. Agassiz’s paper that the gentlemen
took their facts and drew their conclusions while they were within the
trappean belt, not having found the junction at all, it being some dis-
tance below the falls, not at them. From Prof. Pumpelly’s state-
ment it would seem that he had made the same mistake, as likewise
Mr. Foster had done years before.* Something more is necessary to
be observed than simply to find a sandstone or conglomerate on the
eastern side ; it is necessary to prove that it is part of the eastern sand-
stone, and not a bed intercalated in the trap. The sandstone and mela-
phyr, a short distance below the dip last given, has a dip of 20°, still
inclining to the northwest. The last melaphyr sheet underlies a sand-
stone dipping at this angle, and is itself underlaid by another sandstone
having the same dip. In other words, the last trap on the eastern side
of Keweenaw Point is a thin flow of only some two feet in thickness, at
this locality, and is interbedded between sandstones which immediately
above and below it have the same dip that it has. As the river is fol-
lowed downwards the dip gradually declines in steepness, although still
dipping northwest. The last dip measured was N. 45° W. 5°. The
conglomerate and sandstone below the first basaltic flow, i. e. that near-
est to Torch Lake, has apparently been acted upon by hot waters. The
sandstone has been leached, its feldspathic constituents largely changed
into clay, and the pebbles are greatly altered and kaolinized. The con-
stitution of the sandstone and conglomerate appears to have been origi-
nally the same as that of the bands interlaminated with the trap, except
so far as they are modified by the detritus of the latter. In many places
this hot-water action has bleached the sandstone and leached out of it
all the argillaceous material, leaving it a nearly pure siliceous sandstone
(518). This has also converted some of the finer beds into a fine-grained,
highly argillaceous sandstone or arenaceous clay, these beds having prob-
ably arrested the progress of much of the argillaceous material (519,
520). This water action would certainly account for the absence of fos-
siliferous remains in the sandstone exposed to its effects. Considerable
mica in fine scales was seen in the argillaceous bands. Specimens of
the various pebbles were taken from the conglomerate (513, 514, 515,
516, 517). No. 517 is a grayish and reddish-brown granitoid-looking
rock, and under the lens is apparently composed of feldspar holding
quartz grains. Microscopically it is seen to be a crystalline aggregate of

* Senate Docs., Ist Sess. 31st Cong., 1849-50, III. 782; Executive Docs., 1st
Sess, 31st Cong., 1849-50, 1X. Doc. 69, p. 67. phase

MUSEUM OF COMPARATIVE ZOOLOGY. 117

decomposed feldspar and hornblende, holding much secondary quartz.
The quartz is arranged in the feldspar in the graphic or eozoin form,
which makes the decomposed feldspar a most beautiful object in polarized
light. The contrast between the brilliantly polarizing quartz and the
feebly polarizing, kaolinized feldspar substance is thus strongly brought
out. The quartz appears to have been deposited from the decomposed
feldspar itself, which breaks up into silica and the kaolin-like material.
The quartz contains full fluid cavities, those with bubbles, and vapor
cavities. The hornblende is in the usual reddish-brown decomposed
masses. Some magnetite was seen. This rock is most probably a de-
composed old trachyte, although it would doubtless be regarded as a
granite porphyry by most lithologists. No. 515 is a similar but more
feldspathic rock. No, 513 is similar to No. 527, and Nos. 514 and 516
are like No. 524. Many pebbles or lenticular masses of clay were seen,
that are apparently decomposed pebbles of the conglomerate.

In the sandstone quarry at the head of the zze/zne on the Hecla and
Torch Lake Railroad, the sandstone layers have been regarded as being
nearly horizontal. The joint planes that form the floors of the quarry
are nearly so, having only a slight dip to the northwest ; but these joint
planes cannot be the bedding planes, for we find on close examination
that numerous layers of coarser material, pebbles, clay masses, etc. occur
in the rock. These layers extend for long distances through the sand-
stone, and are always parallel, having the same dip, which is N. 45°
W. 15°. These of course, from their character and regularity, must
mark the old planes of bedding, while the generally supposed bedding
planes are secondary joint planes cutting the bedding planes at a small
angle. This sandstone (456, 457, 458, 459, 461, 462, 463, 464) has
been leached and acted upon by water the same as that below the Doug-
lass Houghton Falls, and its feldspathic material converted into clay or
entirely removed. Part of the materials composing the sandstone, espe-
cially in the coarser portions, are similar to those in the sandstone at
Marquette. The quartz grains are partly water-worn, but a large pro-
portion are seen to be short erystals formed of the hexagonal prism,
terminated on both ends by the pyramid, or the usual form found in the
acidic porphyritic rocks. It appears, then, as the facets of these crys-
tals are comparatively unworn, that they were derived from the destrue-
tion or decomposition of trachytic and rhyolitic rocks (granitic and
quartz porphyries), the feldspathic material having been removed since
by water, leaving a quartzose sandstone. It is a question worthy of
examination whether any other sandstones have been formed from

118 BULLETIN OF THE

acidic volcanic material, from which nearly all the other parts of the
rock have been removed by percolating waters ; especially as other sand-
stones have been said to be composed of quartz crystals.

As the sedimentary rocks are more and more studied, the evidence
comes on every side that, like this sandstone, while their formation may
have taken as long as is generally supposed, they may have been de-
posited very rapidly, some being composed of old volcanic scoria, ashes,
and mud. In very many other cases the supposed sedimentary rocks
are really volcanic flows or intrusive masses. In the sandstone just de-
scribed the same masses of clay (460) occur as on the Douglass Hough-
ton River, and they may arise here, as there, from the decomposition of
the enclosed feldspathic or argillite pebbles. Another solution of the
question of the origin of some of these would be the filling in of cavities
formed by the removal of some other material, by the argillaceous mate-
rial brought from above. This is suggested by the finding of stalactites
of the sandstone (464) extending down into the clay. At the spring just
above the quarry the sandstone (521) is red spotted with white, and
dips N. 45° W. 14°.

The relations of the traps to the interbedded sandstones and conglom-
erates have been given before. The trap has, when covered by the sand-
stone, been worn by water, and the latter rock deposited upon it. The
sandstone, in its lower portion, holds to a greater or less extent the
débris of the underlying trap. Should we apply then rigorously the
logic of the Michigan and Wisconsin geologists, we should make a dis-
tinct geological age every time a bed of sandstone or conglomerate was
formed over any of the trappean flows. Their method of reasoning
would prove that the Keweenaw series is made up of some forty to sixty
different geological ages, every one as distinct from the age of the rocks
underlying it, as they would make the Potsdam sandstone distinct from
the Keweenawan.

Besides the melaphyr pebbles and detritus, the conglomerates are
composed of similar pebbles to those found in the conglomerate of
the eastern side. No. 552, from the Hecla mine, has a dark reddish-
brown groundmass, holding white and pinkish feldspars and quartz. In
the thin section it is seen to be an old rhyolite, and to have flowed as a
lava, for it possesses the contorted, twisted, fluidal structure seen in so
many of the rhyolites from the Cordilleras, with which it can be per-
fectly parallelized, except so far as the alteration has removed some of its
original characters. It shows the same twisting and interweaving of the
brownish-colored glassy material that they do; its quartzes are fissured

MUSEUM OF COMPARATIVE ZOOLOGY. 119

and rounded, and penetrated by the base the same as they are in mod-
ern rhyolites ; and in like manner they are seen to be of prior origin to
the consolidation of the lava. The quartz here, as in the rhyolites, plays
the same part that olivine does in the basalts and hornblende in the
andesites. It is a foreign ingredient, of prior origin to the lava, and
has not crystallized out of it.* The quartz contains stone, vapor, and
fluid inclusions. The majority of the fluid and vapor (empty) cavities
are arranged along fissures, as if they had been formed by hot waters
depositing silicg in fissures. The feldspar is thoroughly kaolinized,
and, like the quartz, is frequently in rounded and broken pieces,
which show that it was formed prior to the consolidation of the lava.
Considerable secondary quartz occurs in the groundmass, but the base
affects polarized light but little, if at all.

It is intended to figure this section in connection with some of the
rhyolites of the Cordilleras, for if ever a section showed conclusive
proof that the view, that volcanic action did not commence until the
Tertiary epoch, is fallacious, this is one. No. 553, from the same locality,
has a similar, but lighter brown and less abundant groundmass. This
holds numerous yellowish-red and clay-colored feldspars, as well as much
quartz. This rock, like the preceding, is an old rhyolite (quartz por-
phyry). The base is an olive-brown, felty mass, holding opacite grains,
quartz, feldspar, and decomposed black hornblende. The characters of
the quartz and feldspar are like those in the preceding rock. On the
edges and in the cleavage planes of the feldspar, copper has been depos-
ited in both of these rocks. No. 554, from the same locality, is a grayish-
red, granitoid rock. In the thin section this is seen to be like the more
granitoid strachyte pebbles found towards Torch Lake, and described
before. This contains much secondary quartz, and a little that appears
to be primary. The feldspars are decomposed, and the quartz is so
arranged in them that they show the graphic characters. The rock
holds numerous rows of ferrite globules, which rows are arranged in a
radiate form, giving to the slide a spherulitic appearance. A little of
the feldspar is seen to be triclinic. No. 562 is a pretty brown rhyolite
(felsite) with a very compact groundmass, holding some minute feld-
spars. This was taken from the conglomerate of the Osceola mine. The
feldspars are seen to be largely triclinic, while the groundmass is a
brownish devitrified aggregate of secondary quartz, feldspar, and ferrite.
The finer portions of the Calumet conglomerate are seen microscopi-
cally to be composed of the rhyolitic and trachytic detritus, the former

* Bull. Mus. Comp. Zodlogy, V. 277 - 282.

120 BULLETIN OF THE

predominating. In one of the enclosed fragments, quartz was seen
containing several of the double pyramidal inclusions so common in the
quartz of modern rhyolites.

On the Mineral Point Railroad, about three fourths of a mile from Han-
cock, the melaphyrs were seen to be interbedded with a number of con-
glomerates. Certain pebbles intended to represent the different varieties
were collected. No. 419 is a very compact, fine-grained, reddish-brown
rhyolitic rock (felsite). In the thin section it shows a compact ground-
mass, made up of the devitrification products : quartz, feldspar, and ferrite.
No. 420 has a reddish-brown groundmass, holding reddish feldspars and
black hornblendes. The feldspar is seen in the thin section to be much
decomposed, and part holds quartz in the graphic form in it. Some
retains traces of its triclinic character, but all has the same hematite
alteration product that is common in orthoclase. The hornblende erys-
tals of this old trachyte are changed to ferrite and viridite. Besides the
quartz, ferrite, and viridite, as another alteration product epidote occurs.
This mineral is quite abundant. Magnetite and some apatite were seen.
No. 421 has a very compact, reddish-brown felsitic groundmass, holding
feldspar crystals. This old trachyte (feldspar porphyry, or felsite), in
the thin section, is seen to have a reddish-brown groundmass, composed
of alteration quartz, feldspar, and ferrite. The porphyritically enclosed
feldspars are largely plagioclase. No. 422 is another trachyte (felsite
porphyry), containing numerous reddish and greenish-gray feldspar erys-
tals, held in a dark, reddish-brown groundmass. Microscopically the
feldspars and groundmass are seen to be greatly decomposed and kaolin-
ized. Viridite, epidote, opacite, and quartz occur as alteration products.
This rock is closely allied to the andesites.

No. 423 is a very fine-grained reddish granite, composed of feldspar,
quartz, hornblende, and biotite. Considerable alteration quartz, ferrite,
and opacite were seen. The feldspars are much altered. The quartz
contains fluid, vapor, and stone cavities, also numerous trichites.

No. 424 is a brick-red granitoid trachyte (granite porphyry). The
feldspar is much decomposed, and has the alteration quartz arranged in
the graphic form. The rock shows through its alteration a somewhat
spherulitic structure. This arises from the radiating arrangement of
the alteration products in the groundmass. The sandstone found asso-
ciated with the conglomerates is made up of the fine detritus of these
trachytic and rhyolitic rocks, mixed to a greater or less extent with the
basaltic material.

_ The sandstone and conglomerate west of the traps were studied in sev-

MUSEUM OF COMPARATIVE ZOOLOGY. 121

eral places, especially at Copper Falls, west of Houghton, and northwest
of Hancock. At the latter locality, marked s/ates on the map of the
Portage Lake district, by A. R. Marvine and L. G. Emerson,* or, in other
words, at the bottom of the ravine below the curve, at the end of the
heavy grade of the Mineral Range Railroad, they were examined the
most thoroughly, as that locality seemed to be the most probable place
to find fossils, if any existed in the sandstone. Although our search
was unsuccessful, we think it very probable that, if one had the appli-
ances for more extended work, fossils might be found here. The con-
tact of the sandstone with the traps was not seen here. In the parts
nearest the latter it is a coarse, reddish-brown sandstone, composed of
reddish feldspar, quartz, and basaltic detritus (387, 388, 409). It is
composed of the same materials as the sandstone, interbedded with the
basalts, although it perhaps has more basaltic detritus than they do. ,
The enclosed pebbles appear to be trachyte (felsite porphyry), of the
same character as those found within the trappean district near Han-
cock (389). ;

As we recede from the traps, the sandstone becomes finer, or passes
into a shale composed of the same materials (390, 391). Lenticular or
rounded concretions occur in the shale, which closely resemble pebbles
(392). Little spherical concretions of sand, similar to those described by
Messrs. Foster and Whitney,f occur here (393, 394). In some of the
coarser portions of the sandstone, interstratified with the shale, little
fragments and scales of argillite were seen (395). Some of the shale
is fine and earthy (398), and in places shows rain-drop impressions (399,
400), ripple-marks (400, 401, 402), and mud-flows (403, 404, 405, 408).
About two miles above Hancock the sandstone was formerly quarried,
on the shore of the lake. Its dip is N. 30° W. 23°. The dip of the
conglomerates nearer Hancock, interstratified with the traps, is 40°.
Any inequality of the lava flows or of the shore deposits of sand and
pebbles would give rise to a change in the dip of succeeding beds.

West of Houghton, sandstone and conglomerate of the same general
character was observed dipping N. 45° W. 30°. It is probable that the
Lanmontite (“red Zeolitic mineral”) which Dr. Rominger describes as
occurring here, and also forming the cement of the conglomerates else-
where,# is the red feldspar of the trachytes (felsites). The material of
which the western sandstone is composed, and its junction with the

* Geol. of Mich., I., Atlas, Plate XIV. a.

+ Executive Docs., Ist Sess. 31st Cong., 1849-50, IX., Doc., 69, p. 112.
+ Geol. of Mich., I., Part III. pp. 97, 98.

122 BULLETIN OF THE

trap, all show that it is of the same geological age as the trappean
rocks, although younger in point of time.

The sandstones and conglomerates are evidently beach-worn, and
are simple shore deposits. Whence the trachytic and rhyolitic ma-
terial came, is a subject worthy of future investigation. They were
evidently lavas that had been erupted prior to the basaltic flows, and
a knowledge of their original position, as well as tracing the different
kinds to their present resting-place, would give us considerable knowl-
edge of the physical geography of that old sea. The conglomerates
occurring interbedded with the traps would of necessity be more limited
and variable than the lava flows themselves, for they could only be
deposited upon the part of the lava that lay along the shore line, and
even there only in those places where the conditions were favorable to
the accumulation and retention of detritus. The amount of conglom-
erate would in some measure depend upon the length of time elapsing
between the basaltic flows; but on account of the local nature of the
conglomerates, their absence at any particular spot does not prove the
immediate following of the succeeding eruption, or that no conglomerate
exists elsewhere between the two lavas.

While we were able to do nothing to prove the geological age of the
eastern sandstone, it seems that Dr. Rominger has brought forward
evidence conclusively establishing the correctness of Messrs. Foster and
Whitney’s view, based on its stratigraphical relations, that it was of Pots-
dam age. We have shown sufficient evidence to prove that in the parts
visited by us the eastern sandstone conformably underlies the trap, and
that, as held by Messrs. Foster and Whitney, the eastern and western
sandstones, and the traps lying between them, are of the same geologi-
cal age. Whether the idea is correct or not, as held by these gentle-
men, that the eastern sandstone at the Bohemian and Porcupine Moun-
tains is younger in order of time of deposition than the traps, and was
originally continuous with the western sandstone, we cannot say, having
never studied the sandstone in either locality. It is, however, plain that
such is not the relation of the eastern sandstone in the vicinity of
Torch Lake to either the traps or western sandstone. It is also evident
that the volcanic action began gradually the same as it ended, and pro-
duced similar alternations of trap and sandstone on both sides of Ke-
weenaw Point.

MUSEUM OF COMPARATIVE ZOOLOGY. 123

The Veins and Copper Deposits.

At some time after the sandstones, conglomerates, and traps were
laid down, extensive and deep-seated fissures were formed, generally
extending, in the district north of Portage Lake, across the beds. These
fissures seem to have been formed by powerful movements of differeut
parts of the rocks, causing their cross fracture and dislocation. The
movements have been repeated from time to time, causing a rubbing,
grinding, breaking, and polishing of the parts adjacent to the fissures,
forming numerous slickensides. These movements would not cause ir-
regular aud secondary fracturing to any great extent after the main fis-
sures had been formed, in the heavy-bedded diabases or the sandstones ;
but in the scoriaceous and thin-bedded melaphyrs, the tendency to yield
to the pressure was much greater, and the rock adjacent to the fissures
was broken up to a considerable extent. During the time of the fractur-
ing, and since, the fissures served as channels for water. In the scori-
aceous and easily decomposable melaphyrs the water served by its
decomposition of the adjacent rock to widen the fissures, but in the
diabases, although their composition was the same, their structure and
the absence of much glass prevented the same results occurring. The
sandstones and conglomerates, from their being principally composed
of trachytic and rhyolitic material, and from their structure, suffered
little, compared with the melaphyrs, from vein formation.

In many localities the evidence is strong that the percolating waters
were hot ; in others, as remarked by Marvine, no sign exists that it was
above the temperature of the present day. Water penetrated with
greater or less readiness through the traps themselves, causing their de-
cay and alteration, while the substances taken up in solution by it were
deposited in the fissures, cells, and other open spaces in the rock. The
filling of pre-existing cavities and fissures gave rise to the amygdaloidal
structure of the traps and the vein material ; the decomposition of the
trap, and its replacement of some materials by others, gave rise to
the pseudo-amygdaloidal structure. This structure exists not only in
the non-scoriaceous or non-cellular portions, but also in the truly scori-
aceous or cellular portions.

All or nearly all of the material filling the veins and adjacent traps
appears to have been derived from the decomposition of the traps them-
selves, and not brought in from extraneous sources,— this decomposition
being brought about by the medium of the percolating waters, whose
course seems, in many cases at least, to have been downwards. The par-

124 BULLETIN OF THE

tial decomposition of the fractured portions of the traps and the filling
of the interspaces by the vein matter give rise to the great width which
the veins sometimes attain, — thirty feet. While the veins in the nar-
rower portions are often filled with pure vein material, in the wider
parts they are composed of a breccia of decomposed trap cemented by
vein matter. The comby and sheet structure of the veins, the class of
minerals enclosed, the decomposition of the associated melaphyr, — in
fact, all their characters, — point out that these are true fissure veins
filled by segregation.

In the veins the copper is found intimately mixed with the gangue,
or in sheets or irregular masses. The copper in the sheet form, as
is much of the mass copper of the veins, extends downwards, or has
its sides approximately parallel with the walls of the vein. Oftentimes
the sheet bifurcates, holding some of the gangue or melaphyr between
its parts (818). On cutting the mass copper it is not uncommon to find
completely enclosed in it masses of melaphyr, quartz, calcite, or other
of the vein materials. The association, structure, and the relations of
the copper to the vein material and to the traps, all show that it was
deposited in the same way the vein-matter and secondary materials in
the traps were.

The melaphyrs adjacent to the veins are often impregnated, in the
decomposed portions, with copper, as well as the usual secondary de-
posits. In certain cases it has paid to take out the parts adjacent
to the vein, but fallacious have proved and will prove the hopes of
continous profitable mining based on these local deposits. Vein mines
associated with local deposition of copper in the adjacent traps have
been and are now so abundant at Lake Superior that it would be invidi-
ous for us to specify any one of them. In the vicinity of Portage Lake
the old lava flows themselves are mined. No trace or sign of a true
fissure vein exists in most of the beds that are mined in this locality.
The mining is confined to work upon unstratified deposits, the same as
if some of the more cellular and deeply buried lavas of Vesuvius or
Etna were for any reason mined. These melaphyrs have been greatly
acted upon by hot waters, which have decomposed them, and deposited
the copper in an irregular, “ bunchy ” manner. On the Isle Royale lode
this hot-water action is very strongly marked, the original basalt being
now greatly altered, and filled with epidote and quartz, or other min-
erals (377, 378, 379, 380, 381, 382, 383, 384).

In others the action is not so strongly marked, but more evenly dis-
tributed throughout the bed, as for instance the Quincy. All these bed

MUSEUM OF COMPARATIVE ZOOLOGY. 125

mines have their deposits distributed in a very irregular manner, requir-
ing much dead work as a neccessary concomitant of the way in which
the copper was deposited.

Another variety of the bed mining is that known as ash-bed mining.
As stated before, the ash-bed is a more scoriaceous flow than the gener-
ality of the melaphyrs to which it belongs, and has the copper deposited
throughout its mass, not rich, but quite uniform, or subject to certain
well-marked laws of variation. So far ‘as could be ascertained, the ash-
bed shows no sign of hot-water action at Copper Falls, but rather
evidence that the copper was deposited from a cold, or, at most, only
a warm solution. The rock is but little changed, and retains part of
the signs of its fluid state, almost as well marked as they are in some
comparatively recent lavas. In other mines in which a transverse fissure
vein and a melaphyr (amygdaloid) is mined, the impregnation of the
melaphyr with copper seems to be dependent upon its proximity to the
vein, being rich near the vein, but growing poorer as it recedes from
it. Here the conditions are reversed: the ash-bed is apt to be poorer
near the veins than at a distance from them. Where the overlying
trap sent down tongues into the ash-bed, the latter became indurated,
and consequently but little copper was deposited in it at these places.

The Atlantic mine at Portage Lake is supposed to be on the ash-bed,
or a similar formation. This mine was visited, and the rock found to
be similar to that of the ash-bed, except much harder. This rock has,
like the rock in the other mines at Portage Lake, been subjected to
much more intense metamorphic action than the ash-bed at Copper Falls.
The copper here, however, is quite evenly distributed, and all of the bed -
is stoped out and sent to the stamp-mill. So far as could be told by
lithological evidence, the Atlantic mine is on the same bed as the Cop-
per Falls mine, or on a bed having the same origin. The action of
thermal waters on the former accounts for its present difference from
the latter.

The induration of any rock does not apparently depend upon the
question of the heat of the water which acts upon it, but upon the depo-
sition of mineral matter in the rock by the water, and on the hardness
of the deposited minerals. No mineral matter need be brought in; the
induration requires only that the chemical constituents should reunite
into minerals of greater hardness. These alterations are always a pas-
sage from unstable to more stable compounds, in the conditions to which
the rocks are subjected. Glass is the most unstable form in which any
of the rock constituents can be; but the melaphyrs, from their origin

126 BULLETIN OF THE

and the conditions to which they were subjected at the time of con-
solidation, must have possessed a vast amount of glassy material.
Hence they were most liable to decomposition and alteration, which
might or might not result in induration. At Copper Falls no general
induration exists, except, for instance, where quartz has been deposited,
but at the Atlantic the induration is general. We have seen, that the
action of hot waters on the sandstone at Torch Lake gave rise to the
reverse of induration, as its action was that of removal, and not of
deposition.

The last form of copper deposit in the district visited by us is that
of the conglomerate mines. The beds of conglomerate are composed,
as before said, of rhyolitic, trachytic, and basaltic pebbles and detritus.
In some of these conglomerates, as the Calumet and Hecla, the cement
has been removed, and its place, or the original interspaces, filled with
copper. In some cases melaphyr pebbles have been largely removed,
and their places filled with copper, giving rise to boulder-like forms
(471). These conglomerates, then, are simply old sea-beach deposits,
and, like the amygdaloids and ash-beds, are not veins, and cannot prop-
erly be so called. They must of necessity partake of the characteristics
of their origin, the same as veins do of theirs.

The copper has been found throughout the district underlying heavy
beds of trap or a series of smaller ones; in fact, in the parts visited by
us, experience has shown that copper in abundance was only found
where trap in large amounts overlaid the vein or bed. The copper was
found filling, at the Calumet and Hecla mine, the joints of the overly-

-ing trap, and extending as a continuous sheet through fissures at right
angles to one another. At Copper Falls spikes of copper extend down-
wards out of the overhanging trap into the ash-bed. These are generally
large at the upper end, and pointed at the lower. Like them are the
secondary depositions of calcite, in this trap, in long, spike-like forms,
that here and elsewhere have been taken for fossils. These features
prove that the copper came from above downwards, and that it was de-
posited after the jointing of the trap. In fact, the evidence is- strong
that all the alteration and fissuring of the rocks, and the deposition of
the copper and associated minerals, took place after the western sand-
stone had been deposited. The above facts indicate that the copper was
derived from finely disseminated copper distributed throughout the lava,
as modern lavas have been known to contain it. If it was derived from
the sandstone, as advocated by Bauerman and later by Pumpelly, it
should be found in connection with the sandstone ; but such is not the

MUSEUM OF COMPARATIVE ZOOLOGY. B27

case. The farther from the sandstone, and the nearer the heavy beds of
trap, the larger have been the deposits of copper, e. g. Cliff, Central, and
Calumet and Hecla. The conglomerate of this last mine was not the
home of the copper ; it is simply the place where it has been deposited
by secondary agencies. The statement now kept up for some thirty
years in Dr. Dana’s works, that the copper is chiefly found at the junc-
tion of the sandstone and trap, is a good illustration of how an error once
in a text-book cannot be eradicated.

Conclusions.

The general geological structure of the region visited by us is, then,
in general, as follows. Beginning on the southeastern side of Keweenaw
Point we find a sandstone and conglomerate overlaid by melaphyr.
This melaphyr is again overlaid by sandstones and conglomerates,
principally the latter. The alternations of melaphyr, diabase, sandstone,
and conglomerate, with the melaphyr and diabase largely predominat-
ing, continue across the centre of the Point, forming its backbone. As
the northwestern side is approached, the sandstones and cenglomerates
increase, while the melaphyr and diabase diminish, until a purely sand-
stone formation is reached.

All these rocks taken together make one geological formation, and
have been laid down successively one upon the other, in order, going
from the east towards the west. These rocks are known to form the
same series by their conformably overlying one another. These traps
are old lava flows, spread out over the then existing surface along
a shore line. They have flowed the same as modern basaltic lavas do
under like conditions, and retain the same characters, except so far as
they have been modified by the agencies to which they have been sub-
jected since their outflow. They are known to be old lava flows by their
baking and indurating the immediately underlying rock, by their send-
ing dikes and tongues down into this rock, by their scoriaceous charac-
ter on the upper surface, by their signs of having flowed, and by their
microscopic characters. That they were laid down before the over-
lying rock is shown by their producing no effect upon it; by their
presenting on the upper surface only the irregularities and rounded
knobs that such surfaces are known to have, especially when they have
been worn ; by rounded pebbles and boulders of the underlying traps,
being enclosed in the overlying conglomerates; by the absence of frag-
ments of the overlying rock in the underlying one; and by the ab-

128 BULLETIN OF THE

sence of any characters showing intrusion of the traps between the dif-
ferent beds. The extent of these old lava flows, except as seen along
their upturned edges, is not known, for they have been followed by
mining along their incline some 2,100 feet only. Judging from their
length, their width must be considerable. In thickness they partake
of the same irregularities which any similar flow has. Locally the thin-
ner and more scoriaceous flows are known as ‘“‘ amygdaloids,” the thicker
and more compact ones as “traps,” and the thickest one on the western
side as “greenstone.” The difference between these several forms of
old basalt seems to be occasioned only by the variable amount of lava
erupted at different times, and the slightly different conditions to which
the flows were subjected.

Most of these old basalts are directly covered by succeeding flows,
following after greater or lesser intervals of time ; but part, as remarked
above, are covered by conglomerates and sandstones. These conglom-
erates and sandstones show, by the rounded and water-worn character
of their constituent pebbles and grains, that they are beach deposits.
The surface of the underlying basalt is smoothed as by water action.
The overlying conglomerate is made up at its base of basaltic mud and
pebbles, derived from the underlying rock, and mixed with the felsitic
mud and pebbles of which the conglomerates are chiefly composed. The
trappean mud and pebbles diminish, or are entirely wanting, as we re-
cede from the underlying trap. That the basalt is a metamorphosed
sandstone, as is often contended by mining mea, is disproved by the facts
given above, and by the further facts, that there is no gradual, but an
abrupt, passage between the two ; that all fragments of sandstone caught
up by the trap are baked and indurated by the heat, but show no signs
of passage ; and, lastly, that it would demand the conversion of an acidic
rock into a basic one.

From the conditions given above it would not be surprising to find the
lava flows locally limited at any point, and partially or even entirely de-
nuded, and replaced, in part or as a whole, by conglomerates and sand-
stones. This would depend, of course, upon the position of the shore
line, and upon the conditions to which the basalt was subjected during
the time of its flow, or since. A still greater variability is to be looked
for in the conglomerates and sandstones. All these conditions are to be
taken into consideration in the mining of these old lava flows and their
associated conglomerates.

In the Portage Lake and Keweenaw Point districts there are mined at
present four forms of deposits: —

MUSEUM OF COMPARATIVE ZOOLOGY. 129

1. Melaphyrs of an amygdaloidal character, known as “ amygdaloid”
mines, which have been subjected to hot-water action, and whose depos-
its of copper are ‘“‘bunchy” and irregular. These are in no sense veins
or lodes, and the Quincy and the Shelden and Columbian mines are
good examples.

2. Ash-bed mines, which are truly melaphyr or “ amygdaloid” ones,
but the melaphyr is of a more scoriaceous character, as was pointed
out above, of which the Copper Falls (in part) and the Atlantic mines
are examples.

3. The conglomerate or true bed mines, like the Calumet and Hecla.

4, The true fissure vein mines, like the Central, Phoenix, and Copper
Falls (in part).

The first two forms should be classed as one.

It is an established rule that a mineral vein, in passing from one bed
of rock into another of a different nature, is apt to vary in width and con-
tents. Such variations in dimensions and gangue have been repeatedly
found in this district, as the different beds are comparatively narrow.
As might be expected, the variation is not so strongly marked in the
different melaphyrs, since they are all rocks of the same composition and
origin, differing only in texture, thickness, and crystallization. One and
the same vein may then vary in width, from a mere seam to thirty or
more feet, as is the case with the ‘Owl Creek Vein,” as mined at Cop-
per Falls. Under these conditions one cannot judge with any certainty,
from the appearance of the vein at one point, what will be its width or
character at another. The decision must be based on probabilities only.
In places the fissure may be filled with true vein material, while in other
parts, especially in the wider portions, it may be filled with fragments
of the melaphyr, cemented together by vein matter. The width of the
vein will depend largely upon the readiness with which the country rock
yielded to the crushing and grinding force, and to the action of the per-
colating waters. We should expect, then, the veins to be mere nominal
fissures in the sandstones, conglomerates, and heavy “ greenstone,” but
to be more or less well marked in the “‘amygdaloids” and “traps.”

The filling of the veins and of the cavities in the melaphyrs, it ap-
pears, was accomplished by the same agencies. The amygdaloidal strue-
ture of the melaphyr is owing to the filling with mineral matter, with
greater or less completeness, gas cavities formed at the time of the lava
flow. Besides the true amygdaloidal structure, there are numerous
cases of pseudo-amygdaloidal structure. This last arises from the alter-
ation of the formerly solid parts of the melaphyr, and is to be found not

VOL. VII. — NO. 1. 9

130 BULLETIN OF THE

only in the compact portions (lower) of the rock, but also in the scoria-
ceous parts (upper). These amygdules and pseudo-amygdules are com-
posed of quartz, calcite, epidote, prehnite, laumontite, analcite, apophyllite,
datolite, chlorite, delessite, etc., etc. The constituents of these minerals
were derived from the decomposition of the melaphyr, and deposited
through the agency of the percolating waters. The vein materials are
the same as those of the amygdules, and they are of like derivation and
deposition. The copper is found forming a constituent part of the amyg-
dules in many places, as well as of the vein-stone, and it would seem to
have been deposited ina like manner. Until we know more about the
occurrence of the copper, all theories regarding its origin should be held
with a loose grasp, and dropped as the facts developed may require
thereafter. It is held by some that the copper was derived from solu-
tions of the metal in sea-water, precipitated by decaying organic matter,
and accumulated in the sandstones, shales, and conglomerates of the
series. It was then taken up by the percolating waters, and deposited
in the places in which it is now found. A second view is that the cop-
per was originally finely disseminated through the lava at the time of its
outflow, and has since been locally concentrated by percolating waters
in the amygdules, veins, and conglomerate beds. The writer inclines to
the latter view, believing that this theory is more in accordance with
the facts observed by him than the former one. 'The final concentra-
tion and precipitation seem to be connected in some way with the ox-
ides of iron, which are abundant in the melaphyr and in the detritus of
it and of the felsite pebbles, which form the principal portion of the con-
glomerate. The copper seems to have needed for its deposition some of
the following conditions: rocks that were porous and cellular; those
whose parts were easily removed by the percolating waters, as the mud
forming the cementing material of the conglomerates ; the open spaces of
veins and fissures ; and rocks acted upon by hot waters. The copper,
when not distributed through the whole bed, is found principally in the
upper portion. Whatever may be our views respecting the sources of
the copper, it is evident that it was deposited by aqueous agencies, and
that the general course of the solution was downwards. The best vein-
stones, so far as observed, are datolite, prehnite, and calcite. Laumon-
tite does not seem to have much mass copper associated with it. While
large masses of copper were seen at the Central mine associated with
calcite, a similar association is rarely found in the Owl Creek vein at
Copper Falls. The best vein-stone there has been datolite. The preh-
nite here seems in depth to yield to datolite.

MUSEUM OF COMPARATIVE ZOOLOGY. 131

The theories of the igneous origin of the veins, and of the igneous
deposition of the copper in them, have been so ably refuted in the vari-
ous papers referred to here that it is unnecessary to discuss them ; but
owing to the great weight of Professor Dana’s name, we cannot pass
over his theory without saying that the supposed facts on which it is
based do not exist in the Copper district, he having raised the super-
structure on the errors of Messrs. Houghton and Jackson, never having
visited the region himself.

As in the Iron district, so in the Copper district, the writings of
Messrs. Foster and Whitney remain the best and most accurate expo-
nents, as they were the first of value, of the geology of the country, and
of the ore deposits studied by us, so far as they were known at that time.
All work since, so far as it stands the test of examination, sustains their
views and establishes the accuracy of their observations, except in a few
particulars. Mr. A. R. Marvine’s work stands next in order of value
and geological ability shown.

Professor Pumpelly deserves all credit for his microscopic examina-
tions of the old basaltic rocks of the district, and for the extent and
thoroughness with which he has applied and carried out the investiga-
tions and theories of Messrs. Whitney, Miiller, and Bauerman, in his
“ Paragenesis and Derivation of Copper and its Associates on Keweenaw
Point”; but his stratigraphical work was not worthy of the name, and
served only to obscure the true relations of the rocks. The volcanic
origin of the rocks was proved by Marvine five years before, by Foster
and Whitney twenty-eight years before, and announced by Hubbard
thirty-two years before Pumpelly accepted it.

Our work proves that the Keweenawan system has no foundation
except in insufficient observation and the application of stratigraphi-
cal methods and assumptions that will not bear examination. The
difficulty here, as in the Iron district, has been in the methods, and

in the assumption that certain observations proved that which they
did not.

I desire to extend my thanks for favors received while in the Iron and
Copper districts to Charles E. Wright, M. E., State Commissioner of Min-
eral Statistics; Per Larsen, M. E. of the Jackson mine; Agents C. H. Hall,
of the Lake Superior mine, William Sedgwick, of the Barnum, D.- H.
Bacon, of the McComber ; Capts. James Pascoe, of the Champion, and
Peter Pascoe, of the Republic ; also to Mr. David Morgan, President of
the Republic Iron Company ; to Captain Cliff, and L, G. Emerson, M. E.

132 BULLETIN OF THE

of the Quincy ; Messrs. Cooper and Patch, of the Detroit and Portage
Lake smelting-works ; G. D. Bolton, M. E., and Capts. Hoatson, Dan-
iel, and Wells, of the Calumet and Hecla; Mr. Frank Osburn, of the
Troy Polytechnic School; Agent Delano, of the Phoenix; and espe-
cially to Agent B. F. Emerson and Captain John H. Moyle, of the .
Copper Falls mine; and others. -

CAMBRIDGE, Mass., May 18th, 1880.

MUSEUM OF COMPARATIVE ZOOLOGY. 133

APPENDIX.

List of Papers and Works relating to the Geology, Mineralogy, and Physi-
cal Geography of Lake Superior.

Tue writer does not claim that this list contains all that has been
written on these subjects relating to Lake Superior, for it is simply the
outgrowth of a desire, arising after part of the body of this paper was
written, to save others the trouble of doing over again the work that he
had already done. It is not intended as a bebliography in the approved
modern sense, but simply to serve as a stepping-stone to those who may
hereafter desire to take up the study of this most interesting region.
Papers and works, which from their titles appear to belong to different
departments or to other localities, have been given, when matter re-
lating to these subjects or this region, as the case may be, has been
found in them. All papers given here that the writer has not seen are
marked with an asterisk (*).

In the preceding text, in quoting from the various authors referred to,
the intention has been to make the spelling, punctuation, and italics
identical with the originals, which accounts for certain peculiarities that
the reader will observe.

Agassiz, Alexander.

On the Position of the Sandstone of the Southern Slope of a Portion of
Keweenaw Point, Lake Superior. Proc. Bost. Soc. Nat. Hist., 1867, xi.
244 — 246.

Agassiz, Louis.

On the Fishes of Lake Superior. Proc. Am. Assoc. Adv. Sci., 1848, i.
30-32.

The Terraces and Ancient River Bars, Drift, Boulders, and Polished Sur-
faces of Lake Superior. Proc. Am. Assoc. Adv. Sci., 1848, i. 68 —70.

On the Origin of the Actual Outlines of Lake Superior. Proc. Am. Assoc.
Adv. Sci., 1848, i. 79.

Remarks upon the Unconformability of the Paleozoic Formations of the
United States. Proc. Am. Assoc. Adv. Sci., 1851, vi. 254.

On Marcou’s “Geology of North America.” Am. Jour. Sci., 1859, (2,)
xxvil. 134-137.

134. BULLETIN OF THE

Agassiz, Louis, azd J. Elliot Cabot.

Lake Superior. Its Physical Characters, Vegetation, ana Animals. Boston,
March, 1850. 428 pp. Edinburgh New Phil. Jour., 1850, (2,) xlix. 25
— 33, 398, 399; Am. Jour. Sci., 1850, (2,) x. 88-101.

Akermann, H. W.

Die Kupterfuhrenden Schichten am Lake Superior. Sitzungs-Berichte der

naturwissenschaftlichen Gesellschaft Isis in Dresden, 1875, pp. 101-105.
Alger, Francis.

Pseudomorphie Crystal of Native Copper from Copper Falls Mine, Lake Su-

perior. Proc. Bost. Soc. Nat. Hist., 1861, viii. 170, 171.
Andrews, Israel D.

On the Trade and Commerce of the British North American Colonies, and
upon the Trade of the Great Lakes and Rivers. Sen. Does., 1st Sess. 32d
Cong., 1851-52, xi., No. 112, 906 pp. Contains a report by C. T.
Jackson.

Anonymous.

Michigan: its Commerce and Resources. Hunt’s Merch. Mag., 1842, vi.
333 — 348.

The Copper Mines of Lake Superior. Hunt’s Merch. Mag., 1846, xiv. 439 -
443.

Ancient Mining on Lake Superior. Hunt’s Merch. Mag., 1848, xix. 663.

Elevation of an Island in Lake Superior. Ann. of Sei. Discov., 1851, 255.

The Copper and Tron Region of Lake Superior. Review of the Work of
F.C. L. Koch. Mining Mag., New York, 1853, (1,) 261-268.

The Silver of the Lake Superior Mineral Region. Mining Mag., New York,
1853, (1,) i. 447 — 454, 612, 618; 11. 82, 83.

Notice of a Geological Map of the United States, ete., by Jules Marcou. Am.
Jour. Sci., 1854, (2,) xvii. 199 — 206.

Mineral Wealth of the Lake Superior District. Ann. of Sci. Dise., 1855,
309, 310.

Mineral Region of Lake Superior. Mining Mag., 1858, (1,) il. 248— 252.

Great Mass of Native Copper. Min. and Smelt. Mag., 1864, vi. 25, 26; Am.
Jour. Sci., 1864, (2,) xxxvii. 431.

Canada. A Geographical, Agricultural, and Mineralogical Sketch. Published
by authority of the Bureau of Agriculture. Quebec, 1865, 33 pp.

Barnes, George O.

See Charles T. Jackson.

Bartlit, William, ad David Tod.

Mineral Regions of Lake Superior. Senate Does., Ist Sess. 29th Cong.,
1845 — 46, iv., No. 160, pp. 20 — 25.

Bayfield, H. W.

Outlines of the Geology of Lake Superior. Trans. of the Lit. and Hist. Soc.
of Quebec, 1829, 1. 1 — 43.

On the Junction of the Transition and Primary Rocks of Canada and Labra-
dor. Quart. Jour. Geol. Soc., 1845, 1. 450 - 459.

MUSEUM OF COMPARATIVE ZOOLOGY. rea

Beaumont, Elie de.

Age of the Sandstone of Lake Superior. Bull. Soc. Geol. France, 1849 - 50,
(2,) vii. 209.

See Louis Cordier.

Bell, Robert.

Geology of Lake Superior and Nipigon. Geol. of Canada, 1866 - 69, pp.
313-364.

Report on the Country North of Lake Superior, between the Nipigon and
Michipicoten Rivers. Geol. Surv. of Canada, Rep. of Prog., Ottawa,
1870-71, pp. 322 - 351.

Report on the Country between Lake Superior and the Albany River. Geol.
Surv. of Canada, Rep. of Prog., Montreal, 1871-72, pp. 100-114.

Report on the Country between Lake Superior and Lake Winipeg. Geol.
Surv. of Canada, Rep. of Prog., Montreal, 1872-73, pp. 87-111.

The Mineral Region of Lake Superior. Canadian Nat. and Geol., 1875, (2,)
vil. 49-51.

Report on an Exploration in 1875, between James Bay and Lakes Superior and
Huron. Geol. Surv. of Canada, Rep. of Prog., 1875-76, pp. 294-342.

Report on Geological Researches North of Lake Huron and East of Lake Su-
perior. Geol. Survey of Canada, Rep. of Prog., 1876-77, pp. 193-220.

Bell, William H.

Mineral Lands of the Upper Mississippi. Executive Docs., lst Sess. 28th

Cong., 1843 — 44, iii., No. 43, 52 pp.
Bigsby, John J.

A List of Minerals and Organic Remains occurring in the Canadas. Am.
Jour. Sci., 1824, (1,) vill. 60-88. |

Notes on the Geography and Geology of Lake Superior. Quart. Jour. Sci.
and Arts, 1824-25, xviii. 1-34, 228 — 269.

On the Erratics of Canada. Quart. Jour. Geol. Soc., 1851, vii. 215 -238,
with map.

On the Physical Geography, Geology, and Commercial Resources of Lake
Superior. Edinburgh New Phil. Jour., 1852, lili, 55-62; Am. Jour.
Sei., 1852, (2,) xiv. 138 ; Proc. of the Royal Institution, 1852, i. 154-162.

On the Organic Contents of the Older Metamorphic Rocks: a Review and a
Classification. Edinburgh New Phil. Jour., 1863, (2,) xvii. 171-197.
Billings, E.
General Geology. Canadian Nat. and Geol., 1856, i. 1-25.
Blake, William P.
Review of a Portion of the Geological Map of United States and British
Provinces, by Jules Marcou. Am. Jour. Sci., 1856, (2,) xxii. 383-388.
The Mass Copper of Lake Superior Mines and the Method of Mining it.
Trans. Am. Inst. Min. Engineers, 1875, iv. 110-112.
Blandy, John F.
Topography with especial Reference to the Lake Superior Copper District.
Trans. Am. Inst. Min. Engineers, 1871, i. 75-82.

136 BULLETIN OF THE

Stamp Mills of Lake Superior. Trans. Am. Inst. Min. Eng., 1874, ii
208 - 215.

The Lake Superior Copper Rocks in Pennsylvania. Trans. Am. Inst. Min.
Eng., 1879, vii. 331 -— 333, 336.

See C. P. Williams.

Borie, Jules.

* Notice sur le Lac Supérieur et ses Mines de Cuivre de la Rive Americaine.
St. Etienne Bull. Soc. Industr., 1860, vi. 233-284; vii. 185-252; viii.
271, 272; Allgem. Berg. u. Hitten. Zeitung, 1862, iv. 448 —450, 457 -
460, 469-471.

Bradley, Frank H.
On a Geological Chart of the United States east of the Rocky Mountains, and
of Canada. Am. Jour. Sci., 1876, (3,) xil. 286-291.
Bristol, T. W.
See Jacob Houghton, Jr.
Brooks, =. B:

Geological Survey of Michigan, with Maps, 1869-1873, i.; Part L., Iron-
bearing Rocks, 319 pp.; Part II., Copper-bearing Rocks, R. Pumpelly
and A. R. Marvine, 143 pp.; Part ILL, Paleozoic Rocks, Charles Rom-
inger, 105 pp; ii. 298 pp., contains papers by Messrs. Brooks, Julien,
Wright, Jenney, and Tuttle.

On the youngest Huronian Rocks south of Lake Superior and the Age of the
Copper-bearing Series. Am. Jour. Sci., 1876, (3,) xi. 206 -211.

Classified List of Rocks observed in the Huronian Series, south of Lake Su-
perior, ete. Am. Jour. Sci., 1876, (3,) xii. 194-204.

See T. C. Chamberlain.

Brooks, T. B., and R. Pumpelly.

On the Age of the Copper-bearing Rocks of Lake Superior. Am. Jour. Sci.,

1872, (3,) ii. 428 -— 432.
Brown, A. J.

The Formation of Fissures and the Origin of their Mineral Contents. Trans.

Am. Inst. Min. Eng., 1874, i. 215-219.

Burt, William A., azd Bela Hubbard.

Reports of William A. Burt and Bela, Hubbard on the Geography, Topogra-
phy, and Geology of the U.S. Surveys of the Mineral Region of the South
Shore of Lake Superior for 1845, ete. In the “ Mineral Region of Lake
Superior,” by J. Houghton, Jr., and T. W. Bristol. Detroit, 1846. Sen-
ate Docs., Ist Sess. 29th Cong., 1845-46, vii. Doc. 357, 29 pp.; Ist
Sess. 3lst Cong., 1849-50, ii. 803-842.

Geology and Topography of the District south of Lake Superior, 1846. Sen-
ate Does., 1st Sess. 31st Cong., 1849-50, iil. 842 - 932.

See Charles T. Jackson, and Jacob Houghton, Jr.

Cabot, J. Elliot.
See Louis Agassiz.

MUSEUM OF COMPARATIVE ZOOLOGY. 137

Callender, John A.
The Lake Superior Copper Mines. Mining Mag., 1854, ii. 249 - 253.
Calvert, John.
On the Decomposition of Rocks and the Recomposition of their Metallic Con-
stituents. Mining Mag., 1854, ii, 371-376.
Campbell, J. B.
See John Stockton.

Cass, Lewis.
Letter from Governor Cass, of Michigan, on the Advantage of Purchasing
the Country upon Lake Superior where Copper has been found. Senate
Does., 2d Sess. 18th Cong., 1824-25, No. 19, 2 pp.

Chamberlain, T. C.
Geology of Wisconsin, 1873 - 1877, II., 768 pp. with maps. Reports by
Messrs. I. A. Lapham, O. W. Wight, T. C. Chamberlain, R. D. Irving,
C. E. Wright, and Moses Strong. 1873-1879, ILI., 763 pp. with maps.
Reports by Messrs. R. D. Irving, R. Pumpelly, A. A. Julien, C. E.
Wright, E. T. Sweet, T. B. Brooks, A. Wichmann, T. C. Chamberlain,
and T. S. Hunt.

Channing, William T.
See Charles T. Jackson.

Chapman, E. J.

Popular Exposition of the Minerals and Geology of Canada. Canadian Jour.,
1860, {2,) v. 1-19, 168-182, 517-531; 1861, vi. 149-165, 425 - 455,
500-518; 1862, vii. 108-121; 1863, viii. 17-33, 111-127, 185 - 216,
437-462; 1864, ix. 1-10.

On Some Minerals from Lake Superior. Canadian Jour., 1865, (2,) x. 406-
411.

On Some Minerals from Lake Superior. Phil. Mag., 1866, (4,) xxxi. 176-
180.

Notes on the Silver Locations of Thunder Bay. Canadian Jour., 1869, (2,)
xii. 218 — 226.

An Outline of the Geology of Ontario, based on a Subdivision of the Province
into six Natural Districts. Canadian Jour., 1875, (2,) 580-588.

On the Leading Geological Areas of Canada. Canadian Jour., 1876, (2,) xv.
92-122.

Chester, Albert H.

On the Percentage of Iron in Certain Ores. Trans. Am. Inst. Min. Eng.,

1875, iv. 219.

Clarke, Robert D.
Notes from the Copper Region. Harper’s New Monthly Mag., 1853, vi.
433—448, 577-588.
Glarkep-r.2C-
The Great Lakes. Atlantic Monthly, 1861, vii. 226-235.

138 BULLETIN OF THE

Claypole, E. W.

On the Pre-Glacial Geography of the Region of the Great Lakes. Canadian
Nat. and Geol., 1878, (2,) vii. 187 — 206.

Pre-Glacial Formation of the Beds of the Great American Lakes. Canadian
Nat. and Geol., 1879, ix. 213 — 227.

Clinton, De Witt. :

On Certain Phenomena of the Great Lakes of America. Trans. New York

Lit. and Phil. Soc., i, Part I. 1-383.
Cordier, Louis.

Note sur une Masse de Cuivre natif provenant des Rives du Lac Supérieur, aux
Etats-Unis d’Amérique. Louis Cordier and Elie de Beaumont. Comptes
Rendus, 1849, xxviii. 161-163; Leonhard’s Jahrbuch, 1849, p. 470.

Courtis, W. M.

The North Shore of Lake Superior as a Mineral-bearing District. Trans.

Am. Inst. Min. Eng., 1877, v. 473 - 487.
Credner, Hermann.

Die Gliederung der eozoischen (vorsilurischen) Formationsgruppe Nord-
Amerikas. Zeits. Gesam. Naturwiss., Giebel, 1868, xxxii. 353-405.

Beschreibung einiger charakteristischer Vorkommen des gediegenen Kupfers
auf Keweenaw Point am Oberens See Nord-Amerika’s. Leonhard’s Jahr-
buch, 1869, 1-14.

Die vorsilurischen Gebilde der ‘‘ Obern Halbinsel von Michigan” in Nord-
Amerika. Zeit. Deut. Geol. Gesell., 1869, xxi. 516-554.

Gewaltige Kupfermassen am Lake Superior. Leonhard’s Jahrbuch, 1870, 86.

Ueber nordamerikanische Schieferporphyroide. Leonhard’s Jahrbuch, 1870,
970-984.

Elemente der Geologie. *I1st ed. 1872, *2d ed. 1872, 3d ed. 1876, 699 pp.,
*4th ed. 1880.

Crosby, William O. :
Ona Possible Origin of Petrosiliceous Rocks. Proc. Bost. Soc. Nat. Hist.,
1879, xx. 160 - 169.
Contributions to the Geology of Eastern Massachusetts. Occasional Papers
of the Bost. Soc. Nat. Hist., 1880, iii. 286 pp., with map.

Cunningham, Walter.
Report of Walter Cunningham, late Mineral Agent on Lake Superior. Jan.
8, 1845. Senate Does., 28th Cong. 2d Sess., 1844-45, vii., No. 98,
5 pp-
Dana, James D.
System of Mineralogy. Ist ed., New Haven, 1837, 671 pp.; 2d ed., New
York, 1844, 633 pp.; 3d ed., New York, 1850, 711 pp.; 4th ed., New
York, 1854, 853 pp.; 5th ed., New York, 1868, 827 pp.
Manual of Mineralogy. New Haven, 1857, 456 pp.
Review of Marcou’s “Geology of North America.” Am, Jour. Sci., (2,)
1858, xxvi. 323 -333.

MUSEUM OF COMPARATIVE ZOOLOGY. 139

Reply to Prof. Agassiz on Marcou’s “Geology of North America.” Am.
Jour. Sci., 1859, xxvii. 137 — 140.
Manual of Geology. New York. Ist ed., 1862, 800 pp.; 2d ed., 1874,
828 pp.; 3d ed., 1880, 911 pp.
Manual of Mineralogy and Lithology. New York, 1878, 474 pp.
Davies, D. C.
Metalliferous Minerals and Mining, London, 1880, 432 pp. ; Copper Rocks,
pp. 149-164; Iron Ores, pp. 274, 275.
Dawson, John W.
On the Geological Structure and Mineral Deposits of the Promontory of
Maimanse, L. Sup. Canadian Nat. and Geol., 1857, ii. 1 - 12.
Dawson, S. J.
Report on the Exploration of the Country between Lake Superior and the Red
River Settlement, ete. S. J. Dawson and H. Y. Hind. Toronto, 1858.
424 pp., with maps.
Report on the Exploration of the Country between Lake Superior and the
Red River Settlement. Toronto, 1859. 45 pp., with maps.
Papers relative to the Exploration of the Country between Lake Superior and
the Red River Settlement. S.J. Dawson, Henry Y. Hind, and others.
Blue Book, 1859, Sess. 2, xxii., 163 pp., with maps.
’ D’Archiac, A.
Progrés de la Géologie, 1848, ii., Terrain Quaternaire, 369, 370; viil., For-
mation Triassique, 635 — 644.
Dearborn, H. A. S.
On the Variations of Level in the Great North American Lakes, with Docu-
ments. Am. Jour. Sci., 1829, (1,) xvi. 78 - 94.
Delafield, Joseph.
Notice of new Localities of Simple Minerals along the North Coast of Lake
Superior, ete. Ann. Lyc. of Nat. Hist., 1824, i. 79-81.
Delesse, A. .
Mines de Fer des Etats-Unis. Annales des Mines, 1857, (5,) xii. 805 —841.
Deroux, H.
Die Kupfergruben des Oberen See’s (Lake Superior). * Journal des Mines,
1860, vu.; Berg. u. Hiitten. Zeit., 1861, pp. 305-307, 329 - 331.
Desor, Edward. f
Rain-Drop and Air-Bubble Impressions. Edward Desor and J. D. Whitney.
Proc. Bost. Soc. Nat. Hist., 1849, iii. 200, 201; 1851, iv. 131-133;
Proc. Am. Assoc. Adv. Sci., 1851, v. 74.
Sand Dunes and Ripple Marks on Lake Superior. Proc. Bost. Soc. Nat.
Hist., 1849, iii. 207, 208 ; 1851, iv. 41, 42.
Des Alluvions Marines et Lacustres, et du Terrain erratique de l’Amérique du
Nord. Bull. Soc. Geol. France, 1849-50, (2,) vii. 623-630. Sur les
Drifts de ?Amérique du Nord, 1851-52, ix. 94-96. Sur la Carte géo-
logique du Lac Supérieur, ix. 280, 281. Note sur le Terrain quaternaire

140 BULLETIN OF THE

de l Amérique du Nord, 1851-52, ix. 281-285. Str le Terren de Transi-
tion et quaternaire des Etats Unis, ix. 312-322. Amn. Sci. Discov.,
1853, 269 — 272.
Clay and Drift Deposits on Lake Superior. Proc. Bost. Soc. Nat. Hist.,
1850, iii. 235, 236; Am. Jour. Sci., 1852 (2,) xiii. 93-109; Zeit. Deut.
Geol. Gesell., 1852, iv. 669 — 679.
Drift Strize on Lakes Superior and Michigan. Proce. Bost. Soc. Nat. Hist.,
1850, iii. 242.
“Cross Formation ” of Sandstone on Lake Superior. Proc. Bost. Soc. Nat.
Hist., 1850, iii. 341.
Parallelism of Mountain Chains in America. Proc. Bost. Soc. Nat. Hist.,
1850, ii. 380 - 382; Am. Jour. Sci., 1851, (2,) xii. 118 — 120.
Origin of the Drift of Lake Superior. Proc. Bost. Soc. Nat. Hist., 1851, iv.
28, 29.
Dunes on the Upper American Lakes. Proc. Bost. Soc. Nat. Hist., 1851,
iv. 41, 42.
Lake Superior. On the Silurian Rocks of the Lake Superior Land District.
Proc. Am. Assoc. Adv. Sci., 1851, v. 64, 65.
Post-Pliocene of the Southern States and its Relation to the Laurentian
of the North and the Deposits of the Valley of the Mississippi. Am. Jour.
Sci., 1852, (2,) xiv. 49-59.
See Foster and Whitney.
Dieffenbach, Otto.
Bemerkungen tiber den Kupferbergbau in den Vereinigten Staaten von Nord-
Amerika. Berg. u. Hiitten. Zeit., 1858, pp. 47, 48, 66-68, 75, 76.
Disturnell, John.
The Great Lakes or Inland Seas of America. New York, 1863, 192 pp.
and map.
Douglas, James.
The Native Copper Mines of Lake Superior. Quart. Jour. Sci., 1874, xi.
162-180; Canadian Nat. and Geol., 1874, (2,) vu. 8318-336.
Dupee, J. A.
Ash-bed of the Phcenix Mine. Proc. Bost. Soc. Nat. Hist., 1855, v. 279,

280.
Dutton, T. R.
Observation on the Basaltic Formation on the Northern Shore of Lake Supe-
rior. Am. Jour. Sci., (2,) 1847, iv. 118, 119.,
Eames, Henry H.
* Geological Reconnoissance of the Northern, Middle, and other Counties of
Minnesota. St. Paul, 1866. 58 pp.
Report of the State Geologist, Henry H. Eames, on the Metalliferous Region
bordering on Lake Superior. St. Paul, 1866, 28 pp.
Egleston, Thomas.
Boracic Acid in Lake Superior Iron Ores. Trans. Am. Inst. Min. Eng., 1876,
v. 131, 182.

