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Bulletin of the) Museum of Comparative Zoology,

/

AT HARVARD COLLEGE.
WHOLE Series, Vou. VII.

(GeoLoaicat Series, Vou, I.)

AZOIC SYSTEM

AND ITS PROPOSED SUBDIVISIONS.

BY

J. D. WHITNEY anp M. E. WADSWORTH.

CAMBRIDGE:

PRINTED FOR THE MUSEUM.
Avueust, 1884.

TABLE OF CONTENTS.

yO a

SyNOPSIS OF THE EVIDENCE ON WHICH THE Rocks oF THE AzoIc

The

SYSTEM HAVE BEEN VARIOUSLY GROUPED INTO Distinct Divisions
BY AMERICAN GEOLOGISTS.

CANADA.

** Metamorphic Series” of Locan, as defined by him in the Report of 1845-46,
331; his two divisions of the same, based only on theory, 332; his description
of the Metamorphic Series on the north shore of Lake Superior, in the Report of
1846-47, 333; Hunt's subsequent misrepresentation of Logan’s views, 334.
Murray's description of the formations of the Kamanistiquia Basin, 334; the
two series of rocks subsequently known as the Laurentian and Huronian shown
by him to be conformable, and to pass imperceptibly into each other, 334; this
fact not mentioned by Hunt in his account of Murray’s Report, 334. Murray’s

description of the rocks on the north shore of Lake Huron, Report of 1847-48,

335. LoGan’s description of the same, in 1848, 335, 336; he confuses the
Azoic rocks of Lake Huron with the Paleozoic of the south shore of Lake
Superior, 336 ; Hovucuron’s views misrepresented by Logan, 336. Murray,
in Report for 1848-49, again describes region north of Lake Huron, 337.
Loan, in 1852, calls these rocks Cambrian, 337. In the Report for 1852-53,
published in 1854, Locan gives the name “Laurentian” to the rocks pre-
viously designated by him as ‘‘ Metamorphic” or Cambrian, this name being
the equivalent of the term Azoic, previously introduced by Foster and Wuir-
NEY, 337, 338; the term ‘‘ Huronian” first used, by Hunt, in 1855, 338 ; the
Huronian said by him to be unconformable with the Laurentian, 338 ; this an
error, based on the confounding, by Logan, of the Azoic of Lake Huron with
the Paleozoic of Lake Superior, 338. First mention of the Huronian in the
Canada Reports, 338, 339. The relations of the Laurentian and Huronian indi-
cated in Report for 1856, 339; relation of the hypersthene rock, since called
“ Norian,” indicated by Hunt, 1855, and again in 1856, 339. Division of the
Azoic into Laurentian and Huronian, and the name Laurentian opposed, and
LoGan’s entire misconception of the geology of Lake Huron and Lake Superior
pointed out by Wuirney, in 1857, 340; LoGaN recognizes his mistake, but
does not abandon the terms introduced by him, 340; further statements of
LoGAN (1857) in regard to the Laurentian and Huronian, 340,41 | peculiar

lv

TABLE OF CONTENTS.

logic of his statements indicated, 341. Brespy points out that the Huronian is
distinct from the Cambrian and conformable with the Laurentian, 341, 342.
LoGAn’s statement, in the Report for 1863, that the Laurentian rocks had
been shown by the Canada Survey to be metamorphic sedimentary, controverted,
342. The relation of position of the Laurentian and the Huronian discussed,
343, 344. In the Report for 1863, LoGAN abandons the idea that the copper-
bearing rocks of Lake Huron and those of the south shore of Lake Superior are
of the same age, 344. Hunvt’s views, set forth in the same Report, as to the
sedimentary character of the labradorite rocks in the Laurentian, 344. Macrar-
LANE, in the Report for 1863-66, describes’ the contact of some supposed
Huronian with the Laurentian, on north shore of Lake Superior, near Michi-
picoten Island, 345 ; his observations show that both formations are eruptive,
and of the same age, 346. Hunt, in Paris Exhibition Report of 1867, claims
that the Laurentian comprises two distinct sets of rocks, unconformable with
each other, 346. RicHarpson, in Report for 1866-69, on the Laurentian of the
Lower St. Lawrence River, 346. Manrcovu says that the Laurentian is a mix-
ture of the Upper Taconic with the “‘ Triassic of Lake Superior,” 347. Brwt,
in the Reports for 1871-72 and 1872-73, points out the conformability of the
Huronian and Laurentian in the region northwest of Lake Superior, 347, 348 ;
SrLwyn thinks this apparent conformity only local, and that there is really a
very considerable break between the two formations, 348. SELWyN’s views
shown to have no basis of fact, 348. G. M. Dawson’s and BELL’s observations
in the same region, 349 ; their views criticised and commented on, 349. BrLL,
in the Report for 1877-78, shows that the Laurentian and Huronian are con-
formable in the Hudson’s Bay region, 349, 350.

First mention of the Hastings series, by Murray, in Report of 1852-53, 350 3

the same discussed by MAcFARLANE, in Report of 1866, also by Locan, in
says that it is conformable with the Laurentian, 350; Hunr says that the
Hastings series is overlain unconformably by the Upper Laurentian, 350.
VENNOR gives two entirely different sections of the Hastings series in 1867,
and in the Report for 1866-69, 351 ; his views as to the relations of this series to
the Laurentian and Huronian, 352-354. Hunt, in 1869, refers the Hastings
series to the Laurentian, 350 ; in 1870, to the Terranovan, this being regarded
as in part Potsdam, 354, 355 ; Hunt, in 1871, says that the Hastings series is
conformable with the Laurentian, 355; later in the same year, that it is not,
355 ; in 1875, he says that the Montalban or Hastings series occupies a position
between the Laurentian and the Trenton, 356 ; in 1878, he refers the Hastings
series to the Lower Taconic, and misstates the views of Logan and Bell in
regard to its conformability with the Laurentian, 356. SELWYN announces very
different views fromm those of Hunt, and shows up something of the prevail-
ing confusion in Canadian geology, 356-359. MAcFARLANE, 1879, objects to
Selwyn’s views, 359 ; J. W. Dawson asserts his disbelief in the results of the
Canada Survey, as bearing on the age of the Hastings series, 359.

NEW BRUNSWICK.

J. W. Dawson, in 1855, refers the rocks in the vicinity of St. John to the Lower

Carboniferous, and in 1861 to the Devonian, 360 ; MArrHew divides the same

TABLE OF CONTENTS. Vv

rocks into six groups, and refers to Devonian, Silurian, Laurentian, and Hu-
ronian, 360-362. Baitey, Marrurew, and Harrt, in 1865, give their views
of the age of the rocks of Southern New Brunswick, 362, 363. BatLey and
MAtTrHEw again, in the Report for 1870-71, express their opinions of the
sequence of these rocks, 364; numerous changes made, to conform with the
views of Hunr based on lithological considerations, 364 ; confusion thus intro-
duced, 364-366 ; faults and overturns imagined in order to sustain these new
views, 367 ; an easy explanation of the difficulties, 367. Further confusion and
shifting of the various groups from place to place by Marruew and Baitry, in
the Reports for 1876-77 and 1876-78. tus, in the Report for 1876-78,
describes rocks as Laurentian and Devonian, which in 1865 were called Devo-
nian, and in 1871 Huronian. Further changes, and the St. John group placed
in the Cambrian, in the Report of 1878-79, by Marrurew, Batvey, and Ets,
868. BartLey’s view of New Brunswick geology, in 1880, 368, 369. Hwnv, in
1878, presents his views of New Brunswick geology, mingling his own ideas with
those of Bailey and Matthew, and disregarding the sequence of time in which
these were presented, 371; resulting confusion, 371; impossibility of har-
monizing Hunt's views, as expressed in 1870, with his subsequent explanation
of them, 372 ; a tabular statement of Hunt’s views as expressed by him in 1870,
and as that expression was explained by him afterwards, 372 ; remarks on the
value of the work thus done, 372. Marraew and BarLey misrepreserited by
Hunt in 1879, 373. The rocks of Southern New Brunswick declared by Hunt,
in 1875, to be Huronian and Montalban, 373. Various views of the New
Brunswick geologists, so far as the same can be deciphered, presented in tabular
form, 374.

NOVA SCOTIA.

Hinp, in 1870, indicates the presence of Huronian and Laurentian in Nova Scotia,
374, 375; J. W. Dawson regards the Laurentian gneiss of Hind as being
intrusive granite, 375; SeLwyn differs from Dawson, 375 ; SELWyYN’s views
criticised, 375 ; Hunt considers the Huronian of Hind to be Montalban, 376 ;
HoNEYMAN’s views, which seem to be valueless, and are objected to by J. W.
Dawson, 376 ; HartLey’s opinions of rocks of Cape Breton, and some sugges-
tions in regard to them, 376 ; Rogs’s examination of the same region, in the
Reports for 1873-74 and 1874-75, 376; SeLwyy’s commentaries on Robb’s
work, 377 ; great change in SELWyy’s views since 1871, 377. Further state-
ments by J. W. Dawson, in 1878, 377. The condition of the question summed
up, 378.

NEWFOUNDLAND.

Reconnaissance by JUKES, in 1839-40, 378. Murray, in the Report for 1864,
recognizes the Laurentian, and gives a table of the formation occurring in New-
foundland, 379. Inthe Report for 1868, Muxray introduces an Intermediate
system, supposed to be the equivalent of the Cambrian and Huronian, 379 ;
supposed fossils in this series, 379 ; these rejected by the paleontologist of the
Survey, 379 ; further discoveries of supposed fossils in these rocks, 380 ; Mur-
RAY, in the Report for 1873, presents reasons for dividing the Laurentian into
two groups, 380 ; the real state of the case, 380.

vi TABLE OF CONTENTS.

LABRADOR.

PACKARD’s observations in 1865 ; he recognizes there, on very inadequate evidence,
the Laurentian and Huronian, 381 ; labradorite rocks seen, apparently eruptive,
but called by him Norian, 381 ; Hinp refers the rocks of Labrador to the Lau-
rentian on lithological grounds, 381 ; W1iLKINs holds the same views, calling a
dike Norian, 382.

MAINE.

Geological Survey under C. H. Hircucock developed nothing of value in regard to
the Azoic rocks, 382 ; Hunt infers that the mica schists and gneisses of Maine
are of Montalban age, and that the rocks near Portland are Huronian, and older
than the gneisses, 382; C. H. Hircucock hoids exactly the opposite view,
382. No evidence whatever in regard to the age of the crystalline rocks in Maine
other than lithological, 383.

NEW HAMPSHIRE.

Hunt, in 1847-48, in 1863, and again in 1867, refers the rocks of the White Moun-
tains to the Devonian, 384; Lrestey does the same, and claims for the range a
synclinal structure, 384; his probable error, 384; Hunt, in 1878, says that
Logan considered the White: Mountains as Devonian, omitting to state the fact
that he himself had repeatedly published the same opinion, 384 ; Hunt, in 1870,
called the White Mountains Terranovan, which he considered as being in part of
Potsdam age, 384. C. H. Hircucocr’s first scheme of the rocks of New Hamp-
shire, in the Report of 1869, in which most of them are referred to the Quebec
group, 385; another arrangement, in the Second Report, for 1870, 385, 386 ; in
the Third Report, 1870, the White Mountains are called Eozoic, which “‘ satis-
factory reference” is said to ‘‘clear up the obscurities of New Hampshire
geology,” 386; further changes, in Report for 1871, and introduction of the
Norian, ‘‘the prevalent opinion in regard to the age of the New England meta-
morphic rocks must be changed to conform to the discovery of labradorite in our
State,” 387 ; Hawes, however, regards the labradorite rock as eruptive, 387 ;
Hunt, in 1873, accepts the Norian ; but, in 1878, says that it is found to be of
eruptive origin, 388 ; C. H. Hrrcucock, in 1872, endeavors to prove that the
Norian rocks are of sedimentary origin, 388 ; further remarks to the same effect
by C. H. Hircucock, in various papers published in 1871-72, 389; also, in
Final Report, Vol. II., in which we are told that “the facts as interpreted [in
reference to the Norian or Labrador system] are of great consequence, since they
fix the geological horizon of the whole Atlantic system,” 389, 390 ; later on in
the same volume, all that had been said of the Labrador system taken back,
the rocks recognized as being eruptive, and the exposures on Mt. Washington
formerly considered as stratified now called ‘‘injected dykes,” 390. C,H.
Hrircucock, in the Report for 1872, assigns the Quebec group to the Huronian,
the Concord granite said to be sedimentary, 391; the same author presents,
in the Report for 1872, a classification of the rocks of New Hampshire (see
Table), 391, 392; ‘‘ granite flowed over the country like water,” 392; ‘* ten
distinct periods traced on the scarred sides of the White Mountains,” 392 ;

TABLE OF CONTENTS. Vii

C. H. Hrrencock demonstrates the importance of mineral characters in the
elassification and identification of rocks, 393; the rocks of New Hampshire
classified on that basis, 393; Hunr called on by C. H. Hitchcock to decide
which way the porphyritic gneisses dip, 394; Hunrineron points out facts
indicating that the Concord granite is intrusive, 394; C. H. Hrrcucock states
his views in Final Report, Vol. II., in regard to the importance of not ‘‘ obscur-
ing observations” by ‘‘individual speculations,” 394, 395; some results of
investigations made to ascertain how far C. H. HircHcock was able to distin-
guish and properly name rocks, 395-397 ; authenticity of specimens examined
by us, 397 ; notice of our tabular view of the classifications presented at various
times by the New Hampshire Survey, under C. H. Hircucock, 397, 398.

EASTERN MASSACHUSETTS.

S. Gopon’s observations in 1807-8, 398; his division of the formations in the
vicinity of Boston, 398-400 ; Mac.ure’s geological map, 400; error of Hunt
in describing Maclure’s work, 400; J. F. and S. L. Dana’s contribution to the
geology and mineralogy of the region near Boston (1818), 401, 402; Earon’s
Index to the Geology of the Northern States, 402; Tuomas Cooper, 1822,
recognizes the volcanic character of some of the rocks near Boston, 403 ; Hircu-
cock’s first publication (1824) in regard to geology of Eastern Massachusetts,
403 ; Hircucock contributes to the geology of the same region in Eaton’s Survey
of the Erie Canal, 403, 404. J. W. Wester, 1824-25, publishes Remarks on
the Geology of Boston and its Vicinity, 404. Hrrcucock’s Report, 1833, and
his theoretical views as set forth in that volume, 405-409; his final report,
1841, 409, 410; his theories set forth and commented on, 410. Prescort’s
geological investigations in Essex County 839), 410.

Hunt, in 1854, refers the limestones of Eastern Massachusetts to the Devonian, 411;
he states, in 1861, that he recognizes in New England or Southeastern Canada
‘nothing lower than the Silurian,” 411. Discovery of fossils near Boston, and
recognition of the locality from which they came, 411; various statements as to
the dip of the rocks from which these fossils came, 411, 412 ; Hunt, in 1866,
on the limestones of Eastern Massachusetts, considering it doubtful whether
they may not be Laurentian, 412 ; C. H. Hircucock, 1867, considers the gneiss
and hornblende schist of Andover to ‘‘belong to the Eozoic ages,” 412; his
reported facts doubted, 412. Hunr, in 1869, describes the granite of New Eng-
land as being a sedimentary rock, and containing traces of fossils; in 1870 he
says that the granites of Cape Ann and Quincy are ‘ probably intrusive” ; in
1873, that the granites of Rockport are “distinctly eruptive,” 413 ; necessary
physical conditions resulting from Hvuwnt’s theories, 413; BricKNELL finds
Eozoon in limestone at Newbury, 413, 414; Hunr considers this proof of the
Laurentian age of these rocks, 414.

SHALER, in 1869, considers the stratified origin of the syenites of Eastern Massachu-
setts clearly proved, —the syenite being seen to pass into ‘‘ unquestionably
sedimentary rock,” 414; his geological observations shown to be incorrect, 414.
Hunt, in 1870, considers the finding of the Eozoién at Chelmsford, and its
identification by Dawson, as proof of the Laurentian age of the limestones of that
region, 415 ; Hunt, in 1870, refers the gneiss of Eastern Massachusetts to the

Vill

TABLE OF CONTENTS.

Laurentian, and the diorites and porphyries to the Cambrian, which he then
considered the equivalent of the Huronian, 416 ; he also says that the presence
of the Kozoén ‘‘can no longer serve to identify the Laurentian system, 416 ;
Hunt, in 1870, further discusses the geology of Eastern Massachusetts, 416,
417 ; comments on the views there expressed, 417, 418. C. H. Hircucock, in
1871, publishes a geological description of Massachusetts, 418; some of his
errors pointed out, 418. Hunt, 1871, refers the felsites of Eastern Massachu-
setts to the ‘‘ great Huronian system,” 418.

Hyatt, in 1871, considers the porphyries of Lynn and vicinity to be metamorphic

sedimentary rocks, 418, 419; Hunt, in 1871, takes a similar view, referring
these porphyries to the Huronian, and ‘‘ the limestones, with Eozoon from East-
ern Massachusetts,” to the Laurentian, 419 ; some comments on Hunt’s method
of misrepresenting statements previously made by himself, 419, 420; Hunr
again, in 1871, holds that the gneisses and limestones of Eastern Massachusetts
are Laurentian, 420. Dopen’s classification of the rocks near Boston, 420, 421.
Bouvé, in 1876, considers the felsites to be derived from the metamorphosis of
the conglomerates, 422; these views supported by Hyart, 422, 423. Crospy,
in 1876, divides the ‘‘ Eozoie rocks” of Massachusetts into Norian, Huronian,
and Mont Alban, considering these divisions ‘‘as both lithological and chrono-
logical,” 423; the same statement affirmed in 1880, 423, 424; extraordinary
nature of the views here advocated, 424; errors in CrosBy’s determinations of
the rocks, 424. CrosBpy maintains that granites are derived from sedimentary
rocks, 424; his mistakes as to the real character of the Rockport granite, 425 ;
he considers the felsites near Boston to be of sedimentary origin, 426, 427 ; his
ideas in regard to the Huronian, 427 ; in regard to the argillite and conglomerate
near Boston, 428. WaApswortn’s investigations, in 1877, of the dikes near
Boston, 428 ; in 1878, of the Rockport granite, 428. CrosBy, in 1879, advo-
cates the theory that the felsites are of deep-sea origin, or made of the red clay
deposited at the bottom of the ocean, 428, 429. WaApsworTH studies, in 1878-79,
these felsites, in the field and microscopically, and makes them out to be old
lavas, 429 ; the felsites seen by him in the form of dikes, 429. DILLER, in 1880,
makes an exhaustive investigation of the felsites north of Boston, and confirms
in all respects Wadsworth’s views, 430, 431; his field of work and collections
carefully examined by the authors of the present paper, and the accuracy of his
results testified to, 431. Crospy, in 1880, designates what he previously had
called une ‘* Norian ” as the ‘‘ Naugus Head series”; this he considers the real
base of the geological column in Massachusetts, 431, 432 ; WApsworTH finds the
Naugus Head series to be of similar character to the zircon syenite of Norway ;
Crosby's views shown to be incorrect, 432, 433. CRosBy’s ideas in regard to
the Huronian in Eastern Massachusetts, 433-435 ; his views criticised, and his
reported facts shown to have, in many instances, no other basis than his own
inability to distinguish between different rocks, 436.

SHALER, in 1879, maintains that the shales and conglomerates of Roxbury pass into

the amygdaloidal melaphyr, 437 ; his theoretical deductions, made in accordance
with this view, 437 ; BEnrTon, in 1880, controverts these views, and shows that
the melaphyr is an old, altered basalt, 437. Discussion in regard to the plas-
ticity of the pebbles in the conglomerate, 437, 438 ; opposite views of CrosBy
and WapswortH, 488 ; the spindle-shape, into which CrosBy thought that the

TABLE OF CONTENTS. ix

pebbles had been squeezed or pulled, shown to be only the result of his mis-
taking the enclosing matrix for the pebbles, 438. Dopnce, in 1881, gives
details of his observations near Boston, noticing the occurrence of felsite dikes in
the granite, as had been before shown by Wadsworth and Diller, 439. Waps-
WorrTH, in 1881, calls attention to more of Crosby’s errors of observation, 439.
WaAbswortTH, in 1883, points out the relations of the Roxbury conglomerate to
the argillite, 439. Dopce, in 1883, claims that there are two granites in the
Quincy district, but offers no evidence in support of this view, 439, 440.
Errors of SHALER, Rocers, and JACKSON, in regard to the argillite and granite
pointed out by Wadsworth, 440.

VERMONT AND WESTERN MASSACHUSETTS.

Small progress made by the earlier investigators toward unravelling the intricate
problems presented in this region, 440 ; a specimen from Hrrcucock’s Final Re-
port, 440. H.D. Rocers’s division of the rocks below the ‘‘ Cambrian or Older
Silurian” into azoic and hypozoic, 440, 441; this classification has no basis of
fact, 441 ; he says that it is absolutely impossible to determine ‘‘ the true base of
the Paleozoic system,” 441. Importance to New England that the work of the
Canada Survey should be well done, 441. First published statement of the bear-
ing of the results of that survey on the solution of problems in New England
geology, by Hunt, in 1849, 441, 442 ; the whole of the Green Mountain rocks
said by him to belong to the Hudson River group, 441, 442. “‘ With sucha key
to the structure of the metamorphic rocks of New England, and of the great
Appalachian chain,” Hunt thinks that ‘‘the difficulties that have long environed °
the subject are in a great degree removed, 442; similar views expressed by
Hunt, in 1850, and Emmons’s views of the age of the Taconic entirely rejected,
442; again, in 1854, Hunt refers the crystalline limestones of New England and
their continuation southwest to the Lower Silurian, 442, 443; in 1861, and
again in 1863, similar views were expressed, 443 ; in 1866, Hunt said that the
Quebec group ‘‘constituted the great metalliferous region of Eastern Canada,
Vermont, and Newfoundland” ; he also refers the cupriferous rocks of Lake
Superior to the same group, 443 ; in 1867, he repeated the same statement. con-
sidering the Quebec group as being the equivalent of the Landeilo, and further
remarking that this group formed the Notre Dame and Green Mountains, and
that it “ played a very important 7éle throughout the Appalachian chain,” 443 ;
this all repeated again later in the same year, 444; the statement also repeated
that the White Mountains were of Devonian age, 444; again, in 1868, it is
asserted that there is no proof of the existence in Vermont of any strata older
than Potsdam, the gneiss of the Green Mountains being referred to the upper
portion of the Quebec group, 444; once more, in 1870, Hunt asserts the lower
Silurian age of the Green Mountains, 445.

In 1870, Hunt’s views undergo metamorphism, and he claims that the theories
which he had been advocating since 1863 were only his official ones, and that
his own views were quite different, 445; the rocks of the Green Mountains
begin to be called Huronian, the idea of the Devonian age of the White Moun-
tains being abandoned, and the provisional name of Terranovan introduced for
them, 446, 447 ; Dana objects to these views for various reasons, and especially
on the ground that minerals are not fossils, and that there is no reason for

x TABLE OF CONTENTS.

assuming a chronological order in minerals, 448; in replying to Dana, Hunt
asserts that he did not say that the White Mountain rocks were newer than
those of the Green Mountains, 449 ; it is shown, however, that he had said this,
450,451; a comparison of Hunt’s statements of what he said with what he
really did say, 452; Hunvr’s methods set forth, 453; DANA’s comments on
some of Hunt’s statements, 458, 454, 455. Dana remarks that Hunt’s volume
“*contains a series of misrepresentations of the views of others wholly unnecessary
and difficult to find excuse for,” 454; DaAna’s examination of the Helderberg
rocks in the Connecticut Valley, with reference to the question whether the age
of strata can be determined by means of the minerals they contain, 454, 455 ;
‘‘Jithological evidence worse than worthless,” 455.- SeLwyn’s opinion of the
revolution in Hunt’s views, 455 ; metamorphism and mineralization no test of
geological age, 455. LrsLry, in 1875, states that in Pennsylvania the Huronian
or Green Mountain system overlies the White Mountain series, both being older
than the Potsdam, 455 ; DANa’s criticism of Lesley’s statements, 456 ; LEsLry,
in 1878, withdraws this opinion, and now considers that the Green Mountains
are Palsozoic and the White Mountains Devonian, 456. Dana (1877, 1879)
gives the results of his own and Wrne’s investigations in Vermont and Western
Massachusetts, 456, 457 ; according to these, the limestones of that region are
wholly Lower Silurian, and the Taconic slates overlie them, and are of the age
of the Hudson River group, 457. Hunt, in 1878, further develops his views
in regard to the Upper and Lower Taconic series, 457, 458. Hunt, in 1879,
gives the reasons why he formerly referred the Green Mountain rocks to the
Quebec group, when he in fact regarded them as Huronian, 458 ; ‘ official
reasons ” not only prevented his dissenting from Logan’s views, but caused him
to affirm their correctness in the strongest possible manner, 458 ; further light
on Hunt's methods, 458. Various contradictory statements of C. H. Hircn-
cock in regard to Vermont geology, 460, 461 ; in 1877 he considers the Green
and the White Mountains “ nearer the Laurentian than the Huronian,” and in
1875 thinks that Emmons understood the relations of the rocks called by him
Taconic ‘‘ better than most of his contemporaries,” 460, 461 ; in 1880 he finds
that he had been in accord with Dana and Wing for years in their “disbelief in
‘Taconism,’” 460. In 1880 and 1881, Dana brings together the evidence in
regard to the geological age of the Green Mountain limestones and associated
rocks, showing beyond possibility of doubt that they are Lower Silurian,
461, 462.

NEW YORK.

Geology of the Adirondacks, 462, 463; Hat and Locan’s views in 1864, 463.
Discovery of Eozoén in Westchester County, 463. Ha. on the relations of tlie
limestones of Northern New York, 463, 464. Lrrps, in 1877, on the lithology
of the Adirondacks, 464 ; his views criticised, 464. Brirron on the geology of
Richmond County, 464; insufficiency of his data, 465.

‘NEW JERSEY.

H. D. Rocrrs’s views of the age of the gneiss and limestone of this State, 465.
Cook on the Azoic rocks, 465, 466; some suggestions in regard to points
needing further examination, 466 ; origin of the iron ores, 466.

TABLE OF CONTENTS. xi

PENNSYLVANIA.

Views of H. D. Rogers in regard to the older rocks of this State, 467, 468;
remarkable contradictions in his statements, 467, 468. Hunr employed by
Lesley ‘‘to collate all the known, supposed, and suspected facts of American
Azoic Geology,” 468; result of the same, 469. Hunt's views, in 1861 and
1871, of Pennsylvania geology, 469, 470 ; here again most remarkable contra-
dictions, 470. Hunt; in 1876, makes various statements contradictory of Les-
ley’s opinions, 471. Prive on the gneissic rocks of Lehigh County, 471; he
contradicts Hunt in reference to the age of certain iron ores, 472. C, E. Hatt
on the formations of Eastern Pennsylvania, 472. His results differ much from
those of Hunt, 473. Some remarks of LesLey in regard to the remarkable
differences between the views of Rocrers and C. E. Hau, 473; a key to the
geology found, but ‘‘it will not turn in the lock,” 474.

VIRGINIA.

FonTAIne’s views of the geology of the vicinity of Balcony Falls, 474. CAMPBELL
on the same rocks, 475 ; his peculiar views in regard to the Laurentian and
Huronian, 475 ; criticism of these views, 476.

NORTH CAROLINA.

Kerr's report of 1875, 476, 477; he assigns a large portion of the State to the
Laurentian and Huronian, 476, 477 ; BrapDLEy, in 1875, considers a large part
of these rocks as being Silurian or newer, 478 ; Kerr admits doubt in regard to
the validity of his results, 478. No satisfactory reference of any of the rocks of
this State older than the Trias, 479.

SOUTH CAROLINA.

Lreser’s work gives no clue to the age or order of succession of the older crystalline
rocks of this State, 479; Hunt, however, from Lieber’s description, considers
that he identifies the Green and White Mountain series, 479 ; Hunt’s inferences,
so far as can be made out, in contradiction with the statements of Lieber, 480.

GEORGIA.

LITTLE says that there is no Azoic in this State, 480 ; Hunt, on lithological grounds,
refers some of the rocks to the Montalban, and some to the Taconian, 480.

TEXAS.
BuUcKLEY’s reports noticed and criticised, 480, 481 ; they are of no importance, 481.

TENNESSEE. °

SAFFORD on the older rocks of this State, which he sees no reason for referring to
the Laurentian or Huronian, 481, Brapuey holds that all the metamorphic
rocks of Tennessee are of Silurian age, 481.

xil TABLE OF CONTENTS.

ARKANSAS.

Owen’s views in regard to the crystalline rocks of this State ; he holds that they are
eruptive, 482.

MISSOURI.

Nothing definite known in regard to the crystalline rocks of this State, except that
most, if not all, of them are eruptive, 482; they have been assigned to the
Huronian and Laurentian on lithological grounds solely, 482.

MICHIGAN AND WISCONSIN.

Reference to work recently published by WApsworTH in regard to the geology of
this region, 482. Age of the cupriferous rocks of Lake Superior discussed,
482-494; evidence obtained on branch of Torch River, 482-485; nature of
these rocks indicated, 483; the facts discussed, 484; conclusions reached, 485.
Irvinc, in 1873-74, on the relations of the Lake Superior rocks, 485, 486 ;
he adopts a different theory, in part, in 1879, 486 ; SwEeEr states facts in oppo-
sition to the views of Irving, 486; our explanation of the phenomena, 487.
IrvinG finds evidence in support of his views at the Dalles, 487 ; CHAMBERLIN
holds the same opinion of this locality, 488. SrLwyn, in 1882, states his views
as to the age and relations of the Lake Superior rocks, which he had previously
called Huronian, 488; these views identical with those of Fostrr and Wuit-
NEY, published in 1850, 488. Irvine replies to Selwyn, 489; WADSworTH
replies to Irving, 489. Hunr, in 1883, states that Logan, in 1863, put forth
conclusive evidence that the cupriferous rocks of Lake Superior underlaid, un-
conformably, the Potsdam sandstone, 489 ; WapswortH points out that Logan
brought no such evidence, 489. N. H. WrncuE.u agrees with Foster and
Whitney, and with Selwyn, 480. CHAMBERLIN sums up his reasons for sup-
posing the Keweenaw rocks distinct from the adjacent sandstones, 489, 490 ; the
errors in his reasoning pointed out, 490. Réswmé of the facts at the Taylor’s
Falls locality, 490 ; assumptions of the Wisconsin geologists, 490 ; what OWEN
saw there in 1850, 490, 491. Observations of Koos, in Report for 1881, 491.
N. H. Wrxcuewu thinks the sandstone at this locality more recent than the
Potsdam, 491. Errors fallen into by Irvine and CHAMBERLIN pointed out,
491. The so-called ‘‘ Keweenawan Series” owes its origin to incorrect observa-
tions, and erroneous deductions, 491, 492; N. H. WINCHELL, in 1881, gives a
summary of the opinions held regarding the copper-bearing rocks, made up from
one previously published by Wadsworth, 492. WapsworTH points out the
ignorance of the principles of geology and lithology displayed by Brooks and
Pumpelly, 492 ; they borrow largely from Foster and WHITNEY’s map without
giving any credit, 492. RomincEr on the Azoic rocks of Michigan, 492, 493 ;
his views in regard to the eruptive character of the granites, 493 ; his peculiar
theories of the eruptive rocks, 493, 494; his observations in the Menominee
region, 494. Discussion of the origin of the iron ores in a previous publication,
by Wapsworth, referred to, 494. The views maintained by FosrEr and WHIT-
NEY, and by WADsworTH, sustained by S—ELwyN, 494; these views opposed by
Dana, 494; his reasoning criticised, 494 ; NrewBErry also expresses his opinion

TABLE OF CONTENTS. xii

on the subject, 495; JutreN does the same, 495; both these writers show by
their writings that they have made no investigation of the facts, 495. SWwEEt,
in 1876, on a supposed unconformability of the Huronian and Laurentian at
Penokee Gap, 495, 496 ; Irvine on the same, 496 ; nature of such occurrences
not understood by the Wisconsin geologists, 496. Irvinc on the Huronian in
Wisconsin, 497 ; his ignorance of the necessary results of the intrusion of an
eruptive into a sedimentary one, 497; Irvine adopts some of Wadsworth’s
lithological views, but omits to state the source from which they were derived,
497, 498. HALL, in 1866, refers the gneiss and granite of Redwood River to
the Laurentian, and some quartzites in Minnesota to the Huronian, 498 ;
HAt’s views opposed by Hayprn and N. H. WincHett. The cupriferous
rocks on Lake Superior, within the limits of Minnesota, referred to the Potsdam,
in 1880, by N. H. WINCHELL, 498.

THE FORTIETH PARALLEL SURVEY.

What rocks are included in the “‘ Archean” by the Fortieth Parallel geologists, 499,
500. The Azoic or Archean rocks of the Laramie Range, 500; ZIRKEL’s
distinctive characters of eruptive and sedimentary granites, 500, 501; defect of
his methods, 501; Kine’s and A. Hacuer’s statements at variance with each
other, 501. The Medicine Bow Range referred to the Huronian by A. Hacuz,
502; no proof given that it is older than Tertiary, 502; defects of observation,
502. The Uinta Range, 503. The Wahsatch Range, gradual change of views
in regard to its age, as volume succeeded volume, 503-507. Conflicting state-
ments of ZIRKEL and Kine, 507, 508. Criticism_of Kine’s statements, and of
his manner of observing, 508; similar criticisms by GEIKIE, 509, 510. Sum-
ming up of the results of the Fortieth Parallel Survey, and indication of their
value, 510, 511.

HAYDEN'S SURVEY.

The rocks of the Chugwater, in 1868, called Laurentian, but no reasons given for this,
511, 512 ; HaypeEn, in 1869, states his theoretic views in regard to igneous and
metamorphic rocks, 512. HAypeEN calls the rocks on the north side of the Uinta
Range Silurian and Huronian, 512; the Fortieth Parallel Survey calls them
Carboniferous, Powell Devonian, Emmons Cambrian, and Marsh Silurian,
512, 513. ENp.icu, in 1874, calls all the crystalline rocks in the region studied
by him, at the head of the Rio Grande and Rio Animas, Metamorphic Paleozoic,
513. Statement of PEALE in regard to crystalline rocks, 513. ENpiicH divides
the Azoic rocks into three systems, 513, 514; he admits the insufficiency of his
observations, 514. Remarks by St. JoHN and Prag, 514. Summing up of the
condition of things in the Rocky Mountains, 514, 515.

WHEELER’S SURVEY.

No evidence offered in regard to the Azoic, 515. STEVENSON in regard to age of rocks
called Archean, in parts of New Mexico and Colorado, 515.

Xiv TABLE OF CONTENTS.

JONES’S SURVEY.

Comstock on the Azoic rocks of Northwestern Wyoming, 515. No reasons other
than lithological for calling these rocks Laurentian, 515, 516.

POWELL’S SURVEY.

Report by Nrwton and JENNEY on the Black Hills, 516; the Azoic rocks divided
into Laurentian and Huronian, but on very slight evidence, 516.

CALIFORNIA.

Results of the California Survey, 516, 517. Hunt's views in 1866, and in 1868,
before visiting the region, 517. He spends several days there, and discovers
that rocks of the Sierra Nevada which contain Jurassic fossils are of Huronian
age, 517, 518. Huwnv’s views of Californian geology shown to be fundamentally
wrong, 518.

"RAR Ly je

RisuUME, AND GENERAL Discussion.

Introductory remarks, 519. The geology of Canada and New England in an almost
hopeless state of confusion, 519, 520. How this condition of things has been
brought about, 520. The establishment of the Silurian System by Murcuison,
in 1845, opens the way to the discussion of the question whether the lowest limit
of life had been reached, 520. First use of the term Azoic by Murcuison, 520,
521; his definition of that term, 521; his hesitating and contradictory statements
in regard to it, 521; his gradual withdrawal of it in the successive editions of
Siluria, 521, 522. BArranpr’s grouping, in 1846, of the Protozoic and Azoic
rocks, 522; confusion caused by the use of the term Cambrian already begun, 522.
Fosrrer and WHITNEY, in 1851, describe certain rocks on the south shore of Lake
Superior, under the designation of the Azoic System, 522. Similar rocks, in
Canada, called by LoGaN the Metamorphic Series, but without fully ascertaining
their geological position, 523. LoGan, in 1854, applies the name Laurentian to
these rocks, 523; confusion introduced by his inability to distinguish between
the Azoic and the Paleozoic, 523. The term Azoic for some time in current use
in this country, 523, 524; Dana’s use and definition of it in 1862 and 1871, 524;
his views in regard to the existence of life during an ‘‘azoic”” period, 524; the
position assumed by him in 1874, and the introduction of the term Archean,
with a definition of it, 524. Confusion of views in regard to the older crystal-
line rocks, 525. Some general remarks introductory to the consideration of the
subject, 525 ; great interest attaching to the question whether life exists in other
worlds than our own, 525 ; importance of fixing the epoch when life began here,

TABLE OF CONTENTS. XV

525. What is meant by the term Azoic, and what rocks maybe included under
that designation, 526, 527. How Fosrrr and Wuirney used the term Azoic,
527. The condition of things in regard to the propriety of the use of that term,
527. Injustice done by Locan in his introduction of the name Laurentian,
527,528. Discussion of the question whether the term Archean ought to replace
that of Azoic, 528. Examination of the Eozoén question, 528-538; first announce-
ment of its existence by LoGAN, in 1858, 528 ; Dawson, in 1864, announces
that it belongs to the Rhizopods, and that its discovery will be “ one of the bright-
est gems in the scientific crown of the Geological Survey of Canada,” 529; further
investigation of the Eozoén by CARPENTER, and its recognition by him as a
Foraminifer, 529; his authority insures its general recognition as the earliest
known representative of life, 529; opposition, however, begins to manifest itself,
529; gradual accumulation of an eozodnal literature, but general acceptance of
the Eozoén Canadense, 530; difficulty in the way of proving that it was not
organic, 530; how Moésrvus overcame this difficulty, 530, 531; his results,
and the characterization of them by Zirrer and F. RoEMrEr, 531; Lerpy’s views,
531; our own investigations into the character of the ‘‘ Eozodnal limestones ” of
Eastern Massachusetts, 532-534. Prevalent tendency among paleontologists, at
the present time, to find traces of organic life in all kinds of rocks, such as
granite, lava, and even in slag — this accounted for, 534. Some evidence in re-
gard to the ability of CARPENTER and Dawson to distinguish minerals from
fossils, 534-537. Extraordinary discoveries of Orro Haun, and their bearing
on the Eozoén question, 537, 538. Question discussed whether the existence of
limestone and graphite is a proof of the presence of life at the time of their forma-
tion, 538-544. Biscuor’s views in regard to the existence of carbon during the
primeval epoch, 538 ; his evidence controverted, 538-543; graphite in cast-iron,
538; in the crystalline rocks, 539; not formed as coal has been, 540; plumbago
not always graphite, 540; the artificial production of graphite, and of the dia-
mond, 540; graphite formed in the Le Blanc process, 541; BiscHor’s ideas in
regard to the mode of occurrence of the diamond shown to be incorrect, 541,
542; how it does occur, in connection with gold, 542; in South Africa, in vol-
canic rocks, 542, 543; some facts in regard to the peculiar circumstances under
which the diamond must have been formed, 543. Examination of the current
idea that the presence of carbonate of lime is proof of the existence of life at the
- time this was formed, 543, 544. Similar inquiry in regard to iron, 544; in
regard to sulphur, 544, 545; phosphoric acid, 545. No encouragement given,
by the investigations of the past half-century, to the idea that below the
Primordial or Potsdam zone there is another series of fossiliferous rocks, 545.
The wish father to the thought, 545, 546; LYELL “‘revels with delight”
(fide Murchison) at the discovery of the Eozoén, 545. Difficulty in which evo-
lutionists are placed by its adoption, 546; F. Rormer’s statement of the case
recommended for consideration, 546. Remarkable result of paleontological
investigations — one and the same fauna over the whole globe during the Pri-
mordial epoch, 546. Inferences with regard to the azoic character of the Azoic
series, 546. Inquiry into Dana’s use of his term Archean, 547-550; he includes
under that designation rocks of different ages, both fossiliferous and non-
fossiliferous, 547 ; the importance of recognizing in our nomenclature the epoch
of the first introduction of life upon the globe, 547. Dana believes that a part

.

Xvi TABLE OF CONYENTS.

of the Archean rocks are fossiliferous, and states what the life of that epoch
must have probably been, 548 ; his ‘‘ abundance of life,” however, only a theo-
retical abundance, 548. All eruptive and crystalline rocks, except the meta-
morphic Paleozoic and post-Palozoic, according to Dana, ‘‘ Archean,” 548,
549; unphilosophical character of this idea, 549, 550.

Inquiry into the propriety of the division of the Azoic (Archzan) into two or more
groups, 550-560 ; according to Dana’s views, this absolutely necessary, 550.
The attempts of the Canada Survey to do this on the evidence of fossils, 551, 552;
the Aspidella and Arenicolites, 551, 552. Geological time kept by the order of
succession of life, and not by means of minerals, 552 ; the Canada Survey, and
the results of its attempts to follow the latter method, 552.