MUSEUM OF COMPARATIVE ZOOLOGY. 141

Copper Mining ou Lake Superior. Trans. Am. Inst. Min. Eng., 1877, vi.
275 - 312.

The Conglomerates of Lake Superior, and the Methods of Dressing Copper.
Trans. Am. Inst. Min. Eng., 1877, v. 606 - 611.

Emmons, Ebenezer.

Copper Mines of Lake Superior. American Geology, Albany, 1855, pp. 171

-173.
Foster, J. W.

On Certain Phenomena connected with the Rise and Fall of the Waters of
the Northern Lakes. Proc. Am. Acad., 1849, i. 131-136; Ann. Sci.
Discov., 1850, pp. 245, 246; Edinburgh New Phil. Jour., 1850, xlix. 172.

Catalogue of Rocks, Minerals, ete., collected by J. W. Foster. Smithsonian
Report, 1854, 384 - 387.

On the Antiquity of Man in North America. Trans. Chicago Acad. Sci.,
1867 — 69, pp. 227 — 257.

Ancient Mining by the Mound-builders, in the “ Pre-historic Races of the
United States.” Chicago, 1873, pp. 361 - 374.

Foster, J. W., azd J. P. Kimball.

Geology and Metallurgy of the lron Ores of Lake Superior. New York, 1865,

97 pp., with maps.

Foster, J. W., azd J. D. Whitney.

Synopsis of the Explorations of the Geological Corps in the Lake Superior
Land District in the Northern Peninsula of Michigan. Senate Docs.,
1849 — 50, ili., No. 5, 605 - 626.

Report on the Geology and Topography of the Lake Superior Land District.
Part I., Copper Lands. Executive Docs., 1st Sess. 31st Cong., 1849 - 50,
ix., No. 69, 244 pp. with map; Am. Jour. Sci., 1851, (2,) xii. 222-239.
Part II., The Iron Region, together with the General Geology, contains
additional Reports by James Hall, Edward Desor, Charles Whittlesey,
and W. D. Whitney. Senate Does., Special Sess. 32d Cong., 1851, iii.,
No. 4, 406 pp. with maps; Am. Jour. Sci., 1853, (2,) xv. 295, 296; 1854,
(2,) xvil. 11-38, 181-194.

Report on the Iron District of Lake Superior. Senate Does., 2d Sess. 31st
Cong., 1850-51, ii., No. 2, 147 - 152.

Apercgu de lensemble des Terrains Siluriens du Lac Supérieur. Bull. Soe.
Géol. France, 1850, (2,) viii. 89-100.

On the Azoic System, as developed in the Lake Superior Land District. Proe.
Am. Assoe: Adv. Sci., 1851, v. 4-7.

On the Age of the Sandstone of Lake Superior, with a Description of the Phe-
nomena of the Association of Igneous Rocks. Proc. Am. Assoc. Adv.
Sci., 1851, v. 22-38.

On the Different Systems of Elevation which have given Configuration to
North America, with an attempt to Identify them with those of Europe.
Proc. Am. Assoc. Ady. Sci., 1851, v. 136-151.

142 BULLETIN OF THE

On the Origin and Stratigraphical Relations of the Trappean Rocks of Lake
Superior. Ann. Sci. Discov., 1861, 285.
Frazer, Persifor, Jr.
The Lake Superior Copper Rocks in Pennsylvania. Trans. Am. Inst. Min.
Eng., 1879, vii. 336 -339.
Fullerton, T. M. !
St. Louis River. Minn. Hist. Coll., 1850-56, i. 189 - 143.
Geinitz, H. B.
Alexander Winchell: iitber geologische Verhaltnisse in Michigan. Leonhard’s
Jahrbuch, 1876, pp. 438 - 440.
Genth, Frederick A.
Contributions to Mineralogy. Am. Jour. Sci., 1859, (2,) xxvii. 400; xxviii.
246-255; 1862, xxxiil. 190-206.
Gray, A. B..
Report of A. B. Gray on Mineral Lands of Lake Superior. Executive Docs.,
Ist Sess. 29th Cong., 1845 - 46, vii., No. 211, 23 pp., with map.
See John Stockton.
Greeley, Horace.
Process of Working a Lake Superior Copper Mine. Hunt’s Merch. Mag.,
1848, xix. 559, 560. :
Hager, A. D.
Ancient Mining on the Shores of Lake Superior. Atlantic Monthly, 1865,
xv. 808 - 315.
Hall, C. W.
See S. F. Peckham aad N. H. Winchell.
Hall, James.
On the Silurian System of the Lake Superior Region. Am. Jour. Sci., 1854,
(2,) xvii. 181 - 194.
On the Potsdam Sandstone. Sixteenth Ann. Rep. of the Regents of the
Univ. of New York. Appendix D. Albany, 1863, pp. 210-220.
See Foster and Whitney.
Hanchett, Augustus H.
* Report on the Geology of Minnesota. 1864, 82 pp.
Hayes, A. A.
Datolite from Lake Superior. Proc. Bost. Soc. Nat Hist., 1859, vii. 348,
349, 354; 1862, vill. 62-64.
Hector, James.
On the Geology of the Country between Lake Superior and the Pacific Ocean,
ete. Quart. Jour. Geol. Soc., 1861, xvii. 888-445.
See John Palliser.
Henwood, William J.
On the Native Copper of Lake Superior. On Metalliferous Deposits and
Subterranean Temperature. Part. I, pp. 885-489; Trans. Geol. Soc. of
Cornwall, vol. viii., Part I., 1871, pp. 385 — 489.

MUSEUM OF COMPARATIVE ZOOLOGY. 143

Hill, S. W.
Copper Falls Mine. Mining Mag., 1854, il. 668 - 672.
Hind, Henry Y.
Report on the Exploration of the Country between Lake Superior and the
Red River Settlement. 1858, 425 pp., with maps.
Report on the Assiniboine and Saskatchewan Exploring Expedition. 1859,
201 pp., with maps.
Narrative of the Canadian Exploring Expeditions. London, 1860, i. 494 pp.,
il. 472 pp.
See 8. J. Dawson.

Hitchcock, Edward.
Outline of the Geology of the Globe. Boston, 1853, 162 pp., with maps.

Hodge, James T.
On the Mineral Region of Lake Superior. Proc. Am. Assoc. Adv. Sci., 1849,

ii. 301-308; Amn. Sci. Discov., 1850, 260, 261.

Houghton, Douglass.

Report of Doctor Houghton on the Copper of Lake Superior. Nov. 14, 1831.
In the Discovery of the Source of the Mississippi, by H. R. Schooleraft,
pp. 287 - 292. New York, 1834.

First Annual Report on the Geology of Michigan, 1838. Lanman’s History
of Michigan, 1839, 347-366; Am. Jour. Sci., 1838, (1,) xxxiv. 190 - 192.

Second Annual Report of the State Geologist. Senate Does., Michigan, 1839,
264-294; Am. Jour. Sci., 1841, (1,) xl. 136.

Third Annual Report of the State Geologist, 1840. Senate Does., Michigan,
1840, 66-157.

Fourth Annual Report of the State Geologist. Joint Docs., Michigan, 1841,
472 - 607.

Fifth Annual Report of the State Geologist. Joint Docs., Michigan, 1842,
436-441. .

Metalliferous Ves of the Northern Peninsula of Michigan. Am. Jour.
Sci., 1841, (1,) xli. 188-186; Trans. of the Assoc. Am. Geol. and Nat.,
1840-42, pp. 35 - 38; Edinburgh New Phil. Jour., 1842, xxxiii. 201, 202.

Copper on Lake Superior. Am. Jour. Sci., 1844, (1,) xlvi. 107, 132.

See T. B. Brooks, J. Houghton, Jr., J. H. Relfe, axd H. R. Schooleraft.

Houghton, Jacob, Jr.

The Ancient Copper Miners of Lake Superior. Iron, 1876, (N. S.,) viii. 168,
169, 199; Swineford’s Copper, Iron, and other Material Interests of Lake
Superior. Marquette, 1876, pp. 78 - 89.

Houghton, Jacob, Jr., axd T. W. Bristol.

Mineral Region of Lake Superior. Detroit, 1846, 109 pp. and map. Con-

tains Reports by Messrs. Burt, Hubbard, D. Houghton, and Stannard.
Hubbard, Bela.
See William A. Burt, J. Houghton, Jr., axd C. T. Jackson.

144 BULLETIN OF THE

Hughes, G. W.
The Working of Copper Ore. Senate Does., lst Sess. 28th Cong., 1848 - 44,
v., No. 291, 58 pp.
Hunt, T. Sterry.

On some Ores of Nickel from Lake Superior. Am. Jour. Sci., 1855, (2,) xix.
417, 418.

On some Points in American Geology. Am. Jour. Sci., 1861, xxxi. 392 -
414; Canadian Nat and Geol., 1861, vi. 81-105.

Contributions to Lithology. Am. Jour. Sci., 1864, (2,) xxxvii. 248 — 266;
xxxvill. 91-104, 174-185.

The Origin of Metalliferous Deposits. Trans. Am. Inst. Min. Eng., 1872,

i. 413 — 426.
The Geognostical History of the Metals. Trans. Am. Inst. Min. Eng., 1873,
i. 331-336.

Geognosy of the Appalachians and the Origin of Crystalline Rocks. Proc.
Am. Assoc. Adv. Sci., 1871, xx. 1-59.

The Geology of the North Shore of Lake Superior. (Supplementary Note.)
Trans. Am. Inst. Min. Eng., 1873, ii. 58, 59.

Chemical and Geological Essays. Boston, 1874, 489 pp. Revised Edition,
Salem, 1878.

The Development of Our Mineral Resources. Harper’s Magazine, 1875, li.
82-94.

Azoic Rocks, Part I., 1878. Second Geological Survey of Pennsylvania. LE.
253 pp.

The Lake Superior Copper Rocks in Pennsylvania. Trans. Am. Inst. Min.
Eng., 1879, vii. 333 - 336, 339.

The History of some Pre-Cambrian Rocks in America and Europe. Am. Jour.
Sci., 1880, (3,) xix. 268-283.

See T. C. Chamberlain aad W. E. Logan.

Irving, Roland D.
On some Points in the Geology of Northern Wisconsin. Trans. Wisc. Acad.
Sci., 1873-74, ii. 107-119.
On the Age of the Copper-bearing Rocks of Lake Superior; and on the
Westward Continuation of the Lake Superior Synclinal. Am. Jour. Sci.,
1874, (3,) viii. 46-56.
Note on the Age of the Crystalline Rocks of Wisconsin. Am. Jour. Sci.,
1877, (3,) xii. 307 - 309.
Note on the Stratigraphy of the Huronian Series of Northern Wisconsin ;
and on the Equivalency of the Huronian of the Marquette and Penokee Dis-
tricts. Am. Jour. Sci., 1879, (3,) xvii. 393-398.
See T. C. Chamberlain.
Jackson, Charles T.
Minerals from Lake Superior. Proc. Bost. Soc. Nat. Hist., 1844, i. 203;
1845, ii. 57, 58.

MUSEUM ‘OF COMPARATIVE ZOOLOGY. 145

Nature of Minerals accompanying Trap Dykes which interrupt various Rocks.
Proc. of the Sixth Ann. Meet. of the Assoc. of Am. Geol. and Nat., New
Haven, 1845, 29-31.

On the Copper and Silver of Kewenaw Point, Lake Superior. Am. Jour.
Sei, 1845, (1,) xlix. 81-98; Proc. of the Sixth Ann. Meet. of the Assoc.
of Am. Geol. and Nat., New Haven, 1845, 53-60.

Sur le Gisement de Cuivre et d’Argent natifs des Bords du Lac Supérieur.
Comptes Rendus, 1845, xx. 593-595; Bull. Soc. Geol. France, 1844 - 45,
(2,) ii. 817-319; L’Institute, 1845, xx. 593-595; Leonhard’s Jahr-
buch, 1845, pp. 479, 480.

The Copper and Silver Mines of Lake Superior. Proc. Bost. Soc. Nat. Hist.,
1846, ii. 110-114; Am. Jour. Sci., 1846, (2,) ii. 118, 119.

Report on the Mineral Lands of Lake Superior. Contains Reports by Messrs.
Locke, Channing, McNair, and Whitney. Senate Docs., lst Sess. 30th
Cong., 1847 - 48, ii., No. 2, 175 - 230.

Ores and Minerals from Lake Superior. Proc. Bost. Soc. Nat. Hist., 1847,
il. 256, 259, 260.

Mineral Lands of Lake Superior. Contains Reports of J. W. Foster and
J.D. Whitney. Senate Docs., 1848-49, 2d Sess. 30th Cong., ii., No. 2,
153-163; Executive Does., 1848 —- 49, 2d Sess. 30th Cong., iii., No. 12,
153 - 163.

Report on the Progress of the Geological Survey of the Mineral Lands of the
United States in Michigan. Senate Does., 1848 - 49, 2d Sess. 30th Cong.,
ii., No. 2, 185-191; Executive Does., 1848 - 49, 2d Sess. 30th eon
ili., No. 12, 185-191.

Copper of the Lake Superior Region. Am. Jour. Sci., 1849, (2,) vii. 286,
287."

Lake Superior. Observations on the Mirage seen on Lake Superior in July
and August, 1847. Proc. Am. Assoc. Adv. Sci., 1849, ii. 143-146;
‘Proc. Bost. Soc. Nat. Hist., 1849, iii. 169.

Remarks on the. Geology, Mineralogy, and Mines of Lake Superior. Proc.
Am. Assoc. Adv. Sci., 1849, ii. 283 - 288.

‘On the: Geological Strueture of Keweenaw Point. Proc. Am. Assoc. Adv.
Sci., 1849, ii. 288 - 301.

Remarques sur la Géologie du District Métallifere du Lac Supérieur. Bull.
Soc. Geol. France, 1849 —50, vii. 667 — 673.

Report on the Geological and Mineralogical Survey of the Mineral Lands of
the United States in the State of Michigan. Contains Reports by Messrs.
Jackson, Foster, Whitney, Locke, Barnes, Burt, Hubbard, and others.
Senate Docs., 1st Sess. 31st Cong., 1849-50, No. 5, iii. 371-935; Am.
Jour. Sci:, 1851, (2,) xi. 147, 148.

Remarques sur la Géologie du District Métallifére du Lac Supérieur, suivi
dune courte Description-de quelques-unes des Mines de Cuivre et d’Ar-
gent. Extrait par M. Delesse. Annales des Mines, 1850, (4,) xvii. 103
-115.

VOL. VII. —NO.1, 10

146 BULLETIN OF THE

Age of the Lake Superior Sandstone. Proc. Bost. Soc. Nat. Hist., 1848, iii.
76, 77; 1850, p. 228; 1860, vii. 396 - 398.

On Jacksonite. Proc. Bost. Soc. Nat. Hist., 1850, iii. 247, 248.

Former Level of Lake Superior. Proe. Bost. Soc. Nat. Hist., 1850, ili. 292.

On the Age of the Sandstones of the United States. Proc. Bost. Soc. Nat.
Hist., 1850, iti. 835 — 339.

Analyses of Pitchstone Porphyry from Isle Royale, ete. Am. Jour. Sci.,
1851, (2,) xi. 401, 402; Proc. Bost. Soc. Nat. Hist., 1851, iv. 39, 40.

Rain-Drop and Air-Bubble Impressions. Proc. Bost. Soc. Nat. Hist., 1851,
iv. 131, 132.

Geology, Mineralogy, and Topography of the Lands around Lake Superior.
Senate Does., 1851-52, 1st Sess. 32d Cong., xi. 232-244. In Andrews’s :
Report.

Igneous Origin of Calcite Veins. Proc. Bost. Soc. Nat. Hist., 1853, Feb. 17,
iv. 308, 309.

Ueber den Metallfiihrenden Distrikt am Obern See im Staate Michigan.
Karsten’s Archiv., 1853, xxv. 656 - 667.

Catalogue of Rocks, Minerals, and Ores collected during the years 1847 and
1848, on the Geological Survey of the United States Mineral Lands in
Michigan. Collected by Charles T. Jackson. Smithsonian Report, 1854,
pp. 338 — 367.

Observations sur quelques Mines des Etats-Unis et sur le Grés Rouge du
Lac Supérieur. Comptes Rendus, 1854, xxxix. $03 - 807.

Trap Dikes. Proe. Bost. Soc. Nat. Hist., 1856, vi. 28, 24.

On the Ash-bed and the Origin of the Copper. Proc. Bost. Soc. Nat. Hist.,
1855, v. 280, 281; 1859, vii. 31.

Thermal Waters. Proc. Bost. Soc. Nat. Hist., 1859, vii. 45-47.

Domeykite from Lake Superior. Proc. Bost. Soc. Nat. Hist., 1861, viii. 258.

Sur les Mines de Cuivre du Lae Supéreur et sur un Nouveau Gisement
d’Etain dans ’Etat du Maine. Compes Rendus, 1869, Ixix. 1082, 1083.

See James H. Relfe.

Jackson, Charles T., and J. B. Perry.
Glacial Origin of Lake Superior. Proc. Bost. Soc. Nat. Hist., 1870, xiv.
13-75.
Jenney, F. B.
See T. B. Brooks,
Julien, Alexis A.
See T. B. Brooks and T. C. Chamberlain.
Keating, William H.

Narrative of an Expedition to the Source of St. Peter’s River, etc., performed

in the Year 1823. 2 vols. i. 458; ii. 248, andapp. 156. London, 1825,
Kimball, J. P.

On the Iron Ores of Marquette, Mich. Am. Jour. Sci., 1865, (2,) xxix.
290 - 303.

See J. W. Foster.

MUSEUM OF COMPARATIVE ZOOLOGY. 147

Kneeland, Samuel.
Copper of Lake Superior. Proc. Bost. Soc, Nat. Hist., 1857, vi, 283, 284,
Koch, F.C. L.

Kupfer- und Eisenerze am Lake Superior. Zeit. Deut. Geol. Gesells., 1851,
i. 8355-358.

Die Mineral-Regionen der oberen Halbinsel Michigan’s (N. A.) am Lake
Superior und die Isle Royal. Studien des Gottingischen Vereins berg-
mannischer Freunde, von J. F. L. Hausmann. 1854, vi. 1-248; The
Mining Magazine, New York, 1853, i. 261 - 268.

Lachlan, R.

On the Periodical Rise and Fall of the Lakes. Am. Jour. Sci., 1855, (2,) xix.

60-71, 164-176; xx. 45-53.
Lapham, Increase A.

The Penokie Iron Range. Wisc. State Agr. Soc. Trans., 1858 - 59, v. 391 -
400, with map.

See T. C. Chamberlain.

LeConte, John L.
On Coracite,a new Ore of Uranium. Am. Jour. Sci., 1874, (2,) iii. 173 -
175.
Lesley, J. P.
Tron Manufacturer’s Guide. New York, 1859, 772 pp., with maps.
Locke, John.

Geology of Porter’s Island and Copper Harbour. Trans. Am. Phil. Soc., 1844,
ix. 311, 312, (pp. 305 - 315,) with maps.

Geology and Magnetism. Smithsonian Contributions, 1851, iii, Art. I., pp.
17-29.

Catalogue of Rocks, Minerals, Ores, and Fossils collected by John Locke.
Smithsonian Report, pp. 1854, 367 - 383.

See Charles T. Jackson.

Logan, William E.

North Shore of Lake Superior, Geol. Surv. of Canada, Rep. of Prog., 1846
-47, pp. 5-46.

Remarks on the Mining Region of Lake Superior, and a Report on Mining
Locations claimed on the Canadian Shores of the Lake. Montreal, 1847,
31 pp., with maps.

Report on the North Shore of Lake Huron. Geol. Surv. of Canada, Mon-
treal, 1849, 51 pp.

On the Age of the Copper-bearing Rocks of Lakes Superior and Huron. Re-
port of the Brit. Assoc. Adv. Sci., 1851, xxi., Trans. Sections, 59 - 62;
Am. Jour. Sci., 1852, (2,) xiv. 224-229.

Remarks on the Fauna of the Quebec Group of Rocks and the Primordial
Zone of Canada. Am. Jour. Sci., 1861, (2,) xxxi. 216 - 220.

Considerations relating to the Quebec Group and the Upper Copper-bearing
Rocks of Lake Superior. Canadian Nat. and Geol., 1861, vi. 199 - 207;
Am, Jour. Sci., 1862, (2,) xxxiii. 320 - 327,

148 BULLETIN OF THE’

Geology of Canada. Montreal, 1863, 983 pp., with atlas.

Kupfererze fiihrende Gesteine am Oberen See. : Leonhard’s Jahrbuch, 1864,
p. 741.

Geology of Canada, Ottawa, 1866, 321 pp. Contains a Report on Lake
Superior by Thomas Macfarlane.

Notes on the Report of Mr. Robert Bell on the Nipigon Region. Geol. Surv. |
of Canada, Rep. of Prog., 1866-69, pp. 471-475.

Logan, William E., and T. Sterry Hunt.

A Sketch of the Geology of Canada, in Canada at the Paris Exhibition, 1855,

pp. 411-454.
Lyell, Charles.

New York Industrial Exhibition. Sir Charles Lyell’s Special Report on the
Geological, Topographical, and Hydrographical Departments. Blue Book,
1854, xxxvi., 50 pp. Annales des Mines, 1854, (5,) vi. 1 - 83.

Macfarlane, James.
Geologist’s Travelling Hand-Book. New York, 1878, 261 pp:
Macfarlane, Thomas.

On the Primitive Formations in PNcoae and in Canada, Canadian Nat. and
Geol., 1862, vii. 1 - 20, 113-128, 161-171.

Report on the Geely of Lake Superior... Geol. of Canada, 1866, pp. 115 -
164. in.

On the Rocks and Cupriferous Beds of Portage Lake, Michigan. Canadian
Nat. and Geol., 1866-68, (2,) iii. 1-18; Geol. of Canada, 1866, pp.
149 - 164.

On the Geological Formations of Lake Superior. Canadian Nat. and Geol.,
1866 -68, (2,) iil. 177 — 202, 241 — 257.

On the Geology and Silver Ore of Wood’s Location, Thunder Cape, Lake
Superior. Canadian Nat. and Geol., 1869, (2,) iv. 87 — 47, 459 - 463.

Remarks on Canadian Stratigraphy. Canadian Nat. and Geol., 1879, (2,)
ix. 91-102.

Marcou, Jules.

Réponse a la Lettre de MM. Foster et Whitney sur le Lac Supérieur. Bull.
Soe. Geol. France, 1850, (2,) viii. 101-105.

A Geological Map of the United States and the British Provinces of North
America, with an Explanatory Text, Geological Sections, ete. Boston,
June, 1853. 92 pp.

Esquisse d’une Classification des Chaines de Montagnes d’une Partie de
YAmérique du Nord. Comptes Rendus, 1854, xxxix. 1192-1197; An-
nales des Mines, 1855, (5,) vii. 329-350; Mining Mag., 1856, vil. 321-
333.

Résumé explicatif dune Carte: Géologique des Etats-Unis et des Provinces
Anglaises de l’ Amérique du Nord, avee un Profil Géologique allant de la
Vallée du Mississipi aux Cotes du Pacifique, et une Planche de Fossiles.
Bull. Soe. Geol. France, 1854-55, (2,) xii. 813-936.

MUSEUM OF COMPARATIVE ZOOLOGY. 149

Die Geologie der Vereinigten Staaten und der Englischen Provinzen von
Nord-Amerika von Jules Marcou. Petermann’s Geographische Mitthei-
lungen, 1855, pp. 149 - 159.

Geology of North America, with Three Geological Maps and Seven Plates of
Fossils. Zurich, 1858, 144 pp.

Reply to the Criticisms of James D. Dana. Zurich, 1859, 40 pp.

Dyas et Trias ou le Nouveau Grés Rouge en Europe dans l’Amérique du
Nord et dans l’Inde. Zurich, 1859, 63 pp.

On the Primordial Fauna and the Taconic System. Proc. Bost. Soc. Nat.
Hist., 1860, vii. 369 - 382.

Marteaux en pierre des anciens Américains, pour |’Exploitation des Mines de
Cuivre et d’Argent Natifs du Lac Supérieur. Comptes Rendus, 1866,

_ xii. 470, 471.
Marvine, A. R.
Geology of Michigan, Part II., 1873,
See T. B. Brooks.
Mather, W. W.

Notes and Remarks connected with Meteorology on Lake Superior, etc. Am.

Jour. Sci., 1848, (2,) vi. 1-20.
McCracken, S. B.

The State of Michigan, embracing Sketches of its History, Position, Re-

sources, and Industries: Lansing, 1876, pp. 48 - 69.

M’ Kellar, Peter.
* Mining on the North Shore of Lake Superior. Toronto, 1874, 26 pp.

McKenney, Thomas L.
Sketches of a Tour to the Lakes. Baltimore, 1827, 493 pp. North Ameri-
can Review, 1827, xxv. 334-352.

McNair, D. K.
See Charles T. Jackson,
Mitchell, Samuel L.
Native Copper of North America. Medical Repository, 1818, (2,) iv. 101,
102.
Mosler, Chr.
Der Kupferbergbau am Obern See in Nordamerika. Zeitschr. Berg. Hiitt,
Salin., 1877, Abhandlungen, xxv. 203-221; 1879, xxvii. 77-97.
Miller, Alb.

- Ueber die Kupferminen am Obern See im Staate Michigan, Nordamerika.
Verhandlungen der Naturforschenden Gesellschaft in Basel. 1857, pp.
411-438 ; Leonhard’s Jahrbuch, 1857, pp. 79 - 82, 589, 590.

Murchison, Roderick I.
Siluria. London, 1854, 523 pp.
Murray, Alexander.
North Shore of Lake Superior. Geol. Surv. of Canada, 1846-47, pp.
47-57. * baer

150 BULLETIN OF THE

* Geology of Western Canada. Canadian Jour., 1854-55, (1,) iii. 27-20,

48 —52, 73 — 76.
Murrish, John.

Report on the Geological Survey of the Mineral Regions. Trans. Wisc. Agr.

Soc., 1872-73, pp. 469 — 494.
Newberry, J. S.

Notes on the Surface Geology of the Basin of the Great Lakes. Proc. Bost.
Soe. Nat. Hist., 1862, ix. 42-46.

On the Surface Geology of the Basin of the Great Lakes and the Valley of the
Mississippi. Ann. of the Lyc. of Nat. Hist., 1870, ix. 213 - 284.

The Iron Resources of the United States. International Review, 1874, ii.
754-780.

Nicholson, H. Alleyne.

On the Geology of the Thunder Bay and Shabendowan Mining Districts on
the North Shore of Lake Superior. Quart. Jour. Geol. Soc., 1873, xxix.
17 - 24.

On the Mining District on the North Shore of Lake Superior. Trans. of
North of England Inst. of Min. and Mech. Eng. Newcastle-on-Tyne,
1874-75, xxiv. 237 -249, with maps.

Noggerath, Johann Jacob.

Von dem Gediegen-Kupfer mit Gediegen-Silber am den Gruben von Kezena

Point. Weonhard’s Jahrbuch, 1848, p. 555.
Owen, David D.

Preliminary Report on the Geological Survey of Wisconsin and Iowa. Senate
Does., 1st Sess. 80th Cong., 1847-48, i1., No. 2, pp. 160-174.

Lake Superior. Report of a Geological Reconncissance of the Chippewa Land
District of Wisconsin, ete. Senate Doces., lst Sess. 30th Cong., 1847-48,
vil., No. 57, 134 pp. Am. Jour. Sci, 1850, (2,) x. 1-12.

Abstract of an Introduction to the Final Report of the Geological Surveys
made in Wisconsin, Iowa, and Minnesota in the Years 1847, 748, 749, and
’50, containing a Synopsis of the Geological Features of the Country.
Proc. Am. Assoc. Ady. Sci., 1851, v. 119-132.

Report of a Geological Survey of Wisconsin, Iowa, and Minnesota. Am.
Jour. Sci., (2,) 1853, xv. 296-299; Philadelphia, 1852, 638 pp., with
maps. Am. Jour. Sci., 1853, xv. 296 — 299.

Catalogue of Geological Specimens collected by David D. Owen. Smithsonian
Report, 1854, pp. 393 — 396.

Description of two new Minerals and a new Earth. Jour. Acad. Nat. Sci.
Phil., 1852, (2,) ii. 179-183; Am. Jour. Sci., 1852, (2,) xiii. 420-428 ;
Ann. Sci. Discov., 1853, pp. 290, 291.

Palliser, John, axd James Hector.

Papers relative to the Exploration of British North America. Blue Book,

1859, Sess. 2, xxii., 64 pp., with maps.

Peckham, S. F., and C. W. Hall.

. Lintonite and other Forms of Thomsonite. Am. Jour. Sci., 1880, (3,) xix.
122 - 130.

MUSEUM OF COMPARATIVE ZOOLOGY. 151

Perry, John B.
See Charles T. Jackson.
Phillips, J. V.

The Geology of the Upper Mississippi Lead Region. Mining Mag., New York,

1854, ii. 129-188.
Piggot, A. Snowden.

On Copper and Copper Mining. Philadelphia, 1858, 388 pp.; Mining Mag.,
1858, x. 124-142, entitled History of the Copper Region of Lake Supe-
rior.

Porter, George F.

Report on the Copper Rock. George F. Porter in Thomas L. McKenney’s

Tour to the Lakes, Baltimore, 1827, pp. 477, 478.
Posselt, C.
Die Kupfer-Distrikte des Obersee’s, Lake Superior. Leonhard’s Jahrbuch,
1856, pp. 1-10.
Preston, Samuel.
Copper Ore on Lake Superior. Niles’s Weekly Register, 1829, (3,) xii. 203.
Pumpelly, Raphael.

The Paragenesis and Derivation of Copper and its Associates on Lake Supe-
rior. Am. Jour. Sci., 1872, (3,) iii. 188 — 198, 243 - 258, 347-353 ; Leon-
hard’s Jahrbuch, 1872, pp. 538-540; Geol. of Michigan, Part IT., 1873.

On Pseudomorphs of Chlorite after Garnet at Spurr Mountain Iron Mine.
Am. Jour. Sci., 1875, (3,) x. 17-21.

~ Metasomatic Development of the Copper-bearing Rocks of Lake Superior.
Proc. Am. Acad., 1878, xiti. 253-309.
See T. B. Brooks and T. C. Chamberlain.

Rath, Gustav vom.

Ueber Kalkspath vom Oberen See. Pogg. Ann., 1867, exxxii. 387 - 404;

Leonhard’s Jahrbuch, 1868, pp. 347, 348.
Rawson, A. L.

Pictured Rocks of Lake Superior. Harper’s New Monthly Mag., 1867,

xxxiv. 681.
Relfe, James H.

Sale of Mineral Lands. Reports of Committees, 1845-46, Ist Sess. 29th
Cong., iii., No. 591, 51 pp. with map. Contains part of Douglass
Houghton’s Fourth Report, and some Analyses by Charles T. Jackson.

Richardson, John.

On some Points of the Physical Geography of North America in Connection
with its Geological Structure. Quart. Jour. Geol. Soc., 1851, vii. 212-
215.

Rivot, L. E.

Mémoire sur le Gisement du Cuivre Natif au Lac Supérieur. Comptes: Ren-
dus, 1855, xl. 1306 -1309.

Voyage au Lac Supérieur. Annales des Mines, 1855, (5,) vii. 173-328;

152- BULLETIN OF THE

Mining Mag., 1856, (1,) vi. 28-37, 99-106, 207-218, 414-418; vii,
249 —255, 359-367; 1857, ix. 60-65.

Notice sur le Lac Supérieur. Annales des Mines, 1856, (5,) x. 365 -474.

Uber die Kupfererz-Lagerstatten am Obersee in den Nordamerikanischen
Freistaaten. Berg. u. Hiitten. Zeit., 1856, pp. 261 - 263, 269 — 271, 293 -
295, 277 — 279, 314, 315, 317, 318, 325-328, 333, 334, 341-343, 349=
351, 357 -— 359, 365 — 367, 381; 382.

Analysis of Lake Superior Iron Ore. Mining Mag., 1856, vii. 301.

Rogers, H. D.

Mineralogy and Geology of Lake Superior. Proc. Bost. Soc. Nat. Hist.,

1846, ii. 124, 125.
Rogers, William B.

On the Origin of the Actual Outlines of Lake sie Proc. Am. Assoc,
Adv. Sci., 1848, i. 79, 80.

Age of the Sandstone. Proc. Bost. Soc. Nat. Hist., 1860, vii. 394, 395.

Rolker, Charles M.

The Allouez Mine and Ore Dressing; as practised in the Lake Superior Cop-

per District. Trans. Am. Inst. Min. Eng., 1877, v. 584-606.
Rominger, Charles.

Observations on the Ontonagon Silver Mining District and the Slate Quarries
of Huron Bay. Geol. Surv. of Michigan, 1876, il. 153 — 166.

See T. B. Brooks, Geol. Surv. of Michigan, 1873, 1i., Part IIT.

Rottermund, Count de.
_ Report on the Exploration of Lakes Superior and Huron. Canada Legisla-
tive Assembly, 1856, 24 pp. ; Canadian Jour., 1856, (2,) 1. 446 — 452.
Ruggles, D.

Tides in the North American Lakes. Am. Jour. Sci., 1843, Ql) 3 xlv.
18 — 27.

Considerations respecting the Copper Mines of Lake Superior. Am. Jour.
Sci., 1845, (1,) xlix. 64-72.

Russell, John L.

Wood from the Terraces of Lake Superior. Proc. Bost. Soc. Nat. Hist.,

1850, ili. 273.
Sanders, George N.

Mineral Lands of Lake Superior. Senate Does., 2d Sess. 28th Cong., 1844 —
45, vil, No. 117, pp. 3-9; xi., No. 175, pp. 8-14.

See John Stockton.

Sauvage, E.

Notice sur les Minerais de Fer du Lac Supérieur. Annales des Mines, 1875,

(7,) vill. 1-35.
Schoolcraft, Henry R.

Narrative Journal of Travels through the Northwestern Regions of the United
States, extending from Detroit through the Great Chain of American
Lakes to the Sources of the Mississippi River. Albany, 1821, 419 pp.
with map.

MUSEUM OF COMPARATIVE ZOOLOGY, 153

Account of the Native Copper on the Southern Shore of Lake Superior, with
Historical Citations and Miscellaneous Remarks, in a Report to the De-
partment of War. 1821. Am. Jour. Sci., 1821, (1,) ii. 201-216;
Quart. Jour. Sci., 1822, xii. 422 - 423.

On the Number, Value, and Position of the Copper Mines on the Southern
Shore of Lake Superior. Senate Papers, 2d Sess. 17th Cong., 1822,
Doe. 5, 33 pp.

Notice of a Recently Discovered Copper Mine on Lake Superior, with several
other Localities of Minerals. Am. Jour. Sci., 1824, (1,) vii. 43-49.

Narrative of an Expedition through the Upper Mississippi to Itasca Lake, the
Actual Source of this River. New York, 1834, 307 pp. with map. Con-
tains a Report by Douglass Houghton.

Localities of Minerals observed in the Northwest-in 1831 and 1832. Dis-
covery of the Source of the Mississippi, pp. 157-159. New York, 1834..

~ On the Production of Sand Storms and Lacustrine Beds by Causes associated
with the North American Lakes. Proc. Brit. Assoc. Adv. Sci., 1842, xii,
Trans. Sections, 42-44; Am. Jour. Sci., 1843,-(1,) xliv. 368 - 370.

A Memoir on the History al Physical Geography of Minnesota. Minn. Hist.
Coll., 1850-56, i. 108-182.

Summary Narrative of an Exploratory Expedition to the Sources of the
Mississippi River in 1820, resumed and completed by the Discovery of
its Origin in Itasca Lake in 1832. Philadelphia, 1854. Purports to con-
tain many of the original Reports to the War Department, and other:
papers.

Selwyn, Alfred R. C.
Notes of a Geological Reconnoissance from Lake Superior to Fort Garry.
Geol. Surv. of Canada, Rep. of Prog., Montreal, 1872 —73, pp. 8-18.

The Stratigraphy of the Quebee Group and the Older Crystalline Rocks of
Canada. Canadian Nat. and Geol., 1879, (2,) ix. 17-32; Geol. Surv. of
Canada, Rep. of Prog., 1877-78, A. 15 pp.

Shepard, Charles U.

On the Copper and Silver of Kewenaw Point, Lake Superior. Proc. of the
Sixth Ann. Meet. of the Assoc. of Am. Geol. and Nat., New Haven, 1845,
60, 61. :

_,Tautolite on the North Shore of Lake Superior. Am. Jour. Sci., 1847, (2,)
iv. 278.
Shepherd, Forrest.

Remarks on a Boulder Mass of Native Copper from the Southern Shore of
Lake Superior. Am. Jour. Sci., 1847, (2,) iv. 115, 116.

Observations on the Drift, Furrows, Grooves, Scratches, and Polished Surfaces
of the Rocks of Lake Superior. Am. Jour. Sci., 1847, (2;) iv. 282, 283.

Spencer, Joseph William.
Lake Superior. — On the Nipigon or Copper-bearing Rocks of Lake Superior,
with Notes on Copper Mining in that Region. Canadian Nat. and Geol.,
1878, (2,) viii. 55 -81.

154 BULLETIN OF THE

Stanard, B. A.
Stanard’s Rock. In the “ Mineral Regions of Lake Superior,” by J. Hough-
ton, Jr., and T. W. Bristol, page 81.

Stevens, William H.
The Prospects of the Lake Superior Mining Region. Mining Mag., 1854, ii.
149 - 153.
Stockton, John.
Report on the Mineral Lands of Lake Superior. Senate Docs., 1844 — 45,
9d Sess. 28th Cong., xi., No. 175, 22 pp. with map. Contains reports by
Messrs. J. B. Campbell, George N. Sanders, and A. B. Gray.

Strong, Moses.
See I’. C. ‘Chamberlain.
Sweet, E. T.

Notes onthe Geology of Northern Wisconsin. Trans. Wise. Acad., 1875-76,
iil. 40-55.

See T. C. Chamberlain.

Swineford, A. P.

History and Review of the Copper, Iron, Silver, Slate, and other Material
Interests of the South Shore of Lake Superior. Marquette, Mich., 1876.
Contains Ancient Copper Miners, J. Houghton, 78-89; C. E. Wright,
Geology of the Lake Superior Iron District, 132-145.

Tamnau, F.
Minerals from the Copper District of Lake Superior. Zeit. Deut. Geol.
Gesells., 1852, vi. 3-6, 9,10; 1854, vi. 11; Leonhard’s Jahrbuch, 1854,
442, 443; 1855, 349.
Teschemacher, J. E. .
Harmotome and Volborthite from Lake Superior. Proc. Bost. Soc. Nat.
Hist., 1849, iii. 105, 106.
Tod, David.
See William Bartlit.
Tuttle, H. B.
See T. B. Brooks.
Verneuil, Edouard P. de.
Lettre sur la Géologie des Etats-Unis. Bull. Soc. Géol. France, 1846 - 47,
(2,) iv. 12, 13.
Whiting, Henry.
Remarks on the Supposed Tides and Periodical Rise and Fall of the North
American Lakes. Am. Jour. Sci., 1831, (1,) xx. 205 -— 219.

Whitney, J. D.
Description and Analysis of Three Minerals from Lake Superior. Bost. Jour.
Nat. Hist., 1847, v. 486-489; Am. Jour. Sci., 1848, (2,) vi. 269, 270.
Jacksonite, a New Mineral from the Lake Superior Region. Proce. Bost. Soc.
Nat. Hist., 1848, iii. 5, 6.

MUSEUM OF COMPARATIVE ZOOLOGY. 155

Chlorastrolite, from Isle Royale, Lake Superior. Proc. Bost. Soc. Nat.
Hist., 1848, iii. 12.

Chemical Examination of some American Minerals. Bost. Jour. Nat. Hist.,
1850-57, vi. 36-42; Proc. Bost. Soc. Nat. Hist., 1848, iii, 78, 79;
Am. Jour. Sci., 1849, (2,) vii. 434, 435.

Black Oxide of Copper at Copper Harbor, Lake Superior. Proc. Bost. Soc.
Nat. Hist., 1849, iii. 102, 103; Ann. Sci. Discov., 1850, pp. 261, 262;
Am. Jour. Sci., 1849, (2,) vill. 273, 274.

The Lake Superior Copper and Iron District. Proc. Bost. Soc. Nat. Hist.,
1849, iii. 210-212.

Fracture of Slate at the Jackson Forge. Proc. Bost. Soc. Nat. Hist., 1850,
iii. 226.

Catalogue of the Rocks, Minerals, ete., collected on the District between
Portage and Montreal River, during the Years 1847 and 1848, by J. D.
Whitney. Smithsonian Report, 1854, pp. 387 — 392.

The Metallic Wealth of the United States. Philadelphia, 1854, 510 pp.

Review of Murchison’s Siluria. Am. Jour. Sci., 1855, (2,) xix. 371-385.

Remarks on some Points connected with the Geology of the North Shore of
Lake Superior. Proc. Am. Assoc. Adv. Sci., 1855, ix. 204-209.

On the Occurrence of the Ores of Iron in the Azoic System. Proc. Am.
Assoc. Adv. Sci., 1855, ix. 209-216; Mining Mag., 1856, vil. 67-73;
Am. Jour. Sci., (2,) 1856, xxii. 38 - 44.

Notice of New Localities, and Interesting Varieties of Minerals, in the Lake
Superior Region, supplementary to the Chapter on this subject in Part
IL. of the Report of Foster and Whitney. Am. Jour. Sci., 1859, (2,)
xxviii. 8-20; Mining Mag., 1860, (2,) i. 32 - 47.

Note on the Geological Position of the Lake Superior Sandstone. Mining
Mag., 1860, (2,) i. 435-446.

On the Chemical Composition of Pectolite. Am. Jour. Sci., 1860, (2,) xxix.
205 - 208.

See Edward Desor, Foster and Whitney, ad Charles T. Jackson.

Whitney, William D.
See Foster and Whitney.

Whittlesey, Charles.

On the ‘Superficial Deposits ” of the Northwestern Part of the United States.
Proc. Am. Assoc. Adv. Sci., 1851, v. 54-59.

On the Ancient Mining Operations on Lake Superior. Proc. Am. Assoc.
Adv. Sci., 1857, xi. 42-44.

Fluctuations of Level in the North American Lakes. Proc. Am. Assoc. Ady.
Sci., 1857, xi. 154-160.

On the Origin of the Azoic Rocks of Michigan and Wisconsin. Proc. Am.
Assoc. Adv. Sci., 1859, xiii. 301-308.

On Fluctuations of Level in the North American Lakes. Smithsonian Con-
tributions to Knowledge, 1859, xii., No. 2, 25 pp.

156 | BULLETIN OF THE

The Penokie Mineral Range, Wisconsin, Proc. Bost. Soc. Nat. Hist., 1863,
ix. 235 -—244.
On the Movements of the Glacial Era in the Valley of the St. Lawrence.
Proc. Am. Assoc. Ady. Sci., 1866, xv. 43-54.
On the Fresh-Water Glacial Drift of the Northwestern States. Smithsonian
Contributions to Knowledge, 1866, xv. 1-32; Smithsonian Report, 1866,
32 — 36.
Abstract of Remarks upon the Occurrence of Iron in Masses. Proc. am
Assoc. Ady. Sci., 1867, xvi. 97-107.
On the Cause of the Transient Fluctuations of Level in Lake Superior, Proc,
Am. Assoc. Adv. Sci., 1878, xxii., Part IL, 42-46.
Sudden Fluctuations of Level in Quiet Water: Records of Observations,
Proc. Am. Assoe. Adv. Sci.; 1874, xxiii. 1389 - 143. )
Physical Geology of Lake Superior. Proc. Am, Assoc. Ady. Sci., 1875,
xxiv. 60-72.
On the Origin of Mineral Veins. Proc. Am. Assoc. Adv. Sci., 1876, xxv.
213-216.
See T.C. Chamberlain, and Foster and Whitney.
Wichmann, Arthur.
A Microscopical Study of some Huronian Clay Slates. Quart. Jour. Geol.
Soc., 1879, xxxv. 156 - 164.
See T. C. Chamberlain.
Wight, O. W.
ee T. C. Chamberlain.
Williams, C. P., and J. F. Blandy.
Some Contributions to a Knowledge of the Constitution of the Copper Range
of Lake Superior. Am. Jour. Sci., 1862, (2,) xxxiv. 112-120.
Wilson, Daniel.
The Ancient Miners of Lake Superior. Canadian Journal, 1856, (2,) i. 995
— 237.
The Southern Shores of Lake Superior. Canadian Journal, 1856, (2,) i. 344-
356.
Winchell, Alexander.
First Biennial Report of the Progress of the Genloziaal Survey of Michigan.
Lansing, 1861, 339 pp.
Notice of a small Collection of Fossils from the Potsdam Sandstone of Wiscon-
‘sin and the Lake Superior Sandstone of Michigan. Am. Jour. Sci., 1864,
(2,) xxxvii. 226 — 232.
*Geological Map of Michigan. Philadelphia, 1866. Leonhard’s Jahrbuch,
1868, pp. 99-101.
The Isothermals of the Lake Region. Proc. Am. Assoc. Adv. Sci., 1870,
xix. 106-117.
- The Diagonal System in the Physical Features of Michigan, Am. Jour. Sci.,
1873, (3,) vi. 36-40.

MUSEUM OF COMPARATIVE ZOOLOGY. 157

Winchell, N. H.
The Glacial Features of Green Bay of Lake Michigan, with some Observa-
tions on a Former Outlet of Lake Superior, Am. Jour. Sci., 1871, (3,)
ii. 15-20.
The Geological and Natural History Survey of Minnesota. 1872-1878.
7 volumes. Geology of Lake Superior, lst, 2d, and 7th vols. The last
contains a Report by C. W. Hall.
Wright, Charles E.
First Annual Report of the Commissioner of Mineral Statistics of the State of
Michigan for 1877-78. Marquette, 1879, 229 pp.
See T. B. Brooks, T. C. Chamberlain, avd A. P. Swineford,

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FicurE 25. (page 51) shows in section the relation of the ‘‘ soft hematite,” repre-
sented by oval marks, to the jasper and ore above and on both sides of it ; also to fis-
sures which allow the percolation of water, the upper portion of the figure being

adjacent to the surface of the ground. McComber Mine, Negaunee.

Ficure 26 (page 55) shows in section reddish eruptive granite cutting gray gneiss.
The granite at the left and bottom of the figure is connected with the main body of

the granite. South of Ishpeming.

Ficure 27 (page 113) represents in section a tongue of trap extending down into
the ash-bed, and holding a rounded fragment of the latter. End of drift, Sept. 12,
1879, 5thlevel. Copper Falls Mine, Keweenaw Point.

FIGURE 28 (page 113) shows the denuded and irregular surface of the underlying
sandstone, covered by the overlying lava flow. Emerson Adit, Copper Falls Mine,
Keweenaw Point.

All the figures, except when otherwise stated, are from free-hand sketches made in
the field from actual observed occurrences. No attempt has been made to draw to
scale, or to show anything except the actual relations of the rocks to one another.
The sketches were redrawn by the writer, engraved on stone by Mr. L. Trouvelot,
and printed by A. Meisel.

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PLATE I.

Fricure 1 (page 30) represents the contact of the jasper and ore on the left hand
with the schist on the right. This section shows the relations of the banding of the
jasper to the line of junction. Lake Superior Mine, Ishpeming.

Ficure 2 (page 30) represents in plan the projection of the banded jasper on the
left into the schist on the right, the banding running parallel to the walls. Lake
Superior Mine, Ishpeming.

Ficure 3 (page 30) represents in section a dike of very fair hematite ore, extend-
ing across the lamination of the schist. Lake Superior Mine, Ishpeming.

Ficure 4 (page 31) is a section showing the relations of the branching dikes of
hematite to the schist. Cleveland Mine, Ishpeming.

Ficure 5 (page 31) shows in section the relation of the jasper and ore to the un-
derlying schist. Jackson Mine, Negaunee.

Ficure 6 (page 31) shows in section the relations of the hematite to the schist.
The hematite projects in a large knob-like mass up into the schist, and is connected

with the main body of ore below. Jackson Mine, Negaunee.

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PLATE If.

Ficure 7 (page 31) represents a section of a dike of iron ore extending across the
lamination of the schist. Jackson Mine, Negaunee.

Ficure 8 (pages 31, 32) represents in section the relations of a decomposed hema-
tite (‘‘ soft hematite”) to the schist. In this case the curvature and dislocation of
the schist by the upthrust of the ore is well shown, as represented along the curve
b, c. Of our own knowledge we cannot state that the part a belongs to the hematite

on the right, as represented. Jackson Mine, Negaunee.

Ficure 9 (page 32) shows a section of jasper and ore intruding in a wedge-
shaped mass obliquely through the schist. Jackson Mine, Negaunee.

Ficure 11 (page 32) represents in section the intrusion of ore in a dike of varying
dimensions between and across the lamine of the schist, bending them in different

directions, as shown to a certain extent in the figure. Jackson Mine, Negaunee.

2

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PLATE III.

Ficure 10 (page 32) represents in section the ore passing around and cutting off
a portion of the schist, some six feet in length, from the main body. The ore at the
lower portion of the figure was then being mined, the schist forming a horse in

it. Jackson Mine, Negaunee.

Ficure 12 (page 32) shows the relations of ore, which was then being mined, to
its overlying schist. This represents a section some twenty feet in length. Jackson
Mine, Negaunee.

FicureE 13 (page 32) represents a section of a jasper dike in a sandstone. The dike
is of irregular width, and approximately follows the stratification of the sandstone in
its main course. It sends projections in places out across the lamine, breaking, con-
torting, and indurating them. The dike is some fifteen feet in length, and in the
figure its width has been greatly exaggerated compared with its length. Home Mine,
Cascade Range.

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PLATE IV.

Ficure 14 (page 36) represents in plan a ‘‘diorite” dike with a tongue extended

into the schist. Light-house Point, Marquette.

FicurE 15 (page 36) shows in plan the line of junction of a ‘‘diorite’”’ with the

schist. Quarry near Light-house, Marquette.

Ficure 16 (pages 36, 38) shows in plan the relations of a felsite, represented on
the right of the figure by angular marks, to a later ‘‘diorite” dike and to the schist.
The ‘“diorite”’ cuts and faults the felsite, but as the portion to the left of the “ dio-
rite” is under the waters of the lake, the writer is not sure of the accuracy of ‘that

portion of the figure.

FicureE 18 (page 41) shows in plan the line of junction between the “ diorite” and

schist. East of Ishpeming.

? and

Ficure 19 (page 41) shows in plan the line of contact between the ‘‘diorite’
schist, with an enclosed fragment of schist in the ‘‘diorite.” Northeast of the

Cleveland Mine, Ishpeming.

FiGureE 20 (page 41) is a section, chiefly ideal, showing the supposed relations of
the ‘‘diorite”’ dike to the adjacent schist, at the same locality as Fig. 19.

FicureE 21 (page 41) represents in plan the line of junction between the ‘‘ diorite”
and schist. Northeast of the Cleveland Mine, Ishpeming.

Bull. Museum Comp. Zool. Vol. VI ( Geol. Sertes I)

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PLATE V.

Ficure 17 (page 39) shows in plan the relations of the granite denoted by the
crossed (++) space to the ‘‘diorite.” The ‘‘diorite”’ shows in mass on the left, and
in rounded fragments in the granite. Picnic Point, north of Marquette.

FIGURE 22 (page 41) represents the line of junction between the ‘‘diorite” on the
right with the schist on the left. Northeast of the Cleveland Mine, Ishpeming.

Ficure 23 (pages 49, 50) represents a plan, partly ideal, of a narrow diabase dike
cutting a broad ‘‘diorite”’ dike and the schists at Ishpeming. The lettering is ex-
plained in the text. Salisbury Mine, Ishpeming.

Ficure 24 (pages 49, 50) is an ideal section showing the supposed relation of the

above ‘‘diorite” to the schists. Salisbury Mine, Ishpeming.

No. 2.—The Felsites and their Associated Rocks North of Boston.
By J. S. DILter.

THE extremely interesting and complicated petrology of Eastern
Massachusetts has been the subject of a great deal of discussion, and
at no time in the past have opinions concerning the origin and relations
of the rocks been more at variance than at present. It is important,
therefore, that the facts to be found in nature be carefully observed and
described in order that the various differences of opinion may, as far as
possible, be removed and the truth demonstrated. There are, however,
certain localities whose facts appear, under the eyes of some observers,
to be very different from those seen by other observers in the same place ;
and it seems necessary in such cases, where the facts are questioned, to
describe them with more than usual detail.

The field we have explored includes Melrose, Malden, and the southern
portions of Medford, Stoneham, Wakefield, Saugus, and Lynn. Within
this area felsite is the chief rock, and with it are associated, besides a
complex group of tufaceous rocks, commonly called breccias, a group
of stratified rocks, granites, diorites, slates, and diabases. The recent
“Contributions to the Geology of Eastern Massachusetts,” by W. 0.
Crosby, contains a map upon which the general distribution of the
rocks, so far as we know, is quite correctly given ; but, as Mr. Crosby
is doubtless well aware, there are many places, and some of them im-
portant, too, where the map is in error. We cannot expect to have for
many years to come a very accurately detailed geological map of this
neighborhood, for even if we had, what we have not, a correct topo-
graphical map to use as a basis of geological work, the extreme com-
plexity of the rocks, together with their highly altered condition and
the existence of quite extensive covered areas must necessarily require
a long time for correct delineation. In determining the relative age of
eruptive rocks we have been guided by the generally accepted criterion,
viz. that of two rocks, the one which penetrates the other in dike-like
masses or contains fragments of the other is the younger. In consider-
ing the rocks associated with the felsites, we shall notice them in the
order of their ages, beginning with the oldest, and endeavor to describe
the facts apart from theoretical considerations.

VOL. VII.— NO. 2. 11

166 BULLETIN OF THE

Stratified Group.

The name stratified group is applied to certain rocks whose only
common character is that of stratification; and although the rocks of
the Boston basin, and also some of the so-called breccias, are distinctly
stratified, there is no difficulty in separating the first group, at least
geographically, from the others, for its distribution is widely different.
The stratified group, consisting chiefly of quartzite and argillaceous
rocks, forms an important area, extending from Medford northeast across
Spot Pond and Melrose into Saugus. It is a long, narrow band, and
fortunately it adjoins the granite, felsite and diorite, so that we have
upon the borders of this area the means of determining the relations
of all of the rocks mentioned. The petrological relations of this group
and its probable much wider distribution upon the surface in former
times will be considered later.

Granite.

The granite occupies a large area in Medford southwest of Spot Pond,
and also in the eastern part of Melrose, extending into central and
northern Saugus. In Malden there are four small areas of granite, one
near Pleasant Street between Malden and Medford, another northeast of
Prospect Hill, a third along the Newburyport turnpike north of Broad-
way station, and a fourth near Franklin Park.

The relation of the granite to the stratified group is shown by many
facts so evident, that, as far as the phenomena themselves are concerned,
there is no difference of opinion among observers.

North of Howard Street, along the Melrose-Saugus line, and at other
places, the granite occurs in oblong or irregular patches, apparently as
an eruptive in the stratified group. The facts in these cases are, how-
ever, not as convincing as others so abundant throughout the regions in
which the granites predominate. It has been frequently observed that
upon Marblehead Neck the coarsely crystalline granite contains frag-
ments of distinctly stratified rocks. In the granite of Medford stratified
fragments are abundant, and sometimes at a considerable distance from
the nearest large outcrops of their parent rock. This is especially the
case with those found near the western base of Pine Hill. The granite
in a beautifully glaciated exposure near the west end of Long Pond,
Melrose, envelops several angular pieces of rock in which the stratifi-
cation can be readily traced. Similar phenomena may be observed upon

MUSEUM OF COMPARATIVE ZOOLOGY. 167

the western shore of Pranker’s Pond, Saugus, and Wenunchus Lake,
Lynn. A very fine example of stratified inclusions within the granite
has been pointed out by Mr. Crosby * at Break-heart Hill, Saugus. The
best exposures at this locality are not far from Forest Street, on the west.
side of a private road leading from Mr. Artemus Edmond’s northward
towards Pleasant Lake. The coarse-grained granite makes very clearly
defined contacts with the stratified rocks which it envelops, and the
fragments in which the stratification is prominent are large and numer-
ous, and the facts so evident that they cannot be questioned. It is
interesting to notice that the strike and dip of the planes of stratifica-
tion are about the same in allof the enveloped fragments (strike N. 5° -
10° E. Dip 90°). This phenomenon is developed in a very remarkable
degree about half-way between Oakland Vale and Long Pond, where the
granite is full of elongated fragments whose stratification is nearly verti-
cal, and whose strike is approximately N. 40° E. This direction corre-
sponds very nearly to a sort of gneissoid arrangement of the minerals in
the coarse granite of adjacent localities where the fragments do not occur.
Almost all the varieties of rocks which occur in the stratified group are
represented by fragments in the granite. The fragments vary in size
from an inch to many feet in length, and are generally more highly
metamorphosed than the large mass of the group from which they were
derived. The quartzite, although occurring in very well marked frag-
ments, is not nearly so abundant as the less silicious varieties.