How such methods came to be in vogue, 552. By what principles the Canadian
Survey was governed, 553. LoGaN the author of them, 553 ; with what train-
ing he began it, 553, 554; his age at the time he published his first scientific
paper, 554; the influences under which he worked, 554; he follows LYELL
implicitly, 555; he begins the work with certain theoretical assumptions, the
truth of which he never investigates, 555 ; how his erroneous interpretation of
the geology of Lake Huron and Lake Superior led him to false conclusions, 556.
The Report of 1863 assumed certain things as having been proved which had
not been, 556. Hvnt’s statements about his own or other people’s work not to
be accepted as authority until his quotations have been compared with the
original authorities, 556. The question of the nonconformity of the Laurentian
and Huronian looked into, 556; what owght to be seen if the two are uncon-
formable, and what 7s seen, 556, 557 ; SrLwyn’s statements on this point, 557.
What takes place when eruptive rocks begin to be acted on by erosive agencies,
557. What basis of fact underlies the division of the Azoic rocks into two
series, 558, 559. Locan takes the ground that lithological characters are suffi-
cient for the arrangement of rocks in chronological order, 559 ; in accordance
with this view, the rocks previously called Huronian still farther differentiated,
560; the gabbros thus separated, 560; the Hastings series, demonstrated by
VeENNoR to be continuous with the Laurentian, made into the Montalban and
Taconian, 560; the Arvonian, 560. Tabular arrangement of the rocks as at
present adopted by the Canada Survey, 561; some improvements, and a carrying
farther forward of the same idea, suggested In another table, 562 ; comments
on this mode of work, 562. Importance to American geologists of having the
work of the Canada Survey done according to better methods, 562.

APPENDIX: Examination of some of Invine’s statements, made in the Third Annual
Xeport of the United States Geological Survey, 563-565.

OS
wh)
—

CANADA,

PART .:

Synopsis of the Evidence on which the Rocks of the Azoic System
have been variously grouped into Distinct Divisions by American
Geologists.

In the following discussion the various regions where rocks of the
Azoie System occur will be taken up and examined in a geographical
order, beginning with that part of the North American continent where
these rocks have their greatest development, and where, in course of
a geological survey carried on continuously for more than forty years, a
large portion of the material has been published which will here come
under review. In order to prevent misunderstandings, and as an im-
portant assistance to those who may hereafter wish to make an inde-
pendent examination of the questions here discussed, the exact language
of the author quoted will be given in as much fulness as seems desirable,
although this course must necessarily considerably increase the length
of this paper.

CANADA.

Sir Wm. Logan, in the Report of Progress of the Canada Geological
Survey for 1845-46 (pp. 40-51), described a series of rocks which he,
following Lyell, called the “‘ Metamorphic Series.” This he divides into
two divisions, one composed in general of ‘“syenitic gneiss,” the other of
the same rock with intercalated bands of crystalline limestone. The
relations of these to each other can be best expressed in Logan’s own
words : —

“To the south of the Mattawa and of the Ottawa in its continuation after
the junction of the two streams, important beds of crystalline limestone become
interstratified with the syenitic gneiss, and their presence constitutes so marked
a character that it appears to me expedient to consider the mass to which they
belong as a separate group of metamorphic strata, supposed from their geo-
graphical position and general attitude to overlie the previous rocks conform-
ably. The limestone beds appear to be fewer at the bottom than at the top

BULL. MUS. COMP. ZOOL. VOL. VII. —No. 11,

332 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

of the group, but whether few or many, they are always separated by beds
of gneiss which in no way differs either in constituent quality or diversity of
arrangement from the gneiss lower down, except in regard to the presence of
accidental minerals, the most common of which are garnets.” (l.c., pp. 41, 42.)

It is thus seen that his divisions are arbitrary and theoretical, both
being, according to his statement, conformable and interlaminated with
one another. As regards the origin of the “syenitic gneiss,” or lower
formations, he writes that they possess “an aspect inducing a theoreti-
cal belief that they may be ancient sedimentary formations in an altered
condition.” (/. ¢., p. 40.) The lamination planes of the gneiss (?) ap-
pear to be taken without hesitation as planes of sedimentation. As
before, theoretic belief, and not evidence, was the basis on which all
was decided, and Logan never went beyond this.

Without adopting any theory of the origin of the rocks in question,
it is sufficient simply to point out that, accepting Logan’s own state-
ments as true, the rocks might, so far as the published evidence goes,
have originated in any way not a priort impossible. His evidence is
valueless excepting so far as credit may be given to the skill he may at
that time have possessed in distinguishing metamorphic sedimentary
from metamorphic eruptive rocks.

Later he stated : —

“ The succession of rocks in ascending order, . . . . after crossing sixty-three
miles, . . . . occupied by the unbroken uniformity of the lower metamorphic,
or syenitic gneiss, formation, is as follows :—

“1, Chloritic slates and conglomerates.
“9. Greenish sandstones.
“3. Fossiliferous limestones.” (1. ¢., p. 67.)

The chloritic slates and conglomerates were said to hold pebbles and
boulders of the subjacent gneiss. The limestones were regarded from
their fossils as being of the age of the Niagara. Mr. Logan says :—

“The facts that have as yet come within my observation in respect to these
formations have not been sufficient to enable me to determine to my own satis-
faction what their relations are in respect to conformability. That the lime-
stones are unconformable with the slates appears almost certain, but it is not
in my power to state with which the intermediate sandstones are conformable,
if they are so with either, or whether they are unconformable with both ; nor
can I assert whether the slates are conformable with the gneiss.” (J. c., p- 69.)

We thus see that the chloritic slates and conglomerates, which later
on lithological evidence were referred to the Huronian, were only shown
to be older than the Niagara, their true age being unknown. ©

CANADA, a30

Logan in the Report of Progress for 1846-47 described the series on
the north shore of Lake Superior in ascending order, as follows (/. ¢.,
pp. 8-17) :—

“1. Granite and syenite.

“9. Gneiss.

“3. Chloritic and partially talcose and conglomerate slates.

“4, Bluish slates or shales, interstratified with trap.

“5. Sandstones, limestones, indurated marls, and conglomerates, interstrati-
fied with trap.

“ The rock at the base of the series is a granite, frequently passing into a
syenite by the addition of hornblende, but the hornblende does not appear to
be often present wholly without the mica... . . The granite appears to pass
gradually into a gneiss, which seems to participate as often of a syenitic as a
granitic quality... . . The gneiss is succeeded by slates of a general exterior
dark green colour, often dark-gray in fresh fractures, which at the base appear
occasionally to be interstratified with beds of a feldspathic quality, of the red-
dish color belonging to the subjacent granite and gneiss. ... . Some of the
beds have the quality of a greenstone, others that of a mica slate, and a few
present the character of quartz rock. Rising in the series, these become inter-
stratified with beds of a slaty character, holding a sufficient number of pebbles
of various kinds to constitute conglomerates. The pebbles seem to be of
various qualities, but apparently all derived from hypogene rocks. . . . . The
formations which succeed, rest unconformably upon those already mentioned.
The base of the lower one [No. 4], where seen in Thunder Bay in contact with
the subjacent green slates, presents conglomerate beds probably of no great
thickness, composed of quartz pebbles chiefly, with a few of red jasper, and
some of slate in a green arenaceous matrix, consisting of the same materials in
a finer condition.”

Reposing on the bluish slates (No. 4) are ‘sandstones, limestones,
indurated marls and conglomerates interstratified with trap,” and
crowned by an enormous amount of volcanic overflow. No evidence
is adduced to show that these two “volcanic formations” are uncon-
formable with each other, but sufficient proof is cited to show that they
are unconformable with the granite, gneiss, and chlorite slate. The
volcanic formations are, however, regarded as being older than the
Potsdam sandstone. (J. ¢., p. 34.)

Logan further remarks :—

“The chloritic slates at the summit of the older rocks on which the volcanic
formations rest unconformably, bear a strong resemblance to those met with in
the upper part of Lake Temiscamang on the Ottawa, and it appears probable
they will be found identical.” (J. c., p. 34.)

334 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Logan evidently held that the greenish slates (No. 3) were conform-
able to and continuous with the underlying gneiss, one rock passing
into the other ; while the conglomerates observed were not at the base
of the slates, but quite high in the series. (Geol. of Canada, 1863,
pp. 52-55, 64.) Dr. Hunt’s language in his “ Azoic Rocks” (p. 68)
implies that Logan found a different relation between the gneiss and
slate, — namely, unconformability with the conglomerate at the base.

Mr. Alexander Murray in the same report (1846-47) states that the
rocks in the basin of the Kamanistiquia River are granite, syenite,
gneiss, micaceous and chloritic schist, overlain by blackish argillaceous
slates with associated trap.

Of the first series he says : —

“Where they make their appearance at the lower end of the portage, the
character of the rock is a red or in some instances a whitish massive syenite,
which passes gradually inte a gray gneissoid syenite, dipping at a high angle
N.N. W. Resting conformably on the gneiss, there occurs a series of dark
greenish blue or greenish black altered slates, the one rock passing almost im-
perceptibly into the other. .... Towards the bottom near the junction with
the syenitic portion, the slates are of a dark bluish and occasionally of a brown-
ish color, They appear to be highly altered.”

Of the black argillaceous slates Mr. Murray says : —

“The base of this formation . . . . was observed on the Kamanitiquia near
the Grand Falls. Its immediate junction with the rock on which it reposes
was concealed from view, but appears to be indicated by the position of a small
lake or pond, occurring just below the second portage, and the marshy ravines
which run from it in the direction of the strike on each side. The slates vis-
ibly reach to within a short distance of the pond, probably brought into place
against the syenite by a dislocation.” (J. c., pp. 51-53.)

The syenite and gneiss afterwards were assigned to the Laurentian,
and the greenish blue or greenish black slates to the Huronian. Hence
we see that at the only contact known for many years of the Laurentian
and Huronian both series were conformable, passing almost imperceptibly
into one another. Also, that near the junction the slates were highly
altered. (Geol. of Canada, 1863, p. 64.) These facts are not men-
tioned by Dr. Hunt in his account of this report. (Azoic Rocks, pp.
68, 69.) It is, however, to be kept in mind, that at this time, as also
when the Huronian was named and for some years later, Nos. 4 and 5,
or the black slates, sandstones, traps, conglomerates, etc., constituting
the copper-bearing series (Keweenawan, but really Potsdam) were held
to be the exact equivalents of the schists and slates (Huronian) north of

CANADA. 335

Lake Superior, while the above greenish slates (No. 3) were not sepa-
rated from the preceding rocks (Nos. 1 and 2) until many years later.
(See Am. Jour. Sci., 1852, (2) XIV. 224-229 ; 1857, XXIII. 305-314 ;
Azoic Rocks, pp. 71, 72, 80.)

In the Report of Progress for 1847-48, Mr. Murray gives some ac-
count of the sequence of the rocks on the islands and northern shore of

Lake Huron.

“The older groups observed consist, firstly, of a metamorphic series, com-
posed of granitic and syenitic rocks, in the forms of gneiss, mica slate, and
hornblende slate ; and, secondly, of a stratified series composed of quartz rock
or sandstones, conglomerates, shales and limestones, with interposed beds of

greenstone ;”

succeeded by fossiliferous formations, i. e. Potsdam sandstone, ete.
Certain of the conglomerates of the second series are said to contain
pebbles and boulders of syenite, but beyond this nothing is advanced to
show the relations of this to the granitic and syenitic rocks, the two
series not being seen in contact. The relation of the fossiliferous forma-
tions to the preceding series was shown clearly enough, the separation
being a marked one. (J. ¢., pp. 107-113.)

Mr. Murray further says :—

“On a cluster of small islands . ... Granite, [lithologically like the
Laurentian,] was found breaking through the quartz-rock. ... . The colour
‘of the rock was red. On one of the islands, quartz-rock beds on opposite
sides of the granite were observed to dip in opposite directions, north on the
north side and south on the south side, at an angle of 70° or 80° ; and in an-
other of the islands the quartz-rock and granite were seen in juxtaposition, the
former reclining on the latter. In this case the quartz rock was traversed by
several trap dykes running slightly oblique to the strike, while granitic veins
ran transversely through the whole, and were continued through a main body
or nucleus of granite, the one granite being distinguishable from the other,
notwithstanding the red color of both, by the finer texture of the veins.” (J. c.,
pp. 112, 113.)

In a “Report on the North Shore of Lake Huron,” under date of
December 29, 1848, Mr. Logan gives some account of the second series
described by Mr. Murray, and states : —

“The series of rocks occupying this country from the connecting link be-
tween Lakes Huron and Superior to the vicinity of Shebawenahning, a distance
of 120 miles, with a breadth in some places of ten, and in others exceeding
_ twenty miles, it appears to me, must be taken as belonging to one forma-

336 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

tion ; on the west it seems to repose on the granite, which was represented in
my report on Lake Superior as running to the east of Gros Cap, north of Sault
Ste. Marie; on the east the same supporting granite was observed by Mr.
Murray north of La Cloche, between three and four miles in a straight line up
the Riviere au Sable, . . . . and again, about an equal distance up another
and parallel tributary, . . . . in both cases about ten miles from the coast.
. ... In respect to the geological age of the formation, the evidence afforded
by the facts collected last year by Mr. Murray ... . is clear, satisfactory,
and indisputably conclusive, . . . . successive formations of the lowest fossil-
iferous group of North America, were each in one place or the other found, in
exposures divested of all vegetation, resting in unconformable repose, in a
nearly horizontal position, upon the tilted beds, and undulating surface of the
quartz rock, and its accompanying strata, filling up valleys, overtopping moun-
tains, and concealing every vestige of dykes and copper veins. .... The
chief difference in the copper-bearing rocks of Lakes Huron and Superior,
seem to lie in the great amount of amygdaloidal trap present among the lat-
ter, and of white quartz rock or sandstone among the former. But on the
Canadian side of Lake Superior there are some considerable areas, in which
important masses of interstratified greenstone exist without amygdaloid, while
white sandstones are present in others, as on the south side of Thunder Bay,
though not in the same state of vitrification as those of Huron. But notwith-
standing these differences, there are such strong points of resemblance in the
interstratification of igneous rocks, and the general mineralized condition of
the whole, as to render their positive or proximate equivalence highly probable,
if not almost certain ; and the conclusive evidence given of the age of the
Huron, would thus appear to settle that of the Lake Superior rocks, in the
position given to them by Dr. Houghton, the late State Geologist of Michigan,
as beneath the lowest known fossiliferous deposits, a position which, as will be
seen by a reference to the Report of Progress I had the honor to submit to
your Excellency in 1846, appeared to me to derive some support from evidences
on the Canadian side of Lake Superior itself.” (J. c., pp. 8, 9, 19, 20.)

In this is to be seen one of the attempts to decide geological age by
lithological evidence, applied to rocks at great distances from one an-
other, — a failure, in this case at least, as will be seen farther on. One of
the writers has pointed out elsewhere that the statements in this report
and in that for 1846-47 (p. 34) regarding Dr. Houghton’s views are
erroneous. (Bull. Mus. Comp. Zéol. 1880, VII. (Geol. Series I.) 83.)
The views which Logan held regarding the age of the copper-bearing
rocks of Lake Superior at the time of the publication of the report from
which quotations have just been made, were published later in several
papers. (Bull. Soc. Geol. France, 1849-50, (2) VII. 207-209. Report
Brit. Assoc. Adv. Sci., 1851, Trans. Sec., pp. 59-62. Am, Jour. Sci.,
1852, (2) XIV. 224-229.) In these publications the copper-bearing

CANADA. 337

rocks of Lake Huron, and therefore those of Lake Superior, were re-
garded as being of Cambrian age.

In the Report of Progress for 1848-49, Mr. Murray again reported
on the region north of Lake Huron. He arranges the rocks along the
Spanish River into two series: the granitic or metamorphic group, and
the quartz rock group. The first group “appeared to rise from beneath
the rocks of the second group in two different localities,” but no evidence
seems to have been found to show the relations of the two supposed
formations except the finding of pebbles of granite or syenite in some of
the conglomerates of the second group. ‘The rocks of the first group
were said to be granite or syenite, except the following : —

“ A gneissoid structure was observed on one or two occasions, but it was for
the most part obscure and ill-defined, being perceptible rather in a longitudinal
arrangement of the constituent minerals, than in conspicuous beds of different
quality.” (J. ¢., pp. 36-42.)

In the Report of Progress for 1849-50, a tract of country on the St.
Lawrence River, between Bay St. Paul and Murray Bay, was described.
Here the metamorphic group, consisting of gneiss, was overlain by
white quartz rock (Potsdam sandstone). (/. c., pp. 8-10.) In the Re-
port for 1851-52, the metamorphic or gneissoid group is likewise said
to be overlain by Potsdam sandstone in the country between Beauhar-
nois and the Riviere du Nord. (/. ¢., p. 6.)

In the Quarterly Journal of the Geological Society (Vol. VIIL, 1852,
p- 210), Mr. Logan states regarding the rocks north of Lake Huron :—

“On Lake Huron the Lower Silurian group rests unconformably upon a
siliceous series with only one known band of limestone, of about 150 feet
thick, with leaves of chert in abundance, but as yet without discovered
_ fossils. This series is supposed to be of the Cambrian epoch. It compre-
hends the copper-bearing rocks of that district, and with its igneous inter-
stratified masses has a thickness of at least 10,000 feet. The gneissoid group,
of which mention is made, is probably still older than this. Its conditions
appear to me to make it reasonable to suppose that it consists of aqueous de-
posits in an altered state.”

In the Report for 1852-53, but published in 1854, Mr. Logan
writes :—

“The name which has been given in previous Reports to the rocks underly-
ing the fossiliferous formations in this part of Canada is the Metamorphic
series, but inasmuch as this is applicable to any series of rocks in an altered
condition, and might occasion confusion, it has been considered expedient to
apply to them for the future, the more distinctive appellation of the Laurentian

VOL. VII.—No. 11. 22

338 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

series, a name founded on that given by Mr. Garneau to the chain of hills
which they compose. The geological formations which underlie the district in
ascending order would thus be as follows ; —

“1. Laurentian series.

“2. Potsdam sandstone,” etc. (J. ¢., p. 8.)

It will thus be seen that when the name Laurentian was thus pro-
posed, it was the exact equivalent of the Azoic of Foster and Whitney
proposed four years before.

In “A Sketch of the Geology of Canada,” by Dr. Hunt, occurs the
first mention of the Huronian system as such.

“The shores of Lakes Huron and Superior offer a series of schists, sand-
stones, limestones and conglomerates interstratified with heavy beds of green-
stone, and resting unconformably upon the Laurentian formation. As these
rocks underlie those of the silurian system, and have not as yet afforded any
fossils, they may probably be referred to the Cambrian system (lower Cam-
brian of Sedewick.)..... This Huronian formation is known for a distance of
about 150 leagues upon Lakes Huron and Superior, and everywhere offers
metalliferous veins, which have as yet been very little explored.” (Canada at
the Universal Exhibition of 1855, pp. 427, 428.)

In the same paper Dr. Hunt says of the Laurentian system : —

“The rocks of this system are, almost without exception, ancient sedimentary
strata, which have become highly crystalline.” (p. 421.)

So far as we are able to find in the Reports of the Canada Geological
Survey no evidence was advanced to prove this position ; it was a purely
theoretic assumption, as Logan states (ante, pp. 331, 332). Dr. Hunt
also declares that the Huronian on the shores of Lakes Huron and Su-
perior rests unconformably upon the Laurentian formation. This too
was a theoretical belief instead of an observed fact, so far as the Reports
bore evidence (p. 427), except in the case of the Lake Superior copper-
bearing rocks (Keweenawan, Potsdam), at that time regarded as being
the equivalent of the schists (Huronian) north of Lake Huron. (See
Azoic Rocks, pp. 71, 72 ; also ante, pp. 334, 335.)

Of the chlorite schists in the valley of Lake Temiscaming it is writ-
ten :—

“The chloritic schists probably correspond to the Huronian rocks, but it is
difficult to fix the age of the sandstones which are destitute of fossils.” (J. ¢.,
p- 447.)

The first mention of the Huronian formation by name, found in the
Reports of Progress of the Canada Geological Survey, is in Mr. Murray’s
Report for 1854, under date of June 11, 1855, (p. 125,) as follows : —

CANADA. 339

“ Among the boulders on Lake Nipissing, many were observed to be of a
slate conglomerate, and they were frequently of very great size ; in their as-
pect and general character these have a very strong resemblance to the slate
conglomerate of the Huronian series, from which in all probability, they are
derived.”

The next mention is in the Report for 1855, dated March 1, 1856,
p. 134 :—

“The pebbles and boulders of metamorphic rocks which abound in the
gravel and clay deposits, and are numerously scattered over the surface, are
clearly derived from the Laurentian and Huronian formations on the north
shore of Lake Huron.”

In the Report for 1856 (March 1, 1857, pp. 168, 172) it is stated : —

“ The rocks of the region explored during the season, embrace two of the
oldest recognized geological formatios, the Laurentian and Huronian.... .
The difference in lithological character between the two formations was always
sufficiently apparent, but though both were frequently found at short distances
apart, the immediate point of contact was always obscure ; and a mass of green-
stone of rather coarse grain was usually the first intimation of the proximity
of the higher rocks. . . . . Whether this greenstone is the result of an over-
flow contemporaneous with the upper formation, or an eruptive mass intruded
at a later period, has not yet been ascertained.”

Regarding the hypersthene rock which has since been set apart as the
Upper Laurentian or Norian Series, Dr. Hunt in his Report for 1854
(April 1, 1855, p. 374) states : —

“The rocks about to be described belong to the crystalline strata of the
Laurentide mountains, and occur, as far as yet observed, in close association

with the crystalline limestones, which alternate with the gneissoid and quart-
zose rocks of the formation.” :

In Dr. Hunt’s Report for 1856 (April 1, 1857, p. 451, see also Philo-
sophical Magazine, 1855, (4) IX. 354, 355), it is written concerning
the same rocks : —

,

“In the Report for 1854 I have described at some length a class of stratified
felspathic rocks, which form an important part of the Laurentian series, and
are associated with the calcareous and magnesian deposits of that ancient
formation.”

The Reports here referred to from 1853 to 1856 were not published
until 1857.

The division of the Azoic rocks into Laurentian and Huronian, and
Logan’s view that the copper-bearing rocks of Lake Superior were of

340 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

the same age as the Huronian rocks of Lake Huron, were opposed the
same year by one of the present writers in the May number of the
American Journal of Science (1857, (2) XXIII. 305-314). He also
pointed out Logan’s violation of the law of priority in appropriating the
term Laurentian from Desor.* It was there shown that the reason Logan
had for separating the Huronian from the other Azoic rocks was his
(Logan’s) belief that the copper-bearing rocks (Potsdam) of Lake Supe-
rior were the same as the Azoic schists north of Lake Huron : hence, as
the copper-bearing rocks of Lake Superior rested unconformably on
Azoic granites, etc., therefore the Lake Huron rocks must. Later, Logan
abandoned his premises, but did not, however, give up his conclusion.
(See Hunt, Azoic Rocks, p. 80.)

In the Proceedings of the American Association for the Advancement
of Science (August, 1857, pp. 44-47), Mr. Logan made some statements
regarding “the division of the Azoic Rocks of Canada into Huronian
and Laurentian,” the chief of which we reproduce here : —

“The sub-Silurian Azoic rocks of Canada occupy an area of nearly a quarter
of a million of square miles. Independent of their stratification, the parallel-
ism that can be shown to exist, between their lithological character and that of
metamorphic rocks of a later age, leaves no doubt on my mind that they are a
series of ancient sedimentary deposits, in an altered condition. . ... So
early as the year 1845, as will be found by reference to my report on the
Ottawa district (presented to the Canadian government the subsequent year),
a division was drawn between that portion which consists of gneiss and its
subordinate masses, and that portion consisting of gneiss interstratified with
important bands of crystalline limestone. I was then disposed to place the
lime-bearing series above the uncalcareous, and although no. reason has since
been found to contradict this arrangement, nothing has been discovered espe-
cially to confirm it... < . In the same report is mentioned, among the Azoic
rocks, a formation occurring on Lake Temiscaming, and consisting of silicious
slates and slate conglomerates, overlaid by pale sea-green or slightly greenish-
white sandstone, with quartzose conglomerates. The slate conglomerates are
described as holding pebbles and boulders (sometimes a foot in diameter) de-
rived from the subjacent gneiss, the boulders displaying red feldspar, translu-
cent quartz, green hornblende, and black mica, arranged in parallel layers,
which present directions according with the attitude in which the boulders
were accidentally inclosed. From this it is evident that the slate conglomer-
ate was not deposited until the subjacent formation had been converted into

* This paper of Prof. Whitney’s, in common with some others, was accidentally
omitted in Mr. Wadsworth’s ‘‘ List of Papers” appended to the ‘‘ Notes on the
Geology of the Iron and Copper Districts of Lake Superior,” although reference was
made to it in the text. (See also Canadian Journal, 1857, (2 ) II. 302.)

CANADA. 341

gneiss, and very probably greatly disturbed ; for while the dip of the gneiss,
up to the immediate vicinity of the slate conglomerate, was usually at high
angles, that of the latter did not exceed nine degrees, and the sandstone above
it was nearly horizontal. In the Report transmitted to the Canadian govern-
ment in 1848, on the north shore of Lake Huron, similar rocks are described as
constituting the group which is rendered of such economic importance, from
its association with copper lodes. This group consists of the same silicious
slates and slate conglomerates, holding pebbles of syenite instead of gneiss,
similar sandstones, sometimes showing ripple marks, some of the sandstones
- pale-red green, and similar quartzose conglomerates, in which blood-red jasper
pebbles become largely mingled with those of white quartz, and in great moun-
tain masses predominate over them. But the series is here much intersected
and interstratified with greenstone trap, which was not observed on Lake
Temiscaming. .... The group on Lake Huron we have computed to be
about 10,000 feet thick, and from its volume, its distinct lithological charac-
ter, its clearly marked date posterior to the gneiss, and its economic impor-
tance as a copper-bearing formation, it appears to me to require a distinct
appellation, and a separate color on the map. Indeed, the investigation of
Canadian geology could not be conveniently carried on without it. We have,
in consequence, given to the series the title of Huronian. A distinctive name
being given to this portion of the Azoic rock, renders it necessary to apply one
to the remaining portion. The only local one that would be appropriate in
Canada is that derived from the Laurentide range of mountains, which are
composed of it from Lake Huron to Labrador. We have, therefore, designated
it as the Laurentian series.” (See also Canadian Journal, 1857, (2 ) I. 489-
442 ; Canadian Nat. and Geol., 1857, II. 255-258.)

The logic of the last few sentences will appear to be of a somewhat
peculiar character, when it is remembered that the name “ Laurentian”
had been adopted some two years before the name ‘ Huronian” was
used, and some four years before Mr. Logan’s paper was read.

As we have pointed out before, the age of the Lake Temiscaming
slates was unknown.

In the same Proceedings Mr. Logan published a paper “ On the Prob-
able Subdivision of the Laurentian Series of Rocks of Canada.” Some
limestone and associated labradorite rocks he would set apart, but does
not propose any name for them. This division seems to be a local one
based on lithological characters, as no evidence was advanced to show
that this formation was not conformable with the remainder of the
Laurentian, as it had been stated to be before. (Proc. Am. Assoc. Adv.
Sci., 1857, XI. 47-51; Canadian Journal, 1858, (2 ) III. 1-5 ; Cana-
dian Nat., 1857, II. 270-274.)

Dr. J. J. Bigsby, in 1862, regarded the Huronian as distinct from the

342 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Cambrian, and intimately related to the Laurentian, giving among his
reasons its marked similarity, lithologically, to the Laurentian, and the
conformity of the Laurentian and Huronian ; and stating that in the
only place north of Lake Superior where the two systems have been
seen in contact, they were found conformable. (Quart. Jour. Geol. Soc.,
1863, XIX. 36-52.)

Two other localities spoken of by Dr. Bigsby were hypothetical, not
actual observed contacts, as he supposed. (See Report on the North
Shore of Lake Huron, 1849, pp. 8, 9; Report of Progress, 1848-49,
p. 36.)

In the Report on the Geology of Canada, 1863, the so-called gneisses
of the Laurentian series are assumed to be stratified, and although the
acknowledgment is made that the supposed beds “ when thick, which
they usually are, might on first inspection be mistaken for intrusive
igneous instead of altered sedimentary masses.” That they are really
sedimentary is supposed to be shown by the minerals being obscurely
arranged in parallel lines “ conformable with the more distinctly banded
portion of the strata.” (. ¢., p. 23. See also p. 587.)

In fact Mr. Logan states: “‘ The rocks which compose the Laurentian
mountains were shown by the Geological Survey, in 1846, to consist of
a series of metamorphic sedimentary strata, underlying the fossiliferous
rocks of the Province.” We have pointed out that nothing of the kind
was shown by the Survey; but that there was only an announcement
of “a theoretic belief that they may be ancient sedimentary formations
in an altered condition.” (Geol. Survey of Canada, 1845-46, p. 40,
1863, p. 22; Azoic Rocks, p. 66 ; ante, p. 332.)

Mr. Logan further states, that it is difficult north of Lake Huron to
distinguish the Laurentian gneiss from an intrusive granite. (Geol. of
Canada, 1863, p. 61.)

Regarding the relation of the Huronian to the Laurentian nothing
that can be called evidence is advanced, except in one place; but, as
usual, some general assertions are made. The following extract will
give an idea of what was actually known of the relations of the two
formations, with the exception to be mentioned later.

“Tn that part of the country on the north shore of Lake Huron which lies
between Mississagui and St. Mary Rivers, where the Huronian series has been
more completely examined than elsewhere, the immediate contact of the gneiss
with the overlying rocks has not been observed. On the coast line between
the Mississagui and Thessalon Rivers, a distance of about twenty-five miles,
the gneiss extends from within about four miles of the former to within about

9

CANADA. 343

the same distance from the latter ; but itis very much disturbed by intrusive
granite and greenstone, and, although there are great exposures of rock, it is
very difficult to make out how the stratified portions are related to one an-
other. The gneiss extends to the vicinity of a small stream about a mile and
a half above Les Grandes Sables, and what is supposed to be the lowest Hu-
ronian mass of that part occurs about half a mile above the stream. It consists
of a grey quartzite which abuts against one mass of gneiss and runs under an-
other, and appears to be much broken by and entangled among the intrusive
rock ; but judging from a transverse measure in one part, its thickness would
not be far from 500 feet.” (J. c., p. 55.)

It would seem that here the Huronian was found abutting against
and underlying the Laurentian gneiss (granite). In none of the sec-
tions given do the conglomerates in the Huronian appear to lie at the
base of the formation, but at varying heights in the series.

The exception referred to above is this: under the head of “ Contact
of Laurentian and Huronian Rocks,” it is stated that in the upward
navigation of the Kaministiquia River

“the first development of the Laurentian series occurs at the second port-
age, about half a mile above the Grand Falls. At the lower end of the port-
age, where the series makes its appearance, the rock resembles a massive
syenite, in some parts red and in others whitish, but is probably a hornblendic
gneiss in which the lamellar arrangement of the constituent minerals is ob-
scure, as the rock gradually passes into such a gneiss. Resting on it conform-
ably there occurs a series of dark greenish-blue or greenish-black slates, the
one rock passing almost imperceptibly into the other. The section occupies
upwards of a quarter of a mile on the river bank, and at the upper end of it,
as well as at the head of the portage, the dip is N. 54° E.... . At each
rapid part of the river above the Grand Falls there is a greater or less develop-
ment of these rocks, most frequently presenting the more distinctly stratified
part of the gneiss. The best exposure of the slates is at the Three Discharges,
about four miles above the Grand Falls, where the rocks are observed to pass
from the gneiss to the slate. . . . . Towards the bottom, near the junction
with gneiss, the slates are of a bluish and occasionally of a brownish color.”
(J. c., pp. 64, 65.)

It would then appear that Huronian in the only localities, except one
problematical one (/. ¢., pp. 52-54, 703), in which it had been seen in
contact with the Laurentian, was conformable with and passed almost
imperceptibly into, or else underlaid, the Laurentian.

An intrusive granite is said to occupy

“a considerable area on the coast of Lake Huron, south of Lake Pakowagaming.
It there breaks through and disturbs the gneiss of the Laurentian series, and

344 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

forms a nucleus from which emanates a complexity of dykes, proceeding to
considerable distances. As dykes of a similar character are met with inter-
secting the rocks of the Huronian series, the nucleus in question is supposed
to be of the Huronian age, as well as the greenstone dykes which are inter-
sected by it.” (J. ¢., p. 58.)

Mr. Logan seems in this report to have abandoned the idea that the
copper-bearing rocks of Lake Superior were of the same age as those
north of Lake Huron, except in some minor districts classed as Huro-
nian; for he calls the Huronian formation the Lower Copper-bearing
rocks, and places the others as the Upper Copper-bearing rocks. These
latter rocks he divides into two groups, and writes of their age as fol-
lows : —

“The precise age of the upper copper-bearing rocks of Lake Superior is a
question attended with some difficulty. Mr. Whitney appears disposed to
regard the whole series from the summit of the sandstones of Sault Ste. Marie
to the base of the Kaministiquia slates as one group equivalent to the Potsdam
formation ; but the suspicion of a want of conformity between the Sault Ste.
Marie sandstones and the trappean rocks beneath, would induce us to separate
the'two:'.. 5. The affinities of the red sandstone of Sault Ste. Marie would
thus appear to bring it into the position of the Chazy rather than the Potsdam
formation ; and if this were established, the copper-bearing portion of the Lake
Superior rocks might reasonably be considered to belong to the Calciferous and
the Potsdam formations.” (J. c., pp. 84-86.)

This is an abandonment of the attempt to determine the age of the
Lake Superior copper-bearing rocks by lithological characters only, and,
so far as Mr. Logan is concerned, a removal of those rocks from the
Azoic series.

In the supplement to this report the labradorite rocks occurring in
the Laurentian series are thought to unconformably overlie the lower
portion of the Laurentian formation, cutting out some limestone bands.
The contacts were not seen ; but, as the labradorite rocks were assumed
to be sedimentary, this replacement of the limestone was held to prove
their unconformability with the Laurentian. (/. ¢., pp. 837-839.)

The same year Dr. Hunt remarked :—

“The so-called granites of the Laurentian and Lower Silurian appear to be
in every case indigenous rocks ; that is to say, strata altered in situ, and still
retaining evidences of stratification. The same thing is true with regard to
the ophiolites and the anorthosites of both series ; in all of which the general
absence of great masses of unstratified rock is especially noticeable.” (Am.
Jour. Sci, 1863, (2) XXXVI. 226.)

CANADA. 345

In the Report of Progress from 1863 to 1866 (pp. 127-129), Mr.
Thomas Macfarlane describes the contact of some supposed Huronian
with Laurentian rocks as follows : —

« The manner in which these Huronian rocks adjoin those of the Laurentian
series may be observed on the north shore between Michipicoten Harbour and
Island. I paid some attention to that point of junction which lies to the west
of Eagle River, the precipitous cliffs to the east of which, consist principally of
diabase schist and greenstone slate. A few miles to the west of these cliffs,
and at a point bearing N. 29° 5° E., from the east end of Michipicoten Island,
the Laurentian granite is penetrated by enormous dykes of dense basaltic
greenstone (having the peculiar doleritic glitter when fractured) which contain
fragments of granite. This greenstone is also seen in large masses, which can
scarcely be called dykes, overlying the granite, and enclosing huge masses of
that rock, one of which I observed to be cut by a small vein of the greenstone.
From this point to Eagle River, those two rocks alternately occupy the space
along the shore, seldom in such a manner as to shew any regular superposition
of the greenstone on the granite, but almost always more or less in contact
with each other. The greenstone, however, becomes more frequent towards
the east, and at Eagle River it has almost replaced the granite, and assumed a
lighter colour, and an irregular schistose structure. The strike of these schists
is at places quite inconstant ; they wind in all directions, and what appear
at first sight to be quartz veins, accompany their contortions. On closer in-
spection, however, of the largest of these, they are seen to be of granite, but
whether twisted fragments of that rock, or really veins of it, is at first glance
very uncertain. Observed superficially they have the appearance of veins,
but they do not preserve a straight course, and bend with the windings of the
enclosing schist. They often thin out toa small point and disappear, and, a
few feet or inches further on in the direction of the strike, reappear and con-
tinue for a short distance. Sometimes a vein thins out at both ends, and forms
a piece of granitic material of a lenticular shape, always lying parallel with the
stratification. Although they are seldom or never angular, they can scarcely
be regarded otherwise than as fragments whose shape has been modified by
contact with the greenstone. . . . . There would seem to be only two ways of
explaining the phenomena above described. Either the granite forms veins,
penetrating the schistose greenstones, in which case the latter are the older
rocks ; or it is in the form of contorted fragments, in which case the inclosing
rocks may be of eruptive origin. The latter supposition seems to be most in
harmony with the facts stated, and with what is known as to the relative ages
of the Laurentian and Huronian rocks. I may here remark that in Foster and
Whitney’s Lake Superior Report (Part II., pp. 44 and 45) analogous phenomena
are described, but the exactly opposite conclusion is arrived at, viz.: that the
granite is in veins, and forms the newer rock. Similar relations are observed at
other points of junction on the north shore, and the peculiar breccia, described
among the greenstones above mentioned, occurs at no great distance from one

346 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

of these. It is remarkable that the greenstone found associated with it is also
basaltic, and this is also the case with the trap occurring at the junction of the
two formations in the northeast corner of Bachewahnung Bay. Here it is
finer grained, but still possesses the glittering fracture of basaltic greenstone.
The Laurentian rock is a highly granitic gneiss, and pieces of it are enclosed in
the black greenstone, which at one place seems to underlie the granite. A red-
dish-grey felsitic rock, with conchoidal fracture, is observed at the point of
junction, Eastward from it banded traps occur, striking N. 55° W., together
with greenstone breccia and conglomerate of the characters already described.
On ascending the hills behind this point a breccia is observed, of which the ma-
trix is greenstone, and the fragments granite. The lines of junction between the
Laurentian and Huronian series, and between these and the Upper Copper-
bearing rocks, so far as observed during the exploration, are given on the
accompanying map. With regard to the succession of the strata, I found my-
self as much at a loss among the irregularly schistose Huronian greenstones, as
among the gneissoid granites of the Laurentian.”

It seems almost incredible that a geologist, who professed to be a
lithologist, should bave been unable to ascertain the relations and rela-
tive age of these rocks, when so many excellent exposures were observed
as he states. His observations show clearly that both formations here
are eruptive, and of the same geological age.

In the Lsguisse Géologique du Canada (Paris Exhibition of 1867,
p. 10) the Huronian is said by Dr. Hunt to repose unconformably on
the Lower Laurentian formation, and probably also on the Upper
Laurentian. It is to be remembered, however, that at the locality on
the Kaministiquia River, in which the Huronian had been seen in con-
tact with the Laurentian, the two were found to be conformable. (Ge-
ology of Canada, 1863, pp. 64, 65.) |

In the same paper (p. 5) Dr. Hunt claimed that the Laurentian com-
prised two distinct series of rocks, of which one reposed with discordant
stratification on the other: these he calls the Lower Laurentian and
Upper Laurentian, or Labradorian.

In the Report of Progress for 1866-69, Mr. James Richardson re-
ports, that in the region north of the lower St. Lawrence River
“the Laurentian gneiss sometimes has little appearance of stratification; the
strike is generally north and south, with dips often approaching vertical. The
strata are all more or less broken, contorted and faulted, The labradorite
rocks rest unconformably on the Laurentian ; they generally strike nearly east
and west, and dip at comparatively moderate angles, with little or no appear-
ance of contortion or disturbance. . . . . The reddish quartzose granitoid rock
of the Laurentian is again met with, offering no evidence of stratification ; and
in one place is seen to be distinctly overlaid by a patch, only a few yards

CANADA. 347

square, of labradorite-rock, shewing considerable varieties in character, and
clearly stratified.” (J. c., pp. 805-307.)

Mr. Richardson’s work failed to prove his conclusions, as the rocks
were not shown to be sedimentary.

In 1868 Mr. J. Marcou wrote regarding the Laurentian and Huronian
formations : —

“The Laurentian system is composed of the Lower Taconic, to which are
added all the unstratified crystalline rocks forming the centre of the Laurentine
Mountains, such as granite, syenite, diorite and porphyry, mixing together
strata and eruptive rocks, an attempt which was unexpected from a strati-
graphical geologist. His Huronian system is formed of a mixture of the St.
Albans group of the Upper Taconic, with the Triassic rocks of Lake Superior,
the trap native-copper bearing rocks of Point Keeweenaw, and the dioritic dyke
containing the copper pyrites of Bruce mine-on Lake Huron.” (Proc. Bost.
Soc. Nat. Hist., 1861, VIII. 246, 247.)

In the Report of Progress for 1870-71, Mr. Robert Bell points out a
case of an apparently conformable junction of the Huronian and Lau-
rentian rocks. He remarks :—

“From the mouth to the sixteenth portage . . . . the river [White River]
runs entirely upon greyish and reddish gneiss, mostly of a massive granitic
character (Laurentian], striking W. 8. W., and dipping northward at angles
varying from 30° to 80°. It is occasionally interstratified with bands of dark
hornblendic schist and very light grey gneiss. Fine dark green hornblendic
schists [Huronian], having the same strike, occur between the sixteenth port-
age and the outlet... .. Similar schists [Huronian], with bands of gneiss,
appear to rest conformably upon the massive gneisses at a short distance north
of the river, all the way from Natamasagami Lake to the mouth (28 miles).”
(1. c.. p. 345.)

Of another locality Mr. Bell, in the Report for 1871-72, states : —

“ Towards the end of the above twenty miles, bands of gneiss become inter-
stratified with the schists, and just at Martin’s Falls the latter have become
entirely replaced by red and grey gneiss, apparently shewing a conformable
passage from the Huronian into the Laurentian rocks, What appeared to be a
similar blending of these formations was noticed last year in the neighbor-
hood of White Lake.” (J. c., p. 110.)