It is probable that the position of the fragments, in some cases at
least, as well as the gneissoid structure found in the same region may
indicate the direction of motion in the enveloping mass at the time of
its extrusion. The general distribution of the fragments of the strat-
ified group, throughout a greater portion of the granites we have exam-
ined, forces us to admit, either that the granites have moved quite a
long distance from the present outcropping stratified group, or else
that the latter group at the time of the eruption of the granites had a
wider distribution. The large dike of diabase at the west base of Pine
Hill, Medford, contains quite a number of fragments which closely
resemble the quartzite of the stratified group. If they are fragments of
quartzite from the stratified group, they must have been brought from
beneath the surrounding felsite, either from the stratified group in place,
or an included fragment in the granite. Such facts render it probable
that before the granites and felsites reached the surface, the stratified
group had a much wider distribution than it has at the present time.

* Contributions to the Geology of Eastern Massachusetts, p. 39.

168 BULLETIN OF THE

Felsite.

The felsites, extending from Medford through Malden, Melrose, and
Saugus to the eastern part of Lynn, and northward from Melrose into
Wakefield, are the prevailing rocks of that region. Their petrological
relations have been one of the chief enigmas in the geology of Eastern |
Massachusetts, and, judging from the present diverse opinions, much
thorough work needs to be done before a final solution is reached. Most
observers agree that the felsites are of more recent age than the granites ;
nevertheless, there is a wide difference of opinion concerning the phe-
nomena upon which this common conclusion is based. Some observers
maintain that the felsite is younger than the granite, from the fact, as
they say, that the felsite not only envelops detached fragments of the
granite, but also penetrates it, in the form of distinct dikes. Other ob-
servers reach the same conclusion, because, in their opinion, the granite
envelops felsitic fragments, and in the form of irregular dikes pene-
trates the felsite.

It is evident that theoretical considerations are of little value unless
supported by facts, and for this reason the latter should be clearly set
forth and particularized, apart from theories, so that there may be some
hope of securing, ultimately, a uniformity of opinion concerning at least
what occurs in the field.

As far as our observations have extended, we have never seen an exam-
ple of the granite breaking through the felsite or enveloping its frag-
ments. In every case in which we could determine the relations of the
rocks the felsite occurred as an eruptive penetrating the granite.

Before proceeding to point out the special localities in which the gran-
ite is cut by the felsite, let us consider the evidence, apart from the dikes,
which proves the truly igneous nature of the latter rock.

Upon Break-heart Hill in Saugus and to the west towards Main Street
there occurs an extremely heterogeneous mixture of banded felsite with
grayish fragmental material, which in its external aspect resembles, to a
considerable extent, ordinary ashes. The true nature of this grayish
rock was not suspected until the microscope revealed the fact that it
contains many of the splinter-shaped or chip-like sharp-edged fragments
whose peculiar forms belong to the volcanic glass of rhyolitic tufas. The
forms are so characteristic, and in this case so well preserved among the
other ashy material, that there can be no doubt of their identity. The
fragments, as we would expect,* are no longer volcanic glass, but quartz,

* On the Classification of Rocks, by M. E. Wadsworth; Bull. Mus. Comp. Zoél.
at Cambridge, Mass., Vol. V., No. 13.

MUSEUM OF COMPARATIVE ZOOLOGY. 169

which is the product of alteration. The composition of this interesting
rock, and its petrologic relations, we believe, establish beyond question
that it is a veritable ancient volcanic ash. ‘There is considerable
evidence, though not yet decisive, for want of further microscopical inves-
tigations, that these ashes are distributed in patches throughout a con-
siderable portion of the region occupied by the felsites.

It seems to be certain, therefore, that there has been within this re-
gion a true volcanic outburst by which the ashes were produced, and
that anterior to the formation of the ashes, or perhaps about the same
time, there was an eruption of felsitic lava, with which the ashes became
entangled in the complicated manner we find upon Break-heart Hill.

The banding so well marked in the felsites upon the western shore of
Marblehead Neck until quite recently has been considered stratification,
and therefore appeared to be a fatal argument against the theory of
those who regard the felsites as exotic. Dr. Wadsworth was the first to
consider the banding a fluidal structure, equivalent to that so prominent
in the modern rhyolites, and consequently of igneous origin. It is of
common occurrence, especially in the silicious felsites of Lynn, Saugus,
and Melrose; and from the fact that where it is found in felsite, forming
distinct dikes or tongues in the granite, or enveloping fragments of other
rocks, the banding is parallel to the line of contact, there seems to be no
good reason for doubting that it was produced by the flowing of the fel-
sitic matter in a state of fusion. The extreme complexity of the band-
ing upon Break-heart Hill and at places in Marblehead Neck cannot be
satisfactorily explained by any other supposition, and it is scarcely nec-
essary to add that under the microscope the phenomena of the banding
are wholly at variance with those found in sedimentary rocks and com-
pletely in harmony with those of altered rhyolites. The banding, there-
fore, instead of furnishing an argument in favor of the sedimentary
origin of the felsites, is proof of their eruptive character.

Since the relation of the felsite and granite has been the subject of
such discrepant statements, we shall point out the localities in which, as
it seems to us, the relation is clearly exposed. Within the granite
southwest of Spot Pond a dike of somewhat pinkish felsite occurs near
the top of a high hill west of the north end of Brooks’s Lane, where it
enters Forest Street. Further northward and nearer to Forest Street
there are at least half a dozen smaller dikes of a similar felsite in the
granite. That these masses of felsite are true dikes and not included
fragments within the granite is proved by the fact that they not only
send irregular tongues of felsite from the main dike into the adjoining

170 BULLETIN OF THE

rock, but also that they hold within themselves detached fragments of
the granite which they penetrate. The small patch of granite northeast
of Prospect Hill, Malden, is penetrated by one of the largest felsitic
dikes of this region. It may be seen in the cliff directly opposite Faulk-
ner’s station. Along the Newburyport turnpike in Malden there is a
small area of granite to which we have elsewhere * alluded. Mr. Crosby ¢
regards this rock as granitoid petrosilex. We placed it among the gran-
ites not only on account of its granitic structure, but from the fact that
it is clearly distinct from the adjoining felsite. In a gravel-pit upon the
east side of the turnpike, a short distance north from Salem Street, sev-
eral junctions of the granite and felsite may be seen. The felsite is in
some places slightly banded along the contact, and the line of junction
between the two rocks can be readily traced from the south part of the
gravel-pit for a considerable distance over the hills to the eastward.
Passing a short distance northward along the turnpike several low cliffs
appear upon the left. In the second of these, two well-marked dikes of
reddish felsite occur. One of them is about five feet in width, the other
about twelve feet, and they cut through an almost vertical cliff of the
granite twenty-five feet in height. These dikes may be traced at intervals
for nearly a quarter of a mile to the northeast. The granitic rock of/this
area, as well as that northeast of Prospect Hill, is quite different in its
general aspect from the granite of the larger areas to the northward ; but,
so far as the facts are known, there seems to be no good reason for sup-
posing that it is not granite, or that its relation to the felsite is different
from that of the other granites.

The large granitic mass extending from eastern Melrose into central
and northern Saugus is bounded upon the south and east and partly upon
the west by felsite, so we would expect to find within this area numerous
exposures of the two rocks in contact, and thereby determine their rela-
tions. Near the eastern end of Long Pond in Saugus there are several
distinct dikes of felsite in the same granite which at the west end of the
pond, about one fourth of a mile distant, as already mentioned, contains
well-marked inclusions of the stratified group. One of the most dis-
tinctly marked dikes may be found upon the eastern end of the granite
hill north of Essex Street, about a quarter of a mile northwest from the
Newburyport turnpike. The strike of the dike is N. 20° E., and it
varies, within a distance of sixty feet, from six to ten feet in width.

The most interesting and instructive exposures of the stratified group,

* Proc. Bost. Soc. Nat. Hist., Vol. XX.; p. 357.
+ Contributions to the Geology of Eastern Massachusetts, p. 78.

MUSEUM OF COMPARATIVE ZOOLOGY. 171

granite and felsite near together, are to be found upon Break-heart Hill in
Saugus. It is to this locality that Mr. Crosby refers when he says: *
“On the high hills to the west of the private road running from Forest
Street and Central Brook to Water Street we have, perhaps, the finest
example of the extravasation of the granite yet observed in this region.
The exposures of the rock here are remarkably good; and the granite
is coarse and sharply defined where it penetrates the adjoining petrosilex
and hornblende slate in irregular dykes, or envelops isolated masses of
these rocks that have been wrested from the parent beds.”

Concerning the fact that the granite envelops detached fragments of
the stratified group there can be no doubt ; but when we come to exam-
ine the relations of the felsite and the granite, the evidence is not so
easily deciphered. The top of the hill is composed of a mixture of
felsite and volcanic ashes, which extends over the southeastern slope,
meeting the rocks of the stratified group; to the northward, a short
distance, this mixed mass is limited by the coarsely crystalline granite
containing the stratified fragments; and to the westward it connects
with a large area of similar rocks forming the high hills near by in that
direction. Within the small area of this complex rock there are two
patches of granite. One of these, with a diameter of about twenty-five
feet, upon the western brow of the hill, has its side penetrated by a
tongue, at least six feet in length, of very distinctly banded felsite.
The banding is also very distinctly marked at several places along the
periphery of the granite, and in every case it is parallel to the line of
contact between the two rocks. The smaller patch of granite upon the
southern slope of the hill is completely enveloped by felsite. Although
the felsite in this case is not banded, it apparently sends tongues into
the granite, and, near the junction of the two rocks, it envelops small
fragments of the larger mass which it surrounds. Although there are
other exposed contacts of the felsite and granite in the neighborhood,
none were observed to furnish important evidence bearing upon the
relations of the two rocks. The banding of the felsite is undoubtedly
of igneous origin, and its occurrence about the granite, together with
the tongues of felsite penetrating the granite, and fragments of the
latter rock enveloped by the former, are phenomena which, as it seems
to us, can be explained only by supposing that the felsite flowed through
and around the granite.

The well-marked dikes of felsite cutting the granite between Fishing
Point and Phillips Beach on the Swampscott coast, as first pointed out

* Contributions to the Geology of Eastern Massachusetts, p. 78.

Hye BULLETIN OF THE

by Dr. Wadsworth, as well as the numerous examples found upon the
coast of Marblehead Neck, conclude an array of facts which establish,
beyond dispute, not only that the felsite is a truly eruptive rock, but
also that in every case where we could determine its relation it is
younger than the granite which it penetrates.

The relation of the felsite to the stratified group is the subject of very
different opinions, and for this reason it seems proper to present in
detail the evidence we have observed bearing upon this question. If
the phenomena described sustain the conclusions already drawn, viz.
that the stratified rocks of Medford, Stoneham, Melrose, and Saugus
are older than the eruptive granites of that region, and that the felsite
is a truly eruptive rock younger than the granites, it is evident that
there can be no gradual passage from the felsite into the stratified
group.

Mr. Crosby,* who has done so much on the geology of Eastern Massa-
chusetts, refers to the region west of the Boston and Maine Railroad in
Melrose as the one which “ places beyond question the fact that there
is a gradual transition between the quartzite and petrosilex, and that
portions of the latter rock are intercalated in the stratified group.”
This group is well exposed near the railroad, a short distance south of
the Melrose station, and extends southwestward, parallel with the
general strike of the formation, across Spot Pond into Medford. Excel-
lent outcrops, perhaps the best of the stratified group in this region,
form a part of the northern shore of the pond. The felsites and strati-
fied rocks are exposed within several hundred yards of each other upon
opposite sides of Washington Street, Melrose, a short distance east of
the Melrose-Stoneham line. The exposures in both cases are within
the regions marked felsite by Mr. Crosby. Those upon the north side
of Washington Street are distinctly sedimentary rocks, while the rocks
in the cliffs to the southward are well-marked felsite, slightly porphy-
_ ritic, of the kind forming the mass of the Malden Highlands. Although
I have examined several times the region between Spot Pond and Long
Pond, where the stratified group meets the felsite to the southward, I
have not been able to find the two rocks in place exposed nearer to
each other than at the locality described ; and although in the present
state of our knowledge the existence of a ‘gradual transition ” or inter-
calated felsite in the stratified group cannot be denied, it may be stated
that careful search has not revealed to us the slightest evidence in favor
of Mr. Crosby’s positive assertion. It is hoped that the exposures

* Contributions to the Geology of Eastern Massachusetts, p. 106.

MUSEUM OF COMPARATIVE ZOOLOGY. LTS

which place such an important fact beyond question will be described
in detail, so that other observers may obtain the evidence.

Fortunately we need not depend for a knowledge of the relations of
the rocks in question upon a region in which the absence of exposures
along the line of contact renders it difficult to tell what may be true.
Upon the northern boundary of the stratified group, from Break-heart
Hill westward towards Main Street, the relations of the rocks are clearly
exposed. Between Break-heart Hill and Main Street several distinct
contacts of the felsite and quartzite may be seen, and there are no indi-
cations whatever of a transition between the two rocks. It will be
remembered that, in describing Break-heart Hill, it was mentioned that
the complex mixture of felsite and ashes extends from the summit down
the southeastern slope to the rocks of the stratified group. Near the
middle of the slope facing Mr. Edmond’s house is a small ledge, furnish-
ing an excellent exposure in which the felsite, with contorted banding,
overlies unconformably at a large angle the upturned edges of the
stratified group. The rocks beneath are in part quartzite interstratified
with other rocks of the same group, and the line of contact sloping down
the hill is well marked. A short distance to the eastward the banding
in the felsite and the distribution of the ashy material has the same
general slope as the plane of contact.

It seems to us that this very interesting exposure places beyond the
possibility of a doubt the conclusion that the felsite is younger than the
rocks upon which it reposes. A few rods to the southwest of the ex-
posure just noticed there is another, which shows apparently one side
of a dike of felsite cutting through the stratified rocks. The line of
contact is very distinctly marked and irregular, like that of an eruptive
rock, and is at right angles to the bedding of the adjoining rocks.
Distinct fragments of quartzite belonging to the stratified group are
enveloped by the felsite of this locality, and small ones have been found
embedded in the ashes.

The facts observed upon Break-heart Hill are in harmony with the
relative positions of the two rocks as determined by the relations of both
to the granite, and there appears to be no doubt that the stratified rocks
of Melrose and the adjoining towns are older than either the granite or
felsite.

Having considered the relations of the older rocks to the felsites, let
us turn our attention to the relations which the felsites hold to one
another. Mr. Crosby has shown that the rocks of the group vary widely
in chemical composition, and Dr. Wadsworth has called attention to

14: BULLETIN OF THE

the fact that upon Marblehead Neck the felsites are not all of the
same age.

The stratified group which we have already described separates the
adjoining felsites into two distinct areas, each of which includes several
felsites of different periods of eruption. The felsite which is so inti-
mately associated with the ashes upon Break-heart Hill occupies a con-
siderable portion of the area east of Main Street, and between Break-heart
and Little Castle Hills. A junction between the dark-colored felsite and
a pale pink felsite may be traced across the northern part of Little
Castle Hill, and southwest of this hill, about half-way to Main Street,
another distinct junction occurs along which there is very well marked
banding in the light-colored felsite, showing that it is the younger.
Neither of these felsites is very porphyritic.

Within the southern area, a short distance southeast of Long Pond,
Saugus, there is a small patch of a re¢, chiefly non-porphyritic felsite.
The region immediately south of the pond, and to the southwest as far
as the Boston and Maine Railroad, is occupied by a felsite which is
generally very porphyritic. The ground-mass of this felsite varies
somewhat in color, but it is usually light pink or pale purple, and
besides being the most completely and uniformly porphyritic. felsite of
this region, very frequently envelops fragments of older rocks. It might
properly be designated the porphyritic, pebble-bearing felsite, for these
two features are comparatively uniform throughout the wide area occu-
pied by this beautiful rock. The red non-porphyritic felsite, to which
we have already referred, forms a very clearly marked junction with the
porphyritic felsite about one fourth of a mile southeast of the eastern
end of Long Pond, and the porphyritic felsite, which is distinctly banded
along the line of contact, penetrates the adjoining red felsite, and en-
velops many of its fragments. Among the enveloped fragments in the
porphyritic felsite are found a few of granite, —a fact which accords with
those we have already discussed in showing that the granites are older
than the felsites. The pebbles of the old felsite are numerous and widely
distributed in the porphyritic felsite, and the evidence is so complete
and well marked, that, as it seems to us, there can be no doubt that
the two felsites were extruded at different periods.

About a third of a mile southeast of Swain’s Pond in Melrose the
porphyritic felsite is cut by a dike of what appears to be a third felsite,
which is non-porphyritic and of a gray color. The dike has very irregular
junctions, varies in width from a foot to eighteen inches, and can be
traced across an exposure for a distance of thirty feet. The youngest

MUSEUM OF COMPARATIVE ZOOLOGY. 175

of the felsites does not appear to have a very extensive development
in that region.

Within the felsites many junctions of apparently different rocks
may be seeh ; but because, as it appears to us, it may be possible for dif-
ferent parts of the same eruptive mass to form distinct junctions with
each other, we were not inclined to accept junctions alone as evidence
of difference in age unless supported by other facts. It appears to be
evident, however, that not only at Marblehead Neck, as shown by Dr.
Wadsworth, but also in each of the two areas of felsite we have explored,
there were at least two distinct eruptions of felsite.

That some of the felsites are distinct in age is clearly shown also by
their relations to the fragmental rocks, the so-called breccias, with which
they are associated ; but these relations can be considered to better ad-
vantage after the latter rocks have been described.

Fragmental Rocks.

The complex group of rocks included under the above name embraces
those commonly called breccias in this vicinity, and is composed of
members wholly distinct in origin and composition. The coarse frag-
mental rocks, whose fragments may be either angular or well rounded,
are perhaps more abundant than the sandstone and finer-grained rocks,
Most of these rocks are composed of fragments of highly altered igneous
rocks, the felsites and granites, and properly belong to the tufas, or, accord-
ing to Dr. Wadsworth’s classification,* the porodites. There are, however,
a number of localities where the conglomerate is composed chiefly of
pebbles of quartzite from the stratified group.

The volcanic ashes to which we have already referred as occurring in
the neighborhood of Break-heart Hill are undoubtedly of igneous origin,
but in other regions the material is distinctly stratified, and must have
been produced by aqueous agencies. Although we have no evidence
which proves certainly the relative age of the ashes, it seems probable,
from the fact that they are so intimately mixed with the oldest felsite,
that they were produced about the same time with the felsite, and earlier
than the stratified porodites (tufas) and conglomerates. It is sometimes
extremely difficult to distinguish in the field between a recomposed rock
and an eruptive one which has, at the time of its extrusion, picked up
many fragments.t Only those exposures which are quite certainly of

* Bulletin of the Mus. Comp. Zoél., Cambridge, Mass., Vol. V., No. 13, p. 280.
t See paper by the writer. Proc. B. S. N. H., Vol. XX. 355.

176 BULLETIN OF THE

sedimentary origin will be noticed ; although they are quite numerous,
they are comparatively small. Mr. Crosby was the first to notice the
stratification of these rocks, and pointed out the locality at Dungeon
Rock, Lynn, where the material is fine, and apparently all derived from
the felsites. Another similar locality in which the stratification is well
marked occurs along the water-pipe between the reservoir and the water-
works, Lynn. In these areas it is almost impossible to tell, upon a
weathered surface, that the rock is fragmental. These exposures were
accidentally brought to light by quite extensive excavations, and it is
possible that some of what is now regarded as felsite may be a recom-
posed rock, so like felsite (from which it was made) in its external
appearance as not to be distinguished from it by the unaided eye. The
area of porodites and conglomerates of Vinegar Hill and Pirates’ Glen
is probably the largest area of these rocks in this region. In the same
locality there are several small patches of granite mixed with the frag-
mental rocks which are in places distinctly stratified.

One of the most interesting exposures of the stratified porodites is
upon a high hill, a short distince south from Saugus, and near the east
side of the road leading to Sweetser’s Corner. The greater portion of
the hill is felsite, but upon its northern slope occurs the most beautiful
coarse tufa of this region. It is tilted so as to be standing nearly or
quite vertical, with a strike N. 70° E. At this place the thickness,
measured directly across the strike, is about 150 feet, and may be greater,
but for want of exposures the excess beyond 150 feet cannot be deter-
mined. This is the only locality we have found to furnish an opportu-
nity to determine the thickness of the fragmental rocks.

An exceptional conglomerate occurs a short distance west of the
Saugus station, near the railroad. Its peculiarity consists in its associa-
tion with the granite, and that it is composed almost wholly of granitic
débris. Some of the pebbles are large and well rounded, and the mass
seems to lie directly upon the rocks from which it was derived. An
unsuccessful attempt has been made to use this material for the bases
of gravestones.

Between Cliftondale station and the Newburyport turnpike there is
quite a large area of conglomerate containing a considerable proportion
of quartzite pebbles. A smaller area of finer material occurs near the
end of Granite Street, by the spring, about a third of a mile north of
Maplewood.

A most interesting and varied locality in which the stratification is
well marked may be found about a third of a mile southeast of Swain’s

MUSEUM OF COMPARATIVE ZOOLOGY. LTT

Pond in Melrose. Although the locality is small, it embraces a variety
of fine-grained, red, argillaceous rocks, sandstones, and a very coarse con-
glomerate composed almost wholly of pebbles of quartzite from the
stratified group.

In the base of a small hill a short distance northeast of Oak Grove
station, on the Boston and Maine Railroad, the fragmental rocks of this
group are well exposed. They extend into the base of Prospect Hill,
and on the opposite side of the valley are exposed near the base of
the Malden Highlands. Within the Highlands there are two small
areas of tufas, one on each side of Highland Avenue along the Malden-
Medford line. The conglomerate of West Medford, which is well de-
veloped along Purchase and Mystic Streets, resembles to a considerable
extent some parts of the Roxbury conglomerate ; but Mr. Crosby is most
likely correct in connecting it with the fragmental rocks so intimately
associated with the felsite.

Within the felsites north of the stratified group we have found only
two small areas which, as it seems to us, are of sedimentary origin. One
of the patches lies upon the first hill north of Oak Street, a short dis-
tance west of Nahant Street (Main Street), Wakefield, and the other
is upon Candle-wood Hill, northeast of the Stoneham station on the
Boston and Maine Railroad. It is very probable that a number of areas
of sedimentary rocks have escaped our notice, but we feel sure they do
not occupy the large areas over which they have been represented to
extend. The very porphyritic felsite occupying the region lying between
Long Pond, Saugus, and the Malden Highlands contains, as we have
already stated, many pebbles of other felsites, and some of granite, but,
like that at Red Rock, Lynn, it is by no means of sedimentary origin.

We have elsewhere * shown that some of the felsites are younger than
the fragmental rocks so intimately associated with them, and it remains
in this connection to point out the facts upon which this inference
is based.

In the conglomerate about a fourth of a mile north of Cliftondale
station there is a dike of pinkish felsite which is clearly eruptive
through the fragmental rocks of the same locality. A similar phenome-
non may be seen north of Oak Street, Wakefield, where a distinct tongue
from the black-edged dike penetrates the adjoining fragmental rocks.
The best locality, however, for observing the relations of these rocks is
southeast of Swain’s Pond, where the porphyritic felsite not only pen-
etrates in the form of small, irregular dikes the fragmental rocks, but

* Proc. Bost. Soc. Nat. Hist., Vol. XX., p. 364.
VOL. VII.—NO. 2. 12

178 BULLETIN OF THE

also in one exposure distinctly overlies them. This relation enables
us to understand how it happened that the coarse quartzose conglomerate
is completely surrounded by felsite which does not appear to have en-
tered into its composition. The porphyritic felsite being younger than
the fragmental rocks, it is not difficult to explain the fact that it contains
so many pebbles. In Prospect Hill, Malden, and the small hill near by,
just northeast of the Oak Grove station, the porphyritic felsite appar-
ently overlies the fragmental rocks of the same locality. The dark-
colored, less porphyritic felsite of the Malden Highlands is closely related
to the porphyritic one to the eastward, and there is good reason to be-
lieve that the former, like the latter, is younger than the tufas of that
region. The tufaceous rocks along the Malden-Medford line north of
Highland Avenue are composed almost wholly of very silicious felsites,
unlike those by which the small area is completely surrounded ; a fact
which, as it seems to us, can be explained most satisfactorily by sup-
posing that the dark felsite of the Highlands had not been spread upon
the surface in its present position at the time the fragmental rocks were
formed. The evidence we have given seems to us sufficient to fully
establish the conclusion that some of the felsites are younger than the
fragmental rocks with which they are intimately associated ; and on
the other hand, it cannot be doubted that these fragmental rocks are
more recent than the felsites of whose débris they are largely composed.

Diorite.

The diorite adjoins the felsite for only a few miles along the north-
western boundary of the latter, between Melrose Highlands and Smith’s
Pond (Crystal Lake), Wakefield. The line of contact is generally coy-
ered, and the two rocks were not seen upon the same exposure north of
West Hill, near the Stoneham station * on the Boston and Maine Rail-
road. Upon this interesting hill we find a complex mixture of almost
all the rocks of the region, and it appears to us that the diorite pene-
trates and envelops not only the stratified group, but also the granite
and felsite. Distinct fragments of the granite and felsite have been
seen in the diorite at several places. Similar phenomena may be seen
upon the hills in Stoneham, near the south side of Franklin Street,
where the eruptive diorite penetrates the granite, and cuts directly
across the bedding of the stratified quartzites and schists. In that region
the granites, diorites, aud rocks of the stratified group are intermingled

* The name of the post-office at Stoneham station is Melrose Highlands.

MUSEUM OF COMPARATIVE ZOOLOGY. 179

in a very complicated manner, but we have not been able to find any
evidence which would lead us to suppose that there is a gradual transi-
tion from any one of the rocks into another of the same locality. It
seems evident to us that the diorites are truly eruptive rocks, and that
their extrusion has taken place since that of the granite and felsite
which they penetrate.

Diabase and melaphyr, so abundant in the neighborhood of Boston,
are found in very distinct dikes, cutting all the other rocks, and close
the series of eruptive rocks in which there seems to have been, in the
order of extrusion, a general progress from silicious to basic rocks.

The relative ages of the rocks in the region we have explored, as it
seems to us, have been pretty clearly established, but the position of
the whole series in the geological column is a matter concerning which
we have seen very meagre and conflicting evidence. The slates, sup-
posed by some to be primordial, lying between the Charles River and
the hills of Medford and Malden, have not been found, so far as we
know, in contact with the eruptive rocks to the northward. On the
north side of the Saugus branch of the Eastern Railroad, between
Faulkner’s station and Maplewood, the slates are exposed within about
one hundred and fifty feet of the hills of eruptive rocks upon the north
side of Salem Street. The slates dip steeply (66°) to the northward, as
though they were plunging beneath the other rocks. It may have been
this fact which led Prof. John W. Webster, many years ago, to assert
that.the transition rocks (slates, etc.) were overlain by the porphyries of
Malden.

In the rocks of the stratified group, so far as we know, fossils have
never been found ; and were it not for the fact that the Roxbury con-
glomerate contains numerous pebbles of quartzite, apparently derived,
at least in part, from the rocks of the stratified group, I can see no good
reason for supposing the stratified group to be pre-paleozoic. The same
conglomerate contains pebbles of felsite, but whether any of them are
from the felsites now exposed along the northern margin of the Boston
basin is a question which, for its satisfactory solution, will require much
more thorough and careful work than has yet been done in this region.

Conclusions.

The facts we have observed in the region described in the foregoing
paper appear to establish, for that region, the following conclusions : —
The stratified group contains the oldest rocks of which we have any

180 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.

knowledge in that region, and, before the extrusion of the more recent
eruptive rocks, they probably had a much wider distribution upon the
surface than they now have.

The granites are not derived by metamorphism from any part of the
series of rocks (stratified group) which they envelop, but are truly
eruptive rocks, whose extrusion has occurred since the formation of the
stratified group. Therefore the granites, as we know them in their
present position, are younger than the stratified group.

The felsites are eruptive rocks, more recent than the granites. There
were at least two eruptions of felsite in each area, and in the southern
area there were probably three eruptions.

The fragmental material associated with the felsite upon Break-heart
Hill is a volcanic ash; elsewhere the fragmental rocks have generally
been formed of material eroded and deposited by water.

The very porphyritic felsite between Long Pond and Prospect Hill,
part of the felsite of Wakefield and at Cliftondale, and probably the
dark-colored felsite of the Malden Highlands, are younger than the
tufas and conglomerates with which they are associated.

The diorites are eruptive, and younger than the felsites.

The diabases and melaphyres are the youngest eruptive rocks of this
region, and there has been, in the order of eruption beginning with the
granites, a general progress from silicious to basic rocks.

On an Occurrence of Gold in Maine. By M. E.
WaAbsWortu.

IND: 3:

Tue gold under consideration here is found on Seward’s Island, a
small island in the town of Sullivan, Hancock County. The gold is
found in quartz veins cutting an eruptive mass of diabase. This diabase
forms a dike of about 40 feet in thickness, lying approximately parallel
to the bedding of an indurated fine-grained argillaceous mica schist ;
all dipping nearly S. 30° W., 24° to 42°. The dip averages about 35°,
and the strike is far from being uniform. Crossing the diabase at various
angles, but generally from north to south, are segregated quartz veins.
In some places the rock is a confused reticulated mass of these veins, with
patches of diabase lying between them. The veins vary in width from
a mere seam to even a foot in breadth. Starting where only one or a
few of them are visible, they gradually increase in number until they
become quite numerous, while they will doubtless be found to fade
away as they began. The diabase and schists are cut by several dikes
of diabase running approximately at right angles to the strike of the
schist, or parallel to the veins. The vein stone is quartz, together
with some calcite, tremolite, and chlorite, and carries tetradymite and
gold.

So far as examination has been made, the veins in the diabase carry
gold, and the decomposed diabase immediately adjacent to the quartz
veins also contains that metal to a greater or less extent. The gold
occurs principally in small grains in the vein in connection with the
tetradymite, bits of decomposed diabase, and in the cavernous portions,
but not in the compact quartz of the vein itself. The tetradymite is
in irregular grains and masses, showing a brilliant metallic lustre and a
well-marked basal cleavage. The locality is worked for its gold, and
was visited by the writer in December last.

CAMBRIDGE, Mass., January, 1881.

VOL. VII. — NO. 3.

le ad

No. 4.—A Microscopical Study of the Iron Ore, or Peridotite, of
Iron Mine Hill, Cumberland, Rhode Island. By M. E. Wanvs-
WORTH.

Tur attention of the writer was first particularly called to this forma-
tion by some specimens presented to him by Mr. H. B. Metcalf in the
spring of 1880. These did not appear to the writer to be any common
ore of iron, but rather fragments of a basic eruptive rock containing
much iron. Sections were accordingly made which revealed its true
character.

The formation was described by Dr. Charles T. Jackson in his report on
the Geological Survey of Rhode Island in 1840. He states that lron
Mine Hill “is a mountain mass of porphyritic magnetic iron ore, 462
feet in length, 132 feet in width, and 104 feet in height above the
adjoining meadow. From these measurements, which were made over
only the visible portion of this enormous mass of iron ore, it will appear
that there are 6,342,336 cubic feet of the ore above natural drainage.
. . . Its specific gravity is from 3.82 to 3.88. . . . This ore is remark-
able both on account of its geological situation and its mineralogical
and chemical composition. It appears to have been protruded through
the granite and gneiss at the same epoch with the elevation of numerous
serpentine veins which occur in this vicinity. This will appear the
more probable origin of this mass, when we consider its chemical com-
position in comparison with that of the iron ore, which we know to
have been thrown up with the serpentine, occurring on the estate of Mr.
Whipple, and the fact that the ore at Iron Mine Hill is accompanied by
serpentine mixed with its mass in every part, gives still greater reason
for this belief.” (/. ¢., pp. 52, 53.)

He gives as the result of his chemical analysis of the “ Porphyritic
Tron Ore from Iron Mine Hill, Cumberland,” the following (/. ¢., p. 53) : —

ete ee ee Pe yp i pee A000
ee Sete eh ss 6p (LS.10
ere Geer eels ae! Yn 2 4s 2d.60

teria eevee el te 2 ep xy. 2240
Pee i ee a ei lea ile oe «© «©7200
re ee Get at Sey is, #00
UE MOMMA oy ioe Mist Wa eae Ge et et yey 25.00
ee tt ne) eh ee el oe vet > 2-60

mnt mrenee, Ware, neces hia Wilk. 9100.00

VOL. VII.— NO. 4.

184 BULLETIN OF THE

In 1869 the Rhode Island Society for the Encouragement of Domestic
Industry published a report relating to the coal and iron in Rhode
Island, from which we glean the following. The iron ore is regarded
as practically inexhaustible, the mass at Iron Mine Hill visible above
drainage being estimated at two millions of tons.

“Tt is also conceded, as regards quality, that the Cumberland ore is
free from sulphur and phosphorus, the most common and worst im-
purities, and that it contains manganese, the most, prized of all the
elements found in connection with iron. For these reasons the Cumber-
land ore is sought by manufacturers at a distance, to mix with softer
ores and improve their quality, and is now exported from this State for
that purpose.”

It seems that this Iron Mine Hill ore was employed in 1703, mixed
with the hematite of Cranston, R. I., for the casting of cannon. The
work was done at Cumberland, and, in part at least, “the cannon used
in the celebrated Louisburg expedition, in 1745,” were cast from these
ores. The manufacture was abandoned in 1763, owing to an explosion
of the furnace, by which the proprietor was killed.

During the administration of John Adams the same ores were also
used for the manufacture of cannon. It seems that the Cumberland
(Iron Mine Hill) ore was employed in the manufacture of charcoal iron
at Easton, Chelmsford, and Walpole, Mass., as late as 1834. “The
Cumberland ore, mixed with equal quantities of Cranston hematite or
bog ore, produced, for a long period, a charcoal iron unsurpassed in this
country. . . . The Cumberland ore contains an uncertain percentage of
titanium, which, while it improves its quality, helps make it refractory.
The ore is porphyritic, the magnetic oxide being associated with earthy
minerals, principally feldspar and serpentine.” It would seem that in
1869, and before, the ore was largely shipped to Pennsylvania to mix
with other ores.

A letter of Professor R. H. Thurston, published in this report, states :
“The Cumberland iron ore is of the kind known to mineralogists as
‘ilmenite’; among metallurgists as ‘ titaniferous magnetic ore,’ and iron
manufacturers, on account of its peculiar value for producing steel,
would term it a ‘steel ore.’ ... The Cumberland ore is conveniently
located and of inexhaustible extent; it is perfectly free from noxious
elements, though somewhat refractory ; it will furnish a very strong
iron or a most excellent steel ; it can be smelted within the State at a
profit ; it can be made directly into steel at a much greater profit ; steel
made from it will bring the highest prices in the market.”

MUSEUM OF COMPARATIVE ZOOLOGY. 185

Professor Thurston states that the mean of various analyses made of
this ore is about as follows : —

em coe A) a oP Be

Soo ie ss Me IO nea (07
2-3
aaa} . 44.88

cel. RE eee Se ee ce ee
Re a en es ae a oa ate ote oe, 0.60
ROE s te oe atic es, Cul eye ws at oa, LOL
Ty Le A ar aS le ae A
DE ee ee ce ey a sw , | O20
TIHAGIOSN on ee ee ee ge oe we ew LOS

Ral tos Se een ee ee ee ewe og sc: KOOLOO

The ore on one side of the hill, where it has been most extensively
quarried, shows a dark, somewhat resinous groundmass, holding large
striated crystals of feldspar. The resinous lustre and greenish-yellow
color, as observed under the lens, are caused by the presence of olivine.
The olivine becomes more strongly marked on the slightly weathered sur-
faces seen on the faces of the quarry. Under a lens of high power, the
olivine shows clearly on the fresh fractures. The olivine in weathering
decomposes toa yellowish and reddish-brown ferruginous powder, leaving
the other constituent of the rock, the magnetite, well marked. The
magnetite decomposes more slowly, and forms an incoherent mass after
the decay of the olivine. The rock gelatinizes with hydrochloric acid,
and yields a titanium reaction. A fragment allowed to stand a day or
two in weak hydrochloric acid yielded gelatinous silica copiously.

A section made with special reference to the feldspar crystals shows
large porphyritic crystals of the latter enclosed in a mass of magnetite
and olivine.

The magnetite forms irregular, more or less connected masses, making
a sort of sponge-like structure. Its rounded and irregular cavities are
filled with olivine, which also occupies the interspaces between the mag-
netite masses. The olivine is in rounded forms, which sometimes show
one or more crystal planes. It is cut through by numerous fissures, that
usually show a ferruginous staining along their sides. The olivine also
holds grains of the magnetite. Except the fissuring and ferruginous
staining, the olivine is comparatively clear, and shows little signs of
alteration.

The plagioclase feldspar shows well-marked lines of cleavage and frac-

186 BULLETIN OF THE

ture, and is somewhat kaolinizéd along these lines. It contains a few
irregular flakes of biotite together with grains of olivine and magnetite.

The order of crystallization appears to have been, first the magnetite,
then the olivine, and lastly the feldspar.

This rock is similar to the celebrated iron ore of Taberg, Sweden, as
described by A. Sjéren in the Geologiska Foreningens Forhandlingar
(1876, III. 42-62; see also Neues Jahrbuch fiir Mineralogie, 1876,
434, 435). The Taberg rock has been worked as an iron ore for over
three hundred years. This Swedish ore is called by Sjoren “ magnetite-
olivinite.”

The feldspar is confined to the peridotite found on one side of the
hill, where the peridotite passes into a compact greenish-black rock,
showing patches of serpentine and grains of magnetite. From this fact
it seems necessary to regard the feldspar as abnormal and local in the
rock, which in general is composed of olivine and magnetite or their
alteration products.

The structure remains about the same in the non-feldspathic portions
as it is in those before mentioned as holding feldspar. But the olivine
is entirely changed to a greenish serpentine which shows beautiful
fibrous polarization. The serpentine retains the form of the olivine
grains, their inclusions, and the network of fissures before mentioned.
In some of the sections considerable carbonate was seen, presumably
dolomite. In one section part of the olivine grains, especially towards
their interior, remained unchanged, but on their edges they were altered
to serpentine. Another change was observed here: the formation of sec-
ondary crystals of irregular outline that belong probably to actinolite.
Some are elongated and narrow ; others are short and broad, traversed
by cleavage planes. They evidently belong to the monoclinic system.

The origin of this rock could not be told from its field relations, as its
contact with any other rock could not be found. Since the only method
in which its origin can be absolutely shown cannot be used without expen-
sive excavation, it only remains to give the probabilities so far as ascer-
tainable from the mass itself. Such microscopic characters and mineral
association have been, so far as we know, only found in eruptive rocks when
the origin of such rocks has been studied with sufficient care to determine
it. Hence we must conclude it is most probable that this mass is erup-
tive also, until found to be otherwise.

It closely resembles in structure and composition some of the mete-
orites, except that its iron is oxidized and not in a native state, —a, re-
semblance which for others of the peridotites has long been pointed out.

MUSEUM OF COMPARATIVE ZOOLOWY, 187

It is rocks of this character, as has been suggested by others, that give
us the most probable clew to the interior composition and structure of
the earth.

The rock in the field shows, to our mind, no signs of structural planes
that should be referred to sedimentation. On one side the rock is mas-
sive and jointed, and on the other it is jointed in fine parallel planes.
This portion of the rock is more highly metamorphosed than the other,
and, as is usual in highly altered eruptive rocks, joints parallel to cer-
tain lines of pressure occur. The writer has seen this structure in many
rocks that were indisputably eruptive, forming well-marked dikes in
other rocks.

A rod away from the main mass of the iron ore, near one end, some
serpentine appears that cannot be directly connected with the other peri-
dotite. Microscopically its characters and structure are the same as
the main rock, and there is no reason to regard it as distinct. The rock
nearest to the peridotite is a mica schist some hundred feet away. It
shows no characters that would indicate the transition of the ore into it.

The locality was visited by the writer in October last, in company with
Professor A. S. Packard, Jr., of Brown University, and Mr. T. S. Battey, of
the Friends’ School, Providence, R. I. To the latter gentleman I am
especially indebted for a copy of the paper of the Rhode Island Society
before mentioned, and for other favors.

This examination may serve as an illustration of the aid that micro-
scopical lithology may be to the practical side of life, since now, for the
first time since this rock has been worked, can the ironmaster who
wishes to use it approach understandingly the metallurgical problems it
presents ; whether he desires to employ the rock as a whole, or to con-
centrate the magnetite first.

CAMBRIDGE, Mass., May 13, 1881.

No. 5.— Observations wpon the Physical Geography and Geology of
Mount Ktaadn and the Adjacent District. By C. E. Hamiiy.

Tue “Geological Map of Northern Maine,” that accompanies the
“Preliminary Report upon the Natural History and Geology of the
State of Maine,” for 1861, represents Mount Ktaadn* as included in a
large granite district, of which it is the culminating height. The area,
as delineated, is an ellipse, the axes being respectively about twenty and
forty miles in length, — the major axis running very nearly in a north-
east and southwest direction. Between the most northerly of the two
foci and the northeast border of the district, Ktaadn is placed ; while
between the other focus and the southeast margin are situated the
“Ebeme Mountains,” so called by the compiler of the map. The
Penobscot River, in a course intermediate with the two axes and oblique
to each, crosses the intervening country, which has a general elevation of
not more than 550 feet above sea level, and is thickly sown with lakes,

An excursion, of which this paper states results, was made in August
last, along a route that passes through nearly the whole length of the
supposed granite area. The special purpose of the writer at the outset
was to compare the granite of the lower grounds with that of Ktaadn
itself, which had been partially studied in August, 1879, and less care-
fully in 1869 and 1871; to find, if possible, at some points, the junction
of the granite with the surrounding stratified rocks ; and to continue the
exploration of Ktaadn with reference to completing the model of the
mountain, of which a heliotype is herewith presented. The route selected
comprises the northern seven miles of Schoodic Lake, fifteen miles of
forest travel to the Middle Joe Merry Lake, a course through this, the
Lower Joe Merry, Pemadumcook, and Ambejijis Lakes and their connect-
ing “throughfares,” and nine miles up the Penobscot to the mouth of
the Aboljacarmegus Stream, where the ascent of Ktaadn begins. From
the terminus of highways at Brownsville, the route measures about fifty
miles in length.

*The spelling Ktaadn is adopted in accordance with an opinion communicated to
the writer by J. Hammond Trumbull, of Hartford, the most eminent living authority
upon Indian dialects. Dr. Jackson, Thoreau, and a few others, have previously used
the same form.

VOL. VII. —No. 5.

190 BULLETIN OF THE

As almost nothing definite is on record respecting the depths of the
lakes that cover so large a portion of Northern Maine and British Amer-
ica, Soundings as numerous as circumstances permitted were made of the
lakes traversed. And though the Geological Reports represent the lakes
above named — except the first, of which no account has appeared in
print —as enclosed by shores made up of loose material, it was thought
best, in consideration of the remarkably low stage of water then prevail-
ing, to re-examine the shores and beds of the lakes in regard to their
composition. The same course was adopted for the Penobscot River,
especially at the five falls and portages that intervene between Ambe-
jijis Lake and Aboljacarmegus Stream.

The Lakes.

Schoodic* Lake, which shares its name with the larger Schoodic lakes
that lie on the eastern border of Maine, is in some respects the most
interesting of all that occur in this region. In his “ Water Power of
Maine,” Wells gives its area as sixteen square miles, and it is said to
have a length of ten miles, and in its central part to be two and a half
miles wide. It is free from islands, except at a single point upon the
eastern shore; and the forest that surrounds it shows no break in its
continuity, nor any other sign of settlement. The absence of islands
from the main body of the lake indicated deep water; but the rough
condition of the surface, when we boated over it, prevented us from try-
ing the depth. Our guide, Mr. Clapp, was employed to sound the lake
on his return, and the list of his numerous and careful soundings shows
it to be by far the deepest of all the lakes through which our route lay.
The part over which we passed is enclosed by shores of granitic detritus,
and there was nowhere to be seen any outcrop of the slates that under-
lie the whole surrounding district.

From the Schoodic to the Middle Joe Merry, our way was along a log-
ger’s road through continuous forest, which occupies a land surface very
level and entirely drift-covered, not one exposure of ledge being observed
in the whole distance of fifteen miles. Since our course through the
series of lakes will be apparent from inspection of the accompanying
map, no more need be said of it than that, favored in general by ab-
sence of wind, which, in a brief space of time, raises on these lakes a sea

* The name as applied to this lake is probably a refinement upon an earlier one,
found on the older maps, that of Skootwm Pond, itself perhaps the corruption of
some now unknown Indian name.

MUSEUM OF COMPARATIVE ZOOLOGY. 191

dangerous to boats, our examinations were continued from Pemadumcook
Lake to the foot of the North Twin, whence, returning to Ambejijis
Lake, we proceeded up the Penobscot.

For the first ten days our party consisted of six persons, two boats’
crews ;— one made up of my companion in two former trips to Ktaadn,
Dr. Crosby, of Waterville, Me., his son and nephew; the other, of Mr.
L. E. Blake, of Worcester, Mr. Clapp, and myself. In sounding length-
wise of the lakes, our boats often took opposite sides, and, landing fre-
quently upon the shores and islands, we carefully viewed the unusually
wide extent of rocky surface laid bare through the long-continued
drought. Very nearly the same conditions observed in one were found
to prevail in all the other lakes and their connecting streams. All are
bordered by detrital deposits, constituting occasional sandy or pebbly
beaches of small extent, but ordinarily made up of granite bowlders
having angles but little rounded by attrition, and which are often so
crowded together as to resemble walls. The smaller islands that stud
the lakes are sometimes banked up on all sides, or wholly covered over,
- with bowlders that have been borne to their present resting-places by
the action of ice in successive winters.

The only occurrence of rock in place, upon any of the lakes and
throughfares visited, was observed later upon the Upper Joe Merry,
which lay to the west of our route from Schoodic Lake to the Middle
Joe Merry. On the return of Dr. Crosby and his companions, at the end
of ten days, they ‘“‘carried”’ from the Middle to the Upper Joe Merry,
which has a length of about three miles. An examination of its mar-
gin, made at my request since I was myself to return from Ktaadn by
the Aroostook route, discovered upon a projecting point a granite ledge,
which for seventy-five feet forms the shore, rising steep ten feet from the
water. The southern half of the lake was crossed, but, with the excep-
tion named, only shores of drift were seen. Soundings were at the
same time taken, which will be given in the tables of depths.

Ambejijis Lake, uppermost of the series of expansions of the Penob-
scot known as the Pemadumcook chain of lakes, and but two miles long
by three fourths of a mile wide, receiving directly whatever of detritus
is swept down by the rapid river above, might be expected to be shal-
lower than the rest. It proved, however, to be deeper than the average
of the others, and here at one place was made the deepest sounding, 51}
feet, that occurred in the series. This lake was once a connecting link
between Pemadumcook and the larger Millinoket Lake on the east,
which, according to Wells, has an area of eighteen square miles, while to

192 BULLETIN OF THE

Pemadumcook, including Ambejijis, is assigned an extent of sixteen
square miles. The whole constituted one lake with two outlets, a case
rare in Maine. The formerly connected lakes are now separated by
a wide lagoon and a bush-grown sand-flat of four rods wide, products of
detritus brought down by the river. In times of flood, boats still pass
freely from one to the other. Millinoket at present has for its outlet a
stream bearing the same name as the lake, which, rising from the east-
ern end, flows south into Shad Pond, the lowest lake-like expansion of the
Penobscot. The lagoon, through which in 1871 we were barely able to
thrust our light boats, was now a broad surface of mud, impassable by
boat or on foot, and an effectual barrier to the extension of our sound-
ings and exploration into Millinoket. That this lake, as to its surround-
ings, is not unlike the neighboring ones, we are confident from our
recollections of a pretty careful examination of it made in the previous
visit. They agree with the statement of Dr. Jackson, that “the islands
are composed of the detritus of granite rocks, and the shores are com-
posed of the same materials.” * Seen from the summit of Ktaadn, the
outspread Millinoket Presents in a marked degree those flowing ontlines
of gently rounded bays which distinguish lakes enclosed by detritus
from the angular, irregular, and often narrow recesses that are said to
characterize lake basins excavated in solid rock. Of the latter class I
know not an instance in Maine.

The following tables register soundings made at intervals in what
appeared to be the deepest parts of the lakes we navigated. Casts were
made from the two boats, running some distance apart, and commonly in
nearly parallel lines. The columns marked A contain the results of
soundings taken by myself, with the assistance of Mr. Blake. The col-
umns B give soundings made by Mr. C. B. Wilson from Dr. Crosby’s
boat. The figures show that the lakes represented, with the notable
exception of Schoodic, have bottoms that are generally flat ; and noting
the nature of the materials that compose the shores, the lake beds would
seem to be hollows, which had their origin in irregular accumulations of
drift deposited on broad, flattish surfaces.

* Second Report on Geology of Public Lands, 1838, p. 11.

t G. W. Taylor, Esq., a resident of Cazenovia, Madison County, N. Y., writes as
follows respecting Cazenovia Lake, which is one of the feeders of the Erie Canal, and
situated in a valley surrounded by hills : —“ Mr. Ledyard, one of the old inhabitants,
made many soundings before I came here to reside. The bed of the lake [four miles
long by three fourths of a mile wide] is as level as « valley ; about one third of its
area varies in depth only from 43 to 46 feet, — the latter being the greatest depth.
The south end [the foot] of the lake is quite shallow.”

MUSEUM OF COMPARATIVE ZOOLOGY.

I. Upper Joe Merry Lake.

Off east shore, from middle of that
shore to south end of lake

South of South Island .

CaONauh OW —

ly
West of South Island... . Sy:
19

20%.
North of South Island. . . . 21
22.

East of South Island .

Up centre of lake from south end { 27

II. Middle Joe Merry Lake.

Running along central part from lagoon on south to vicinity of outlet at

B.

A.

Ft. In.
ql 10
2 10
3 < : ‘ 15
4 : : - 15
5 : A - 14 8
6 14 if
7 15 3
8 15
93 F < : - 11
10 : F = 2 15
i | boner : : ; 14>» 4
12 : : : : 13
WS *: : a F 16 4
14 < ‘ “ - 18
Lop 3 . 5 : 18 2
16 - ‘ - a 17
iy ee : ; : 5 16
18 - 17

VOL. VII.—wNO. 5. 13

COmIHS oP COD

Ft.
28

36

43
44

193

In.

4
8

194 BULLETIN OF THE

Ill. Lower Joe Merry Lake.

From entrance on south, along middle 1} miles to northwest, till stopped from
sounding by wind.

Az B.

Ft. In. Ft. In.
1 20 4 1 15 4
2 2D 2 16 5
3 PWR ts 3 20 4
4 10 6 4 22 4
5 25 5 20
6 20 ay. 6° 20
7 30 7 21
8 30 7 8 23 10
9 33] 9 24 2

10 33

IV. Pemadumcook Lake.

Running southeast toward foot, west of middle. Soundings began off small island
near mouth of Lower Joe Merry outlet, and continued 23 miles down, till stopped by
wind.

A. B.

Ft. In. Ft. In,
1 13 1 13
?) 15 8 2 23
3 23 5 3 36 «6
4 37 4 30
5 : 29 4 5 - 28's 2
6 28 7 6 5 3 24 9
7 : 15 20 7 : . F 23
8 24 4 8 5 A 17
9 20 10
10 17
11 17 3
12 14 7

From foot, east of middle, in northwest course, about four miles, nearly to Gull Rock
on east shore, opposite mouth of Lower Joe Merry outlet.

A. B.
Kt. In.
Oy 4)
13
12
Wt
15
17 Hes aint
21 ler. 5 4 3 - « 2 f4
21
s c c ; 19
10 6 2 7 m5 16
11 c : 5 A . 23
12 2 , : ; 23
18 ; 3 ; : Fi 23

CaonNtaurbhoatwv=
ora =F

CAN kam

MUSEUM OF COMPARATIVE ZOOLOGY. 195

V. Ambejijis Lake.

Along middle, from foot, north to head, about two miles.

A. B.

Ft. In. Ft. In
1 9 3 i 7
2 10 4 2 18
3 LOD 3 35 4
4 1 a 4 44 6
5 14 5 35 3
6 16 9 6 37 «6
7 25 4 7 25 4
8 2659
SD es : “ 7 . 380
10 : : - ‘ Sl 6
LS : > , : 26 4
12 : ; é - 25) 7d

Cast 12 was quite distant from 11, and near entrance of Penobscot into lake.

VI. Schoodic Lake.

Numbers 1 to 25 give soundings from south end north, along course of west shore,
but well out from it ; 26 to 38 were taken off east shore, going from south to north ;
39 to 50 are soundings made in March, 1881, through holes cut in ice along centre of
lake, from south to north, at intervals of halfa mile. Taken by Mr. Isaac Clapp, who
speaks of his soundings as showing that “there is a mound near the centre of the lake
105 feet high,” above the adjacent deepest parts.

Ft. Ft.

1 37 26 . : P ; : 120

2 65 oT &: : : P } = 220

3 100 28 : ; F : : 97

4 100 Dom. : : : A S100

5 87 30 : : : : - 104

6 86 Slaae : : : : a 06

7 63 32 : : é ; : 100

8 25 BR ee. ¢ : 5 : S70

9 28 34 2 : ‘ 3 3 63

10 16 35 Off Five Islands . 100
ll 12 36 : : é : ¢ 95
12 17 ove we : : : : . 95
13 56 38 ’ : ; 4 : 28
14 , : evn ate 39 . Z : : Se110
15 A 2 ; 70 40 : : : : ; 140
16 : . TS hie E P : ¢ . 140
17 : ‘5 : 90 42 E : Z : : 142
18 90 43") F . : : eee:
19 100 44 ; J , : : 40
20 51 45. : : : ; > 145
21 37 46 : ; 4 f : 100
22 39 ieee - : : : 90
23 28 48 : : ; j : 120
24 28 49. 5 : ; ; Sep

25 Atnorthend . . (14 eet ee 90

196 BULLETIN OF THE

VIL North Twin Lake.

Soundings taken by Mr. Wilson, along middle, from north to south, about two miles.
Mine were lost.
Ett) in:
19
18
16
22
23
22
19
19

MIS OP 63 to
rt a i)

An Unreported Kame.

From a spot on the western shore of Middle Joe Merry Lake, known
to the guide as Gordon’s Landing, a name derived from former lum-
bering operations, a “ horseback,” or kame, runs two and a half miles
north 28° west, forming for some distance the shore of the lake. On
examination it proved to be an interesting specimen of its kind. It
slopes at each end gradually to the general level, but through all the
central portion maintains a tolerably uniform height. At a fairly rep-
resentative point, it was found to have at its slightly rounded top a
width of 15 feet, and by use of a clinometer and level the inclination of
the east side was ascertained to be 30°, and the height 39 feet above
the lake. The west side has an angle of 25° and rises 26 feet above an
old pond of equal length with the kame, now changed to a swamp, only
the width of the kame intervening between the swamp and the lake.
Many granite bowlders of from one to two feet or more in diameter are
strewn upon the ridge at and near its summit. The smooth and un-
broken surface of the kame seems to indicate rather that they were
deposited upon the ridge subsequently to its formation, than that, having
made part of the original structure, they were by denudation left pro-
jecting from its surface.

The Granite Area.

Doubts respecting the actual existence of the granite area represented
in the geological map were suggested during a rapid passage, in 1869,
over the route now taken. The facts already stated, so far as they bear
on the theory of such an area, do not go to sustain it. The observations
now to be noted are more closely related to it.

From Gordon’s Landing an excursion was made to Joe Merry Moun-

MUSEUM OF COMPARATIVE ZOOLOGY. 197

tain, which is situated well within the limits of the supposed granite
district, and is nearest and highest of the elevations that lie west from
the chain of lakes. Showing upon its sides, as it does, bare cliffs through
the forest that covers it, this mountain was chosen as a locality where
we might hope to find some evidence of the nature of the rock underly-
ing the vicinity, which, at the lower levels, had been hitherto concealed
by thick drift deposits.

Dr. Jackson, while on his way to Ktaadn in 1837, saw this mountain
from the shore of Ambejijis Lake, and describes it in these words:
“ From this spot I took a view of Joe Merry Mountain, which appears
rising to a considerable elevation on the southwest. ... . It is composed
of granite, and is a commanding point of view for examining the sur-
rounding country, so that it is frequented by explorers for timber.” *
But as Jackson was never nearer to it than when he ran down Pema-
dumcook Lake on the return from Ktaadn, it is evident that this
statement rests merely on report.

A circuit of seven miles through the woods brought us to the foot of
the mountain on its north side, where it rises at a sharp angle from
the valley. For the last four miles of our way up to this point, the
ground was thickly strewn with granite bowlders, which became larger
and more numerous as we approached the mountain. So far neither
rock in place, nor bowlders of other material than granite, had any-
where been seen. But, 200 feet up from the foot of the steep north-
ern face, we began to find mingled with the granite bowlders others
of considerably altered mica schist. At the height of 450 feet, and
again at 600 feet, above the base, we came upon exposed ledges of rock,
the same in kind as the newly found bowlders. So far the ascent
had been abrupt. For the next hour it was more gradual, and
several small levels and depressions were traversed. Later, a narrow
and deep ravine was crossed, having on its farther side a cliff of schist,
similar to that observed below, which rose at an angle of 35°, and so
high as to require twenty minutes’ sharp climbing to gain its top.
Thence a gentle ascent was followed for ten minutes, when an elevation
was attained of 1,635 feet above the lake, as determined by means of an
aneroid, whose readings at various points were compared with simultane-
ous observations made by Mr. Blake with a Green’s mountain barometer
stationed in camp at Gordon’s Landing. At this height numerous gran-
ite bowlders were still scattered over the mountain top. The mountain
is a long ridge, running north and south. Its actual summit now lay

* Second Report ‘on Geology of Public Lands, p. 13.

198 BULLETIN OF THE

perhaps half a mile before us, but scarcely more than 150 feet higher
than the point already reached. As it was covered with forest, and
promised neither outlook nor further revelation of the lithology of the
mountain, and as our time was exhausted, we advanced no farther, but
returned to the lake.

From the head of Ambejijis Lake, the route to Ktaadn for the next
nine miles follows the Penobscot. For this distance, and in fact all the
way from Shad Pond, below, to Chesuncook Lake, the river at short
intervals widens into still lakes connected by rapid, rocky, and narrow
reaches of running stream. As related to the falls and rapids, each of
the numerous lake-like expansions is styled by rivermen a “ dead-water.”
These remaining nine miles of water route include five falls, requiring as
many portages of from twenty to ninety rods in length, each fall having
below a dead-water bearing the same name as the fall itself. Thus
Ambejijis Lake is the dead-water that lies below Ambejijis Falls.

While the prevailing and excessive drought greatly retarded travel
upon the river, it afforded an unequalled opportunity to learn the nature
of its bed, now bare to an extent unknown before for many years. One’s
conclusions with regard to the geology of the district south of Ktaadn
must be shaped largely by the view he takes of the facts that relate to
the nine miles of river bed here referred to. And since the previously
recorded examinations of this part of the river were made in haste, and
at times when high water in great measure hid the channel from obser-
vation, it seems best to state the very simple facts somewhat in detail.

Ambejijis and Passamagamet Falls, first in order, and a mile and a
half apart, are caused by accumulations of large granite bowlders that
choke up the narrow channel and give origin to the dead-waters next
above them. ‘To remove the bowlders would be to draw off the waters
of those pond-like expansions. Not a trace of rock in place could be dis-
covered in the river bed at either of these falls, nor upon the adjacent
shores, which are elevated but a few feet above the level of the river.

The first ledge that appears upon the river or its expansions, from the
foot of North Twin Lake northward, occurs twenty rods below the third,
or Katepskonegan Falls, longest of the series, stretching seventy rods
along the course of the river. The ledge, which is of granite, rises on
the eastern shore directly from the water in a precipitous head of twenty
feet in height. | Northward to the falls, the east shore is a steep exten-
sion of the head, which inclines downward to the north, till at the falls
themselves the ledge is to be seen only on the floor of the river bed.
There is no exposure of granite upon the western side to match the high

MUSEUM OF COMPARATIVE ZOOLOGY. 199

head upon the eastern ; neither could rock in place be detected in the
low banks of drift abreast the falls, nor along the carry. In the chan-
nel at the foot of the falls, the ledge was mestly hidden by accumulated
granite bowlders, while at the upper part the water was seen to pitch
over successive shelves of granite in place.

Though it was here that we first came upon fixed rock in the river
bottom or banks, we had seen, half-way between this and the next fall
below and some distance back from the west shore, two high forest-coy-
ered hills, which were the first considerable elevations met with since
we left the lakes below. On the southern slope of each hill is a naked
cliff. Circumstances rendered it impossible to land and push through
the woods for a visit to the cliffs ; and no second view of them occurred,
since my return from the region took place by another route.

The passage through the dead-water of more than two miles to the
fourth fall showed no trace of rock in place, either in the channel or along
the shores. Nor did the neighboring low hills exhibit any faces of
exposed rock.

Pockwockamus Falls, the fourth, occupy about twenty rods of the riv-
er’s length, beginning abruptly from still water above, and ending as
abruptly below in water of like character. The bed is an uneven floor
of granite ledge, measurably free from bowlders in the middle third,
but on each side covered with large blocks, mainly riven from the under-
lying fixed rock, which does not differ materially from that of the third
fall.

At the fifth or Aboljacarmegus Falls, a mile above the fourth, is the
next exposure of rock iz situ. The river makes here a sudden bend,
flowing from northeast to southwest, and is exceedingly narrow. The
length of the fall is ten or twelve rods only, and the underlying granite
differs strikingly from that of the third and fourth falls, and from that
which makes up Ktaadn. In places it is highly porphyritic, and occa-
sional patches of several square feet consist of massive feldspar or quartz,
not constituting veins. At the third and fourth falls the granite, being
highly jointed, has become divided into rhombohedral blocks of all sizes.
Worn at the angles in various degrees by attrition, these make a large
proportion of the bowlders that at both those falls conceal the rock in
place over much of its area. At the fifth fall the fragments split from the
solid mass in somewhat lenticular forms, never in rhombohedral blocks.
About the foot, the only pot-holes anywhere seen occur in considerable
number, but not of great size. Their presence here and absence from
the falls below must be explained by difference in the texture of the

200 BULLETIN OF THE

rock at the localities, rather than by difference of other conditions.
Along the portage past this fall are several small exposures of granite
ledge, the only ones that were seen near the river, apart from its bed or
banks.

The granite of the three ledge-formed falls, as well as that of Ktaadn,
beyond any other that I have elsewhere seen, is free from veins and
dikes. In fact the only instances observed of either in the whole
region were a quartzose vein, an inch wide, that ran through a block
twenty feet in length, evidently torn from the rock on which it rested at
the fourth fall; and a small trap dike, four inches wide, that traversed
a nearly buried erratic bowlder lying on the portage at the fifth fall.

Another circumstance common to the granite of the several localities
is, that at the falls only is it visible. Above and below each fall the rock
so suddenly and entirely disappears, that over the spaces between the
falls granite in place could nowhere be discovered. It would seem, then,
that at the third, fourth, and fifth falls a ridge of granite in each case
cuts the river bottom transversely, damming the stream and obliging it in
its course seaward to tumble in a fall over the lower slope of the ridge.
The underlying fixed rock which intervenes between the granite ridges
is so hidden by drift deposits that nothing can be asserted positively
concerning its nature. One would naturally suppose it to be granite ;
but without attaching much importance to the marked difference between
the rock of the upper fall and that of the two next below, there are other
considerations, to be noticed presently, which suggest a doubt whether
the three ridges that occasion the three ledge-formed falls have any lat-
eral connection below the drift, and the question whether they may not
be distinct ridges of intrusive rock, thrust up through strata from a com-
mon source beneath.

The theory that the district south of Ktaadn is part of a continuous
granite region, is a hasty generalization from insufficient data, origi-
nally made by Dr. Jackson. Prof. Hitchcock, in his survey, which was
discontinued at the close of its second year, made no personal examina-
tion of the Penobscot valley between Chesuncook Lake and Grand
Falls. He therefore naturally adopted in the construction of his geo-
logical map Dr. Jackson’s view of that district, supplemented by some tes-
timony of one of his own assistants. The map was of course intended to
be provisional only, and, had the survey been continued, would probably
have been superseded by others. All the basis that exists for belief ina
wide granite area south of Ktaadn is found in a few passages of Jack-
son’s and Hitchcock’s Reports. They can here be presented in small
compass.

MUSEUM OF COMPARATIVE ZOOLOGY. 201

Jackson’s notes of his trip to Ktaadn contain only the following brief
statements respecting the rocks im situ which he saw on the way to and
from the mountain. First, the one previously quoted in full, that Joe
Merry Mountain “is composed of granite.” * Second, that, “leaving our
boats, we walked to Pock-wock-amus Falls, where the river rushes over a
ledge of granite.’ ft Third, “ All the rocks at Quakish Lake} are
granite, and the water falls over huge bowlders of that rock.’ §

Dr. Jackson's assistant, Mr. J. T. Hodge, had preceded him by three
months in the passage up the river. He speaks of but one of the two
hills I have described as lying west of Katepskonegan Dead-water,
saying: ‘‘On its western side is a high hill of granite, covered with
immense loose blocks of the same rock, piled one upon the other almost
perpendicularly.” He adds: “Two miles above [a fall over “ lvose
granite rocks” ], we were obliged to carry by again on the western side.
The opposite bank is formed of granite . . . . lying in the best position
and form for working.” Continuing, he remarks: ‘ Not far above
this we arrived at a fifth portage, which is called the Pauquakamus [in
fact Aboljacarmegus]..... At the head of this portage, the bank is a
smooth ledge of granite.” ||

Mr. J. C. Houghton, who for the year 1861 was Hitchcock’s assistant,
furnished for his report the following facts. In the account of a trip
from Moosehead Lake down the Penobscot to Ktaadn and beyond, he
notes that at the fourth and fifth portages “ the river falls over ledges
of fine granite.” {1 Respecting the fixed rocks upon the river and lakes
below, he makes no further remark than that “near the outlet of North
Twin Lake is the southeast limit of the granite, and the quartz rock
[which he had last seen between Chesuncook and Ripogenus Lakes]
again appears.” **

Elsewhere Mr. Houghton mingles facts and conjectures. Having vis-
ited the *‘ Katahdin Iron Works,” ++ which are situated in the township
that corners upon Brownsville at the northwest, he proceeded twelve

* Second Report on Geology of Public Lands, p. 11.

Tt Ibid., p. 14.

¢ Quakish Lake on Hitchcock’s map is placed outside of the manite district, the
last granite in place being now known to occur a little below North Twin Lake, above
Quakish.

§ Ibid., p. 20. | Ibid., p. 53.
J Prel. Rep. Nat. Hist. and Geol. of Maine, p. 440.
** Thid., p. 440.

tt A confusing misnomer, since they are situated full thirty miles in a straight line
from the mountain whose name they bear.

202 BULLETIN OF THE

miles farther northwest to a remarkable gorge, known as the “ Gulf.”
This has been cut by Pleasant River for five miles through black slate
that rises on either side in walls, sometimes to the height of from 100
to 300 feet, often vertical or overhanging.

He next “ascended Saddle Rock, a mountain which is about eight
miles north 36° east from the Iren Works.” * Its height he gives as
3,010 feet, being 2,416 feet above the ground in front of the furnace
of the Iron Works.” + He says again: “I was disappointed when I got
to the summit to find it composed of the same slate formation that I
had been on so long.” After a few lines more he adds: “ To the north-
west are several mountains, the highest of which is called ‘White Cap,’
on account of its naked white summit, which, as a hunter informed me,
is composed of granite. It is about eight or ten miles from Saddle
Rock, and is probably near the southwest limit of the Katahdin granite
region.” ¢

This report of a “hunter,” and Dr. Jackson’s false statement, grounded
on hearsay, that Joe Merry Mountain is made up of granite, constituted
Mr. Houghton’s only warrant for considering the granite district to
extend beyond the Pemadumecook chain of lakes, and so far south as the
northern line of the township next north of Brownsville, as is repre-
sented upon the geological map. Furthermore, the fact that, in the
whole forty miles of the route between Ktaadn and the imaginary south-
ern line of the district, granite has been found coming to the surface,
over exceedingly narrow areas, in five localities, — viz. at the third, fourth,
and fifth falls, near the outlet of North Twin Lake, and at the Upper
Joe Merry Lake, — furnishes a very slender basis for belief in the exist-
ence of a continuous granite area south of Ktaadn.

Suppose we concede to be made up of granite the cliffs seen by Mr.
Hodge and myselt on the hill, or hills, west of Katepskonegan Dead-water,
and apparently identified by him as granite through a distant view
gained as he passed up the river in his boat ; and White Cap, reported
to consist of granite by one whom we do not know to have learned its
character from personal examination. With these additions we have
data still entirely insufficient to justify the conclusion that has been
drawn from them.

The sudden appearance, and as sudden disappearance, of granite in
districts covered by stratified rocks, are characteristic of Central Maine.
The granite not uncommonly occurs as isolated hills separated by a

* Prel. Rep. Nat. Hist. and Geol. of Maine, p. 430.
t Ibid., p. 430. ¢ Ibid., p. 431.

MUSEUM OF COMPARATIVE ZOOLOGY. 203

greater or less extent — sometimes by a score of miles —of unbroken
strata. The same reasoning that would make the district south of
Ktaadn a continuous granite area, would apply as well to others known
to be underlaid by strata through which granite shows itself in detached
hills or ridges.

The case of Augusta, situated near, but not at, the southern border of
the region of slates and schists, is instructive in this connection. The
conclusion which even a geologist looking over that vicinity in haste might
feel to be the natural inference from obvious and abundant data, would
nevertheless be a wholly false one. An outline of the case only can here
be given. Augusta city is built on both sides of Kennebec River, upon
well-developed terraces which form the sides of a valley that has there
been excavated to the depth of 300 feet below the level of the adjacent
country. The width of the valley east and west, from summit to sum-
mit, is a little over one mile in a straight line, and midway runs the
river in a course somewhat west of south. The terraces and summits
on either side are composed of drift deposits, so thick that the deepest
wells nowhere reach solid rock; and four sharp ravines, that on the
western side cut the terraces down to the level of the river at their
mouths, have bottoms and sides of drift, as has the river bed, except at
two points. The highest part of the western summit is a “ granite”
ledge which rises in a knob some thirty feet above the rest of the sum-
mit and the general level of the country. Its top has an area of not
more than one or two acres, and falls off rapidly on the north, east, and
southeast beneath the enveloping drift. A mile south of this point, and
half a mile southwest from the State House, is a broad hill, about 400
feet in height above the river. On its southwest side, which lies in
Hallowell, are the quarries that furnish the well-known “ Hallowell
granite.” The hill throughout is a solid mass of the same material.
In riding out of town two miles to the west, northwest, or northeast, one
comes upon several “granite” quarries in each direction. In view of
the foregoing facts, a visitor would feel himself justified, if no further
examination were made, to pronounce “granite” to be the underlying
rock of the vicinity. But should he notice just across the railway track
from the station, at the foot of the second terrace, forty feet above the
river and 200 feet from it, an exposure of rock now mostly hidden by
a granite bank-wall, he would find it to consist of hardened, upturned
schist ; and in the drought of summer he would see in the river bed,
for a few rods above and below the railway bridge, ledges of the same
schist.

204 BULLETIN OF THE

Across the deep, narrow valley of a tributary to the Kennebec, above
half a mile in an air-line northeast from the granite knob before men-
tioned, and at the northern limit of the city proper, rises more than 300
feet above the river what was formerly known as the Andros Hill, the
upper part of the so-called Cushnoc Heights. On the southeastern slope
of its upper hundred feet, on nearly-the same level with the road, but on
the opposite side of that part of the hill, and so hidden from the view
of the passer-by, is an abandoned quarry of mica schist. Here, too, the
rock plunges off on the south, east, and west beneath an unknown depth
of drift.*

Finally, should the observer examine, for the four miles that intervene
between Andros Hill and the northern line of the township of Augusta,
the very few exposures of rock in place that occur along the river road
on the west side of the Kennebec, and upon the farms crossed by the
road, he would find in every case schist, and that only. Upon the cor-
responding road east of the river, only schist is found for the whole six
miles of itslength across the township. It is evident, then, that the
underlying rock of Augusta is the upturned schist, which becomes at
Waterville, eighteen miles north of Augusta, the almost vertically placed
Taconic or Lower Silurian slate that stretches to Moosehead Lake on
the north, and easterly to and beyond the city of St. John, N. B.

In the great denudation which this extensive region has undergone,
the more resisting granitest of Kennebec County have been left project-
ing as hills above the softer schists, which, worn down to lower levels,
have been covered with deposits of drift, frequently of great thickness.
For miles these lower grounds and the hills also may be traversed with-
out meeting any indication of the nature of the underlying rock. Thus,
upon the road along the western side of the Kennebec, between Andros

* Half a mile above the bridge, at the foot of Cushnoe Heights, is the Kennebec
Dam. In 1839 a freshet swept away seven acres of iand at the west end of the dam,
and cut a new channel for the river 500 feet in width, the floor of which, when the
waters abated, was found to be a transverse ridge of well-marked mica schist. In
extending the dam across the new channel, the rock thus laid bare was soon after
hidden again from view.

+ The so-called granite of Hallowell and Augusta was termed by Jackson “ granite
gneiss” (First Rep. Geol. of Maine, p. 83), and is declared by Dr. T. Sterry Hunt to
be ‘true gneiss” (Am. Jour. Sci., [3.] I. p. 85). But is the sudden transition, in so
many places within a small area, from crystalline rock to distinct schists, compatible
with the idea that the former is a metamorphosed portion of the latter? Are not the
relations of the two more consistent with the hypothesis that the ‘gneiss ” is in real-
ity eruptive granite, which in its passage through the strata has changed the original

slates into hardened schists ?

MUSEUM OF COMPARATIVE ZOOLOGY. 205

Hill in Augusta and Waterville, I remember but five small spots where
rock zz situ rises to the surface. Upon the adjoining farms a few others
may be observed. All are little patches of outcropping strata. Going
northward from Augusta, wherever the strata are harder than usual
they rise into hills. At Waterville, while fissile slates occupy the low
grounds, they lose the slaty structure and pass into hard schists in sev-
eral high hills, one of which presents a bold, precipitous face. The
numerical proportion of such hills increases farther north, till, south and
east of Moosehead Lake, so far as examination has been made, hills and
mountains of schist far outnumber those composed of granite. Isolated
granite hills occasionally rise in districts of slates and schists, but
nowhere is anything to be found that can be termed a granite district.
Judging from the foregoing facts and instances, we must think, until
stronger proof to the contrary is produced than at present appears, that
the country south of Ktaadn, to and beyond the Joe Merry Lakes, is
part of the great region of stratified rocks which surrounds it on all sides.
On such an hypothesis, the presence of Joe Merry Mountain where it is —
a mass of schist — is comprehensible ; but how shall it be accounted for
if supposed to rise out of a granite district ?

On arriving at the mouth of the stream where the trail from the river
to the summit of Ktaadn begins, it had been my purpose, before making
the ascent of the mountain, to run up the Penobscot twelve miles far-
ther, to Ripogenus Portage, upon which occurs the border line between
the granite and the stratified rocks in that direction. But lack of water
in the river, and its obstruction by great gatherings of logs, formidable
enough below and known to be worse above, made further boating
impracticable. The Ripogenus trip was therefore unwillingly relin-
quished.

Of the northwestern portion of the so-called granite district, I can
speak, then, only from notes and recollections of a canoe excursion made
in 1871 from Moosehead Lake downward. They enable me to say, how-
ever, that the river’s course, from the Ripogenus Gorge to Sourdnahunk
Falls, lies chiefly among hills. Those on the north skirt closely the
left bank of the river, and are foot-hills of the Sourdnahunk Mountains,
which are a little beyond. The hills are frequently precipitous, present-
ing a frontage of granite cliffs. Except at the Ambajemackomus Falls,
where the river plunges eight or ten feet over a shelf of granite, I have
no distinct remembrance of ledges in the channel, which is thickly
strewn with granite bowlders. But the character of the heights adja-
cent upon the left leaves no room for doubt that, between the limits

206 BULLETIN OF THE

specified, the Penobscot flows over underlying granite, superficial or
drift-covered.

Mount Ktaadn, as we shall see, is composed wholly of granite, and its
relation to the Sourdnahunk Mountains, which extend from Ktaadn
westerly ten miles, is such that it and they must be regarded as parts of
one continuous range. It cannot be doubted, therefore, that a Ktaadn
“oranite area” exists, having for its length that of this range, and
including on its southern side the channel of the Penobscot, at least so
far down as Sourdnahunk Falls, which are three miles above the mouth
of Aboljacarmegus Stream. These statements are confirmed by the few
observations upon this part of the river which the Geological Reports
record,

The floor of the Great Basin of Ktaadn has an elevation of 2,900 feet
above the sea. As one goes outward from it by the present route to the
East Branch of the Penobscot, better styled the Mattagamon River, he
skirts along the northern foot of the abrupt portion of the eastern moun-
tain. On leaving that, he quits the last trace of rock im situ, which
nowhere reappears in the descent of more than 2,400 feet made along the
twenty-three miles of way to the crossing of the Mattagamon at the
Hunt Place. There is abundant testimony that ledges do not come to
the surface on the old Keep Path, which diverges from the present route
at Ktaadn Lake and runs seven miles to the foot of the East Slide.
It is certain, then, that on the east side of Ktaadn granite has not
been discovered upon the gradual lower slopes of the mountain, which
make up nearly half of its whole height. It is certain, too, that just
beyond the western or Sourdnahunk end of the range, the granite dis-
appears beneath the surface. To the south of the Sourdnahunk Moun-
tains, as we have seen, granite without doubt makes up the river channel ;
but the aspect of the low country to the south warrants the supposition
that granite as a superficial rock extends in that direction not far beyond
the Penobscot. It seems, therefore, in the highest degree probable, that
the Ktaadn “granite area” includes little but the mountains them-
selves, and that, nowhere extending far out from the foot of the range, it
does not, in some parts, embrace even the lowest slopes. ;

Mount Ktaadn.

The low country south of Ktaadn has an average elevation of not
more than 550 feet above the sea. From it rises the mountain by mod-
erate gradations to less than half its altitude, or about 2,200 feet on

MUSEUM OF COMPARATIVE ZOOLOGY. 207

the south side, but the upper portion, rearing itself 3,000 feet higher, is
bounded by declivities of great abruptness.

A brief description, illustrated by the accompanying heliotype of a
model which represents the upper three thousand feet of the mountain,
will render intelligible subsequent references to the general features of
Ktaadn.

The crest that bears the highest peaks is bent like a deep crescent,
opening north, and enclosing the Great Basin. At the centre of the
crescent are the two chief peaks, which differ in altitude less than
twenty feet, and are not more than a third of a mile apart. Directly
beneath the East Peak, shoots off to the southeast the longest of all the
spurs, which, narrow above, widens greatly towards its foot. Beyond
‘the peaks, the eastern horn of the crescent includes a thin, serrated
crest, and forms at its tip, first, the little tower-like peak known as
the Chimney, and then, across a narrow, square-cut notch, the peak of
Pamola,* named from the Indians’ demon of the mountain. It is known
to many only as First Peak, so styled because it was the first summit
reached by tourists who followed the original eastern route to the
mountain. Pamola has a regularly convex, wide northern face, that
runs down with a precipitous foot to the level of the basin floor, nearly
2,300 feet below the highest peak. Eastward from Pamola projects a
narrow, sharp-ridged spur, the ‘‘ Horseback,” —an unfortunate name as
here applied, since in other cases it invariably means, in Maine, a kame,
with which this buttress of solid rock has nothing in common. Towards
its extremity, the ‘ Horseback” forks, and sends off to the northeast a
lower, flat-backed spur, while on its southern flank is the East Slide,
the smaller of the two great slides that are among the peculiar features
of Ktaadn.

Against the western horn of the crescent abuts the Table Land, an
almost absolutely plane surface, inclined to the northwest at an angle
of from five to seven degrees, and having a length of a mile and a
half, and an area of more than five hundred acres. The centre of this
plateau is a few hundred feet lower than the highest peak, which has an
elevation of 5,215 feet, as determined by Prof. Fernald. Half a mile
below the middle point of the sharp brow that bounds the Table
Land on the south is the head of the Southwest Slide. This slide is

* The name as given by Jackson and those who have followed him is Pomola.
I have chosen the form Pamola on the authority of Rev. Eugene Vetromile (‘‘ The
Abnakis and their History,” pp. 63-67), for many years Catholic missionary among
the Indians of Maine and New Brunswick. Dr. De Laski, in a paper to be referred
to farther on, applies the name incorrectly to the ‘‘ apex of Katahdin.”

208 BULLETIN OF THE

the track of an enormous avalanche, which, in 1816,* swept over a course
of not less than four miles in length. A mile or more of the lower part
is now wholly grown up to forest, but the upper part, for a mile and
three fourths, is still covered with loose fragments of rock and gravel,
upon which vegetation has not encroached, except along the sides. The
East Slide is less than.a mile long.

The Table Land narrows on the west, and sends off a sharp-ridged
spur that curves to the southwest. From West Peak there is a descent
northward and westward, into which the Table Land merges, down
to the level of 4,250 feet,—the lowest part of the central mountain,
termed the Saddle. Northward from this rises rather gradually a
rounded summit 450 feet higher than the Saddle, or 4,700 feet above
the sea, and 515 feet lower than West Peak. Three fourths of a mile
farther northeast is a second summit, similar to the first, but slightly
lower, the two being separated by a moderate depression of the ridge.
A half-mile farther, in the same direction, follows a third rounded sum-
mit, perhaps seventy-five feet lower than the first. From the first and
second northern summits run eastward two sharp and narrow spurs,
which include the North Basin, so named to distinguish it from the Great
or South Basin. The northern face of this smaller basin is made up of
cliffs for the most part nearly vertical. From the second summit runs
west another long and flat-topped spur.*

Beyond the Saddle, the mountain stretches some seven miles to the
northeast, and terminates in a knot of lower spurs, having in the main
flattish tops and precipitous sides.

The Great Basin, in its whole extent, forms an amphitheatre, which,
seen from above, strongly resembles an old voleanic crater. In the ab-
sence of trigonometrical measurements, its dimensions cannot be accu-
rately stated ; but they may be approximately given as from summit to
summit east and west two and a half miles, by a mile and a half from
north to south. Its most precipitous part, the southern lobe, measures
from its head to the Basin Pond about three fourths of a mile, and its
width is nearly the same. The smaller North Basin approaches in
shape the capital letter U, and is about a mile and a half long and half
as wide, fronting a little south of east. The larger basin has a narrow
gateway opening to the northeast.

* Williamson’s History of Maine, Vol. I. p. 90.

+ In photographing the model, light fell upon the western spurs exactly in the
direction of their length. Flooded thus with light, these parts have not enough of
shade to render them distinct.

, MUSEUM OF COMPARATIVE ZOOLOGY. 209

The wall of the Great Basin rises highest above its floor on the south,
becoming gradually lower on the east and west sides. The height of
West Peak above the Basin Pond, as determined by the mean of six
pairs of simultaneous observations taken with a Green’s mountain ba-
rometer at the level of the pond, and with an aneroid upon the peak,
was found to be 2,287 feet, which is the depth of the basin, measured
downward from the top of the same peak. Its walls on the south and
east are so steep that they have never been climbed, except at one or
two points, as an act of foolhardy daring. The height of Pamola above
the little pond, as estimated from a single pair of simultaneous observa-
tions, is 1,891 feet, or 396 feet less than that of the highest peak.

It is within the walls of the Great Basin, and upon their summits,
that the geology of Ktaadn can best be studied. The whole mountain,
from the lowest point where rock in place has been discovered, is com-
posed of granite. Of this, five specimens, numbered 3, 5, 23, 25, and
57, have been examined by the lithologist of the Museum, Dr. Wads-
worth, whose notes upon them are here given. In a general description
of the mountain, it may be said that it is made up of two varieties of
granite, the gray and the red. ‘To the first variety specimen 3 be-
longs ; to the last, belong 23, 25, and 57; 5 being in a manner in-
termediate between 3,on the one hand, and 23, 25, and 57, on the
other.

Dr. Wadsworth’s Notes.

No. 3.— A gray granite, composed of feldspar, quartz, and biotite. The
feldspar is of two kinds: a grayish-white one, with a pinkish tinge, is the most
abundant, while subordinate to it occurs a milk-white striated feldspar. The
powder of the rock is magnetic. Under the microscope the thin section is seen
to be composed of orthoclase and plagioclase, quartz, biotite, and magnetite.
The orthoclase is much decomposed and cloudy, showing only feeble polariza-
tion. The plagioclase, in general, is much less altered, and shows its triclinic
character well in polarized light. Some of the crystals, however, show the
characteristic banding only in places, principally at the ends and sides of the
crystals, while in the more altered portions the twinned structure is rarely seen.
This alteration renders it very uncertain that the supposed orthoclase is really
all so; and we feel that this has been a fruitful source of error in the micro-
scopic examination of rocks. The quartz contains numerous fluid inclusions,
moving bubbles being seen in them; it also contains trichites and minute
crystals. These crystals are probably apatite and zircon. Some apatite crys-
tals were seen in the feldspar.

No. 5. — A pinkish gray granite of the same composition as No. 3, the dif-
ference in color being due to the deeper color of the feldspar. It shows in the

VOL. VII. — NO. 5. 14

210 BULLETIN OF THE E

thin sectior. similar characters to No. 3, except that the feldspars are more de-
composed, and therefore less plagioclase could be seen, while the quartz con-
tains more abundant trichites.

No. 23. —A brownish red granite of similar composition with the preceding.
Feldspars colored pink and greenish white. Calcite and a greenish talcose
mineral occur as alteration products. In the thin section the feldspar is seen
to be greatly altered, and but very little of it shows any trace of triclinic
characters. The biotite is partly decomposed, and has a greenish color. The
general character of the rock is slightly more basic than the two preceding,
but we do not consider that there is enough difference to lead us to regard
them as distinct. We should rather regard them as parts of the same forma-
tion.

No. 25. —In this specimen the greenish feldspar predominates over the
pink. The rock shows abundant signs of weathering, containing numerous
cavities formed by the decomposition of its ferruginous minerals, and now
partially filled with hydrous oxide of iron. Under the microscope this is seen
to be the most decomposed of any of the specimens, the biotite being almost
wholly changed, and almost no plagioclase being recognizable. Many parts of
the rock are filled with viridite. The quartz, besides its numerous fluid inclu-
sions, contains dodecahedral quartz crystals of the same character as those so
commonly seen in the quartz of rhyolite. This rock is similar to No. 23. We
should regard these rocks as eruptive, but we are well aware that others would
claim that the microscopic characters are those which belong to metamorphosed
sedimentary rocks.

No. 57. — This rock is seen in the hand specimen to be composed of flesh-
red orthoclase, pale greenish white feldspar, somewhat decomposed, together
with altered biotite and quartz. The biotite has been changed to a chloritic
material. The minerals give to the rock a greenish red color, It is more
coarsely crystalline than the other specimens from Mt. Ktaadn, and in its
general facies is somewhat unlike specimens 3, 5, and 25.

The lower two thirds of the basin walls are composed of the gray
granite, which is similar in composition and appearance to that of the
lower slopes of the mountain on the south side, and to that of Katep-
skonegan Falls, except that the rock of the localities last indicated con-
tains only the white feldspar. The upper third of the walls consists
chiefly of the red variety (5), the modifications represented by Nos. 23,
25, and 57 being found only upon the very highest parts of the moun-
tain, — the East and West peaks, the serrated crest, and the ridges that
connect those portions. The rock represented by the last three num-
bers is throughout so badly decomposed that only once was a specimen
(57) obtained tolerably sound and firm under the hammer. The rock
represented by No. 5 is oftenest, but not always, found in a crumbling

MUSEUM OF COMPARATIVE ZOOLOGY. 211

condition ; while the gray variety (3) is generally comparatively solid,
but occurs in a few places in the last stages of disintegration.

From the shores of the Basin Pond, where an unobstructed view is to
be had of the whole height of the walls, the granite, up to two thirds the
height of the eastern side, or about the upper limit of the gray variety,
is seen to be arranged in concentric sheets, that dip west at an angle
varying from 45° to 60°. On the southern wall the same concentric
arrangement prevails, the layers dipping north, often at angles higher
than 60°. Above the part that lies in concentric sheets is the red
granite, which divides, on weathering, into blocks more or less regular
in form. Near the head of a torrent that comes down from the Saddle,
in two instances the red variety (5) lies in blocks, with forms so definite
as strongly to resemble courses of cyclopean, but crumbling masonry.
At the foot of these “castles” the rock is so friable as to fall into gravel
under the tread.

What has been said of the occurrence of the red and gray granites, at
different elevations, does not mean that they are separated from each
other by any well-defined horizontal plane. : They are undoubtedly parts
of one and the same formation, and, as in the quarries of Quincy and
Cape Ann a variety of rock having one color passes into a variety of
another color so gradually that the separation cannot be said to take
place along any line, or plane, so at Ktaadn the red and gray granites
merge into each other in the same way, and at various levels. Yet it is
substantially true that the lower two thirds of the basin walls, and
probably the whole of the mountain mass below the level of the basin
floor, consist of the gray, and the upper 700 feet of the red granite.

As has been remarked already, the granite of Ktaadn is singularly
free from dikes and veins. During the explorations made both in 1879
and 1880, not a dike or vein was discovered, either in the fixed or
loose rocks of the mountain. We have seen that the same was true,
with but two exceptions, of the ledges and bowlders that were observed
upon the Penobscot. The absence of these characteristics of older rocks
will be held to indicate that the granite of Ktaadn and its vicinity is of
comparatively recent origin.

The only considerable departure from the normal granitic type is the
occurrence of very numerous inclusions which resemble imbedded frag-
ments of foreign rock. Like patches are common in most granites, but
I have never known elsewhere so many as the Ktaadn granite presents.
Upon the talus beneath the east wall of the basin a small block of red
granite was observed which contained five visible inclusions, varying from

aie BULLETIN OF THE

two and a half to seven inches in diameter. In respect to numbers, this
was an exceptional case, but single inclusions met the eye at every
turn. Of specimens collected in the basin, some have their outlines
sharply defined, but others merge gradually into the enclosing granite.
As usual, they are finer in grain, and of darker color, than the sur-
rounding rock, being commonly of a deep gray, but sometimes lighter
from the presence of imbedded crystals of white feldspar. Upon the
Southwest and East Slides a few inclusions were found of another char-
acter. Of these, one was brought away from each locality, — the best
of its kind. They seem to be fragments of almost black mica schist,
are angular on all sides, are separated from the granite by lines per-
fectly distinct, and were selected as pieces of foreign rock which had been
caught up by the granite and included within its mass.

Inclusions in granite have long attracted attention, but have not
been the subject of much investigation. A clear and extended discus-
sion of their nature, with figures of specimens and a record of analyses,
may be found in a paper, by J. Arthur Phillips, entitled “On Concre-
tionary Patches and Fragments of other Rocks contained in Granite.” *
In his “ General Conclusions,” the author makes the following state-
ment: ‘The inclusions contained in granite are of two distinct kinds.
Those of the first class [which are spoken of throughout the article as
concretionary, though not exhibiting a concentric structure] are the re-
sult of an abnormal arrangement of the minerals constituting the granite
itself, while those belonging to the second represent fragments of other
rocks enclosed within its mass.” (p. 19.) Most of the patches observed
in the basin must be assigned to the first class, while the specimens
brought from the slides seem clearly to belong to the second.

The forms which the several parts of the mountain now present, and
the condition of their surfaces, are largely due to the original structure
and mode of weathering that characterize the rocks. As the highly in-
clined concentric sheets in the basin walls break away, and fall upon
the talus below, other faces of equal inclination are exposed; while the
red granite of the higher parts, deprived of support, in turn gives way,
and thus the steepness of the walls is maintained. Similar steep faces,
due to the concentric structure of the granite, abound upon other parts
of the mountain, as on the flanks of several spurs, and about the base
at various points.

The crest (a feature unique among Eastern mountains) that occupies
most of the space between East Peak and the Chimney owes its form and

* Quar. Jour. Geol. Soc. of London, Vol. XXXVI. pp. 1-22, February, 1880.

MUSEUM OF COMPARATIVE ZOOLOGY. 213

preservation to the circumstance that the modified red granite which
makes it up divides in weathering into plates, which, when undisturbed,
stand vertically on edge. They vary in thickness from an inch, or less,
to upwards of a foot. Where their trend is in the same direction as the
ridge, there, as they have become loosened, and have fallen over the
cliffs on either side, the plates still left firm in place constitute a nar-
row crest. It is surmounted by a serrated edge, and, as one follows it
for the fourth of a mile, alternately ascending steep projecting points,
and descending into jagged notches between, he must again and again
walk along a mere blade of rock from one to two feet wide, having upon
one side the yawning gulf of the basin, and on the other cliffs too steep
for climbing.

From the crest southwest to East Peak, and between that and West
Peak, the rock plates stand crosswise of the ridge at various angles, and
there, as they have been loosened by frost, falling more or less out
of perpendicular, they still remain. Thus the blade-like form is lost,
and the ridge is somewhat wider, though still narrow. Bristling with
oblique, projecting plates covered with black lichens, these parts pre-
sent a savage and chaotic desolation that is probably without a parallel
in Eastern North America.

The very diverse conditions of surface upon the other summits —
hardly their forms — may be traced sometimes to variations in the
jointing of the constituent rock, but oftener to simple difference in firm-
ness. Thus, parts made up of the more friable red granite (other than
those modifications of it, represented by specimens 23, 25, and 57, that
divide into thin plates, and are confined to the highest summits only)
are covered with small-sized fragments, rounded by decay. These at
times assume, over wide spaces, the size, and almost the arrangement,
of cobble paving-stones, and in a few places the aspect of gravelled
~ areas. Such are seen chiefly on the northern summits.

Again, the middle of the northward slope, between the Table Land
and the Saddle, is piled with blocks of the firmer red granite, riven
from the mass beneath, of size so great as to render travel over them
extremely difficult. The Table Land is in parts smoothed by a covering
of wholly disintegrated material, but in general is strewn with tabular
blocks that increase upwards toward West Peak in size and number.
The half-mile between the head of the great Southwest Slide and the
brow above is literally a heap of huge blocks, constituting a slope that
varies from 36° below to 47° above.

The slopes south from the two chief peaks are covered with loose,

214 BULLETIN OF THE

angular, often tabular fragments, as far down as to the tree line,
which is everywhere upon the mountain very low, leaving an unusual
amount of naked rock above. These slopes present much the same
appearance as does the top of Mt. Washington southward from the
Summit House toward the Lake of the Clouds, except that on Ktaadn
the blocks are larger, and the slopes much more abrupt.

All the summits so far described are bare of vegetable growth larger
than lichens, or shrubs like the mountain cranberry, almost as diminu-
tive as mosses, and are therefore open to close inspection. The whole
rock surface has been so shattered that only on faces of cliffs too steep
to allow the accumulation of detritus is rock in place to be found. To
the east spur of Pamola, the ‘‘ Horseback,” the last statement will not
apply. This narrow ridge may be said, in a great measure, to have
shed its ruins as they have been formed. Consequently, the spur, over
all its upper part, exhibits along the ridge abundant granite in place.
Here, of course, the present surface is of recent origin.

Except a few paragraphs in the brief accounts of hurried visits
made to Ktaadn by Dr. Jackson and Prof. Hitchcock, contained in the
Maine Geological Reports, a brief article by the late Dr. John De Laski,*
of Vinalhaven, and a reference of three lines in the second and third
editions of Dana’s Manual of Geology, based upon an erroneous state-
ment of De Laski’s, I recall nothing in print that specially relates to
glaciation in connection with Ktaadn. Prof. Fernald’s observations for
the latitude of the highest peak make it to be.45° 53’ 40". The par-
allel of 46°, therefore, crosses the northern base of the mountain. Far-
ther north than Mt. Washington by over one degree and a half, and,
according to the computation of Mr. W. H. Pickering, 161 miles distant
from it in a straight line, and of New England mountains inferior in
altitude only to the highest summits of the Washington group, Ktaadn
becomes of so much interest that, but for the inaccessible nature of the
region, the mountain and its vicinity would long since have been thor-
oughly explored for testimony upon the question of a great northern
ice-sheet, and the existence of former local glaciers.

As might be expected, upon summits changed from the original con-
dition to the extent that has been indicated, days of search failed to
discover any signs of glacial strie, or polish. Examination for them
was made also, without result, on the lower slopes: first, where the
trail from the Aboljacarmegus Stream, about a mile from its beginning,
crosses a succession of bare granite areas, and at the next exposure of

* Am. Jour. Sci., [8.] III. pp. 27-31, 1872.

MUSEUM OF COMPARATIVE ZOOLOGY. 215

granite in the course of the trail, which is just at the foot of the pres-
ent terminus of the Southwest Slide. At both localities the rock is of
the coarse gray variety that is exposed at the third and fourth falls,
and is destitute of glacial markings. The surface is honeycombed by
decay, which, at the lower station, has gone so far that it was there
impossible to break out, with a heavy hammer, specimens which at all
approached a sound condition.

The only rock in place to be seen upon the Southwest Slide occurs
two thirds the way up from its foot, at an elevation of about 3,500
feet. It is a fine-grained, dark gray granite, approaching in appearance
some of the inclusions that are found in the basin, and well adapted to
resist decomposition. It lies, as at the stations below, in concentric
sheets,* which have here an inclination of about 30°, and is smooth,
hard, and free from all indications of decay; but not a scratch or
other sign of glaciation appears upon it. It is a small area, only sey-
enty-five feet along the slope, and perhaps a third as wide, and dis-
appears above, below, and at the sides, under the débris of the slide,
beyond the slanting face of which the ledge scarcely projects. If it was
first uncovered, in recent times, by the descent of the avalanche of 1816,
as from the surroundings seems not improbable, the absence here of
grooves and striz is significant as respects the glaciation of the higher
parts of the mountain.

If evidence of glaciation upon the summits of Ktaadn exists, it must
be other than that to be derived from smoothed and striated surfaces.
It will be maintained by many that such evidence is supplied by the
flat tops of the Table Land, and of several of the spurs, and by the well-
rounded northern summits and faces. To this it may be objected that
table-topped mountains are not wanting in regions where neither drift
nor other indications of glaciation have been recognized. The state-
ment, however, is open to the rejoinder that, in such cases, the shape
may be rationally accounted for by obvious peculiarities of structure, as
is the typical instance of Table Mountain, near the Cape of Good Hope,
which is a mass of granite capped by horizontal beds of sandstone.
The prevalence of steep faces upon the sides of Ktaadn, as already re-

* My observation of Maine granites in general, and especially at Mt. Ktaadn,
forees me to the conclusion that the concentric lamination of granite is due to causes
connected with the original structure of the rock, and not, as has been maintained
by Professors Shaler and Hunt, to superficial variations of temperature during the
changes of the seasons. It would seem, then, to be putting terms in their logical

order to speak of the conformity of present surfaces to the inclination of the granite
sheets, rather than of the lamination as conformable with superficial features.

216 BULLETIN OF THE

marked, is to be ascribed ultimately to the high inclination of the con-
centric sheets of granite; but there is absolutely nothing in the rock
structure that will help to account for the existence of a great plane
surface of above five hundred acres, like that of the Table Land. The
supposition that it is the work of moving ice is a natural and rational
one, provided the weight of proof in support of such an hypothesis is
greater than that of proof antagonistic with it. But to cite testimony
for, or against, any particular theory, does not come within the scope of
a brief paper like this, whose chief purpose is the presentation of facts.

Material interesting from its relation to the transportation of drift,
whatever may have been the agent that moved it from the north, is
not wanting upon Ktaadn. The two slides furnish the chief amount of
such material. The present Southwest Slide proper — the loose slide
— begins a little above the point where the old avalanche started, a full
half-mile below the brow of the Table Land, and terminates at the foot
of the most abrupt portion of the mountain. The length between the
points indicated, as estimated after repeated ascents and descents, is one
mile and three fourths. The width at the bottom is about 100 feet,
narrowing very slowly upwards. The difference of elevation between
the top and bottom is 1,774 feet, — the mean of two observations. In
its course the slide exhibits several terraces, at places doubtless where
it conforms to the varying slope of the solid surface of rock over which
it passes. The inclination, therefore, is variable. As tested with a
clinometer at several points, it appears to be as follows. From the foot
to the “Green Island,” * a small bush-grown patch upon the surface of
the slide, and 985 feet (mean of two observations) higher than its foot,
the inclination of the slopes between the terraces varies upwards from
24° to 28°; thence to the top it is 31°. The average inclination of the
rock-piled surface, from the head of the slide to the brow of the Table
Land, is 35°, but the last seven minutes’ climb is upon a slope of 47°.
Along the lower two thirds of the slide, drift is distributed in consider-
able quantity, but on the upper third it is rarely seen, and disappears
entirely before the top is reached.

The East Slide is less than a mile long, and is one continuous slope,
uninterrupted by terraces like those of the Southwest Slide. The in-
clination of the lower half was found to be 25°; of the next fourth, 28°;
of the upper fourth, 30°. Its foot lies about 200 feet lower than the
level of the Basin Pond, and its head is 1,000 feet above the same level,

* A landmark conspicuous for miles down the Penobscot, and recognizable in
photographs.

MUSEUM OF COMPARATIVE ZOOLOGY. 217

making the elevation of the head above the foot about 1,200 feet. It
had its origin in an avalanche which is said to have descended between
1820 and 1830. The two slides will in time disappear, as others before
them doubtless have, by the slow encroachment of shrubby growth from
the bottom and sides, now seen to be in progress. On the East Slide
much less drift is found than on the other. Outside of the slides, I
have never found drift upon the flanks of the mountain; but it re-
appears higher up, in very small amount on the Table Land, but princi-
pally upon the northern summits, sparsely strewn among the broken
granite that covers them. Neither on slides nor summits is the drift
ever found in large bowlders, but always as fragments of moderate size.
On the Southwest Slide a few masses were seen as heavy as a hundred
pounds each, but in general — always upon the East Slide — the pieces
ran from a few ounces up to twenty pounds in weight. They were
chiefly fragments of slates and sandstones, identical with the strata of
the country north and west, mingled with pieces of metamorphic and
trappean rocks, such as occur in place for a few miles beyond the Ripo-
genus Carry.

The fragments of stratified rocks on the Southwest Slide very gener-
ally include fossil shells, mainly Brachiopods, and always impressions or
interior casts. Owing to the small size of the enclosing masses, — due
to the fissile structure of the rocks, —the fossils ordinarily are much
decayed, but occasional specimens are obtained in fine condition. Among
the scanty drift upon the upper third of the Southwest Slide, I have
never seen a fossil-bearing stone. And upon those parts of the summits
where drift was found, only once was a fossil met with, —a solitary
Brachiopod impression on a ten-pound piece of sandstone, picked up on
the slope northward from West Peak to the Saddle, about 600 feet be-
low the top of the peak, or at an elevation of about 4,615 feet above the
sea. This is by far the highest point at which fossiliferous rocks have
yet been found upon Ktaadn.*

* Dr. De Laski’s statement of the height (4,385 feet) at which he found fossils,
“‘well up toward the ‘ Horseback’ ridge” (Am. Jour. Sci., [3.] III. p. 27), and
which is quoted by Prof. Dana in his Manual of Geology (editions 2d and 3d),
is founded upon a wrong estimate of the altitude of the mountain. He adopted
the one current for some years before Prof. Fernald’s remeasurement of the eleva-
tion, which he made to be 5,215 feet. Now the elevation of the ‘‘ Horseback”
ridge, at a point directly up from the head of the East Slide, —Dr. De Laski’s
route, — we make 1,181 feet above Basin Pond, while that of the summit of Ktaadn
is 2,287 feet above the same level. The difference 2,287 — 1,181 1,106 feet, the
difference of elevation between the ‘‘ Horseback” ridge, at the point named, and

218 BULLETIN OF THE

For a purpose presently to appear, it is pertinent here to introduce
an observation made by Prof. Hitchcock in the valley of Avalanche
Brook, a stream that, starting from the gorge between the Chimney
and Pamola, abruptly terminates the East Slide by sweeping away the
detritus at its foot, which the brook passes nearly at right angles. This
“valley,” where we saw it, is only a rocky channel, heaped with bowl-
ders of all sizes. In the dry season there runs, half hidden among the
rocks, a rivulet, which, in times of flood, becomes a furious torrent, and
fills the banks. Says Hitchcock : ‘‘ We ascended the valley of Avalanche
Brook on the south side of the mountain, and... . found an immense
number of bowlders of Oriskany sandstone, many of them highly fossilif-
erous..... We found none of these bowlders higher than the foot of the
slide, although others have found them a few hundred feet higher.” *

Among the other drift met with upon the slides, we found smoothed
and striated stones, scratched uniformly in the direction of their length,
and rounded at the angles. They are the first of their kind that have
been reported from Ktaadn. The best were as fine examples of what
are considered typical glaciated fragments as any that are figured as
such in geological works. The largest, weighing from ten to fifteen
pounds, were more deeply scored than the smaller; but being too heavy
to be borne many miles in our packs, they were unwillingly left behind,
and others of less weight were selected as specimens. Of two that were
brought away, one is a piece of hard trap rock (determined by Dr.
Wadsworth to be diabase) five inches long by two and a half at its
widest part, and weighing twenty ounces. The other is a thin piece of
fine-grained argillaceous sandstone, seven inches by three and a fourth,
split from some larger stone that was not discovered. Of such striated
fragments not more than a dozen in all were found upon both slides.
They were rare exceptions among drift that showed no striz. Accord-
ing to the testimony of books, and of several persons familiar with gla-
cial phenomena from their own observation, the specimens agree precisely
in character with stones worn at their angles, and grooved on their
faces, under the ice of existing glaciers. It is of course impossible to
conceive them to have been shaped and grooved simply by the friction
they would have suffered in descending by gravity down the slide among
the other debris.

the summit ; and 5,215 — 1,106 = 4,109 feet, the height of the given point of the
ridge above sea level. It was below this point, it will be observed, that De Laski
found his ‘‘ upper fossils.”

* Prelim. Rep. Nat. Hist. and Geol. of Maine, p. 395.

MUSEUM OF COMPARATIVE ZOOLOGY. 219

All the facts in the case serve to indicate that the non-granitic ma-
terial found upon the mountain is a portion of the so-called “ northern
drift,” with the fact of whose distribution — not the manner — we are
here concerned. But we may and must suppose that in the distribu-
tion the sides and summits of Ktaadn, as far up at least as 4,600 feet,
received deposits of drift more or less in quantity. Through the action
of gravitation the slopes have become loaded with fragments of granite
that have been wedged from its mass by frost. Ktaadn has thus been
buried under its own ruins, and beneath these ruins has been hidden
the drift that was deposited when the mountain was comparatively
intact. The avalanches which have produced the slides have brought
to light along their course the covered drift. Near the starting-point
of the descent, where the movement was superficial, little or none of
the hidden material has been unearthed ; but farther down, where the
avalanche ploughed deep, more was brought to the surface. The shorter
East Slide, therefore, which is superficial in comparison with the other,
shows far less drift than does the Southwest Slide ; while Avalanche
Brook, which flows over the steepest of the lower slopes, reveals in its
deep channel more of drift than has elsewhere yet been found upon the
whole mountain. There is reason to think that the bed of another
stream, that runs on the north side of the East Spur, will, if followed
up, yield like testimony.

But while proofs of the former presence of an ice sheet upon Ktaadn
are so scanty and questionable, seeming indications of local glaciation
are not wanting. The location and surroundings of three little ponds,
that lie just without the mouths of the basins, are at least signifi-
cant. Their waters are retained in place by low, irregular ridges, sit-
uated just where terminal moraines of glaciers issuing from the basins
would naturally occur. Those that hem in the second and third ponds,
counting from the outlet of the chain, on the supposition that they are
moraines, must have been deposited by glaciers that moved down from
the North Basin. The ridges that hold the first pond, and separate it
from the second, would seem to have been supplied by a glacier from
the South Basin. Entirely satisfactory determination of the nature of
these ridges is impossible while they are, as at present, completely masked
by dense thickets ; but should fire hereafter lay them bare, opportu-
nity will be afforded for thorough examination before a new growth
springs up.

The outlet of the first or lower pond is cut to the depth of about
twelve feet, through a ridge of débris that appears to be the continua-

220 BULLETIN OF THE

tion of the one which runs along the eastern margin of the same pond ;
and there can be but little doubt that the loose structure observed at
the outlet prevails through the whole length of the retaining ridge.
But as a running stream can speedily change stones over which it passes
from irregular and angular forms to rounded and smoothed water-worn
pebbles, such as now cover the surface at the outlet, no proof that the
material of the ridge has the characters of a moraine deposit is attainable
till an amount of digging is performed for which we had neither time
nor tools.

Half a mile from the point last named is a little bog, fifty by one
hundred feet in extent, represented in the heliotype as a faintly drawn
pond. Going outward from the basin, one steps from the surface of the
bog directly upon the foot of a narrow ridge, which rises abruptly to the
height of twenty feet, and as abruptly falls off on the opposite side to a
level much lower than that of the bog. Its relations to the adjacent
heights favor the view that it is the terminal moraine of a glacier that
came down a wide depression of the mountain side, between Pamola,
the “ Horseback,” and its flat-topped branch. The hollow is widest and
steepest above, and would constitute a promising gathering ground for
a glacier. So far as could be ascertained, without extensive digging, the
elevation apparently consists of loose material, which might be regarded
as moraine débris.

Higher up in the same hollow, and nearly at the end of the flat-
topped spur, is another diminutive pond, nestled behind what looks
from a distance like the remnant of a moraine deposited later than
the one below, and of which the greater part has been removed by de-
nudation. These ponds will forcibly remind one who is acquainted
with Viollet-le-Duc’s “Mont Blanc” of the small lakes held in place
upon that mountain by like ridges, which are described as undoubted old
moraines.

The mouth of North Basin is shut across by a low hill, to be seen
in the heliotype. Viewed from the northern summits, it seems to be
the last deposited terminal moraine of a glacier which once occupied
that basin; but on closer inspection its aspect changes, and it is to be
regarded only as a possible, not a probable moraine. And, indeed, as is
implied in the foregoing statements, the moraine-like form and location
of the elevations which have been considered should be held, prior to
thorough investigation, as indications that they may be, rather than
proofs that they are, deposits from local glaciers.

Whether the depression on the northern side of the “ Horseback”

MUSEUM OF COMPARATIVE ZOOLOGY. 221

was, or was not, the track of veritable glaciers of a former period, it is now
occupied at intervals by moving masses that approach as nearly to the
character of glaciers as changed climatic conditions permit. The hollow
is so broad, comparatively shallow, and smoothly concave in outline,
that it cannot have been fashioned by running water, which on Ktaadn
leaves its mark always in deep and narrow gorges. At about the mid-
dle of the concavity an open strip, ten or twelve rods wide, and com-
pletely cleared of trees, runs down the slope, for more than a mile from
the bare upper mountain, through thick woods below. The growth, at
the intermediate point where we struck the strip, is one of spruces
twenty feet high, that rise like a wall on either side of the square-cut
opening; while the strip itself is covered with growing bushes that
averaged, last September, less than five feet high. Among the bushes
lay prostrate, with their tops pointing down hill, small spruce trunks,
bleached and dry, and evidently for some years dead. None of them
were more than ten feet long. The dead trunks had been simply
broken near the ground, and still lay attached to or near their bases.
That the movement which cleared the strip is one that occurs only at
intervals of some years, is proved by the considerable size the trunks
had attained before they were broken down; and that at least one
descent had taken place since that which felled them is shown by the
fuct that the eastern border of the strip, for a width of two rods, was
free from bushes, but was covered with levelled spruces as large as those
of the adjacent wood, and still retaining their branches and bark in
nearly fresh condition. Here the thickness of the trunks was so great
that they were not broken, but the roots were torn from the scanty
soil on the upper side, leaving in the earth those that extended in
the downhill direction. The mass that last descended was two rods
wider on the east than any other which for many years had passed
down the path. It must have levelled, for the time being, the bushes,
whose elasticity saved them from breaking, and restored them to the
upright position.

The inclination of the hollow, through its wooded portion, is mod-
erate for Ktaadn. It is evident that snow, accumulated on the bare
and steeper slopes above, under conditions that have recurred only after
periods of some years, has swept down as an avalanche with an impetus
that bore it far over the forest-obstructed smaller slope below.* In

* Under peculiar conditions, a trifling slope may serve, not only for the transmis-
sion, but for the origin of an avalanche. In Angusta a street, 100 feet wide, runs
west from the river directly up the terraces before described to the general level

922 BULLETIN OF THE

its progress it has successively prostrated, buried, and passed over the
opposing small trees, in no case, at the intermediate part which we saw,
carrying away the trunks or branches.

Certain huge blocks of granite that lie on the floor of the South
Basin have been regarded by some as erratics, but in fact are parts of |
the adjacent cliffs, and owe their present location indirectly to the
agency of ice. They are fragments of the eastern wall, which, falling
upon inclined planes of compacted snow or ice accumulated in winter
against the basin sides, have slid or rolled several rods beyond the
great talus, 350 feet in height. Lying so far beyond the talus, which is
the receptacle of most descending fragments, they have been mistaken
for erratics, notwithstanding their agreement in composition with the
nearest cliffs. In the same way alone can we account for the presence
of great rock masses at stations so far out from the northern foot of Pa-
mola that they cannot be supposed to have rolled thither over any other
surface than an inclined plane of ice. Here, too, somewhat west from
where the foot of the cleared strip must be, are four approximately par-
allel ridges made up of granite blocks of all sizes. They are of consider-
able length, and have between them hollows fifteen or twenty feet deep
and some rods wide, but of unequal width. They appear too recent, —
resembling parallel tali of fresh material,—and too near together, to
correspond to my notion of old terminal moraines ; and I was unable
to explain their origin in any way satisfactory to myself.

A change that was produced in a part of the southern lobe of South
Basin, during the early summer of last year, is instructive, as illustrating
the origin of the Ktaadn slides. The gorge between the Chimney and
the peak of Pamola —a typical instance of erosion — is a deep and nar-
row cut, forty feet wide at its head, dimin’shing to ten at the foot, and
upon its floor to two or three feet at the outlet, where it is a polished, con-
cave water-course worn in the solid rock. Its small drainage area, and
evidence derived from the accumulations about its foot, show that even
in times of flood it ordinarily carries a stream of but moderate size. In
the summer of 1879 the débris that had been brought down in a series
of years extended downward from the foot in the usual fan-shaped “ cone
above. The hillside from the upper terrace to the top is 1,300 feet in length. The
inclination of the street near the summit is 11°; midway, 7°; below, from 3° down
to 0°. Early in the winter of 1878-79, the snow, after continued rain, assumed the
slushy state, and, starting from the middle of the hill, where the inclination is only
7°, rushed suddenly down the street with a roar, and piled itself on the level ground

at the foot. On the steeper upper half the snow lay unmoved. In the ninety years
since the street was opened, this is the only case of the kind recorded.

MUSEUM OF COMPARATIVE ZOOLOGY. 229

of dejection,” rendering passable the portion it overspread of the talus,
which, except at like places, is almost inaccessible from its base, being
there made up of huge blocks like ‘‘ monolithic houses tumbled together
by an earthquake.” The cone was furrowed by no deep channel, such
as would have been formed had a large and powerful stream passed over
it. In September last the whole had been changed. Without pausing
for details, it is enough to say that a gully had been cut to a depth of
fifteen feet, down which, at a quarter of a mile’s distance, was piled,
twenty feet high, a heap of bowlders, varying from ten feet in diameter
down to those of moderate size, all mingled with earth and gravel.
Here the first rush of water which effected the change was checked, and
its course deflected. Lower down, smaller blocks were distributed in the
order of their size ; then came cobbles, next pebbles, then gravel, till at the
distance of more than half a mile, and near the Basin Pond, one stepped
suddenly down from a square-ending sand terrace two and a half feet
high. Such an exhibition of material assorted by water, within so small
a space, is rarely to be seen. A water-spout, or “cloud-burst,” upon the
peaks had wrought the havoc. It must have been confined to a nar-
row area, for signs of disturbance were wholly wanting on the talus half
a mile north; and in the bed of the torrent, less than a mile distant,
which descends from the Saddle and was both years our daily route from
camp at the Basin Pond to the summits, no change from the previous
year had happened. The time of the occurrence was fixed by valid
proof. Scrub birches were found in the course of the flood completely
stripped of bark, but often retaining at the tips of their highest twigs
‘shrivelled leaves, which showed by their thinness that the shrubs had
been torn from place just as the leaves were fully expanded.