In the Report of Progress for 1872-73, Mr. Bell again states, regard-
ing the rocks northwest of Lake Superior: —
“ As mentioned in the present and in my previous reports on this region, the

Huronian rocks appear to succeed the Laurentian conformably, the distinction
between the two being chiefly of a lithological character. As nearly as the

348 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

distribution of the two series can be mapped by means of our present data, it
would appear that the various bands of each set of rocks in contact with each
other, correspond in their general run, and partake of the same curves and
flexures.” (Ul. c., p. 106.)

Regarding Mr. Bell’s observations Mr. Selwyn states : —

“Tt may, however, be remarked that though the facts observed undoubtedly
lead to the conclusion, as stated by Mr. Bell, that the two series are in conform-
able sequence, yet it is far from improbable that this apparent conformity is
only local, and that the result of a more extended and detailed investigation of
the structure would serve to shew that there is in reality a very considerable
break and much unconformity between the Laurentian gneiss and the over-
lying schistose and slaty strata. As regards the age of these so-called Huronian
rocks, the evidence is not of the most satisfactory kind. While stratigraphi-
cally they rest directly upon highly crystalline and typical Laurentian gneisses,
mineralogically they resemble as closely the chloritic, epidotic and dioritic
strata of the altered Quebec group as they do those which on the shores of
Lakes Huron and Superior are referred to the Huronian series.” (J. ¢., pp.
13, 14.)

In this connection it is ‘well to remember that these rocks were re-
ferred to the Laurentian and Huronian on the same evidence that four
fifths of the rocks so called are, — lithological, namely, —and that the
evidence of conformability given by Mr. Bellis just as strong as any of
the evidence of unconformability; also, that Logan had shown that
the two formations were conformable. Moreover, it had been shown
that the Huronian lay beneath the Laurentian. We do not see that
Mr. Selwyn’s statement has any basis of fact, it being decidedly op-
posed to all the evidence collected by the Canada Survey.

In the Report for 1872-73 (p. 104), Mr. Bell states : —

“The junction of the Laurentian rocks on the north with the ‘Hauronian
schists of the Lake of the Woods on the south takes place on Rat Portage.

The two rocks are seen almost in contact with each other, and have the same
strike and dip.”

Mr. George M. Dawson says of the same locality : —

“The southern end of the path passes over Huronian rocks. ... . At
the water’s edge . . . . they were found to be vertical, with a strike of N.
75° E. About half-way across the Portage, and at its highest part, the rocks
dip N. 17° W. < 48°, and are then immediately succeeded by Laurentian
gneiss, which is granitoid, and of alight pinkish-grey colour ; dip N. 30° W.
< 89°. The junction is so close that one may actually lay the hand upon it,
and the separating line is remarkably straight and even. Followed about
one hundred yards westward, it was found to preserve the course of 8. 67° W.,

CANADA. 349

or nearly that of the strike of both series of rocks, The gneiss at this
distance has a strike of N. 72° E., and the green slate, just across the line
of junction, and only a few yards removed, N. 73° E.” (Report on the Ge-
ology and Resources of the Region in the Vicinity of the Forty-ninth Parallel,
1875, p. 45.)

Mr. Dawson continues : —

“A mile still further eastward .... the Winnipeg River... . falls
northward, across the junction of the Laurentian and Huronian series, through

a narrow passage between rocky cliffs. At the fall, the rock is... . much
hardened and of greenish colour; dip N. 10° W. < 45°. Just below the fall,
the red gneiss again suddenly appears with a dip N. 18° E. 78°... .- Not-

withstanding the close accordance of the strike of both series of rocks, and the
direction of the line of junction, the evidence appears to be nearly conclusive,
_ that the two formations are here brought together by a fault, with an extensive
downthrow southward. If they are thus in contact merely by sharp folding,
the relative position must be reversed, as the dips would carry the slate series
below the gneiss.” (I. ¢., p. 46.)

Mr. Dawson in explaining this line of contact proceeds on the sup-
position that both formations are sedimentary, and hence offers the only
explanation he can and preserve the Laurentian in its supposed position.
Yet, so far as his descriptions go, one or both may be eruptive, which
would explain the observed facts just as well. It is a pity that, with
so much contact observed, he did not ascertain whether the contact was
the rubbing, grinding division-plane contact of a fault; or the contact
produced by one rock laid conformably, or unconformably, upon an-
other, and both folded ; or the close-welded, altering contact of an erup-
tive rock. Had he carefully observed the phenomena of the contact,
he might have built on facts, and thus have been saved much useless
speculation.

Of another locality Mr. Dawson remarks :—

“The rocks ... . belong, as I believe, to an area of much-altered Huro-
PaaS -.-'. The actual junction between the two formations at this point is
concealed by water, but they show a remarkable appearance of conformity, the
next rock seen, being a soft greenish slate, with a dip of 8. 60° W. < 45°.
[The previously given dips of the Laurentian were S. 60° W. < 50°, and S. 45°
W. < 60°.] Itis worthy of notice that similar apparently conformable junc-
tions of Laurentian and so-called Huronian rocks have been noticed by Prof.
Bell, as occurring on the Albany River at Martin’s Falls, and also in the neigh-
bourhood of White River.” (J. c., p. 29.)

Mr. Bell in the Report of Progress for 1877-78, speaking of the

350 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

junction of the Laurentian and Huronian in the Hudson’s Bay district,
says :—

“The junction of the two formations, which appear as usual to be ‘conform-
able with each other, occurs just where the southwest area opens into the main
body of the lake. Here the last of the Laurentian series consists of gray coarse
rough-surfaced quartz and mica-rock. The first rock on what is considered to
be the Huronian side of the boundary between the two series, consists of highly
crystalline dark green hornblende schist, ribboned with fine lines of white
quartz grains. It is identical in character with the hornblende schist which
is usually found at the base of the Huronian bands in the region to the north-
westward of Lake Superior.” (J. ¢., 21,C C.)

It is now necessary to retrace our steps, and give some attention to
the Hastings or Montalban series in Canada. To these Mr. Murray
called attention in the Report of Progress for 1852-53, remarking : —

“In Huntingdon, Madoc, Marmora and Belmont, many interesting diversi-
ties occur in the Laurentian series, but the rocks belonging to it become so fre-
quently and unexpectedly covered up by projecting and outlying masses of the
unconformable fossiliferous formations, in the part investigated, that it is as
yet impossible to give any connected view of their arrangement.” (J. c.,
pp. 103-108.) ‘

In the Report of 1863 the rocks were again described (pp. 32, 33),
Dr. Hunt giving analyses of the limestone, as belonging to the Lauren-
tian (pp. 592, 593).

In the Report for 1866 (pp. 91-113), the Hastings series was once
more discussed by Mr. Thomas Macfarlane, who states that in the pre-
vious reports they have been shown to belong to the Laurentian. He
remarks that some of the conglomerates are “lithologically not unlike
some of the Huronian rocks,” but does not appear to have taken ground
that this series of rocks was newer than the Laurentian, as Dr. Hunt
says he (Macfarlane) did (Azoic Rocks, p. 170). In the same Report
Logan stated that these rocks appeared to be conformable with the
Laurentian series, although they might be a higher portion of the series
than had been met with elsewhere. (/. ¢., p. 93.) :

In 1867 Dr. Hunt stated that the Hastings series reposed in concord-
ant stratification upon the Laurentian gneiss; but that the Upper
Laurentian or Labradorian reposed unconformably, not only on the
Lower Laurentian, but also upon the Hastings series. (Hsquisse G'éolo-
gique du Canada, pp. 5,6). The same year Logan held that the “ inter-
ruption” of a limestone zone in the Hastings series by a labradorite
rock (gabbro, norite), supposed to be Upper Laurentian, showed that

CANADA. 351

this zone belonged to the Lower Laurentian. (Quart. Jour. Geol. Soc.,
1867, XXIII. 253-257.)

In the same paper Mr. H. G. Vennor gives a section of the Hastings
series in ascending order ; this is here given, abbreviated by the omission
of the descriptive portions.

_

. Red felspathic strata.

. Dark-green chlorite slates.

. Whitish highly crystalline limestone.

. Gray silicious or fine micaceous slates.

. Bluish and greyish mica slates.

. Grey and pinkish dolomite.

. Grey micaceous limestone or cale schist.
. Green diorite-slates.

. Reddish granitic gneiss.

Oo ont GS o & WW bO

In the Report of Progress for 1866-69, Mr. Vennor again furnishes a
section of the rocks of the Hastings series, referring to the one given
above, quoted from the Quarterly Journal of the Geological Society, and
using the words “it is here repeated.” (é. c., p. 144.)

The following is the section as given, in ascending order, in the
Canada Report : —
Lower Division. A.

. A great mass of highly crystalline syenitic rock.
. Reddish and flesh coloured granitic gneiss.

. Greyish and flesh-coloured gneiss.

. Crystalline limestone, sometimes magnesian.

® GC Db

MrppieE Division. B.

_

. Hornblendic and pyroxenic rocks.

Urprer Diviston. C,

. Crystalline and somewhat granular magnesian limestone.
. Gray silicious or fine-grained mica-slates.

- Bluish and grayish micaceous slate.

. Gneissoid micaceous quartzites.

. Grey micaceous limestone.

ao 2 w be

Comparison of the sections given by Mr. Vennor will show that there
is hardly any resemblance between the two. No one would ever sup-
pose, unless previously informed of the fact, that the same rocks were
intended to be embraced in them. Particular notice may be called to
the transference of No. 8 of the first section from near its summit to the
middle of the series in the second one.

352 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

The rocks of Division B, as Mr. Vennor says, were
“seen to rest immediately upon the gneisses, Nos. 2 and 3 of Division A, but
whether conformably or not is a question yet to be investigated, as in the locali-
ties where they are best represented, the massive diorites and greenstones, which
form the base of this division, do not offer any clear marks of stratification,”

The rocks of this division were thought to closely resemble the
Huronian. Division C contained Lozoin Canadense, but no evidence of
importance was brought forward to prove its relations to A and B.
Overlying all, Trenton limestones were found.

In the Report of Progress for 1870-71, Division A was regarded by
Mr. Vennor as Laurentian, and B as probably Huronian. He further
states :—

“.The dolomites and schists of division C lie unconformably upon the gneiss
and crystalline limestones of A, while the true position of the diorites and
chloritic schists of division B, appears to be at the base of C; where, however,
they are not unfrequently wanting, suggesting a probable unconformity of
these both with the upper and lower divisions.” Cis mentioned as being “ seen
in contact with the chloritic schists of B, without any apparent unconformity.”
(l. c., pp. 310, 311.)

In the Report of Progress for 1871-72, Mr. Vennor remarks of Di-
vision A :— :

“The age of the granite [A], on which these gold-bearing rocks [B] rest, is
not yet satisfactorily determined. That it is of more ancient date than the
latter, is I think clearly shown by the manner in which they repose upon its
flanks, and conform to its general outline. My own conviction is, that this,
and other like masses of granite, met throughout the Hastings district, repre-
sent eruptions which probably took place towards the close of the Laurentian
period, or at some time prior to the deposition of the greenstones, schists, dolo-
mites and limestones of Divistons B, and C.” (1, ¢., p. 130.)

In the Report for 1872-73, Mr. Vennor remarks : —

“ The red granites [A] also occur in many localities throughout the area just
described, but in a very irregular manner, so as to render it difficult to deter-
mine their age in relation to the other rocks. ... - In the vicinity of the East
and West Mountains in Grimsthorpe, they are unstratified, and often appear
to be of more recent date than the white mica granites, and even than the dio-
rites of division B.” (/. ¢., p. 140.)

In the Report of Progress for 1874-75, Mr. Vennor groups the rocks
of Lanark County as follows : —

I. Mica Schist Group.
II. Dolomite and Slate Group,

CANADA. 353

III. Diorite and Hornblende Schist Group.
IV. Crystalline Limestone and Hornblende Rock Group.
V. Gneiss and Crystalline Limestone Group.
VI. “Embracing coarse orthoclase gneisses, felsites, garnetiferous gneisses,
pyroxenites, crystalline limestones and white quartzo-orthoclase
rock.”

From its lithological characters he thought it probable that the mica
schist group (I.) should be placed near the summit of Division B, and
beneath the gray calce-schists and impure limestones of Division C of the
Hastings series. He also states that the belt of red gneiss (Division A,
Hastings series)

“separates the mica-schist group (I.) from the dolomite and slate group (II.).
It appears to overlie the former, and invariably shows the same constant dip to
the south-east and east. But extended observations on its course for a number
of miles seem rather to show that its present position is due to an uplift or
overturned elevation of an older gneiss series. . . . . The rock is a fine-grained
granitic gneiss, composed largely of flesh-coloured feldspar and greyish quartz,
and differing in no respect from most of the gneisses heretofore described as
Lower Laurentian.”

Group V. was fotind apparently overlying Group IV., the limestone
group. It would seem that Hozodn had been found in Groups III. and
IV. (l. ¢, pp. 105-165.)

Mr. Selwyn, the next year, in quoting from Mr. Vennor’s work,
writes : —

“The geological structure of this section of the country is exceedingly intri-
eate, but when worked out will be both important and instructive. It is now
apparent that the rock groups referred to in my last report as I. IT. III. and
IV., constitute together the lower members of one great crystalline series,
_ while V. and VI., of the same report, constitute its upper members. These
groups include the so-called Hastings series of the earlier reports, and the

Throughout this region the lowest rock is a massive red, orthoclase gneiss, in
which, as a rule, no bedding planes can be recognized, and the groups above
enumerated overlie it in, probably unconformable sequence. In many places,
in connection with the Bonnechere limestone trough, labradorite rocks were
observed, but these appear to be quite conformable with the rest of the series.”
(Report of Progress, 1875-76, p. 4.)

In the Report of Progress for 1876-77, Mr. Vennor remarks : —

“Now these rocks represent Division B, and a part of C, of the Hastings
series which have been compared, by some investigators, to the Huronian, but
VOL. VII. —No. 11. 23

354 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

which I have now shown are really only the westward extension of the diorites
hornblende schists and mica-slates of Lanark and Renfrew counties, or, in
other words, of Groups I., II. and III. But these last, as we have also shown,
are simply a low portion of the gneiss and limestone series which has always
been looked upon as typical Laurentian. Consequently, we are finally led to
the important conclusion that the Hastings series is not, as it has up to the
present been considered, the most recent, but rather the oldest portion of the
great system of rocks we have been investigating from the year 1866 to 1875
inclusive. Further, it was clear that this great crystalline, gneiss and lime-
stone series rested upon a still older gneiss series, in which no erystalline lime-
stones had yet been discovered. ‘This series is referred to as Division A in the
Report of Progress, 1866-69, where, however, limestones are, incorrectly, men-
tioned as occurring init. It... . is the rock which may be said to form the
back-bone of Eastern Ontario, and the nucleous around which have been de-
posited all succeeding formations. This, then, is undoubtedly Archean and.
Lower Laurentian, and consequently the crystalline limestones and gneisses
constitute a series which would come in beneath Sir W. E. Logan’s Upper Lau-
rentian or Labradorite series. As regards the existence of this latter as a dis-
tinct formation, however, I entertain grave doubts.” (J. ¢., p. 254.)

As a reason for these doubts he points to several localities where he
says the labradorite (Norian) rock is interstratified with the limestones
of this series, and to others where it is conformable with the Hastings
series. Mr. Vennor concludes : — |

“So far, then, my investigations in Eastern Ontario show but three great
divisions or groups of rocks, namely :—

“1, A great eneissic and syenitic series, without limestones.

“9. A thinner gneissic series with labradorites and limestones.

“3. Lower Silurian (Potsdam to Trenton).” (U. ¢., p. 277.)

In 1877 Mr. Vennor said (Am. Jour. Sci., 1877, (3) XIV. 313-316) : —

“ We find that there still exists a great Azote formation, consisting of syenite
and gneiss (?) without crystalline limestones. In this there are but little indi-
cations of stratification. Occasionally a limited surface presents an approach
to an obscure stratification, but this does not appear to be due to the deposition
of sediment. This rock forms the back-bone of Canada. On it there has, been
deposited a great series of gneisses, schists, slates, crystalline limestones and
dolomites, which, although heretofore grouped with the former, is clearly dis-
tinct and unconformable. . . . . Hozoon Canadense belongs undoubtedly in the
main to the highest band of crystalline limestone yet found... . . I may
simply state that I consider both the Huronian and Upper Laurentian of Sir
W. E. Logan to belong rightly to my second division, which I must for the
present call Upper Laurentian. . . . . I have found Labradorite rocks clearly
interstratified with several of my bands of limestone, and I fail entirely to dis-

CANADA. 355

cover Sir William’s upper distinct system — yet I have been over the same
ground. The Huronian and Hastings series of rocks I believe to be simply an
altered condition, on their westward extension, of the lower portion of my
second system.”

Retracing our steps, we see that in 1870, under date of December 13,
1869, Dr. Hunt held that the Zozoién Canadense of Madoc, and hence
the Hastings series, occurred in the Laurentian. (Am. Jour. Sci., 1870,
(2) XLIX. 75-78.) Later, under date of May 10, 1870, he referred the
Hastings series to the Terranovan, but it would seem that, when the
term Terranovan series was first employed by him, it was regarded as
being, in part at least, Potsdam. He remarks :—

“ From these investigations of Mr. Murray we learn that between the Lau-
rentian and the Quebec group, there exists a series of several thousand feet of
strata. including soft bluish-grey mica-slates and micaceous limestones, belong-
ing to the Potsdam group; besides a great mass of whitish granitoid mica-
slates, whose relation to the Potsdam is still uncertain. To the whole of these

we may perhaps give the provisional name of the Terranovan series, in allusion
to the name Newfoundland.” (Am. Jour. Sci., 1870, (2) L. 85, 87, 88.)

To this series he referred the White Mountain rocks, as well as certain
rocks in New Brunswick.

In the Twenty-first Annual Report of the Regents of the Univer-
sity of New York, Dr. Hunt remarked of the Hastings series (1871,
p- 48) :—

“Tn the county of Hastings, in the province of Ontario, not less than 21,000
feet of strata, consisting of crystalline schists, limestones and diorites, are found
resting conformably upon the Laurentian series.”

In a postscript (/. c., p. 98) he states : —

“More recent researches by the Geological Survey of Canada have shown
that the rocks of Hastings county . . . . rest unconformably upon the Lau-
rentian, and belong to one.and possibly two distinct systems. The upper and
larger portion consists in a great part of mica-schists and micaceous limestones,
while at the base are great masses of dioritic and hornblendic schists with
iron ore, possibly of Huronian age.”

In some remarks of Dr. Hunt, in 1873, it was stated :—

“As regards the Norian, which had once been joined by the Laurentian,
Dr. Hunt had elsewhere shown that we had reason for suspecting that it might
be more recent than the Huronian, and possibly than the Montalban, a conclu-
sion which appeared to be confirmed by the facts made known by Hitchcock.”
(Proc. Bost. Soc. Nat, Hist., 1873, XV. 310.)

THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

oS
or
fap)

In 1875 Dr. Hunt remarked of the White Mountain or Montalban
series (Hastings series) :—

“ These ancient rocks are also largely represented in Hastings County, Ont.,
where they occupy a position between the Laurentian and the fossiliferous
limestones of the Trenton group, and are the equivalents of similar limestones

and micaceous quartzites in Berkshire County, Mass. and elsewhere in New
England.” (Proc. Bost. Nat. Hist., 1875, XVII. 509.)

In 1878 Dr. Hunt referred the limestones of the Hastings series to
the Lower Taconic (Taconian). (Proc. Bost. Soc. Nat. Hist., 1878, XIX.
278; Preface to Second Edition of Chemical Essays, pp. xxii, xxvi.) In
the last quoted work the Hastings limestones and slates are said to lie
between the Huronian and Trenton. In 1879 the Norian was said
by Dr. Hunt to rest unconformably upon the gneisses and crystalline
limestones of the Laurentian, and held to be older than the Huronian.
The Huronian was also said to rest unconformably on the Laurentian,
on the north shores of Lakes Huron and Superior, thus rejecting the
positive evidence given by Messrs. Logan and Bell of their conformable
relations (in one case underlying however) on the north side of Lake
Superior.

The rocks of the Montalban series “are believed to be younger than
the Huronian, although some geologists have supposed them to be older.”
(The Geologist’s Travelling Hand-Book, pp. 10-13.) The Taconian in
the previous year was said to be found reposing alike on the Lauren-
tian, Huronian, and Montalban, and to be overlain, in apparent uncon-
formity, by the Upper Taconic, which was considered to be identical with
the Quebec group of Logan. (Nature, 1878, pp. xviii, 444.)

In the Report of Progress for 1877-78, Mr. Selwyn made some re-
marks on the Quebec Group and the older Crystalline Rocks of Canada.”
(A., pp. 1-15.)

He separated the Quebec into three groups : —

1. The Lower Silurian group.

2. The Volcanic group, probably Lower Cambrian.

3. The Crystalline Schist group. (Huronian ?)

Mr. Selwyn further said :—

“Tn any case, I think, there are very few who would agree with Dr. Hunt
in the general proposition that the diorites and serpentines of the Quebec
group are of sedimentary origin, and the amygdaloids altered argillites ; unless
all contemporaneously interbedded volcanic products are to be considered as of
sedimentary origin, the Quebec group might be said to present some of the most

CANADA. 357

marvellous instances on record of ‘ selective metamorphism.’ But whether this
is so or not, there seem to be no good grounds for assigning either an age or an
origin to the cupriferous diorites, dolerites, and amygdaloids of the Eastern
Townships different from that of the almost identical rocks of Lake Superior.”

Of the Hastings series he says : —

“The gradual progress of the work, however, from west to east has now, I
think, conclusively demonstrated that the Hastings group, together with the
somewhat more crystalline limestone and gneiss groups, .. . . form one great
conformable series, and that this series rests quite unconformably on a massive
granitoid gneiss.”

Of the Norian rocks he said : —

“Tn not one of the several areas where they are known to occur in Canada,
have they yet been mapped in detail, and even their limits, as indicated on the
geological map, are more or less conjectural. . . . . Professor Hitchcock shews
that they rest unconformably on the upturned edges of the ‘ Montalban’ gneisses,
leading to the conclusion that the gneisses of the White Mountains are older
than the ‘ Norian, whereas Dr. Hunt, solely, I believe, on mineralogical con-
siderations, supposes these same ‘ Montalban’ gneisses to constitute a system
newer than the Huronian, Here, then, as in the Hastings region, we find
theory and experience at variance. . . . . If it is admitted — which, in view
_of the usual associations of Labrador feldspars, is the most probable supposi-
tion —that these anorthosite rocks represent the volcanic and intrusive rocks
of the Laurentian period, then also their often massive and irregular, and
sometimes bedded character, and their occasionally interrupting and cutting
off some of the limestone bands, as described by Sir W. E. Logan, is readily
understood by one who has studied the stratigraphical relations of contempo-
raneous volcanic and sedimentary strata, of paleozoic, mesozoic, tertiary and
recent periods. Chemical and microscopical investigation both seem to point
very closely to this as the true explanation of their origin. That they are
eruptive rocks is held by nearly all geologists who have carefully studied
their stratigraphical relations. .... When we recall the names of Dahl,
Kerulf and Torrell in Norway, Maculloch and Geike in Seotland, Emmons,
Kerr, Hitchcock, Arnold Hague, and others in America, all of whom consider
these norites as of eruptive origin, we may well pause before accepting Dr.
Hunt’s conclusions respecting them, and that they should often appear as
“bedded metamorphic rocks,’ .... is quite as probable as that we should
find the mineralogically similar dolerites occuring in dykes and bosses, and in
vast beds interstratified with ordinary sedimentary deposits of clay, sand, etc.,
as we do over wide areas in Australia and elsewhere. In conclusion, I may
say that I fail to see that any useful purpose is accomplished, in the present
stage of our knowledge of the stratigraphical relations of the great groups of
rocks which underlie the lowest known Silurian or Cambrian formations, by
the introduction of a number of new names such as those proposed by Dr.

58 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ise)

Hunt for systems which are entirely theoretical, in which category we may in
my opinion include the Norian, Montalban, Taconian and Keeweenian. These,
one and all, so far as known, are simply groups of strata which occupy the
same geological interval, and present no greater differences in their physical and
mineralogical characters than are commonly observed to occur both in forma-
tions of the same epoch in widely separated regions, and when physical acci-
dents, such as contemporaneous volcanic action or subsequent metamorphism
have locally affected the general character and aspect of the formation within
limited areas. . . . . Unfortunately in Canadian geology, hitherto, stratigraphy
has been made subordinate to mineralogy and paleontology, and, as the result,
we find groups of strata which the labours of the field geologists during the
past ten years have now shewn all to occupy a place between Laurentian and
Cambrian, assigned to Carboniferous and Upper Silurian in New Brunswick
and Nova Scotia, to the peculiar paleontological Lévis group and its subdivis-
ion, Lauzon and Sillery, in the Eastern Townships, and to Lower and Upper
Laurentian, Huronian, Lower Silurian and Triassic on the north side of the
St. Lawrence valley and around Lake Superior, The same system of minera-
logical stratigraphy is now further complicating and confusing the already
quite sufficiently intricate problem by the introduction of the new nomencla-
ture I have referred to, and in some cases these names are applied regardless of
and in direct opposition to well ascertained stratigraphical facts. A similar
unfortunate instance of paleontological stratigraphy is found in the history of
the Quebec group ; and especially in the late introduction in it of the belt of
supposed Potsdam rocks, about which I have already stated my opinion. In
the reconstruction of the geological map of Eastern Canada, — and in this I
include the country from Lake Winnipeg to Cape Breton and Labrador, — ren- _
dered necessary by the present state of our knowledge, I should propose to
adopt the following divisions of systems to include the groups enumerated : —
“JT. LAURENTIAN: '

“To be confined to all those clearly lower unconformable granitoid or
syenitic gneisses in which we never find interstratified bands of calcareous,
argillaceous, arenaceous and conglomeratic rocks.

“TI.. HURONIAN:

“To include — 1. The typical or original Huronian of Lake Superior and
the conformably —or unconformably, as the case may be — overlying upper
copper bearing rocks. ;

“2. The Hastings, Templeton, Buckingham, Grenville and Randon crystal-
line limestone series.

“3. The supposed Upper Laurentian or Norian.

“4. The altered Quebec group, as shewn on the map now exhibited, and
certain areas not yet defined between Lake Matapedia and Cape Maguereau in
Gaspé.

“The Cape Breton, Nova Scotia and New Brunswick pre-Primordial sub-
crystalline and gneissoid groups.

CANADA. 359

“TIT. CAMBRIAN :

“Tn many of the areas, especially the western ones, the base of this is well-
defined by unconformity, but in the Eastern Townships and in some parts of
Nova Scotia it has yet to be determined. The limit between it and Lower
Silurian is debatable ground, upon which we need not enter. . . . . One point
I wish particularly to insist on is, that great local unconformities and lithologi-
cal differences may exist without indicating any important difference in age,
especially in regions of mixed volcanic and sedimentary strata, and that the
fact of crystalline rocks (greenstones, diorites, dolerites, felsites, norites, &c.,)
appearing as stratified masses and passing into schistose rocks, is no proof of
their not being of eruptive or volcanic origin — their present metamorphic or
altered character is, as the name implies, a secondary phase of their existence,
and is unconnected with their origin or original formation at the surface, but
is due partly to original differences of composition and partly to the varying
physical accidents to which they have, since their formation, respectively been
subjected.” (J. c., pp. 1-15 A.)

Mr. Selwyn’s views were discussed, and in part objected to, by Mr.
Thomas Macfarlane. (Canadian Naturalist, 1879, (2) IX. 91-103.)

Dr. Hunt very ingeniously derives comfort from the preceding paper
by ignoring most of it and claiming : —

“The pre-Cambrian age of these crystalline schists in Eastern Canada has
now been clearly proved by the . . . . recent stratigraphical studies of Selwyn,
as announced by him in 1878.” (Proc. Am. Assoc. Ady. Sci., 1879, XXVIII.
286.)

In 1879 Dr. Dawson remarked that

“the idea that the Middle Laurentian, the horizon of Eozoon Canadense and of
the great Phosphate and Graphite deposits, is identical with the Hastings
group, or with the Huronian, has, I am fully convinced, after some study of
the Lake Huron, Madoe and St. John exposures of these formations, no foun-
dation in fact.” (Canadian Nat., 1879, (2) IX. 180.)

Dr. Dawson, however, gave no proof of this statement, while Mr.
Vennor had worked out the subject according to the stratigraphical
methods of the Canadian Survey, —a labor of ten years ; this is better
than an unsupported assertion.

VOL. VII. —wno. 11, 24

360 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

NEW BRUNSWICK.

In this Province it is not necessary to go back in the geological his-
tory earlier than the first edition of Principal J. W. Dawson’s Acadian
Geology, for in his writings and those of Messrs. Bailey and Matthew
nearly all the evidence bearing on our subject is to be found. The
methods of work appear to be the same as those of the Canadian Sur-
vey, and therefore similar results were to be expected.

In 1855 Dr. J. W. Dawson, on lithological grounds, would have re-
ferred the rocks in the vicinity of St. John to the Lower Carboniferous ;
but on account of the statement of Dr. Gesner, that similar rocks un-
derlie the Carboniferous sandstones, he says, “I must be content in the
mean time to consider them as silurian rocks of: uncertain age.” (Aca-
dian Geology, Ist ed., p. 324.)

Later he states regarding these rocks : —

“The limestone and its associated shales underlie unconformably the Lower
Carboniferous conglomerate... . . This arrangement is general throughout
the belt to which the St. John rocks belong. The whole of the beds of the St.
John group, appear to be conformable to one another, and to constitute one
formation.” (Canadian Nat. and Geol., 1861, (1) VI. 164.)

From the resemblance of these rocks to the Devonian of Gaspé, and ;
from the plants found in them, he considers them all to be of that age.
Later he writes regarding this entire series of rocks : —

“The Devonian age of the upper members of this great series of beds I re-
gard as established by their fossils, taken in connexion with the unconformable
superposition of the Lower Carboniferous conglomerate. The age of the lower
members is less certain. They may either represent the Middle and Lower
Devonian, or may be in part of Silurian age.” (Quart. Jour. Geol. Soc., 1862,
XVIII. 303.)

In the later editions of this Acadian Geology (1868, 1878), he fol-
lows in the main Messrs. Bailey and Matthew; therefore we need only
incidentally refer to those editions.

Mr. Geo. F. Matthew, in 1863 (Canadian Naturalist, 1863, (1) VIII.
241-260), divided the rocks at St. John into the following groups : —

“Ist Portland Series containing fragments of plants in the upper beds ;
2d, Coldbrook Group; 3d, St. John Group, containing lingula, a conchifer,

9

NEW BRUNSWICK. 361

annelides, and coprolites ; 4th, Bloomsbury Group ; 5th, Little River Group,
containing numerous plants, several crustaceans, and wings of insects, ete. ;
6th, Mispeck Group.” (J. c., pp. 244, 245.)

He states that no proof has been observed that the St. John group is
unconformable with either the overlying or underlying rocks. (/. ¢.,
p. 247.) The Mispeck group is said to contain fragments like the lower
slates of the Coldbrook group. (J. c., p. 253.) The rocks in the vicin-
ity of Black River, to which the name Coastal group was afterwards
given, were here classed under the Little River group. This group
was divided into two parts, the lower called the Dadoxylon sandstone,
and the upper the Cordaite shales. He says it seems clear that the
Black River rocks mentioned above
“form a part of the Upper Devonian series, because, — 1st They overlie the
Dadoxylon sandstone conformably (or nearly so). 2nd They underlie car-
boniferous deposits unconformably. 3rd They partake of the flexures of the
Devonian series, which preceeded the formation of the Lower Carboniferous
‘conglomerate. .... I have connected them with the cordaite shales, but it is
quite possible that the upper part may be altered beds of the Mispeck group.”
(I. c., pp. 252, 253, 256-258.)

Mr. Matthew’s statements regarding the age of the entire series are
far from being clear. In some places he appears to regard them as
Devonian, in others as being in part Devonian and in part Silurian.
His language admits of no other interpretation than that he regarded
the Coldbrook group as being of Devonian age. (/. c., pp. 258, 259.)

In 1865 the same geologist referred the Portland series to the Lau-
rentian and the Coldbrook group to the Huronian. The Coldbrook
rocks were placed in two divisions, a lower and an upper. The upper
division is said to be “largely composed of erupted materials, diorites,
_ tufas, and volcanic mud,” the same as the Huronian of Canada, and to
be “conformably surmounted by the lowermost strata of the Lower
Silurian formation.”

He further remarks : —

“Considering, therefore, the origin of these deposits as well as their position
relative to the more ancient series and the Lower Silurian beds above, we have
little hesitation, notwithstanding that the latter are conformable to them, in
assigning these semivolcanic sediments to the ‘ Huronian series’ of Logan.”

The St. John group was regarded by him as being the equivalent of
the Potsdam, Calciferous, and possibly Chazy formations.
A series of rocks which cover an area of about seventy miles long and

0362 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

twenty wide, stretching northeastwardly from Passamaquoddy Bay, and
including the highest eminences in the southern counties, was assigned
to the Upper Silurian. The Bloomsbury, Little River, and Mispeck
groups were placed in the Middle and Upper Devonian, and were said to
rest unconformably upon the Laurentian, Huronian, Lower Silurian,
and Upper Silurian strata, and it was stated that the Primordial shales
appear to overlie the Huronian without any appreciable discordance be-
tween the two. (Quart. Jour. Geol. Soc., 1865, XXI. 422-434.)

In Messrs. Bailey, Matthew, and Hartt’s “ Observations on the Geol-
ogy of Southern New Brunswick,” 1865, a work prepared for the press
by Prof. Bailey, the rocks referred to the Huronian and Laurentian ages
are so placed on theoretical and lithological grounds. Regarding the age
of the Portland group, here assigned to the Laurentian, he writes : —

“Tt might readily be supposed that the extreme metamorphism exhibited
by the rocks of the Portland Group would be accepted as conclusive evidence
of their great antiquity. Indeed the fact of such antiquity could scarcely
have been doubted, were it not for the intimate association and almost entire
conformability between the beds of this and the overlying groups, which have
heretofore induced all the observers who have examined the district to link
them in a single series. As the latter are unquestionably of Upper Devonian
age, the beds of Portland were supposed to represent either a portion of the
Lower division of the same formation, or possibly the upper part of the Silu-
rian’? y(/. ¢...p- 18:)

The reasons for assigning it to the Laurentian are, in brief, partly
lithological, and partly because it seemed to them probable that the
Coldbrook group was Huronian, and therefore the syenites (Portland
group) must be Laurentian. (/.¢., p. 18.) Between the Coldbrook
group and the underlying syenite and limestone, Prof. Bailey states
that Mr. Matthew observed “evidence of slight unconformability.”
(U.c., p. 49.) Again he remarks : —

“ During the deposition of the various rocks referred to the Azoic and Silu-
rian Ages, a prolonged period of repose prevailed throughout the districts
where these rocks occur, broken only by the volcanic activity which marked
the epoch of the Coldbrook Group. ... - Through all these vast intervals of
time no evidence exists to show that any violent disturbances broke the general
quiet, unless it be the folding of the Portland and Kingston rocks, and even
this may have been the result of a later date. Each formation was quietly
deposited upon that which preceded it, the almost entire conformability which
now marks their succession being conclusive evidence that no period of marked
upheaval prevailed between the deposits of one epoch and those of another.”
(l. ¢., p. 50.)

NEW BRUNSWICK. 363

Of the Bloomsbury group, which later was united to the Coldbrook
group, he states : —

* The association of the Bloomsbury rocks with the Groups which are to fol-
low, is conclusively proved by the general similarity of their deposits, by their
entire conformability, and the absence of such perfect conformability between
these and the Primordial (or Saint John) rocks below. As the overlying beds
have been shown to be unquestionably of Upper Devonian age, there can be no
hesitation in referring the Bloomsbury Group to the same horizon.” (J. c.,

p- 53.)

The Coldbrook group, while nominally underlying the St. John
group, was found in another place overlying it. In this locality it
seems that the rocks were recognized as Coldbrook (Huronian) from
lithological characters, and their stratigraphical position explained by a
reversed folding. (/. ¢., pp. 23, 28, 29.)

In regard to the age of the Kingston group, which with the Mica
Schist formation appears to be the Upper Silurian of Matthew, it is
said : —

“We have only the general lithological characters and the stratigraphical
relations upon which to rely for the determination of this important question.
As the conclusions derived from these two independent sources accord exactly,
we may consider the position of this formation as established with some degree
of certainty.” (J. c., p. 38.)

Again he states, quoting from Mr. Matthew : —

“ Their relations to other groups, as well as their appearance when altered,
indicate that the Kingston rocks and their associates may be provisionally
looked upon as Upper Silurian, though Middle Silurian and Lower Devonian
beds may also occur. The only objection to this view is the absence of such
hard rocks along the outcrops of the soft Lower Silurian strata in Saint John
County, where these latter are covered by deposits of Upper Devonian age.
This may be accounted for by denudation subsequent to their deposition, or by
supposing an elevation of the older rocks above the sea when those of Kingston
were being formed.” (1. ¢., p. 39.)

The arrangement of the formations in this report, it has been seen
from the above, is as follows :—

LAURENTIAN. The Portland group, if it is not Huronian, doubt existing.
Huronian. Coldbrook group, probably.
PoTsDAM AND QuEBEC. St. John group.
The Kingston group.

UPPER SILURIAN. | Limestones of Dalhousie.

364 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

LowER DEVONIAN. Possibly some portion of the Kingston group,
Mispeck group.

Upper DEVONIAN. Little River group.
Bloomsbury group.

In a paper presented to the American Association for the Advance-
ment of Science (1869, XVIII. 179-195) by Messrs. Bailey and Mat-
thew, it is remarked that “several hills of crystalline felspar rock,
associated with hypersthene,” were, on the authority of Dr. Hunt, re-
ferred to'the Labrador or Upper Laurentian series. (/. ¢., p. 181.) The
Kingston series the authors were inclined to regard as Upper Silurian
and Devonian. The overlying formations below the Carboniferous, ex-
cepting in their subdivisions, and being classed as Siluro-Devonian, re-
mained about as in 1865. This paper was revised up to April, 1870.

In a joint report by Messrs. L. W. Bailey and G. F. Matthew (Geol-
ogy of Canada, Report of Progress, 1870-71, pp. 13-240) numerous
changes were made in the supposed sequence of the formations, Dr.
Hunt having worked in the field with them. Lithological evidence had
been thought sufficient authority for enlarging the amount of Lauren-
tian rocks; and the finding of a few pebbles in some of the granitoid
masses was regarded as proof that they were altered conglomerates.

The rocks referred, on lithological evidence, to the Huronian, were
divided into three groups: the Coldbrook, Coastal, and Kingston. The
former was found in some places to overlie the Primordial or St. John
group, and to conformably underlie rocks of Devonian age, to which.
age these rocks (the Bloomsbury group) had formerly been referred.
However, lithological characters being then regarded as more weighty
than stratigraphical ones, this difficulty, together with some others, was
surmounted in the following manner.

“ Prior to the work of the present survey, the river St. John, at the Suspen-
sion bridge, was considered as marking the extreme western limit of the Huro-
nian rocks of St. John County, the only sediments noticed to the westward of
this point, which bore much resemblance to them, being supposed, on strati-
eraphical grounds, to be more recent. .... Recent observations, however,
have led us to the conclusion that a part of these supposed more recent sedi-
ments are in reality the Huronian strata brought up by a fold, and by an over-
turn of the whole series made to rest upon newer strata. ... . The diorites
and schists of Bloomsbury Mountain, although apparently resting upon the
slates of the St. John group, and overlaid by Devonian sandstones, which con-
form to them in dip and strike, are now also regarded as Huronian strata.
. . - » On both sides of Musquash Harbor a series of hard green epidotic sub-
crystalline schists, sometimes with dark green serpentine, may be seen resting

NEW BRUNSWICK. 365

upon black carbonaceous crumbling shales. . . . . These latter dark colored
rocks resemble very closely some portions of the St. John group as seen in the
city of St. John, and are supposed to be continuous with them through a belt
of similar rocks, extending across the peninsula of Pisarinco, and coming out at
Mill Creek in Pisarinco Harbor. In this view, it is probable that the structure
indicated in this group at St. John, and to be presently noticed, will hold good
here also, viz.: That the St. John group is inverted upon itself, and that the
green crystalline schists, though overlying that group, are in reality more an-
cient and probably of Huronian age.” (J. c., p. 60.)

Of the Huronian rocks at Ratcliffe’s mill-stream it is stated that

“they overlie the Primordial strata, both formations occupying a nearly verti-
eal position, with a slight southward inclination, and both being inverted.”
(U. ¢., p. 63.)

Of the Bloomsbury group it is again remarked : —

“Tn our earlier publication, this hill . . . . has been referred, from the fact
of its overlying the slates of the St. John group, to the Devonian series ; but
the close resemblance in aspect borne by the rocks composing it to those so
largely developed to the north and north east, from which they are separated
only by a narrow valley, renders it more probable that the great mass of strata
in this hill is of Huronian age, and that, though here apparently resting upon
the Primordial strata (which in the valley alluded to dip southerly under
Bloomsbury Mountain) they are in reality more ancient than these latter, and
are here brought up along a line of fault in a similar manner to those of
Ratcliffe’s millstream.” (J. c., pp. 63, 64.)

The upper part of the Coldbrook group, from its conformably under-
lying at other places the St. John group, and from its containing peb-
bles supposed to have been derived from the lower portion of the
Coldbrook group, was regarded as forming the base of the Primordial
or St. John group, (/. ¢., p. 59,) an unfossiliferous portion of the latter.
As we have seen before, part of the Coldbrook group was found resting
on the St. John group; the latter was supposed to have been inverted
upon itself, which would explain the fact that Huronian rocks were
overlying Primordial ones. (/. ¢c., pp. 136-139.)

Of the rocks of the Coastal group it is said that they

“have been found to overlie, at several points, strata of Upper Silurian and
Lower Devonian age. Hence, those occurring along the coast were, in our re-
port on the geology of Southern New Brunswick, described in connection with
the Devonian rocks of St. John County, under the denomination of the Coastal
group, Dr. Hunt, however, who has examined a large number of specimens
collected from these rocks, and has visited a part of the districts in which they
occur, is of opinion that their lithological aspect is such as to indicate much

366 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

greater antiquity. In the presence of diorites, felsites and other crystalline
rocks, he finds this series to resemble the Huronian strata of St. John County.
Portions of it do indeed correspond in the appearance of the beds to the Huro-
nian of that county, but the series of the coast is much more voluminous than
the resembling parts of the Coldbrook group, and contains conglomerates, lime-
stones, micaceous slates, feldspathic grits, etc., which have not been recognized
among the Huronian rocks of St. John County, first described as the Coldbrook
group.” (I. c., p. 83.)

In this connection it may be well to remember that later Dr. Hunt
acknowledged that at that time his ‘opportunities for studying the
Huronian had been very imperfect.”

Again Messrs. Bailey and Matthew say :—

“ These Devonian sediments appear to dip beneath those of the Coastal type
at those points where the two have been observed together, but, as the latter
are lithologically unlike those of the Devonian series, and do strongly resemble
those elsewhere referred to the Coastal group, we suppose that the appearance
alluded to is due to a dislocation.” (J. ¢., p. 94.)

Again, of the Coastal rocks in another locality : —

“Their superposition on the Dadoxylon sandstone, however, being probably
the result of a fault and overlap, they are considered as pertaining to the same
horizon with the strata already described along the coast westward of St.
John, and in Charlotte County, to which the designation of the Coastal group
has been given.” (J. ¢., p. 98.)

It is also stated that, although Upper Silurian strata were found “ in-
tercalated with the Kingston rocks, the intimate association of the two
is evidently accidental” ; hence the Kingston rocks are Huronian, espe-
cially as the Coastal group overlies them. How the “accidental inter-
calation”” could occur between Huronian and Upper Silurian rocks is
not explained.

We thus see that, while the Portland group remains in the Lanren-
tian, the Bloomsbury group, formerly regarded as Upper Devonian, is
placed in the Lower Coldbrook group; the Coldbrook group divided
into two portions, and the upper one assigned to the St. John group ;
the Kingston group taken from the Upper Silurian and Lower Devo-
nian, and placed above the Lower Coldbrook in the Huronian; and
the Coastal group formed from part of the Little River group of the
Upper Devonian and placed in the Huronian above the Kingston group.

In this way two groups of rocks are intercalated between the two
members of the Coldbrook group. It is necessary to remember, while

NEW BRUNSWICK. 367

observing this extraordinary rearrangement of the rocks in Southern
New Brunswick, throwing them from 8,000 to 15,000 feet perpendicu-
lar, that it has been stated all along that the Azoic and Silurian ages
were ages of stability and repose, excepting some volcanic action, and
that the formations were conformable to one another, with the possible
exception of a slight unconformability between the Portland and Cold-
brook groups. It would seem, then, that lithological resemblances —
especially if accompanied by the dictum of Dr. Hunt — were regarded
as being more important than stratigraphical facts. There does not
appear to be any evidence of faults or overturns; but these were im-
agined in order to explain the resemblance in lithological characters, and
carry out the views of the Canadian geologists. The language of Messrs.
Bailey and Matthew admits of no other possible construction.

The natural explanation of the lithological resemblances seems to us
to be, that similar eruptive materials were originated in different ages.
Such faults and overturns should by no means have been introduced,
unless some evidence could be brought forward of their actual exist-
ence.

In the Report of Progress for 1876-77, Mr. Matthew regards the
Coastal group as Laurentian, and the Kingston group as partly Upper
and partly Lower Silurian. At one place this group is said to uncon-
formably overlie the St. John group, and to contain pebbles probably
derived from it. (/. ¢., pp. 334-350.)

In the Report of Progress for 1876-78, the Kingston series is regarded
by the same gentleman as Upper Silurian on account of palzontologi-
eal evidence, although lithologically it appears to be Huronian, and to
dip beneath that group. (/.c¢., p. 6 E.)

In Prof. Bailey’s report, in the same volume, the Coldbrook and
Coastal groups remain in the Huronian, and the Upper Coldbrook
series is taken away from the St. John group, and replaced in the Hu-
ronian below the Coastal, on account of the unconformability of certain
rocks supposed to belong to the series. (/. ¢., pp. 28, 29 DD.)

The Huronian is conformably interbanded with the Devonian rocks
at Bloomsbury Mountain and westward from Black River; but that this
does not prove that they belong to the same series is said to be shown
by the conglomerates of the Devonian being largely made up of débris
from the Huronian, and by the absence of conformability in some places.
It would seem that in much of the district in question Prof. Bailey has
no other than lithological evidence to prove that he is dealing with
Devonian strata. (/. ¢., pp. 21-23 DD.) The statement that the De-

368 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

vonian conglomerates contain pebbles from the Huronian could only
be accepted after a careful examination of the rocks in question by a
competent lithologist.

Mr. R. W. Ells, in the same volume, describes some Huronian and
Laurentian rocks, claiming that they are unconformable, and that
“in many places a gradual transition can be traced from the green
slates through schists, felsites and gneisses to the syenites.” (/. ¢., p. 4
DD.) No evidence is advanced to prove either statement ; and in re-
gard to the latter one it is to be wished that some of the places where
these phenomena can be seen might be pointed out, so that the actual
existence of. such a transition might be demonstrated. The rocks de-
scribed by Mr. Ells as Laurentian and Huronian were in 1865 assigned
to the Devonian, but in 1871, under the divisions of Coldbrook, Coastal,
and Kingston, were included in the Huronian by Messrs. Bailey and
Matthew.

In the Report on the Geology of Canada for 1878-79 is a contribu-
tion by Messrs. Bailey, Matthew, and Ells. In this the Laurentian or
Portland rocks are divided into two groups, one of which is regarded as
being more recent than the other, but no proof of this is given. The
Coldbrook, Coastal, and Kingston groups were placed in the Huronian.
No instance was observed of the Coldbrook resting upon the Laurentian ;
but as the Coastal lies upon the Coldbrook and the Laurentian, there
was thought to be no reasonable doubt as to the true succession. The
Coastal was also said to contain fragments of the Coldbrook in it. The~
Kingston was replaced in the Huronian, because beds containing Upper
Silurian fossils were found to abut against those rocks, instead of forming
a continuous series. The St. John group was placed in the Cambrian,
while in the Cambro-Silurian were included rocks which in 1871 were
described as Laurentian, etc.

In a paper read before the American Association for the Advance-
ment of Science, August, 1880, Prof. Bailey remarked : —

“ Beginning with the older formations, we have found no reason to depart
from the view first advanced by us, that, beneath the fossiliferous rocks of the
St. John or Acadian Group, there exist two, if not three distinct formations,
equivalent in part, at least, to the so-called Laurentian and Huronian forma-
tions in other parts of Canada. It has been objected that this reference has
been based upon the wholly valueless ground of lithological characteristics, and
that the strata in question, being destitute of fossils, may even be Silurian ;
but such objection entirely ignores the fact that, accompanying such differences
of lithological character, there is, at the same time, the most marked evidence
of unconformability. .A study of the Primordial rocks east of St. John, in

NEW BRUNSWICK. 869

1879, placed this point beyond question, they having been then found by me to
occupy irregular troughs in the older Pre-Silurian rocks, resting sometimes
upon one and sometimes upon another of the subdivisions of the latter, crossing
their strike obliquely, and having at their base coarse conglomerates made up
of the waste of the underlying formations. The latter being thus unquestion-
ably of Pre-Silurian age, it is equally obvious that in their vast thickness, in
the markedly different conditions under which their several divisions were
accumulated, and finally in the further unconformability indicated between
these divisions, they represent a vast interval of time, and are at least as old as
the Huronian and portions of the Laurentian system, which in all their physi-
cal characters they so nearly resemble. No more marked coérdination of dis-
tant formations could be desired than is here furnished between the great mass
of coarse gneisses at the base of the series, associated with finer gneisses, quart-
zites, graphitic and serpentinous limestones and dolomites (the probable equiv-
alents of the Hastings’ series of Mr. Vennor), and capped by the great volcanic
series of the Huronian, with its petrosilicious and felsitic strata, ash-rocks and
agglomerates, the whole unconformably traversed by bands of the lowest Cam-
bro-Silurian, and the similar succession observed about Lake Huron and else-
where. . . . . It should be added in this connection that in the rocks here
assigned to the Huronian, there are as a whole two well-marked divisions, the
lower (or Coldbrook group) consisting almost entirely of fine grained felsitic
strata, with diorites, amygdaloids and porphyries, and the upper (or Coastal
group) of schistose rocks, often talcoid or nacreous, with conglomerates and
limestones and holding ores of copper, and that between the two there is not
unfrequently evidence of at least a partial unconformability, but in general
the relations to each other are much more intimate than are their relations
either to the underlying Laurentian, or to the Primordial strata which overlie
them.” (J. c., pp. 416, 417.)

In this paper the Kingston was separated by Prof. Bailey into two
groups : one of these was placed in the Huronian, and the other in the
Lower Silurian. This author further states, that the Upper Silurian

“age can now be definitely assigned to the very remarkable group of rocks sur-
rounding Passamaquoddy Bay, and which include the peculiar orthophyres or
felspar-porphyries of Eastport and Pembroke, Me., these latter having been
found to rest directly and almost horizontally upon a series of fossiliferous
sandstones, identical with those which at the last-named locality have been
long known to contain a rich Upper Silurian fauna. Another instance of the
difficulty of distinguishing the rocks of this most variable formation is to be
found in the occurrence, first observed by Mr. Matthew, of corals and other
Silurian organic remains on the Long Reach of the St. John River, in amygda-
loidal ash-rocks, which are undistinguishable lithologically from those of the
Huronian formation, and which, like those of Passamaquoddy Bay, had pre-
viously been referred to this horizon.” (Ul. ¢., p. 421.)
VOL. V1I.— No. 11. 24

370 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

The relation of the rocks as given by the preceding writers has been
given so far as we are able to make it out in the table appended.

In 1878 Dr. T. Sterry Hunt remarked : -——

“Tn a paper on the Geology of St. John County, New Brunswick, published
in the Canadian Naturalist in 1863, and reprinted in part in the geological
report of Canada for 1870-71, page 23, Mr. George F. Matthew described, under
the name of the Coldbrook group, a great mass of crystalline strata found in
southern New Brunswick, to the east of the river St. John. These rocks
repose on the Laurentian, and underlie unconformtably the uncrystalline Lower
Cambrian slates of the city of St. John, which include, near their base, con-
glomerates holding fragments of the Coldbrook group. From this, and from
their lithological characters, these older rocks were, by Matthew, referred soon
after to the Huronian series. (Quar. Jour. Geol. Soc., Nov., 1865.) They
have since been found to rest unconformably upon the Laurentian, pebbles of
which are contained in the conglomerates of the Coldbrook group. In the
paper which contained his account of the Coldbrook group, in 1863, Mr. Mat-
thew described a second belt of crystalline rocks similar to these, to which he
gave the name of the Bloomsbury group. These, apparently resting upon the
Menevian, and conformably overlaid by the fossiliferous Devonian sandstones
of St. John, were, at that time, called by him altered Devonian strata. In
1869 and 1870, however, the writer devoted some weeks, in connection with
Prof. L. W. Bailey and Mr. Matthew, to the investigation of the geology of
southern New Brunswick, when it appeared that the Bloomsbury rocks were
but a repetition of the Coldbrook group on the opposite side of a closely folded
synclinal holding Lower Cambrian sediments. Accordingly, in the geological
report of the gentleman just named, both of these belts were designated as
Huronian ; in which were now also included two other subdivisions of crys-
talline rocks found in that region, and previously designated the Coastal and
Kingston groups. (Report of Geol. Sur., 1870-71, pages 27, 60, 64.) These
Huronian rocks were traced in 1869 and 1870 along the southern coast of New
Brunswick, from the head of the Bay of Fundy to the confines of Maine, as
was stated by the writer in July, 1870, when these rocks ‘ called Cambrian
and Huronian by Mr. Matthew, and characterized by the occurrence of diorites
and quartziferous feldspar-porphyries, were said to occur in Eastport, Maine,
and in Newbury, Salem, Lynn and Marblehead, Massachusetts. (Amer. Jour.
Science, II. 1, 89.)” (Azoic Rocks, 1878, pp. 188, 189.) ;

It would seem that Dr. Hunt’s memory must have been at fault,
since the views of Messrs. Matthew and Bailey are indiscriminately
mingled with his own, while the sequence of time at which these views
were presented is generally disregarded. We cannot find, in either of
the papers of Mr. Matthew to which Dr. Hunt refers, any evidence that
the St. John rocks unconformably overlie the Coldbrook rocks, or that
the former contain pebbles derived from the latter. Mr. Matthew ex-

-

NEW BRUNSWICK. 3871

pressly states that there is no proof of unconformability,* and also that
the deposits of the St. John group

“present a marked contrast with those of the formation on which they rest
[Coldbrook Group]. Coarse fragmental beds and volcanic products are com-
mon in the latter ; but among the former no conglomerate or even a grit has
been detected, or any evidence of synchronic igneous action.” (Quar. Jour.
Geol. Soc., 1865, XXI. p. 427.)

It is also stated in the Observations on the Geology of Southern New
Brunswick (1865, p. 46), that
“ between the rocks above alluded to as constituting the upper member of the
Coldbrook Group, and the deposits which underlie the City of Saint John, the
contrast is very marked. While in the former, beds of coarse materials are
almost universal, the Saint John Group is, without exception, a collection of
the finer sediments. Throughout the limits of its distribution, not one con- -
glomerate or even a grit has been yet observed ; while the sandstones which
occur interstratified with the slates, are usually of a fine and even texture.”

If there were no conglomerates, or even grits, known in 1865 in the
‘St. John group, and the two formations were conformable, how could
Mr. Matthew, in the same paper in which these facts are stated, have
referred the Coldbrook group to the Huronian, because it was uncon-
formably overlain by the St. John group, and held fragments of the
Coldbrook group in its conglomerates? The fact is, that Mr. Matthew,
at that time, assigned the Coldbrook group to the Huronian, on ac-
count of its lithological characters, and because it underlaid conform-
ably the St. John group. In fact Dr. Hunt himself was not aware
of any such unconformability of the rocks in question, since he thus
expressed himself in 1866, referring to the Lower Silurian :—

“The lowest member of the series as yet known, is a group of 3000 feet of
black shales and sandstones, which at St. Johns, New Brunswick, is found
resting conformably upon still older schistose rocks, as yet unstudied. This,
which has been provisionally called the St. Johns group, has yielded numerous
fossils, which have been examined by Mr. Hartt. and show the formation to
correspond with the third division (Etage C) of the primordial zone.” (Geol.
of Canada, 1866, pp. 235, 236.)

Lithological evidence, so far as we can find, is all that is offered in
support of the statement that the Bloomsbury group is ‘a repetition of
the Coldbrook group on the opposite side of a closely folded synclinal
holding Lower Cambrian sediments.” The synclinal, the repetition, the
faults and overturns, appear to be purely theoretical, and introduced to
obtain conformity with that which the lithological characters seemed to

* See Dawson’s Acadian Geology, edition of 1868, pp. 660, 662.

372 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

demand. Had not these rocks resembled the Huronian, no one would
have ever thought that they were not Devonian ; but here appeared to
be some discrepancy in the theory of Delesse and David Forbes, adopted
by Dr. Hunt, that certain rocks could have appeared only at one epoch
in the earth’s history, and to get over this difficulty an overturn of the
strata was claimed. ~ The “ quartziferous feldspar-porphyries” of East-
port, which Dr. Hunt has here placed under the Huronian, have since
been shown by Bailey to be at least as recent as the Upper Silurian,
since they rest nearly horizontally upon Upper Silurian fossiliferous sand-
stone. In fact, on comparing Dr. Hunt’s published views in 1870 with
his explanation of them since given, it becomes quite impossible to make
out what those views really were.

In 1870 the Coldbrook group, to which he assigned the felsites, was
' spoken of as Cambrian. (Am. Jour. Sci., 1870, (2) L. p. 89.) This paper
related principally to the Terranovan, since called Montalban, and later
separated into the Montalban and Taconian. The Terranovan at that time
was regarded by Dr. Hunt as being in part Potsdam, and its relations
to the felsites unknown. In 187], in his address before the American
Association (Proceedings, XX. p. 33), Dr. Hunt claimed that in the above-
quoted paper of 1870 he held that the Terranovan was more recent than
the Huronian. In 1872, in his “ History of the Names Cambrian and
Silurian in Geology,”’ he claims to have held, since 1870, that the Ter-
ranovan (Montalban) and Huronian were pre-Cambrian in age, and
refers to the same paper for proof of this. (Canadian Nat., 1872, (2)
VI. p. 435.) In his “ Azoic Rocks” (pp. 189-193) he claims to have
held since 1870, referring to the same paper, that the felsites of Passa-
maquoddy Bay were Huronian.

According then to the original paper, and to Dr. Hunt’s subsequent
explanation of it, he maintained in 1870, in the same paper, that

THE FELSITES WERE CAMBRIAN.

THE FELSITES WERE HURONIAN.

THe HuRONIAN WAS PRE-CAMBRIAN,

THE TERRANOVAN WAS POST-HURONIAN.

THE TERRANOVAN WAS PRE-CAMBRIAN.

Tue TERRANOVAN WAS IN PART (SEVERAL THOUSAND FEET) POTSDAM, —

THE GEOLOGICAL RELATIONS OF THE TERRANOVAN TO THE FELSITES
WERE UNKNOWN.

From this table of conflicting views the student of North American
geology can draw his own conclusions as to the value of the work done
on a basis of lithological classification and speculation.

NEW BRUNSWICK. 873

The statements previously given in Dr. Hunt’s “ Azoic Rocks,” in
regard to the geology of New Brunswick, were repeated in essentially
the same form in 1879 (Proc. Am. Assoc. Adv, Sci., XXVIII. pp. 285-287;
Am. Jour. Sci., 1880, (3) XIX. pp. 273-275), together with this remark
regarding the lower and upper divisions of the Coldbrook group : —

“Tn a joint report of Matthews and Bailey in 1865, these rocks were declared
to be overlaid unconformably by the slates in which Hartt had made known a
Lower Cambrian (Menevian) fauna, and were compared with the Huronian of
Canada.”

This again is in part incorrect ; for if Messrs. Bailey and Matthew de-
clared anything in 1865, it was that the St. John group was conformable
with the Coldbrook group, or nearly so, and they are so represented in
their sections.* Furthermore, in Matthew’s paper, published in 1865
(Quart. Jour. Geol. Soc., XXI. p. 425), the St. John group is said to con-
formably overlie the upper division of the Coldbrook group, and this
same statement is made in the Report of Progress of the Canada Geo-
logical Survey (1870-71, pp. 59, 136).

Dr. Hunt, in 1873, remarked concerning the work of himself aud
Messrs. Bailey and Matthew, that he regarded the ancient crystalline
rocks in Southern New Brunswick

“as for the most part the equivalents of the Green Mountain and White Moun-
tain series, or what he calls Huronian and Montalban. These are penetrated
by granites, and associated in one part with Norian rocks, but the presence of
Laurentian in the region is somewhat doubtful.” (Proc. Am. Assoc. Adv. Sci.,
1873, XXII., B., pp. 116, 117.)

In 1875 it appears that Dr. Hunt held that the limestones in the
vicinity of St. John were of Montalban age. (Proc. Bost. Soc. Nat. Hist.,
1875, XVII. p. 509.) In 1878 these limestone rocks (the Portland series
of Matthew) are referred to the Taconian, and the gneiss (Laurentian)
to the Montalban, by the same writer. (Proc. Bost. Soc. Nat. Hist.,
1878, XIX. p. 278 ; Preface to the Second Edition of the Chemical Geo-
logical Essays, p. xxii. ; Azoic Rocks, p. 181.)

From the above it seems that Dr. Hunt would not admit as proved
the presence of any Laurentian, but would take the limestones belonging
according to Matthew to that formation and place them above the Cold-
brook group as Montalban and Taconian. Dr. Hunt’s statements seem
to have no substantial basis of facts ; they are mere lithological specula-
tions. Instead of trying to ascertain whether his theories are correct,

* Observations on the Geology of Southern New Brunswick, pp. 29, 31, 50.

314. THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

he assumes that they are so, and by faults, overturns, etc. endeavors to
make the stratigraphy coincide with his theoretical views. The fault
is always in the formation, never in the theory. According to Dr.
Hunt's own statements, he had, previous to his visit to New Brunswick
in 1869 and 1870, but little acquaintance with Huronian rocks. Since.
that, however, he has referred the felsites of Eastern Massachusetts,
Pennsylvania, Missouri, and elsewhere, to the Huronian, because they
lithologically resemble the rocks of New Brunswick, referred by him to
that age. He ought, therefore, if he really believes that rocks of the
same kind can only occur at the same epoch, to now refer all these fel-
sites to the Upper Silurian, Prof. Bailey having shown that to be their
true position, as stated on a previous page. We, however, believe that
they are rhyolitic lavas and ashes, and hence that they may occur at
any age and time. That they are of volcanic origin is admitted by Mr.
Selwyn also,

The reader should not fail to notice that, if credit is due any one for
the so-called establishment of the Huronian in New Brunswick, such
credit is to be given to Messrs. Matthew and Bailey, and not to Dr.
Hunt; also that the last-named gained his chief knowledge of the
Huronian rocks from the study of that formation as established by
Matthew and Bailey in New Brunswick, —that he was actually their
pupil, and not they his, as he would give us to understand.

The various opinions held at: different times by the geologists con-
nected with the Survey of New Brunswick with regard to the classifica-
tion and nomenclature of the older formation will be found presented
in the tabular view (Table A.) given herewith.

NOVA SCOTIA.

Prof. Henry Y. Hind in 1870 described two series of gneissoid rocks
which he regarded as probably Huronian (Cambrian) and Laurentian.
(Quart. Jour. Geol. Soc., XXVI. pp. 468-479.) He gives the following
as his reasons for this supposition : —

“Ist. The unconformable contact of the Lower Silurian gold-bearing strata
with the underlying gneissoid and schistose series.

“2nd. The unconformable contact of this gneissoid and schistose series with
the old porphyritic gneiss . . . . before described as Laurentian.

é
al
j
,
ms
J
Dy
e.'
A er Fi
- ee
: :
, jm *

o1( Ve

aT
rs

wl
yay?

7

J. W. Dawson.

TABLE

AS ARRANGED BY MESSRS. DAWSON,

OF THE PRE-CARBONIFEROU

Geor@E F. MATTHEW,

GeoRGE F. MaTTHeEw,

Portland.’

1863. 1865.
1855.| Sil Y Portland Series.1 |
Bs) ilurian. ortland Series. a
| 3 | Laurentian.* Portland.
| 5 |Coldbrook Group.?
: 2 ——
1861 | Devonian. . Se yon Greine
ne . Lower
| : Huronian. Coldbrook i
| Dominant =) Bloomsbury Group { Upper.®
ay <i
1862. | Silurian. (2) g eres
| Silurian. (? =
x § |Little River Group 4 pas eee
5 Shales. Lower Silurian. St. John.¢
| % \Mispeck Group
iF
= |
= Upper Silurian.
Bloomsbury.
Devonian. Little River. $7
Mispeck.

1 Containing fragments of plants in the upper beds.
2 Certainly regarded as Devonian.

8 No proof observed that this group is unconformable either with the over- or under-lying rocks.

4 Certain rocks afterward separated from this group under the name of Coastal were placed in the above
group as Upper Devonian, because they overlie the Dadoxylon Sandstone conformubly (or nearly so), and
underlie the Carboniferous unconformably, while they partake of the flexures of the Devonian series.

5 Conformably overlain by the St. John group, but on lithological grounds Huronian.
6 No unconformability between this group and the Huronian.

7 These three groups rest unconformably on the Laurentian, Huronian, and Silurian, and were regarded as

Middle and Upper Devonian.

8 Assigned to the Laurentian on lithological grounds.

unquestionably Upper Devonian groups.
9 Probably Huronian, both under- and over-lying the St. John group.
10 Made Upper Silurian (?) on lithological and stratigraphical grounds.

11 Entirely conformable with the Little River and Mispeck groups; not entirely so with the St. John.

* The names in this column are to be considered as applying to all beyond, except the last two columns.

Almost entirely conformable to the overlying

Coldbrook.®

St. John.

Kingston.!°
Mica Schist Group.

Bloomsbury,1! 3
Dadoxylo:
lave : Sandston
Little River Cordaite

F Shales.
Mispeck.

FORMATIONS

(LEY, MATTHEW, AND ELLS, 1855-1880.

OF NEW BRUNSWICK,

ULEY AND MATTHEW, | MarriuEw, BalLEY AND MATTHEW, BalLey, Baitey, Matruew, anv ELLs,
1870-1871. 1876-1877. 1877-1878. | 1880. 1878-1879.
|
——— = | — = ==
|
rtland. feo Portland. Portland. epee } Portland. oe re
= a =
wer Coldbrook.'$ Lower Coldbrook. ee |
yomsbury.!4 Coldbrook. Upper Coldbrook. goldbro ek: pole ok.” H ;
agston. 16 Bloomsbury. Bloomsbury. Sastre Mele | SEULOXUAT.
usta] .16 Coastal: Kingston.*° [Kingston.%
2 pee | =
per Coldbrook. St. John. St. John St. John. St. John. |Cambrian.
Jobn. Lower Kingston. '* ; ¥ Kingston.2° [Kingston.?5 Cambro-Silurian.
|Felsites of
Upper Kingston. Kingston.18 Eastport and Silurian.
? Pembroke.?!
loxylon Sandstone. Dadoxylon Sandstone.
‘daite Shales 'Cordaite Shales. Devonian.

speck Conglomerate.

Mispeck Conglomerate.

12 The entire Devonian series here given was laid down quietly, one group on another, with no marked

unconformability or disturbance.

18 Overlying conformably in places the St. John group, and underlying conformably the Devonian.
14 United with Coldbrook on lithological grounds.

18 Contains intercalated Upper Silurian strata, but Coastal overlies them.
18 Overlying Upper Silurian and Lower Devonian strata, but from its lithological characters is placed in the

Huronian.

17 Contains pebbles derived from the St. John group.
18 Placed here on account of paleontological evidence, although lithologically identical with the Huronian,
and apparently dipping beneath that formation.

20 In part.

*1 Lithologically undistinguishable from the Huronian, and formerly regarded as belonging to that age.
22 No instance of the superposition of this on the Laurentian observed.

23 In part.

[These notes represent in a brief form the statements of the geologists above quoted regarding these for-
mations, as given in their publications and in the text preceding.]

NOVA SCOTIA. 375

“3rd. The unconformable contact of the gold-bearing series with the Lau-
rentian gneiss, showing the absence of the intermediate gneissoid series, or the
Huronian.” (Jl. c., p 474.)

See also Am. Jour. Sci., 1870, (2) XLIX. pp. 347-355 ; L. pp. 132-
134, 417-422.

In order that the conclusions of Prof. Hind may properly be regarded
as proved, it is necessary that the age of the gold-bearing strata sup-
posed to be Lower Silurian or Cambrian should be. ascertained, and also
that the origin of the rocks in question, and their actual, not supposed, re-
lations to one another be clearly made out, he having apparently deter-
mined the order of superposition by the dip of the foliation. Mr. Hind
expressly states that his supposed Silurian strata are more altered —
bearing andalusite crystals —near the so-called Huronian rocks than
at a distance from them. Dr. Dawson regards the so-called gneiss of
Prof. Hind as granite, and states that it is intrusive in the gold-bearing
strata and Oriskany rocks. Certainly more credit should be given to
Dr. Dawson’s assertion than to Prof. Hind’s negative evidence. (Supple-
ment to Acadian Geology, 1878, pp. 84, 85.)

Mr. Selwyn states regarding this granitic region : —

“T have examined it in all the above-named districts, and the impression I
at present have, is that it is strictly of an indigenous character, and neither an
old granitoid gneissic series of Laurentian age, nor an intrusive mass. Dr.
Dawson has shown (Acadian Geology, 1868) that in different parts of its
course it comes successively into contact with Lower Silurian, Upper Silurian
and Devonian rocks, and the manner in which these sedimentary strata are
affected at the lines of contact scarcely leaves room to doubt the posterior ori-
gin of the granite ; but whether as an intrusive mass, or by the metamorphism
im sité of the stratified rocks, (in part by a process of molecular re-arrangement
of their original component particles,) is perhaps uncertain.” (Geol. of Can-
ada, Report of Progress, 1870-71, p. 265.)

Whatever the origin of the granite may have been, evidence of that
origin ought to be obtained from an investigation of the relation of that
rock to the adjacent ones. Dr. Dawson’s statements prove most clearly
the eruptive intrusive character of the granite in question, the evidence
consisting not only in the induration of the rocks with which the gran-
ite comes in contact, but also in its sending tongues and dikes into
them. Mr. Selwyn does not furnish any evidence to sustain his views,
which seem to be the natural result of an effort to solve problems with-
out a sufficient petrographical examination of the rocks concerned. As
we have before repeatedly remarked, such metamorphism iz sitw as is
here demanded needs to be proved, before it can be admitted.

376 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Dr. Hunt thinks that the supposed Huronian of Prof. Hind belongs
to the White Mountain series ; but this conclusion, like most of his geo-
logical work, is purely theoretical, based on lithological resemblances.
(Am. Jour. Sci., 1870, (2) L. p. 87.)

Dr. Honeyman’s papers on the Laurentian age of certain rocks of
Nova Scotia, in the Transactions of the Nova Scotia Institute of Natural
Science, the Quarterly Journal of the Geological Society, and the Amer-
ican Journal of Science, appear likewise to be valueless, as his conclu-
sions depend chiefly on lithological characters, aided by the distribution
of a supposed Hozoén. His conclusions are, furthermore, objected to by
Dr. Dawson, who states that there is neither stratigraphical, lithologi-
cal, nor paleontological evidence to sustain them. The rocks in question
Dr. Dawson regards as probably Lower Silurian, Cambrian, or Huronian.
(Canadian Naturalist, 1879, (2) IX. pp. 1-16.)

According to Mr. Edward Hartley, the Coal Measures near New Camp-
belltown, Cape Breton, stand vertical, or nearly so, within one hundred
feet of syenite and “limestone highly altered serpentinous and crystal-
line.” The dip of the Coal Measures diminishes on receding from the
syenite, until they assume a nearly horizontal position (dip 5 or 10
degrees). Since the syenite and limestone resemble the Laurentian, Mr.
Selwyn writes: “From the foregoing facts it appears that the Coal
Measures in Cape Breton are in direct contact with rocks of Laurentian
Age.”

The present writers, however, think that nothing of the kind has been -
proved. It has been simply shown by Mr. Hartley that the Coal Meas-
ures are seen highly tilted within fifty or one hundred feet of limestones
and syenite of unknown age. (Geol. of Canada, Report of Progress,
1870-71, pp. 4, 5.)

Later, Mr. Charles Robb, in an examination of the same region,
states :—

“The existence of a fault or complication of faults here seems to be proved
beyond a doubt, and the occurrence of a band of calcareous and magnesian
rocks of varying thickness, between the Lower Carboniferous and Productive
Coal-measures on the one hand, and the syenite on the other, is also clearly
established.”

No eozoénal characters were found in the limestone on microscopic
examination. (Report of Progress, 1873-74, p. 174.)

Mr. Robb later gave a much fuller account of the district, with a map
of the same. He found a conglomerate containing pebbles of syenite in
the Lower Carboniferous rocks, and some of the strata appeared to have
been inverted. (Report of Progress, 1874-75, pp. 251-262.)

NOVA SCOTIA. 377

In commenting upon Mr. Robb’s work, Mr. Selwyn remarks : —

“ The examinations recently made by Mr. Robb at Kelly Cove on the Great
Bras D’Or Lake show that a similar series of crystalline rocks, — magnesian
limestones, serpentine, &c.,— occur there between the Carboniferous series
and the great mass of syenite, which has been supposed to be of Laurentian
age ; but which will, I think, more probably prove to be an intrusive mass
nearly corresponding in age with the great central granitic axis of Nova Scotia,
which is undoubtedly pre-Carboniferous and post-Devonian.” (J. ¢., p- 9-)

This is certainly a striking change in Mr. Selwyn’s opinion since
1871. The evidence, however, is strongly in favor of his later views.
Mr. Hugh Fletcher, from more extended labors in Cape Breton, ren-
dered it quite evident that in some localities the syenites and felsites
are older than some lower Silurian rocks, hence probably Azoic. He
relies on lamination solely to prove the sedimentary origin of the rocks
in question, and on almost every page shows by his work that he has
no knowledge of the characters of eruptive rocks, or of the methods of
proving in the field whether the rocks in question are or are not erup-
tive. His statements concerning their origin are therefore valueless.

The St. George limestone, which he thinks may possibly be Huro-
nian, — although he has classed it as Laurentian, —is said to contain
pebbles apparently derived from the syenites and felsites. (Reports of
Progress, 1875-76, pp. 371-388 ; 1876-77, pp. 405-428; 1877-78,
pp. 3-10, F.)

The age of the limestone was not determined any farther than that it
was shown to be older than the Carboniferous ; it was simply assumed
that it was Azoic. Concerning the Huronian in Nova Scotia, Principal
J. W. Dawson remarks :—

“There is no good evidence that the Cobequid series and its equivalents in
Pictou and elsewhere are older than the Lower Silurian. There seems, how-
ever, good reason to class as Huronian, or at least as Lower Cambrian, the
rocks of the Boisdale Hills in Cape Breton, which Mr. Fletcher finds to under-
lie the fossiliferous Cambrian of that region, and which are more quartzose
and micaceous than the rocks of the Cobequid series. It is not impossible
that rocks of this age may also occur in the vicinity of the Cambrian beds
found at Miré. We may also conjecturally class as Huronian the chloritic
rocks of Yarmouth.” (Supplement to Acadian Geology, 1878, p. 88.)

In the same work Dr. Dawson also states regarding the Lauren-
tian : —

“Dr. Honeyman and Prof. Hind have suggested the Laurentian age of
certain rocks as Arisaig, in the Cobequids, and associated with the coast Meta-

378 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

morphic series, but Ido not regard the evidence of this, either from fossils,
mineral character, or superposition, as conclusive, and must refer for it to the
memoirs of these gentlemen in the transactions of the Nova Scotia Institute,
and the Journal of the Geological Society of London. I must, in like manner,
decline to receive as of Laurentian age the felsitic and other rocks of Cape Bre-
ton, referred to this system by Mr. Fletcher in the latest Report of the Geo-
logical Survey. I would except those of St. Anne’s Mountain, the lithological
resemblance of which to the Lower Laurentian of Canada is indisputable, and
the evidence that they may be of this age has certainly been much strength-
ened by the recent observations of Mr. Fletcher. Specimens, and the observa-
tions of Mr. Brown and Mr. Campbell and others, induce me also to believe
that in the little island of St. Paul, and in some parts of Northern Cape Bre-
ton, we may have a continuation of the rocks referred by Mr. Murray to the
Laurentian in Newfoundland. With these exceptions, I have not seen in
Nova Scotia, unless in travelled boulders, any rock that I could believe to be
lithologically equivalent to the Laurentian of Canada, nor have I found any
stratigraphical evidence of the occurrence of such rocks.” (J. ¢., pp. 89, 90.)

The condition of the question in Nova Scotia can be briefly summed
up as follows. In one locality it is probable that some rocks— of, in
part at least, doubtful origin — are of Lower or Pre-Silurian age. There
is no evidence showing that they should be subdivided into any of the
supposed pre-Paleeozoic systems, other than lithological, and the finding
of some pebbles in a limestone, supposed (not proved) to be the same as
the rocks it was desired to place in an inferior position. In fact, beyond
the evidence of the pebbles, no proof has been furnished that would
justify us in placing any of the rocks of Nova Scotia below the recog-
nized fossiliferous portions.

NEWFOUNDLAND.

The first report of the Geological Survey of Newfoundland made
under the general direction of the head of the Canada Survey, Sir
William Logan, bears date April 11, 1865. Previous to this, however,
Prof. J. B. Jukes made a geological reconnaissance of the island, under
governmental authority. This was during the years 1839 and 1840.
As Professor Jukes made no attempt to assign names, other than local,
to the formation below the Carboniferous, it will not be necessary to
take his work into consideration in the present connection.

eked

NEWFOUNDLAND. 379

Mr. A. Murray, in his report to Logan of what was done during the

year 1864, recognizes the Laurentian Series as occurring on the north-

ern peninsula of Newfoundland. He gives the following table of the
sequence and distribution of the rocks of that region. (J. ¢., p. 8.)
I. Laurentian Series,

II. Lower Silurian Series.

III. Upper Silurian Series,
IV. Devonian Series.

Potsdam Group.
Quebee Group.

After describing the rocks assigned to the Laurentian, which were
found to be exclusively of a gneissic character, he adds as follows :—

‘¢ The rocks which have thus been described are considered Laurentian, not
merely from the lithological resemblance which they bear to the strata of that
series in various parts of Canada, but also from the relation they are seen to
have to the Lower Silurian series, which unconformably covers them up in the
northern part of the peninsula... .. In Canada the Laurentian gneiss is in
some parts interstratified with enormous bands of crystalline limestone. .. . .
None of these bands have been met with among the gneiss of the northern
peninsula.” (J. c., pp. 10, 11.)

In the Report upon the Geological Survey of Newfoundland for the
year 1868, Mr. Murray introduces into the series of formations of that
island an “ Intermediate System,” which he supposes to be the “ equiv-
alent of the Cambrian of England, and the Huronian of Canada.” This
series he divides into seven distinct groups, admitting, however, that
“there are many repetitions of the same strata,” and that “a large por-
tion of the country is concealed by superficial deposits of gravel and
boulders.” The total thickness of the strata thus divided is given at
11,370 feet, the rocks being, with the exception of the upper portion,
chiefly slates, and the reason for this manifold division of the series not
being apparent in the description of the same. About the middle of
the series, in group ¢, “ fossil forms, supposed to be of the genus O/d-
hamia,” were obtained. In group d, also, “some obscure organic
remains, resembling the fossils found inc,” were found. The order of
superposition of these rocks was determined by observations made along
a section from St. John’s to the northern side of Great Bell Isle in
Conception Bay. Ina note added to the English reprint of the series
of Newfoundland geological reports (published by Stanford, in London,
in 1881), it is said that the fossil forms “supposed to resemble the
Oldhamii of Bray Head” were pronounced, on examination by Mr.
Billings, the late paleontologist of the Survey, to be undeterminable.
“ He doubted their organic origin altogether.” (J. c., p. 144.)

380 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

In the Report of the Geological Survey [of Newfoundland] for the
year 1872, Mr. Murray notes the discovery of fossil forms in the Huro-
nian rocks of St. John’s, which, according to him, ‘‘ appear to mark out a
particular zone or horizon of the formation, which is limited to the sub-
division (d) of No. 2 Section” of the Report for 1868. These fossils are
the Aspidella (misprinted Aspidilla throughout the report for 1872)
Terranovica and the Arenicolites spiralis, described by Billings in the
“ Paleozoic Fossils” of the Canada Geological Survey, Vol. II. Part I.
pp. 76, 77. The presence of the Aspidella was considered by Mr. Mur-
ray as being of “ marked value as an indicator of the horizon, no form .
bearing any resemblance to that fossil having ever been recognized in
the rocks of the upper series. Nor are they known to exist in any of
the strata, by which the slates (¢d) are underlaid.” (7. ¢., p. 17.)

In the Report of Progress [of the Geological Survey of Newfoundland]
for the year 1873, the presence of “ labradorite and other anorthosites”
in the gneissic rocks of certain localities is said to “give rise to the
supposition that they belong to the upper or newer Laurentian Series,”
while angular boulders and fragments of white crystalline limestone are
considered to be “suggestive of the proximity of the upper members of
the lower series.” This is the first intimation that the Laurentian is to
be divided into two or more groups, and seems to be merely an endeavor
to correlate the older formations of Newfoundland with those of Canada,
on a purely mineralogical basis, and on extremely imperfect evidence.

That certain stratified rocks are unconformable with a lower granitic
and gneissic formation, called Laurentian, is evident from the facts
stated in the Newfoundland reports. That these strata belong to the
Primordial or Potsdam division of the Lower Silurian is also made ap-
parent by the character of the fossils which they contain. That these
Primordial rocks may be developed to.a very great thickness is also ren-
dered probable; although it is‘ not unlikely that a more thorough study
of the region would considerably reduce that amount, the region being
one difficult of exploration, much disturbed, and largely covered by
superficial detritus.

In the Report of Progress [of the Geological Survey of Newfoundland]
for the year 1881, the discovery of the Aspidella and the Arenicolites is
again alluded to, as offering “ great facilities for the ready recognition of
the Huronian when tracing out the structure which, otherwise, would
be extremely difficult.” The value of the evidence based on the pres-
ence of these supposed fossils, as establishing a new system between the
Primordial and the Laurentian, will be discussed farther on. At pres-

LABRADOR. 3881

ent it need only be remarked that the published sections do not furnish
the desired proof of the unconformability of the “ Intermediate Series ”
with the overlying Primordial.