Heliotype taken from a model of Mt. Ktaadn, representing the upper three
thousand feet of the mountain, and an area of about ten miles in length by seven
in width. The vertical scale of the model is three times greater than the hori-
zontal. Lack of shade renders some of the features indistinct.

No. 6. — Report on the Recent Additions of Fossil Plants. By
Lio LEsQUEREUX.

In the department of Paleophythology the collections of the Museum
have been this year greatly increased by the following contributions : —

1. The Smithsonian Institution has presented one hundred specimens
of tertiary and cretaceous plants, obtained by the U. 8. Geological Sur-
veys of the Territories under the direction of Dr. F. V. Hayden. They
are referable to species published in the Cretaceous and Tertiary Floras,
Vols. VI. and VII. of the U. S. Reports.

2. More than six hundred specimens of cretaceous fossil plants have
been obtained in the Dakota group of Kansas by Mr. Charles H. Stern-
berg. These specimens, in a remarkably good state of preservation,
represent forty specific forms, of which about twenty are new, and six
known only as yet by the descriptions of Professor Heer.

The new species are referable, like those published already from this
formation, to all the essential divisions of the vegetable kingdom. The
Cryptogamous have fragments of a Jeanpaulia? and of an Lquisetum.
The Conifers are represented by a large Thuites ; the Cycadez, by three
or four species of Podozamites. The Phznogamous Apetalee have a
Myrica, an Alnites, a Quercus, two species of Ficus, and a Laurophyllum ;
the Dialypetalee, an Aralia, three distinct forms of Araliopsis, a Cissus,
four species of Liriodendron, an Anona, a Greviopsis, a Sapindus, and a
ithamnus. Besides these new species there are in the collection speci-
mens of Populus litigiosa, Ficus primordialis, Diospyros primeva, already
described by Heer from the Dakota group, with Proteoides lancifolius,
described by the same author from the European Cretaceous of Qued-
linburg, and Magnolia speciosa, from that of Moletin. Some other very
rare species, like Popudites elegans, Platanus primeva, Magnolia tenuifo-
ha, Liriodendron giganteum, Aralia Towneri, Aralia saportanea, divers
species of Protophyllum, and especially Aspidiophyllum trilobatum, are
represented also by numerous beautifully preserved specimens. Taken
all together, this collection is therefore a valuable acquisition for the
Museum.

VOL. VII. — No. 6. 15

226 BULLETIN OF THE

It is not less valuable in regard to the data which it affords in con-
firmation or contradiction of some of the general conclusions derived
from the examination of the materials formerly described from this
peculiar cretaceous flora.

For example, the disconnection of the flora of the Dakota group from
that of the older ones, those of the Jurassic times, does not appear now
as positive as formerly, or as it was indicated in the Cretaceous Flora,
Vol. VI. of the U.S. Reports. For besides the Pterophyllum described
in that volume as somewhat doubtfully referable to the Cycadez, plants
which essentially constitute the vegetation of the Jurassic, we have now
four species of the genus Podozamites either identical with or closely
related to species known from this formation.

Per contra, the disconnection of the Cretaceous flora from that of the
lower Tertiary appears now still more evident, as the new species do
not indicate any affinity to the plants of the Laramie group, which is
positively Eocene by its types. As yet no vegetable remains distinctly
referable to Palms have been found in the Dakota group.

The vegetation of the Cretaceous seems to be essentially composed of
synthetic types, genera or groups of plants of analogous characters,
which it is extremely difficult to define and separate into species. And
nevertheless, when considered separately, the leaves, which are as yet the
only organs obtained for analysis, show points of difference so marked
that it is not well possible to consider them as representing mere varieties.
To prove this assertion, it is sufficient to examine the so-called species
described under the generic names of Populites, Platanus, Araliopsis (a
new division which includes most of the leaves described as Sassafras),
Aralia, Protophyllum, Menispermites, etc. One of these types, however,
the more peculiar and distinctly cretaceous in its facies, Liriodendron,
was until now represented by few diversified forms, and therefore con-
sidered as simple, and the supposition seemed confirmed by its passage,
with Platanus, Sassafras, and Fagus, through all the geological ages from
the Cretaceous to our time, with scarcely any modifications and few
representatives. But now the collection of Mr. Sternberg eliminates
this exception, as we find in it four new and very distinct forms of this
group, besides a beautiful entirely preserved leaf of Liriodendron gigan-
tewm, which had been described from a mere lateral lobe, and which was
therefore of uncertain attribution.

A short description of this genus, and of its species as exposed by the
leaves, may show how uncertain, though binding, are the characters of
the Cretaceous leaves.

MUSEUM OF COMPARATIVE ZOOLOGY. 227

Genus Liriodendron. Leaves panduriform, oppositely bilobed ; lobes oblique
or in right angle, obtuse or acuminate ; midrib thick ; lateral veins in right
angle, opposite or irregularly alternate.

1. L. giganteum. Leaves large, twenty centimeters broad between the lower
broad (six centimeters), oblong, obtuse or rounded lobes ; upper lobes shorter,
slightly turned upwards, narrowed and rounded to an obtuse point, joining the
lower in an obtuse sinus at a short distance (two centimeters) from the medial
nerve.

This form is the éne more distinctly related to Liriodendron tulipifera,
the species living at our epoch. It cannot be considered identical with
it, however, the difference in the characters of the leaves being too
marked, but not more so than in the following forms, which I consider
as new species.

2. Liriodendron acuminatum, sp. nov. Leaves small, about half as large as
in the preceding species, cut in two pairs of narrow linear acuminate lobes,
about one centimeter broad, all curved upwards.

3. Liriodendron cruciforme, sp. nov. Leaves large, upper lobes broad, square
or equilateral, in right angle to the broad midrib ; lower lobes narrow, linear,
acuminate, much longer and turned upwards. The shape of the leaves is like
that ofan anchor, except that the medial nerve or axis does not pass above the
upper borders of the lobes.

4. Liriodendron semi-alatum, sp. nov. Leaves divided at the base in two
opposite short rounded lobes (one on each side) curving up to near the medial
nerve and then enlarging upwards into an obovate or spathulate entire lamina.

5. Liriodendron pinnatifidum, sp. nov. A single leaf withthe general facies,
and the venation of a Liriodendron, but subalternately trilobate on each side.
The top of the leaf is broken.

Besides the above forms, there have been described already, from the
Dakota group, Lirtodendron Meekii, Heer, a species with comparatively
small leaves, only three to five centimeters long, two to four centimeters
broad, the lobes equal in length, short and rounded ; and Liriodendron
primevum, Newb., from a leaf of which the upper half is destroyed, and
whose characters are not sufficiently defined. By the size of the leaves, the
species is intermediate between LZ. Meekii, Heer, and L. intermedium, Lsqx. ;
form also known from a single lacerated leaf, which, narrow in the middle,
has long obtuse lobes turned upwards, and a facies different from that of
any of the other forms described. We have thus eight specific forms of
leaves representing the clearly defined type or genus Liriodendron, all dif-
fering so greatly that it is not possible to consider them as mere varieties
of one species only, and nevertheless of characters so closely allied that
their specific identification seems to be hazardous. And this, as said
above, is the case with most of the so-called species of the Dakota group.

228 BULLETIN OF THE

The difficulty is increased by the fact that by gradual modification the
leaves pass to evidently different generic types. The genus Liriophyl-
lum, for example, represents leaves of Liriodendron nearly round in out-
line, but split at the top and to below the middle in two lobes joined in
a narrow sinus upon the medial nerve, a peculiar division and facies
which have no analogy in any species of plants of our epoch. This new
genus is by its leaves intermediate between Liriodendron and Populus.

The local distribution of the leaves may be relied upon to give some
directions for the separation of species. For of course if the analogous
forms are found in separate and distant localities, the marked differences
are more likely to be specific. On this subject the specimens collected
by Mr. Sternberg afford good opportunity for examining the question.
Omitting details, it suffices to mention what is known of the distribution
of the leaves of Liriodendron.

L. Meekii is described from specimens found in Nebraska and Minne-
sota only. The specimen of LZ. prumevum is labelled Blackbird Hills,
Nebraska. This form is allied only to Z. semz-alatum of Kansas. L. in-
termedium is also from Nebraska, represented in one specimen only, and
has no affinity with any of the Kansas species. L. giganteum was first
described from a fragment found near Fort Harker, Kansas, while the
specimen of the Museum is from two and a half miles from Glascoe, in
another county, where also were found L. acuminatum and L. pinna-
tifidum, whose leaves have little affinity of characters between them.
L. semi-alatum was found at a different locality seven miles distant from
Glascoe, and Z. cruciforme at Elkhorn Creek, twelve miles northwest of
Ellsworth.

From this kind of distribution it seems legitimate to conclude, not
only for Liriodendron, but also for all the other groups of this flora
whose leaves present the same degree of affinity or of difference, that, if
the forms are derived from synthetic types, and if they are found some-
what modified in characters at distant localities, it is a proof that the
modifications are already fixed, have become local characters, and that
they may be considered as specific.

On another question, that of the derivation of, the vegetable remains
found in the strata of the Dakota group, and of their distribution, either
in place, from trees grown there, or as transported by water from dis-
tant localities, a question examined already in the Cretaceous Flora, the
collection of Mr. Sternberg affords the same degree of evidence as for
the preceding.

It has been observed in the Flora, Vol. VL., loc. cit., that the Creta-

MUSEUM OF COMPARATIVE ZOOLOGY. 229

ceous leaves and other remains of plants are found always spread over
small areas, generally less than one or two acres in surface, and far dis-
tant from each other, so that in travelling over the prairies of Nebraska
and Kansas, the collector may wander for twenty to forty miles or more
without discovering a single fragment of fossil vegetable, and abruptly
come to one rich deposit where leaves are found in abundance. Gen-
erally each of these deposits has remains of plants of a peculiar group,
even sometimes of a single species. For example, Aspidiophyllum leaves
are from one place only ; Aralia Saportanea, from two widely distant.
Protophyllum and Sassafras, or Araliopsis cretaceus, and its varieties,
abound at Thompson’s Creek, while species of Salix and Podozamites
are from Elkhorn Creek and Glascoe ; and so on. The localities where
the specimens examined were found are twenty in number, and in each
of them only two to a dozen species have been recognized. A group-
ing of this kind shows that the leaves were derived from trees grown in
place where the leaves are now found, the trees apparently covering hil-
locks, or dry surfaces of land, disseminated in wide lagoons. As floated
from a distant shore, the leaves should be more or less, but always,
mixed. Their fine state of preservation, their position generally flat,
confirm this supposition.

3. A second lot of specimens from the same formation has been pro-
cured for the Museum in Colorado, near Morison, by Rev. Arthur Lakes.
The number of specimens is small, and the species which they represent
are all, except one, already known from the Dakota group of Kansas.
Among them are Proteoides grevillieformis, P. daphnogenoides, Magnolia
alternans, M. Capellini, described by Heer in the Phillites of Nebraska,
Sassafras cretaceus, Newb., Salix proteefolia, with Liriophyllum popult-
folium, L. Beckwithi, Aralia Towneri, Sterculia lugubris, and species of
Ficus, most of them found in Kansas, and already figured for the eighth
volume of the U. S. Reports. One of the species only, a peculiar small
form of Liriophyllum, is new.

4, The last addition of this year to the phytopaleontological depart-
ment of the Museum has been made by the acquisition of nine hundred
specimens of coal plants from Mr. I. T. Mansfield of Cannelton, Pennsyl-
vania. This locality has until now furnished to the coal flora an abun-
dance of vegetable remains of species rarely found elsewhere. Of the
genus Cordaites, for example, formerly known by separate leaves or
mere fragments of leaves only, specimens have been found there with
branches bearing leaves, and even flowers and fruit. A proportionately
large number of specimens of this kind are in the Cannelton-collection,

230 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.

which represents fifty species, mostly in finely preserved materials.
Among the species worth mentioning are Odontopteris cornuta, Callipte-
ridium inequale, Alethopteris ambigua, divers species of Stemmatopteris
and Caulopteris, Lepidostrobus spectabilis, Lepidophyllum Mansjieldi, Spo-
rocystis and Lepidocystis species, Teniophyllum decurrens, Rhabdocarpus
Mansfieldi, all peculiar to the locality, or not as yet found elsewhere,
and splendid and numerous specimens of the rare spikes of Macrostachia
infundibuliformis, Neuropteris cordata? Brgt., or Cyclopteris trichoma-
noides ?, N. heterophylla, Brgt., Pseudopecopteris Pluckneti, and P. anceps ;
many specimens of Spiropteris, circinnate branches of ferns (spirally
coiled inward in the process of unfolding), of Szgillaria monostigma, of
Artisia (decorticated stems of Cordaites), of Cordavanthus (their flowers),
of Cordaicarpus (their fruits), ete. As the Museum had not any spe-
cimens of that peculiar locality, these plants constitute an important
addition to the collection.

With the materials obtained this year the Museum has now in fossil
plants : —

1. From the Devonian, a series of specimens presented by Professor
J. W. Dawson and Mr. C. T. Hartt from the measures of Canada, and
from England a number of very fine ones, presented by Sir Charles
Lyell. Among these is a splendid fruiting pinna of Archewopteris Hyber-
nica.

2. From the Carboniferous, a large number of the best specimens
found in the nodules of Mazon Creek, the shales of Morris, and other
localities of Illinois; numerous and good specimens from the anthracite
basins of Rhode Island and of Pennsylvania ; fine materials from divers
localities of Ohio and Kentucky, presented by Mr. Anthony ; rare speci-
mens from the subconglomerate measures vf Ohio and Tennessee; and
the collection of Cannelton mentioned above.

3. From the Cretaceous of the West the Museum has now an amount
of materials sufficiently representing the Dakota group. Fine and nu-
merous specimens can be spared for exchange.

4. The Tertiary of this continent is insufficiently represented in the
Museum by a number of specimens presented by the Smithsonian Insti-
tution, and by a few sent by Rev. Arthur Lakes from Golden, Colorado.
There is, per contra, from Europe a splendid collection of Miocene
plants purchased from Professor Heer, of Zurich, and a number of un-
determined specimens from divers formations and localities, mixed with
animal remains, in the collection of Bronn.

No. 7.— The Great Dike at Hough's Neck, Quincy, Mass. By Joun
ELiotT WOLFF.

Tus dike is situated some two and a half miles northeast from
Quincy Depot ; rising, when first seen, as an irregular ridge, and con-
tinuing, with interruptions, for about a mile in an easterly direction.

Mr. Crosby has mentioned this locality in his “Contributions to the
Geology of Eastern Massachusetts ”: * — “On Hough’s Neck, in Quincy,
the amygdaloid is a green, slaty rock ; it is sometimes amygdaloidal,
and sometimes porphyritic, and includes masses which resemble felsite.
It. occupies the axis of an anticlinal in the conglomerate ; and also cuts
the latter rock very freely, after the manner of an eruptive.” (p. 176.)
Again: —‘‘On Hough’s Neck, in Quincy, along the north side of Rock
Island Cove, there are prominent ledges of conglomerate flanking a large
mass of amygdaloid, and the latter rock crops through the former in iso-
lated bands, due to extravasation or faulting. The conglomerate strikes
about east-west, and shows nearly vertical dips to the north and south,
dipping away from the amygdaloid. It holds unmistakable pebbles of
Shawmut breccia. This is clearly a faulted anticlinal fold. Toward
the north, over the area marked as slate, the rocks are all concealed by
drift ; but on the south the conglomerate shows very plain indications
of a passage to slate.” (p. 209.) The amygdaloid, constituting a mem-
ber of Crosby’s Shawmut group, is regarded by him as older than the
overlying Primordial conglomerate, and as a sedimentary rock in general,
though sometimes presenting evidence of intrusion.

The country rock of the dike is a coarse conglomerate, with occasional
interbedded layers of red sandstone and slate. At the eastern end it is
bordered on both sides by the conglomerate. After running for a quar-
ter of a mile as a ridge, the dike suddenly loses its ridge character, and
occasional exposures only are found in the field to the east, among the
outcropping conglomerate ledges. It can be traced thus for a quarter
of a mile ; then for some hundred feet no outcrop of dike is found until
a small creek is reached. Crossing this, however, we again find a
dike continuing as a ridge in the same direction for some hundred yards,
when it disappears under the drift of a headland. This exposure, how-

* Occas. Papers, Bost. Soc. Nat. Hist., ITI., 1880.
VOL. VII. — NO. 7.

won BULLETIN OF THE

ever, is not in the line of strike of the main, or westerly part of the dike,
but lies some hundred feet to the north. Whether this change is due to
a horizontal throw, or to a fresh outbreak of dike along a parallel line,
does not appear.

At the western end, on the southern side, the junction with the con-
glomerate and red sandstone is very irregular,

large and small tongues
of the dike penetrate into the conglomerate, this rock having a strike
N. 60°-80° W., and a dip 70° south. The junction between the two
rocks is sharp and well marked : the dike seems often amygdaloidal near
the junction. Sections of the contact of the two rocks show that the dike
is composed of a mass of very small feldspars, having a beautiful fluidal
arrangement, while they are often bent when in contact with the line of
the conglomerate. On the northern side, a fine vertical exposure of the
junction is ebtained, which is seen to stand almost vertical ; the dike
cutting the slate and conglomerate a little irregularly, but standing
nearly parallel to the stratification. The conglomerate here is nearly
vertical, but may be said to dip tothe north very steeply ; if, however,
we pass east along the strike, a few hundred yards, to the exposures in
the field, we find that all the conglomerate, both north and south of the
line of the dike, dips steeply in one direction, i.e. south. I cannot,
therefore, agree with Mr. Crosby, that “ this is clearly a faulted anticlinal
fold.” It may equally well be an intrusion of the dike into the verti-
cally standing strata, causing irregularities of the dip. More detailed
study is required. In the western ridge the dike has a width of about
three hundred feet from contact to contact.

The rock is generally of a greenish color, approaching a greenish red
in the fresher portions ; it is irregularly jointed. In texture there is
great variation between coarse, fine, porphyritic, and amygdaloidal.
Masses of quartz, and yellowish-green epidotic material frequently occur.
These greenish masses are often very irregular, occasionally vertically
banded, and resembling fragments of a stratified rock, and often lined on
the exterior with a band of reddish substance. Microscopic sections of
some of them give a mixture of quartz, calcite, epidote, and a whitish
opaque substance (kaolin ?), and show that they are in part areas in the
rock of decomposition, or segregation. ;

Although at first sight this dike appears to be a homogeneous mass of
rock, yet it is in reality composed of rocks belonging (in all probability)
to at least three separate eruptions, forming, instead of one, numerous
dikes. To this fact is largely due the noticeable variations in the area
of rock. First in order comes the amygdaloid, forming the principal

MUSEUM OF COMPARATIVE ZOOLOGY. 2350

mass of the rock, and eruptive through the conglomerate. In the
second place, a close study of the great area of this rock shows that
it is cut by a large number of narrow diabase dikes, generally but a
few feet in width (e. g. three feet), which do not have a marked amyg-
daloidal structure. In many cases they run almost parallel with the
trend of the amygdaloid ; in other cases they run obliquely, while
others again may cut almost transversely across it, in parallelism with
a third dike to be mentioned. These dikes show generally well-marked
contacts with the amygdaloid : they are fine-grained at the junction,
but coarse-grained in the centre; in some cases they have melted
the amygdaloid at the contact, so that it is difficult to find the actual
line. Some of them are easily distinguished from the amygdaloid, un-
der the microscope, by the large amount of augite which they contain,
but in others this mineral cannot be found as such, for all trace of it
(if originally present) has been lost in the alteration products. Lastly,
about the middle of the large western exposure of the amygdaloid there
is found a large dike (at least seventy feet wide) running transversely
across it, in a direction N. 5°-10° W. On the south side it is seen
breaking through the conglomerate and sandstone, and can be traced
from that locality across the amygdaloid. No exposure was found giving
the actual contact of this rock with any of the others, although it can
be seen at a distance of a foot or two from them. Judging from its
direction, which cuts directly across the trend of a great number of the
small dikes, it would seem to be the latest rock of all. Some of the
small dikes to the east of it are, however, nearly parallel with it. While,
therefore, there seem to be at least two periods of eruption subsequent
to that of the amygdaloid, yet some of these small dikes may cut the
others, thus complicating the phenomena still further. I have not been
able to find evidence of this beyond the difference of direction; and to
settle the question by the discovery of the actual contacts will be diffi-
cult, on account of the lithological similarity of all the eruptive rocks,
and the thick covering of lichens, which conceals everything, and makes
any work there laborious.

The amygdaloid sometimes loses its amygdaloidal character, so as
to resemble greatly the later dikes; but in such cases the passage is
gradual.

The microscopic descriptions which follow show that all these rocks
are altered basalts, and, together with the field relations, prove that
they are all truly eruptive rocks, breaking through the conglomerate,
while the later eruptive rocks cut the earlier ones.

234 BULLETIN OF THE

[1.] From Western End of Dike, North Side, near the Road, — one of the
small Dikes in the Amygdaloid.

Lens. A greenish-gray, felty-looking rock, containing minute grains
of pyrite, and small feldspar crystals. Traversed by veinlets of epidote.
— Section. White opaque feldspar crystals, and masses of opacite, mag-
netite, and pyrite, in a green chloritic groundmass. The feldspars have
generally the long ledge form of the basaltic triclinic feldspars, but
occasionally the form of Carlsbad twins of sanidin. They are entirely
altered to a fibrous and scaly aggregate, polarizing with yellow and blue
colors, — often with the brilliancy of tale. Colorless needles with cross
fracture (apatite) occur occasionally in the feldspars, and also aggregate
quartz. Between the feldspars lies a mass of green fibrous products, —
chlorite, viridite, etc., considerable epidote, magnetite, quartz, etc., —
rarely hematite and biotite. The magnetite often has the form of a
grating, reminding us of decomposed olivine. The feldspars occasion-
ally have a fluidal arrangement.

[2.] Contact of Amygdaloid and Conglomerate at Southeast Corner.

Section. A mass of small feldspar crystals, having a well-marked
fluidal arrangement, and surrounding decomposed crystals of olivine and
masses of magnetite and opacite. The olivine crystals have the charac-
teristic lozenge shape, blackened border, and irregular fissuring, while
the small parallel feldspars of the groundmass separate and flow around
the crystals. Some are altered within the black border to a light green
serpentine with fibrous polarization ; in others, while the centre shows
the brilliant polarization and the pitted surface of olivine (though the
greenish color is evidence of some alteration), the exterior zone of the
crystal has been altered to a bluish-gray substance, which in polarized
light is seen to contain fibres with brilliant polarization, and may per-
haps represent a stage in the alteration to tale. Some of the olivines
are wholly or partially altered to ferrite and talc, the latter polarizing
very brilliantly. Some of the magnetite and opacite in the section is
derived apparently from the complete alteration of grains of olivine.
The feldspars have generally the long ledge character of the basaltic
feldspars, though some have the form and optical properties of Carlsbad
twins. Occasionally there is found a crystal sufficiently fresh to show
the multiple twinning, but generally they are filled with greenish or
transparent scales, while along the centre of the ledge crystal there
runs a line of green chloritic material, containing generally less opacite

t

MUSEUM OF COMPARATIVE ZOOLOGY. Zot

o

than the similar substances lying outside the crystal, but often continu-
ous with them. Some of the crystals are more than half filled in the
centre by a rectangular mass of this chlorite, often extending through
to connect with that outside. The space between the feldspars is occu-
pied by chloritic materials, opacite, etce., together with some quartz.
Epidote and quartz occur in the groundmass as alteration products, and
transparent needles, frequently broken across, which are probably in part
apatite. Along the line of the conglomerate some of the feldspars are
bent. j

[3.] West End of Amygdaloid very near [1].

Lens. A gray-colored groundmass, containing white and greenish
feldspar crystals, spots and crystals of epidote, occasional quartz and
epidote amygdules, and reddish areas of decomposition. — Section. Com-
posed principally of feldspars, with considerable epidote, chlorite, opacite,
etc. The feldspars are mainly plagioclase, but there are occasional
Carlsbad twins of sanidin. Some of the large porphyritic feldspars
are broken and fragmentary ; an effect, apparently, of the flowing base,
for the small feldspars diverge, and flow around the large crystals. In
Some cases they are seen to have been pushed into the large crystals
a certain distance on opposite ends along the central line, while a line
of base passed through the crystal connecting the two tongues. This
base, however, is now altered to calcite, chlorite, epidote, etc. Occasion-
ally two feldspars interpenetrate each other. The products of their de-
composition are the same greenish or colorless scales (which often have a
brilliant polarization), epidote, chlorite, calcite, quartz, and colorless nee-
dles.. The smaller feldspars seem less decomposed than the larger ones.
Between the feldspars lie masses of chlorite, epidote, opacite, calcite,
magnetite, etc. ; often in the form of wedges between the diverging feld-
spars. One grain of altered olivine is seen in the section, identified by
the shape and the previously described motion of the groundmass and
base around it. The exterior consists of reddish ferrite, penetrating
along the fissures ; the interior of quartz.
[4.] West End of the Amygdaloid near [1] and [3], but nearer in the Cen-

‘tre of the Mass.

Lens. Similar to [3]. — Section. The large feldspars are broken by
the base, as described above. Plagioclase and sanidin occur. True
amygdules occur here, recognized as such by the regular shape, and by
the fact that the small feldspars of the groundmass flow around the

236 BULLETIN OF THE

cavity and are distinctly separated from it. They are filled with epi-
dote, chlorite, calcite, quartz, and a fibrous chalcedonic (?) material :
the epidote is generally on the outside, the chlorite inside. Consider-
able epidote is scattered through the section, generally outside of the
feldspars, and also talc, calcite, and quartz. These decomposition prod-
ucts often occur in the groundmass in rounded areas, but are not true
amygdaloids. Patches of reddish: opaque ferrite also occur in a similar
manner, constituting the red spots seen macroscopically.

[5.] Western Ridge of the Dike on the West Side of a Road which crosses
at, — taken towards the Centre of the Mass.

Lens. A greenish groundmass containing porphyritic feldspars, red-
dish and greenish areas of alteration, and rounded masses of quartz.
The groundmass has intruded into some of the Jarge feldspars. —
Section. Crystals of feldspar and areas of decomposition or infiltration
surrounded by a greenish chloritic mass. The large feldspars are occa-
sionally Carlsbad twins; the small ones of the groundmass principally
plagioclase, although some are twinned sanidin crystals. The (original)
base, carrying small feldspars, has bent some of the large feldspars, and
pushed into them. Others contain in the centre square zonai inclusions
of the greenish mass, while the outer zone of the crystal is free from
it. These phenomena are similar to those so frequently observed in the
unaltered basalts with a glassy base. Many of the larger feldspar crystals
are partly filled with epidote grains, chloritic material, and light-green
needles, which have a yellowish-white polarization. Rounded areas, com-
posed of greenish chloritic fibres, with sometimes a deep violet blue
color between crossed nicols, occur in the groundmass, mingled occa-
sionally with talc, and bordered by epidote. Some of these areas, en-
closing the remains of the small feldspars, arise from the decomposition
of the groundmass ; others are either true amygdules, as described above,
or some might be pseudomorphs after some mineral, — for instance, oli-
vine. Between the feldspars lies the green mixture of chlorite, viridite,
and greenish needles similar to those described in the feldspars, beside
some epidote, calcite, and quartz.

[6.] Western Ridge of the Amygdaloid, about fifty feet east of a Road
crossing it, — the Specimen taken from a long Dike crossing the
Amygdaloid obliquely to its Main Trend.

Lens. A grayish-green groundmass, holding crystals of greenish
feldspar and grains of pyrite. The groundmass has pushed into some of

MUSEUM OF COMPARATIVE ZOOLOGY. 237

the long crystals. Powder feebly magnetic. — Section. Much decom-
posed. The feldspars retain their outline, but are filled with chloritic
material, — kaolin, epidote, and calcite. Magnetite is very plentiful in
crystalline and irregular forms, having often a whitish, decomposed sur-
face (leucoxene), which, in connection with the reticular or branching
shape of the masses, shows the presence of menaccanite. Pyrite occurs
in oceasional grains and square crystals, generally close to or mingled
with the magnetite or decomposed menaccanite, and is therefore proba-
bly an alteration product. The remaining portion of the rock is a con-
fused mixture of chlorite, epidote, quartz, viridite, hornblende, calcite,
and colorless needles, in part probably apatite, — all products of altera-
tion. This rock is the most coarsely crystalline and the most decom-
posed of any examined.

[7.] From the Exposure of the Dike in the Field midway between the
extreme Eastern and Western Ridges.

Lens. Similar to the preceding hand-specimens, but rather red-
dish in color, and somewhat more amygdaloidal. — Section. A much
fresher rock than those already described. The few porphyritic feld-
spars are generally plagioclase, and exhibit the same proof of an early
crystallization mentioned above (i. e. the feldspars of the groundmass
flow around them, etc.). The feldspars of the groundmass are principally
plagioclase, but some Carlsbad twins and unstriated crystals can be
found. All these feldspars are comparatively fresh, and the formation
of the greenish scales and other products of decomposition has not pro-
egressed far. The frequent inclusions of the original base, however, are
entirely altered to chloritic products and magnetite. The feldspars con-
tain occasional large rounded or irregular flnid inclusions, with bubbles,
and immense numbers of extremely small similar inclusions (requiring
the use of powers of from 700 to 900) characterized also by occasional
moving bubbles. Grains and crystals of epidote occur in the feldspars,
and occasionally quartz. Chloritic products and magnetite represent the
original base. Epidote occurs in the groundmass in patches ; calcite is
rare. True amygdules occur, filled with chlorite, quartz, and epidote.

[8.] From the Ridge constituting the extreme easterly Exposure of the Dike,
and not in Line with the Western Half, though trending parallel with it.

Lens. A reddish groundmass, containing feldspar crystals, amyg-
dules of greenish chlorite, and red spots resulting from the decomposi-

238 BULLETIN OF THE

tion of the rock. — Section. The least decomposed rock of any exam-
ined. It has a groundmass composed of small ledge-shaped feldspars,
magnetite, chlorite, epidote, etc., enclosing porphyritically a few large
feldspars. The majority of the crystals are plagioclase, but there is a
considerable number of Carlsbad twins. The small feldspars of the
groundmass show the flowing of the base around the large crystals, as
described previously. The larger feldspars contain very characteristic
inclusions of a base in irregular, reticulated, or cylindrical forms. They
often fill a large part of the crystal; may be zonally arranged ; and are
absolutely identical in shape and other characteristics with the inclu-
sions of glass or base in the unaltered basalts. These inclusions are now
altered to magnetite and greenish chloritic or viriditic products. Be-
sides these dark inclusions of base, the feldspars are filled with almost
colorless microliths and scales, —the products of the incipient decom-
position of the feldspathic substance, — and very minute fluid inclusions,
rounded, cylindrical, or branching. Some epidote and calcite occur in
the feldspars. True amygdules are found, filled with calcite, epidote,
and chlorite. Irregular masses of epidote occur as areas of alteration in
the groundmass, —the magnetite often in large masses, enclosing the
small feldspar crystals of the groundmass, and mixed with considerable
ferrite. One decomposed crystal may perhaps be referred to olivine.

[Q. 8'.] Zhe Large Dike running nearly at Right Angies across the Trend
of the Amygdaloid.

Lens. A coarse-grained, dark green rock, containing crystals of feld-
spar, pyrite, magnetite, and hornblende, in a dark green groundmass. —
Section. Contains (comparatively speaking) large-sized feldspar crystals ;
fibrous, greenish, dichroic hornblende ; crystals of magnetite and pyrite ;
decomposed crystals of olivine ; epidote ; and viridite, quartz, apatite,
etc. The feldspars are to a great extent kaolinized. The hornblende
occurs in irregular masses, shows strong dichroism and brilliant polar-
ization, and contains a great deal of epidote in rounded grains. Some
of the feldspar crystals lie imbedded in the hornblende, or cross it, just
as they do in the case of the augite of the less decomposed diabases, so
that this and the whole character of the hornblende indicate that it is
(in part at least) a product of the decomposition of the original augite.
The olivine occurs generally in shattered crystals, with the usual black-
ened border. The interior is altered to greenish serpentinous products ;
but little spots still show the polarization and other characteristics of

MUSEUM OF COMPARATIVE ZOOLOGY. 239

the unaltered olivine. The magnetite is found in extremely irregular
forms, while the pyrite grains often contain magnetite, and therefore
arise probably from its decomposition.

[Q. 1] One of the Narrow Dikes running parallel with the Trend of the
Amygdaloid.

Lens. A compact greenish rock containing crystals of feldspar. —
Section. Contains feldspar crystals, augite, magnetite, pyrite, and de-
composition products. The feldspars are kaolinized, or else decomposed
to white fibres, and contain considerable epidote, viridite, etc. The
augite occurs in irregular masses ; it is reddish and has well-marked
cleavage ; the decomposition to viridite, hornblende, and epidote is seen
to be well advanced, these substances forming along the cleavage lines.
The magnetite often shows the white decomposition characteristic of
menaccanite. The pyrite is probably derived from the magnetite. No
traces of olivine were seen.

[9.] Section of Two Pieces of the Greenish vein-like or irregular Masses
found in the Rock.

One of the fragments is composed of epidote, calcite, quartz, and an
opaque gray substance, perhaps kaolin, — mixed with the remains of
feldspar crystals. The other fragment, from one of the banded veins, is
composed of the same substances arranged in bands. Both are proba-
bly areas of decomposition in the rock.

Summary.

From the details given we obtain the following generalized description
of the amygdaloid proper. In the hand specimens the groundmass varies
in color from green, through gray, to red, — the last color characteristic
of the rock that is least decomposed. It sometimes encloses large green
or white feldspar crystals, often indented by the groundmass, or the feld-
spar crystals may be comparatively minute ; grains and crystals of epidote
are occasionally seen. The rock generally contains greenish spots of epi-
dote and of chloritic material, in part true amygdules, and spots of red-
dish decomposition. There are also amygdules of calcite and quartz.

The specimens from which the eight sections were made differ chiefly
in the degree of decomposition, the presence or absence of olivine, and
the coarse or fine texture. The specimens from the eastern end are much
less decomposed than those from the western end.

240 BULLETIN OF THE

As seen under the microscope, the rock is composed of large and small
feldspar crystals, magnetite, epidote, calcite, and a mass of chlorite,
viridite, and opacite. The large porphyritic feldspars are twinned plagio-
clase, and occasionally Carlsbad twins of sanidin. The minute feldspars
of the groundmass flow around them, encroach upon, and sometimes
break them. tarely, the groundmass, holding small feldspars, has
pushed into a crystal, a little distance on either side, and a tongue of
the (original) base, alone, without the small feldspars, passes through the
crystal and connects the two intrusions, — this connecting tongue now
altered, however, to calcite, chlorite, and epidote. The small feldspars,
when sufficiently fresh, show the triclinic twinning; but some Carlsbad
twins of sanidin and unstriated crystals occur, the former of which
cannot be referred to the plagioclase that, owing to the alteration, does
not show its multiple twinning.

The degree of decomposition that the feldspars have undergone varies
in the different sections: in the freshest rock they contain immense
quantities of minute fluid inclusions, characterized by moving bubbles,
and occasional larger ones, rounded or irregular in shape, together with
inclusions of the base. The latter are cylindrical, or irregularly reticu-
lated in form, often zonally arranged in the interior or exterior parts of
the crystal ; they are absolutely identical in shape, and in their relations
to the enclosing crystal, with the inclusions of glass or base of the fresh
basalts ; they are now altered to magnetite, viridite, and other products.
In the smaller feldspars these intrusions generally run through the
centre of the crystal, parallel with the twinning-plane. Even in the
freshest specimens, the substance of the feldspars is filled with minute
microliths, and scales either colorless or of a light greenish color, with
occasionally some epidote, calcite, or quartz, — generally products of the
decomposition of the feldspathic substance proper. In the more decom-
posed specimens these products multiply, so that the crystals become a
mass of these viriditic scales and fibres (often polarizing with the bril- -
liancy of talc, or in red and yellow colors), or even of opaque kaolin,
while calcite, epidote, quartz, and colorless needles with cross fracture,
in part apatite, appear to a greater or less extent. The epidote occurs
generally in the large feldspars in grains: some of it may originate
from the alteration of included minerals; but of this there is no proof.
Occasionally two feldspars interpenetrate each other.

The only other original mineral, unless it be part of the magnetite and
apatite, is olivine. This was found in well-marked, large, and undecom-
posed crystals only near the contact of the amygdaloid with the con-

MUSEUM OF COMPARATIVE ZOOLOGY. 241

glomerate (described with section [2]); though what seemed to be the
remains of olivine crystals were found in one or two other sections.
Their relations to the groundmass prove an anterior origin: some of the
magnetite and opacite in the sections have probably been derived from
the alteration of small fragments of olivine.

Between the large and small feldspar crystals lies a mass of greenish
alteration products, — chlorite (often dichroic), viridite, magnetite, opa-
cite, considerable epfdote, quartz, and calcite. When some of the large
feldspar crystals diverge, the triangular space between them is filled
with very small feldspar crystals, lying in this greenish mass ; showing,
as has been often remarked, that it is merely an original, glassy base,
much altered, for we find this same relation in the unaltered basalts.
Calcite, quartz, epidote, hornblende, biotite, apatite, etc., in the decom-
posed base, seem to belong to the more advanced state of decomposition.

Magnetite is always present. A large part of the magnetite arises
from the decomposition of the base, and it is generally difficult to say
what part of it is original. |

While in some sections true amygdules are wanting, yet they gener-
ally occur, characterized by their sharp boundary, and the arrangement
of the feldspars of the groundmass parallel to their outline. They are
filled by epidote, chlorite, viridite, calcite, or quartz; the epidote gener-
ally on the outside, when other minerals occur with it. Besides these true
amygdules, areas of decomposition occur in the groundmass, consisting
either of opaque ferritic material, constitutmg the macroscopical red
spots, or of epidote, chlorite, viridite, etc., enclosing the small feldspars.

Assuming that all the specimens described belong to the same rock-
mass, this rock, according to the classification used, would be referred
to both the Diabase and Melaphyr sections of the Basalts* (according to
the specimen examined), or again might be called a Diabase and Olivine-
diabase.t It is found by study to be a rock which, in the original state,
was composed of the feldspars, olivine, magnetite, a base (glassy, micro-
lithic, etc.), and probably some augite (though this cannot be identified
now), all in varying proportions, and that these original constituents
have been largely replaced by secondary products. It is therefore an
altered basalt, as has been previously shown by others for similar rocks
of this region.

* M. E. Wadsworth ‘‘ On the Classification of Rocks,” Bulletin Mus. Comp. Zodl.,
Mol<¥, No; 13.

+ Rosenbusch, Mikros. Phys. der Mass. Gest., etc.

+ M. E. Wadsworth, Proc. Bost. Soc. Nat. Hist., Vol. XIX. p. 217 e¢ seg., 1877.

E. R. Benton, Ibid., Vol, XX. p. 416 et seg., 1880.
VOL. VII. — NO. 7. 16

242 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.

The examination of the sections made from some of the narrow dikes
which cut the amygdaloid seems to show, in general, a similarity to
either [Q. 1’] or [6]—one series containing undecomposed augite, the
other none that can be identified. The great cross dike is described
under [Q. 8’]. Ali of these later eruptive rocks seem in a more advanced
stage of decomposition than the amygdaloid.

JULY, 1882.

No. 8. — On some Specimens of Permian Fossil Plants from Colo-
rado. By Lro LESQUEREUX.

Last February, Rev. Arthur Lakes, of Golden, wrote me that he had
found in South Park, near Fairplay, Colorado, a bed of shale with
beautiful insect remains mixed with a profusion of vegetable fragments
resembling the scales and seeds of Conifers, and with them some well-
defined forms, among others a small stem of Lepidodendron, showing
distinctly the scars and various small branches of Conifers, or Zamize, or
Lycopodiaceze. ‘ Those remains,” he said, ‘‘are in the Red-beds, on an
horizon appearing to us when examining the locality as Lower Triassic,
or Permian, or Carboniferous. A thin seam of coal was also discovered,
adjacent to the beds, and one tiny shell.”

Some time later Mr. Lakes sent me a box of specimens from the local-
ity mentioned above, asking me to determine them if possible, to report
to him what evidence on the age of the formation could be derived from
these vegetable remains, and to send the specimens to the Museum of
Comparative Zodlogy at Cambridge.

Though the specimens are very small, covered with mixed minute
fragments of leaves, scales, flowers, and seeds of Conifers, leaflets of Ferns,
etc., I was able to recognize, in all those which could be determined, the
characters of a Permian vegetation, and I reported to Mr. Lakes ac-
cordingly.

Being then about to publish the list of the determined species, with
some remarks upon them, Prof. Samuel Scudder, to whom the insects had
been sent, advised me that, from the characters of the animal remains,
his conclusions on the age of the formation did not fully agree with those
derived from the plants. As he was going to examine the locality
himself, he wrote me that he might perhaps find some more valuable
specimens, and that he would communicate them to me when returned
home.

These specimens, kindly communicated by Prof. Scudder, were re-
ceived two weeks ago. Though the vegetable remains preserved upon
them are quite as broken, mixed, and indistinct as those of Mr. Lakes, I
found a few of them whose determination added some new evidence to
that which had been procured already.

VOL. VII. — No. 8.

244 BULLETIN OF THE

The species which I consider as positively determined from all the
specimens are the following :—

1. Collection of the Museum of Comparative Zoilogy.

CALAMARI. — Sphenophyllwum Schlotheimii Br., an entire perfectly preserved ._
whorl. No. 1 of the collection.

Ferns. — Odontopteris obtusiloba Naum. Nos. 2 and 4.

Neuropteris Loschw Br., or Cyclopteris cordata Goepp. No. 6.

Fragment of an Alethopteris like A. lingulata Goepp. No. 7+.

Five specimens of fragments of small leaflets of Ferns, not determinable.
No. 18.

LycopopiacE&. — Leaves of Lepidodendron. No.9. The stem of Lepidoden-
dron recorded by Mr. Lakes, and rightly described by him in his letter,
was not found in the collection.

Conirers. — Seeds of Ullmannia selaginoides Gein., Leitpfl. No. 8.

Scales or involucres of Walchia ! lincarifolia? Goepp. No. 10.

Young leaves of Ullmannia Bronni Goepp. No. 11.

Leaves (detached) of UW. frumentaria Goepp. Very abundant, and mixed
with those of U. Bronnii. No. 12.

Leaves of U. selaginoides Gein. No. 13.

Branches bearing leaves of Walchia piniformis St. No. 14. Abundant
and variable.

Fragments, mostly ground nearly to powder, of leaves, flowers, and seeds of
Ullmannia Walchia, etc. Nos. 15 and 16.

Branch of Ullmannia Bronnit Goepp. No. 17.

2. Collection of Prof. Scudder.

CALAMARLA. — Sphenophyllum emarginatum Br. No. 9. Good specimen.
Fragment of rachis with a few leaves or Sphenophyllwm species, Gein., as
figured in Nachtr. zur Dyas, I., Pl. I. fig. 22.
Ferns. — Schizopteris species. Same as figured in Gein., Ibid., Pl. I. figs. 18,
18h) Nowé:
Sphenopteris Geinitzit Goepp. No.7. In many specimens.
Hymenophyllites Leuchartt Gein. No. 8.
Cyclopteris rarinervia Goepp. ‘No. 10.
Sphenopteris coriacea ? White & Font. No. 11.
Goniopteris Newberriana? White & Font. No. 12.
Pecopteris arborescens Brgt., in fruit. No. 13.
Cyatheites Beyricht Weiss. No. 14.
Callipteris conferta ! var. obliqua ? Weiss. No. 15.
Sphenopteris dentata ? White & Font. Nos. 15* and 16.
Small fragments of Ferns indeterminable. Nos. 17, 18.
Lycopopiacea. — Lepidophyllum species. Sporange and blade. No. 5.

MUSEUM OF COMPARATIVE ZOOLOGY. 245

Conrrers. — Leaves of Walchia longifolia Goepp. No, 20.

Leaves of Abietites Goepp. Fragments in many specimens. No. 21.

Leaves of Ullmannia frumentaria Goepp., and U. Bronnii, No. 1, abound.

Branches and leaves of Walchia piniformis, No. 3, in plenty of specimens.

Corpaitex. — Cordaites borassifolius Ung. Very fine specimen. No. 4.

Fragments of leaves of Cordaites species. No 22.

Cardiocarpus orbicularis Goepp. No. 24.

Cardiocarpus species nov., allied to C. gibberosus Gein. No. 25.

Carpolithes speciés, one referable to C. hwmidus Heer, the other, very
small but in plenty of specimens, to C. Geinitzi Heer, Perm. Pfl. of
Funkirchen, Pl. XXII. figs. 5, 6, 7, 8, and 13. These are all mixed
with ground fragments of scales, leaves, etc. of Walchia and Ullmannia,
No. 26. Same as No. 16 of the collection of the Museum of Comparative
Zoology.

On the above species of vegetable remains I add a few remarks in
regard to their evidence for the determination of the age of the forma-
tion where they have been found.

The genus Sphenophyllum ranges from the Silurian to the base of the
Permian, as far as known, at least, by the present state of our knowl-
edge in vegetable paleontology. Three species of the genus are recorded
by German authors, as from the Permian: Sphenophyllum Schlotheimi,
S. emarginatum, and S. longifolium. But all are from the lower strata
of the Old Red Sandstone, whose flora is so intimately connected by its
characters with that of the Upper Carboniferous that the exact limita-
tion between the formations has not been fixed. It is the same with
the Permo-Carboniferous strata of Virginia, wherefrom a number of spe-
cies of Sphenophyllum are described by White and Fontaine. Here we
are not yet in the true Permian. A very small and obscure fragment of
a Sphenophyllum species is described by Geinitz, Nachtr. zur Dyas, L,
. p. 10, Pl. I. figs. 22, 23. It is as yet the only trace of the genus in
the Middle Permian. The specific characters are not discernible, and
the author remarks that he has published it only because it is as yet the
only species of Sphenophyilum found in the Permian of Germany, The
presence of two species of this genus in the specimens of Fairplay would
be already sufficient authority for referring the formation to the paleo-
zoic time.

In the Ferns, the specimens represent Neuropteris Loschii, a species
found already in the whole thickness of the Carboniferous, and also in the
Permian of Europe. Pecopteris arborescens, Upper Carboniferous and
Lower Permian. Callipteris conferta, one of the more abundant species of
the Permian in Europe, and found until now on this continent only in

246 BULLETIN OF THE

the Permo-Carboniferous beds of Virginia. Odontopteris obtusiloba, Cy-
clopteris rarinervis, Odontopteris cordata which is scarcely distinguishable
from Neuropteris Loschit, Cyatheites Schlotheimii var. latifolia, Sphenopteris
Geinitr, Hymenophyllites Leuckarti, as well as a Schizopteris, are all Per-
mian species only. The other named species of Ferns are uncertain on
account of the insufficiency of specimens, but they are referable to types
of the Permian or Permo-Carboniferous.

In the Conifers, the most abundantly represented in the specimens
of Fairplay are the two more distinctly characteristic of the Permian,
Ullmannia frumentaria and Walchia piniformis. There are besides nu-
merous leaves and branches of Ulmannia Bronnit, and leaves of U. selagi-
noides, of Walchia longifolia, and of Abietites, species all representatives
of the same formation only.

In the Lycopodiaceze, Mr. Lakes has found a branch of Lepidodendron
which I have not seen among the specimens, but two of them have frag-
ments of leaves of this genus, and a Lepidophyllum with blade and spo-
range. It is well known that the Lycopodiacez disappear at the base of
the Trias, or rather in the Upper Permian. The same can be said of the
Cordaites, of which C. borassifolius is represented upon the largest frag-
ment of shale I have seen from Fairplay.

The age of a flora is indicated, not only by the presence of certain
types, but by the absence of others. And in this, the group of vegetable
remains in Fairplay is remarkably free of any fragments of plants char-
acterizing the Triassic period. There is no trace of Equisetacez or of
Cycadez. The fragments doubtfully referred to Cycas by Mr. Lakes in
his letter are all leaves of Ullmannia frumentaria and U. longifolia.
The Ferns are of a totally different character also. Prof. William Fon-
taine has prepared a memoir, descriptions, and figures of a large num-
ber of species of plants obtained from the so-called Triassic measures of
Virginia, which he considers as the equivalent of the Rhetic of Europe.
On these plants, Prof. Fontaine writes me that none of them could be
referred to the Permian, or to any of the species which I have recorded
from the specimens of Fairplay.

Possibly these Permian fossil remains will help to determine the geo-
logical distribution of the strata of South Park. In Dr. F. V. Hayden’s
Annual Report of 1873, Dr. A. C. Peale gives a section of the valley
from Platte River to Trout Creek, on a distance of six miles. The sec-
tion passes about five miles north of Fairplay. Its lower part, or beds
No. 18 to 50, represent an open series of 1,250 feet of strata, all hypo-
thetically referred by Dr. Peale to the Carboniferous or Permian, for no

MUSEUM OF COMPARATIVE ZOOLOGY. 247

fossils of any kind were found to prove it. Above this there is a covered
space (beds No. 51 and 52) of 1,300 to 1,500 feet, which is referred to
the Red-beds or Triassic. The whole is covered by a thickness of Jurassic
strata, overlaid by about 2,000 feet of Cretaceous. From this it appears
very probable that the remains of plants found by Rev. Mr. Lakes first,
and after him by Prof. Scudder, represent part of the first series of beds
No. 18 to 50, all exposed and as yet hypothetically referred by Dr.
Peale to the Carboniferous and the Permian. The exact location of the
plant-bearing beds in the section of Dr. Peale may probably be easily
determined.

OcToBER, 1882.

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No. 9.—On the Relations of the Triassic Traps and Sandstones of
the Eastern United States. By WitLIAM Morris Davis.

1. INTRODUCTORY.

LITERATURE.

3. OBseRVATIONS. Nomenclature. — A, Turner’s Falls. —B, Mount Tom. —C,
West Springfield, Mass. —D, Beckley Station. — E, Meriden, —F, Walling-
ford. —G, New Haven, Conn. — H, Fort Lee and Englewood. — J, Weehawken.
— K, Jersey City. — L, Paterson and Little Falls.— M, Feltville.—N, Mar-
tin’s Dock. — O. Point Pleasant Station. —P, Lambertville, N. J.

4, Brier STATEMENT OF FoRMER VIEWS.

5. GENERAL Discussion. Origin of the Triassic Estuaries and Cause of Trap Erup-
tions ; Origin and Deposition of the Strata ; Composition of the Trap; Relations
of the Trap and Sandstone; Review of Previous Ideas; Test-Characters for In-
truded and Overflow Sheets; Examples of these elsewhere; Dikes; Intrusions ;
Overflows; Amygdaloids; Effect of Trap on Sandstones; Tilting; Theories to
account for the Monoclinal Structure; Faults; Folds.

6. SuMMARY.

bo

1. INTRODUCTORY.

Since seeing in 1877 the trap conglomerate on the back of Mount
Tom, I have doubted the generally accepted explanation of the intrusive
origin of the Triassic traps, and inclined to Hitchcock’s theory of their
origin by overflow contemporaneous with the deposit of the sandstone.
During the past summer the desired opportunity came to examine the
question further, by personal observation, in Massachusetts, Connecticut,
and New Jersey, as detailed below, and with the result of satisfying my-
self that both views are correct; that some of the trap sheets are of
intrusive, and some of overflow origin. The Palisade range along the
Hudson may be taken as the type of the first, as has been shown by
Russell; Mount Tom in Massachusetts represents the second, as was
shown by Hitchcock. Other examples will be found below.

My endeavor has been to discover critical points that give decisive
evidence one way or the other as to the origin of the trap sheets, so as
to compel instead of merely allowing an explanation ; but observations
satisfactory or compulsory to one observer are not always so to another,
and I cannot, therefore, expect that what has convinced me will surely

VOL. VII. — NO. 9.

250 BULLETIN OF THE

be equally convincing to those who have thought differently ; but to
those who agree with my conclusions, as well as to those who differ from
them, I would quote the wish of the elder Silliman ; “TI take the liberty
to request, that those who may have it in their power will make precise
observations upon the appearances at the junctions, .... accompanied
by drawings and specimens when it is convenient; and at least with
accurate descriptions. We might thus be in a condition to form a
general opinion of the origin of our trap rocks.” *

2. LITERATURE.

A number of unimportant references to the Triassic rocks in Annual
Reports of State Surveys are omitted in the following list. These can
easily be found, if desired, by following Prime’s “Catalogue of Official
Reports,” etc., in the Trans. Amer. Inst. Mining Engineers, VII., 1879,
455. Papers referring only to fossils and date of the deposits are also
omitted, as the question of the age of the strata, for which the generally
accepted determination is adopted, does not now arise. References to
the articles cited are made in the text below simply by page number if
the author has but one title in the list; by letter and page number, if
several of his papers are given. Pages in parentheses after a title show
that only those pages of the paper are devoted to the Triassic formation.
Papers that have not been seen are marked with an asterisk.

Akerly, S.
The Geology of the Hudson River. New York, 1820, (25-39, 57-64), and

section.
Alger, F. See Jackson and Alger.
Bailey, L. W., and Matthew, G. F.

Preliminary Report on the Geology of Southern New Brunswick. Canada
Geol. Surv., 1870-71, (216-221).

Bailey, L. W., Matthew, G. F., and Ells, R. W.
Report on the Geology of Southern New Brunswick. Canada Geol. Surv.,
1878-79, (21-23 D), maps and sections.

Bailey, L. W., Matthew, G. F., and Hartt, C. F.
Observations on the Geology of Southern New Brunswick. Fredericton,
1865, (123-125), map and sections.

Barratt, J.
On the Evidence of Congelation in the New Red Sandstone. Assoc. Amer.
Geols. Proc., 1845, 26.

* Amer. Journ, Sci., XVII., 1830, 131.

MUSEUM OF COMPARATIVE ZOOLOGY. 251

Bradley, F. H.
On a “Geological Chart of the United States,” ete. A. J. S. [3], XII,

1876, (289).

Britton, N. L. j
On the Geology of Richmond County, New York. N.Y. Acad. Sci. Ann.,
II., 1881, (168-170), map and sections.

Canada.
Atlas to Geology of Canada. Montreal, 1863.

Chapin, A. B.
Junction of Trap and Sandstone ; Wallingford, Conn. A.J.S.{1], XXVII.,
1835, 104-112.

Cleaveland, P.
An Elementary Treatise on Mineralogy and Geology. 2d Edition. Boston,

1822, (746, 759).

Clemson, T. G.
Notice of a Geological Examination of the Country between Fredericksburg
and Winchester, in Virginia, including the Gold Region. Penn. Geol.
Soc. Trans., I., 1835, (311-313).

Cook, G. H.
a. Geological Survey of New Jersey. Map of the Triassic Formations.
- 1867.
b. Geology of New Jersey. Newark, 1868, (173-238, 336-339).
c. Geological Survey of New Jersey. Annual Report for 1879. Trenton,
1879, (18-35).
d. Geological Survey of New Jersey. Geological Map of New Jersey.
1881.

Cook, G. H., and Smock, J. C.
Geological Survey of New Jersey. Report on the Clay Deposits, etc.
Trenton, 1878, (170, 304-306).

Cooper, T.
On Volcanoes and Volcanic Substances, with a particular Reference to the
Origin of the Rocks of the Floetz Trap Formation. A. J.S. [1], IV.,
1822, (239-243).

Credner, H.
Geognostische Skizze der Umgegend von New York. Deutsch. Geol. Gesell.
Zft., XVIL., 1865, (392-394).

Dana, E. S.
a. Abstract of a Paper on the Trap Rocks of the Connecticut Valley. A.
J. S. [3], VIII, 1874, 390-392.
b. Trap Rocks of the Connecticut Valley. Amer. Assoc. Proc., 1874,
45-47,

252 BULLETIN OF THE

Dana, J. D.

a. Origin of the Grand Outline Features of the Earth. A. J.S. [2], III,
1847, (390-392).

6. Manual of Geology. Philadelphia, 1863, 1869, (21, 414-443).

c. The same. New York, 1876, 1880, (21, 403-423).

d. On the Geology of the New Haven Region, with special Reference to the
Origin of some of its Topographical Features. Conn. Acad. Trans., II.,
1871-73, (45-48).

e. On some Results of the Earth’s Contraction from Cooling ; Part IV.
Igneous Ejections, Volcanoes. A. J. S. [3], VI., 1873, (104-113).

f. Notes on Percival’s Observations on “ Indurated Bitumen” in the Con-
necticut Trap. A.J. S. [3], XVI., 1878, 180-132.

g. (On Russell’s “ Physical History,” etc.) A.J.8. [8], XVII. 1879,
328-330.