LABRADOR.

In 1863 the gneissoid rocks of Labrador were assigned by the Cana-
dian survey to the Laurentian. In 1865, Prof. A. 8. Packard, Jr. gave
some account of the geology of the coast of Labrador. It seems at the
beginning he mistook for syenite some diabasic rocks, and thought, from
finding some pebbles enclosed, that it was formed from a conglomerate.
He evidently was not aware that eruptive rocks frequently enclose peb-
bles that they have picked up. Indeed, it is probable that under the
name Syenite Prof. Packard has united very diverse rocks. He assigns
some quartzites doubtfully to the Huronian, saying: ‘“ Nowhere was I
able to see the juncture of this rock with the Laurentian gneiss. ... .
At no point was I enabled to observe whether these quartzites rest un-
conformably upon the older Laurentian gneiss, though inclined to think
Shot The Canadian Geologists likewise state that the strata of
the Huronian system have not been observed resting directly on tilted
Laurentian rocks; it is as yet a matter of hypothesis.” Prof. Packard
evidently assumed that the foliation of the gneiss or granite was
synonymous with stratification.

He pointed out the presence of the labradorite rocks forming the
‘Upper Laurentian of Logan and the Norian of Hunt, but he (Packard)
does not seem to have observed its. relations to the other rocks. He
however found part of it in overflows which he supposed resulted from
a refusion of the labradorite rock. His observations point rather to an
eruptive than to a sedimentary origin for this “norite.” (Memoirs of
the Bost. Soc. Nat. Hist., 1868, I. 213-218.

Prof. Packard’s Huronian Dr. Hunt regards as Laurentian, but accepts
the labradorite rock as Norian. (Amer. Jour. Sci., 1870, (2) XLIX.
p. 182.)

Prof. H. Y. Hind later described the Geology of Northeastern Labra-
dor ; but, as before, the rocks were referred to the Laurentian on litho-
logical grounds. No evidence was given to show the relations of the
so-called Upper Laurentian to the Lower Laurentian, but all rested on

382 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

theoretical grounds. (Canadian Nat., 1878, (2) VIII. pp. 227-240,
262-278.)

In 1876 Mr. D. F. H. Wilkins illustrated in a paper upon Labrador
some of the methods employed in the study of crystalline rocks. The
supposed formations were determined by lithological characters, the folia-
tion taken as the lines of stratification, and an apparent dike regarded a
representative of the Norian. He says: “The stratification lines are
very often so obscure that it is almost impossible to say whether the
rocks are metamorphic or eruptive” ; and of the Norian at one locality,
that it consists of “red-weathering, gray hyperite in a bed two feet thick,
overlaid by. four feet of whitish gneiss . . . ., seen to repose, at low tide,
upon the underlying red gneiss of Lower Laurentian age.” (Canadian
Nat., 1878, (2) VIII. pp. 87, 88.)

Thus far we have found no evidence except lithological in support of
the ages to which the crystalline rocks of Labrador were assigned.

MAINE.

The geological survey of Maine, under Prof. Chas. H. Hitchcock, de-
veloped nothing of value as determining the question whether the Azoic
system existed in that State. No evidence bearing on this question
other than lithological was furnished.

Dr. Hunt in his Geognosy of the Appalachians infers from lithologi-
cal characters and difference in dip that the “ mica schists and gneisses ”
are of Montalban age, while the “ greenish chloritic and chromiferous
“schists” in the vicinity of Portland are Huronian and older than the
gneisses. (Presidential Address, 1871, p. 10.)

Prof. Chas. H. Hitchcock objected to the views of Dr. Hunt, holding
that, while the rocks in question were Montalban and Huronian, the
Montalban was the older, and the Huronian at this point was deposited
upon it. He states that “at the line of junction as observed in Deer-
ing, the two groups of rocks possess exactly the same inclination,” and
declares that, if in their natural position, the gneiss underlies the schist.
He acknowledges that the only way these formations have been identi-
fied is by lithological characters, remarking that

“ Logan, in 1855, described a system of rocks overlying unconformably the
Laurentian gneisses about Lake Huron, which were distinguished by means of

MAINE. — NEW HAMPSHIRE. 383

lithological characters. All geologists, therefore, who use the name Huro-
nian, of necessity practically adopt this principle, though perhaps insensibly.
We do not claim that a talcose rock can never be found in any other system
than the Huronian, nor that gneiss may never be interstratified with the hydro-
micas. Professor Dana’s recent paper shows that gneisses, quartzites and lime-
stones are interstratified in the Lower Silurian of western New England.....
In no instance would we claim that mineral character is sufficient to distin-
guish systems without a study of the relations of the strata. We may some-
times generalize, and believe that rocks of similar mineral character must be of
the same age, but such speculations always provide for confirmation by a study
of the strata.” (Proc. Am. Assoc. Adv. Sc., 1873, XXII. pp. 166, 167.)

We shall see that in New Hampshire Prof. Hitchcock relied en-
tirely on lithological evidence, evidently not following the views here
advocated.

In his paper on Granites and Granitic Vein-stones Dr. Hunt referred
many of the granites (gneisses) and mica schists of Maine to the Terra-
novan or White Mountain series, but on lithological grounds. (Am.
Jour. Sci. 1871, (3) I. p. 182.)

In two more recent papers by Messrs. Hitchcock and Huntington
certain rocks in Northern Maine are regarded as Laurentian and Huro-
nian, if not Montalban; but this decision rests solely on lithological
evidence, not the slightest proof being given that the rocks in question
may not be much more recent than the Azoic, and of the same instead
of different ages. (Proc. Am. Assoc. Ady. Sci., 1873, XXII. pp. 205-
214; 1877, XXVI. pp. 277-286.)

Thus far no evidence has been given that proves the pre-Silurian age
of any rocks in this State, all the evidence thus far advanced being
based exclusively on lithological characters.

NEW HAMPSHIRE.

In this State we have principally to do with the writings of Messrs.
Hunt, Huntington, and Hitchcock, these being the geologists who have
especially interested themselves in establishing subdivisions in the sup-
posed Azoic rocks of that State. It is in the publications of Prof.
C. H. Hitchcock, State Geologist of New Hampshire from 1869, how-
ever, that we find the larger part of that which touches the questions
here before us.

384. THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

In stating the results obtained by the Canada Geological Survey, as
detailed in the Report of Progress for 1847-48, Dr. T. Sterry Hunt re-
marked that to the “Chemung and Portage group of New York, with
the old red sandstones, .... may perhaps be referred in part the
rocks of the White Mountains.” (Am. Jour. Sci., 1850, (2) IX. p. 19;
Proc. Am. Assoc. Adv. Sci., 1849, IL. pp. 333, 334.)

In 1863 he wrote : —

“Tt is moreover probable that the rocks of New Hampshire, including the
White Mountains, are altered strata of Devonian age.” (Geol. of Canada, 1863,
p- 598.)

In 1867 the White Mountains were again referred to the Devonian
by Dr. Hunt. (Esquisse Géologique du Canada, p. 23; Bull. Soc. Géol.
France, 1867, (2) XXIV. p. 687.

Prof. J. P. Lesley, in 1860, stated that he had a

‘‘ orowing conviction that the range of the White Mountains would prove to he
synclinal instead of anticlinal, and therefore of probably Devonian age. ... .
Ascending Mount Osceola . . . . the bridle path mounts over successive out-
crop ledges of perfectly horizontal plates of granite, as evidently and regularly
bedded as any of the sandstone masses of the Alleghanies, the bed planes not
being at all disguised by the cleavage planes. Between these plates of granite
lie plates of unchanged dark blue sandstone ; a rock which at the cascades

. has been mistaken for greenstone trap.” (Proc. Acad. Nat. Sci. Phil.,
1860, XII. pp. 363, 364. Mining Magazine, 1861, (2) II. pp. 99-101.)

The probable truth in this is, that Prof. Lesley mistook some old
basaltic dikes for sandstone, and the concentric lamination of the gran-
ite for stratification.

Dr. Hunt, in 1878, stated that Logan suggested that the rocks of
the White Mountains were “probably altered Devonian strata” (Azoic
Rocks, pp. 86, 87, 182); while, in 1861, he said :—

“The White Mountains as we suggested in 1849 (this Journal, [2], IX, 19),
are probably, in part at least, of Devonian age, and are the representatives of
7000 feet of Devonian sandstone observed by Sir William Logan in Gaspé.
Mr. J. P. Lesley has more recently, after an examination of the White Moun-
tains, shown that they possess a synclinal structure, and has adduced many
reasons for regarding them as of Devonian age.” (Am. Jour. Sci., 1861, (2)
XXXI. p. 403.)

In 1870 it would appear that, under the name Terranovan, they
were regarded by him in part at least as Potsdam. (Am. Jour. Sci.,
1870, (2) L. pp. 83-90.)

NEW HAMPSHIRE. 385

In the First Annual Report of the New Hampshire Geological Sur-
vey, 1869, Prof. C. H. Hitchcock divided the rocks then examined as

follows :—
“ Gneissic, Granitic or White Mountain Series.
Staurolite Schists
Lower (mostly green) Schists

Copper Belt Quebec Group.
Clay Slate
Auriferous Conglomerate
Upper Schists.”
Prof. Hitchcock in that Report states that
“there are two general divisions . . . ., first the granitic and gneissic rocks

which appear to be older and consequently to underlie the formations of the
second or Quebec group — the true auriferous strata. The name Quebec is
that applied by Sir W. E. Logan, of Canada, to rocks . . . . shown to consti-
tute a new group, not present in the New York series, but lying between the
Calciferous Sandrock and the Chazy Limestone.” (J. ¢., p. 17.)

.No evidence is given to show that the rocks belong to the Quebec
group, and that the granite is not eruptive, nor are its relations to the
supposed Quebec group stated. All is based upon theoretical grounds.

In the Second Annual Report, 1870, the rocks of New Hampshire are
arranged as follows : —

‘61. White Mountain or Gneissic series, subdivided into
. Normal Gneiss.

. Ferruginous Gneiss.
. Granitic Gneiss.

. Feldspathic Mica Schist.
. Andalusite Gneiss.

. Chiastolite Slates.
Granite.

. Syenite.

. Porphyritic Granite.
. Quartzites.

. Limestones.

12. Soapstones.

SOMDTIAAA wD

a
_—

*¢ Little doubt remains as to the Eozoic or pre-Silurian age of this entire
series.”

“2. Sienite of Exeter and Dover.

‘* There appear to be sienitic rocks of probable Laurentian age, equivalent
to the Quincy sienitic group of Massachusetts, . . . . in the towns of Exeter
and Dover. They form, apparently, an anticlinal mass, overlaid by the Mer-
rimack slates.”

VOL. vir.— No. 11. 25

386 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

‘3. Porphyritic Granite.

‘*Common granite full of large crystals of feldspar. . . . . Some portions
of it have evidently been injected, while the arrangement of the feldspathic
erystals in parallel lines leads to the suspicion of stratification in other cases.”

‘4, Common Granite.

“The granite of New Hampshire seems to have originated at five different
periods. First are the (a) indigenous and (6) eruptive granites of the White
Mountain series ; second, the (c) indigenous granites of the Merrimack group,
in which none of the eruptive class have yet been seen; third, the (d) indige-
nous and (¢) eruptive granites of the Coés and calciferous mica schist groups.”

‘© 5, Merrimack Group.

‘They probably belong to the earliest Silurian series.”
** 6. Quebec Group.

“ Lower Silurian, according to Sir William E. Logan.”

‘¢'7. Cods Croup of slates, schists, quartzites, etc.
** It appears clearly to overlie the White Mountain veins unconformably.”

“8. Calcrferous Mica Schist.

“9. Clay Slates.
“8 and 9 seem to be limited outliers in New Hampshire.” (I. c., pp. 31-34.)

In the Third Report, for the year 1870, it is stated that

‘the White Mountain rocks are believed to belong to two great systems, the
Gneissic and the Coos Group. The first are, for convenience, called the White
Mountain series... .. These rocks appear to underlie the Coos group, and .
are therefore older. The presumption is that they are entirely Eozoic, though
it is not clear whether they are to be considered as the equivalent of the Lau-
rentian of Canada, or more nearly the age of the Cambrian of Great Britain as
restricted by the Government Survey. .... Its satisfactory reference to the
Eozoic series will enable us to clear up the obscurities of New Hampshire
geology.”

The Cods group was placed as before above the White Mountain
series, and, “judging from fossils in Nova Scotia, this group is not far
from the St. Johns slates in age.” (J. ¢., pp. 9-11.)

In the next Report, —that for the year 1871, some changes were
made in the general arrangement of the rocks, which were classed as
follows :—

«1. Porphyritic Gneiss.

‘¢ We suppose this to be the oldest formation among the mountains. Geolo-
gists speak of a rock of this character as common in the laurentian in various
parts of North America and Europe.”

NEW HAMPSHIRE. 387

‘© 2. Bethlehem Gneiss.

“It is usually granitic, so much so that it has always been called granite
heretofore. .... Lying between outcrops of porphyritic gneiss the natural
inference is that it is a synclical, and therefore newer, while the strike indi-
cates a very great antiquity judging from the same phenomenon elsewhere.
.... If the anticlinal structure is persistent, evidence may be afforded that
this peculiar gneiss is older than No. 1.”

‘¢ 3. Gneiss.

‘¢4. White Mountain or Andalusite Gneiss.

‘¢ Tt seems to be newer than Nos. 1 and 2, but the relations to the granites
and norian are yet to be made out.

‘¢5. Common Granite.
“The joints passing through this rock are both horizontal and vertical.
.... East of Saco the Andalusite gneiss seems to have been cut by it.”

‘* 6, Trachytic Granite.
‘¢ Above No. 5, with the same horizontal appearance.”

‘¢'7, Brecciated Granite.

‘‘The rock is irregular in arrangement as if thrust up from below. As it
contains no fragment of the common and trachytic granite, we have concluded
it to be more ancient than either of these granites, but newer than the porphy-
ritic gneiss. The two areas are also probably connected beneath the Pemige-
wasset valley under the common coarse granite, which either flowed in above
the breccia or was deposited upon it quietly in some other way.”

“8, Norian.
‘“‘ This includes several areas of labradorite rock, including compact felsites,
breccias and syenites.”

“9. Clay, Slate and Quartzites.
“10. Coos Group.”

Concerning the age of the Norian and some others of the preceeding
divisions, Prof. Hitchcock remarks : —

“ All will agree that the mineral labradorite belongs to the original lauren-
tian system, and therefore by its discovery in New Hampshire will be satisfied
that some of our crystalline rocks belong to the older series of the Eozoic, and
not the Paleozoic. Hence the prevalent opinion respecting the age of the New
England metamorphic rocks must be changed to conform with the discovery of
labradorite in our state. . . . . Our conclusions as to the absolute and relative
ages of the New Hampshire formations depend upon the reference of some of
them to the Norian system of Hunt.” (J. ¢., pp. 4-10.)

Dr. Geo. W. Hawes regarded the Norite rock as eruptive, saying : —

“ At some points the rock possesses all the structure of an eruptive mass,
and when in other places this is not found, the evidence furnished by more

388 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

favorable localities, as well as that furnished by allied rocks in other lands
where they have been more thoroughly investigated, must at present be deci-
sive.” (Geol. of New Hampshire, III., Part IV. p. 165.)

This rock was accepted by Dr. T. Sterry Hunt as Norian in 1873
(Proc. Bost. Soc. Nat. Hist., 1873, XV. p. 310), but in 1878 he re-
marked :—

‘‘ The labradoritic rocks in the White Mountains, which had by Hitchcock
been referred to norite, are now found by him to be eruptive masses.” (Azoic
Rocks, p. 161.)

In a paper by Prof. Hitchcock (Am. Jour. Sci., 1872, (3) III. pp. 43-
47), on the “ Norian Rocks in New Hampshire,” the following is ad-
vanced to show their sedimentary origin : —

“ The first rock seen is a gneiss with nodular orthoclase, dipping by compass
about 80°, S.70° W. The strata are indicated by folia of a dark hypersthenic
mineral, often forming bunches or nodules. Jointed planes dipping about 25°
westerly might be mistaken for strata.* One might be so easily deceived, that
it seems as if they must be the planes described at the Cascades and on Mount
Osceola by J. P. Lesley. .... A few rods higher up the stream ... . the
first ledge of the labradorite rock appears. ... . It is a perplexing matter to
determine the lines of stratification, as the outcrops are divided by two promi-
nent sets of jointed planes, either of which might be called layers of deposition,
the rock being essentially homogeneous. One set dip about 20° northerly and
are the most numerous. The other dip about 75°, W. 10° 8. The latter cor-
respond better in position to the gneissic strata first seen than the former.”

In the Report for 1871, published in the summer of 1872, we aor’
the following statements regarding the same rocks : —

‘“‘ The first rock seen was called gneiss with nodular orthoclase, with its sup-
posed strata dipping by compass 80° 8. 70° W. . . . . the presumption arises
that these so-called strata may be bands of mica whose planes do not corre-
spond with those of accumulation, but have been superinduced during the meta-
morphism of the rock. The jointed planes dipping about 25° westerly would
be those of stratification, if the rock is stratified. These were pointed out by
J. P. Lesley. A few rods up Norway Brook appears the first ledge of the Ossi-
pyte [the labradorite or Norian rock]... .. Considered as an isolated case it
is difficult to determine the planes of stratification since two prominent sets of
jointed planes exist, either of which might be taken for strata. One set dip
about 20° northerly, and are the most numerous. The other dip about 75°
W. 10° S. As the latter correspond better in position with the supposed
strata of nodular gneiss, it was thought they indicated the proper lines of

* Same statement in Atlas of New Hampshire, 1877, p. 11.

NEW HAMPSHIRE. 389

deposition. The former, however, are what appear at the first glance to be the
strata, and as by this interpretation the position of the rocks at Waterville will
correspond with that in Franconia about the Lafayette range, our former ideas
must be modified.” (J. c., pp. 15, 16.)

Again, in a paper read a few months later, Prof. Hitchcock said : —

“Tn ascending from ‘ Beckytown’ the first rock met with is ‘trachytic
granite.’ This I called ‘gneiss with nodular orthoclase’ in my first sketch,
- with seams or strata dipping (by compass) 80° south, 70° west. . . . . A care-
ful examination of this granitic rock in numerous localities leads to the con-
clusion that it is a true erupted granite and not a gneiss ; though it is possible

the present case may be an exception... .. The first ledge of ossipyte ap-
pears a few rods higher up.... .- The rock seems to be stratified, the planes
dipping about twenty degrees northerly. .... The importance of this discoy-

ery may be best appreciated by remembering that the presence of the lime
feldspars affords a strong presumption that these rocks are Eozoic, and not
metamorphic Paleozoic formations. It seems to be generally admitted by geol-
ogists that these feldspars are confined to the older rocks, except as found in
eruptive trappean and volcanic masses.” (Proc. Am. Assoc. Ady. Sci., 1872,
XXI. pp. 135-151.)

In the second volume of the Final Report on the Geology of New
Hampshire, pages 210, 214, 257, 258, 266, the following statement is
made regarding the labradorite and its associated rocks : —

* None of the Labrador areas, whether in America or Europe, have yet
been carefully studied stratigraphically, so that we have not the means of
knowing their thickness. The lines of iron ore and other foreign minerals
better agree with the idea of stratification than to suppose the masses are erup-
tive. In the study of New England rocks, the labradorite aids us greatly,
since most geologists are prepared to accept it as indicating formations of
Eozoic date ; and, if these triclinic feldspar layers rest upon strata formerly
thought to be Paleozoic, they render it probable that both the underlying and
contiguous masses belong to very ancient systems... . .

“A few rods above [Beckytown] is an exposure of the same rocks with
those seen at the falls, dipping 80°8.10° W. The strata are indicated by folia
of mica and a little of a dark hypersthenic mineral, often forming nodules,
There are jointed planes, also, with a dip westerly of 25°... . . Between Norway
and Cascade brooks there seems to be an anticlinal axis in the porphyritic
gneiss. At first I was satisfied that this rock was gneiss, but did not recognize
its true place with the porphyritic group. Subsequently I referred it to the
‘trachytic’ or Albany granite, buf a reéxamination in 1875 shows that it be-
longs to the oldest of our formations, and is distinctly stratified, traversed by
trap dykes and narrow banded veins of quartz. These exposures do not occupy
more than two hundred feet of distance. A few rods up Norway brook ap-
pears the first ledge of the ossipyte.....

390 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

“ Considered as an isolated case, it is difficult to determine the planes of strati-
fication since two prominent sets of jointed planes exist, either of which might
be taken for strata. One set dip about 20° northerly, and are the most numer-
ous. The other dip about 75° westerly. More definitely, the following are the
supposed strata dips seen in ascending ; about 20° to N. 26° W., N. 86° W.,
N. 34° E., and N. 46° W. The joints have these strikes, N. 22° W., N.,
BUGS: ess The evidence is plain that the Labrador system does not include,
besides the triclinic feldspars, the porphyries and all the Pemigewasset granites.
Hence the statements respecting the nature of the events transpiring in the
Labrador period, — given in the chapter upon the physical history of the
strata, — pertain to a later epoch. .... We are therefore led to believe that
the labradorites alone represent the Labrador system, and, as thus limited, it
has been described... . . There are seven small areas of it, cut by a sort of
‘sienite’ containing triclinic feldspars, and therefore supposed to close the
period. = 245. The reality of the system is not affected by the removal from
it of these various porphyries and granites. Their elimination makes the cor-
respondence perfect between the New Hampshire and Canadian areas, thus
establishing more firmly the existence of the series. Some difference of opinion
may exist among geologists as to the relations between the Montalban and
Labrador systems... .. The labradorite rocks, with a very moderate dip,
rest unconformably upon the greatly upturned edges of the Montalban schists,
as if there had been large upheavals at the close of the Montalban period, and
comparatively little disturbance since... . . The facts as interpreted are of
great consequence, since they fix the geological horizon of the whole Atlantic
system, while considerations of a stratigraphical character confirm this impres-
BON se aetiens The discovery of the Labrador system, overlying the most abun- |
dant and characteristic White Mountain strata, makes it clear that the latter
are older than the former, which are confessedly Eozoic.”

In the Final Report on the Geology of New Hamphire, Vol. IL. p. 667,
Prof. Hitchcock remarks as follows :—

“The Labrador system, if present in New Hampshire, is in very limited
amount. Recent investigations make it difficult to say that the labradorite
rocks are not of eruptive character. They have the composition of dolerite ;
and certain exposures of them upon Mt. Washington are surely injected
dykes. Hence great doubt arises whether the larger area of Waterville
really represents the Labrador system of Canada. At all events its age is
great, for these dykes cut through Montalban strata. This dolerite may be
regarded as one of the oldest eruptive rocks in the state, coming to the surface
in what was the Labrador age of the world.”

Resuming the Report for 1871, we find the relative geological posi-
tion of the formations to be stated as follows :—

“ The sections given of the common granite, trachytic granite and the norian
series (or at least certain felsites,) seem to determine their relative positions,

NEW HAMPSHIRE. 391

the last being at the top. The brecciated granites of Franconia seem to be
older than any of these, and to underlie them. .... If these points are as-
sumed, the porphyritic gneiss can be shown to be at the bottom of the series,
for it lies outside of the lowest of them..... We cannot as yet locate the
andalusite gneiss, save that it is newer than the porphyritic bands as shown at
Moosilauk..... The Coos group of Littleton and Lisbon passes around the
west end of the Bethlehem gneiss, showing that the latter existed before either
the deposition or elevation of the former. This indicates that the whole of
the White Mountain rocks are more ancient than the Coos and Quebec groups
of the Connecticut valley.” (J. ¢., pp. 25-27.)

In the Report for 1872, the Quebec group of the earlier reports is
assigned to the Huronian. The Porphyritic group is described as con-
sisting
“mainly of gneiss full of large crystals of orthoclase feldspar, associated with
ferruginous and other bands. It is regarded as the oldest of all the formations
in the State for these reasons :

“1, The principal range is flanked on both sides by similar varieties of gneiss,
and later series of rocks in the same order. The newer groups being outer-
most, the anticlinal rather than the synclinal structure is suggested, and hence
the greater antiquity of the central range.

“2. This rock is apparently covered by the other members of the gneiss
series in the northern part of the State.

“3. The lithological chamber [? character] corresponds with that of known
Laurentian strata in Canada, North Carolina, and elsewhere.” (J. c., p. 11.)

Of the “ Concord granite” Prof. Hitchcock says : —

“This rock is not a proper granite. There is an arrangement of the parti-
cles of mica along parallel planes, which allows the rock to split readily,
These we regard as strata.” (J. c. p. 12.)

In 1872 Professor Hitchcock presented the following classification of
the rocks of New Hampshire : —

“TT, Kozoic.

“1. Laurentian, including (a) porphyritic gneiss ; (b) White Mountain series,
or andalusite gneiss; (c) Bethlehem, or talcose gneiss ; (d) gneiss of Lake
Winnipiseogee Basin ; (e) gneiss on both flanks of the porphyritic variety in
the south part of the State, subdivided by bands of quartzite, — this carries the
Concord and Fitzwilliam granites, and is probably the beryl-bearing series also ;
(f) range of gneiss between Whitefield and Milan, considerably hornblendic.

“2. Norian, including (a) common granite ; (b) trachytic granite ; (c) four
bands of felsite, both labradorite and orthoclase.

“3. Exeter syenites, including those cutting the Norian at Waterville, Mount
Monadnock, opposite Colebrook, Redhill, &c.

392 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

“4, Huronian. The talcose schist series along Connecticut River, and in
the north part of Cods County.

“5, Older Cambrian? Includes Cods and Merrimack groups, and probably
the ‘ Calciferous Mica Schist’ of Vermont Survey.

“TI. Pa.zEozic.
“ Helderberg limestones.
‘¢ Clay slates.”

In discussing these formations it is later stated as follows : —

“Tf these granites behave like a stratified formation, of course the question
is at once raised whether they should not be regarded as true strata, The
answer cannot be given from position merely, since it is not uncommon to find
sheets of trap or lava holding a perfectly analogous position. We have pre-
ferred to think of the White Mountain country at the end of the Laurentian
period as an immense basin, upon which there was an overflow of common
granite. Being liquid, it spread itself out like water, assuming a horizontal
surface. After a while there was an eruption of trachytic granite, which spread
itself in the same way. Subsequently the felsites were formed above them
conformably. It would be natural to regard these granites, and felsites as
belonging to one period, the Norian. The limits of this system have not been
fixed ; and it seems as if in New Hampshire it should commence in the com-
mon granite, and end with the red orthoclase felsite. . .. .

“Tf the felsite series is of the age of the Upper Laurentian or Labrador of
Logan, then by the law of superposition the strata underneath the common
granite are Lower Laurentian. Observation showed us, at this phase in the
development of the White Mountain structure, two gneisses and a breccia
underneath the granite sheet. The most important is the ‘ Porphyritic gneiss,’
or granite sometimes. This is a gneiss having large crystals, usually one and
a half inches long, of orthoclase, arranged in layers in the mass, with the longer
axes parallel to one another. These we conceive to be the strata... . .

“ The description of the Laurentian rocks in Canada and Europe make men-
tion of large quantities of porphyritic gneiss ; hence we feel warranted in fefer-
ring these lower schists to the Laurentian system. We have yet found nothing
older in the state. ....

“ Our explorations have brought to light the existence of ten distinct periods,
whose records can be traced upon the scarred sides of these highest mountains
of New England.....

“If our limited opportunities have led to such unexpected results, what
may we not look for when the geological structure of the entire metamorphic
area of New England has been carefully studied !” A Am. Assoc. Adv.
Sci., 1872, XXI. pp. 134-151.)

In 1873 Prof. Hitchcock remarks that the evidence of the inferior
position of the White Mountain or andalusite gneiss
“to the Labrador group is very decided. . . . . In the valley of Dry or Mt.

NEW HAMPSHIRE. 893

Washington River, . . . . there is a limited synclinal of ossipyte resting upon
the upturned edges of the andalusite gneiss.” (Proc. Bost. Soc. Nat. Hist.,
1873, XV. pp. 304-310.)

In the second volume of the New Hampshire Geology, Prof. Hitchcock
writes as follows :—

“ Another important doctrine relates to the identification of formations in
our field of labor by means of mineral characters. . .. . The style of similar-
ity made use of for identification is better shown in the porphyritic gneisses.
There are over thirty areas of porphyritic gneiss, in which the feldspar crystals
are very conspicuous for their size, the rock being the Augen gneiss of Europe I
assume that all the areas of this rock are identical in age, and, in speculating
upon the relative positions of the intervening groups, rely upon the correctness
of this starting point. .... The fact of minor differences would seem to con-
firm our assumption of their identity in age, just as the paleontologist finds,
from the presence of the same fossils, proof of contemporaneity in rocks with
dissimilar mineral character. From these facts [the supposed relations of the
rocks] it is inferred that the porphyritic gneiss is older than either the Lake or
the Montalban gneisses, the last being the newest... . . It may as well be
said now as at any time, that nothing older than the porphyritic gneiss has
yet been discovered, This formation constituted the first dry land in the
state.” (I. c., pp. 659, 660, 663, 664.)

The equivalency of the New Hampshire formations with others is in
part stated as follows : —

“ The first two of our groups may be referred to the oldest of these, the Lau-
rentian, without great hesitation... .. A porphyritie or augen gneiss is emi-
nently characteristic of the fundamental rocks in every part of the world, and
hence ours may readily be called Laurentian. .... Those who are familiar
with the crystallines, as Prof. Dana and Dr. Sterry Hunt, after examining some
parts of the Bethlehem group in New Hampshire, say that there is a close
resemblance between them and the Laurentian. .... I have grouped these
rocks, the porphyritic and Bethlehem gneiss, as Laurentian.

“The next division, the Lake gneiss, cannot be so readily assigned. Its
affinities are strongly with the Laurentian, but it is not pyroxenic nor porphy-
ritic, nor does it abound in any triclinic feldspar. . . . . In Massachusetts this
group carries the Hozodén, but that fossil is not confined to the Laurentian.
. . . - The Montalban series are certainly not characteristic of the Laurentian.

. . - Dr. Hunt is satisfied that they overlie the Huronian or greenstones.
Our own observations lead to the view that the typical Montalban rocks un-
derlie the same, as recently stated, though the precise relationship is not beyond
controversy.” (J. c., pp. 668, 669.)

The other formations are in like theoretical manner referred to their
supposed places, with the exception of the Helderberg series.

394 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Again, it is said regarding the arrangement of the feldspar in the
“ Porphyritic gneiss or granite,” that

“ sometimes the crystals are placed in the rock with their longer axes parallel
to each other, and this plane is coincident with that of the strata. On the con-
trary there is often no arrangement to correspond with the stratification. ....
It is obvious that one of these rocks must be granite and the other gneiss. In
our explorations no distinction has been made between them. The assump-
tion has been that the agencies producing the granite operated with greater
intensity, so as to induce a party condition in the mass, and obliterate the strati-
fication without destroying the porphyritic aspect of the rock. If the differ-
ence in condition involves radical distinctions in the mode of origin or in the
time of the fusion, then there are two formations to be considered instead of
one. But in that event the second rock was derived from the first, so that the
assignment of both to one group at present will not lead to error in respect to
the geographical areas occupied by the porphyritic rock. .... Being re-
garded as granite, no pains were taken to observe lines of stratification in it
which doubtless exist. . . . . The determination of the dip of this rock near
the wing road station has been a difficult matter. There are jointed planes,
with scarcely any inclination that might be taken for strata. At the sugges-
tion of Dr. T. Sterry Hunt, a crystalline arrangement of materials dipping
75° S. 40° E. was decided upon to represent the strata.” (Geology of New
Hampshire, II. pp. 98, 99, 102, 274.)

In the same work, pages 472, 513, 514, Mr. J. H. Huntington says of
the porphyritic gneiss ; —

“The fact that rounded fragments of a dark gneiss are found in the porphy--
ritic shows that the porphyritie rock in Fitzwilliam is either intrusive, or that
in the process of metamorphism these fragments were not obliterated, and that

the dark gneiss — which is very limited, but resembles some varieties of the
Bethlehem gneiss — is the older rock.” :

He further points to the fact that the Concord granite at Fitzwilliam
was intrusive. (/.¢., p. 513.)

Mr. Huntington also informs us that the ‘ Concord” granite (Mont-
alban gneiss of Hunt) at Granby, Vermont, is distinctly eruptive, being
seen in contact with a mica schist, sending tongues into the schist and
including fragments of it.

After reading the speculations and conclusions given above, it is some-
what interesting to peruse the following from Prof. Hitchcock’s pen : —

“Tt has been our constant aim to so divorce the facts and theories from each
other in the descriptions, that those who hold different general views from our
own will not find the observations unwarrantably obscured by individual spec-
ulations, .. . . If our interpretation fails in any particular it will be in the

NEW HAMPSHIRE. 395

neglect to invoke all the inversions and faults that are required for truthful
elucidation.” (Geology of New Hampshire, II., pp. 658, 659. See also Am.
Jour. Sci., 1877, (3) XIV., pp. 316-321 ; 1878, XVI., pp. 399-401.)

Since it was evidently the case on the New Hampshire Survey that lith-
ological characters were considered to be all-important in the determina-
tion of the age of the crystalline rocks, it seemed desirable to find out
what amount of skill had been shown in ascertaining what the character
and true names of these rocks really were. A few results of a partial
examination, by Dr. Wadsworth, of one of the collections of the New
Hampshire Survey, obtained from the State Geologist, may therefore be
here introduced for the purpose of throwing light on this question.

As an example of the value of the lithological determinations of this
Survey, the typical Exeter syenite may be first taken. The specimen is
No. 71 of Hawes’s Catalogue, and No. 200 of the “ Preliminary Cata-
logue.” This rock is said by Prof. Hitchcock to be lithologically the
same as the country-rock of the Merrimac mine at Newburyport,* and
the hornblendic granite of Gloucester and Quincy, Mass. All these are
regarded as being probably of Laurentian age, and it is recomended that
search be made in the Exeter rock for mineral veins, on account of its
resemblance to that in which the Merrimac mine is found. The theo-
retical idea at the base of this piece of advice seems to be, that, even in
eruptive rocks, identity of lithological character indicates identity of age,
and the probable occurrence of similar metalliferous deposits. (See Ge-
ology of New Hampshire, I., p. 27 ; IL, pp. 22, 630; III., Part V. p. 34.)
It has by no means been established, as the result of observation, that
rocks of the same geological age and mineralogical composition contain
the same useful ores ; but in the present case it is not necessary to go
so far as this, since it can easily be shown that the rocks to which ref-
erence is here made have no lithological resemblance to each other.

The Quincy and Gloucester (Cape Ann) hornblendic granites (syenites)
were described by Dr. Wadsworth in 1878 (Proc. Bost. Soc. Nat. Hist.,
XIX., pp. 309-316). They consist of grayish, granitoid, coarsely crystal-
line aggregates of feldspar, quartz, and hornblende. In some places this
granite has a reddish color. This rock was found, on careful examina-
tion, at Rockport, to pass, in the same continuous mass, into a micaceous
granite, the only difference between the two being that lepidomelane
replaced the hornblende. The feldspar proved to be mainly orthoclase.
The country-rock of the Merrimac mine, on the other hand, is a dark-

* The real location of the Merrimac mine is, however, in Newbwy, not New-

buryport.

\

396 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

greenish micaceous and hornblendic schist and gneiss, not having litho-
logically a single character of the Quincy or Cape Ann granites or
syenites.

The specimen of “Exeter syenite” obtained from Prof. Hitchcock,
and now in the lithological collection at the Museum of Comparative
Zodlogy, is unlike either of the preceding rocks. Macroscopically it
appears to be composed of feldspar and biotite, a large proportion of the
former appearing as well-striated plagioclase. From its resemblance
to rocks of similar character occurring in Maine, it appeared likely that
it belonged rather to the basalts than to the granites; in other words,
that it was a basic instead of an acidic rock. Microscopic examination
of a thin section showed, in fact, that the rock is composed of plagio-
clase, a little orthoclase, augite, biotite, magnetite, apatite, and some
quartz. The augite is seen in places to have suffered alteration and to
be partly changed to biotite, a common occurrence, rendering it proba-
ble that all the biotite is of secondary origin. The quartz is in small
amounts, and occupies the angular interspaces usually filled by the
base in such rocks when unaltered ; it is therefore probable that it has
either replaced the glass in the process of alteration, or was itself residual
silica after the other minerals had crystallized out. The plagioclase
proves, as determined by the method of Descloizeaux, to be labradorite.
This rock, therefore, is a gabbro, or a coarsely crystallized diabase, and
belongs rather to the so-called Norian rocks (basaltic) than to the gran-
ites. (See M. E. Wadsworth in Proc. Bost. Soc. Nat. Hist., 1877, XIX...
pp. 217-238 ; Bull. Mus. Comp. Zodl., 1879, V., pp. 275-287.)

We have here, therefore, three rocks, almost as different from each
other as it is possible for rocks to be, placed together as alike; and, on
this presumed analogy, practical advice in regard to exploration for min-
ing purposes is based.

Another instance which may be cited as illustrative of the value of
the lithological determinations of the New Hampshire Survey is that of
No. 71 of the Preliminary Catalogue, there called hornblendite, and No.
291 of Hawes’s Catalogue, where it is designated as hornblende schist.
The locality is Piermont, N. H., and the region where this rock occurs is
described as being made up of alternating bands of whetstone slate (mica
schist) and hornblende (hornblende schist). Prof. Hitchcock states that

“ there are five bands of hornblende schist and five of whetstone slate. ... . af
am inclined to carry out the suggestion of a previous page, to the effect that
much of this hornblende should be regarded as Huronian. In agreement with
this notion, it would form hummocks underlying the mica schists, probably

S -

2 1 ) Pe

Le iy oe Ce eae it
oh ’
‘oe ‘

ANNUAL REPORTS : 1869-1872

1st Annual Report, 1869.

Gneissic, Granitic, or
White Mountain Series.

( Staurolite Schists.
| Lower (mostly green) Schists
4 Copper Belt,
Clay Slate.
Garston Conglomerate.

Quebee Group.

(<o|

pper Schists.

2d Annual Report, 1870.

(Normal Gneiss.
Ferruginous Gneiss
Granitic Gneiss.
Feldspathie Mica Schist.
Andalusite Gneiss.
Chiastolite Slates.
Granite.
Syenite.
Porphyritie Granite.
Quartzite.
Limestones,

| Soapstones.

Eozoic.
aaa!
White Mountain or Gneissic Series.

Laurentian (?) Exeter Syenites.
Porphyritic Granite.
Common Granite.
Lower { Merrimac Group.
Silurian | Quebec Group.
Cods Group.
Calciferous Mica Schist.
Clay Slates.

38d Annual Report, 1871.

Porphyritic Gneiss
Bethlehem Gneiss;
Gneiss.

White Mountain or
Andalusite Gneiss,
Common Granite.
Trachytic Granite.
Brecciated Granite.
| Norian.

Clay Slate and Quartzites.
Coos Group.

Laurentian (?)

4th Annual Report, 1872.
Division 1.

{ Hydro-mica and Talcose Schists,
Conglomerates, and Quartzites.

Huronian,

Quartzites, Staurolite Schists,
Mica and Argillaceous Schists,
Calciferous Mica Schist,
Decomposing Slates, Dikes.

DIVISION 2.

Porphyritic Gneiss and Granite.

Bethlehem and Berlin Gneiss.

White Mountain or Andalusite
Gneiss.

Franconia Breccia.

Laurentian.

Common Granite.
Spotted Granite.
‘eat! Series of Compact Feld-

Laurentian

/
i

Norian.
Basin,

spar.
Green Granite and Syenite.

Pemigewasset

DIVISION 3.

§ Porphyritic Gneiss and
| Granite.
Granitic Gneiss.

( Andalusite Gneiss, Ordinary and
t Imperfect Gneiss, the Con-
r cord and Fitzwilliam Granite,
| Soapstone and Limestone.

Quartzite.
Mica Schist.
Andalusite Slates of the Coés Group.

White
Series.

Mountain

I. Eozoic.

Se ee ee ee eS SS ee

II. Paleozoic.

,
(ee eee Se ee EEE eee

Proc. AM. Assoc. ADV. Scl., 1872,

XXTI. 134, 185, 150.

. Porphyritic Gneiss.
. White Mountain Series, or

Andalusite Gneiss.

Bethlehem, or

Talcose Gneiss.

. Gneiss of Lake Winnipi-
seogee Basin.

Gneiss on both flanks of
the Porphyritic variety in
the south part of the
State, carrying the Con-
cord and Fitzwilliam
Granite, and is probably
the Beryl-bearing Series.

Range of Gneiss between
Whitefield and Milan,
considerably hornblendic.

a 9

1. Laurentian.
Ss

Common Granite.

Trachytic Granite.

Ossipy te.

Compact Labradorite Fel-
site.

Dark compact Orthoclase
Felsite.

Red compact and Crystal-

l line Orthoclase Felsite.

ie

&

SS ee ee ee eee
>

2. Norian,

®
.

>

ge

Exeter Syenites.

The Taleose Schist
Series.

ae

Huronian {

Coés Group.

Merrimac Group, and probably
Caleiferous Mica Schist of
the Vermont Survey.

[
}

5. Older Cambrian.

Helderberg Limestone.
{ Clay Slates.

6

Paleozoic.

Eozoic.

say

ye ae ee Se ee eae |

Bost. Soc. Nar. His., 1873,
XV. 304-309.