Dawson, J. W.
a. On the New Red Sandstone of Nova Scotia. Geol. Soc. Journ., IV.,
1848, 50-59, map and sections.
b. Additional Notes on the Red Sandstones of Nova Scotia. Geol. Soc.
Journ., VIII., 1852, 398-400.
c. On the Parallelism of the Rock Formations of Nova Scotia with those of
other Parts of America. Amer. Assoc. Proc., X., 1856, (20, 21).
d. Acadian Geology. Edinburgh, 1855, (60-115).
e. The same. London. 2d Edition. 1868, (86-124).
f. Notes on the Geology of Prince Edward Island in the Gulf of St. Law-
rence. Geol. Mag., IX., 1872, (203-205).
g. The Physical Geography of Prince Edward Island. Canad. Nat., VIL,
1872, 342, 343.
h. Supplement to the Second Edition-of Acadian Geology. London, 1878,
(28-30).
Dawson, J. W., and Harrington, B. J.
Report on the Geological Structure and Mineral Resources of Prince Ed-
ward Island. Montreal, 1871, (13-21).
Eaton, A.
a. An Index to the Geology of the Northern States. Leicester, 1818,
(31-35).
b. The same. 1820, (206-212, 215-221, 249-256).
c. A Geological Nomenclature for North America. Albany, 1828, (section).

Ells, R. W. See Bailey, Matthew, and Ells.

Emerson, B. K.
The Deerfield Dyke and its Minerals. A.J.S. [3], XXIV., 1882, (195, 196).

Emmons, E.
a. Notice of a Scientific Excursion (to Nova Scotia). A. J.S. [1], XXX,
1836, (834-338).

MUSEUM OF COMPARATIVE ZOOLOGY. 253

Emmons, E.

b. Agriculture of New York. Albany, 1846, I., (200, 201).

c. American Geology. Albany, 1854, (106-112).

d. Geological Report of the Midland Counties of North Carolina. New
York, 1856, (227-342), map and sections.

e. The Chemical Constitution of certain Members of the Chatham Series in
the Valley of Deep River, North Carolina. Amer. Assoc Proc., XII.,
1858, 230-232. , ,

Fontaine, W. M.
Notes on the Mesozoic Strata of Virginia. A.J.S.[3], XVII, 1879, 25-39,

151-157, 229-239.

Frazer, P., Jr.

a. Second Geological Survey of Pennsylvania. Report of Progress in the
District of York and Adams Counties, etc. Harrisburg, 1876, map and
sections.

b. The same. Report of Progress in the Counties of York, Adams, Cum-
berland, and Franklin. Harrisburg, 1877, map and sections.

c. The same. The Geology of Lancaster County. Harrisburg, 1880, with
a volume of maps. '

d, The Position of the American New Red Sandstone. Amer. Inst. Mining
Engr. Trans., V., 1877, 494-501.

e. Regarding some Mesozoic Ores. Amer. Phil. Soc. Proc., XVI. 1877,
651-655.

f. The Mesozoic Sandstones of the Atlantic Slope. Amer. Nat., 1879,
284-292.

Gesner, A.
A Geological Map of Nova Scotia, with an accompanying Memoir [1843].
Geol. Soc. Proc., IV., 1846, (190).

Gibson, J. B.
Observations on the Trap Rocks of the Connewago Hills,.... Pa. [1820].
Amer. Phil. Soc., II., 1825, 156-166.

Harrington, B. J. See Dawson and Harrington.
Hartt, C. F. See Bailey, Matthew, and Hartt.

Hawes, G. W.
a. The Trap Rocks of the Connecticut Valley. A.J. S. [3], IX., 1875,
185-192.
b. On the Mineralogical Composition of the Normal Mesozoic Diabase upon
the Atlantic Border. Washington Nat. Mus. Proc., 1881, 129-134.

Heinrich, O. J.
The Mésozoic Formation in Virginia. Amer. Inst. Mining Engr. Trans.,
VI., 1879, 227-274, map and sections.

254 BULLETIN OF THE

Hitchcock, E.

a. Remarks on the Geology and Mineralogy of aSection of Massachusetts,
on Connecticut River, with a Part of New Hampshire and Vermont.
A. J. 8. [1], I., 1818, 105-116, map and section.

5, A Sketch of the Geology, Mineralogy, and Scenery of the Regions con-
tiguous to the River Connecticut, with a Geological Map, ete. A.J. S.
[1], VI., 1823, (89-80), map and sections.

c. Miscellaneous Notices of Mineral Localities, with Geological Remarks,
A. J.S. [1], XIV., 1828, (227, 228).

d. Report on the Geology, Mineralogy, Botany, and Zodlogy of Massachu-
setts. Amberst, 1833, (206-241, 404-439), map and sections.

e. Final Report on the Geology of Massachusetts. Amberst, 1841, (199-
204, 434-531, 640-663), map and sections.

f. On the Trap Tufa or Volcanic Grit of the Connecticut Valley, etc. Assoc.
Amer. Geols. Proc., 1844, 10,11; A. J. S. [1], XLVII., 1844, 103, 104.

g. Description of several Sections measured across the Sandstone and Trap
of the Connecticut River Valley in Massachusetts. Amer. Assoc. Proc.,
IX., 1855, 225-227.

h. Ichnology of New England. <A Report on the Sandstone of the Con-
necticut Valley, especially its Fossil Footmarks. Boston, 1858, (5-28),
map and sections.

Jackson, C. T.

a. Nature of Minerals accompanying Trap Dykes which intercept various
Rocks. Assoc. Amer. Geols. Proc., 1845, (30, 31).

b. On the Coal Formation of Deep River, North Carolina. Boston Soe.
Nat. Hist. Proc., VI., 1856-59, 30-34.

Jackson, C. T., and Alger, F.

a. A Description of the Mineralogy and Geology of Part of Nova Scotia.
A. J.S. [1], XIV., 1828, 305-330 ; XV., (132-146), map and section.

b. Remarks on the Mineralogy and Geology of Nova Scotia, Amer. Acad.
Mem., I., 1833, (219-287), map and section.

Kerr, W. C.

a. Observations on the Mesozoic of North Carolina. Amer. Assoc. Proc.,
1874, 47-49.

b. Report on the Geological Survey of North Carolina. Raleigh, 1875,
(141-147), map and sections.

Leconte, J.
Elements of Geology. New York, 1878, (439-447).
wesleysjeuk-
a. Manual of Coal and its Topography. Philadelphia, 1856, (132, 133).
*b. United States Railroad and Mining Register, Philadelphia.
Lieber, O. M.
Reports on the Geognostic Survey of South Carolina. Columbia, 1860,
(19, 20), map.

MUSEUM OF COMPARATIVE ZOOLOGY. 255

Lyell, Sir C.

a, On the Fossil Footprints of Birds and Impressions of Rain-drops in the
Valley of the Connecticut. Geol. Soc. Proc., III., 1842, 793-796.

b. Travels in North America. London, 1845, (I. 12, 18, 124-126, 252-
256; II. 171, 172).

c. On the Structure and probable Age of the Coal Field of the James River,
near Richmond, Virginia. Geol. Soc, Journ., III., 1847, 261-280.

d. A Second Visit to the United States. New York, 1849, (I. 211-217).

e. On Fossil Rain-marks of the Recent, Triassic, and Carboniferous Periods.
Geol. Soc. Journ., VIL., 1851, 238-247.

Macfarlane, J.
The Coal Regions of America. New York, 1873, (505-528).
Maclure, W.

a. Observations on the Geology of the United States, explanatory of a
Geological Map. Amer. Phil. Soc. Trans., VI., (2), 1809, (417-421),
map.

b. On the Geology of the United States of North America, ete. Philadel-
phia, 1817, and Amer. Phil. Soc. Trans., I., 1818, (11, 12, 27-31, 63,
64, 66, etc.), with map.

Martin, B. N.

(On the Trapoid Rocks of the Palisades.) N.Y. Lyceum Proc., I., 1870-

71, 132, 133.
Mather, W. W.

Geology of New York. Part I., comprising Geology of the First Geological

District. Albany, 1843, (278-294), and sections.

Matthew, G. F. See Bailey and Matthew.

Mitchell, E.
Elements of Geology, with an Outline of the Geology of North Carolina..
1842, (36-39, 130-134).
Newberry, J. S.
Genesis of Sandstones. N. Y. Lyceum Proc., I., 1870-71, 131.

Olmsted, D.
a. Red Sandstone Formation of North Carolina. A. J. S. [1], IL, 1819,
175, 176.
*b. Report on the Geology of North Carolina. 1824, 1825,
c. [Review of b.] A. J.S. [1], XIV., 1828, (236). .
Peirce, J.
Account of the Geology, Mineralogy, Scenery, etc. of the Secondary Region
of New York and New Jersey, and the adjacent States. <A. J.S. [1],
II., 1819, 181-199.
Percival, J. G.
Report on the Geology of the State of Connecticut. New Haven, 1842,
(10, 11, 299-452), and map.

256 BULLETIN OF THE

Prime, F., Jr.
Second Geological Survey of Pennsylvania. Report of Progresson....
Lehigh County. Harrisburg, 1875, (4, D).
Rogers, H. D.
a. Report on the Geological Survey of the State of New Jersey. Phila- ~
delphia, 1836, (145-170).
b. Third Annual Report on the Geological Survey of the State of Pennsyl-
vania. Harrisburg, 1839, (18-23).
c. Description of the Geology of the State of New Jersey. Philadelphia,
1840, (114-171), map and sections.
d. (Oblique Deposition of the Triassic Strata.) Assoc. Amer. Geols. Proc.,
1842, 25.
e. (Origin of the Crescent Form of the Triassic Dykes.) A. J.S., XLV.,
1843, 333.
jf. Address. Assoc. Amer. Geols., 1844, (27-31).
g. The Geology of Pennsylvania. 1858, (II. 666-697, 759-765), map and
sections, *
Rogers, W. B.
a. Report of the Geological Reconnaissance of the State of Virginia. Phila-
delphia, 1826, (52-62), and section.
b. Report of the Progress of the Geological Survey of the State of Virginia
for 1839. Richmond, 1840, (69-83).
c. (Oblique Deposition of the Triassic Strata.) Assoc. Amer. Geols. Proc.,
1842, 26, 27, 28.
d, On the Age of the Coal Rocks of Eastern Virginia. Assoc. Amer. Geols.
Proc., 1843, 298-316.
e. On the Relations of the New Red Sandstone of the Connecticut Valley
and the Coal-bearing Rocks of Eastern Virginia and North Carolina.
Boston Soc. Nat. Hist. Proc., V., 1856, 14-18, 189, 190.

Russell, I. C.
a, On the Intrusive Nature of the Triassic Trap Sheets of New Jersey.
A. J.S. [3], XV., 1878, 277-280.
b. On the Occurrence of Solid Hydrocarbons in the Eruptive Rocks of New
Jersey. A. J.8. [3], XVI, 1878, 112-114.
c. The Physical History of the Triassic Formation in New Jersey and the
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Ann., IL., 1880, 27-80.
Schweitzer, P.
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23-25.
b. Analyses of Newark Sandstone. N. Y. Lyceum Proc., I., 1873, 136.
c. Analyses of Sandstones from New Jersey. N.Y. Lyceum Proc., L.,
1873, 196.

MUSEUM OF COMPARATIVE ZOOLOGY. 257

Schweitzer, P.
d. Notes on the Felsites of the Palisade Range. N. Y. Lyceum Proc., |.,

1873, 244-252,
Shepard, C. U.

On the supposed Tadpole-Nests, or Imprints made by the Batrachoides
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South Hadley, Mass. A. J.S. [2], XLIII., 1867, 99-104.

Silliman, B.

a. Sketch of the Mineralogy of the Town of New Haven. Conn. Acad.
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b. Mineralogical and Geological Observations on New Haven and its Vicin-
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c. Sketches of a Tour in the Counties of New Haven and Litchfield, in
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(202, 203, 231-233).

d. Tour between Hartford and Quebec. 2d Edition. New Haven, 1824,
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e. Igneous Origin of some Trap Rocks. A.J. S. [1], XVII., 1830, 119-132.

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On the Watercourses and the Alluvial and Rock Formations of the Con-
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Smock, J.C. See Cook and Smock.

Taylor, R. C.

a. Memoir of a Section passing through the Bituminous Coal Field near
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VOL. VII. —NO. 9. 17

258 BULLETIN OF THE

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River Palisades. N.Y. Lyceum Proc., I., 1870-71, 99-105.

3. OBSERVATIONS.

The following observations were made in the summer of 1882. The
attempt has been made in recording them to keep inference distinct
from observed fact, though the two may come in the same sentence.
The observations have been reduced as far as possible to graphic form,
for ease of reading as well as for the convenience of those who may care
to repeat them. It should be remembered that they are mostly the
work of short excursions, made with the object of discovering the posi-
tion and condition of the rocks only at certain points, and not with any
idea of preparing complete geological maps of a district. The plans are
generally traced from topographical or geological maps; none of the
sections are constructed accurately, but all are kept down near natural
proportions. In order to avoid too much assumption in these sec-
tions, all lines of contact not directly seen are drawn broken-dotted
(——-— ); the Hanging Hills section is an accidental exception to
this rule. The scales of maps and sections are only approximate. The
observations are referred to in the text farther on by the letters at
their headings.

Nomenclature. — The trap ranges are grouped according to Percival’s
method : the largest of a system is called the main range; lateral ranges
on the outcrop side or face of the main range are called anterior; on the
back or dip side, posterior. These lateral ranges are numbered accord-
ing to their distance from the main range. In the case of overflows,
these terms have the unforeseen advantage of serving to denote the rela-
tive dates of eruption.g Upper and lower contacts are between the trap
and the overlying and underlying sandstones. Dzke (except in quota-
tions) is restricted to masses of igneous rock clearly of later date than the
rocks they intersect, and with a greater extension across the layers of
sandstone than parallel to them. Sheet is applied to interbedded masses
of trap, of intrusive or of overflow origin. Sandstone is sometimes used

MUSEUM OF COMPARATIVE ZOOLOGY. 259

in a general sense, applying to the whole formation, and is then not
closely limited to its lithological meaning. Bearings are all magnetic.
Page references to previous writings are made in parentheses after the
author's name ; the titles are given in the list above.

A. Turner's Falls, Mass. (figs. 32, 33, 34).— This manufacturing
town is on a corner of land on the left bank of the Connecticut, which
here makes a considerable detour from its usual course, and on the way
exposes an excellent continuous section of sandstones and trap for more
than a mile. ‘This is best examined by beginning on the northwestern
bank, one eighth of a mile below the lower suspension bridge (A, fig. 32),
where the back of the main trap range is clearly seen. This range has
its beginning on the southwest flank of Mount Toby in Sunderland, in
a layer of trap making an inconspicuous ridge; Hitchcock has de-
scribed its upper contact with sandstone in a brook a mile and a half
southeast of Sunderland. It then advances northwest, and ascends on
the back of Deerfield Mountain, gaining the summit a few miles before
the Deerfield River cuts through the ridge to the Connecticut; two
railroads pass through this gorge and cut the trap, but do not, so far as
I could see in passing, show any contacts. East of Greenfield the Poet’s
Seat is the culminating point ; here the ridge is doubled, with a shallow
valley along its top, probably indicating a bed of sandstone or tufa, or a
strike fault. It is the upper surface of this main trap sheet that comes
to the river’s edge below Turner’s Falls (A, fig. 32); and going up
stream the bright red shaly sandstone is soon met lying upon its vesic-
ular, amygdaloidal surface, quite conformable to its slight irregularities,
and showing no signs of local baking at the junction, or of any branch-
ing intrusions from the trap below. The sandstone strikes N. 65° E.,
dips 35° 8. E. throughout the section. Following up the bank, we pass
obliquely across the strike of the sandstone, and just before coming to
the bridge reach the first posterior trap (B). The contact is unfortu-
nately hidden here; it might be found by searching on the face of this
posterior ridge farther northeast. The trap is at first dense, but a little
beyond the bridge becomes vesicular, and so continues up to the en-
trance of Fall River. Looking southwest across the river, one may see
an outcrop of rocks about in line with the strike of this trap, but they
seem to be bedded; no ridge is visible in that direction, and I believe
the trap ends about where the river crosses it. Going up stream the
trap is seen continuously except in two places where covered by sand-
stone: the first is in a little hollow on its back (C), about one third of
the way to the mouth of Fall River, where the bedding of the sandstone

260 ~ BULLETIN OF THE

is somewhat uneven, but not more so, I imagined, than would result
from the washing in of sand and mud to fill an irregular hollow; this
exposure is about twenty feet square ; the second is a much larger trian-
gular patch of sandstone (D) at the mouth of Fall River, giving excel-
lent contact specimens, very little weathered, retaining the usual texture,
softness and color of the sandstone directly to the trap surface, and
holding small scraps of trap clearly separated from the mass below (see
fig. 34). A wooden dam gives passage across Fall River near its
mouth, and directly opposite (S. E.) there is a small exposure of sand-
stone overlaid by trap breccia, with contact hidden. Farther up this
valley, by climbing up its steep southeast bank opposite a road bridge,
a larger exposure (E) is found some eighty feet over the stream. The
sandstone is gray and micaceous, and dips a little steeper than usual ;
its contact with the igneous rocks is hidden, but after a blank of say
five feet there is a bank of tufa containing fragments of hard trap. The
tufa is deeply weathered, so that I could get no good specimen with
fresh surface ; it shows parallel lines on its weathered front, which seem
to indicate bedding, as they were conformable with the sandstone strata
below. The trap fragments here are round or oval, not angular as by
the dam ; some are as much as two feet in diameter, with a hard, dense
surface, but vesicular within; they may be volcanic bombs. Twenty
to thirty feet will probably cover the thickness of this tufa bed; next
comes the dense trap of the second posterior range, well exposed at its
southern end in a rocky point on the river bank ; passing around this,
we come to the third exposure (F) of overlying sandstone, showing the
same features as the first. This trap also is not apparent as a ridge
farther southwest, but points to a sandstone island in the river, and
may, like the first posterior ridge, end about where the river cuts it.
From here up to the falls, one fourth of a mile, beds of shale, sandstone,
and conglomerate are well exposed in ascending section, but no more
trap appears. The close conformity of the trap and sandstone through-
out this series is noticeable.

This section is described and figured by Hitchcock (d, 423; e, 653,
here copied, fig. 7). Numerous specimens of foot-prints have been
found in the neighborhood. Emerson’s recent article on the Deerfield
Dyke and its minerals appeared after the above description was written :
it confirms the overflow origin of the trap, but speaks of only two trap
ridges, and regards these as originally one, now separated by a fault in
the Fall River valley. Ido not consider the evidence offered in favor
of this view as fully excluding the idea of separate overflows of limited

MUSEUM OF COMPARATIVE ZOOLOGY. 261

area, as above suggested ; although, so far as the origin of the trap is
concerned, it is immaterial whether the ridges are regarded as a single
sheet faulted or as separate sheets.

B. Mount Tom, Mass. (figs. 35, 36, 37). — This section is one of the
best I have seen. The following description is reversed from the de-
scending order in which the observations were made. The bench on
the western face of the mountain below the talus of trap fragments is
dependent on a hard sandstone conglomerate ; it forms a ridge by itself
from the southern end of Tom over two miles to Rock Valley, where it
dies away. The rock quarried at Mount Tom Station, Connecticut River
Railroad, seems to be of the same horizon. From this bench the sand-
stone is generally hidden by trap blocks; but about three quarters of a
mile north of the end of Mount Tom, there is a small exposure of sand-
stone in contact with the great trap cover; others doubtless occur, but
on finding this one I searched no farther. The sandstone here, a few
feet from the trap, is gray, micaceous, and clearly bedded ; but near and
at the contact it is dense, as hard as quartzite, bluish, and somewhat
like the trap itself in appearance, with only the larger bedding-joints
remaining. The two rocks are not welded together here: an open seam
separates them, so that no single specimen shows both. The trap is
dark, dense, fine-grained, and excessively hard; it lies evenly on the
layers below without cutting them; the columnar structure does not
show for some ten feet higher. Along the mountain summit the texture
of the rock is much coarser, the crystals are occasionally a tenth of an
inch in length. Descending the long eastern slope by a wood road, there
was no clear evidence of any persistent variation in form, such as occurs
by the Poet’s Seat in Greenfield, or on the back of the First Mountain,
south of Paterson, N. J. The entire mountain seems to be a single
heavy trap sheet, several hundred feet thick. When nearly at the
bottom of the valley, between the main and the posterior range, an
excellent series of exposures was found in a little gully leading down
the slope. First there was a glaciated surface of firm trap. Descend-
ing a little farther (ascending in the geological series), there was found
some forty feet of ragged, rough surface, in part trap, and in part clearly
a mixture of angular trap fragments with sandstone. The surface of
the trap is often vesicular, and in places shows included fragments of a
denser kind. The sandstone is reddish, not nearly so hard as that found
on the western face of Mount Tom, though harder than some of the soft
fragments of trap, which weather out leaving a rough framework of
sandstone; at some points the bedding can be seen, but exposures are

262 BULLETIN OF THE

generally too small and rusty for this. The trap fragments in the
sandstone vary from small grains up to pieces one to three inches in
diameter; some are dense, some vesicular. This locality is about one
fourth of a mile north of a strong gap in the posterior ridge, and is
marked by a five-foot boulder of light granite. Crossing the marshy
stream, a small outcrop of ordinary normal sandstone is seen on the
opposite slope ; similar outcrops are found one fourth of a mile farther
northeast, higher up on the face of the posterior ridge ; and finally, just
below its trap, several feet of well metamorphosed sandstone appear,
gray in color and quartzitic in texture. The trap here shows nothing
peculiar. Crossing over the ridge and descending a quarter of the way
to the river, we leave the trap and come to numerous outcrops of con-
glomeratic sandstone, darker in color than usual, and containing plen-
tiful scraps of trap, many of them vesicular, and in size up to three
inches. The first of these outcrops is not more than fifteen or twenty
feet over the trap; many others appear at a greater distance, even on
the railroad a little below Smith’s Ferry Station. It was there that
I first saw them in 1877, in company with Professor N. S. Shaler and
Mr. J. S. Diller.

The upper contact was not found among these outcrops, but it is
excellently shown in Delany’s Quarry, on the railroad and river bank,
not quite half-way from Smith’s Ferry to Holyoke. (From the quarry
to Holyoke Station is about an hour’s tiresome walk along the hot, sandy
track.) Here the rock is freshly worked, and the upper surface of the
trap is well shown to be very amygdaloidal, uneven, and knobby, as a
lava flow might be, and upon it lies the fine dull dark reddish muddy
shale, fitting closely to the trap and filling up its inequalities, so that
the sandstone a few feet higher is evenly bedded (see fig. 37). This
contact shale is as soft as ordinary shale at a distance from the trap ; it
is easily scratched to powder with a knife. On some trap faces patches
of similar shale appear to be included in the trap, but as they also are
not metamorphosed, I consider them to be muddy fillings of cavities
near the rough old lava surface, reached by passages not now exposed
to view ; where their bedding shows, it is about parallel to that of the
sandstone above. There was no appearance of branching intrusion into
the sandstone, or of breaking across its layers. I looked carefully at a
great number of freshly exposed amygdules here and elsewhere, in hopes
of finding some of them banded like those at Brighton, Mass. (see Bos-
ton Soc. Nat. Hist. Proc., XX., 1880, 426), but was always unsuccessful.
Ten or fifteen feet of sandstone over the trap are well shown in the

MUSEUM OF COMPARATIVE ZOOLOGY. 263

quarry. Several layers contain distinct fragments of trap, rather an-
gular in form, and variable in structure from dense to vesicular. These
layers are darker than the normal red sandstone, some being nearly
black, presumably on account of the trap sand they contain; some
might be mistaken for metamorphosed sandstone, as they have faint
bedding, and in a rough way resemble trap; but they grade into normal
reddish sandstone below as well as above, and this clearly shows that
their color is not due to metamorphic action. There is a strongly slick-
ensided joint at right angles to the dip in this quarry, with some evi-
dence of a fault of several feet throw.

Hitchcock wrote (e, 442) that a tufaceous conglomerate “ reposes on
the greenstone on the east side of Mounts Tom and Holyoke ; and con-
sists of a mixture of angular and rounded masses of trap and sandstone,
with a cement of the same materials. .... I do not doubt but the same
rock may be found on the east side of neatly all the greenstone ranges
in the Connecticut Valley. Its thickness is but small, and it graduates
‘on one side into greenstone, and on the other into sandstone.” This
evidently refers to a bed similar to those above described, and points to
the same conclusion. He refers to it again in the Ichnology (A, 17).
Lyell (a, 794) visited this region in his company, and concluded “that
there were eruptions of trap accompanied by upheaval and partial denu-
dation, during the deposition of the red sandstone.” Dana quoted Hitch-
cock’s results in 1863, and added, ‘‘But after an examination of the
region the author regards it more probable that the appearance of scoria
is owing to an escape of steam laterally from between the opened strata
during the ejection of the trap of the adjoining mountain.” (4, 430.)
Emerson’s observations, made recently (196), confirm Hitchcock’s and
those of the present writer. In his last edition of the Manual (1880),
Dana makes no mention of overflows.

C. West Springfield, Mass. (fig. 38).— About two miles west of this
station on the Boston and Albany Railroad, the track passes through a
short cut in the second posterior trap ridge near its end on the north
bank of the Westfield River, and fortunately reveals some twenty feet
of sandstone below the trap, as may be seen even from a passing train.
The natural outcrops in this neighborhood are very poor, as the ridge is
almost smothered in the high sand plain of the Connecticut River. The
main ridge and the first posterior are also very poorly shown as far as
critical outcrops are concerned, though the trap itself is well opened in
the city quarry by the railroad on the west face of the main ridge, where
distinct columnar structure is apparent. In the railroad cut, it is

264 BULLETIN OF THE :
noticeable that the hardness of the lower sandstone does not depend
entirely on its distance from the trap, but rather on its composition.
A sandstone stratum, some twenty-five feet below the contact, is red
and very hard; then comes some softer red shales; above these some
soft gray sheds and finally, next to the trap, sevens feet of hard red
sandstone. The strata strike N. 25° E.; dip 20°, E.S. E. The two
rocks here are very firmly welded tonather at their junction; the line
is slightly irregular, but its average conforms precisely with the bed-
ding. Within a foot of the contact, the sandstone is somewhat vesic-
ular; within an inch, its color changes to light gray, and in texture it
becomes a firm dense quartzite. The adjoining trap is dark and dense,
and but slightly amygdaloidal. The rest of the cut is all in trap, but
the rock is by no means of uniform structure. There is first a mass
from twenty-five to thirty feet thick (at right angles to dip), of which
the greater part is ordinary dense trap; but its upper six to eight feet
become very amygdaloidal and loose-textured, and the upper limiting
line, clearly seen on both sides of the cut, dips closely parallel to the
sandstone strata; near the bottom of the cut it exhibits some irregu-
larity. Over this, but separated by an open seam, comes a second mass
of dense trap, of about the same thickness as the first. This is not so
decidedly amygdaloidal as the first in its upper part, and is limited
above by a very even six-inch band of coarsely crystalline trap, dis-
tinctly visible on both sides of the cut. Ten feet higher, there is an-
other coarsely crystalline band, four inches thick, then say eight feet
of massive trap overlaid by drift; no upper sandstone could be found.
These even persistent bands dip parallel to the sandstone; they are
rather abruptly interpolated in the trap, and the whole is firmly welded
together. I do not feel satisfied with any suggestion yet presented in
explanation of them ; but there can be little doubt that the lower mass
with its amygdaloidal cover is a single lava flow, buried under later
eruptions. One can hardly imagine a clearer example of the kind. A
number of small faults can be seen on the sides of the cut, well marked
by a foot or so of brecciated trap ; the fault planes are all at right angles
to the dip of the sandstone; the largest throw was only a foot, with
uplift on the east.

I have been unable to connect the ridges here with the single poste-
rior range by Mount Tom, and cannot say how they are related to one
another.

D. Beckley, Conn. (fig. 39).—The several curved ridges shown on
Percival’s map (1, 2, 8, north end of E. ITI.) in the towns of Berlin and

MUSEUM OF COMPARATIVE ZOOLOGY. 265

Wethersfield, give clear explanation of the two causes that have produced
the crescentic outlines so characteristic of the trap. The first (1) is
shown to be a flat fold, a faint canoe-synclinal outcropping to the north
and west, by the close parallelism of the sandstone ledges around its
front ; their strike changes so gs™to run parallel to the trap bluff, and
they dip towards and under it On three sides. The trap shows a steep
face on the convex, and a long gentle slope on the concave side of its
crescent. It is undoubtedly a thin overflow sheet; for although no
contacts were seen, normal red sandstone was found three feet below
the trap, and red shaly sandstone fifteen feet above it, on a cross-road a
quarter of a mile southwest of Beckley Station ; and the trap is compact
at the bottom, and very loose and amygdaloidal on top. Evidently,
then, the sandstones and the trap have been here slightly folded to-
gether, and erosion has revealed their canoe-form precisely as it has
brought out the greater canoes of Medina Sandstone in Pennsylvania.
The eastern side of the canoe is not visible except at its northern end,
or bow as it may be called, because the fold is canted over on the east.
The fold as a whole has a gentle eastward dip.

The second curve (2) is made of trap much like that of the first, and
it is very probably the same trap sheet brought to the surface again by
a north and south fault with upthrow of forty or fifty feet on the east ;
its curve does not seem to depend on a fold, but simply on the cross
valley of the Mattabesic ; for a stream cutting through a monoclinal
ridge always produces such a retreat in the outcrop line of its deter-
mining hard stratum. The second and third crescents are therefore to
be regarded as parts of a single fold, cut into the imitation of a double
fold by the stream between them.

It becomes, therefore, an important matter to determine which of the
crescentic ridges shown in Percival’s and other maps are due to folding
of the trap sheets, and which to erosion without folding; E. I. and
E. Il. are undoubtedly folds ; so is the great curve of E. IV. that runs
_ up into Massachusetts. New Jersey shows several others. But the
peculiar forms of E. IV. 1, 2, 3, are chiefly, if not entirely, due to erosion,
as is shown under the next heading.

Percival gives a close description of the facts about Beckley (358),
but makes no statement of their cause.

E. Meriden, Conn. (figs. 40-43).— Two days’ walking about the
Hanging Hills and Lamentation Mountain failed to discover any con-
tacts, very probably on account of keeping mostly to the roads so as
to cover more ground, for the work here was chiefly stratigraphical.

266 BULLETIN OF THE

The main result found was that the Hanging Hills and the neighbor-
ing trap masses marked on Percival’s Map, E. IV. 1, 2, 3, 4, 5, and
probably 6, and others farther north, are all parts of a single trap sheet
of overflow origin, broadly and faintly folded into a very flat synclinal,
perhaps a little faulted, and deeply cut by erosion around the margin.
It is pretty surely an overflow, because it has small influence on the
sandstone when the two are seen near together, and its upper part is
very amygdaloidal; and because it makes part of the Mount Tom
range, whose overflow origin is well established. The former union of
the now separate hills is made sufficiently sure by the nearly uniform
height of the hills on the opposite sides of a gap (see section, fig. 41) ;
by the uniform slope in a single plane of the separated parts of the
sheet (fig. 40); by the conformity of this slope to the dip of the
adjoining sandstone, wherever seen; and by the regular position of
the first anterior ridge on the slope below the great bluffs. This is
not apparent from Percival’s description or map; on the latter, his
outlines indicate only the ridges or elevations, not the areas of trap.
Professor Dana’s reduced copy of this part of the map (c, 418) unites
the hills as here drawn, but he regards their trap as an intruded sheet
(d, 41). West Peak (E. IV. 3), the highest of the Hanging Hills, owes
its height over 2 and 4 to being at the southwestern end of the flat
synclinal; to the same structure is due the change in the direction of
the bluffs at this high point from a north and south to an east and west
line. E. IV. 5 is higher than 4 chiefly because it is farther from the
axis of the synclinal ; it is noteworthy that the oblique gaps between
3 and 4, 4 and 5, etc., are about parallel to this synclinal axis, and may
very probably indicate the position of subordinate bends or breaks.

I believe it probable and provable that Lamentation Mountain (E.
III. 5) is a reappearance by faulting of the Hanging Hills overflow sheet,
and it may extend even through E. III, II, and I, as is explained below
under faults and folds.

F. Wallingford, Conn. (fig. 45).—The sandstone in this neighbor-
hood is loose and coarse, with well-marked cross-bedding ; it is cut by
many dikes, as was first stated by Chapin in 1835, but there are also
several sheets nearly conformable to the bedding. The dikes are well
seen on the road to Cheshire, half a mile or more southwest of the
Wallingford Station (New Haven and Hartford Railroad), where they
break through the sandstone very irregularly: they are from five to
twenty feet thick, but do not affect the adjoining sandstone for more
than a few inches, Fig. 45 shows the ragged edge of one of them.

MUSEUM OF COMPARATIVE ZOOLOGY. 267

Besides the dikes, there are sheets of trap cutting the sandstone at
a small angle, or perhaps in places conformable to the bedding. One
of these begins close to the corner of the Middle Turnpike and the
Cheshire road, and can be easily followed several hundred feet obliquely
up the slope to the northwest ; it makes a little bench on the hillside,
rendered clearer by some quarrying work at several points; it is about
fifteen feet thick, dense throughout, and its columns are closely at
right angles to its bounding surfaces ; the sandstone is baked for a few
inches below it, and the only sandstone found on its back was hard-
ened. Another similar bench is seen a little higher; and a third makes
a well-formed mesa near by, locally known as Mount Tom. All of these
are probably intrusions ; but they have not’ the regular vertical position
shown in Chapin’s general section (see fig. 8). The trap here is more
irregularly intruded than at any other place I have visited.

G. New Haven, Conn. — There is a good exposure of sandstone on
the southwestern face of West Rock under the trap. The strata here
are of coarse granitic sand, and red and purple shales ; sometimes firm,
but with several purple shaly beds; they do not show so much meta-
morphism as the rocks beneath the Palisades, but nevertheless appear
to be distinctly changed from their original condition for several feet
from the trap, thus gaining a compact crystalline texture in certain
layers. The trap is fine at the base, where it is conformable to the
sandstone, and very compact through the whole mass: no amygdaloid
was seen at any point on the face or back.

The eastern slope near the southern end of the Rock is covered by
shaly sandstone for a considerable distance toward the top; it is often
exposed in little gullies, and shows a variety of colors from gray to
purple and bright brick-red. But for several hundred feet beyond the
uppermost exposure, no rock is seen till the firm trap appears ; at least
such is the case on the path leading up to the “ Judges’ Cave,” * and
along several gullies farther south. Undoubtedly a junction may be
found by searching farther to the north. In the covered space, several
fragments were found resembling baked shale; they are probably from
nearer the junction.

Pine and Mill Rocks are simply large dikes of compact trap, about
vertical, cutting across nearly horizontal granitic sandstones; a marked
consolidation has been produced by their heat for ten or twelve feet at
least from their sides. Their width and direction are variable: the

* A rude shelter under some boulders, where ‘‘Cromwell’s Judges” were cgn-
cealed for a time.

268 BULLETIN OF THE

former is certainly as much as two hundred feet at some points; and
their general trend is east. A rough but distinct columnar structure
is seen at right angles to the sides. Their junction with the sandstone
is somewhat irregular; but this is natural, as the latter has no well-
marked joint planes.

East Rock shows two patches of lower sandstone on its southwestern
face ; they are very similar to that described under West Rock, except
that about eight feet below the conformable junction, a spotted appear-
ance has been produced in a layer of purplish granitic sandstone. The
trap is also like that of West Rock. Ascending by the road on the
southern side of the hill, and when the eastern slope is reached turning
across a field into the wood, a very strongly baked granitic sandstone
is found within a few feet of the fine compact trap: the sandstone is
very dense and much more crystalline than any found elsewhere in
the Connecticut valley, but it rapidly loses this character, and becomes
soft and fragile farther down the hill, like that found on the back of
West Rock.

A number of dikes (fig. 44) may be found by crossing the river from
New Haven by Tomlinson Bridge, and continuing half a mile along
Forbes Avenue toward East Haven. These were long ago described by
Hitchcock (}, 56), but his figure (here copied, fig. 2) makes them much
too regular; they vary in strike and dip as well as in thickness, and
their sides are uneven. They are not at all amygdaloidal; their bak-
ing extends one or two feet into the adjoining granitoid sandstone.
The second cut on the Shore Line Railroad east of Fair Haven shows a
similar dike; but the third cut is in a coarse granitic sandstone that
makes a strong ridge by itself, being hard enough to stand up between
the softer shaly sandstones on either side, though not visibly aided by
any igneous rock. The ridge west of Saltonstall’s Lake (Percival’s
E. I.) is cut at a low gap by the same railroad, and shaly sandstones
are exposed, conformably covered by trap, and baked to white quartzite
immediately at the junction, as at West Springfield. The line of con-
tact is broken at one point by a very small fault, displacing the shales
and trap equally, and evidently of later date than the eruption. The
trap is brecciated at certain points, and is generally uneven in its joint-
ing, and its upper surface along the lake shore is very amygdaloidal.
No overlying sandstone could be found.

There is fairly good evidence that the natural gap, cut deeper by the
railroad, results from a transverse fault of ten or twenty feet, with the
throw eastward on the southern side.

MUSEUM OF COMPARATIVE ZOOLOGY. ; 269

Reference to Percival’s description of these ridges is given farther on.
Professor Dana gives a brief mention of the traps of this district (d, 46 ;
most of this article applies to the quaternary features of New Haven).
E. S. Dana and Hawes describe the composition of the trap here and
elsewhere, and note an increase in the hydration and alteration of the
eastern traps over the western. (See below, under Composition of
Trap.) All of the trap is regarded as intrusive by these authors.

From the descriptions given above, and a comparison of this region
with others, I am led to believe that the Saltonstall Ridge is an over-
flow : its small metamorphic effect at the base, its decided amygdaloidal
texture on the back or upper surface, its irregular and brecciated
structure, and its alteration and hydration, all agree with the characters
of overflow sheets rather than with those of well proven intrusions, such
as East Rock and the Palisades.

Palisade Range.— H. Fort Lee and Englewood, N. J. — Sandstone
shows at the water’s edge above and below the wharf at Fort Lee.
About eighty feet up the hill, under the Bluff Point House, a path cut-
ting shows baked shales seven feet from the trap.* A two-mile walk
northward from here leads one obliquely over the range toward Engle-
wood, showing many well-glaciated knobs of coarse, dense trap on the
way ; the glacial striz advance obliquely up the back of the range, bear-
ing 8. 20° E. A small stream known as Mill Brook, shown close to
Floraville, a mile south of Englewood on the Triassic Map of New Jersey
(Cook, a), gives a good exposure of the upper contact of sandstone on
trap.T

The trap is of rather coarse texture when first shown in the stream ;
it is evenly divided by parallel joints, one to three feet apart, dipping
12° W. N. W., just as the sandstone dips farther on; the columnar
structure is subordinate to this appearance of bedding. Following down
the stream-bed, the texture soon becomes finer, but is nowhere vesicular,
and in a short distance highly metamorphosed sandstones and shales are
reached. Their bedding is very even, and not perceptibly disturbed
near the trap; their color varies from nearly black to gray or greenish ;
in texture they are jaspery or distinctly crystalline. The junction was

* Contacts could certainly be found by further searching. The bluffs at Shady
Side Landing, a few miles down the river, and under Englewood Hotel, two miles up
stream, seemed worth visiting, as seen from a passing boat. Mather (282) gives
examples of contacts farther north ; some of his figures are here copied (figs. 11-14).

T Cook mentions sandstones overlying the trap at Englewood (8, 178, 208). I was
directed to Mill Brook, as a stream likely to show the desired contact, by Mr. J. H.
Serviss, of Englewood.

270 BULLETIN OF THE

found with difficulty, and only after passing over it many times, up and
down stream. It was at last discovered in a block, slightly moved from
its original position by frosting and stream-work, but still preserving its
joint faces parallel to those in the ledges near by. The ledge from
which this block had been loosened was covered; but as trap in place.
was found two feet below it, and baked sandstone in place three feet
ibove it, [ have no doubt that it showed the true place of junction. Its
weathered face showed no change of color, and very little change in tex-
ture, and specimens showing the actual welded contact were found only
after much hammering. They closely resemble those found at the
Wecehawken.tunnel at the under contact ; in both cases the igneous rock
is bluish black, dense, and fine, and for a quarter of an inch from the
contact is chilled to a dark gray ; and the aqueous rock is gray or dark,
and the more distinctly crystalline of the two. The thickness of the
Palisade Range trap between these contacts is, according to a true scale
section by Cook (6, 200), about seven hundred feet. Some twenty feet
of metamorphosed beds are seen farther down the brook; then expos-
ures are rare. A hard reddish-white sandstone was found farther south
lying say one hundred and fifty feet over the trap. No posterior ranges
of trap are known in this district, unless the Snake Hills back of Hoboken
are so called.

This excursion can easily be made in an afternoon from New York ;
going up the Hudson to Fort Lee by boat from Canal Street, and re-
turning from Walton Station, Northern Railroad of New Jersey, to the
Erie terminus. It is of value, as upper contacts are rare.

J. Weehawken, N. J. (fig. 46).— The several exposures of the sand-
stones below the trap in this district have been fully described by
Russell (d); some of his figures are here copied (figs. 30, 31), and a
more detailed view of the junction at the point of rocks below the
Duel Ground* is added (fig. 46). H. Credner examined the Palisade
trap in 1865, and pronounced it intrusive ; he regarded the Snake Hills
as a branch from the main “ emporbrechende Dioritmasse” (393).

It is very probable that the advance of the Weehawken cliffs to the
river bank at this point is due in part to the resistance to erosion offered
by the chimney or dike of trap, which here descends close to the water’s
edge, while elsewhere the trap generally rests on a sandstone base, thirty
to one hundred feet above the river; but it is also quite possible that a
fault, similar to that seen at Garret Rock, Paterson (L), has aided the
advance. The intersection of the sandy and shaly layers by the dense

* The Hamilton-Burr duel ground of 1804.

MUSEUM OF COMPARATIVE ZOOLOGY. 271

trap, and their metamorphism, are excellently shown. The branch dike
cannot be traced quite to the greater mass, but they undoubtedly join
below the talus; the branch is about four feet thick, generally lying
evenly between the layers, but at one point crossing them in an irregu-
lar, ragged passage ; it is clearly traced two hundred feet horizontally ;
and where it is lost to sight the main trap mass of the high cliffs above
has risen nearly half this distance over it. All the bedded rocks here
are thoroughly baked, and near the junctions are more or less clearly
crystallized ; their color varies from light gray to black, but there are
no red beds; the beds above the branch dike are affected quite as
stongly as those below it.

Half a mile farther north, where the tunnel of the West Shore road
(New York, Lake Ontario, and Western Railroad) opens on Day’s Point,
another contact was found. Here the fine dense trap lay evenly on the
baked and crystallized layers below it, of which some eight feet were
shown ; their color was dark or black, not red. This contact will prob-
ably be covered by later work. Day’s Point, a low triangular projection
into the Hudson, where the wharves of the West Shore Railroad are in
process of construction, now shows a small ledge of sandstone, rapidly
being cut away in the work of grading. It is separated from the trap
by eighty or one hundred feet of sandstone, measured at right angles to
the dip of 12°. The upper layers of the ledge are firm, fine-grained, and
red ; the lower are looser, clear white, with some coarser grains of trans-
parent quartz. Similar white sandstone occurs under the cliffs a third
of a mile southwest of the Duel Ground.

K. Jersey City, N. J.— The recent work of straightening the old cut
on the Pennsylvania Railroad gives an excellent section with many fresh
exposures through this lower part of the Palisade Range. The trap is
generally coarse ; in some small patches there were crystals of pyroxene
half to three quarters of an inch in length. It was nowhere found to be
the least vesicular. Broad joint faces are very common, and faulting
has taken place on some of them. Near the eastern end of the cut
there is a vein or dike, six inches wide, vertical, trending about north
and south, in the trap. It is light gray in color and is composed of a
fine granitoid mixture. Its texture is uniform throughout, and the
trap shows no change of structure on approaching it. I have found no
other example of the kind.

Both Cook (b, 216) and Russell (d, 43) give evidence to show the
existence of a soft bed, probably of sandstone, between the eastern and
western part ofthe trap. Its place in the cut is marked by an open hollow

272 BULLETIN OF THE

in which no rock is now to be seen, and it is not fully proven not to be
a fault like that at Garret Rock, Paterson. There is a longitudinal
valley on top of the Palisade Range at Fort Lee, but coarse trap is seen
so plentifully on its two slopes that there is little room for sandstone at
the bottom; and its cause is very probably a fault. Cook also notes
that the trap of the Palisades is remarkably uniform and very hard
(b, 178).

L. Paterson and Lnttle Falls, N. J. (figs. 47, 48). — First and Second
Mountains * are here cut through by the Passaic. The flat country
back of the broad gap and the considerable quantity of drift in the
neighborhood indicate that the present course of the river is not its
course during preglacial times of greater land elevation. We cannot,
therefore, now see the old valley bottoms, so that here, as on most of
the Palisade Range, the back of the trap is stripped of its sandstone
cover below the present general surface of the valley drift, and upper
contacts cannot be found. In spite of the deep river gorges, and the
large areas of trap exposure, I was unable, in searching a day and a half
in this district, to find any sandstone lying on the trap; but lower con-
tacts are seen at several points. The best of these is in the gorge below
the Passaic Falls at Paterson: on the left bank the exposure is ina
high bluff, not easily reached ; on the right the trap is quarried for pav-
ing-blocks, and a fresh contact constantly shown and easily accessible
(fig. 48).

There are red strata of firm sandstone and thin-bedded shale cut
below the trap, and up to a few feet of the junction they show no marks
of alteration ; both can be matched closely at many points distant from
any igneous rock. Within a foot of the contact the sandstone becomes
firmer than usual, and shows rusty cavities, presumably a metamorphic
effect, as they are most numerous by the trap. The upper half-inch of
sandstone is darker than the rest but still reddish. The line of junction
is easily found and traced; it is parallel to the sandstone layers, and
nowhere cuts across them; the slight waving irregularity that it shows
does not demand intrusion for its explanation. Specimens are easily
broken out showing the two rocks welded together. The mass of the
trap in the gorge is dark, fine, and even in texture; farther back from
the sandstone it becomes coarser, but no samples were found so coarse
as those from the Jersey City cut or from Goat Hill on the Delaware.
Close to the junction, amygdaloidal cavities are very plenty ; but most
of them are within a foot or even half a foot of it, and here the trap is

* Called the Watchung Mountains in Cook’s later Reports.

MUSEUM OF COMPARATIVE ZOOLOGY. 213

very fine-grained. The lower ten or fifteen feet of trap is of very heavy
columns, two to four feet on a side, irregular or roughly rectangular ;
divided near the middle by rather continuous joints parallel to the sand-
stone bedding, sometimes breaking the rock into slabs two to ten inches
thick. No change of texture is seen at these joints, and some of the
columns are continued above and below. The heavy columns suddenly
change upwards to smaller ones, six inches to a foot on a side, but there
is no corresponding ‘change in the texture of the rock, nor is there any
appearance of a seam between the two parts; it is simply a change of
jointing, for which I can suggest no satisfactory cause. The smaller
columns are not all parallel, but incline in various directions ; some
variation is shown in the figure where they overhang the lower columns.
Where thus irregular in position, they are at right angles to the present
surface of the ground (noted also by Cook, }, 202, 203). The same
change of structure is shown a third of a mile south, by Barber’s Mills ;
again a little farther where the Delaware, Lackawanna, and Western
Railroad cuts a bench for its passage around the end of First Mountain,
here known as Garret Rock; and finally in the first and third of three
quarries opened on the eastern face of the mountain, over the railroad
station. Contacts of trap and sandstone show in all but the first of
these, but not so clearly as at the Falls; the sandstone shows no effect
of heat except the slight one above described. Of these latter localities
the most important is that on the railroad (fig. 47), showing two strike
faults of small throw. The eastern and greater of the two is covered by
a ravine and its rubbish, but is proved by the repetition of shaly sand-
stone, heavy columns, and smaller columns on either side ; from junction
to junction measured along the track is one hundred and sixty paces,
say four hundred and fifty feet ; the junction line dips with the bedding
10°; this gives seventy or eighty feet for the displacement, with down-
throw on the east. The second fault, a little farther west in the same
cut, is shown to be about eight feet by the displacement of the upper
surface of the heavy columns with downthrow to west; the fault is on
an open joint, parallel to the columns, and striking with the ridge.

The mountain is most easily ascended by its northwest flank ; from
any of its higher knobs* a well-marked longitudinal valley is seen sep-
arating the eastern from the western summits; it extends several miles
with varying distinctness, and is very marked at the Notch, where the

* Most of these knobs are well rounded by glacial action, and same still retain
strie pointing directly up hill. Excellent scratches on the trap at Little Falls point
up into Vernon Valley between the two mountains.

VOL. VII. — NO. 9. 18

274 BULLETIN OF THE

Greenwood Lake Railroad crosses the mountain. As the valley is in
line with the larger fault, they probably stand in the relation of effect
and cause; the throw has very probably increased where the valley is
well formed.

Sandstone was not found in the valley as far south as the Notch,
although the place is favorable for its preservation. If continued north-
ward, the fault would pass east of the trap front at the Falls, and its
effect, if existing there in the sandstone, would be less noticeable.

On the western foot of First Mountain two small exposures just west
of the Morris Canal and south of the High Bridge showed amygdaloidal
trap, and one of them presented clear marks of variation in structure
bounded by curved surfaces, such as are found farther south at Felt-
ville. There was also seen at this point a surface much like that of
flowing lava or slag.

Sandstone is not seen in the flat valley until the village of Little Falls
is reached, a short mile west of the First Mountain trap, where it is
shown in normal condition in a quarry by the canal and river, about
two hundred yards east of the Second Mountain trap. The right bank
of the Passaic here approached gives no chance of finding a junction ;
but on the other side, a little farther down than opposite the quarry,
there is a small opening in which fine trap and red sandstone both show,
though the contact is hidden by several feet of rubbish. The sand-
stone has no marks of baking. Following up stream, the trap varies
greatly in texture; an irregular very amygdaloidal mass grades into
firm trap on one side, and into a much decomposed loose rock on the
other ; I have considered the latter an ash or tuff. The dense trap is
often distinctly columnar, and above the canal bridge it is well divided
by nearly horizontal open joints into sheets of varying thickness. In
the midst of this there is a very uneven mass of amygdaloidal trap that
seems to contain fragments. Farther west there is a broad area of flat
alluvial meadow-land.

The trap of this region is described by Rogers (c, 146) and Cook
(6; 179):

M. Feltville, NV. J. (figs. 49, 50).— Mr. I. C. Russell (a) describes an
upper contact in a little ravine on the back of First Mountain near this
deserted village; but I failed to discover any outcrops corresponding
closely to his description. My time there was short, and allowed only
the examination of a ravine about an eighth of a mile east-northeast of
the village ; ‘the stream from it enters the brook in Washington Valley
at the lower part of an old broken dam. Going about one hundred yards

MUSEUM OF COMPARATIVE ZOOLOGY. 275

from the mouth, so as to descend (geologically) below the trap surface,
the rock appears firm and hard in the stream bed: shaly sandstone
often outcrops on the banks of the ravine, but at no point within five
feet of the trap, and generally ten or fifteen feet from it. Returning
down stream, the trap becomes amygdaloidal, and shows rounded
bosses or knobs similar to those described by Russell ; but as seen here
they are not directly at the upper surface of the trap. Nearly at the
entrance of the ravine, a bank of much-weathered vesicular and frag-
mental trap suggests a trap breccia, but the surface is too much rusted
for determination. The most important exposure here was found in the
side of a short adit made some years ago on a small vein in the trap ; it
is known in the district as the “Copper Mine.” It shows (fig. 49) a
number of oval masses of trap, up to two feet or more in diameter, con-
tained in a peculiar red and black matrix. The trap masses vary in
their texture and color with the distance from their surface ; the outer
part is black and dense, then amygdaloidal for a few inches with con-
centric bands of color, and rather dense near the centre. The matrix
(fig. 50 a, b) has all the appearance of being a disorderly mixture of
small, angular scraps of trap, up to an inch long, held in a soft reddish
shaly mass, that shows no signs whatever of metamorphism. Its con-
trast with the over-lying sandstones at Englewood is very marked, and
it is difficult to understand how this could have been formed except on
the surface of a pre-existent sheet of lava.

Russell says (a, 280), “‘ The section at Feltville furnishes indisputable
evidence that the igneous rocks composing the first Newark Mount&in
were intruded in a molten state between the layers of the stratified
rocks subsequent to their consolidation.” He describes (b) another
upper surface of the trap on the back of the same mountain farther
south, back of Plainfield, where there is “an amygdaloidal trap passing
into a metamorphosed shale,” so that it is frequently difficult to detect the
difference between the two rocks. I was unable to visit this point.

Feltville can be reached by a pleasant walk of four miles from Fan-
wood Station, Central Railroad of New Jersey ; the Triassic Map of New
Jersey, 1867, gives the roads very clearly. It is to be hoped that further
observations will soon be made to give evidence for one or the other of
the above discordant conclusions. At Fanwood Station, the railroad
cuts the unstratified terminal moraine of the quaternary ice sheet (New
Jersey Geol. Survey, Annual Reports, 1877, 10; 1878, 16); and good
specimens of foreign angular and scratched stones, large and small, are
easily found.

276 BULLETIN OF THE

N. Martins Dock, N. J. (fig. 51).— Two beds of trap appear in the
shales a little above Martin’s Dock on the north (left) bank of the
Raritan River about two miles below New Brunswick ; they are there-
fore about three miles posterior to Palisades — Rocky Hill trap range,
which if continuous is here buried under the cretaceous formation. The -
lower bed is about fifteen feet, the upper two feet thick, and they are
separated by some ten inches of slate; the two are closely parallel to
each other and to the strata of shale and sandstone below and above,
and all dip ten to twelve degrees westerly; there is no appearance
whatever of the traps cutting across the shaly layers that enclose them.
The section may be described as follows, beginning at the bottom.

Soft, fragile shales, generally red in color, appear along the shore for
several hundred feet down stream: occasionally they vary to a fine,
sandy layer, six to twelve inches thick, with rather irregular layers, as
if disturbed, although the shale below and above is very evenly bedded.
Approaching the trap, three to five feet below it, the shale is grayish,
but still soft and fissile ; for six or eight inches below the trap, the shale
becomes slaty, dark, tending to bluish black, and hard; but in places
two or three inches under the junction occur loose, soft, weathered
patches quite unlike the firm, dark shale enclosing them. The trap
and shale are not welded together; all the junctions are separated by
open joints, so that no specimen showing the two rocks together could
be obtained. The lower heavy trap layer is firm, dense, dark through-
out with finer texture at both junctions, and no appearance of vesicular
structure ; it breaks into rough columnar blocks, and where these are
weathered on the shore, they often have the ragged look of a breccia,
but no such structure could be found in the rock in place. The inter-
mediate stratum is a hard black ringing slate: in places it shows a
slight breaking and disarrangement of its layers, not by cross-faulting or
any general disturbance, but more as if kneaded together. The upper
trap layer is dark and dense, like the lower. Above it the rock is very
rusty from weathering, and shows an open, loose texture for some six
inches ; the rusty color continues for several feet, and about ten feet
from the trap there are normal soft red shales again.

These trap-sheets must be intrusive, although they show less baking
than similar sheets on the Delaware. Cook says (b, 202), speaking of
the bedded appearance of the trap here and elsewhere, “So strongly
marked are these divisional planes, and so closely do they resemble
marks of stratification and even lamination, that good observers are
frequently unable to tell which is trap and which is only discolored

MUSEUM OF COMPARATIVE ZOOLOGY. Bet

shale.” He includes this with the general occurrences of intrusive
trap.

O. Point Pleasant Station, Belvidere Railroad, N. J. (fig. 52). — The
main mass of trap here seems to be a small example of what is shown
on a larger scale farther down the Delaware about Lambertville, but
the smaller sheets resemble most the little outcrops at Martin’s Dock,
and are finely shpwn.

The first outcrops on the railroad are about five hundred feet below
the station, where a dark, fine grained trap shows in the bank; it is
faintly columnar, but clearly bed-jointed, so that the slabs dip 12° N.
20° W.; the sandstone wherever seen is closely of the same position.
There are no amygdules, but on some weathered surfaces the trap is
pitted in lines parallel to the bed-joints, showing points of chemical
weakness probably determined early in its history. The rock rapidly
becomes coarse-grained and light-colored on going northward, and in
this form rises to the hill-top ; on the slope where seen, it is not colum-
nar, but breaks out in large masses and slabs; it becomes somewhat
finer again, but I failed to find its northern limit, which occurs in a
ravine. North a little farther and opposite the station is a bed of fine-
grained dark trap, again showing distinct bed-joints and little cavities
weathered in lines parallel to its lower surface; there is no apparent
change of structure to cause them. This trap rests on a fine, brittle
black slate ; the junction of the two rocks is seen with few interruptions
for a hundred feet, and is precisely conformable to the bedding. The
upper surface of the trap was not seen; but judging by the form of the
bank, the bed is not more than twenty feet thick.

A little above the station there is a cliff, thirty to fifty feet high, of
fine black trap ; its face is marked by joints a little steeper than a nor-
mal to the dip, and dividing the rock into sharp-edged columns (9) ;
there are other joints parallel to the bedding of the adjacent sandstone ;
and two four-inch bands of the same dip were traced some forty feet
along the face, distinguished from the rest by a peculiar roughness of
weathered surface dependent upon short cracks occupied by calcite.
This may be called a kind of vesicular structure, but not at all like the
ordinary trap amygdaloid. No contacts of this trap with slates were
seen, but the slate where found above and below was fine, black, and
brittle, and dipped 12° parallel to the bed-joints in the trap.

An eighth of a mile above the station, a dry stream bed gives a
good series of exposures to a height of more than two hundred feet over
the river. Much the greater part is on fine black shale or slate, or

278 BULLETIN OF THE

brownish shale of somewhat coarser texture; near the several trap
sheets, it is always black and brittle. Mud-cracks were noticed on
many loose slabs, and occasionally in place here and farther up the
river. Four beds of fine black trap occur in this little ravine: the first
two form a single shelf over which a fine thread of water falls (fig. 52),
the lower bed being four feet thick, the upper twelve, with four to
six inches of shaly slate between them. ‘This parting of slate is seen
between the two beds of trap, extending with uniform dip for seventy
feet. The slate and trap are very much alike on fresh surfaces, but the
slate has a bluish tinge, and shows some signs of breaking on its bed-
ding; the trap is blacker, and its fracture is more conchoidal. Both
are jointed into sharp-edged columns, but these are most distinct in the
trap. Farther from the trap, the shaly structure is more apparent,
and bands of lighter and darker color are sometimes found. The other
two trap sheets make two small benches farther up the ravine, and
show about the same characters as those just given, but their junctions
with the slate could not be determined, so nearly alike were the tex-
tures of the two rocks near their contact, and so closely did joints in
the trap imitate beds in the slate. Weathered fragments of trap often
showed a pitted or scoriaceous surface, though no cause could be seen
for this in the structure.

Returning to the railroad, and going north again, the same trap
sheets are passed as they descend to cross the river. A quarter of a
mile above the station, dark red sandstone appears in the bank, and
continues without further interruption ; it is fine and hard, though not
at all quartzitic ; generally thick-bedded, but sometimes shaly and mud-
cracked ; fine green dots of epidote (?) are found in it. It is very
evident that the brittle black slate that adjoins the trap was never like
this sandstone.

Rogers (c, 156) and Cook (6, 192) both refer briefly to this locality.
The trap here is shown on the Triassic Map of 1867, but not on the
Economic Map of 1881 (Cook, « and d).

P. Lambertville, N. J. —The section along the Delaware by Lam-
bertville is spoken of by H. D. Rogers (c, 153; g, 685) as affording -
good examples of the metamorphic effect of the trap on the sandstone
on both sides of the igneous mass. Cook shows the same region in a
generalized section (a, sec. 1, here copied, fig. 26), with the traps lying
between the sandstones after the manner of sheets elsewhere. The
region is one of difficult study, for, in spite of the deep valley cut by
the Delaware, outcrops are not continuous enough to show junctions ;

MUSEUM OF COMPARATIVE ZOOLOGY. 279

it seems hopeless to look for them here, and I was unable to get good
evidence as to the position of the trap. It is surely intrusive, as no
amygdaloid is present, and the shales are baked on both sides of the
trap ridges; but whether interbedded or in dike form, is rather an
open question. Against the sheet form may be noted the small dif-
ference in slope of the two sides of Sourland Mountain, and conse-
quently the absence of a well-marked face and back so characteristic
of the sheets elsewhere; and the fact that the baked and blackened
shale ascends to about the same height on either slope (Cook, 5, 191).
Farther southeast, the several elevations known as Rocky Hill, Penning-
ton Mountain, and Bald Pate are on the other hand probably sheets,
as their southern face is steeper than the northern: as suggested by
Russell, these are presumably the reappearance of the Palisade curve,
which is covered by the cretaceous strata in its middle ; its length from
Haverstraw on the Hudson to Bald Pate on the Delaware would then
be over eighty miles.

4, BRIEF STATEMENT OF FORMER VIEWS.

The following paragraphs show in brief the opinions of various writers
on this subject, the districts of their observations, and the dates of their
publications.

It was thought that the trap was intrusive by Silliman (Conn., 1810,
1830), Hitchcock (Mass., Conn., 1818), Chapin (Conn., 1835), Gesner
(Nova Scotia, 1846), Lyell (Va., 1847), Emmons (N. Y., 1846, N. C.,
1858), Cook (N. J., 1868), E. S. Dana and Hawes (Conn., 1874), Kerr
(N. C., 1875), Prime (Pa., 1875), and Frazer (Pa., 1876). These authors
make no special reference to the effect of the eruptions on the position
of the sandstone strata in their writings of the above dates. It was
held that the intrusion of the trap tilted the sandstones by A. Smith
(Conn., 1832), Percival (Conn., 1842), Emmons (1854), and in part by
Silliman Jr. (Conn., 1842) and Hitchcock (Mass., 1844).

The following considered the trap intrusive, but held that the dip of
the sandstone was due to some other disturbing force: Jackson and
Alger (Nova Scotia, 1833), H. D. Rogers, (N. J., 1836), Hitchcock in
part (Mass., 1844), Credner (N. J., 1865), J. D. Dana (Conn., 1863-
1880), Heinrich (Va., 1878), and Russell (N. J., 1875-1880).

The overflow origin of the trap was faintly suggested by Gibson (Pa.,
1820) and Cooper (N. J., 1822); it was shown to be probable by
Hitchcock in 1833, and proved later (Mass., 1841-1858) ; Dawson came

280 BULLETIN OF THE

to the same conclusion (Nova Scotia, 1848-1868) ; it was adopted by
Lyell in part (Mass., 1842), and fully by Leconte (1878) and Walling
(Mass., 1878). These authors agreed with those of the preceding group
in believing that the tilting of the sandstones was the effect of some
external force.

The trap was considered passively intrusive, and the dip of the sand-
stone was looked on as the result of original oblique deposition, by H. D.
Rogers (Pa., N. J., 1839), W. B. Rogers (Va., 1840), Mather (N. Y.,
1843), Silliman Jr. (Conn., 1844), and Whelpley (Conn., 1845).

The former anticlinal connection of the two sandstone strips in North
Carolina was suggested by Kerr in 1874, and extended by Bradley in
1876 to the Connecticut and New Jersey areas. Russell independently
made the same suggestion for the latter in 1878.

The trap has been considered a metamorphosed sedimentary deposit
by Wurtz and Martin (N.J., N. Y., 1870).

_ Plate I. may be taken as a pictorial supplement, in illustration of
the preceding abstracts. It embraces nearly all the sections that have
been drawn showing the Triassic traps within their sandstones. These
drawings are not fac-similes, but in the small changes that have been
made I think no injustice has been done.

1. Hitchcock (a). Across the Connecticut Valley in Northern Mas-
sachusetts. The vertical position of the greenstone intersecting the
strata of Deerfield Mountain was corrected in his next article (6), but
in the mean time it had served Cooper as an argument for the igneous
origin of floetz-trap. f

2. Hitchcock (6). East Haven (Conn.) dikes; their sides are too
regular and parallel. See our figure 44.

3. Eaton (c). Across the Connecticut Valley in Northern Massachu-
setts ; excessively wrong.

4. Smith. “Across the Connecticut Valley ; sandstone tilted by the
trap, which rose through chasms and overflowed at the surface.

5. Jackson and Alger (0). Southeastern side of Bay of Fundy.

6. Hitchcock (c, 221). Across the Connecticut Valley in Northern
Massachusetts.

7. Id. (c, 423). Turner’s Falls on the Connecticut in Northern Mas-
sachusetts. The increased thickness of the main trap sheet at the sur-
face is wrong.

8. Chapin (105). Across a number of ridges at Wallingford in
Southern Connecticut. The author failed to observe any interbedded
sheets.

MUSEUM OF COMPARATIVE ZOOLOGY. 281

9, 10. Chapin (109, 111). Details in the same region.

11, 12. Mather (PI. V., figs. 5 and 4). Dikes in the sandstone under
the Palisade trap, two miles south of Haverstraw, and near Verdrietje
Hook.

13, 14. Mather (Pl. XLV., figs. 3 and 2). Sections across Southern
New York and Northern New Jersey.

15. H. D. Rogers (c). Across the Newark Mountains, Central New
Jersey. The interbedded position of the trap is not shown.

16. Emmons (0, 200; ¢, 107). Palisade section at Slaughter’s Land-
ing, showing intrusions between the beds below the main mass of trap.

17. Lyell (c, 271). Dike in the Richmond Coal Field.

18. Dawson (a, Pl. V.). North shore of Mines Basin, opposite Two
Islands, Nova Scotia. Part of this section gives the appearance of a
post-Triassic overflow, but it is all described as contemporaneous.

19. Lesley (a, 133). Hypothetical section illustrating the use of
“ overflow” by Rogers as well as by the author.

20. Hitchcock (g, Pl. III.) Mount Tom, Mass., with incorrect in-
crease in thickness of the trap sheet as in fig. 7. .

21, 22. H. D. Rogers (g, II. 912, 691). Dikes at New Hope and
Gettysburg, Pa., producing metamorphism and cleavage.

23. Id. (g, Geol. Map Pa., sec. 8). General section near Gettysburg,
Pa., showing post-Triassic eruptions.

24. Emmons (d, sec. 1). Dike in North Carolina.

25. Cook (4, 200). True scale section of the Palisades. The author
says this “fails to impress the mind” as one of the exaggerated sections
does ; but it certainly has the advantage of giving a true impression.

26. Cook (a, sec. 1). East bank of Delaware by Lambertville, N. J.
There is some doubt as to whether these trap masses are sheets as here
shown.

27. Frazer (a, 298, sec. lla). Dikes near Gettysburg, Pa. It is
not definitely stated in the context whether faults exist’ as shown in
this section.

28. Leconte (440, 441). Hypothetical section of the Connecticut
Valley. If drawn on true scale the amount of erosion would be still
more enormous.

29. Russell (c, 230). Hypothetical section of the New Jersey and
Connecticut Triassic belts, showing their supposed anticlinal relation.

30. Id. (d, 47). Section of the Palisade trap at Weehawken, N. J.

31. Id. (d, 42), Ideal section of intrusive trap sheet. The descend-
ing branches seem to be of improbable occurrence.

282 BULLETIN OF THE

5. GENERAL DISCUSSION.

Origin of the Triassic Estuaries. — The small number of Triassic.
trough-deposits and their absence from the western half of our Eastern
mountains go to show that in the making of the Appalachians the syn-
clinals were not, as a rule, absolutely depressed, but on the contrary
took part in the general elevation, and rose with the rest of the strata,
although to a less height than the anticlinals: as they were continually
rising above drainage level, they very seldom or never served as troughs
for the accumulation of deposits. But, on the other hand, the estuaries
or troughs in which the Triassic strata were deposited must have been
absolutely depressed below their previous levels; and it seems reason-
able to suppose that the remarkable relation existing between the trap
and sandstone areas, so often alluded to, must be mechanically depend-
ent on this downfolding or absolute depression of the estuaries; for
here alone where there is evidence of absolute local depression are the
only post-carboniferous eruptions of trap to be found from the Green
Mountains to Alabama. That this may be truly a relation of cause
and effect is made the more probable by the evidence given in the fol-
lowing pages that much of the trap, if not all, was ejected during the
downfolding and filling in of the troughs.

Professor Dana (e, 113) considers that the subsidence which ended in
the post-Triassic eruptions was slow, and not more than five thousand
feet, and that it caused in the end only small displacements of strata,
wholly inadequate to cause the fusion and ejection of deep-lying rocks
from which the traps were derived. He further instances the Green
Mountains as a region where the folding was much stronger, and yet
where no eruptions but only metamorphism took place, and takes this
as arguing against the possibility that the moderate Triassic disturbance
was the cause of the fusion and ejection of the traps.

However it may be with the fusion, I must differ from this opinion
concerning the eruptions ; it seems best, in view of what has been stated
above, to suppose that the Triassic disturbance was directly and cau-
sally connected with the fact and act of the eruptions. The occurrence
of absolute depression in the slightly disturbed Triassic troughs seems
reason enough for mechanical eruptions taking place here, although
absent elsewhere in regions of greater disturbance but general absolute
elevation.

MUSEUM OF COMPARATIVE ZOOLOGY. 283

Origin and Deposition of the Triassic Strata. —There seems to be no
sufficient reason to look upon these stratified deposits as very abnormal
in their origin. Their material was derived from the highlands adjoin-
ing either side of their estuaries of lakes of deposit, and whatever the
agent of importation — glaciers, streams, waves, or tides — the layers
were probably coarser along the shores, finer in mid-water, and all essen-
tially horizontal when deposited. It is noteworthy that those who look
on the present dip as the result of original oblique deposition took this
ground less from direct evidence in favor of anything so extraordinary,
than from the hope of escaping from what seemed a greater difficulty ;
namely, the tilting to a (supposed) constant dip in one direction in each
monoclinal belt.

In addition to the great improbability of the theory of oblique depo-
sition, and its mechanical difficultiessof one sort and another, it has
to explain why very nearly all the detritus should have been derived
from only one side of each estuary ; and this in the face of the frequent
occurrence of heavy conglomerates of local derivation on the other
side. With the coarse material in the conglomerates, there must have
been introduced a great quantity of finer detritus, which was carried
farther from shore: how could this have been deposited dipping so uni-
formly towards its origin? The general absence of conglomerates along
the outcrop sides of the estuaries, appealed to by Russell (c, 231-238,
251) as evidence of open water and not of shore line there, is partly and
perhaps sufficiently explained by the fact that the outcrop side must
have lost a large share of its original mass on account of its elevation
and erosion. But it should be remembered that conglomerates or coarse
sandstones of local origin do occur on the outcrop sides of the belts.
Such are mentioned by Percival (430), Cook (6, 336; ¢, 31, 34), H. D.
Rogers (g, 669, 677, 679, 760), and Kerr (6, 141). An example of peb-
bles found on one side of a Triassic belt and derived from the other,
is given by Wurtz (100): he describes fragments in the sandstone
beneath the Palisades coming from Green Pond Mountain, which stands
northwest of the Triassic area. Further detailed study on the position
and source of these conglomerates is much needed in order finally to
prove or disprove the theories above mentioned.

The conditions and order of origin of the various strata, — conglom-
erate, sandstone, shale, limestone, and coal, — their even, cross-bedded,
and ripple-marked structure, and the causes that brought about a change
from one to another in this series, cannot be determined with any defi-
niteness until the strata are better co-ordinated than they are at present.

284 BULLETIN OF THE

I believe that in Connecticut and elsewhere there are repeated outcrops
of the same beds, produced by faults as described below ; but their iden-
tification is now a difficult matter. Microscopic analysis and detailed
study by local observers will do much to solve this difficulty.

Composition of the Trap. — The composition of the eruptive rocks in -
the Triassic belts is not discussed here, as the present work relates to
their physical characters. For this reason, the general term trap is em-
ployed throughout. Many names have been previously used, — whin,
greenstone, trap, basalt, sienitic basalt, diorite, trachyte, dolerite, and
diabase ; but the last two would seem the more proper ones, judging by
mineralogical composition. Chemical analyses and microscopic exami-
nations of the trap from various localities have been made by Cook,
E. 8. Dana, Frazer, Hawes, Schweitzer, and Wurtz. The following
statement gives the limiting percentages of their results : —

Silica 2 a ee
Alumina’ 6) oe) Sa ee
Ironoxides. .) 24). oe. B= 210geF
Magnesia, Lime, Soda, pacer less than 10% each.

The minerals present are pyroxene, labradorite, and magnetite, with
certain accessory species, and chlorite as a common product of alteration.
E. 8. Dana (391) and Hawes (a, 185) note an increase in hydratation
and alteration in going eastward across the Connecticut. It is notice-
able that the least modified traps are dikes or intruded sheets, and the
most modified are overflows, according to the present determinations ;
thus Hawes describes East and West Rocks and the Jersey City traps
as dolerites, and the Saltonstall and Durham Mountains (Conn.) as
diabases: Mount Holyoke gives an exception to this apparent rule, as
it is classed under the dolerites, although it is certainly an overflow.
The two authors above named considered all the trap as intrusive, and
consequently did not perceive the natural relationship between condi-
tions of origin and composition, as here suggested.

Relations of the Trap and Sandstone. —Two views as to the origin of
the trap sheets have been discussed. According to one, they are con-
sidered eruptive across or between the sandstone layers, and more or
less active in aiding the breaking, tilting, consolidating, and coloring of
the strata, after the period of deposition had ceased. The other view
looks on the trap sheets as younger than the sandstones below, and
older than those above them; or, as it may be stated, the sandstones
and traps are geologically contemporaneous; the sheets are old lava
overflows buried under strata of later date than their eruption.

MUSEUM OF COMPARATIVE ZOOLOGY. 285

The following review, arranged by localities, beginning in the north-
east, will give an idea of the various opinions that have been held.

In 1833, Jackson and Alger (6, 276) described the Nova Scotia trap
along the Bay of Fundy as “an immense dike, thrown up from beneath
the sandstone through some vast and continnous rent, produced by the
sudden eruptive upheaving of its strata, which allowed it to spread out
laterally only to a very limited extent.” In 1846, Gesner included the
same traps under the heading “ Intrusive Igneous Rocks.”

In 1848, Principal Dawson in describing these sheets said (58) that
volcanic action “brought to the surface great quantities of melted rock,
without disturbing or altering the soft arenaceous beds through which
it has been poured, and whose surface it has overflowed.” This is quoted
in his Acadian Geology, 1868.

Bailey and Matthew mention stratified columnar and vesicular traps
and trap conglomerates on Grand Manan; but further speak of the
traps as intrusive (219, 220).

For Massachusetts, Hitchcock’s first section (1818) shows the trap as
a vertical dike breaking across the sandstones; this was soon changed
(1823) and the trap and sandstone were described as in alternate beds
(5, 48), separating the old red sandstone on the west from the coal for-
mation on the east. In 1833, he described the conglomerate on the
back of Mounts Tom and Holyoke, consisting of “angular and rounded
masses of trap and sandstone, with a cement of the same materials,”
and concluded that some of the trap must have occurred as a con-
temporaneous overflow (d, 211). In 1844, the same conglomerate is
ascribed to small precursory outbursts during the formation of the sand-
stone ; but the larger ridges are considered intrusive and of later date.
In 1858, he decides that all the Massachusetts trap is of overflow origin,
as will be referred to below.

‘Lyell was shown the trap conglomerate on the back of Mount Tom
by Hitchcock, and inferred “that there were eruptions of trap, accom-
panied by upheaval and partial denudation, during the deposition of the
red sandstone” (a, 794). Leconte and Walling both adopt Hitchcock’s
final view, and it is recently confirmed by Emerson.

The rocks in Connecticut have given rise to other opinions. The
elder Silliman held that the trap was eruptive, but did not reach the
surface (1810-1830) ; his observations were mostly made when it was
still discussed whether the trap might not be of aqueous origin. Cooper
took strong ground in favor of the igneous origin of the trap, but did
not concern himself with the manner of its eruption: he implies, how-

286 BULLETIN OF THE

ever, a belief in overflows (240), though he quotes no decisive observa-
tion in this direction. Smith considered the trap eruptive over the
tilted layers of the secondary strata (225, 227), and Chapin represented
all the ridges about Wallingford as vertical dikes (fig. 8).

Percival states that the traps ‘‘ have obviously the character of intru-.
sive rocks of igneous origin,” which exerted “apparently a controlling
influence” in determining the arrangement of the sandstone (10, 11).
The trap occurs in dikes and ridges; the dikes are small; the ridges
are steep on one side, and on the other are frequently overlaid by sand-
stone, “thus apparently forming interstratified masses or inclined dikes.”
“In some instances, where the middle portion of a ridge appears thus
interposed, or merely as an overlying mass, its extremities appear as
distinct vertical dikes.” ‘The ridge and the dike may thus be regarded
only as modifications of the same arrangement.” (300.) His use of the
term “volcanic” (as 311) does not seem to imply that the eruptive
rocks ever reached the surface: nor does ‘ cotemporary formation”
(299, 321) seem by the context to indicate the contemporaneous origin
of the traps as used in this article. He would apparently agree with
those who considered the trap eruptive after the making of the sand-
stone, often appearing between its layers and strongly affecting its
position. The younger Silliman at first (1842) thought the sandstones
tilted by the intrusion of the trap, but later reported to the American
association of geologists, in 1844, that the sandstone had been deposited
as now standing, and that the trap had been intruded without disturbance
and had seldom reached the surface. Whelpley held similar opinions.

Professor Dana (6, 430) refers to Hitchcock’s observations on the
back of Mount Tom, and adds, ‘‘ But after an examination of the region,
the author regards it as more probable that the appearance of scoria is
owing to an escape of steam laterally from between the opened strata
during the ejection of the trap of the adjoining mountain.” In the later |
editions of his Manual, he makes no mention of overflows. He states
that the trap “has come up through fissures in the sandstone which
varied from a few inches to three hundred feet or more in breadth. In
many cases, it has made its way out by opening the layers of sandstone,
and in such cases it stands with a bold front, facing in the direction
toward which it thus ascended.” (c, 419; alsod, 46.) “The manner
in which the trap at its eruption has sometimes separated the layers of
sandstone, and in this way escaped to the surface, instead of coming up
through the fissures simply, shows that the rock had been tilted exten-
sively before the ejection.” (¢, 421.)

MUSEUM OF COMPARATIVE ZOOLOGY. 287

Akerly did not decide between the igneous or aqueous origin of the
trap of the Palisades (62).

For New Jersey, H. D. Rogers wrote in 1836 that the molten trap
had burst up through nearly parallel fissures, after the sandstone had
been tilted: the eruption caused no further change in the position of
the strata, but produced certain changes in their contents and structure
(a, 160): and in 1840, ‘the protrusion of the trap, the formation and
deposition of the conglomerate, and the elevation and final drainage of
the whole red sandstone basin, have hardly been consecutive phenomena,
so nearly simultaneous appear to have been these changes.” (c, 171.)
Cook considers the trap sheets intrusive. (b, 176, 200, 337; c, 32, 34.)
Russell gives good evidence of the intrusive nature of the Palisade sheet
(d), and claims to have proved the same origin for the First Newark
Mountain (a). Wurtz regards the Palisade sheet as metamorphosed in
place from sediments ; he is doubtful if this origin apply to the Newark
Mountain as well (101).

Pennsylvania gives so few good opportunities for observation, that
little has been written about its trap sheets and dikes, though they are
extensive and numerous. Many are omitted from the State Geological ©
Map, 1858. Farther south, dikes seem much commoner than sheets ;
and so far as I have learned, there have been only two suggestions of
contemporaneous overflow for any of the trap southwest of New Jersey.
The first, by J. B. Gibson, was written in 1820 and published in 1825:
“That the trap may have been deposited on the sandstone by a volcano
before the present continent was elevated above the level of the sea,
would be a more plausible supposition ; but it would be altogether gra-
tuitous.” (Observations on the Trap Rocks of the Connewago Hills,
159.) The second was by H. D. Rogers, who wrote: “In certain cases
the entire length of each middle secondary belt seems not to have been
uplifted to the sea level before the commencement of the trappean erup-
tions ; and those tracts which remained thus submerged are seen to con-
tain, interstratified, as it were, with the later sedimentary deposits, those
sandy volcanic tuffs or subaqueous sedimentary forms of trappean matter
which constitute the link between the exclusively aqueous and igneous
masses.” (g, II. 762.) The context shows that such cases were regarded
as very exceptional in Pennsylvania at least: no definite localities are
given. “Overflow,” as used by H. D. and W. B. Rogers (g, IT. 670 ; 6, 82)
and Lesley (a, 133), seems to refer to eruptions after some erosion of
the Triassic strata, so that the trap should lie unconformably on the
sandstones : they all seem to regard the trap as post-Triassic, with slight
exception.

288 BULLETIN OF THE

Heinrich accepts the general view of post-Triassic intrusion for the
Virginia traps (251). Fontaine writes that the “outpour” of fused rock
occurred near the end of the period of deposit (29); but his attention is
given more especially to the stratified rocks. Farther south than Vir-
ginia, there is no mention of anything but dikes in the sandstone.

It would thus seem that the overflow theory of the origin of the
trap sheets has found its most pronounced supporters north of Con-
necticut.

There is theoretically no difficulty in distinguishing between the in-
trusive and overflow modes of origin, and the practical difficulty and
difference of opinion above shown are probably to be explained by the
rarity of good points of observation.

If the traps are intrusive, the sandstone above and below should show
about equal signs of metamorphism ; there might be fragments of sand-
stone in the trap, and such should be well baked, but there could be no
fragments of trap in the sandstone; the trap might break across the
sandstone layers, or send branches off from its main body; the upper
surface of the trap should not be scoriaceous, especially in the thin
’ layers, for if intrusive it must have been under almost as much pressure
as the lower surface.

Examples of intrusive sheets elsewhere are described by the following
authors :— .
G. K. Gilbert. Geology of the Henry Mountains (Utah), 1877. The
intrusive rock is not vesicular at all; no fragments from it occur in
the overlying strata; metamorphism is marked as well above as below
the intrusions. The name of laccolite was proposed by Gilbert for such
masses of eruptive rock, and it may be applied to the Triassic intrusions
as well. The laccolites of the West still retain their original horizontal

position: those of the East have been tilted since intrusion.

Other less detailed mentions of intruded sheets may be found in the
Annual Reports of the Geological Survey of the Territories, 1873, 186
(Marvine), 234 (Peale); 1874, 64 (Holmes), 219 (Endlich); 1875, 60,
95 (Peale), 268 (Holmes); 1876, 194 (Holmes): in the Bulletin of the
same Survey, IIT. 1877, 551-564 (Peale).

A. Geikie. On the Tertiary Volcanic Rocks of the British Isles.
Geol. Soc. Journ., XXVII., 1871, 279-310. The flows and intrusions of
the island of Kigg are described in detail: the overflows have frequently
been regarded as intrusions (292), but the two are easily separated
by the difference in their metamorphic effects, and by the presence or
absence of slaggy, amygdaloidal structure (281); the intrusions “are

MUSEUM OF COMPARATIVE ZOOLOGY. 289

almost wholly confined to the lower portion of the volcanic series”
(295).

A. Geikie. On the Carboniferous Volcanic Rocks of the Basin of the
Firth of Forth. Edinb. Roy. Soc. Trans, XXIX., 1879, 437-518.
Both intrusions and overflows are again recognized; in the former, a
cellular or amygdaloidal texture is hardly to be observed, and never
when they are largely crystalline (475) ; in the latter, amygdaloids are
common (481).

If the trap sheets are old lava-overflows, there must of course be
supply dikes, by which the sheets were fed, and these dikes must cut
across and bake and be younger than all the strata they pass through,
but their cross-section will probably be small compared to the area
of the overflows; the sheets will be rather closely conformable to
the strata over which they flow, though, as might be expected, their
creeping advance while yet molten may have produced some disturb-
ance, and they may contain sandstone fragments; only the previously
formed sandstone beneath them can be baked; the upper and lower
surface of the flow should differ as in modern lava flows, the upper being
more vesicular and uneven than the lower ; one flow may cover another ;
the compact lavas may be preceded or followed by tufaceous or frag-
mentary deposits ; the overlying sandstone must lie conformably on the
uneven surface of the lava, adapting itself to all inequalities, and grad-
ually filling them to an even surface ; it may often contain volcanic sand
or fragments of lava.

Overflow sheets are much more common than intrusions; the follow-
ing references will lead to descriptions of some of the more notable.

K. C. v. Leonhard. Die Basalt-Gebilde, 1832. This work serves
well as a guide to the older European observations on eruptive rocks.
Both overflow and intruded sheets are recognized; the former are de-
scribed as scoriaceous on the surface, while the latter are generally dense,
because gas bubbles could not expand in their heavily compressed mass
(I. 475) ; but in speaking of the baking in the adjoining strata (II. 230),
the author does not clearly state the different effects of the two kinds
of sheets.

J. W. Dawson. On the Lower Carboniferous Rocks, or Gypsiferous
Formation of Nova Scotia. Geol. Soc. Journ., I., 1845, (29-31). Sev-
eral beds of trap conformably interbedded with the adjoining strata; the
trap is dense below, amygdaloidal above, and its fragments are found in
an overlying conglomerate. (See also ¢, 316, and section, 125; h, 49.)

J.S. Newberry. Pacific Railroad Reports, Vol. VI., 1857, ch. vi., vii.,

VOL, VII.—NO, 9. 19

290 BULLETIN OF THE

the overflows of the Columbia basin. Geological Report of the Colorado
River Exploring Expedition, 1861; many observations.

G. P. Scrope. The Geology and Extinct Volcanoes of Central France,
1858, 14.

Medlicott and Blanford. Geology of India, 1879, I. 299. Amygda-
loids are very common, especially in the upper part of the various flows.

M. E. Wadsworth. Geology of the Iron and Copper Districts of Lake
Superior. Bulletin Museum Comp. Zool. Cambridge, VII., 1880, 109-
113. The trap sheets are amygdaloidal at the upper surface: they
were first shown to be overflows by Foster and Whitney, in 1850, but
various opinions have since been expressed concerning them.

In the Western Territories, lava overflows have been very common,
and have covered vast extents of country. They are mentioned in
nearly all the Western Survey Reports, but their overflow origin is as
a rule so evident that few special descriptions are given of the characters
that serve our needs of comparison. The following may be referred to
from among many others: King, 40th Parallel Survey, I. ch. vii. sec. v.
Geol. Survey of the Territories, 1874, 172 (Peale) ; 1875, 145 (Endlich).
C. E. Dutton, Geology of the High Plateaus of Utah, 1880, ch. iii.

The above means of distinction between intrusions and overflows are
almost self-evident ; but they have seldom been definitely stated in con-
nection with our Triassic traps, and have often been entirely overlooked.
The earlier studies of the traps were made when the controversy between
the Vulcanists and Neptunists was still unsettled ; it was sufficient then
to show that the traps were igneous, not aqueous. But later than this,
and down even to recent dates, observations on the traps seldom give
secure basis for statement of their mode of origin, for the essential and
critical points for observation have been very generally neglected. In
many cases the older observers gave no special attention to this physi-
cal phase of the question ; their work being directed to some other of
the many difficulties that the Triassic rocks present; and hence from
their accounts it is impossible to discover how the trap is related to the
adjoining rocks. Even Percival’s remarkably painstaking and accurate
description of the Connecticut traps is often indeterminate as to their
origin ; it is greatly to be regretted that he had not. better opportunity
to publish what he had learned, in addition to simple descriptions.

The rare exposure of contact lines is extremely provoking: in the
Connecticut valley alone their combined length must amount to many
hundred miles, but so universal is the drift and talus covering, that one
seldom finds more than a few feet of “junction” exposed. And this

MUSEUM OF COMPARATIVE ZOOLOGY. 291

is especially the case for the more important upper contact with the
sandstone on the back of the trap; for during the ages in which these
rocks have been eroded, they undoubtedly stood frequently or always at
a higher level above the sea than at present; the soft beds were deeply
worn away, and are now buried under the clays and sands of post-glacial
weathering or of glacial deposit. Upper contacts are everywhere rare.
Lower contacts are not very uncommon in Massachusetts, Connecticut,
and New Jersey; but nearly all contacts are hidden in Pennsylvania
and farther south. The discovery and description of the junction of the
trap with sandstone above and below it afford excellent field for local
observations in all the Triassic belts.

The observations of the past summer, as detailed in the preceding
pages, give examples of nearly all the points of evidence required to
prove an intrusive or an overflow origin of the trap sheets. The locali-
ties where the best evidence of overflow sheets was found are : — Con-
formable, unbaked sandstone on the trap, or fragments of trap in the
overlying sandstone, at Turner’s Falls; on the back of Mount Tom and
its posterior ridge; and at Feltville, on the back of the First Newark
Mountain. Tufa deposit with fragments or bombs of trap, under the
second posterior ridge, Turner’s Falls. A second lava-flow resting on
the uneven amygdaloidal surface of an earlier one, at West Springfield.
Percival mentions a trap breccia or conglomerate at several points. in
Connecticut. Dawson represents a large mass of these fragmental trap
deposits in his Nova Scotia section.

Three distinct forms of occurrence must be admitted for these traps :
first, the feeders, or supply dikes ; second, the intruded sheets, generally
lying evenly between the enclosing layers; third, the overflow sheets.
The second and third forms are generally closely alike in their present
topographic features, and can be distinguished only by detailed observa-
tion. Even in the best known districts, there is room for much work of
this kind.

Trap Dikes. —Under this heading will be included only those trap
masses that have a greater extension across the sandstone layers than
parallel to them. They have been observed as follows : —

Dawson and Harrington note a single occurrence of trap on Prince
Edward Island in a dike form; it is vesicular and scoriaceous in part,
as well as dense and columnar (21).

Bailey and Matthew mention a dike in the Triassic of Grand Manan
(221).

Hitchcock says there are no well-characterized dikes in the Massa-

292 BULLETIN OF THE

chusetts sandstones (e, 655); the only possible case of the kind was
found on the south side of Mount Tom, near a saw-mill on a stream, not
far from the main road three miles below Northampton (e, 656).*

In Connecticut dikes are comparatively common. The first examples
recognized were described and figured by Hitchcock in 1823 (6, 56);
they are in East Haven, eight narrow dikes within four hundred feet.
(See figs. 2 and 44.) Chapin was the first to describe and figure some
of the numerous and irregular dikes about Wallingford in 1835 (fig. 10).
Percival refers to all of these, and adds many others; but it seems that
he sometimes applied the word dike to sheets, and therefore we cannot
say how many of his examples would come within our limitation. Pine
and Mill Rocks at New Haven (G) are the largest dikes observed in
the State.

Mather gives one or two examples from the face of the Palisades
(279, 282, here copied, figs. 11, 12).

Cook finds only two dikes in New Jersey ; one near Blackwell’s Mills,
on the east side of the Delaware and Raritan Canal ; the other in a road
cut beyond the Flemington copper mine; but he thinks it probable
that many others lie hidden below surface drift (b, 204; a). He later
says there are many places where the trap can be seen cutting across
the stratified rocks, as by Hook Mountain, Palisade range (c, 32).

In Pennsylvania and beyond, dikes become more common. H. D.
Rogers figures two examples (here copied, figs. 21, 22), and on the State
map (1858) a number are represented within and without the sandstone
belt : of the latter, the most remarkable is the long dike discovered by
Henderson, which extends some eighteen miles, across the Juniata and
Susquehanna near their junction. Frazer describes the dikes in Lan-
caster and the adjoining counties as so numerous and so difficult to trace
that he was unable to represent them all on his map (c, 27); he says,
also, ‘‘ The outflow of trap probably followed one or more of the planes
of cleavage, of which these rocks are full” (6, 325; his sections showing
dikes are cautiously drawn without contact lines : compare extract below,
under Intruded Sheets).

W. B. Rogers mentions dikes cutting across the sandstones in Vir-
ginia (+, 82), and Heinrich writes that, “Penetrating the sedimentary
rocks, igneous rocks are occasionally met with in the form of dikes”
(244, also 250, 263). -

* Since writing the above, Professor C. H. Hitchcock tells me that he has seen
one or two small vertical dikes cutting the sandstone in a quarry on the sonthwest
slope of Mount Holyoke about half a mile from the Connecticut, — the only examples
of the kind known to him in the State.

MUSEUM OF COMPARATIVE ZOOLOGY. 293

Lyell shows a dike in his section of the Richmond coal field (c, 271 ;
our figure 17). Olmsted (c, 236) and E. Mitchell speak of trap dikes
in North Carolina. Emmons does not describe or figure any sheets, but
shows several dikes on his sections (¢d; our figure 24). Kerr states
that the sandstones are everywhere intersected in various directions by
dikes of trap; their thickness varies from a few yards to two or three
rods, and their length occasionally reaches several miles: the sandstones
and shales are usually blackened for several feet or yards on either side
of the dikes (+, 146); the dikes are usually transverse to the stratifi-
cation (a, 48).

It would seem from this review that dikes are rare in Nova Scotia,
in Massachusetts and Northern Connecticut, and in New Jersey; while
they are common in Southern Connecticut, in Pennsylvania, and farther
south. They are of all sizes up to two hundred feet, Mill Rock and Pine
Rock just north of New Haven being the largest well-known examples.
They are, as a rule, dense and compact, with a rough columnar structure
at right angles to the sides; some are reported as amygdaloidal, but
such are clearly exceptional; their vesicles are very likely not of gas-
bubble origin. The sides of the dikes are not smooth, like the sides of
most of the dikes in the old jointed slates about Boston, but are more
or less irregular or even ragged (fig. 45) ; implying that there were no
joints to guide their fissures. It should be noted, however, that some
of the looser sandstone is still almost without joints, and in such cases
this point of evidence is of no value. Their metamorphic effects are not
far reaching so far as observed : a dike ten feet wide bakes the sandstone
for a foot ; a hundred-foot dike has some effect ten or twelve feet away.
None of these dikes have clearly the form of “necks” or “chimneys,”
such as are described by A. Geikie about the Firth of Forth (Edinb. Roy.
Soc. Trans., XXIX., 1879, 468).

Intruded Trap Sheets. — A number of sheets named in the following
list cannot be regarded as fully proven to be of intrusive origin : the evi-
dence for Pennsylvania and the States farther south is very incomplete.

There seem to be no intruded sheets north of Middle Connecticut.
Farther south, near New Haven, East and West Rocks (G) and the
northern continuation of the latter have long been rightly regarded as
intrusions. Smaller examples occur at Wallingford (F), and doubtless
many more may be found.

Percival’s descriptions make it very probable that all his western line
of elevation from East and West Rocks at New Haven north to South-
ington are intrusive traps. In evidence of this, we may note the general

294 BULLETIN OF THE

absence of amygdaloid here (mentioned once on 403), and the frequent
mention of indurated sandstones above as well as below the trap. The
sandstone near the trap by East Rock (W.S. I. 1) * “is remarkably in-
durated to an unusual width” (395). Two points on the back of East
Rock show “highly indurated sandstone” bordering the trap (396).
Mill Rock (W. 8. I. 2) is a dike rather than a sheet, and is bordered by
“light gray very indurated coarse sandstone” (396). West Rock
(W.S. I. 4) is overlaid or bordered on the east by indurated sandstone
(399). ‘The dikes or ridges of W.S.I. 7 are bordered by “singularly
altered and indurated” sandstone (401). Roaring Brook shows indu-
rated sandstone on the back of W.S.II. (403). “At different points,
in connection with the western line of trap,” dark purple, black, and
bright indurated sandstones are found (437). Professor Dana classes
East and West Rock, Mount Carmel, and the Meriden Hills with the
dikes of Pine and Mill Rock, as trap “that came up melted through
wide fissures in the sandstones and subjacent rocks” (d, 46).

The Palisades give the largest example of intrusion: this origin was
first well proven for them by Russell (d ; see also our observations, H, J) ;
Emmons noted, a number of years ago, that branching intrusions oc-
curred in the sandstones below (0, 200; his figure is here copied, 16).
Smaller sheets are found in New Jersey at Martin’s Dock (N), and on
the Delaware (O); whether the large coarse trap masses by Lambert-
ville (P) are dikes or sheets, I cannot fully decide; but they are not
overflows. Cook inclines to the intrusive origin of all of these (6, 176,
200) ; he mentions the occurrence of transverse dikes by Hook Moun-
tain, the north end of the Palisade Range (c, 32), which would seem to
correspond to the large dikes by West Rock, Conn. H. D. Rogers’s
sections represent intruded sheets in the Pennsylvania sandstones near
the surface (here copied, fig. 23); and Frazer says of the traps about
Lancaster County, “As a general rule in this region, their dip corre-
sponds to that of the beds between which they were poured out” (6, 318;
compare with the quotation above, under Dikes).

W. B. Rogers describes the trap in Virginia as ‘‘not unfrequently
entering between the layers of sedimentary rock, or pouring out and
overspreading them at the top” (4, 82); and Lyell writes of the trap
in the Richmond coal field that it, “although intrusive, has often here,
as is so common elsewhere, made its way between the strata like a con-
formable deposit.” But all these latter references are inconclusive as to
intrusions or overflows ; they leave the question open for further work.

* The notation used by Percival.

MUSEUM OF COMPARATIVE ZOOLOGY. 295

The trap sheets which are definitely determined to be intrusive show
no vesicular structure at any point so far as I have seen them; they are
dense throughout, fine at the margins and very coarse in the centre of
the larger sheets. Their metamorphic effect on the adjoining sandstones
is very marked, as will be described below. The even intrusion of these
sheets between shaly or sandy strata is very remarkable. At Martin’s
Dock and Point Pleasant Station, N. J. (N, O, figs. 51, 52), where this
is best shown, trap sheets of various thicknesses, from two to twenty
feet, are seen evenly interposed between the strata above and below
them for fifty or more feet, without breaking across the layers at any
point: in two cases the slaty partings between adjoining trap sheets
are less than one foot thick, and yet are continuous for over fifty feet.
From this it must be supposed that the molten trap was injected slowly,
and that it acted as a liquid wedge, prying open a passage for itself along
the planes of easiest breakage that could be found: where two sheets
are close together, one was probably intruded after the other. Still it
is surprising that any rock could break so evenly as the Triassic strata
are thus proved to have broken.

It is not a little interesting to discover that the largest clearly intru-
sive sheets, the West Rock range and the Palisades, are found on the
outcrop side of their respective sandstone belts; they are near what
would be the bottom of the sandstone series if the entire formation had
received a single monoclinal tilting. The intrusions on the Delaware are
also near the’base of the formation, as is shown by the appearance of
the Matinal limestone not far from them. The probable cause of this is
suggested below.

The date of these intrusions is indeterminate. It cannot be fully
shown when they took place; whether at about the time of the over-
flows, thats is, the latter half of the Triassic time, or whether their
intrusion came later, when deposition was stopped by upheaval and dis-
location ; but the latter is the more common view.

Professor Dana has already been quoted as taking the position of the
trap sheets as evidence that their intrusion came after the sandstones
had been tilted extensively (c, 421). But the laccolites of the Henry
Mountains, Utah, as described by Gilbert, and similar intrusive rocks in
Colorado described by Peale (referred to above) lie between horizontal
strata ; it is therefere not necessary that the sandstones should have
been tilted in order that the trap might be forced in between its layers.
Professor Dana further argues, from the fact that the trap columns on
the face of the ridges are at right angles to the sandstone layers, that

296 BULLETIN OF THE

“there was a tilting of the strata in progress, before the final breaking
and ejections” (c, 421). ‘This is also inconclusive ; for the same relative
position of columns and strata obtains in the sheets that overflowed
on horizontal layers, the entire mass being tilted bodily afterwards.
We must therefore differ from the conclusion that the eruptions of the
trap were necessarily the “closing events of the sandstone period,” or
that they took place in “a succeeding epoch” (c, 421). The overflow
sheets were certainly of earlier formation: the intruded sheets may
have been so as well.

Russell states that the outbursts of trap occurred after the sedimen-
tary rocks had been consolidated and upheaved, and at the time when
the post-Triassic elevation culminated. His evidence for this view is
theoretical (c, 245, 251) and is seriously weakened by the occurrence of
overflows. ‘The generalized section that he gives for the Palisade sheet
(d, here copied, fig. 31) shows some down-branching dikes of proble-
matic occurrence. Cook classes all the traps as eruptive after the depo-
sition of the sandstones and shales (c, 32).

The evidence which points to an early date for the eruption of the
intruded sheets is, first, the ragged line of contact with the sandstones
where they are broken across; this, as has already been mentioned
under the dikes, indicates an eruption before the making of joint planes,
and consequently before the tilting; but it is not final or conclusive.
Second, the occurrence of intrusions chiefly on the outcrop side of the
sandstone belts, or, in other words, near the base of the formation ; the
only cause that I can suggest for such a limitation of position is that
these laccolitic intrusions could only form at a considerable depth, and
under considerable pressure, and were therefore placed near the bottom
of the sandstones before the latter were tilted: if the intrusions had
taken place after the tilting, they might break out at one point as well
as another, and would not be likely to have so peculiar a restriction as
that above noted. Third, the intruded sheets have the same crescentic
form as the overflows; and this, as will be shown farther on, results
from folding after the eruptions: while it is possible that the intrusions
were guided into their curved line of outcrop by the gently folded strata,
it seems more probable that all were folded together.

But, as stated above, this question is at present indeterminate; the
above suggestions may serve to counterbalance opinions on the other
side of the question, but not to settle the matter. It remains with a
number of other points, notably the monoclinal structure, open for
further observation.

MUSEUM OF COMPARATIVE ZOOLOGY. 297

The force which caused the intrusion of these sheets can hardly have
been the expansion of vapors and gases, which plays so important a
part in modern volcanoes ; for evidence of such expansion (vesicular
structure) is wanting. It was therefore more likely mechanical, and
connected as already suggested with the downfolding of the troughs
rather than with the subsequent elevation and tilting of the sandstones.
So far as this holds good, it also points to a Triassic date for the intru-
sions as well as for the overflows.

Overflow Trap Sheets. — By far the greater number of trap sheets seem
to be of overflow origin. The proof of this origin is more or less com-
pletely established for the following examples.

The high trap cliffs of the Bay of Fundy are described by Dawson as
overflows, but he gives no account of their upper contacts, and his sec-
tion (here copied, fig. 18) shows much more irregularity than any that
I have found in Massachusetts and farther south. But amygdaloids
are very common in Nova Scotia, and these seem limited to overflow
sheets. On Grand Manan the trap and amygdaloidal beds conform to
the adjoining sandstones (Bailey and Matthew, Verrill). The Connecti-
cut valley gives many examples. Farthest north is Deerfield Moun-
tain, as recently described by Emerson and as represented in this
paper (A); the long range beginning at Belchertown, Mass., including
Mounts Tom (B) and Holyoke, and extending to the Hanging Hills (E)
by Meriden, Conn., has been fully shown to be an overflow in its north-
ern part, and it can hardly be of other origin farther south. Its lateral
ridges are probably all overflows as well. Hitchcock’s observations
applied to the posterior ridge on the back of Mount Tom, and should
have left no doubt of its mode of formation.

In Connecticut, much observation is still necessary to decide finally
on the origin of the numerous ridges. The evidence that favors the
intrusive origin of all Percival’s western line of elevation has already
been stated. Equally good evidence may be found to show that all the
large and most of the small sheets of the eastern lines of elevation are
overflows. The frequent occurrence of indurated sandstones, and the
general absence of amygdaloids, in the west, contrast strongly with the
lack of evidence of distinct metamorphism, and the frequent mention of
amygdaloids, and trap and amygdaloid conglomerates, in the east. Toket
Mountain (E. II.) is described as dense trap at the base, amygdaloidal
at the top, and overlaid by friable red shale (Percival, 338). Lamenta-
tion Mountain (E. III. 5) has swells of amygdaloid on the back, overlaid
by shale (352). The anterior range is separated from the main range

298 ' BULLETIN OF THE

of Newgate Mountain (E. IV. 2. 2) by a band of friable red shale
(391). A part of A. 1, S. of E. Il. shows a peculiar dark green trap con-
glomerate, accompanied by beds or dikes of amygdaloid and fine-grained
trap (341). A conglomerate east of Saltonstall Lake contains fragments
of a fine-grained light green sub-amygdaloidal trap, similar to that in
P. 1 of E. I. (324). The ridge anterior to Lamentation Mountain is
partly composed of a peculiar trap conglomerate, or rather brecciated
amygdaloid, distinctly parallel or stratified in its arrangement (365).
Many similar extracts might be noted.

In New Jersey, I believe First Mountain to be proved an overflow by
observations at Paterson and Feltville (Land M), although Russell takes
the other view. As early as 1822, Cooper wrote that “this mass of
floetz trap is poured over the old red sandstone” (240), but it is doubt-
ful whether he had considered the possibility of its intrusion. Second
Mountain is probably also an overflow, as its sheet is very amygdaloidal
and irregular in structure near the under surface at Little Falls, and
its effect on the underlying sandstone is very slight ; but its upper con-
tact has not yet been described. Cook mentions pebbles of trap in the
sandstone beneath the First Mountain (6, 337), but later says that no
fragments of trap are found in any of the stratified beds (¢, 34).

There are no decisive observations of contact for the trap sheets of
Pennsylvania and the States farther south. H. D. Rogers speaks indefi-
nitely of “overflowed” trap (g, 670), of amygdaloid near the borders of
certain of the larger dikes (g, 671), and of ‘“‘sandy volcanic tuffs” and
“trap shales” interstratified with the sandstones, mostly in Nova
Scotia, some in Connecticut and the Middle States (g, 762). Lesley’s
general section (copied in fig. 19) shows ‘the original sea, the lava and its
vent, the manner in which it lifted the new red layers at its outburst,
so soon as it was near enough the surface to do so, and overflowed them
above”’ (a, 133), but evidence to prove this sequence of events is wanting.

Heinrich mentions that amygdaloids are found in the Virginia traps
(244).

The sheets which are proved by their appearance at the contacts to
be overflows have the following characters: they produce very little
metamorphic effect on the underlying strata; they often show some ve-
sicular structure near the base, sometimes within the mass, and are
always very amygdaloidal at the upper surface. It cannot be said that
amygdaloids occur only in the overflow sheets, for they are reported in
some dikes, and in rare instances in intrusions; but the vesicular struc-
ture is as frequent in the overflows as it is rare elsewhere.

MUSEUM OF COMPARATIVE ZOOLOGY. 299

Percival noted that the amygdaloids are generally found in the lateral
portions of the trap ranges, and occasionally make a large part of the
lateral ridges (315); Hitchcock wrote that amygdaloids occupy “ the
easterly [i. e. posterior or upper] part of the ridges wherever I have
examined them” (e, 645); and Rogers, that amygdaloids are common
“near the borders of certain of the larger dikes” (g, 671).

The occurrence and position of the amygdaloid has been variously
explained. Jackson and Alger (, 265) thought this texture resulted
from the combination of the trap with sandstone and shale. Rogers
stated that the amygdaloid occurred “in immediate contact with the
altered red shale, by the reaction of the trap upon which this amygda-
loidal character has been acquired” (g, 761, 763). Cook says that if
the cooling of the traps had been “rapid and not under much pressure,
they would be more or less cellular” (6, 215). Professor Dana con-
siders all the original trap to have been equally anhydrous at its deep
source, and to become vesicular by the expansion of steam formed
wherever water was met in the process of eruption (¢, 107). E.S.
Dana and Hawes accept this cause.

Several of these explanations are undoubtedly true and possible, but
they do not show why the overflows should always be amygdaloidal on
the back, and why the intrusions should so generally be compact. It
seems most probable that the vesicular texture was produced in these
old traps as it,is in modern lavas ; not so much by meeting water during
their eruption, as on account of a decrease of pressure which allowed the
occluded gases and vapors to separate from the surface of the overflowing
molten mass (Dawson, d, 63; e, 87). The difference in the composition
of the eastern and western traps found by E. 8S. Dana and Hawes in
lower Connecticut has already been referred to as resulting naturally
from the better chance the eastern traps have had for alteration.

The area marked by some of the larger ranges is very considerable.
The Mount Tom — Hanging Hills range has a front sixty-five miles long,
and, judging by the curves at either end, its breadth must be six miles,
giving an area of nearly four hundred square miles. If the several loops
down as far as Saltonstall Lake all belong to the same sheet, broken by
faults, as is suggested below, then the length and breadth would be
much increased, and the area might be over seven hundred square miles.
The Newark Mountains in New Jersey would in the same way have an
area of above three hundred square miles.

But it is not by any means proven that these sheets are the product
of single eruptions. The heavy trap which forms Mount Tom (B) de-

300 BULLETIN OF THE

creases in thickness or disappears entirely in going south, and the range
is continued for a time by a varying number of smaller sheets. So at
Turner’s Falls (A), the southward ending of the first and second poste-
rior ridges seems as well explained by the giving out of the trap at the
edge of its flow-area, as by the faulting suggested by Emerson. At
West Springfield (C), the composite structure of the second posterior
trap is well shown. In New Jersey the irregularities in the columnar
structure of the Newark Mountains at Paterson and Little Falls (L) may
be perhaps explained by supposing each mountain to be the product of
several consecutive flows. It seems, therefore, probable that the long
trap ranges: represent a period of volcanic activity, rather than a single.
violent outburst, preceded and followed by periods of shorter or less in-
tense activity represented by the anterior and posterior ridges. This is
shown in Connecticut far better than anywhere else, and is beautifully
illustrated by Percival’s remarkable map.

The importance of the overflow trap ranges as marking horizons in
the deposit of the sandstones will be referred to later.

Effect of the Trap on the Sandstone.* — A metamorphic effect is gen-
erally attributed to the trap, by which the sandstone in its neighborhood
has been indurated and changed in color to a greater or less extent.
The most exaggerated form of this idea ascribed the general red color
of the whole formation to the effects of trap heat (Hitchcock, d, 242 ;
see also Percival, 430, and Dana, c, 420); but as red sandstones are
common in other regions far from any contemporaneous or subsequent
igneous action, it is more probable that their color here as well as there
is essentially due to conditions of weathering at the time of deposit.
Whether the contemporaneous volcanic action in the Connecticut valley
aided the coloring of the sandstones or not, is difficult to say; for bright
colored strata are found far from and near to the horizons of the vol-
canic rocks. But, as a general rule, the baked strata near the trap
are not so red as the unaltered layers farther away. Above and below
the Palisade trap sheet (H), the rocks were black, gray, or dull reddish-
brown, but not strong or bright red as is common elsewhere. Under
Mount Tom (B), the sandstones near and at the contact were gray or
dull greenish-gray. Along the Delaware (O, P), the layers nearest the
trap sheets or masses were black or dark gray; the red strata appeared
only several hundred feet on one side or the other, so far as seen: these

* T have not yet had time to examine closely the mineralogical changes produced
by the trap; some of these, as shown by specimens collected during the past sum-
mer, are very striking.

MUSEUM OF COMPARATIVE ZOOLOGY. 301

last are the most extended effects of the trap that I found. In the West
Springfield - railroad cut (C), the baked sandstone for a quarter or half
inch from the contact was almost white on fresh surfaces.

The absence of red color in strata near a contact has been noted by
several observers. Silliman described the sandstone close under the trap
of Rocky Hill by Hartford as gray or white (e, 125). Percival found
that the sandstones near the trap were “sometimes discoloured greenish
or brown, and at other times their usual reddish color is apparently dis-
charged, leaving them nearly white” (319, also 436): in a few cases
they are black or red (437). Lyell found some of the shales turned
white below the traps of the Richmond coal field (c, 271). H. D. Rogers
described the shales near the traps as dull brown or purple (g, 673,
678). The change to black color as a consequence of baking is men-
tioned by Cook (6, 206, 212) and Kerr (0, 147). In view of these facts,
it is impossible to consider the prevailing color of the New Red Sand-
stone in any way dependent on the action of the trap after the deposit
of the sandstones. How much effect the contemporaneous eruptions may
have had upon weathering and color, is an open question.

In regard to the effect of the trap on the hardness of the sandstone
the most excessive views were those of H. D. Rogers, who considered
most of the good building sandstone in New Jersey hardened by baking
(c, 157) ; and of Whelpley, who thought that the sandstones had covered
a broad area in Connecticut, but had been preserved only near the trap,
where it was hardened (62). But here, as before, it may be urged that
as hard sandstones occur plentifully in regions free from eruptive rocks,
it is more probable that variations in the hardness of the sandy and
shaly Triassic strata, except those close to the trap, are due to the un-
equal action of the ordinary processes of consolidation. Whatever dis-
timct hardening effect was produced by the trap, it generally extended
but a short distance into the adjoining rocks, — probably in no case more
than one hundred feet. Slight mineral alteration reached farther than
any other notable change.

The marked difference between the effects of the intruded and the
overflow sheets has already been pointed out. The Palisade trap (H, J)
hardened the adjoining sandstones and shales very distinctly for twenty
feet and probably farther, and in some of the more easily altered layers
produced a marked crystalline structure: this was equally apparent at
upper and lower contacts. On the other hand, the lower contact of the
overflows shows a very slight change from the normal sandstone. Em-
erson describes the alteration under the Greenfield trap as extending

302 BULLETIN OF THE

only an inch from the contact, and the baking as reaching only a foot
(196). Under Mount Tom (B), the baking reaches three feet or more.
Under the First Mountain trap at Paterson (L), the alteration is dis-
tinct for several inches.

The different effects in these contrasted cases evidently depend on the
manner and rate of cooling. The intruded sheets must have cooled
slower, and entirely by conduction through the enclosing rocks, and
hence produced more baking than the others. The difference in the
baking effects of different intruded sheets can probably be largely re-
ferred to the variations in the composition and the amount of moisture
present at the time of intrusion.

Tilting of the Sandstones and Traps. —The remarkable monoclinal
structure of several of the Triassic belts has given sise to five supposi-
tions: first, that the present is the original position of deposit ; second,
that the originally flat layers have been tilted into a monoclinal without
faulting ; third, that certain paired belts are lateral remnants of a broad,
eroded anticlinal ; fourth, that the present position is the result of re-
peated faults and moderate folds; fifth, that a tilting was in progress
during the deposition (Cook, 6, 174; ¢, 34). I am unable to give any
evidence for or against this last proposition.

Before speaking of these theories we may note the structure of the
several Triassic belts ; for some of them do not present any very peculiar
features in the position of their strata. On Prince Edward Island the
formation shows repeated faint folds (Dawson and Harrington). Around
the Bay of Fundy there is an unsymmetrical synclinal, with the greater
visible part on the southeast. The Connecticut valley belt has a pre-
vailing dip to the eastward, but with significant exceptions. The long
strip from the Hudson extending almost continuously to the Dan River
in North Carolina has a similarly prevailing dip to the northwest or
west, but also with certain irregularities. The Richmond coal field is a
synclinal, strongly faulted (W. B. Rogers and Heinrich). Two patches
north and east of it, and the Deep River strip reaching into South Car-
olina, dip to the east or southeast (Heinrich and Kerr).

first Theory. — H. D. Rogers first thought that some external force
was responsible for the tilting (a, 160), but soon replaced this supposi-
tion with the theory that the several sandstone belts from the Dan River
to the Hudson had been deposited with their present oblique dip in a
noble river that rose in the mountains of North Carolina and flowed
northeast to the ocean about New York Bay , that the occasional rever-
sal of dip was produced by eddies in the great current; and that the

MUSEUM OF COMPARATIVE ZOOLOGY. 303

monoclinal theory was impossible because the great depth that it re-
quired for the sandstone was disproved by the visibility of the old foun-
dation rocks at certain points within the Triassic belts (b; ¢, 166-171;
d; g, 671, 761). Mather replaced the river by ocean currents, but oth-
erwise accepted this explanation. Whelpley thought the large and small
sandstone areas of Connecticut once connected by a general, oblique
deposit, since eroded except where trap intrusions preserved it. This
theory has gained few advocates. Oblique deposition on so large a scale
and at so uniform a dip as sometimes occurs over large areas is impos-
sible; and as has already been pointed out, the occurrence of plentiful
conglomerates on the dip side of the sandstone belts is a strong argu-
ment against it. The unsymmetrical form of footprints, as if made on
a sloping surface (H. D. Rogers, d), is too exceptional to be of much
value (Hitchcock, 4, 17). On the other hand, it need not be claimed
that the layers were absolutely horizontal when formed. Some small
share of their present dip may be original.