A Porphyritic Gneiss.

B. Bethlehem Gneiss.

C. White Mountain or Andalusite
Gneiss.

A.

B.
C.

Common Granite of the White
Mountains

Spotted Granite.

Ossipyte

D. Dark compact Labradorite.

FE. Dark compact Orthoclase.

F. Red compact Orthoclase.

G leddish compact Orthoclase

H, Syenites of Exeter and Tripyr-

amid.

faleose and Auriferous Conglomer-
ates.

reen Schists.

Whitish Schists

feldspar and Tale.

{ 4A. Mica Schists of Rockingham
County.
B. Merrimac Group.
Cods Group.
Clay Slates.
Green Granite.

C.
Dz.
z.
#, Mt. Mote Conglomerates

1. Helderberg Limestone.
3. Clay Slates.

Am. Assoc. ApDy. Scr., 1873,
XXII. 120-131.

Winnipiseogee Lake.

Beehyritic Gneiss or Granite. |
‘Winnipiseogee Lake Gneiss For-
mation.

White Mountain Series.

Eruptive Granites of the Ossipee
Mountains.
. Pelsites or Compact Feldspars.

otive Syenite,
| Schist.

es! di le
Paleozoic.

GEOLOGY OF NEw HAmpsHIRE, 1874,
I. 506-539.

t
{ Porphyritic Gueiss.

Atlantic. Laurentian.

Lake Gneiss.
| Montalban.
| Franconia Breccia Group.

| Bethlehem.

( Conway Granite.
| Albany Granite. »
| Chocorua Granite.

Eozoic.

Fine Sedimentary Deposits.
Eruptive Syenite.

Dolomite, Soapstone, and
Serpentine with Siliceous Schist.
Conglomerate.

—— eK

Huronian. Labrador.

| Copper and Iron Beds.

Rockingham Mica Schist.
Merrimac Group.

Cambrian Auriferous Clay Slates.
Coés Group.

Period.

od
a
=
>
mn
2
=
=

Helderberg Period.

WALLING’s ATLAS OF NEW HAMPSHIRE
1877.
qi
=
on
8 { Porphyritic Gneiss.
3
_ { Bethlehem Group.
2 | Lake Winnipiseogee Gneiss.
= {Montalban or White Mountain
2 Series
s | < (Franconia Breccia.
o
~ .
3 3 Conway Granite.
2 | Albany Granite
= ; Chocorua Granite.
—] .
&} Ossipyte.
= | Compact Feldspar.
= | Exeter Syenites.

Lyman Group.

Lisbon Gronp.
Auriferous Conglomerate.

Rockingham Schists.
Calciferous Mica Schists.
Coés Group.

Clay Slates.

Mt. Mote Conglomerate.

Helderberg Limestones.
Slates, Conglomerates, &ec.

a eS

Silurian. Cambrian. Huronian. Labrador or

GEOLOGY oF New HAmMPpsHIRE, 1877,

II. 674, 675.

ees

Eozoic

Paleozoic (?)
en o-oo ee

Paleozoic,

Granitic.

Augitic. Feldspathic.

f

|
|

}
l

I. Stratified Groups.

& Porphyritic Gneiss.

= J Bethlehem Ordinary Gneiss.
2 } Bethlehem Fine-Grained Gneiss.
= | Lake Winnipiseogee Gneiss.
ol

g { Gneiss and Feldspathic Mica
= Schists.

= | Concord Granite.

= Ferrugitious Schists.

& | Fibrolite Schists.

P|

( Franconia Breccia.
Labrador.
Lower Huronian.

Hornblende Schist.
Swift Water Series.
Lisbon Group.
Lyman Group.
| Auriferous Conglomerate.

Upper
IHuronian,

Ferrugirous Slates.
Merrimac Group.
Rockingham Mica Schist.
Kearsarge Andalusite Group.

Cambrian Slates.

Quartzite.

Mica Schist.
Staurolite Slate.
Calciferous Mica Schist.

Lower Helderberg.

Coés Group

Il. Eruptive Masses.

Conway Granite.

Albany Granite.

Chocorua Series.

Granite cutting Coés Group.
Granite not otherwise assigned.
Syenite of Mt. Gunstock, ete.
Exeter Syenite and Diorite.

Labradorite Diorite.
Porphyry.
Pequawket Breccia.
Trachyte.

Diorite.
Diabase.

é

NEW HAMPSHIRE. 397

uncomformably. . . . . This theory will explain the occurrence of the whet-
stone rock in limited outlying patches. .... Were it interstratified with the
hornblende, it should descend into the earth at the same angle to indefinite
depths.” (Geol. of New Hampshire, II., p. 379.)

On examination, however, of this so-called hornblende schist, both in
the hand specimen and microscopic slide, we find it to be a well-marked
diabase, a rock that so far has always, when carefully studied by com-
petent observers, been considered to be eruptive.

No. 121, called “granite from bed” in the Preliminary Catalogue,
(“feldspar from bed,” Hawes’s Catalogue) is the same as the sandstone
No. 117 (Prelim. Cat.), both being masses of feldspar with a little quartz.
No. 86 of the Preliminary Catalogue, called “ serpentine, very impure,”
from Norwich, Vt., is regarded as Huronian. (Geol. of New Hamp-
shire, II., pp. 360, 361.) This rock is a mixture of quartz and horn-
blende, with considerable epidote, but we cannot find the slightest sign
of serpentine about it, either macroscopically or microscopically.

We might go much further in illustrating the character of the litho-
logical determinations of the New Hampshire Survey, and the probable
value of these as forming a basis for a geological classification, but we
forbear.

The criticisms here made depend of course on the authenticity of the
specimens used. On this point we quote Prof. Hitchcock : —

“Pains have been taken to have all the specimens exactly alike, so that
those who obtain duplicate collections, by purchase or otherwise, may be sure
that Mr. Hawes’s accurate descriptions in the chapter on Lithology are appli-
cable to their set.” (Geol. New Hampshire, Part IV. p. 261.)

Dr. Hawes, however, appears to have had his doubts with regard to
the uniform character of the various collections prepared by the New
Hampshire Survey, for he expressly states that it is only for the collec-
tions preserved in the Peabody Museum at Yale College that he is to be
held responsible (J. ¢., p. 255).*

Further remarks on the methods of work of the New Hampshire Sur-
vey, and the character of the classification established on a purely
lithological basis, will be found in the second part of this memoir. At
present it will be sufficient to present in a tabular form (Table B.) the
different results arrived at from year to year, as displayed in the re-

* It is a fact, as shown by actual examination, that, in various collections obtained
from Prof. Hitchcock by different parties, specimens bearing the same number, and
purporting to be from the same locality, are — in some cases, at least — quite differ-
ent from each other.

398 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ports of the State Geologist, published while the work was going on,
The scheme here presented is as complete as it has been found pos-
sible to make it. So numerous are the contradictions in the published
statements made from year to year, that only an intimate personal
acquaintance with the geology of New Hampshire would make it possible
to prepare a connected scheme of the subdivisions of the geological
formations of that State, as from time to time set forth in Professor
Hitchcock’s reports.

EASTERN MASSACHUSETTS.

The first paper of which the writers are aware, relating to the lithol-
ogy of the vicinity of Boston, is that of Mr. 8. Godon, entitled, “ Minera-
logical Observations, made in the Environs of Boston, in the Years 1807
and 1808.” (Mem. Am. Acad., 1809, (1) IIL, pp. 127-154, with a
Table; Ann. Mus. Hist. Nat., 1810, XV., pp. 455-472.) From this
paper it appears that Mr. Godon united under the name amphboloid
all the rocks in this region which he supposed to be composed of am-
phibole and feldspar, when the former mineral predominated. When
the latter was more abundant than the hornblende, the rock was called
felsparoid. It seems from his descriptions that he included under the
term amphiboloid part of the granitic and all of the basaltic rocks
(diabase, diorite, and melaphyr) except the amygdaloid and possibly
some diabase. ;

The amphiboloid was divided into the following series: Common,
Granitic, Trappine, Porphyritic, Epidotic, Quartzose, Micaceous, and
Taleous Amphiboloid. The presence of epidote in small veins both in
the amphiboloid and felsparoid was noticed and described.

The felsparoid included the hornblendic granite both north and
south of Boston, and probably some of the coarser diabases. The fel-
sparoid was said to be often micaceous, and in general to present no
distinct stratification. Mr. Godon also remarks, that “the transition
of felsparoid to petrosilex and porphyritic petrosilex is frequently ob-
served in the compass of the present observations.” He cites, as local-
ities where the transition can be observed, Milton, Blue Hills, and
Malden.

EASTERN MASSACHUSETTS, 399

The felsparoid was divided as follows: Common, Quartzose, Epido-
tic, and Granitic Felsparoid.

The felsite he classes under the head of Petrosilex, but thinks that,
instead of petrosilex being a simple mineral, as it was then generally
regarded, possibly it might be compound in its nature.

He makes the following divisions of the petrosilex : —

Flinty Petrosilex.
“Simple Petrosilex ~ Sonorous “

Jasper Ke

Novacular “
“Porphyritic Petrosilex.”

The name stmple petrosilex seems to have been confined to the more
apparently homogeneous felsites, while the term porphyritic petrosilex
was given to those rocks supposed to have a base of simple petrosilex,
or of felsparoid which held enclosed porphyritic crystals. The simple
petrosilex was thought to pass into wacke and felsparoid.

The common argillite of the country was denominated argzloid, and
it was supposed to pass into petrosilex. He separated it into the fol-
lowing divisions: Common and Novacular Argilloid. An imperfect
chemical analysis was made of some of the argilloid that resembled the
sonorous petrosilex.

The conglomerate of the district was called wacke. Mr. Godon says
of it: —

“ How much attention soever I have paid to the examination of this rock in
situ, I have never observed in it any distinct stratification. It commonly
unites with the rocks previously described, and with amygdaloid, often by an
insensible transition. I possess specimens, which, on pieces of four inches
square each, present its different passages to felsparoid, amphiboloid, simple
and porphyritic petrosilex, argilloid, &c.”

His explanation of its origin is interesting, not only as illustrating
some of the views of that time, but also from its general resemblance to
the conclusions and statements in some more recent articles on the geol-
ogy of Eastern Massachusetts.

“Tf permitted to venture an opinion on the mode of its formation, we may
suppose, that, as we find in it specimens of almost all the rocks, which pre-
dominate in the country, it originated from a motion, which disturbed and
divided the vast deposits of felspathic, porphyritic, petrosiliceous, &c. rocks,
while they were passing from the state of fluidity to that of solidity. This
motion ought to be supposed as having taken place before the complete solidi-
fication of these rocks ; since the compactness of the wacke indicates that its

400 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

elements were in a state of softness, which permitted the union of these hetero-
geneous bodies to form a solid mass. Moreover this aggregation cannot be
supposed to have been formed after the last cast of the primordial deposit, be-
cause the rents, which took place in its mass, have been filled by veins or
rather strata of amphiboloid and felsparoid .... which demonstrates, that
these minerals were still depositing themselves, at a period later than the for-
mation of the wacke.”

The amygdaloidal basalt (melaphyr) was called amygdaloid, and re-
garded as made up of nodules cemented by an apparently homogeneous
reddish-brown or greenish substance. It is said that
“sometimes it occurs with a schistous texture, and even emits an argillaceous
smell, when breathed on. This rock is analogous to the toadstone of the Eng-
lish.”

In Godon’s work is seen the same theoretical belief in the passage
of one rock into another which has since his time played so important
a factor in the geological papers in this region, all resting, however, on
theory and imperfect observation.

Next in order followed Mr. William Maclure’s paper, entitled ‘“ Ob-
servations on the Geology of the United States, explanatory of a Geo-
logical Map,” (Trans. Am. Phil. Soc., 1809, VI, pp. 411-428,) which
was followed by an enlarged paper on the same subject in 1817.
(Ibid., 1818, (2) I, pp. 1-91.) The latter paper was also published
as an independent work in 1817. Maclure, following Werner, arranged
all rocks in four classes: Primitive, Transition, Floetz or Secondary,
and Alluvial Rocks.

Dr. Hunt in his History of the Azoic Rocks (Second Geological Sur-
vey of Pennsylvania, 1878, E., Part I. pp. 23, 24) fell into the error of
making Maclure’s classes of rocks five in number. This was done by
Dr. Hunt’s placing the “Old Red Sandstone” as a distinct class, al-
though Mr. Maclure regarded it as belonging to the Floetz or Secondary
class, being one of the twelve formations into which that class was
divided. Dr. Hunt’s mistake probably arose from the fact that the
“Qld Red Sandstone ” (Mesozoic) of Maclure was colored distinctively
on the map, which was the case with all the classes, but not with the
other formations. This rock was furthermore placed at the base of the
Secondary, and regarded as making a passage from the Transition to
the Secondary classes.

The rocks in the vicinity of Boston were placed by Maclure in the
Primitive and Transition classes. The Transition corresponded gener-
ally with the conglomerate in this region, and it was directly connected
with the Rhode Island Coal Basin, then regarded as Transition.

EASTERN MASSACHUSETTS. 401

Prof. Parker Cleaveland’s “‘ Elementary Treatise on Mineralogy and
Geology ” followed Maclure and Godon in the first edition (1816), with
the addition of the Messrs. Dana’s observations in the second edition
(1822), and therefore no reference need be made to Cleaveland’s views.

In 1818 was published the “Outlines of the Mineralogy and Geology
of Boston and its Vicinity, with a Geological Map,” (Mem. Am, Acad.,
1818, (1) IV., pp. 129-223,) by the brothers J. F. and S. L. Dana. This
was, and is, a very important contribution to the mineralogy and lithol-
ogy of the region, although it is weak in its petrology and geology,
as would naturally be expected from the authors’ line of research.
This paper probably contains the best account of the mineralogy of the
region which has yet been written. The general distribution of the
rocks was shown on a map, but this is very imperfect.

The argillite was regarded as the oldest rock known in the region.
(1. c., p. 199.) The trappean rocks were called greenstone, greenstone
porphyry, and green porphyry ; the last two being regarded as varieties
of greenstone. Attention was especially called to the globular disinte-
gration of the greenstone, so well marked at some localities in this
vicinity. (Proc. Bost. Soc. Nat. Hist., 1877, XIX., pp. 217-237.) They
state that the greenstone has not been observed stratified, and that it
overlies the argillite. It is also said to occur in large beds in the latter,
while it is further claimed that it passes into syenite in places.

The felsite of the-district was divided into two classes: petrosilex and
porphyry. The petrosilex was regarded as a miueral, and the term
applied only to the compact felsite, e. g. the so-called Saugus jasper.
The banding of and irregular colored patches in the felsite were re-
garded simply as variations in the coloring of the mineral, and not strati-
fication. This to a certain extent agrees with the results of modern
investigation. Porphyry was the term applied to the felsite, whose base
was held to be petrosilex, in which minerals were porphyritically em-
bedded, especially quartz and feldspar. The feldspar was said generally
to be in “rectangular crystalline grains, and the quartz in small rounded
nodules.” (/. c., p. 204.) They further state that the “porphyry is un-
stratified in this vicinity, and is intimately connected with Sienite and
Petrosilex, into both of which it passes.” (J. ¢., p. 205.)

The hornblendic and micaceous granites were classed as “sienite.”
The rock was regarded as principally a compound of quartz, feldspar,
and hornblende, but it was said that “ mica sometimes forms a large
proportion of the mass; and hills of Sienite, of a fine structure, con-
taining mica in quantity nearly equal to the other ingredients, prevail

VOL. VII.—No. 11. 26

402 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

for a great extent, particularly at Danvers.” It was also stated that
“Sienite has not been observed stratified in this vicinity.” (lc.
p- 207.)

The amygdaloidal basalt or melaphyr was called Amygdaloid, and
regarded asa rock having a homogeneous base. This base was sup-
posed to have been originally cellular, and the cells afterwards filled
with the minerals, “ Petrosilex, Quartz, Feldspar, Epidote and Carbon-
ate of Lime,” forming the amygdules. The base was denominated
“ Wacke,” which in common with petrosilex and basalt was held to be a
simple mineral. The amygdaloid was said to be destitute of stratifica-
tion, but to present sometimes an imperfect slaty structure. This rock
was said to repose on, and to be associated with, the greywacke (con-
glomerate) of the vicinity.

The conglomerate so common in the vicinity of Boston was called
greywacke, and said to be “composed of nodules of Petrosilex, Quartz,
Argillite, Feldspar, Porphyry, and Sienite; some of these nodules ap-
proach, in magnitude, to rolled masses, and from these we find a grad-
ual gradation to grains of sand.” (/.¢, p. 210.) No stratification was
observed in the greywacke and greenstone ; argillite and amygdaloid are
said to form beds in the greywacke. The amygdaloid was said to be
intimately connected with the greywacke.

In 1818 there was also published Dr. Amos Eaton’s “ Index’ to the’
Geology of the Northern States, with a Transverse Section from Catskill
Mountain to the Atlantic.”

Like Maclure and the brothers Dana he follows the Wernerian system
in a somewhat modified form, dividing the rocks into five classes : Prim-
itive, Transition, Secondary, Superincumbent, and Alluvial.

He explains the presence of granite boulders in the vicinity of Boston
and elsewhere as follows :—

“The sienite stratum was formerly much thicker than at present. This
aggregate has been long known to be strongly disposed to disintegration. It
has dissolved and set loose the enduring granite, which now lies in loose
blocks, with fragments of sienite attached to them, on the surface of the allu-
vial deposites.”

This gives us the germ of the theory of the local origin of boulders
by disintegration. Beyond this, the finding of a syenite boulder in
front of the State House in Boston, and of fragments of argillaceous
and graywacke slate near the same city, appears to be all that he
knew of the geology of this district.

In the second edition, under date of 1820, argillite was thought to

EASTERN MASSACHUSETTS. 403

exist in the vicinity under the “deep alluvion ” on account of the “large
patches and fragments” which he found there (/. ¢c., p. 168). In his
section Dr. Eaton represents hornblende rock as extending from Fram-
ingham to Boston, and dipping towards the sea at a gentle angle. Un-
derlying this blanket of hornblende rock was gneiss, and then granite.
Most of his information regarding the geology of Boston seems to have
been taken from the Messrs. Dana’s Outlines, referred to in the preced-
ing pages.

According to the Rev. Elias Cornelius, the rocks at the eastern por-
tion of the peninsula on which the city of Salem was built “are either
a pure granite, or that variety of it called sienite, the hornblende of
which is diffused in different proportions, from a few specks scarcely
discernible, to very considerable quantities.” (Amer. Jour. Sci., 1821,
(1) IIL, p. 232.)

Dr. Thomas Cooper later remarked that ‘no person accustomed to
volcanic specimens can look at the porphyries from the neighborhood of
Boston, in my possession, and doubt of their volcanic origin.” (Ibid.,
1822, (1) IV., p. 239.)

In his Sketch of the Geology, &c. of the Connecticut, Prof. Edward
Hitchcock states that epidotic and syenitic greenstones belonging to the
Transition exist in the vicinity of Boston, and that dikes of basaltiform
greenstone occur in the syenitic granite in the same region. (Ibid.,
1824, (1) VII., p. 30.)

In a section given by Dr. Amos Eaton in his “ Geological and Agri-
cultural Survey of the District adjoining the Erie Canal,” beginning at
Boston and passing through Waltham, Weston, Sudbury, and Framing-
ham, the country-rock is represented as being “ hornblende rock includ-
ing all its varieties.” This rock is given as extending from Boston to
midway between Framingham and Shrewsbury, and is figured as having a
steep easterly dip. A patch of argillite is represented as horizontally
underlying Harvard College and resting on the upturned edges of the
“hornblende rock.”

In the description of a section made by Prof. Edward Hitchcock, and
placed at the end of the above-quoted work, the rocks in the vicinity of
Boston are said to be syenite, argillite passing into greenstone slate,
pudding-stone, amygdaloid, transition argillite, greenstone, and petrosili-
ceous porphyry. Veins of dark compact greenstone are said not to be
uncommon in syenite and syenitic granite, in the vicinity of Boston.
He cites Dr. J. W. Webster as authority for the statement “that the
only rock ever found im situ in Boston” is syenite. A peculiarity of

404 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Prof. Hitchcock’s section is, that all the formations lying between Bos-
ton and a point some seventy miles west are represented as extending
perpendicularly downwards.

Later, Prof. John W. Webster published his “ Remarks on the Ge-
ology of Boston and Vicinity.” (The Boston Journal of Philosophy and
the Arts, 1824-25, II., pp. 277-292; 1825-26, III, pp. 486-489.) He
states that the Boston peninsula exhibits no rock in place except at one
locality. This was a light gray clay slate (argillite) found by digging
to a considerable depth below the surface. The syenite seen, which had
led to the belief that the rock of the peninsula was syenite, had been
found to be a boulder. Winter Hill of Charlestown (now in Somer-
ville) was said to be composed of clay slate passing on the north into
hornblende slate. The dip was towards the north, at an angle of from
15° to 20°. These rocks contain “ beds and veins of greenstone.” The
lowest rock on Prospect Hill, near Winter Hill, was regarded as a
greenish compact feldspar,* in places strongly resembling some varieties
of limestone. This rock passed into clay slate and dipped “to the
south, inclining a little to the west, under an angle varying from 20°
to 50°.” This was overlain by trap, which it was thought once formed
an extensive bed covering the slate. The Granite Street diabase of
Prospect Hill was described and called a “‘sienitic greenstone.” Like-
wise the diabase of the Powder-House, Somerville, and of Medford, is
mentioned, and the boulder-like disintegration pointed out. The oe-
currence of slate north of the Powder-House was noted, together with
trap overlying the slate or interposed between the strata.

The Roxbury conglomerate was described at some length, and said to
pass “into coarse grau wacké, fine grained grau wacké, and grau wacké
slate which becomes at last distinct clay slate.” The components of the
conglomerate enumerated were hornstone, quartz, compact feldspar,
flinty slate passing to Lydian stone, porphyry, granite, clay slate, no-
vaculite, serpentine, and nephrite. The occurrence of “ trap veins or
dikes ” in the conglomerate was noticed. The conglomerate was said to
pass into amygdaloid, the latter being the overlying rock. Another
transition observed was in crossing the conglomerate of Dorchester,
which was seen to acquire “a greater degree of compactness and uni-
formity of composition until within about three miles of the Blue Hills,
where it passes into compact feldspar, and this last into hornstone.”
The Blue Hills were said to be composed principally of a “ peculiar por-
phyry resembling some of the trachytes.” This rock overlaid the sye-

* This is the indurated argillite of that vicinity.

EASTERN MASSACHUSETTS. 405

nite. The clay slate was thought to underlie all the other rocks to form
the islands in Boston Harbor. The presence of slate in Quincy was
noticed. The rock of Marblehead was designated as syenite. The
Malden felsite was called porphyry, and that of Saugus a “bright red
jasper.” Of Nahant he remarks that the slate “ has undergone a strik-
ing change from the presence of the huge veins of trap with which
it is traversed in every direction.” Prof. Webster previously had pub-
lished a short account of the limestone of Stoneham, which he thought
was probably in a bed. (Bost. Jour. Phil. and Arts, 1823-24, L, pp.
95, 96.)

In the Report on the Geology, Mineralogy, Botany, and Zodlogy of
Massachusetts, by Prof. Edward Hitchcock, published in 1833, consider-
able attention was given to the geology of Eastern Massachusetts. (See
also Am. Jour. Sci., 1833, (1) XXII., pp. 1-70.)

The conglomerate of Brighton and elsewhere was denominated gray-
wacke, said to be stratified, and “sometimes beautifully amygdaloidal.”
The amygdaloidal portion was regarded as “rather wacke than gray-
wacke.” The wacke “often forms the cement of graywacke.” The
localities of the amygdaloid were given as Brighton, Brookline, Newton,
Needham, Hingham, and Saugus. (/. c., pp. 33, 34.) It can be read-
ily seen from reading President Hitchcock’s report that he holds that all
the amygdaloidal melaphyr above mentioned passes into the conglom-
erate, the former being only a variety of the latter. The amygdules
were according to him formed by fusion, except in some cases where
they were formed by infiltration. (/. c., pp. 248-262.) The argillite of
Nahant he regards as part of the graywacke formation belonging to the
Transition. The argillite there he calls flinty slate, and appears to hold
that the induration was caused by the trap veins passing through it.
He also remarks : —

“The slaty structure is rarely lost, except at the junction of the greenstone
and slate, where the two rocks are so intimately blended, that it is not easy to
fix upon the spot where either of them commences. This corresponds with
the opinion of Dr. Maculloch, that nothing but the requisite degree of heat is
necessary to convert argillaceous slate into greenstone.” (J. ¢., p. 265.)

The argillite (argillaceous slate of Hitchcock) in the vicinity of Boston
was described with the graywacke formation, although President Hitch-
cock was inclined to make it older.

The limestone of Stoneham, Newbury, and Chelmsford, he held to be
in beds, modified by the action of granite and syenite, which had oblit-
erated the lines of stratification. (J. ¢., pp. 308-313.)

406 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

The unstratified rocks were assigned an igneous origin without excep-
tion. They were regarded as having been formed during diverse ages,
the author holding that

‘their intrusion among the stratified rocks affords an important clue for de-
termining their relative ages. It is obvious, however, that the intrusion of
the former among the strata of the latter, only proves that the unstratified rock
was formed posterior to the stratified one.”

While we believe that the above quotation from President Hitch-
cock’s work is essentially sound in its views, it will be seen in the sequel
that considerable work has been done in this vicinity from a diametri-
cally opposite point of view.

President Hitchcock further held that all these rocks were
“merely varieties of the same melted mixture, whose peculiarities resulted
from the modes in which they were cooled, and crystallized, and intruded
among the stratified rocks..... On this supposition we are no longer sur-

prised to find it impossible to draw any definite line between the different va-
rieties, nor to find them all united in the same mountain mass.”

?

He inclined to the opinion, that all the unstratified rocks of Massa-
chusetts belonged to a single family, but concluded to treat of them all
under four divisions, viz. greenstone, porphyry, syenite, and granite.
The order of production according to him, beginning with the lowest, is
as follows: granite, syenite, porphyry, and greenstone. He further
states : —

‘‘ Porphyry, however, passes by insensible gradations into sienite ; but the

change commonly takes place in a vertical and not in a horizontal direction.”
(1. c., pp- 402-404.)

The greenstone was regarded as a mixture of hornblende and feldspar,
although some at Nahant was thought to contain augite. This rock
was said to be mixed with syenite in every conceivable mode, and to
pass into it and into granite. The former rock was in general the
younger, although cases were observed in which the latter held frag-
ments of the greenstone. A special case is cited, a little west of Mar-
blehead village, and explained as follows :—

“They certainly appear as if the greenstone had been partially melted down
in the granite ; though the heat was not great enough to complete the fusion.
Or rather, may it not be probable, that the perfect fusion of the rock out of
which these unstratified ones were produced, gave rise to the granite ; while
those portions that were not so entirely fused as to admit of entirely new and
perfect combinations and crystallizations, might have formed those portions of
the rock which I call greenstone.”

EASTERN MASSACHUSETTS. 407

It appears from his remarks in connection with this, that in his opin-
ion a more or less perfect fusion of the same materials may have been
the principal cause of the production of greenstone, syenite, porphyry,
and granite from them.

The unstratified rocks were said to “‘occur in three modes: first,
as protruding irregular masses; secondly, as overlying masses; and
thirdly, as veins.” The greenstone he held to be principally of the first
class, but considered that it also occurred in veins. In regard to these
points he thus expresses himself : —

“‘ Wherever I have seen this rock associated with the graywacke and argil-
laceous slate in the eastern part of the State, it either occupies veins, or pro-
trudes itself in some other form, among, or between, the strata... .. It has
there also the appearance of being regularly interstratified with the slate. But
I am satisfied that this is a deception; that is to say, these supposed beds are con-
nected with some unstratified masses. Yet I think it extremely probable that
some of the greenstone in the vicinity of Boston has resulted from the fusion
of clay slate ; and perhaps it is possible that a particular portion of the slate
might be converted into greenstone, while that around it might remain but
little changed ; and in such a case, the altered rock might at the surface appear
interstratified with the other.”

On Nahant the presence of two sets of trap dikes was noticed, and it
was held that the slate was in the form of a clay at the time of the in-
trusion of the greenstone which altered it. The apparent distinct strati-
fication (jointing ?) of some greenstone on this promontory was regarded
as the result of a concretionary structure. Part of the veins (dikes)
were said to run parallel with the strata, and it was thought that they
would be regarded by some geologists as being regularly interstratified
with the slate. President Hitchcock gives the following as the reasons
why he holds the greenstone to be of igneous origin : —

1, “The resemblance in external characters between some varieties of our
greenstone and the products of existing volcanoes.”

2. “The columnar structure of greenstone.”

3. “ The irregular manner in which greenstone is intruded among stratified
rocks.”

4. “The Mechanical effects of Greenstone upon the Stratified Rocks.”

5. ‘* The Chemical effects of Greenstone upon the Stratified Rocks.”

These views were illustrated by examples. (J. c., pp. 404-442.)

The porphyry is divided into four classes: 1. Compact Feldspar ;
2. Antique Porphyry; 3. “ Porphyry with a base of compact Feldspar
and two or more minerals embedded”; 4. Brecciated Porphyry. The
last he describes as being

408 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

“composed of angular fragments of porphyry and compact feldspar, re-united
by a paste of the same materials, which is itself also porphyritic. Hence it
appears that there must have been an original formation of these rocks (com-
pact feldspar and porphyry) which was subsequently broken up, either by the
mechanical agency of water, or the mechanico-chemical agency of heat, redis-
solving and mingling the materials.”

Of the geological position he remarks : —

“ Am I asked whether the porphyry of Massachusetts belongs to the Primi-
tive, Transition, or Secondary Class? Ireply that it belongs to none of them,
but is a member of a series of rocks consisting of granite, sienite, porphyry,
and greenstone, which have been protruded through or among the stratified
rocks, subsequent to their deposition. ... . The mere existence of these
rocks, therefore, among those of any particular stratified class, does not prove
that they were produced at the same epoch ; it rather proves that the unstrati-
fied rock was of subsequent production. .... I have never met with an
instance in which this porphyry was exhibited in juxtaposition with any strati-:
fied rock ; except as already remarked, the compact feldspar succeeds to the
eraywacke as an older rock and gradually passes into porphyry: ‘This por-
phyry, however, is associated, both on the north and south of Boston, with
sienite ; and in all cases, so far as I have observed, the porphyry lies above the
sienite, and there is a gradual transition between the two rocks,” ©

The compact feldspar was considered to have been derived from the
melting of common feldspar or albite, in connection with other min-
erals. He remarks as follows in regard to this compact feldspar : —

“That it does result from this change in common feldspar, I can hardly
doubt, when I often see specimens that have not entirely lost their foliated
structure, being intermediate between the two minerals... . . It is not un-
common to meet with specimens of porphyry that exhibit traces of an origi-
nally slaty structure in all or a part of the materials composing it. This clearly
points us to a slaty rock as the source from which porphyry was derived. And
sometimes fragments of this rock, along with fragments of compact feldspar,
flinty slate, &c. are scattered through the mass as if partly melted down ; very
much as fragments appear in the slag of a furnace. They seem to be all but
incorporated with the paste, and the whole mass presents an appearance of a
more perfect chemical union than any rock resulting from aqueous agency
ever exhibits, unless it be entirely crystalline. .... The gradual passage of
this rock into sienite, without any apparent change of ingredients, seems to
indicate that the peculiarities of porphyry did not result chiefly from the
nature of the materials employed in its production.” (J. ¢., pp. 442-451.)

Under the term syenite President Hitchcock included “all the varie-
ties of rock, between greenstone and porphyry on one side, and common
granite on the other, into whose composition hornblende enters.” His

EASTERN MASSACHUSETTS, 409

varieties of syenite were six, of which only the first five occur in the dis-
trict under discussion here. It would seem that he included under the
name syenite many diabases as well as hornblendic granites. The divis-
ion of the rock into parallel portions observed in one locality on Cape
Ann he regards as pseudo-stratification (concretionary structure), and
not real stratification. The syenite was said to pass by insensible gra-
dations into granite on one side, and into greenstone or porphyry on the
other, the author remarking as follows :—

“Or when these rocks are wanting, some of the stratified rocks, such as
hornblende slate, graywacke, or new red sandstone repose upon it... .. In
all cases where this rock occurs, we find it between the oldest granite and
greenstone, or the earlier stratified rocks. Hence I infer that a portion of the
materials of which granite is composed, under certain circumstances were con-
verted into sienite, and that these circumstances existed generally in that por-
tion of the melted granite nearest the newer stratified rocks. Or if we suppose
it erupted at a different epoch from the granite, certain causes always forced it
upwards between the granite and the newer rocks. Or if we suppose it to
have resulted from the melting down of the stratified rocks, then perhaps their
more or less perfect fusion produced the difference which we find between
granite and sienite.”

The syenite is said to penetrate “sienite of a different variety, or
greenstone.” President Hitchcock thought that the evidence in favor
of its igneous origin was not strong, yet he held that view. (/.c¢.,
pp. 451-465.) A second and revised edition of this report was published
in 1835, but his views remained essentially unchanged.

In 1838 was published President Hitchcock’s “ Report on a Re-
examination of the Economical Geology of Massachusetts.” In this the
existence of the Lynnfield serpentine was pointed out (pp. 137, 138).

President Hitchcock’s Final Report was published in 1841, and in it
certain changes were made. The graywacke was subdivided into the
Coal Measures, Old Red Sandstone, and Graywacke. The last com-
prised the conglomerates about Boston Harbor and in some other local-
ities (1. c., p. 534).. The argillite in the vicinity of Boston was still
included in it, although lower in the series. Under the head of “ Meta-
morphic Slates” were classed among other formations “ Aggregates of
Porphyry,” “ Varioloid Wacke,” and the “‘ Flinty Slate of Nahant.” Of
the first he says : —

“The best example . . . ., perhaps, is in Hingham, a little west of the vil-
lage ; and in Cohasset, at the head of Nantasket Beach. At the latter place is
a coarse breccia, or conglomerate, which is chiefly made up of fragments of por-
phyry reunited by a cement of the same materials, and is sometimes almost

410 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

reconverted into compact porphyry. .... At the head of Nantasket Beach
is another metamorphic rock, lying contiguous to the breccia just mentioned.
. . . - L incline to the opinion that it was originally a hard slate, like that on
Nahant, and the Brewster Islands, which has been very much changed and
filled up with veins of epidote, by the action of heat. Some of it appears as if
converted into a sort of compact feldspar.” (J. c., pp. 547, 548.)

The latter rock he described in the Report for 1833 (p. 255) as con-
sisting of “fragments of gray and yellowish green compact feldspar,
united by an unknown dark-colored cement.”

The “varioloid wacke” is the amygdaloid of most writers on the
geology of Eastern Massachusetts, and, as in 1833, President Hitchcock
holds that it passes into and “is only a metamorphic variety of the
graywacke formation.” (Final Report, 1841, pp. 548, 549.) In this
Report he held that “the different unstratified rocks appear to be the
result of volcanic agency exerted at different periods under different cir-
cumstances,” and gives reasons for this view, which in part at least
appear to be sound. He further remarks : — ‘

“ The greater degree of crystallization in the older unstratified rocks may be
explained, by supposing a more perfect fusion of the materials than in recent
lavas, and greater slowness in cooling, under perhaps the more powerful pres-
sure of a deep ocean.” (J. c., pp. 790, 791.)

He advances two theories for the origin of the “ Primary Stratified
Rocks.”

1. “The stratified primary rocks are merely the detrital or fossiliferous
rocks altered by heat. As these accumulated at the bottom of the ocean, being
much poorer conductors of heat than water, they would confine the internal
heat that was attempting to escape by radiation, until it became so great as to
bring the matter into a crystaline state : but not great enough to produce en-
tire fusion, so as to destroy the marks of stratification.”

2. “This hypothesis supposes the primary stratified rocks to have been
formed partly in a mechanical and partly in a chemical mode, by aqueous and
igneous agency, when the temperature of the crust of the globe was very high,
and before organic beings could live upon it.”

President Hitchcock seems indeed to incline towards the second
theory. (1. ¢., pp. 796-798.)

In 1839 Mr. William Prescott’s “Sketch of the Geology and Mineral-
ogy of the Southern Part of Essex County, in Massachusetts,” was pub-
lished. (Journal of the Essex Co. Nat. Hist. Soc., 1852, L, pp. 78-91.)
The rocks were described as gneiss, syenite, greenstone, porphyry, silicious
breccia and brecciated porphyry, puddingstone, amygdaloid trap, and

EASTERN MASSACHUSETTS. 411

magnesian serpentine, or verd antique marble. The syenite was said
to pass into greenstone often by insensible shades, This paper locally is
of considerable value. The red felsite of Saugus was described as jasper.

In 1854 the limestones of Eastern Massachusetts were referred to the
Devonian by Dr. Hunt, who remarks as follows : —

“Tn the fourth class we include the crystalline limestone of eastern Massa-
chusetts, which occurs in a great number of places in the towns of Bolton,
Boxborough, Chelmsford, Carlisle, Littleton, Acton, Natick and Sherburne.
It appears according to Hitchcock, in interrupted lenticular masses, lying in
the gneissoid formation, or in the hornblendic slates, and occasionally present-
ing distinct marks of stratification. Still farther east at Stoneham and New-
bury, we find crystalline limestone, sometimes magnesian, in irregular masses,
lying in a rock intermediate between syenite and hornblende slate. Serpen-
tine is found with that of Newbury ; and at Lynnfield, a band of serpentine
has been traced two or three miles N. E. and §$.W..... We have now to
inquire as to the geological age of this great mass of crystalline rocks which is
so conspicuous in Eastern New England... .. When we consider the geo-
graphical position of the Upper Silurian rocks in the Connecticut valley on the
one hand, and the coal fields of southeastern Massachusetts on the other, we
can scarcely doubt that the intermediate gneissoid, and hornblendic rocks, with
their accompanying limestones, are the Devonian strata in an altered condi-
tion.” (Am. Jour. Sci., 1854, (2) XVIIL., pp. 198, 199.)

As late as 1863 the same view of the age of these limestones was
held; while in 1861 Dr. Hunt especially stated, that we recognize
nothing in New England or southeastern Canada lower than the Silu-
rian system.” (Am. Jour. Sci., 1861, (2) XXXL. p. 403 ; 1863, XXXVI,
p. 225; Geology of Canada, 4863, p. 592.)

In 1856 the first definite knowledge of the actual geological position
of any of the rocks in the vicinity of Boston was obtained. Specimens
of a trilobite, belonging to the genus Paradoxides, and a characteristic
fossil of the Primordial, or Potsdam group of the Lower Silurian, had
for many years been in the hands of scientific men in Boston; but the
locality from which they had been obtained was not known. Finally, in
1856, the attention of geologists was called to these trilobites by the
proprietors of a quarry in the argillite at Braintree, and the first notice
of the occurrence of these fossils, and of their true locality, was given to
the public by Prof. W. B. Rogers. (Proc. Bost. Soc. Nat. Hist., 1856,
VI., pp. 27-30, 40, 41, 217; Am. Jour. Sci., 1856, (2) XXII., pp. 296-
298 ; Proc. Am. Acad., III., pp. 315-319.)

Professor Rogers describes the argillite as being included between
large masses of igneous rock, or syenite, and a dipping N. 20° W., at an

412 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

4
angle of about 45°. Dr. C. T. Jackson, later, gave the dip as to the
north, at an angle of 50°. (Proc. Bost. Soc. Nat. Hist., 1856, VI.,
pp. 42-44.) .

The nextyear, Mr. Isaac Lea, however, on examining the position of
the fossils in the rocks, concluded that the dip was to the south, and to
the amount of 68°. (Proc. Phil. Acad. Nat. Sci., 1857, IX., p. 205.)
This latter appears, beyond doubt, to have been a correct statement of
the direction of the dip, if not of its amount.

Dr. Hunt, in 1866, in his paper on the Laurentian Limestones, re-
marks of the crystalline limestones of Bolton and the adjoining towns in
Eastern Massachusetts, that they
“resemble in geognostic and mineralogical characters, those of the Laurentian
system. There are however not wanting reasons for supposing them to be-
long to a more recent geologic period, and the facts recently observed in
Bavaria . . . . show, what was antecedently probable, that similar minera-
logical characteristics may be found in crystalline limestones of very different
ages.” (Geol. of Canada, 1863-66, p. 197.)

This was reprinted without change in 1871, in the revised edition
published in the Report of the Regents for New York. (See also Am.
Jour. Sci., 1854, (2) XVIII., p. 200.)

In 1862, Mr. T. T. Bouvé claimed that he had traced, especially in
Hingham, the passage of the conglomerate into a compact, homogeneous,
almost jaspery rock. (Proc. Bost. Soc. Nat. Hist., 1859, VII., p. 183 ;
1862, VIIL., p. 57.)

In 1867 Prof. Chas. H. Hitchcock remarked that there was reason to
believe that the gneiss and hornblende schist of Andover belonged to
“ Eozoic ages, perhaps as old as the Laurentian. ... . The evidcnce consists
chiefly in the fact that pebbles of the syenite, which is newer than the schist,
occur in the Paradoxides slates near Boston, along with red jasper, green por-
phyry, and other rocks associated with the syenite. These slates form the low-
est member of the Paleozoic series ; hence the rocks from which the pebbles
were derived are older than the Silurian, and must be Eozoic. Lithologically
they resemble the Laurentian gneiss and syenite, in the typical localities.”
(Proc. Essex Institute, 1867, V., pp. 157-160.)

Professor Hitchcock probably had in mind the argillites and conglomer-
ates, of whose age nothing definite is known, for in the Braintree argillite
containing fossils, so far as the published records show, no such pebbles
have been found by the numerous observers who have examined it.*

* Dr. Wadsworth has repeatedly examined the Braintree locality with a like nega-
tive result, so far as the occurrence of pebbles is concerned.

ded

EASTERN MASSACHUSETTS. 413

In the Bulletin of the Essex Institute, August 26, 1869, Vol. I.
p. 106, the following report occurs : —

“ Professor T. Sterry Hunt of Canada gave a geological description and his-
tory of the New England granite formation. The investigation of the last
twenty years had gone very far to destroy the commonly received notion that
granite was the foundation of all other rocks. They were beginning to learn
that instead of the granites being the substrata of the globe, they were rather
secondary or derived rocks, — that they were once great beds of gravel or sand-
stone which had subsequently become crystallized. After speaking of the
probable age of New England granites, Professor Hunt said that in walking
along the shore at Rockport, he could see that the granites were distinctly strati-
fied with alternations of sandstone at different periods. This clearly showed
their sedimentary origin, and probably identified them as being the same as the
granites north and south, and thus enabled them to class them among the De-
vonian rocks. Perhaps ten thousand or fifteen thousand feet beneath them
might be beds holding fossils of the Silurian type, — the same beds, perhaps,
as those cropping out at Braintree. As compared with the rocks at Braintree,
the granites probably were of very recent origin. From careful analysis it was
ascertained that the Rockport granite contained traces of living organisms.
He would mention that with reference to aerolites, chemists had found in
them traces which by them were regarded as certain evidence of the remains of
organic life.”

October 19, 1870, Dr. Hunt said that the granites of Cape Ann and
of Quincy were probably intrusive, (Proc. Bost. Soc. Nat. Hist., 1870,
XIV., p. 46,) which agrees with the view advanced by him in a paper
read before the American Association for the Advancement of Science,
August 20, 1870. (Am. Jour. Sci., 1871, (3) 1, p. 85.) In 1873
the granites of Rockport were stated by him to be distinctly eruptive.
(Proc. Bost. Soc. Nat. Hist., 1873, XV. p. 262.) These statements,
then, according to Dr. Hunt’s published views (Chemical Essays, p. 9),
necessitate a depression of the sediments, out of which the granite was
formed, into the solid earth to the zone of igneo-aqueous fusion, where
the eruptive granite was formed. Part of the original sandstone, how-
ever, remained in this zone unchanged ; while beneath, at a depth of ten
or fifteen thousand feet lower, the Silurian rocks retained their original
character, their fossils remaining unaffected ; and this took place in the
“same beds, perhaps, as those cropping out at Braintree,” the rock at
that place being, as is well known, an easily fusible argillite. Then this
granite was raised again to the surface, thus carrying the argillite un-
metamorphosed twice through the zone of igneo-aqueous fusion.

In November, 1869, Mr. E. Bicknell announced that Zoz0dn Cana-

414 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

dense had been found in the serpentine (limestone) quarry at “ Devil’s
Den,” Newbury. » Prof. Hyatt then remarked that “the rocks of this
county [Essex] had been hypothetically referred to the lowest known
series of Laurentian strata”; but that this was the first instance “in
which any positive evidence has been produced of their actual age.”
(Bull. Essex Institute, 1869, I. pp. 141, 142; American Nat., 1869,
IIl., pp. 498, 499.)
In 1869, Prof. N. 8. Shaler remarked ; —

“There can be no doubt that the syenites, which make up so large a part of
the exposed rocks of Eastern Massachusetts, are the oldest materials found in
this region. .. . . The most remarkable fact which has come under my ob-
servation is the existence of planes of separation in this syenite, which cannot
be referred to joints... .. That Iam not mistaken in referring these frac-
tures to bedding, is, 1 believe, abundantly proven by the details of structure of
the syenite itself, as well as by the relations it bears to the unquestionably
stratified rocks which rest upon it. .... There are visible on the surface of
considerable sheets of this rock, laid bare in the Mitchell quarry near Quincy,
splitting along what I believe to be the plane of stratification, markings indis-
tinguishable from ripple marks. . .. . If these syenites were of igneous origin,
if they had been poured out before the deposition of the adjacent stratified
beds, or thrust through them in a state of fusion, we should expect to find the
usual marks of such actions. In the first of these cases the later sedimentary _
deposits would be found lying unconformably upon the syenite without any
indication of transition ; in the second we should expect to find a clear line of
contact between the syenite and the sedimentary rocks, such as is always to be
found where an intrusive mass of trappean matter cuts more ancient rocks.
What we do find is that the imperfect bedding of the deeper portions of the
syenite becomes more and more clearly defined as we pass towards the exterior
of the mass, and gradually passes into unquestionably sedimentary rock.
Every stage of this transition is not clearly seen, but enough is visible to satisfy
any one that it really exists. The first rocks of quite unquestionable stratified
origin, lie directly to the north of the Quincy syenite hills, and consist of
clearly bedded sandstones, approaching quartzites in their character.....
Their general dip is northerly, with a variable angle of inclination which may
be roughly averaged at twenty degrees. .... Running the same north course
across the break, we come upon the lowest of the Braintree series... .. Its
dip corresponds with the general inclination observable in the supposed strati-
fication of the syenite, as well as that of the quartzites immediately above it.
The whole of this Braintree series is fossiliferous, . . . . and although much
changed by metamorphic action, it is easily perceived that the whole set of
beds contains no trace of shore deposits. Immediately beyond the exposure of
the Braintree beds at Hayward’s Landing, a dislocation has brought the thin
bedded quartzites again to the surface. The alteration in these is so great that

EASTERN MASSACHUSETTS. 415

the rock has assumed something of the appearance of gneiss, and would by
some be classed in that group of rocks... . . The uniform dip away from the
Quincy Hills, shown by all the stratified beds on their flanks, may be regarded
as sufficient proof that their elevation came after the deposition of these beds,”
(Proc. Bost. Soc. Nat. Hist., 1869-71, XIII., pp. 172-178.)

While to one not acquainted with the geological structure of the re-
gion described, Professor Shaler’s paper may appear conclusive ; the
facts, that the granite presents exactly the same intrusive relations to
the argillite that he says it should have if eruptive ; that he mistook for
sandstones and quartzites the Quincy granite itself; that the fossils in
the argillite show that its dip is diametrically the opposite of the one he
has assumed ; that his supposed ripple-marks were the not uncommon
wavy fracture of granite ; and finally that his assumed stratification
planes are joint or structure planes, — leave his conclusions without any
foundation.*

Professor Shaler points to the relations between the argillite and con-
glomerate as exposed while the excavations were being made for the
construction of the Chestnut Hill Reservoir. There he found that the
argillites lay beneath with conglomerate overlying, then more argillite
and above this the conglomerate, indicating it as probable that the argil-
lites and conglomerates in the vicinity of Boston form the same series of
beds, which he considered to belong to the primordial era. (/. ¢., p. 176.)

In 1870, Dr. Hunt, on account of the finding of Hozodn Canadense in
limestones at Newbury (erroneously said to be in the adjoining town,
Newburyport) and Chelmsford, regarded the associated rocks as being of
Laurentian age, saying : —

“ These specimens from Chelmsford, it should be said, have been examined
and satisfactorily identified by Dr. Dawson. The argument from mineralogi-
cal and lithological resemblances in favor of the Laurentian age of the lime-
stone in question is therefore now supported by the undoubted presence in
them of Hozodn Canadense.”

The rocks about Newbury, which it will be recollected were united
by Prof. C. H. Hitchcock to the Cape Ann and Quincy hornblendic

* In the preceding paper of Professor Shaler the misnomer of ‘* Cambridge slates”
was applied to the argillites so well exposed in Somerville, and which properly should
have been called by the name of that city instead of Cambridge. The truth is, that
the locality from which they were named was erroneously supposed to be in Cam-
bridge, when in fact it is in Somerville. This locality was again erroneously said to
be in Cambridge in Professor Shaler’s ‘‘ Question Guide to the Environs of Boston,”
1875, p. 20. No exposure of the argillite is known to exist in Cambridge, although
it has been found there by digging.

416 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

granites (syenites), Dr. Hunt regards as unlike the latter. (Am. Jour.
Sci., 1870, (2) XLIX., pp. 75-78.)

In a paper published in 1870, but said to have been read before the
American Association in August, 1869, Dr. Hunt remarks: “ The gneiss
of Eastern Massachusetts is, as I have recently found, in part of Lau-
rentian age.” (Am. Jour. Sci., 1870, (2) XLIX., p. 184.) Again, the
” at Newburyport, Salem,
Lynn, and Marblehead were referred to the Cambrian, which Dr. Hunt
at that time appears to have regarded as the equivalent of the Huro-
nian. (Am. Jour. Sci., 1870, (2) L., p. 89.) Further, of his Terranovan
series he states : —

same year, the ‘“ diorites and porphyries’

“The micaceous and hornblendic schists, with interstratified fine grained
whitish gneisses (locally known as granites) which I have seen in Hallowell,
Augusta, Brunswick and Westbrook, in Maine, appear to belong to the same
series ; which will also probably include much of the gneiss and mica-schist of
Eastern New England. If this upper series is to be identified with the crystal-
line schists which, in Hastings County, Ontario, overlie, unconformably, the
Laurentian, and yet contain Hozoon Canadense, the presence of this fossil can no
longer serve to identify the Laurentian system. To this lower horizon how-
ever, I have referred a belt of gneissic rocks in Eastern Massachusetts, which
are lithologically unlike the present series, and identical with the Laurentian
of New York and Canada.” (J. c., p. 88.)

In October, 1870, Dr. Hunt stated regarding the geology of Eastern
Massachusetts, that

“the rocks which we have seen may be considered in three classes. <A, the
crystalline stratified rocks ; B, the eruptive granites ; C, th unaltered slates,
sandstones and conglomerates. The former of these may be separated litho-
logically into two divisions; the first being the quartzo-feldspathic rocks.
Among these are included the felsite-porphyrites of Lynn, Saugus and Marble-
head, with their associated non-porphyritic and jasper-like varieties... . .
Associated with them is a granular quartzo-feldspathic rock, which is often
itself porphyritic, with feldspar crystals, and sometimes appears as a fine
erained syenitic or gneissoid rock, often distinctly stratified... . These
rocks are seen intimately associated with the porphyry on Marblehead Neck,
also in Marblehead, and underlying the argillites of Braintree and Weymouth.
The second division of the rocks of class A includes a series of dioritic and
chloritic rocks, generally greenish in color, sometimes schistose, and frequently
amygdaloidal..... This series holds a bed of dolomite at Stoneham, and
serpentine in Lynnfield, . . . . the greenstones of Dr. Hitchcock . . . . ; and
also his varioloid wacke, under which name he describes the green and choco-
late-colored amygdaloidal epidotie and chloritic rocks of Brighton, and the
somewhat similar rocks of Saugus. ... . I regard these two types of rocks as

‘ EASTERN MASSACHUSETTS. 417
forming parts of one ancient crystalline series, which is largely developed in
the vicinity of Boston, and may be traced at intervals from Newport to the
Bay of Fundy, and beyond. To this same series I refer the great range of
gneissic and dioritic rocks with serpentines, chloritic, talcose and epidotic
schists which stretches through western New England. These ancient rocks
are in various places penetrated by intrusive granites, which are generally more
or less hornblendic —the syenites of Hitchcock and others, ... . In this
vicinity, besides the granites of Cape Ann and of Quincy, which probably be-
long to this class, examples of intrusive granites (or syenites) are well seen in
Stoneham and in Marblehead, where they cut the greenish chloritic rocks,
and on Marblehead Neck, where they are erupted among the felsite-porphyries.
In all these places the phenomena of disruption and enclosure of fragments of
the broken rock in the granite are well seen, the lines of contact being always
sharp and well-defined... .. All of these rocks, the granites included, are on
Marblehead Neck traversed by dykes of intrusive greenstone, which are some-
times very similar in aspect to certain of the bedded diorites of A. Of the
rocks of class C, the unaltered argillites of Braintree, holding a primordial
fauna, were observed by Prof. Shaler and myself to rest directly upon a hard
porphyritic felsite of the ancient series. . . . . Reddish granulites directly un-
derlie the black argillites of Weymouth, and the quartzites with conglomerates
and argillites of Chestnut Hill Reservoir, and of Brighton near by, are in sev-
eral places observed in contact with the old dioritic and epidotic rocks already
noticed. The Roxbury conglomerate was observed to contain pebbles of the
felsite-porphyries, diorites and intrusive granites of the older series, besides, as
already remarked by Hitchcock, fragments of argillaceous slate. In this con-
nection may be noticed a remarkable recomposed rock long since correctly
described by the same careful observer, as an aggregate of broken-up and re-
cemented felsite-porphyry. .... He observed it at Hingham and Cohasset,
and Mr. Hyatt has since found it on Marblehead Neck, resting directly on the
parent rock, and very firmly cemented. The unequal weathering of the sur-
face, however, clearly shows both its conglomerate character and the inferior
hardness of the cement. . . . . The fact that the primordial strata of Braintree
have suffered no metamorphism is the more significant, since the beds of sim-
ilar age in New Brunswick and Newfoundland rest unconformably on crystal-
line strata supposed to belong to the same ancient series that underlies the
Braintree beds, and are, like these, unaltered sand and mud rocks.” (Proce.
Bost. Soc. Nat. Hist., 1870, XIV., pp. 45-49.)

This paper of Dr. Hunt’s secured an amount of acceptance amongst
the local geologists far beyond that to which it was entitled ; especially
when it is remembered that it is based on simple assertion, without any
evidence in support of the positions taken. Moreover, these views were
largely in opposition to his life-long teachings, down to 1869, and con-
cerning which statements had been made as positive in character as

those of an opposite ane here upheld. From this time onward, how-
VOL. VII. — No. ‘1. 27

418 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ever, most of the geological papers relating to Eastern Massachusetts
were based on the views of Dr. Hunt as here presented. It may be
noticed that the Quincy granite near the Braintree argillite quarry,
which Professor Shaler regarded as a quartzite or sandstone, Dr. Hunt
calls the same as the Marblehead felsite.

In Mr. Walling’s Atlas of Massachusetts, published in 1871, Prof. C.
H. Hitchcock gave a Geological Description of the State (pp. 17-23).
He writes :—

‘¢ In New England the older strata have been greatly metamorphosed, i. e.,
have been transformed from the original sedimentary sandstones, clays, and
limestones into granite, gneiss, schists, slates, and other crystalline rocks ; and
during the process of change the remains of the primeval animals and plants
have been mostly obliterated.”

To the Eozoic formation he refers

“the syenite and porphyry of Eastern Massachusetts ; and possibly the gneiss
and granite of Plymouth and Bristol counties, and the gneiss and hornblende
schist of Middlesex county. . ... Associated with the Paradoxides slates of
Hingham, is a conglomerate composed of pebbles of syenite and porphyry, like
the ledges of these rocks occupying so much of the area in Essex, Middlesex,
Norfolk, and Plymouth counties. The inference is irresistible, that these un-
stratified rocks existed as ledges before the birth of the trilobite, occupying the
very oldest Paleozoic bed, and therefore they must be of Eozoic age. Litho-
logically, there is a slight resemblance between some of the porphyritic rocks ~
and the Huronian group of Canada and Michigan.”

Prof. Hitchcock is in error here, since the age of the Hingham argil-
lite is not known, and if it were, the finding of fragments of an eruptive
rock in a sedimentary one is no proof of difference in geological age.

In his Notes on Granitic Rocks Dr. Hunt says : —

‘« Felsites and felsite-porphyries are well known in Eastern Massachusetts at
Lynn, Saugus, Marblehead and Newburyport. .... These rocks are through-
out this region distinctly stratified, and are closely associated with dioritic,
chloritic and epidotic strata. They apparently belong, like these, to the great
Huronian system.” (Am. Jour. Sci., 1871, (3) L., p. 84.)

Later, Prof. A. Hyatt remarked : —

“The porphyry of our vicinity, whether Lynn, Marblehead or Newbury-
port is a recomposed rock, a conglomerate composed of more or less rounded
pebbles of more ancient banded porphyry. ... . We meet in the neighbor-
hood of Newburyport with a transition rock made up partly of porphyry, and
then with stratified diorites and slates, which surround the porphyry outcrop
on the sea-face. ... . The northwesterly dip, and northeasterly strike of these
diorites and slates, and the presence of slate rocks in Topsfield and Middleton,

EASTERN MASSACHUSETTS. 419

are difficult to account for unless we imagine the porphyries to be interstrati-
fied with them. The succession of the strata in this part of the country then
would be Eozoénal limestones and serpentines, then slates, then the porphyries
of Kent’s Island and Lynn, then slates and diorites, and lastly, the porphyries
of Marblehead Neck. Either this is the explanation or else we have several
anticlinal axes or folds in the porphyry. In either case all the porphyries are
probably older than the Eozoénal rocks of Newburyport, and underlie them.
The porphyry of Marblehead Neck has the stratified micaceous rocks . .
lying upon its southeastern face, with dip and strike precisely conformable to
the more ancient shore-line formed by the porphyry itself. The porphyry of
Lynn has upon its eastern face the outcropping edges of an enormous overflow
of igneous granite. . . . . In fact, all the difficulties of the survey have arisen
from the enormous sheet, or rather, sheets of igneous rocks, for there seems to
have been several which overspread the surface of the country.” (Bull. Essex
Inst., 1871, IIL, pp. 49-53.)

Dr. Hunt, in reply to Prof. Hyatt’s communication, remarked as fol-
lows :—

“T have expressed the opinion that the porphyries of the eastern coast of
Massachusetts are stratified rocks, belonging, together with their associated
diorites and slates (greenstones, chloritic and epidotic rocks), to the Huronian
system, or Green Mountain system. As regards the limestones with Eozodn,
from eastern Massachusetts, which in the American Journal for Jan., 1870,
I referred to the more ancient Laurentian system. I have in that same journal
for July, 1870, pointed out the fact that the Eozoén of Hastings county, On-
tario, occurs in a series of crystailine schists which I consider newer than the
Huronian, and the equivalent of the White Mountain gneisses and mica-schists,
so that, as I there remark ‘the presence of this fossil can no longer serve to
identify the Laurentian system. .... It will therefore remain for farther
study, to determine how far the crystalline limestones of eastern Massachusetts
belong to the Laurentian, and whether some of them are not included in one
or the other of the newer systems of crystalline schists. The porphyry con-
glomerate noticed by the late President Hitchcock and described by Prof.
Hyatt, are referred to in my paper of last October, mentioned above. This
rock is, I conceive, to be distinguished from the old Huronian porphyry, on
which it often reposes, and from the ruins of which it is derived.” (Bull.
Essex Inst., 1871, IIL, pp. 53, 54.)

If the reader will refer to our quotation of Dr. Hunt’s paper relating
to the Eozoon, or to the original (Am. Jour. Sci., 1870, (2) L., p. 88), he
will see that the remark regarding the value of that supposed fossil was
a hypothetical, and not a positive one, as Dr. Hunt now claims it to have
been. In connection with the above quotation from the Bulletin of the
Essex Institute it may be interesting to remember that a little over a

420 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

year later Dr. Hunt denied that he had held that the White Mountain
series was younger than the Green Mountain or Huronian series. (Am.
Jour. Sci., 1872, (3) IV. p. 51.)

In his address before the American Association, Dr. Hunt still held
that the gneisses and crystalline limestones of Chelmsford, etc. were
Laurentian, and said : —

“The uncrystalline argillites and sandstones, holding Paradoxides, at Brain-
tree, . . . . overlie unconformably crystalline schists of the second series,”
(Huronian or Green Mountain). (Proc. Am. Assoc, Adv. Sci., 1871, XX.,
pp- 10, 32.)

In 1875 Mr. W. W. Dodge classified the rocks of Eastern Massachu-
setts as follows (Proc. Bost. Soc. Nat. Hist., 1875, XVII, pp. 388-
419) :—

I. Crystallines.

Tie Stratined socks i Slates.

B. Conglomerates,

Of the crystallines he says : —

“They underlie unconformably strata holding Paradoxides, etc., and proba-
bly formed hill or island ranges very early in the history of this continent.
... + For the most part, metamorphism has been so complete that these
rocks have lost almost entirely their probable original character,” *

Of the syenite he states : —

“ The abundance of quartz seems to point rather to metamorphic than igneous
condition, and there is probably no doubt that they are chiefly of sedimentary
OTIC... a4. Above Spy Pond in Arlington, there are slaty rocks which pass
through fine grits to coarse sienite by various stages. So, too, in Medford.”

Under the term “ porphyry” he makes four divisions, and thinks that
some of the slates may have been so altered as to closely resemble por-
phyry. He appears to hold that all the rocks included under the term
“‘crystallines ” are of sedimentary origin, and have acquired their pres-
ent character by metamorphism. ‘The eruptive rocks of this region Mr.
Dodge holds to have been derived from the “ crystallines,” remarking : —

“Asa matter of fact, so close is the resemblance in chemical composition,
appearance and minerals developed in them, of the eruptives among the slates
and conglomerates, to the more fusible portions of the crystallines, that it seems
almost unreasonable to doubt that the former were derived from among deep
lying masses of the latter.”

Of the Brighton melaphyr (amygdaloid) he states : —

“Whether these rocks as a whole are of the crystalline stratified class, or
whether they have undergone such change as to entitle them more appropri-

EASTERN MASSACHUSETTS. 4?1

ately to a different name, this is certain, that some of them are found cutting
the slate and conglomerate, and poured out over them, and that near the con-
tact the slate is greatly hardened.”

Of the “ stratified rocks” Mr. Dodge remarks : —

“Between the older rock bands described lie certain more recent and more
clearly stratified rocks. The more recent age of these is shown beyond dis-
pute by their position in relation to the underlying crystallines, as well as by
the fact that they are composd of detritus of the latter, which may not only be
so recognized, but even may at times be referred to the source from which it
was probably derived.”

The “stratified rocks” were separated into slates and conglomerates,
although much argillite was united with the latter. The “slates” in-
cluded not only the Braintree argillite, but also many of the other argil-
lite deposits, and in common were referred to the St. John group. He
further states : —

“Tn all the localities they are much disturbed by intrusions of igneous rock
(which is sometimes poured out over them), are faulted, hardened and dis-
torted.”

Mr. Dodge considers the conglomerate as overlying the Braintree
argillite, and as being probably of Carboniferous age. (Proc. Bost.
Soc. Nat. Hist., 1875, XVII., pp. 411, 412.) Dr. Hunt states in the
same volume that he regards the argillite about Boston Harbor as
being of the same age as the Braintree argillite. (Ibid., pp. 486-488.)

The following is a quotation embodying remarks made by Dr. Hunt,
at a meeting of the Boston Natural History Society, in the same year :—

“The crystalline rock, . . . . seen in contact with the fossiliferons Lower
Cambrian (Menevian) strata of Braintree, Mass., is clearly a variety of the feld-
spar-porphyry or orthopyre, which is so abundant along the eastern coast of
Mssachusetts, Maine and New Brunswick, and which passes on the one hand
into a jaspery petrosilex, and on the other, into a finely granular, almost grani-
tod. rock. .-... The porphyries of Lynn, Marblehead and Salem, and the so-
called jaspers of Saugus and Newbury, belong toit. This rock is identical with
the porphyry which accompanies the crystalline iron ores of southeastern Mis-
souri, and is also well displayed on the north shore of Lake Superior. It is,
in all these localities, distinctly stratified, and has been by the speaker referred
to the Huronian series of rocks. . .. . This porphyry, in the form of pebbles,
often forms conglomerate beds in the Keweenaw or copper-bearing series of
Lake Superior, as is well seen in the Calumet and Hecla, and the Boston and
Albany mines.

“ As regards the relations of the eruptive granites of our Eastern coast to the
Braintree fossiliferous slates, Dr. Hunt remarked that the granites on Marble-

22 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

head Neck, which resemble those of Cape Ann, are seen to cut the still older
porphyries.” (Proc. Bost. Soc. Nat. Hist., 1875, XVII., pp. 508-510.)

In 1876 Mr. T. T. Bouvé called attention to his views regarding the
derivation of the felsites in the vicinity of Boston from the metamor-
phosis of the conglomerates. He remarked that, in 1870,

“ Professor Niles distinctly stated that he had traced in Dedham the con-
glomerate until it passed into porphyry. He had noticed the effects of meta-
morphism where dikes occurred, and he believed that many of our porphyritic
rocks were formed from the conglomerate. These views I sustained by refer-
ring to my own observations, expressing myself satisfied that the porphyries
of our vicinity, as well as the amygdaloids, were altered conglomerates. Dr.
Hunt closed the discussion by saying he was confident that at Marblehead
these rocks were not altered conglomerates. They were derived rocks, but
from the primitive parent rock on which they rested..... In conclusion I
wish not only to re-express my belief in the derivation of these felsites from
conglomerates, but to go one step further, and include among the rocks having
the same origin, some at least of the underlying sienites. ... . But I refrain
from expressing more on this point, simply because my own observations in
the field have been so limited, but will ask if the reputed succession of our
rock deposits is not itself very suggestive.

** Conglomerate.

‘“Compact Feldspar, gradually passing into Porphyry. :

“ Porphyry gradually passing into a rock intermediate between Porphyry
and Sienite.

“ Rock intermediate between Porphyry and Sienite.

“« Sienite.

‘¢ Now if this gives the true succession of our rocks, . . . . I ask if it be not
a fair inference that the causes that led to the changes in the higher portions
of the series, affected all, only to a much greater degree the lower ; that the
heat and aqueous menstruum that softened and partly changed some of the
conglomerates of the upper portion forming the felsite conglomerate, ... -
and which melted the succeeding strata so as to produce first felsites without
crystals, and below these the true porphyries, may not also by its greater
intensity so thoroughly have melted down still lower strata of sedimentary
rocks (conglomerates and slates perhaps), as to entirely resolve them into their
original elements, recrystallize them and thus have formed sienites, some of
which may have even subsequently played the role of eruptive rocks ; for it by
no means follows that because a rock has been sedimentary that it may not
also have become likewise eruptive by being forced upward when in a semi-
fluid state.” (Proc. Bost. Soc. Nat. Hist., 1876, XVIIL., pp. 217-220.)

Prof. Hyatt, in support of Mr. Bouvé’s views, remarked in regard to
the felsite of Marblehead Neck :

EASTERN MASSACHUSETTS. 423

“The porphyries appear to overlie the Salem syenites unconformably, and
together with them are cut by at least two series of dioritic dykes. .... The
porphyries, though varying greatly in aspect and in composition, are neverthe-
less but one formation, and derived from a vast conglomerate which appears in
Lynn, Saugus, and Marblehead, and is reported to occur under the granites on
the Beverly shore. The originally conglomerate nature of the entire deposit is
inferred by extensive observations made by myself at Marblehead Neck, and
by my assistant, Mr. W. O. Crosby, in Saugus, and the general identity of the
purely crystalline porphyries of Lynn with those of Marblehead Neck, which
are undoubtedly merely altered conglomerates. ... . The change into the
felsite is the most instructive, since here it is possible to trace the included
pebble of dark colored, banded porphyry through all stages until it becomes a
mere spot in the light colored matrix. During this change the pebble disap-
pears by some process by which the structure is altered from without, the
centre being the last point to lose its distinctive coloring or structure. ....
The fact seems to me unquestionable, . . . . that both a felsite and a true por-
phyry were formed out of a conglomerate, without any perceptible change
having been made in the form of the contained pebbles.” (Proc. Bost. Soc.
Nat. Hist., 1875-76, XVIIL., pp. 220-225.)

Professor Hyatt points out that the felsite pebbles in the conglomer-
ate are different from the felsite formed from it, and holds that through
pressure or otherwise the pebbles form the thin lamin seen in the
banded felsite. The reader is referred to his very interesting descrip-
tion of the iniaginary processes, since it is too lengthy to transcribe
here. (Ibid., pp. 223, 224.)

Mr. W. O. Crosby, in his Report on the Geological Map of Massa-
chusetts, 1876, says (pp. 7, 8, 10, 11) :—

“The Eozoic rocks of Massachusetts may to a large extent at least be divided
lithologically and chronologically, into three divisions, which, stated in their
order of sequence, are the Norian, the Huronian, and the Mont Alban. I
weigh my words well when I describe these divisions as both lithological and
chronological ; for, . . . . I do not hesitate to affirm that the lithological char-
acters of the divisions which have been worked out among the crystallines of
this region, — the chronological and geographical distinctness of which I can-
not doubt — are as unlike as the faune of any two successive geological for-
mations.”

This statement was in substance again affirmed in 1880. Of the
Norian he writes : —

“The rocks of this formation, though frequently stratified, seem in general to
have been somewhat fluent, and usually exhibit more or less extravasation;
but doubtless in some cases the metamorphic action has stopped short of this
extreme term, though destroying all traces of bedding. In many places....

424 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

the entire formation seems to have been fluent, and the extravasation has been
so extensive that the character of the rock changes nearly every rod. One im-
portant fact should be noted here, viz.: nowhere in this region does the
Norian series appear to be cut by eruptives belonging to another formation, for
all the extravasated rocks of this system may be easily referred to, or shown to
be derived from, its stratified members. .... At Nahant we find slates, be-
lieved to be of Primordial age, resting upon the Norian diorites, which have
been extravasated through the slates, producing extensive alterations. The
coarse grained, readily disintegrating, exotic diorites, so extensively quarried in
Medford, and also occurring in Somerville and Brookline, are, doubtless, ex-
truded portions of this same series, which is the probable seat of many of the
eruptive rocks, especially diorites, cutting the newer formations. . . . . Here
is the real base of our geological column.” (Report, 1876, pp. 8, 10, 11.)

We have in Mr. Crosby’s work above quoted strongly formulated the
principle that any dike cutting another rock is older than the rock it
cuts, and is itself of distinctly recognizable age, —a perfectly logical
result of Dr. Hunt’s teachings. The ‘“ Norian” dikes in Medford,
Somerville, and Brookline were found by Dr. Wadsworth to be diabase
(Proc. Bost. Soc. Nat. Hist., 1877, XIX., pp. 217-237), and to belong to
old basaltic eruptions. We must then conclude, according to this view,
that all basaltic rocks, even the outflows of modern volcanoes, are de-
rived from the Norian system, and are to be mapped and called Norian.
To be sure we find such dikes cutting the Laurentian of other regions,
but in this latter case they were doubtless extravasated downwards,
as advocated recently by Professor Shaler (Mem. Vol. Bost. Soc. Nat.
Hist., pp. 8-15). Dr. Wadsworth has also carefully studied the dikes
both in the so-called Laurentian and Huronian, and can affirm their
unity, both in macroscopical and microscopical characters.

Mr. Crosby divided his supposed Huronian rocks into the following
series: hornblendic granite, felsite, diorite, stratified rocks, and lime-
stone. Of the first series it was said : —

“That these granites are mainly exotic, can scarcely be questioned, for we
have seldom far to look, to find, in the form of enclosed angular fragments of
clearly stratified rocks, evidence of their extravasation, and near the bounda-
ries of the granites we usually find them cutting the adjoining rock, especially
if that is stratified, in a manner incompatible with any theory that would re-
gard them, in their present condition, as indigenous or endogenous. Never-
theless it is doubtless true, as suggested by Prof. N. 8. Shaler, and later by
Mr. T. T. Bouvé, that these granites have been derived from sedimentary
rocks, and have simply reached the final term in the metamorphic process —
igneous, or more probably, igneo-aqueous fusion.” (Report, 1876, p. 14.)

EASTERN MASSACHUSETTS, 425

Mr. Crosby also states emphatically that “this rock [the granite of
Rockport] is destitute of mica, or at least its presence is a very rare
occurrence.” Dr. Wadsworth showed in 1878 (Proc. Bost. Soc. Nat.
Hist., XIX., pp. 309-316) that this was an error, so far as it concerned
at least ninety-five per cent of the rock then quarried at Rockport. It
was also pointed out, that a brief inspection of the two buildings in
which Mr. Crosby had for many years been working would afford evi-
dence of the mistake, as would also an examination of the buildings on
almost any street in Boston. The correctness of these statements of
Dr. Wadsworth was acknowledged by Mr. Crosby in 1880 (Contribu-
tions, p. 28).

Of the felsite Mr. Crosby writes (Report on the Geological Map of
Massachusetts, 1876, pp. 17-21) :—

“In general it is a structureless rock, showing no trace of bedding ; but at
Dungeon Rock in Lynn, it is distinctly stratified, a dense, black variety being
interstratified with a crystalline dioritic variety ; and going northward in
Melrose, the porphyritic character gradually disappears, the felsite becomes
more siliceous, and gradually becomes interstratified with quartzite and horn-
blende slates. The transition is so gradual that it is impossible to define
the boundary between the stratified and unstratified felsites, which proves
there is no break, no natural division here. In Melrose and Malden, and at
other points the porphyritic felsites exhibit frequent local passages into granite
and diorite. It seems probable that considerable portions of this rock have
been in a more or less fluent state, this can scarcely be doubted on the west
shore of Wenuchus Lake in Lynn, where the tongue of granite penetrates the
felsite ; and on Marblehead Neck and the neighboring islands, there is abun-
dant evidence of the softening and extravasation of portions of the rock. Nota-
bly on Marblehead Neck, also on Red Rock in Lynn, and at the Pirate’s Glen
in Saugus, and, perhaps, at other points, this felsite exhibits traces of a con-
glomerate origin. .... There are in this region two principal varieties of
‘banded’ or laminated felsite, which differ widely in their origins ; first, that
in which the banding is due to a conglomerate origin, having been produced
by a flattening of the pebbles of the conglomerate; ... . and second, the
much more abundant and widely distributed variety in which the banding
represents the original bedding of the rock..... The banding commonly
results from the interlamination of thin layers of quartzose and feldspathic ma-
terials. The thickness of the laminz usually varies from a mere line to one-
sixteenth of an inch, and seldom exceeds one-eighth of an inch. That this
banding really represents stratification is proved by the regularity and continu-
ity of the bands, since a banded structure due to the flattening of the pebbles
of a conglomerate would necessarily exhibit little uniformity in the thickness
of the lamin, and I find it difficult to conceive of pebbles flattened to such an
extent as to produce continuous layers of uniform thickness and yards in

426 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

extent ; and it is also proved by the constancy of their strike and dip. It
undoubtedly becomes more crystalline, more granitic, and passes into the
Quincy granite, and the granite of Dedham. It passes into fine grained gran-
ite toward the east and south. Good examples of the granitoid felsite, of
small extent, occur on Lowell’s Island and the north-west shore of Marble-
endian (3

“On Marblehead Neck the breccia, which is here more properly a conglom-
erate, becomes at some points, especially on Lowell’s Island, a coarse, gritty,
feldspathic sandstone, and both the conglomerate and sandstone pass into com-
pact felsite, the former in two distinct ways, which, although observable at
several points in this region, are best exemplified here. These two modes of
metamorphism are: (1) By a blending together of the pebbles and paste,
whereby the outlines of the former are lost, or, when the process is not com-
plete, can only be seen on weathered surfaces. (2) By a flattening or drawing
out of the pebbles into thin lenticular laminz, which, more or less coalescing
at their edges and lying in parallel planes, produce a stratified appearance in
the rock, and give rise to a laminated or banded structure closely resembling
that already described, due to original sedimentation... .. It is further
shown that the massive, structureless felsites, have probably been largely
derived from massive, obscurely stratified, feldspathie slates, while the nor-
mally banded felsite represents a finely and distinctly stratified slate.”

Of the diorites he remarks (Report, pp. 22, 23) :—

“The diorite, like the granite, varies greatly in texture and composition.
. . . . In composition it has a wider range; as already stated, it passes, by an
admixture of quartz, into fine-grained hornblendic granite ; and it is no less
prone, by losing hornblende, to pass into felsite. Fine examples of the transi-
tion between diorite and felsite may be seen in Greenwood and Stoneham.
.... The areas colored as diorite on the map .. . . embrace a great amount
of fine grained hornblendic granite. . . . . Any observer of these two rocks
will agree with me that they admit of neither a lithological nor a geographical
separation. Asarule they are both eruptive, and over large areas they have
been extravasated through each other so extensively, and the action has been
so mutual, that the complication is complete; and I have long been accus-
tomed to speak of them as ‘mixed rocks’; and I know of no term that will
better express their relations, lithologically or petrologically.”

Of the stratified rocks he states (/. c., pp. 28-27) : —

“ As already stated, we find, on going northward through Melrose, the por-
phyritic felsite, gradually becoming less porphyritic and assuming a stratified
appearance. North of Howard Street traces of stratification are common,
though porphyritic felsite occurs as far north as Greenwood. North of Central
Brook, in Saugus, the felsites are chiefly stratified, the bedding increasing
northward, are largely quartzose, passing into quartzite, and are frequently
interstratified with hornblende slate and stratified diorite. No observer, who

EASTERN MASSACHUSETTS. 427

has been over this ground, can doubt that these different rocks are stratigraphi-
cally inseparable. Along the eastern border of this area of stratified rocks,
one can find beautiful examples of the passage of stratified diorite and horn-
blende slate into the eruptive diorite and fine grained hornblendic granite.

There is nothing abrupt about these transitions, the gradation is perfect. . . ..
About four miles farther northwest, in Reading, .... we find the rocks

shading insensibly into eruptive diorite and granite. . . . . The large area of
diorite stretching from Stoneham to Weston includes numerous small patches
of stratified rocks — hornblende slate and petrosilex. ... . They pass fre-
quently into the enclosing rock, showing that they are mere remnants of the
stratified group, which yet preserve traces of the structure once possessed by
the whole mass of the rock. . ... It thus becomes evident that this diorite,
the so-called ‘Salem syenite,’ has, like the diorites elsewhere, resulted from
the extreme metamorphism of the stratified group. ... . I have already indi-
cated that much of the hornblendic granite has been derived by metamorphism
from felsite. . .. . I have shown that this is the probable origin of all the
Huronian granites. It is demonstrated that the most, and probably all, of the
felsites of this region, are now, or were originally, stratified, and may, there-
fore, be logically included in the stratified group... . . The rocks of this
area consisted once, speaking generally, of stratified felsite, hornblende slate
and stratified diorite only, which were then, and are even now, so related strati-
graphically, and exhibit such frequent lithological transitions, as to prove
them to be members of one and the same unbroken series ; and that the fel-
sites, by metamorphism, have given rise to granite, the hornblende slates, in
like manner, to fine grained hornblendic granite approaching diorite, and the
stratified diorite to eruptive diorite.”

Of the Huronian formation in general it is stated (/. c., pp. 27-29) : —

** All the stratified rocks of this formation north and west of Boston, includ-
ing besides the so-called stratified group, the dolomites and stratified felsites,
dip, with few and unimportant exceptions, to the northwest. . . . . Since the
limits of the different rocks are marked by gradual transitions, which precludes
the existence of faults of any great extent ; and since there are no apparent
repetitions of the different rocks, which precludes the existence of considerable
folds of the strata ; we are forced to the conclusion that the geographical ar-
rangement corresponds to the stratigraphical succession ; and the rocks to the
south-east must underlie those to the north-west — the felsites must be older
than the hornblende slates and diorites..... Since the granites are more
intimately associated with the felsites than any other of the stratified rocks,
and are probably derived from them ; and since the exotic granites occur as
eruptives through all the stratified rock ; the inference is plain that the gran-
ites belong normally at the bottom of the series, and may be taken to represent
the lower portions of the felsite..... The oneness of formation has been
established ; it is proved by its petrological, its lithological, and as I have else-

498 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

where shown its chemical characters. I have pointed out, in the preceding
pages, that it distinctly overlies the Norian rocks ; and it no less clearly wnder-
lics the Mont Alban. It exhibits much greater disturbance than the Mont
Alban, but less than the Norian; and near the common boundaries of this
series and the Mont Alban, the gneiss. of the latter is cut by the eruptive gran-
ite and diorite of the former. And since this series so closely resembles, in its
internal characters and its external relations, the Huronian of other regions,
we are bound to conclude that it is the Huronian.”

Of the argillite and conglomerate in the vicinity of Boston, Mr.
Crosby remarks (/. ¢., pp. 40-42) : —

‘¢ Although the fossils characteristic of the Acadian group have been found
at only one locality in Massachusetts, viz. Hayward’s quarry, in Braintree,
yet most observers agree that the greater portion of the slates in the vicinity
of Boston are probably of Primordial age ; and I have so represented them on
the map... . . Theconglomerate so well developed about Boston, and widely
known as the Roxbury conglomerate, is lithologically identical with the car-
boniferous conglomerate of Bristol county and Rhode Island, and seems to be
similarly related to the Primordial rocks. It has been frequently referred to
the Carboniferous horizon ; and, in view of the facts just cited, and the absence
of any positive evidence to the contrary, this is certainly the most probable
view of its age.”

Dr. Wadsworth published, in 1877, a description of the dikes in cer-
tain portions of the Boston basin, based on a study of their field
relations and microscopic characters. He showed that the supposed
hornblende was in general augite, and that the rocks were old basaltic
ones belonging to the melaphyr and diabase varieties. It was also
proved that dikes of two, if not three, distinct periods existed here, and
that the later faulted the earlier ones. In 1878 he also showed that
the Rockport granite was of two varieties, a micaceous and a horn-
blendic one. These were found by careful observation on continuous
exposed surfaces to pass into one another, usually having an intermedi-
ate grade containing both hornblende and mica, (Proc. Bost. Soc. Nat.
Hist., XIX., pp. 217-237, 309-316.)