Second Theory. — The theory of anticlinal remnants was first proposed
for North Carolina by Kerr, in 1874. It was extended by Bradley (289)
to Connecticut and New Jersey, in 1876, and proposed for the same
region independently by Russell, in 1878. Heinrich suggests a some-
what similar explanation for the several sandstone patches in Virginia
(249), but later considers each estuary isolated (251). The objections
to this theory are well set forth by Dana (9); it has the serious defect
of resting on ‘negative rather than positive evidence ; it fails to explain
the general absence of trap in the intermediate region, and the occur-
rence of such an isolated sandstone patch as that of Waterbury, Conn. ;
the amount of erosion it requires is something enormous ; the occurrence
of conglomerates along the outcrop side of the sandstone belts has already
been mentioned as arguing against it. (See fig. 29.)

The Third Theory supposes the entire body of horizontal strata tilted
to a uniform dip, and the upper parts worn off. This has been advocated
by Hitchcock (c, 221, and later), partly by Cook (6, 174), and more re-
cently and decidedly by Leconte (441). Besides the great thickness of
strata that this supposition requires, and the enormous erosion it involves,
not only of sandstones but of the older rocks on one side, the theory is
based on the assumption that there is no faulting or reversal of dip ; and
this is not proven. If lack of visibility sufficed to prove the absence of
faults, it might be said that there are none in Pennsylvania, Virginia,
and Tennessee; for fault-planes are hardly ever seen there; they are
lines of weakness, and are always covered with detritus. Their exist-

304 BULLETIN OF THE

ence is known by the repetition of outcrops that they produce, and this
test can hardly be applied as yet in the Triassic belts, for the beds there
are, as a rule, too little varied to be recognized at their repeated appear-
ances, if such occur. On the other hand, as may be inferred from the
position of the intruded sheets, there is evidence that, however numer-
ous the faults may be, they fail to bring up the lowermost strata; and
the great sweep of the trap curves in New Jersey would indicate an ap-
proach to the simple monoclinal structure. These considerations would
imply a great thickness for the sandstone. (See figs. 6 and 28.)

The Fourth Theory looks on the general monoclinal dip as the result
of tilting with faulting and some slight folding, but is unable to explain
the mechanism of the disturbance; and here with regret I must take
my place. Much more observation is necessary before any detailed ex-
planation of this peculiar disturbance can be made. It can now be said
only that the disturbing force pretty surely was one of the latest mani-
festations of the Appalachian mountain-building, which began and had
its greatest activity long before; and that the eruption of the trap had
no important share in it. Here, as in so many other cases, the trap is
relegated to a passive ré/e; and as already suggested, its eruption was
very probably a direct effect of the force which at one time depressed
the Triassic troughs, and later deformed the rocks collected in them.

It is sometimes objected that it is mechanically impossible to fault a
series of horizontal layers into repeated parallel monoclinals. In an-
swer to this it should be urged that too little is still known of geological
mechanism to make such apparent impossibilities of much importance ;
that faulted monoclinals of gentle dip have been found in the Western
plateaus (see Dutton’s sections of the High Plateaus of Utah), and ot
steeper dip in Tennessee (Safford’s Geology of Tennessee); and that the
Triassic monoclinals show not infrequent irregularity too great to be
considered the result of eddies (as Rogers thought), and implying the
presence of incipient folds.

As to the occurrence of faults, some of small throw are seen in Delany’s
Quarry above Holyoke (B), in the West Springfield railroad cut (C), and
on the northern slope of Garret Rock, Paterson (L); slickensides are
noted about New Haven, in the Jersey City cut, and in Goat Hill by
Lambertville. Faults are also shown in the Richmond coal field syn-
clinal by W. B. Rogers and Heinrich, and are suspected by Cook in New
Jersey (c, 33). Further observation will surely discover others, either
directly or by means of repeated outcrops. In this latter way a fault
has been determined with a great degree of probability at Beckley,

MUSEUM OF COMPARATIVE ZOOLOGY. 305

Conn. (D); and a similar one, but of much larger throw, very likely
occurs west of Lamentation Mountain, Conn., with uplift on the east,
so that the trap sheets seen in Lamentation and in the Hanging Hills
are really parts of a single overflow. The evidence of this is the repe-
tition of similar series of strata as described by Percival in the outcrop
faces of the two mountains ; in each there is sandstone at the base, then
the amygdaloid of the anterior ridge, next a limestone at the bottom of a
shale, and finally the heavy trap of the ridge line. As shown in fig. 43,
the fault is about three thousand feet. It is obvious that a great sav-
ing is thus made in the thickness of the sandstone: a moderate depth
of formation is made to cover a good breadth of country by its repeated
rising to the surface ; the layers do double duty, and the vast thickness
supposed necessary on the monoclinal theory may be much reduced for
Connecticut at least. Similar evidence makes it very probable that the
same sheet of trap is repeated by faulting and folding southward from
Lamentation Mountain in all the high ridges to that of Saltonstall Lake ;
_but further observation is needed on this point.

We have already stated that the uniformity of dip in direction and
amount has been exaggerated, especially by H. D. Rogers, who wrote
that in the Connecticut valley there is “only one direction of the dip,”
and in New Jersey, Pennsylvania, and Virginia, “ without exception the
strata dip in only one direction” (g, 761; also 670). It was thus that
he was forced to prefer the theory of original oblique deposition. But
this artificial constraint vanishes when we recognize that flat folds with
- faults are perfectly indicated by the curved outlines of the trap ridges,
and by the conformity of the sandstones to these curves; for the trap
sheets that are shown to be overflows at once take the important position
of distinct horizons in the monotonous sandstones and shales, by which
distortion can easily be recognized ; just as the scalloped line of outcrop
of the Medina sandstone reveals the folded structure of the Appalachians
in Pennsylvania.

The conformity of the sandstones to the curved trap ridges is well
known, but has never received its proper explanation. Percival de-
scribed the trap ridges as “arranged according to a peculiar system,
conformably with which the secondary rocks are themselves arranged”
(10). “The trap ranges... . conform, in their arrangement, to that of
the sandstone, and indeed have apparently exercised a controlling influ-
ence on the arrangement of the latter, thus indicating a cotemporary
origin” (321; also 299, 408). He further says that both the general
and particular direction of strike of the sandstone strata agrees with the

VOL. VII. — No. 9. 20

306 BULLETIN OF THE

trend of the trap ridges (450-432). Hitchcock noted the same arrange-
ment for Massachusetts (e, 654; h, 17, and Pl. II.), and Cook mentions
it for New Jersey (c, 29, 32).

An illustration of a flat fold producing a curve may be seen in the
excellent example at Beckley, Conn. (D); it corresponds perfectly with
the much larger curves shown by the Turner’s Falls — Deerfield Range,
by the great range from Belchertown, Mass. to Meriden, Conn., by
many other smaller ranges in Connecticut so well shown on Percival’s
beautiful map, and by several similar curves in New Jersey. The most
instructive region for the further study of this important point in the
structure of the Triassic belts is without doubt the southeastern corner
of the Connecticut sandstone area, about Durham and North Branford, —
Percival’s ‘‘ volcanic focus” (311). I had hoped, but was unable, to
reach it during the past summer.

All these folds are like flat oval dishes, tilted toward and faulted on
the dip side of the general monoclinal ; and as a necessary consequence
of this, the trap sheets that are folded with the sandstones outcrop in
crescentic ridges with the horns of the crescent pointing in the direction
of general dip.* The fact of this position was first published by Percival
in 1842 (311), but its cause was not then perceived. The folds are
very numerous in Connecticut, but in Massachusetts and New Jersey
they are fewer and larger: this would indicate that in the last two States
there is the nearest approach to the simple monoclinal of the third
theory of disturbance. An interesting exception to the rule occurs east
of Saltonstall Lake, Conn.; it is P. 2 of E. I. of Percival’s notation, and
is described as abrupt on its eastern, convex side (325): this makes it
seem very much like the eastern edge of a small sheet whose western
outcrop is lettered P. 1 on Percival’s map. Whether the small curves
in southern Durham lettered P. 1 of E. IIL. are produced by folding, or
result from the original form of intrusion or overflow, or are simply the
effects of erosion, requires further observation to determine. f

In regard to the crescentic form of the trap ridges, H. D. Rogers con-
sidered it natural that the horns of the curves should point with the dip

* The imitation of this erescentic line of outcrop produced at a cross valley is men-
tioned under the observations at Beckley.

t It is greatly to be regretted that Percival had not the facilities for illustration
afforded now by well-executed chromo-lithography. A map of the Connecticut valley
drawn with as full an appreciation of topographic form as Percival must have pos-
sessed, and colored to show the different varieties cf trap and sandstone, is needed to
do justice to the remarkable features of this unique region. There is nothing like it
known anywhere else in the world.

MUSEUM OF COMPARATIVE ZOOLOGY. 307

of the sandstone ; for as a trap sheet made its way obliquely upward be-
tween the layers, the cover of the sandstone must have been cracked at
the ends, allowing the trap to rise there and so turn the extremities of
its outcrop with the dip of the bedded rocks (e). This was agreed to by
Silliman, Jr. Whelpley thought the crescent ridges determined by the
form of the fissures in the old rocks below the sandstones (64). Dana
considered the curved ridges as marking curved fissures, characteristic
of certain eruptions, and further added that the agreement in form of
these ridges with more prominent features of the earth confirms “the
view that ranges of mountains and islands correspond to ranges of
fissures ” (4, 391, 392); but later (4, c, 21) he essentially follows Rogers's
explanation, and further says that the tilting was caused by the subsi-
dence of the estuaries, and is “without evidence of folds” (c, 421).
Wurtz considers that subsidence went on to a small amount during
deposition, and was fastest along the axis of the belt. “Such slight
inward inclination of the beds on both sides of the basin, explains the
crescent form of the edges of the sheets of trap. The flow or propaga-
tion of the metamorphic agent being thus governed.” (102.) Russell
calls the curves “lines of least resistance,” which were naturally and
necessarily chosen by the eruptive trap (c, 241). Cook says, ‘‘ The prin-
cipal changes of dip appear to be, in some unexplained way, connected
with the direction of the trap ridges, and are near them” (c, 29). All
of these explanations, based on the intrusive origin of the trap, fail when
the sheets are found to be overflows.

The value of the overflow sheets as marking horizons in the sandstone
formation is thus very considerable, and will in time lead to closer meas-
ures of thickness than have yet been possible. The peculiar restriction
of the localities of footprints in the Connecticut valley to the strata
along the back of overflows is well shown by Hitchcock in the map in
his Ichnology : it is evidently connected, as he suggests, with the appear-
ance of volcanic islands and shallow waters in the old estuary.

6. SUMMARY.

The Triassic strata were deposited nearly horizontal in narrow estu-
aries not greatly exceeding their present area: some degrees of their dip
may be the result of original oblique deposition, but this is insufficient
to explain all of it. During their accumulation, extensive and repeated
eruptions, very possibly from fissures, poured sheets of trap over their
surface, to be buried under later deposits ; and at the same time, or later,

308 BULLETIN OF THE

large and small trap sheets were forced laterally between the deep-lying
strata. The period of deposition, and probably of eruption, was ended
by an uplift that drained the sandstone areas, and tilted the included
_ strata by small amounts from their original position. Some of the strips
were bent into simple or faulted synclinals (Nova Scotia, Richmond coal
field) ; one was thrown into gentle waves (Prince Edward Island) ; the
others received their peculiar monoclinal tilting. Why the general
monoclinal structure was produced cannot now be clearly explained ;
but by means of the overflow trap sheets, which serve perfectly as iden-
tifiable horizons in the monotonous sandstones and shales, it can be
shown that. there are distinct folds in these monoclinals, thus explaining
the crescentic form of the trap ridges. The folds are of small pattern
in Southern Connecticut ; on a much larger scale in Nova Scotia, Massa-
chusetts, and New Jersey. Faults also occur: some of small throw are
directly visible ; some of much greater displacement are properly inferred
from the repetition of similar series of strata; and many more probably
exist hidden under drift and soil: thus the necessity is avoided of sup-
posing a great thickness for the formation. The erosion of the sedimen-
tary and igneous strata into their present form was probably accomplished
in great part during a time of greater land elevation than the present ;
but it presents nothing abnormal.

The pbysical features of the Triassic belts that seem most worthy of
further observation are, first, a closer identification than has yet been
made of the source of the conglomerates that not unfrequently occur
along either margin of the belts, thus allowing or excluding the ideas of
original oblique bedding and of anticlinal remnants ; second, the deter-
mination of the overflow or intrusive origin of the many undetermined
trap ridges ; third, the further proof that the curvature of these ridges
implies a folding of the strata; fourth, the closer identification of the
surmised but undiscovered faults.

CAMBRIDGE, January 8, 1883.

MUSEUM OF COMPARATIVE ZOOLOGY. 309

EXPLANATION OF PLATES.

Tuis article is accompanied by three plates, numbered IX., X., and XI., with fifty-
two figures, numbered consecutively.

Plate IX., figs. 1-31, gives a general graphic review of the opinions held concerning
the relations of the trap and sandstones from 1818 to 1880. The references to the
originals of the drawings are given on pp. 280, 281.

Plates X. and XI. Sketch-maps serving as guides to the localities of the observa-
tions above described, and figures representing some of the results obtained. Page
numbers refer to explanations in the text.

Fig. 32. Turner's Falls, Mass. Fig. 33. Section of trap ridges (p. 259). Fig. 34.
Fragments of trap in overlying sandstone (pp. 260, 300).

Fig. 35. About Mount Tom, Mass. (p. 261). Fig. 36. Section of Mount Tom and
posterior ridge (p. 261). Fig. 37. Generalized section of contact, Delany's Quarry
(p. 262).

Fig. 38. Railroad cut in posterior trap ridge, West Springfield, Mass. (p. 263).

Fig. 39. Map and section of curved trap ridge at Beckley Station, Middletown
Branch Railroad, Conn. (pp. 264, 265, 306).

Fig. 40. The Hanging Hills from Meriden (p. 265). Fig. 41. The same in section
(p. 266). Fig. 42. Map of the same (p. 266). Fig. 43. The same with Lamentation
Mountain, as seen from Wallingford, Conn., showing place and throw of probable
fault (pp. 266, 305).

Fig. 44. Dikes near East Haven, Conn. (pp. 268, 292).

Fig. 45. Side of ragged dike, Wallingford, Conn. (p. 266).

Fig. 46. Base of Palisade trap cutting sandstone, Weehawken, N. J. (p. 270).

Fig. 47. Garret Rock, First Mountain, Paterson, N. J. (pp. 273,304). Fig. 48.
Gorge at Passaic Falls, Paterson (pp. 272, 300).

Fig. 49. Peculiar conglomerate overlying First Mountain trap, Feltville, N. J.
(p. 275). Fig. 50. a, 6, the same, natural size (p. 275).

Fig. 51. Intruded trap sheets, Martin’s Dock, below New Brunswick, N. J.
(pp. 276, 295),

Fig. 52. Intruded trap sheets, near Point Pleasant Station, Belvidere Railroad,
N. J. (pp. 277, 295).

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PICTORIAL REVIEW

OF THE
SUPPOSED RELATIONS or THE

TRIASSIC TRAPS axon SANDSTONES
FROM
1818 To 1880

ComPILED BY WM. DAVIS.
IBBR

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1858

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No. 10. — Zhe Folded Helderberg LInmestones East of the Catskills.
By Witu1aM Morris Davis.

Introductory. — Previous Descriptions. — Character and Sequence of the Formations.
— Hudson River Group. — Absence of Medina-Niagara Group. — Waterlime and
Tentaculite. — Lower Pentamerus Limestone. — Catskill Shaly Limestone. — Encri-
nal and Upper Pentamerus Limestone. — Oriskany. — Corniferous Grits. — Cornif-
erous Limestone. — Marcellus Shale. — Hamilton and Catskill Sandstones. —'The
Question of Unconformity. — Paleogeography. — Folds and Faults. — The Catskill
Gorge below Leeds. — Other Points for Observation. — Unconformity by Faulting. —
Compression in Synclinals. — Compression in Faulting. — Surface Geology. — Gla-
cial Phenomena. — Stratified Clays. — Former Lines of Drainage.

Tue Appalachian district in Pennsylvania is made up of three well-
distinguished parts: a plateau of nearly horizontal rocks on the north-
west, showing no formation younger than the Carboniferous and Upper
Devonian ; a rolling low country on the southeast, where the rocks are
Lower Silurian and older, greatly folded and often half or wholly crystal-
line ; an intermediate region, where the wave-like folds of the Paleozoic
strata are best developed, and their effect in producing anticlinal, syn-
clinal, and canoe mountains is best seen. If we trace these three belts
northeastwardly into the Hudson valley, the first is well shown in the
broad mass of the Catskills ; the second in the perplexing Taconic region
from the Hudson across to Western Connecticut and Massachusetts ;
but the third, so striking in Pennsylvania, has dwindled to a narrow strip
of insignificant hills, only a mile or two wide, and a few hundred feet in
height. Although so greatly reduced in size, this middle belt still re-
tains its characteristic structure very clearly, and reveals this structure
in its surface forms. The accompanying map represents a part of it
some ten miles in length, the middle point of which is about west of the
town of Catskill on the Hudson. Very little attention has as yet been
given to this belt of miniature mountains, excepting in the study of its
fossils. The following are the only descriptions referring to it that I
have found.

W. W. Mather. Geology of New York; First District. Albany,
1843, pp. 317-352, 366-421. A general description is given of the sev-
eral formations here occurring, their characters and sequence ; but the
structural peculiarities of the district are very imperfectly represented.

VOL. VII.—No. 10.

312 BULLETIN OF THE

E. Emmons. Agriculture of New York. Albany, 1846. Vol. I.
pp. 134-175, and Plates IV., XX., and XXI., bear more or less directly
on the structure of our district.

N.S. Shaler. On the Existence of the Alleghany Division of the
Appalachian Range within the Hudson Valley. American Naturalist,
XL, 1877, 627, 628. A short notice of the extension of distinct anti-—
clinal and synclinal structure to this point.

W. M. Davis. The Little Mountains* east of the Catskills. Appa-
lachia, IIT., 1882, 20-33. <A detailed elementary account of the struc-
ture of a small part of the Helderberg belt ; with map and sections.

No geological maps of this region have been drawn on a large enough
scale to show anything more than parallel strips of color along the west-
ern side of the Hudson valley. The little sketch-map in the last of
the above-named articles, and the map accompanying this paper, are the
first that show the well-marked Appalachian topography of the district.

The material for the present paper was obtained in part during two
short visits in the spring and summer of 1877, the first in company with
Mr. E. R. Benton, now Professor of Natural History in the University
of Rochester; the second with Professor N. S. Shaler, Mr. J.'S. Diller,
and members of the Harvard Summer School of Geology. But a third
trip made in the spring of the present year furnished fuller results ; in
this I was accompanied by Mr. J. E. Wolff, Assistant in Geology, and by
Messrs. Bunker, Chase, Clark, Dean, and Jackson, students in Harvard
College and the Lawrence Scientific School. To all of these I desire to
give thanks for aid in making the observations herein recorded.

Our work was mostly stratigraphical, and some description of part of
the results has already been published in Appalachia, as above men-
tioned. As only a short time was spent on the ground, the reader must
expect to find some points indicated as probable, but not fully estab-
lished ; many of these would afford excellent subjects for detailed sum-
mer studies, and I should be greatly pleased to learn of their being taken
up by residents or summer visitors.

The Silurian and Lower Devonian strata occurring in this part of the
Hudson valley are the Hudson River sandstones and shales in the low
country on the east by the river, and in occasional anticlinal valleys
within the Little Mountain belt ; next, the Lower Helderberg limestones,
‘in good variety and well exposed at many points; over these the grits

* This name was given by the writer to call attention to the peculiarly mountain-
like structure and form of these limestone hills. They are not so known in their own
neighborhood.

MUSEUM OF COMPARATIVE ZOOLOGY. 313

and limestones of the corniferous period ; then the Marcellus shale in a
valley, and the Hamilton sandstones in a line of bluffs limiting our dis-
trict on the west. The latter sandstones or very similar ones continue
to the foot of the Catskill Mountains in low ridges and shallow meadow
valleys. Whatever paleontological evidence might be discovered by de-
liberate observation to justify these subdivisions, the lithological char-
acter is so distinct that fossils are hardly necessary, except in some of
the limestones, for the identification of the several groups. The follow-
ing table shows the sequence and thickness of the strata as described
by several observers here by Catskill and a little farther south near
Kingston.

Grits : Caleareous Matiat| Ritmtns. Lindsey,| Dale, | Davis,
ica Hgritty shales.| 1843. | 1846. | 1879.* |1879.*| 1882.

Oriskany.

Upper Pentamerus and

Encrinal Heavy and

cross-bedded
limestone.

Thin-bedded
Catskil) Shaly. impure shaly 15-20 | 2100 |
limestone.

Lower Pentamerus.

limestone.

(Upper Ribbon. )

i

ibbon. = 3
aa ] Fine-bedded.
Stromatopora. 2 } Sponge-layer.

Tentaculite. Fine-bedded.

Waterlime.

Coralline. >

Shales and

“Y= ] fine sand-

Hudson River Group. [=
: stones.

* As referred to below, page 321.

314 BULLETIN OF THE

The remarkable absence of the Medina-Niagara series of formations
between the Hudson River group and the lowest of the overlying lime-
stones will be discussed farther on. Here by Catskill nothing was seen
that could be surely referred to any of the missing formations ; but
Lindsey and Dale describe six or eight feet of Coralline or Encrinal
limestone that they identify as some member of the Niagara series.
The absence of the Oriskany sandstone is almost as complete.

The formations observed in our sections of the Little Mountains may
be described as follows.

The Hudson River group consists of a great series of fine gray or
brown sandstones and shales, with no layers here sufficiently marked to
be recognized at their probably repeated outcrops. The layers some-
times contain flakes of many-colored clay with the fine sand, implying
an erosion near the place of deposition, and some layers have an uneven
surface like a mud-flow (see fig. 1). Irregular ripple-marks are common,
and in good exposures they may be seen over large surfaces; but we
found no cross-bedding or coarse sandy layers. No fossils were seen :
their absence cannot be ascribed to metamorphism, either mechanical or
chemical, for many of the strata seem very little altered in spite of the
general disturbance. These rocks are well exposed at many points
where they crop out above their usual terrace covering of clays and
sands that are spread over all the low land ; and are also shown on the
creek sections, as on the bank of the Catskill at Catskill Village, where
excessive and irregular plications may be seen (fig. 2); sharp folds,
slickensides, and small faults are very common; and likely enough
faults of larger throw occur, though they cannot be detected. A point
of good continuous, and just now of fresh exposure, is in the railroad cut
on the bank of the Catskill just below Austin’s Mill; a fime dome-like
fold is seen by the stream, and farther on broadly curved surfaces of
rippled shales alternating with firm sandstones dip conformably under
the limestones (fig. 3). Unconformity might well be expected: the
Medina, Clinton, Niagara, and Salina series, about one thousand feet
thick in Western New York and over six thousand in Central Pennsyl-
vania, are all absent here, unless some few feet of nondescript beds may
represent them.* The evidence of conformity and the possible mean-
ings of this absence of formations are discussed farther on.

The beds of passage from Hudson River to Lower Helderberg were
best seen on the road leading down to Austin’s Mill (fig. 3), and at the

* If the shaly layers of the Waterlime are considered equivalent to the Salina,
this must be a little modified.

MUSEUM OF COMPARATIVE ZOOLOGY. 315

north end of the Quarry Hill: they are sandy limestones, without fossils
as far as observed, and not more than five or ten feet thick between char-
acteristic Hudson River sandstones and shaly layers of the Waterlime.

There is no distinction attempted on our map and sections between
the Waterlime and the Tentaculite limestone: all the calcareous layers
below the knotted strata of the Lower Pentamerus are marked by a
single color. Professor Hall (Paleontology of New York, III. 386)
describes the Waterlime as being of “ gray or drab-colored surface and
darker interior color, and almost destitute of fossils”; while the Ten-
taculite is “a thinly bedded blue or black limestone, abounding in
certain organic remains.” These characters are easily recognized. The
total thickness of seventy feet was measured on the eastern slope of the
Quarry Hill, from the uppermost sandstone to the lowest knotted lime-
stone. At Austin’s Mills the measure would be less. The subdivisions
of the Tentaculite, as described at Rondout (see Lindsey and Dale, as
below), are here clearly made out. Some ten feet of fossiliferous lime-
stone are followed by the Stromatopora layer, of one or two feet thick,
with numerous sponges a foot or a foot and a half in diameter (fig. 4) ;
next above come twelve feet of fine Ribbon limestone, in even parallel
layers, shown by alternating bands of lighter and darker color, often as
thin as one twentieth of an inch ; then comes the coarse Lower Penta-
merus, but about ten feet above its base there is a band of Ribbon
limestone again, one or two feet thick. » The even lines and smooth
gray weathered surface of the Ribbon limestone frequently serves as a
well-determined horizon, outcropping on the slope of the ridges made
by the Lower Pentamerus.

The fossils of the Tentaculite limestone commonly seen are a Leper-
ditia, a Tentaculite, Orthis plicata, and a Turritella(?). The first two are
very common on certain layers. The thickness of the Waterlime and
Tentaculite has already been mentioned as seventy feet or less. These
two divisions of the limestone group are well seen — at least their upper
members — at many points along the front of the Kalk Berg, around
the synclinal outlier opposite Austin’s Mill, and at the head of the
southern anticlinal valley.

The change to the coarse, heavy, knotted layers of the Lower Pen-
tamerus is accomplished within two or three feet. With this comes
the frequent occurrence of dark chert in irregular masses up to six
inches in diameter. The fossils easily found are Pentamerus galeatus
(beaks are very common on weathered slopes in the soil) and Atrypa
reticularis: both are common. The thickness measured about eighty

316 BULLETIN OF THE

feet on the eastern slope of the Quarry Hill. The best exposure is on
the Catskill on the first bend above Austin’s Mill, where broad surfaces
of the limestone are laid bare ; it is fairly shown in the ridges or bluffs
all along its outcrop.

The Catskill (formerly Delthyris) shaly limestone is a rather evenly
bedded, thin splitting, impure dull blue rock weathering gray or brown
as its calcareous particles disappear. Fossils are very common, but on
weathered outcrops are found only as casts: the ordinary forms are
Spirifer macropleura, Spiriferina perlamellosa, Streptorhynchus (Hemi-
pronites) radiatus, Strophomena rhomboidalis, Rhynchonella ventricosa,
Eatonia peculiaris, and Pterinea communis.* The thickness of this
division is somewhat under one hundred feet. The best exposure is at
the railroad bridge across the Catskill, three quarters of a mile below
Leeds, and on the banks farther down stream ; but characteristic fossils
are easily found at many points.

The Encrinal and Upper Pentamerus limestones were not separated
in our study, as they constituted a single topographic element ; but it
was readily seen that crinoid stems were more plentiful in the lower than
in the upper layers. The rock is hard, heavy-bedded, and coarse-grained,
consisting of broken shells and crinoid stems; it is well adapted to
heavy masonry ; on some weathered joints, exposed in French’s Quarry,
very clear cross-bedding was seen. Corals make no important share of
these limestones so far as we could discover. The shells recognized were
Pentamerus pseudo-galeatus, Spirifer cycloptera, and many others not de-
termined : they are so firmly held, that it is difficult to break out good
specimens. The thickness of these two members as determined at the
railroad bridge below Leeds is one hundred and twenty feet, but this
may be exaggerated by local faulting. Other observers give it much
less. French’s Quarry and the Catskill bank by the railroad bridge give
good exposures ; and fair outcrops are found at many other points.

These Lower Helderberg limestones as a whole are decidedly harder
than the shaly sandstones below or the grits above them, and are strongly
determinant in forming ridges and bluffs. Among the most marked of
these is the long, continuous ridge at their easternmost outcrop, known
as the Kalk Berg (corrupted into Kalla Barrack ¢), where they are usu-
ally nearly vertical and sometimes are overthrown : other interesting
forms of outcrop appear on the several synclinal and anticlinal folds.

* The names are thus given in the collection in the American Museum of Natural

History, New York.
+ For these local names I am indebted to Mr. Henry Brace of Catskill.

MUSEUM OF COMPARATIVE ZOOLOGY. 317

The subordinate ridge-making members of the group are well shown in
the Quarry Hill synclinal; they are the Lower Pentamerus, the upper
part of the Catskill Shaly, and the Upper Pentamerus ; while the Water-
lime, the junction of the Lower Pentamerus and Catskill Shaly, and of
the latter with the Encrinal, are marked by depressions. These relations
of hardness are pretty constantly shown in all parts of our field, and add
much to the ease of identification of the several subdivisions.

The upper part of the Upper Pentamerus becomes sandy and impure
for about ten feet: this change i8 completed in the occurrence of a six-
inch layer containing limestone pebbles up to an inch in diameter, and
quartz grains of a quarter of an inch or less. Although no fossils were
found in this thin conglomerate, I have considered it as representing the
Oriskany sandstone, as it has the proper place in the series. Mather
and Emmons describe it as half a foot to two feet thick. The best ex-
posure of this layer was found on the north bank of the Catskill at
Leeds, in the vertical strata on the western side of the anticlinal that
shows there in the stream; and again at several points below, as far
down as the railroad bridge.

The Grits which come next are fine-grained, dark gray or bluish, and
generally with all appearance of bedding destroyed and supplanted by
an imperfect, nearly vertical cleavage. Bedding planes are sometimes
found, and generally contain impressions of the Sprrophyton cauda-galli.
Very few other fossils were found in this monotonous formation. Its
thickness is three hundred and fifty feet, when measured by the breadth
of outcrop where the enclosing limestones were about vertical, east of the
limekiln near the junction of Old Kings and the Mountain roads. Other
observers give only a fifth of this thickness. Outcrops are generally
poor, as the rock usually weathers down to a rolling surface of gray
gravelly soil, or is covered by swamps; the lower half of the Grits is
more easily eroded than the upper: the gorge of the Catskill by Leeds
presents on its southern bank an excellent section of the entire forma-
tion (fig. 5), and exhibits perfectly the relation between its true bedding
and secondary fracturing. A small table-rock, over which a little stream
falls on its way to the Kaaterskill west of West Berg, an eighth of a
mile north of the limekiln above mentioned, shows many slabs near the
top of this formation well marked with the cocktail seaweed.

The Corniferous limestone follows the Grits by an abrupt change ; its
layers are often massive, and always of a fine, close grain. Dark horn-
stone is very common in irregular masses often a foot broad ; it is clearly
of secondary origin. Fossils are scarce; the corals so common farther

318 BULLETIN OF THE

west are hardly seen here, but the fine, massive limestone was very pos-
sibly largely derived from a coral reef not far distant. There was no
good place to estimate its thickness; but twenty-five or thirty feet, as
given by Emmons, seems too small. The margins of this formation have
a peculiar way of weathering out into large loose blocks, often ten feet
cube; good examples are seen on. Old Kings road just south of the
Mountain road ; near Van Luven’s Lake ; and north of Hooge Berg. The
last-named point gives a good section of the limestone at its southern
end, and it can be well seen at Leeds’ west of the Grits.

The Marcellus shale follows by a very abrupt transition, as may be
seen at its only exposure, on the east bank of the Cauterskill, just south
of the Mountain road bridge. It is a fine black fissile shale, in which a
few faint fossil shells were found in 1877. Its upper limit and thickness
were not determined, as it is throughout worn down into a valley be-
tween the Corniferous on the east and the Hamilton on the west, and
deeply buried under stratified clays. The Hamilton sandstones and
shales and the overlying formations were not examined closely ; the
lower layers of the former are well shown at the Big Falls of the Kaa-
terskill, where several strata are very fossiliferous ; Sprrifer mucronata
and medialis are both of common occurrence. From the Marcellus val-
ley to the foot of the mountains these and similar, but non-fossiliferous,
sandstones and shales continue with a gentle westerly dip, and their
thickness must amount to over two thousand feet. From the foot of the
mountains to the summits of their broad masses, the strata are essen-
tially horizontal, and may measure about three thousand feet more,
chiefly of sandstones and sandy shales, with some conglomerates near
the top. These are generally accounted of the Catskill formation.
Cross-bedding is common throughout, and in a great part of the Hamil-
ton group.

The most interesting question presented by this series of rocks turns
on the absence of the Medina, Niagara, and Salina strata from between
the Hudson River and the Lower Helderberg formations, and the possi-
bility of unconformity at this point of the section. The following his-
toric review will show what observations have been made and what
views have been held on this subject in the Hudson valley.

W. W. Mather. Report of W. W. Mather, Geologist of the 1st Geologi-
cal District of the State of New York. Albany, 1838. (2d Annual Re-
port.) ‘Mount Bob and Becraft’s Mountain are outliers of limestones,
lying unconformably upon the subjacent slate rocks. I have traced these
rocks within a few feet of their junction in many places.” (p. 165.)

MUSEUM OF COMPARATIVE ZOOLOGY. 319

The same. Fourth Annual Report, 1840. The Hudson River slate
group ‘is overlaid unconformably in many places by the various rock
formations of more recent origin.” (p. 212.) The common and hydraulic
limestones at the base of the Helderberg series ‘‘ sometimes rest uncon-
formably upon the Hudson slate group, as at Lawrence’s quarry, on the
Rondout, opposite Wilbur (see fig. 6, copied from fig. 1, Pl. 26, Final
Report, 1843); sometimes conformably on the Shawangunk grit, ... .
as at Rosendale and Lawrenceville, on the Rondout ; sometimes on the
red and variegated shales and grits that overlie the Shawangunk grits, as
at the High Falls of the Rondout in Marbletown.” (p. 237.) Lawrence’s
quarry is again mentioned (242) as affording “a fine exposure of the
different strata, and the Hudson slates are seen uwnconformable, below
the limestones.” At Hasbrouck’s quarries on Pine Mountain between
Rondout and Kingston Point, the Hudson slate series dips 40-60° to
E. 8. E.; the overlying limestone and cement beds dip 80° W. N. W.,
‘and this dip continues nearly uniform along this line of upheave to the
‘High Rocks’ above Kingston Point.” (p. 242.)

The same. Fifth Annual Report, 1841. There is “a line of fracture
and anticlinal axis” extending northward from New Jersey, passing
Kingston and the district here mapped. ‘On the west side of this axis
of fracture and elevation, the rocks dip to the westward at variable, but
generally at small angles, while on the east side they dip at a high
angle to the eastward, and are frequently vertical in their stratification.”
(p. 64.) Further reference to Becraft’s Mountain is made on page 90;
it is also said that west of the line of fracture ‘the superincumbent
rocks overlie this [Hudson slate] series conformably in most places.”
The several Helderberg outliers known to Mather are Becraft’s Moun-
tain and Mount Bob near Hudson; another in Greenbush, between the
Sandlake and Nassau roads, about two miles from Albany, first examined
by Dr. Eights; and two others described by Eaton, one in the north
part of Greenbush, five miles southeast of Troy, the other in the town
of Schaghticoke, on the north side of Tomhannock Creek (p. 87).

The same. Geology of New York, First Distret, 1843. Most of
the observations are repeated from the Annual Reports, pp. 330-373.
Becraft’s Mountain is described in detail (p. 351) and figured (PI. 24,
fig. 6, here copied, fig. 7); no doubt is expressed of the unconformity
there; but at Mount Bob (PI. 38, fig. 1, here copied, fig. 8) it is said
to be “apparent.” “Although the actual junction of the rocks of
the Hudson River group with those of the Helderberg division was
not observed between Kingston and Catskill, they were seen in many

320 BULLETIN OF THE

places so near/y in contact, and unconformable, as to leave scarcely a
doubt that they were really unconformable” (p. 374) ; and they are so
shown in his section on Esopus Creek (Pl. 7, fig. 9, here fig. 9); the
author suggests that the Hudson series may have been disturbed first
only to the east of the “ anticlinal axis,” and, later, to the west with the
overlying formations (p. 374). But his section (Pl. 38, fig. 14, here
fig. 10) at Catskill shows conformity.

H. D. Rogers. Second Annual Report on the Geological Exploration
of the State of Pennsylvania. Harrisburg, 1838. The sandstone and
conglomerate of IV. (Oneida and Medina) are “displayed near Rondout,
resting wnconformably and with a gentle inclination upon the steeply
uptilted, contorted, and disrupted strata of the immediately subjacent
slates” (p. 37). In Pennsylvania, the conglomerate at the base of IV.
contains fragments of the three earlier formations, showing a violent
physical change ; but no unconformity was noted there (p. 36).

The same. On the Correlation of the North American and British
Paleozoic Strata. Brit. Assoc. Rep., 1856 (178-180). “ Undulated
Matinal rocks support horizontal Niagara or Scalent strata, with a lapse
of two intermediate formations for some distance from the Hudson,
westward along the base of the Helderberg range.” (p. 178.) In the
Mohawk valley, these formations approach conformity, Southwestward
to Alabama there is neither lapse of formations nor unconformity, but
a violent change in the rocks in passing from Hudson River to Medina
strata; the latter contain fragments of earlier formed layers.

The same. Geology of Pennsylvania, 1858, II. (784-787). “From
Gaspé on the Gulf of St. Lawrence, 8. W. to the River Hudson, wherever
the Matinal rocks appear in contact with any of the superposed forma-
tions, the former are either highly inclined and folded, or give evidence
of disturbance and partial metamorphism, while the overlying strata
display much less displacement and alteration.” (p. 785.) Becraft’s
Mountain and Rondout (fig. 11, here copied from Vol. II. p. 785) are
mentioned as points where the unconformity is distinct. It is said to
exist “from Rondout to Schoharie” (p. 785).

E. Emmons. Agriculture of New York. Albany, 1846, I. The sec-
tions in the gorge of the Catskill at Austin’s Mill and at Becraft’s
Mountain are drawn showing.a conformable sequence of Waterlime on
Hudson River layers (his sections 5, Pl. XX. and p. 136, here figs. 12,
13) ; at Rondout, the relation is represented as unconformable by fault-
ing (fig. 17, p. 134, here fig. 14).

James Hall. Paleontology of New York, Vol. II. Albany, 1852.

MUSEUM OF COMPARATIVE ZOOLOGY. 321

“ Along the base of the Helderberg, where the Clinton, Niagara, and
Onondaga salt groups are very thin, the Oneida conglomerate is absent,
and the shales and sandstones of the Hudson River group rise to within a
few feet of the Tentaculite limestone or Waterlime group.” (p. 1, note.)

The same. Palzeontology of New York, Vol. III. 1859. The author
repeats a doubt previously expressed as to the truth of the unconformity
at Becraft’s Mountain, and states that the Upper and Lower Silurians
are conformable on the northern front of the Helderberg Mountains
(p. 33, note). Farther on, he writes: “The Hudson River group, which
constitutes a few feet of their [Catskill Mountains] elevation at the base,
is disturbed, and the succeeding beds lie upon this unconformably ”
(p. 69); and again, “the unconformability of the Lower Helderberg
group upon the Hudson River group” shows that the subsidence of the
old sea bottom was periodical (p. 70; see also p. 88).

These are the older observations on the subject. The following ref-
erences show the recent work, as well as the lack of agreement on the
question in the two text-books in more general use.

J. Leconte. Elements of Geology. New York, 1878. ‘In the United
States, the rocks of the whole [Paleozoic] system are conformable.”
(p. 277.)

J.D. Dana. Manual of Geology. New York, 1880. The making of
the Green Mountains came at the end of the Lower Silurian (211, 212) ;
the disturbance extended to the Hudson (214). Localities of uncon-
formity mentioned are near Gaspé, near Montreal, and at Becraft’s
Mountain (216,* 241). The disturbance is thought not to extend
southwestward of New Jersey (217).

J. G. Lindsey. A Study of the Rocks.. Poughkeepsie Soc. Nat. Sci.
Proc., Il., 1879, 44—48, giving a careful description of the rocks at the
Rondout cement quarries, and regarding the junction of the Upper and
Lower Silurian rocks as unconformable.

T. N. Dale. The Fault at Rondout. Amer. Journ. Sci., XVIIL,
1879, 293-295, from which figure 15 is here copied, showing the Lower
Helderbergs, with a thin layer of Niagara (Encrinal) limestone at the
bottom, lying squarely across the tilted Hudson River strata.

It would seem from this review that Mather and Rogers regarded the
contact of the Upper and Lower Silurians as unconformable on both
sides of the Hudson; Emmons figures a conformable relation, and con-
siders the apparent unconformity at Rondout the result of a fault; Hall
at first admitted the general unconformity, but later doubts it even for

* Here Becraft’s Mountain is wrongly said to be west of the Hudson.
VOL. VII. —No. 10. 21

322 BULLETIN OF THE

Becraft’s Mountain (but not for Rondout?). Leconte, on I know not
what authority, takes a view opposite from the generally accepted one
given by Dana. Lindsey and Dale both represent the junction at
Rondout as an unconformity.

West of Catskill, 1 am persuaded that no unconformity exists: the
evidence for this conclusion is given below. Becraft’s Mountain and its
smaller neighbor I have not seen, except from the railroad in passing:
the opinions concerning this important point are contradictory, Mather
and Rogers being opposed to Emmons and Hall. About Rondout no
disagreement is directly expressed except by Emmons; and yet none of
the observations or figures of the hill-sections in that district are con-
clusive ; none enable the reader completely to exclude the possibility of
the apparent unconformity being really a junction by faulting. It
would seem, therefore, that all this subject needs reviewing.

The observations on which I rely to prove the conformable sequence
of the strata in the district here mapped are as follows : —

First. At the north end of French’s Quarry Hill, by a good spring on
the middle one of the three roads that run around the slope, there is a
contact of sandstone and an impure limestone clearly shown for some
ten feet. The rocks here lie horizontal in the axis of a synclinal fold ;
their strata are closely parallel, and evenly superimposed ; going down
hill several outcrops of sandstone may be found ; ascending to the south,
the several limestones of the Lower Helderberg group are easily recog-
nized in proper order; going east or west, the Hudson River strata soon
rise from the synclinal axis, becoming steeper and steeper by gradual
change.

Second. In the road and railroad cuts just east of Austin’s Mill on
the Catskill, the absolute contact is hidden by about ten feet of detritus,
but the strata show only parallel arcs of the eastern half of a synclinal
(see fig. 3). The apparent unconformity in the limestones here shown
is due to horizontal faulting in the trough of the fold, as is described
farther on.

Third. Along the front bluff of the Kalk Berg, generally marked by
vertical strata of Waterlime and Lower Pentamerus, the sandstones are
also vertical and parallel in strike; in the anticlinal valleys within the
belt, the sandstone is perfectly conformable to the curves of the lime-
stones, but no absolute contacts were found.

We therefore must conclude that the entire series is conformable in
‘this district, and is folded together; and so it is represented on our
sections.

MUSEUM OF COMPARATIVE ZOOLOGY. 323

When the attempt is made to restore the geographic changes by which
the several strata were made to vary, it cannot be denied that this con-
formity is difficult to understand. The sands of the Hudson River group
indicate a return of the shore line on the east after the open ocean con-
ditions of the Trenton formation ;* the shallowing of the waters and the
westward advance of the shore continued certainly as far as the present
line of the Hudson. If the unconformity at Becraft’s Mountain be ac-
cepted, then we may follow the generally allowed belief in the folding of
these sandstones accompanied by their elevation and erosion; and the
very variable composition of the Niagara group as a whole, and the prob-
able changes of level during the Onondaga (Salina) period are most likely
to be explained by the oscillations of the adjoining land on the east dur-
ing the Green Mountain growth. Excepting the few feet of beds found at
the northern end of the Quarry Hill, which were not definitely referred
to any group, there is nothing to be seen in the Catskill section to repre-
sent this vast lapse of time ; for directly and conformably above the Hud-
son River sandstones come the Lower Helderberg limestones, which mark
the second and greater eastward advance of the sea in the Upper Silurian,
the first being that of the Niagara limestones. The present Catskill
district cannot then have been dry land, for it shows no eroded surface
beneath the Lower Helderbergs so far as we could discover. It could
hardly have been far under water, for then it should have received some
share of the various sediments so plentifully supplied to the ocean far-
ther west and southwest. It may, therefore, be best to suppose that our
district lay just off shore, or almost between wind and water, and either
received very little detritus, or else was alternately covered and swept
bare again by shoal water currents, so that in the end it had gained
scarcely any rock material.

The change that followed next was not so much a depression of the
ocean floor as a distant eastward retreat of the shore line ; for the Lower
Helderberg limestones show shallow waters, with freedom from shore
sediments such as the Green Mountain rocks could have furnished. The
Catskill shaly limestone probably marks a slight departure from this
open ocean, and the presence of a neighboring shore, for it contains
much more non-calcareous material than the limestones above and be-
low it.

This second oceanic cycle ends with the Oriskany sandstone, marking
a return of the shore, though perhaps not a very near approach; and

* See Professor Newberry’s ‘‘Circles of Deposition,” &. Amer. Assoc. Proc.,
XXIL, 1873, (2,) 185-196.

324 BULLETIN OF THE

a third cycle culminates in the Corniferous limestone, with deeper water
here than the second. The Marcellus shale, which follows abruptly,
seems too fine-grained and even-bedded over large areas to mark either
a change to shallow water or a neighboring shore ; the disappearance of
the limestone below it was more probably connected with a further
deepening of the water, or with a-change in its temperature. But shal-
low water and near shore conditions came very clearly in the cross-bedded
Hamilton and higher sandstones, and even more distinctly in the Cat-
skill conglomerates.

It is difficult to say what is here meant by ‘shallow water,” for we
know too little of the winds and currents of these old times. But the
meaning of ‘‘near shore” can be estimated from the Catskill conglom-
erates, the coarsest of the entire series here seen from the Hudson River
upwards, and therefore probably nearer their source than any of the
other fragmental strata; and yet the crystalline rocks frém which their
pebbles have been chiefly derived cannot be less distant than the High-
lands of the Hudson (forty miles), the same series of rocks in Connecti-
cut and Massachusetts (forty), or the Adirondacks (sixty miles), for all
the intervening areas, even if then exposed to erosion, were of non-
crystalline rocks. ‘Near shore” does not, therefore, necessarily imply a
very close neighborhood to land ; and the carrying power of the paleozoic
currents must have been very considerable. The identification of the
source of the Catskill conglomerate pebbles is an interesting and impor-
tant piece of work.

Folds and Faults. — The folds of small radius and varying form into
which the above-described strata have been pressed, and the strong in-
fluence of the rocks’ attitude on the surface form, combine to render this
district an excellent training ground for Appalachian work. I know of
no other where so many structural problems are as well shown within so
limited a space. ‘Two well-known features are clearly seen: the folds
become more pronounced in going eastward, and all the anticlinals have
their steeper dips on the west. Points of special interest may be named
as follows.

The Catskill gorge from Austin’s Mill up to Leeds gives a very fine
series of natural sections. The railroad cutting and the lane leading up
from the mill to the turnpike give good evidence of the conformity of
the Hudson River strata under the limestones, and the Waterlime here
presents two interesting forms of distortion. The first is an unconform-
ity by horizontal faulting (fig. 3); the layers have been shoved past one
another on an oblique crack. It is worth noting that a similar style of

MUSEUM OF COMPARATIVE ZOOLOGY. 325

dislocation would probably be called true unconformity if it had taken
place and been laid bare just at the junction of this formation with the
Hudson strata below it; but happening twenty feet higher, it can be
referred to its true cause. Secondly, we may note the effect of internal
disturbance in the limestone, shown by the breaking up of some of its
fine layers (fig. 16): this must be referred to the epoch of general fold-
ing, for examples can be found of all sizes up to a coarse brecciated mass
several feet thick near the fault-unconformity ; it is therefore an example
of what Heim calls folding with fracture, as distinguished from folding
by bending ; and is explained by him as’a folding that took place under
a pressure of superincumbent rocks insufficient to cause plasticity in the
brittle strata.* This fact may some day yield a measure of how many
hundred or thousand feet of rock were xot over the Waterlime when it
was folded, and so lead to a conclusion respecting the former eastward
extension of the Hamilton and Catskill sandstones.

Another conclusion may be noted : the strata showing these crowded
layers lie near the axis of a synclinal trough, where it is often stated
that folding produces tension, not compression. Scrope, for instance,
compares folded strata to a bent board, which of course is stretched on
its convex side.t Such a comparison is incorrect. None of the deep-
lying rocks can escape compression during their folding: this can
happen only to the superficial strata of the anticlinals. That synclinals
are actually compressed, and not stretched, is shown by the growth of
subordinate folds often found in their troughs ; by the cleavage of slaty
rocks at such points; and in general by the thickening of (argillaceous)
strata at the turns and the thinning at the shanks or tangents of the
folds, as was long ago pointed out by Sir James Hall,{ and lately
confirmed by Heim.§

Across the stream from the mill is a well-formed synclinal outlier
(see Emmons, Pl. 1V.) capped with Lower Pentamerus and perhaps with
some Catskill Shaly limestone. Farther up the gorge, where the stream
turns to the rock-strike, there are excellent exposures of Lower Pentam-
erus on the eastern (left) bank, and of Catskill Shaly opposite; the
latter dips gently to the west at this point, but following it one third
of a mile south, it becomes steeper, and at last is overthrown so as to
dip 50° to the east. Above the next band, about at the middle of the
west-east course of the stream, on the north bank, a distinct fault may

* Mechanismus der Gebirgsbildung, 1878, II. 31.
+ Volcanos, pp. 51, note, 289.
¢ Edinb. Phil. Trans., VII., 1815, 97. § Loc. cit., II. 48.

326 BULLETIN OF THE

be seen at the side of the railroad. The plane of the fault dips 45°
east ; on the western side, the Upper Pentamerus has a smooth, well-
rubbed wall; on the east, the Catskill Shaly ends more unevenly, and
supplies a quantity of fragments for the two feet of fault-breccia. There
is no noticeable contortion of strata on either side. This example is
interesting as it is a violation of the so-called “law of faults,” (which I
believe is no law at all,) for the upthrow overlies the hade. In this
particular it confirms the hypothetical attitude of the fault-planes as
generally drawn in Appalachian sections by Lesley and others, although
these seldom if ever depend on direct observation. The example is
further of use in showing that the fault may result from the same com-
pressing force as the fold; and not from horizontal tension, such as is
needed for the so-called normal fault. The throw here on the bank is
probably fifty or seventy feet ; it could be closely measured by more
leisurely observation. We succeeded in finding the apparent continua-
tion of the same fault half a mile to the north, but the intervening
details of the map need revision. On the next turn of the stream by
the railroad bridge, the upper limestones are finely shown on the east
bank ; on the other side, an obscure fold or fault complicates their
succession. The grits and the thin Oriskany layer in the gorge at
Leeds have already been mentioned.

A cross-fault probably determined the gap on which the Kaaterskill
turns eastward from the Marcellus at the saw-mill ; for the folds do not
correspond on the two sides of the gap, and the vertical limestones of
West Berg seem displaced where they reappear on the north.

Other points of interest are as follows, beginning at the north end of
the map :— Black Lake and a high hill next west of it; the hill is a
saddle of grits on a limestone anticlinal; a rare occurrence. Canoe
Pond and the steep plunge of the limestone under its eastern side. A
Corniferous arch on either side of a little cross valley through which the
railroad passes south of Leeds. The Quarry Hill synclinal and the
Fuyk Valley anticlinal. The long tongue of Corniferous running down
to Van Luven’s Lake, and the large loose blocks of limestone at several
points along it. The southern anticlinal valley, and the narrow faulted
grit synclinals to the east of it. The way in which the several lime-
stones wrap around the disappearing anticlinals is beautifully shown.

Surface Geology. —Glaciated rock surfaces are very seldom seen
within the Little Mountain belt, but this is merely because the rocks
are generally too weak to hold them. The firmer sandstones of the
Hudson River group to the east show them abundantly, as on a large

MUSEUM OF COMPARATIVE ZOOLOGY. 327

knob of rock alongside of the Mountain road in the village of Catskill
just west of the stream; its steep northern slope gives a good small
example of an overhanging polished surface. The only case of glacial
action noted on the limestones was on the western side of the Cornifer-
ous anticlinal, where the Kaaterskill has recently cut away the pro-
- tecting clays, just south of its cross valley by the saw-mill: these striz
are very well preserved; they run horizontally along the steep lime-
stone stratum, parallel to the valley. The Hamilton and Catskill sand-
stones west of our limestone belt preserve many and distinct scratched
surfaces: the largest of these was found on a bare even bed of rock on
the Mountain road at a four-corners, about half-way from the Marcellus
valley to the foot of the long grade; they bear 8S. 20° W., and some
are continuous for fifty feet. A little farther west the same direction
is repeated, and with it there are many straggling scratches turning to
S. 60° W. On the mountain road ascending to Beach’s Mountain
House, about half-way up its long grade, the scratches run S. 25° W.,
parallel to the mountain face. On the new road leading from the
Kaaterskill Hotel eastward across the plateau to South Mountain, the
freshly uncovered sandstone ledges show very distinct Stosssetten, indi-
cating an ice-overflow from the Hudson valley across the mountain and
up the Palenville clove ; the directions of ice-motion, here clearly deter-
mined by the form of rock-surface and the well preserved scratches,
were N. 80°, 75°, 50°, and even only 35° W., giving a westward deflec-
tion from the main valley of more than a quadrant.*

The general absence of drift over the limestone belt and the sand-
stones to the foot of the Catskills is noteworthy ; largely on this absence
depends the clearness of the topography of the region. There are no
sheets or mounds of till or gravel ; everywhere but in the deeper valleys
the country rock comes close to the surface and appears in abundant
outcrops ; 4nd the drift is recognized only in scattered stones and boul-
ders of northern origin: in French’s quarry there is, for example, a two-
foot boulder of garnetiferous granite, presumably from the Adirondacks.

There is no clear evidence of any marked effect of glacial action on
the topography, unless we place the little Black, Canoe, and Van Luven’s
lakes here; but they are small, and probably very shallow, and quite
as likely the result of drift obstruction as of ice excavation: they all
occur on the lower part of the grits, where these join the Upper Pentam-

* This deflection has been observed by Mather, 1843, 203; Ramsay, Quart.
Journ. Geol. Soc., XV., 1859, 208; and Julien, N. Y. Acad. Sci. Trans., 1881,
24-27.

328 BULLETIN OF THE

erus, and this as we know elsewhere shows a tendency to valley form.
We had not time to study the origin of the basin of Green Lake, the
largest of the district.

The large blocks of Corniferous limestone, weathered loose along its
margins, may be mentioned again here. The best examples are on the
Old King’s road where it joins the Mountain road; several of the
blocks are eight or ten feet cube. They cannot be considered simply as
glacial boulders, for they occur only along the disappearing margins of
their formation ; they cannot be of pre-glacial weathering, for the ice
stream that filled the Hudson valley till it overflowed its mountain
boundaries east and west can hardly have left any loose blocks so near
where it found them. So we are forced to consider them largely the
product of post-glacial weathering, mostly by solution; but this gives a
so much greater measure of post-glacial erosion than is generally found,
that it is not satisfactory. Some of the blocks are separated from one
another and from the still continuous bed out of which they seem ‘to
have weathered, by a hundred feet or more. The limestone would
therefore have to be easily dissolved by surface waters, although it is
very dense physically; and yet the same limestone under the clays of
the Marcellus valley, where much water must have filtered in along the
contact of rock and clay, has not lost its glacial scratches. The case is
not satisfactorily explained. |

All the lower valleys are occupied by stratified clays capped with
sands up to about one hundred and fifty feet above the Hudson (tide-
water). Near the river, the area and often the depth of these clays are
very great ; they cover all but the higher sandstone ridges, which crop
out as rocky islands. Farther back from the river, the clays fill the
depressions among the limestones, as is nicely shown in the Fuyk, when
viewed from the Lower Pentamerus cliff on the east; and the long
valley cut on the Marcellus shale, where it is followed by the Kaaters-
kill and far north and south as well, is deeply buried under the clay
terraces.

It is easy to see that, if the clays were stripped off, and the country
elevated several hundred feet as it has been in the past, its valleys and
drainage would be considerably changed from their present arrangement ;
but just what these changes would be is difficult to say. I think it
probable, however, that the Kaaterskill would leave the Hamilton a
little to one side of its present course at Big Falls; that both the Kaa-
terskill and the Catskill would run along the Marcellus valley at a
lower level than their present beds, and would escape eastward by some

MUSEUM OF COMPARATIVE ZOOLOGY. 329

channel farther south than our map extends. If this view is correct, it
follows that Big Falls, like so many other cascades in New York and
other glaciated States, result from an old stream’s taking a new course
(L believe this to be a general explanation for many falls); that the
Kaaterskill now makes its way through the Little Mountains over‘a
broadly open pass that once led from the Hudson to the Marcellus
valley ; that the Catskill, although larger than the Kaaterskill, was
accidentally turned into a smaller cross-valley, which it has since deep-
ened somewhat into the appearance of a gorge. Such disturbance of
pre-glacial drainage is a very common occurrence in our Northern regions,
and often gives rise to lakes.

Further study is needed to learn the features of the Helderberg
folds as they extend northward to the south line of Albany County,
where Mather (1843, 335) says they end, and to show their increase
to the south.

Since writing my article for Appalachia, several months ago, an excur-
sion to the mountains in Central Pennsylvania has given me new reason
to repeat what was then said concerning the advantages of the Little
Mountains for studying the elements of topography ; for in Pennsyl-
vania the structural features are on so much vaster a scale, that days
are there required for what can be seen much more clearly in a few hours
near Catskill.

This article is accompanied by two plates, numbered XII. and XIII.
Plate XII. contains sixteen figures, described in the text.
Plate XIII. is a colored map showing the district here described.

CAMBRIDGE, January 15, 1883.

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DIAGRAMS

THE HELDERBERG ROCKS

IN AND NEAR

GREEN COUNTY, N.Y.

FROM VARIOUS AUTHORS & ORIGINAL DRAWINGS

by

W. M Davis
1882

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