In a paper “On a Possible Origin of Petrosilicious Rocks” (Proc.
Bost. Soc. Nat. Hist., 1879, XX., pp. 160-169), Mr. Crosby advocated
the view that the felsites were of a deep-sea origin corresponding to the
“red clay” of the Challenger Expedition. In this paper he remarks : —

“These rocks, which are widely distributed over the globe and compose
formations of great extent, are undoubtedly of marine origin. We can scarcely
regard them as shore deposits, and therefore it seems natural and legitimate to
conclude that they were formed in the deep sea; and I would submit that

EASTERN MASSACHUSETTS. 429

they are very fairly represented by the modern abyssal accumulations, espe-
cially if we take into account the enormous period of time which has elapsed
since their formation, and the probable changes in the physics and chemistry
of the sea which it has wrought. The petrosilicious rocks are often distinctly
and beautifully banded. This structure usually results from the alternation of
very thin and regular quartzose and feldspathic layers, and although doubtless
originating in, and determined in direction by, the sedimentary process, I think
it can be proved that it has been made much sharper and more definite by a
subsequent partial segregation of the ingredients, especially the Silica.”

Dr. Wadsworth, from examinations of the felsites in the field and
under the microscope, became convinced, in 1878, that their characters
were the same, excepting in their alteration, as those of the volcanic
rhyolites so common in the Cordilleras, the banding being a fluidal
structure. He convinced himself that we had here the remains of
ancient volcanic action, shown by ashes and other ejected fragmental
material, lava flows, dikes, etc., such as at the present day accompany
eruptive action. Subsequently the whole series had been more or less
altered by various agencies. While in some places a recomposed con-
glomerate was found made up of water-worn detritus resting on the
parent felsite, the structure as a whole was unlike that described by
Messrs. Hyatt and Hunt.

Dr. Wadsworth found that in many cases there had first been thrown
out a rhyolitic ash, and that through, around, and over this ash the
rhyolitic lava has been poured, —the structure being identical with
that observable in the more recent lava flows of the West. No passage
could be traced between the fragmental and non-fragmental forms, but
distinct lines separating the two could be found on careful observation.

Dr. Wadsworth also ascertained that two or more distinct flows had
taken place at Marblehead Neck, and that the felsite also cut the granite
in dikes of various dimensions. The opposite view had been taught by
Messrs. Hunt and Crosby, but their evidence was taken from some fel-
site dikes cutting the granite near the boundaries of the main masses of
these rocks, where only the most careful examination would show which
was the intrusive one. Dr. Wadsworth’s statement was based on find-
ing smaller dikes of felsite, which gradually narrow and come to an end
in the granite and on felsite dikes which hold fragments torn from their
granite walls. He has examined the relations of the two rocks over
much of the coast, and has always found the same relation between
them.

As a result of microscopic investigations the banding was found to be

430 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

a fluidal structure, and not due to a linear arrangement of the quartz
and feldspar, as had been supposed by some. The base of the felsite
has become devitrified, as is seen to have been the case, to a less extent —
perhaps, in many modern rhyolites. The grains and crystals in the
groundmass extend from one band to another, and do not have a strati-
fied arrangement. Dr. Wadsworth’s conclusions were published in
1879, in the Bulletin of this Museum (V., pp. 275-287).

Dr. Wadsworth, not being able to find the time necessary for a thor-
ough examination of the felsites in the vicinity of Boston, with a view
to a complete elucidation of the question whether these rocks were of
sedimentary or of eruptive origin, called for assistance on one of his
pupils, Mr. J. S. Diller, assigning to him, as a subject for a thesis,* the
felsites and the associated rocks in a district selected as being suit-
able for throwing light on the question at issue, and also because it was
one in which Dr. Wadsworth himself had done but little work, so that
the pupil would not feel in any way hampered by conclusions previously
reached by his teachers. All that was asked of Mr. Diller was to ob-
serve the facts carefully, and give the conclusions to wel they led,
let the results be what they would.

Mr. Diller’s work gradually expanded, until he took in finally almost
all of the felsitic area north of Boston. He made a detailed map of the
region examined, and published his results in the Proceedings of the
Boston Society of Natural History; and again, when further extended,
in the Bulletin of this Museum. Mr. Diller showed in the district
studied by him that a series of stratified rocks occurred, which he re-
garded as the oldest rocks observed. These were intersected by dis-
tinctly eruptive granite, and this again by felsite. All were again cut
through and through by successive eruptions of basaltic rocks.

He concludes that there is no true felsite belonging to the stratified
group, the quartzite and slates being wholly distinct from the felsites
both in structure and origin. It will be remembered that Mr. Crosby
stated that, on going northward in Mr. Diller’s district, the porphyritic
character of the felsite gradually disappeared, the latter becoming inter-
stratified with quartzite and hornblende slates. It was said that the
transition was so gradual that no boundary line could be drawn between
the stratified and unstratified portions, thus proving that there was no
break and no natural division here.

* Mr. Diller was at that time (1880-81) a candidate for the degree of S. B. in
Harvard University. Later he was appointed Geologist to the Assos Expedition, and
is now in the employ of the U. 8. Geological Survey.

EASTERN MASSACHUSETTS. 431

Mr. Diller, on the other hand, showed that the felsites were not
exposed within some eight hundred and fifty feet of the stratified rocks,
and that when last seen they were as porphyritic as at any other point.
The accuracy of his work has not been impeached by any one ; nor is it
easy to see how his conclusions can fail of acceptance on the part of
those familiar with the lithological characters of eruptive rocks.

Mr. Diller found the granite breaking through and holding fragments
of the stratified rocks. The felsite was seen always to cut the granite,
but the reverse could not be found. Splinters in curved and crescent-
shaped forms were found in the rhyolitic (felsitic) ash, and in their
forms were identical with those so commonly occurring in the rhyolitie
ashes of the West. These forms, as would naturally occur in such old
glasses, were replaced by silicious material, forming pseudomorphs.
The microscopic characters thus sustained the relations indicated by
the work in the field. Mr. Diller clearly showed that, while part of the
ashy material was earlier than one felsite at least, since it was cut by
dikes of it, it had been in part worked over by water and stratified.
This water-deposited ash passed into conglomerate and sandstone in
places, as is natural in any detrital material having that origin. The
ash when consolidated closely resembled the parent rock, and led many
observers to think that here the transition between sedimentary rocks
and true felsites occurred. (Proc. Bost. Soc. Nat. Hist., 1880, XX.,
pp. 355-368 ; Bull. Mus. Comp. Zool., 1881, VII., pp. 165-180.)

The present writers examined from time to time, in company with
Mr. Diller, parts of the region he was engaged in investigating, as well
as his microscopic sections, and are thus able from personal knowledge
to testify to the accuracy of his work. In our opinion, there can be no
doubt that the felsitic rocks of Eastern Massachusetts show all the
characters that a modern volcanic rhyolitic district would, if situated on
a sea-shore, and afterwards subjected to the ordinary denuding and
metamorphic agencies. In places, in the field, there can be but little
difference perceived between the modern and ancient forms.

In his Contributions to the Geology of Eastern Massachusetts, 1880,
on account of some objections made by Dr. Hunt, Mr. Crosby called the
Norian series of his former paper, the “ Naugus Head series.” The ac-
count of its generally eruptive character is given nearly as before, and
is as follows (pp. 18-22) :—

“That this series of pyroxenic and feldspathic rocks, with its associated
minerals, — which is sometimes stratified, oftener eruptive, frequently very
coarsely crystalline, and always quartzless,— is distinct from anything ob-

432 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

served elsewhere in Massachusetts, cannot be doubted. Lithologically at least
it may be said to be sui generis in Massachusetts geology. The great disturb-
ance which the Naugus Head series everywhere exhibits, and its thoroughly -
crystalline appearance, stamp it as older than the Huronian and Montalban for-
mations. .... What, now, are the geognostical relations of the Naugus Head
series to these Huronian terranes? It underlies them. Everywhere, along
the boundaries of the Naugus Head areas, we find the various members of this
series penetrating and cutting through the Huronian rocks. But the converse
of this is never observed. Nowhere, so far as my observations extend, does
the Naugus Head series appear to be cut by the adjoining Huronian rocks ;
nor by any member of the Huronian system ; nor, in fact, by any rocks not
easily referable, as already stated, to the stratified portions of this series itself.
In short, the Naugus Head series appears to be, as it were, at the bottom ; and,
while it has been extravasated extensively through superjacent formations, it is
penetrated by nothing foreign to itself... . . The Naugus Head series is cer-
tainly distinct from, and... . probably underlies, the Huronian ; and, since
it bears no likeness to the Laurentian system, we are brought to the conclusion,
that, if it is to be correlated with any series already described, that series is
the Norian. In short, the Naugus Head series does not resemble the Lauren-
tian, and is, stratigraphically, where we should expect to find the Norian.
. . .. The only rocks in Massachusetts that have been observed passing below
the Huronian system, or cutting through its lower members, are those compos-
ing the Naugus Head series ; and this, together with its crystalline character
and immense disturbance, convinces me that this series is the oldest in the
State. In the light of our present knowledge the conclusion cannot be
avoided, that the Naugus Head series is the real base of the geological column
of Massachusetts.”

An examination of this so-called Norian or Naugus Head region and
its rocks, by Dr. Wadsworth, has shown that the chief rock is of similar
character to the zircon syenite of Norway, and that it consists princi-
pally of orthoclase, with hornblende and some microcline and plagio-
clase, together with microscopic and macroscopic zircons. The feldspar
has the same inclusions as that of Norway. At Naugus Head a dark
micaceous schistose rock occurs. Through this schist the syenite has
been erupted, forming long bands parallel with the foliation. These
bands vary from a fraction of an inch to many feet in thickness. This
structure strikingly resembles stratification, and has been taken as
such ; but, if a careful examination is made, it will be seen that the
syenite follows the foliation only approximately, and that after running
some distance it suddenly shoots across the foliation into other bands.
Fragments of the schist are abundantly enclosed in the syenite, while
dikes of the latter can be seen cutting directly across the schist.

EASTERN MASSACHUSETTS. 433

At this locality, and elsewhere about the harbor, the syenite can be
seen cutting irregularly through the schist in every direction, thus form-
ing with it a network of fragments. Such also isthe case with the gran-
ite along the seaward’shore of Marblehead, both north and south of the
Neck. The breaking of the syenite across the foliation, the interlock-
ing of its bands, its included fragments of schist, its irregular network
structure as well as its cross dikes, and the fact that, like the granite, it
sometimes covers large areas alone, — all this proves that it is an erup-
tive rock of later date than the schist, and not interstratified with it.
Furthermore, it was observed that the ‘‘ Naugus Head Series” was cut
both by granite and felsite, and that the statements to the contrary
were incorrect. In addition to the syenite numerous dikes of diabase
oceur of different periods, probably separated by long intervals of time.
(Proc. Bost. Soc. Nat. Hist., 1881, XXI., p. 294, Feb. 1, 1882; Har-
vard Univ. Bull., 1882, II., p. 359.)

Of the Huronian system Mr. Crosby remarks (Contributions, pp.
26, 27, 34, 36, 37, 38, 43, 45): —

“The Huronian system in this region, like the Naugus Head series, though
in a somewhat less degree, exhibits great disturbance. Distinctly bedded
rocks are the exception ; and, although many apparently structureless rocks
are probably really stratified, it is undoubtedly true that a large part, perhaps
the greater part, of the formation has been more or less fluent, and extravasa-
tion may be set down as a characteristic structural feature. ... . The Huro-
nian series of Eastern Massachusetts is principally composed of the following
rocks, or, rather, groups of rocks : —

1. Granite (hornblendie and binary).

2. Petrosilex (passing into felsite and quartzite).
3. Diorite (unstratified and largely exotic).

4. Hornblendic Gneiss, Stratified Diorite, ete.

5. Limestone.

“ Although so connected athologically and stratigraphically as to be clearly
members of one great series, yet these various groups are, on the whole, well
separated, occurring mainly in large masses. The stratigraphic distinctness
would be much more striking but for the wide-spread extravasation which
some of the divisions have experienced... . . The true sequence, excluding
some of the limestone, is expressed in the foregoing classification.

“The Huronian granites of this region sometimes exhibit traces of stratifica-
tion. Many examples of well-marked bedding have probably escaped obser-
vation ; and there can be little doubt that the granites in some cases really
possess a gneissic structure where the rock is too coarse and massive to enable
the eye to detect it. Yet I do not hesitate to assert that such phenomena
must, wherever occurring, be very local; for it can be proved beyond a doubt

VOL. VII.— No. 11. 28

434 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

that the Huronian granites of this region are mainly exotic. We have seldom
far to look to find, in the form of enclosed, angular fragments of clearly-strati-
fied rocks, evidence of their extravasation ; and near the boundaries of the
granites we often observe them cutting the adjoining rocks, especially if these
are stratified, in a manner incompatible with any theory that would regard
them, in their present condition, as chiefly indigenous. ... . Believing with
Prof. Shaler, and also with Mr. T. T. Bouvé, that all these granites are meta-
morphosed sediments, I conceive that the peculiar planes of separation (joint
structure) referred to by Prof. Shaler demand a different interpretation from
that proposed by him, for evidence is not wanting of the extravasation of the
granite at many points along the Blue Hill or Quincey and Milton range.
.... Itis well known that the Quincy granite is met along its northern bor-
der by conglomerate and slate. . . . . The actual contact of this rock with the
granite is displayed, however, at a place about } mile west of the Old Col-
OLY tiie Hisees ara The contact line is extremely irregular; and the relation
of the granite tothe semi-crystalline rock is unquestionably that of an exotic.
Some three miles to the southwest, it is very distinctly cut by dykes and irreg-
ular strings of the underlying and surrounding granite. According to Prof.
W. H. Niles, the relations of the granite and slate on Weymouth Fore River,
near the trilobite quarry, affords equally conclusive evidence that at least a
portion of the granite has experienced some extravasation since the deposition
of the slate. The slates on the South Shore R. R., immediately east of the
station at Weymouth Landing, are in contact with the granite, which cuts
through, and overlies them in a manner possible, apparently only with an,
exotic ; and at the contact of the granite and slate, southwest of the station,
Prof. Niles has observed angular fragments of slate actually enclosed in the
granite, though lying only a few inches from their original positions in the
parent bed. The induration, as if by heat, of the slate and conglomerate at
most points where they adjoin the granite, and the frequent development of
amygdaloidal characters in the slate in those places, are also facts which tell
strongly in favor of the former igneous condition of the granite. The evi-
dence of the extravasation of the granite afforded by a study of its relations to
the uncrystalline rocks appears to be sufficiently conclusive as regards the por-
tions of granite immediately involved. ... . At Hospital Point on the Bev-
erly shore, near the water’s edge south of the lighthouse, is a considerable mass
of distinct mica-slate enclosed in the coarse, structureless granite. A smaller
mass of a similar stratified schist is enclosed in the granite near the northern
end of the railroad-cut in Beverly. On Marblehead Neck the relations of the
granite to the fine-grained, distinctly stratified schist occurring there, are such
as to leave no doubt that the granite is exotic, Along the shore, at the south-
western end of the neck, the exposures are magnificent, and one can see, espe-
cially at low tide, numerous angular, ragged, contorted masses of the schist, of
various sizes, enveloped by the granite... . . It has been set down by all
observers as the oldest rock in this region, and this view is abundantly justi-
fied (except as regards the Naugus Head series), not only by its generally

EASTERN MASSACHUSETTS, 435

coarsely crystalline aspect and the great disturbance and almost complete
absence of stratification which it everywhere exhibits, but also by the general
fact that it cuts, as an exotic, all the other members of the Huronian system.
In fact it pierces, in its well-nigh universal extravasation, every rock in this
region, save the Naugus Head series and the newer uncrystallines. In its
geographical distribution we have a strong indication that the granite belongs
to the Huronian system ; for it is co-extensive with that system, and does not
occur beyond its limits. And it will be shown farther on that its lithological
relations point indubitably to the same conclusion. But its petrology makes
it clear that, if the granite is referred to the Huronian series, it must be re-
garded as the lowest, and hence the oldest member of that series. It appears,
in fact, to be the foundation of the Huronian system in Massachusetts... . .
Although well satisfied that a large proportion of the granite has been in a
state of igneous plasticity, yet its relations to the stratified petrosilex and the
many traces of bedding which it still retains forbid me to believe that the mass
of this rock has been elevated from any vast depth ; it seems rather like an
extensive stratified formation which has been softened in situ, and then toa
greater or less extent forced out of its normal position by the pressure of sur-
rounding and overlying terranes.”

Mr. Crosby now classed nearly all of the felsite under that obsolete
term petrosilex, following in this, as in almost all of his work, the ideas
of Dr. Hunt. Of the felsite and its relations to other rocks he says
(J. c., pp. 47-69) : —

“‘ The petrosilex of this region is overlaid at many points by a group of rocks,
including the well-known petrosilex breccia, which appear to be in every case
merely the more or less thoroughly reconsolidated mechanical débris of petro-
silex itself. This second group of petrosilicious rocks constitutes one member or
division of a formation much newer than the Huronian, for which I have pro-
posed, provisionally, the name Shawmut group: a semi-crystalline series
which, as will appear in the sequel, underlies the primordial slate and con-
glomerate of Eastern Massachusetts, coming between these oldest Paleozoic
sediments and the Huronian beds, and appearing to have been formed toward
the close of Eozoic time. The petrosilicious portion of the Shawmut group
includes rocks of all textures, from a coarse breccia to a compact, homogeneous
rock which the naked eye cannot distinguish from the parent petrosilex.
They are proved to be of more recent origin than the Huronian petrosilex, not
only by their petrological relations, since they everywhere overlie the Huro-
nian, but also and most conclusively by the fact, already stated, that they are
composed mainly of the débris of petrosilex, which, where the material is
coarse, can be plainly seen to be identical with that which may be referred
with certainty to the Huronian system. ... . That the Huronian petrosilex
is now for the most part a stratified rock, and was originally wholly so, I can-
not doubt; and it appears most probable that the conditions presiding over its

436 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

deposition differed in degree only, if at all, from those that have obtained in
more recent geological times... . . So far as I am aware, those limited por-
tions of the Huronian petrosilex containing distinctly marked pebbles occur
chiefly in the immediate vicinity of the petrosilex breccia of the Shawmut
eroup ; and in nearly every instance the evidence is plain that the petrosilex
has experienced some extravasation, and has, consequently, been in a more or
less fluent state. .... On the eastern shore of Marblehead Neck ... . the
former reposes directly upon the latter ; and both series have evidently suf-
fered great disturbance. The light-colored Shawmut breccia is cut and torn
in every direction by tortuous dykes of the black petrosilex, which itself very
clearly holds angular pebbles of different varieties of petrosilex. ... . The
main point to be proved in this connection is brought out at this locality with
especial clearness; viz., that the very same petrosilex which holds pebbles
underlies, and is in part eruptive through, the breccia, forcing the conclusion
that, in spite of a certain superficial resemblance, these are distinct formations.

_. « To summarize, the facts observable at the places named, and elsewhere,
compel us to suppose that the petrosilex, while suffering great disturbance, has
been locally crushed and brecciated, and that certain portions of this rock, per-
haps as a consequence of enormous friction, have been softened to an extent
that would permit the envelopment of extraneous masses. . . . . The theory
of the conglomerate origin of the banded petrosilex . . . . is I think based
upon an entire misapprehension of the principal facts.”

He admits the extravasation of the felsite through the brecciated
material or ash, and states that the evidence that the banding was
formed by flattened pebbles “is wholly illusory.” (i. ¢., p. 68.)

He claims that in Melrose is a locality that
“ 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.” (J. ¢., p. 106.)

This locality, however, was, as already mentioned, studied by Mr.
Diller, and nothing of the kind found there. Dr. Wadsworth also ex-
amined the rocks in place at that locality, and found no felsite or any
other rock that ought to be mistaken for a felsite.

Mr. Crosby further states : —

“The conclusion is now certainly safe that the eruptive diorites and the
stratified group are unequally metamorphosed portions of one great series of
basic rocks.” (J. ¢., p. 112.)

But this, like his other conclusions, rests on his inability to distin-
guish between different rocks, and is purely theoretical.

In 1879 Prof, N. 8. Shaler took the ground that the shales and con-
glomerates of Roxbury passed into the amygdaloidal melaphyr, locally

e

EASTERN MASSACHUSETTS. 437

known as the Brighton amygdaloid. He held that a “trained eye”
could trace the gradual passage from the conglomerate to the melaphyr,
remarking as follows : —

“We see .... a mass of conglomerate essentially the same as the Roxbury
pudding stone, only the pebbles and the cement have been greatly affected by
heat, so that the whole is more fused together than in the ordinary forms of
that conglomerate — looking closely we see that the matrix of the pebbles
and to a certain extent the outer parts of the pebbles themselves are filled with
cavities in which similar amygdules have been formed. With care and with
favorable conditions of the quarries, the observer may trace the stages of this
transition, from the faintest beginning of this structure in rocks which are
distinctly conglomerates, into rocks where the blebs have been so completely
developed that every trace of the original pebbly structure is now lost, and
the mass converted into the amygdaloidal trap.” (Proc. Bost. Soc. Nat. Hist.,
1879, XX., pp. 129-133.)

From this he argued that the Roxbury conglomerate had been deeply
buried under sedimentary deposits, forming lofty mountains, which had
since been worn away to their foundations, the conglomerate in the
mean time undergoing fusion, and being thus converted into melaphyr.

Later, the question of the nature of the Brighton melaphyr (amyg-
daloid) was taken up by Prof. E. R. Benton, who showed that the
amygdaloid was a melaphyr or an old altered basalt, which owed its
present variation from basalt to changes subsequent to its original for-
mation. The structure he regarded as pseudo-amygdaloid, and the
supposed pebbles and fragments were shown to be the same as the
remaining portion of the melaphyr. He also points to the fact that Pro-
fessor Shaler’s hypothesis requires the heterogeneous pebbles of the con-
glomerate to be transformed into the homogeneous ones of the melaphyr ;
also, that no part of the melaphyr is like the Roxbury conglomerate.
Professor Benton further showed that all the claims made in the past,
that the melaphyr passed into slates, conglomerates, etc., were without
any basis of fact, for a distinct line of separation between these rocks
could be found whenever they were seen together. (Proc. Bost. Soc.
Nat. Hist., 1880, XX., pp. 416-426.)

Associated with the general belief in the production of crystalline and
eruptive rocks by the fusion of sediments is the theory of the plasticity
of pebbles in conglomerates, a theory at least as old as the days of
Michael Kirwan. Certain forms observed in Brighton were regarded
by Mr. Crosby as the result of the compression of the quartzite pebbles
in a plastic state, but on examining the district in question Dr. Wads-
worth found that these. forms were confined to glaciated surfaces, and

438 THE AZOIC SYSTEM AND ITS SUBDIVISIONS,

were not met with elsewhere in the conglomerate. Some of the inden-
tations were much deeper than they were broad, and hence could not
have been formed by the pressure of one rounded pebble upon another,
Mr. Crosby claimed that certain fissuring in the pebbles occurred dur-
ing the time of the compression; but these fissures were found to be
filled with vein-crystals of quartz, which had suffered the same indenta-
tion as the pebble, so that it was impossible for both to have been
formed at the same time. The forms in question were attributed by
Dr. Wadsworth to glaciation, the rock being found to be smoothed on
both its north and south sides as well as in its depressions ; while sand
action later appeared to have given rise to some of the peculiar forms
observed, either directly or by the modification of previously existing
surfaces. It was also pointed out by him that some pebbles had in-
deed been compressed and indented ; but that the forms exhibited in
such cases were different from the peculiar ones under discussion ; the
indentations, fractures, etc. being such as would naturally take place
when a fragmental rock like quartzite was subjected to compression. It
was furthermore remarked, that no softening and plasticity could have
occurred, because the grains of quartz were round and intact, and not
flattened, as Mr. Crosby’s view demanded.

This subject of plasticity of the conglomerate pebbles was again under —
discussion before the Boston Society of Natural History, Mr. Crosby
claiming that he found compressed forms below the original surface,
and attempting to explain them by saying that they were due to a lack
of cohesion amongst the sand grains in the quartzite. This ground had,
however, been already taken by Dr. Wadsworth for certain forms ob-
served ; and it will be noticed that it begs entirely the question of the
softening and plasticity claimed. A rock that has been softened by
metamorphic agencies, so as to have become plastic, must be so through-
out its entire mass. Mr. Crosby’s view was similar to that which would
be taken in regard to sand, if it were to be said that it ran through a
hole by virtue of its plasticity.

Mr. Crosby also tried to show that the pebbles of the Bellingham
conglomerate had been squeezed or pulled out into spindle-shaped
masses ; but it was evident to more than one who examined his speci-
mens, that he had confounded the adhering matrix with the pebbles
themselves, —a not uncommon mistake. (Proc. Bost. Soc. Nat. Hist.,
1879-80, XX., pp. 308-318, 368-378, 405.)

Mr. W. W. Dodge gave, in 1881, a paper containing numerous details
of his observations in the vicinity of Boston, In this paper he noticed

»

EASTERN MASSACHUSETTS. 439

the occurrence of felsite dikes in the granite, as had been previously
indicated by Dr. Wadsworth and Mr. Diller. (Proc, Bost. Soc, Nat.
Hist., 1881, XXI., pp. 197-216.)

In 1881 Dr. Wadsworth showed that the rock which Mr. Crosby had
regarded as slate or sandstone on Marblehead Neck was really a lava
flow, —a trachyte; and hence it appeared that the theory of the lat-
ter regarding the filling of Marblehead Harbor by sandstone, and its
subsequent erosion, was based on an error regarding the nature of the
rock in question. (Ibid., pp. 288-294.)

Dr. Wadsworth also showed that the so-called diorite or syenite of
Marblehead was a diabase. (Ibid., p. 306.)

It was later pointed out that a supposed felsite on Central Avenue,
Milton, from the detritus of which the associated conglomerate was be-
lieved by Mr. Crosby to have been formed, was simply a modified por-
tion of the conglomerate itself, and that here as elsewhere the usual
mistakes regarding the character of the rocks had been made. (Bull.
Harv. Univ., 1882, II. pp. 431, 432.)

In a paper presented to the Boston Society of Natural History in
1883, it was pointed out by Dr. Wadsworth that the Roxbury conglom-
erate unconformably overlaid the argillite, and contained fragments of
the latter. The argillite showed an old eroded surface, with its strata
cut off; while abutting against the laminze was the conglomerate that
had been deposited on this surface. Mr. Crosby had held ‘that the con-
glomerate lay beneath the argillite, and explained the appearance at the
locality in question by supposing the existence of a closely folded syn-
clinal; but the evidence that the conglomerate is really unconformably
laid down on the older argillite and contains its débris, Dr. Wadsworth
thinks, must be patent to any one who carefully examines the locality.
No faulting exists, for the two rocks are so closely adherent that both
can be removed as a single piece, which distinctly shows the unconform-
ability. It was further shown that an argillite occurred interbedded
with the conglomerate, and that a conglomerate of a later date than the
Quincy granite had been found on the northern side of that rock. The
argillite beneath the conglomerate in the Boston Basin is a fine-grained
compact rock, while that associated with the conglomerate is coarse-
grained arenaceous, passing into sandstone and conglomerate. To the
former belong the Newton, and probably the Braintree argillites ; while
to the latter is provisionally referred the misnamed Cambridge slates.

In 1883 Mr. W. W. Dodge claimed that two granites existed in the
Quincy district, the outer being older than the inner one, but he gave

440 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

no evidence in support of this view. (Amer. Jour. Sci., 1883, (3) XXV.,
pp. 65-71.)

Dr. Wadsworth showed, in 1881, that the Quincy granite was intru-
sive in the fossiliferous argillite, and that the supposed sandstone and-
quartzite of Professor Shaler — the felsite (orthophyre) of Dr. Hunt —
was simply the granite modified by its contact with the argillite. No
faulting existed, for the two rocks were welded into a solid mass. He
also pointed out that the dip of the argillite was southerly, instead of
northerly, as had been claimed by Messrs. Rogers, Jackson, and Shaler.
(Proc. Bost. Soc. Nat. Hist., 1881, XXL, pp. 274-277.)

VERMONT AND WESTERN MASSACHUSETTS.

The geology of Eastern Massachusetts presents us, as has been seen
in the preceding pages, with a complication of problems, toward the
solution of which but little progress was made by the earlier investiga-
tors. A similar condition of things is revealed when we examine what
has been published in regard to the age and sequence of the formations
in the westery portion of the State. Of what was known on this sub-
ject at the time of the publication of President Hitchcock’s Final Re-
port on the Geology of Massachusetts (1841), a good idea may be formed
from the following quotation from that work in regard to the age of the
limestone of Berkshire County : —

“ According to the views which have now been suggested, it will follow, that
wherever we find the limestone of Berkshire county enclosed between strata
of gneiss, it must be regarded as the oldest variety of that rock, or primary
limestone. Where it is interstratified with mica and talcose slate, although
more recent than in gneiss, it ought still probably to be regarded as primary.
But when we find it above these rocks; .. .. then as it lies immediately
beneath clay slate, it may be what is called primary, or what is called transi-
tion, according as we place clay slate on the one class or the other.” (Final
Report on the Geology of Massachusetts, p. 581.)

Prof. H. D. Rogers, in 1856, in his sketch of the geology of the
United States, furnished for publication in Johnston’s Physical Atlas,
makes two periods below the “‘ Cambrian or Older Silurian ”; one, the
“ Azoic or Semi-Metamorphic” ; the other, the ‘ Hypozoic, or True
Metamorphic.” The basis on which this classification rests seems to be

VERMONT AND WESTERN MASSACHUSETTS. 441

a purely imaginative one. As an illustration of the correctness of this
statement, it may be mentioned that the Coast Ranges and the Sierra
Nevada of California are placed in the Azoic by Professor Rogers. At
that time nothing had been ascertained in regard tou the geological age
of these chains ; but they are now known to be made up of rocks not
older than the Carboniferous, the Coast Ranges in fact being of Creta-
ceous and Tertiary age, with associated eruptive and intrusive matter.

Professor Rogers states that the “ Azoic sediments” were succeeded
by those of Paleozoic age, “in some quarters apparently with, in some
without, the interruption of a disturbance of levels.’ The merging of
the Azoic with the Metamorphic Paleozoic under one color on the map
was said to have been

“made indispensable by the absolute impossibility of ascertaining at present
the true base of the Paleozoic system, for the history of Geology forbids us to
believe that research has yet detected the actual horizon of the dawn of ani-
mal and vegetable life upon our globe.”

Professor Rogers, at that time, seems to have known little or nothing
of what had been done toward developing the geological structure of
the country, either by the Lake Superior Survey, or by that of Canada.
Neither was there any other than a purely theoretical basis for his
division of the rocks below the Lower Silurian or Cambrian into a
“‘ semi-metamorphic ” and a ‘‘true metamorphic ” system.

The work of the Canada Geological Survey on the borders of Vermont
— from which in a northeastern direction the rocks become less and
less difficult to decipher, because their relations are less obscured by
metamorphism — could not fail, if it were well done, to be of great
assistance in unravelling the intricacies of New England geology.

In 1849 the first published statement appears to have been made of
the results obtained by that Survey, bearing especially on the question
of the continuity through New England of the Canadian formations.
This statement was made by Dr. Hunt, “of the Geological Commission
of Canada,” and was said to be “a brief sketch of the results obtained
by Mr. Logan and his associates.” It reads as follows :—

“ The facts which we have stated seem to show that the sandstones and red
slates with their chromiferous chloritic bands, are identical with the dolomitic,
chloritic and quartzose rocks of Sutton valley, and these with the serpentines
and quartzose rocks of the valley of the Missisquoi ; so that the whole of the
Green Mountain rocks, including those containing the auriferous quartz veins,
belong to the Hudson River group, with the possible addition of a part of the
Shawangunk conglomerates. The fossiliferous rocks of the St. Francis valley

442 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

are evidently Upper Silurian and referable to the Niagara limestones; a simi-
lar formation has been met with at Gaspé and traced one hundred and fifty
miles S. W.; and from the similarity of the Notre Dame to the Green Moun-
tains and the fact that the Hudson River rocks are continuous along the St.
Lawrence to Cape Rosier, we may conclude that the Upper Silurian rocks will .
be found continuous, or nearly so, throughout. They constitute the calecareo-
micaceous formation of Prof. Adams, which he has traced nearly to the south-
ern line of Vermont. Resting upon this formation in Gaspé is a body of are-
naceous rocks, seven thousand feet thick, which apparently correspond to the
Chemung and Portage group of New York, with the old red sandstones. As
this formation is found extending quite to the Mississippi, it is probable that it
will accompany the Silurian rocks through New England and surround the
coal fields of New Brunswick, of Eastern Massachusetts and Rhode Island.
To this may perhaps be referred in part the rocks of the White Mountains,
which may sweep around the Western border of the Massachusetts anthracite
formation until lost under the super-carboniferous rocks of the Connecticut
River. The limestones of Western New England seem to be no other than the
metamorphic Trenton limestones of Phillipsburg, while the chlorito-epidotic
rocks and serpentines of Sutton valley appear again in the rocks of Southern
Connecticut between these limestones and the new red sandstone. With such
a key to the structure of the metamorphic rocks of New England and of the
great Appalachian chain of which these form a part, we may regard the diffi-
culties that have Jong environed the subject as in a great degree removed, and
the bold conjectures as to their metamorphic origin which have been from time
to time put forth, fully vindicated.” (Am. Jour. Sci., 1850, (2) IX., p.19;
Proc. Am. Assoc. Ady. Sci., 1849, IL, pp. 333, 334.)

In 1850 Dr. Hunt again expressed similar views with regard to the
age of the Green Mountain rocks. (Proc. Am. Assoc. Adv. Sci., 1850, IV.,
pp. 202-204.) He declared that the view of Professor Emmons, that the
Taconic system was older than the Silurian formation, was at variance
with the structure of the region, as deduced both from stratigraphical
and geographical analogies. After summing up the observations which,
according to him, were in absolute contradiction with the theory of the
pre-Silurian age of the so-called Taconic rocks, he remarks :—

“ Such are the facts that lead to the conclusion that between the crystalline
rocks of the East side of Lake Champlain and the North shore of the St. Law-
rence, on the one hand, and the Upper Silurian limestones at the eastern base
of the Green Mountain range on the other, there are no rocks more ancient
than the Silurian.”

Again, in 1854, Dr. Hunt referred the crystalline limestones of West-
ern New England, and their continuation through Northeastern New
York and the adjacent parts of New Jersey and Pennsylvania, to the

VERMONT AND WESTERN MASSACHUSETTS. 443

Lower Silurian, citing Mather’s opinion to the same effect. (Am. Jour.
Sci., (2) XVIIL, pp. 195-198.)

In 1861 Dr. Hunt once more stated his opinion very fully with regard
to the relations of the formations of the Appalachian chain to those
studied out in Canada by the Geological Survey. He closed with the
following statement : —

“Tt will be seen from what has been previously said that we look upon the
Ist and 2d divisions described by Mr. Safford in Eastern Tennessee, as corre-
sponding to the hypozoic series of Rogers and to the Green mountain gneissic
formation, which instead of being beneath the Silurian series, is really a por-
tion of the Quebec group more or less metamorphosed, so that we recognize
nothing in New England or southeastern Canada lower than the Silurian sys-
tem, nor do we at present see any evidence of older strata, such as Laurentian
or Huronian, in any part of the Appalachian chain. The general conclusions
which we have previously expressed with regard to the lithological, chemical
and mineral relations of the Green mountain rocks remain unchanged. (This
Journal [2], IX, 12).”. (Am. Jour. Sci., 1861, (2) XXXI., pp. 392-414.)

In the Geology of Canada, 1863, the Green Mountains of Vermont
were still regarded as belonging to the Quebec group, as above given in
the preceding papers, and as being of Lower Silurian age. (See also
Am. Jour. Sci., 1863, (2) XXXVI. pp. 214-226.)

In the Geology of Canada, 1866, Dr. Hunt stated :—

“ Between the Potsdam and Chazy periods, a rapid continental elevation,
and subsequent gradual depression, allowed a great accumulation of deposits,
which now appear in the rocks of the Green Mountain range... .. To this [the
Upper Calciferous] succeeds the Quebec group, which is regarded as occupying
@ position in the series between the Calciferous and Chazy formations. The
members inferior to it have not yet been observed in eastern Canada, nor, with
the exception of the Potsdam of St. Albans and Georgia in Vermont... .
The Quebec group constitutes the great metalliferous region of eastern Canada,
Vermont and Newfoundland ; and the Upper Copper-bearing series of Lake
Superior, in which the principal mines of that region are found, belongs to the
same geological horizon.” (J. c., pp. 235-237.)

In 1867 Dr. Hunt said that the Quebec group formed the Appalachian
region of Canada and Vermont, as well as the metalliferous terranes of
Lake Superior. He then. considered the Quebec group as being the
equivalent of the Landeilo, and occupying a position between the Upper
Calciferous and Chazy. He further remarked that this group formed
the Notre-Dame: Mountains in Canada, and the Green Mountains in
Vermont, and that it played a very important ré/e throughout the Appa-
lachian chain. (Esquisse Géologique du Canada, pp. 5, 6, 12-16.)

444 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

The same year Dr. Hunt further stated that the Quebec group had
been proved, stratigraphically and paleontologically, to have been de-
posited between the Calciferous and Chazy. Also, that this group
formed that part of the Appalachian region of Canada and Vermont
occupied by the Green Mountains and their prolongation to the south.
(Bull. Soc, Géol. de France, 1867, (2) XXIV., pp. 666, 667.)

Again, the Taconic Mountains and the Green Mountains were said to
be portions of the Lower Silurian, which had escaped erosion ; while the
White Mountains of New Hampshire were said to be a detached portion
of the Devonian formation, the Devonian sediments having been altered
to gneiss and crystalline schists. (/. ¢., p. 687.)

In 1869 Dr. Hunt remarked : —

“Tf we look at the North American continent, we find along its north-east-
ern portion evidence of great subsidence, and an accumulation of not less than
40,000 feet of sediment along the line of the Appalachians from the Gulf of
St. Lawrence southwards, during the paleozoic period, and chiefly, it would
appear, during its earlier and later portions... . . The region of Lake Supe-
rior, Where we find the early portion of the paleozoic age marked by a great
accumulation of sediments, comparable to that occurring at the same time in
the region of New England, and followed or accompanied by similar plutonic
phenomena.” (Canadian Naturalist, 1869, (2) IV., pp. 395, 396 ; Smithso-
nian Report, 1869, p. 206.) ;

Still later Dr. Hunt made the following statement (Am. Jour. Sci.,
1868, (2) XLVI., p. 229) : —

“To sum up in a few words —all the evidence, paleontological and strati-
graphical, as yet brought forward, affords no proof of the existence in Vermont
of any strata (a small spur of Laurentian excepted) lower than the Potsdam
formation, which the present advocates of the Taconic system regard as form-
ing its summit. The supposed more ancient Middle and Lower Taconic
clearly consists in part of Potsdam, in part of Utica and Hudson River, and in
part of the Quebec group, which also constitutes the Lower Taconic. To the
upper portion of the Quebec group, the Geological Survey of Canada have
already referred the gneiss of the Green mountains, assigning to this chain a
synclinal structure, nor does there yet seem to be any reason to believe other-
wise. That strata still older than the Potsdam of New York and Vermont
were deposited in some portions of the oceanic area, is apparent from the exist-
ence in New Brunswick of the St. John’s slates holding a primordial fauna
older than the Potsdam, and it is not impossible that their equivalents may
underlie the Potsdam of Vermont. No such rocks have, however, as yet, been
detected either in Vermont or Canada, and to preserve the name of the Taconic
system as the designation of a series of rocks older than the Potsdam and

VERMONT AND WESTERN MASSACHUSETTS. 445

lying unconformably beneath it, is simply to perpetuate an unfortunate mis-
take which I believe Dr. Emmons, if now living, would, with the paleontologi-
cal evidence at present before the world, be the first to acknowledge.”

In 1870 Dr. Hunt stated regarding the Taconic rocks in Western Ver-
mont and Massachusetts, that “the evidence up to this time adduced
with regard to these so-called Taconic rocks, has failed to show that
they include any strata more ancient than the Potsdam, while most of
them are certainly younger.” Of the Green and White Mountains he
remarks in the same paper : —

‘Tn fact, the schists and gneisses of the White Mountains are clearly dis-
tinct, lithologically, from the Laurentian, the Labradorian and the Huronian,
as well as from the crystalline rocks of the Green Mountains, and from the
fossiliferous Upper Silurian strata which lie at the southwestern base of the
Canadian prolongation of the latter. Having thus exhausted the list of known
sedimentary groups up to this horizon, it was evident that the crystalline strata
of the White Mountains must be either (1) of Devonian age, or (2) something
newer (which was highly improbable); or (3) must belong to a lower and
hitherto unknown series.” (Am. Jour. Sci., 1870, (2) L., pp. 83, 84.)

This language of Dr. Hunt, as well as other remarks in the same
paper, is inexplicable, unless he still, as in the past, regarded the Green
Mountain crystalline rocks as being Lower Silurian, and distinct from
the Huronian.

The remarks of Dr. Hunt above quoted, beginning with the year
1863, possess an additional interest from the fact, to be shown later,
that he claims that during all these years he held an entirely different
opinion as regards the age of the Green Mountains, he, for official rea-
sons, having been advocating views which he himself did not hold.
It seems that later the official reasons became inoperative, for in the
mean while Sir William Logan resigned his position as director of the
Geological Survey of Canada, and Mr. A. R. C. Selwyn was appointed
in his place.

It now appears from Dr. Hunt’s various writings that some time be-
tween the date of the last quoted article, May 10, 1870, and October 19
of the same year, (he in the mean time having been appointed Professor
of Geology in the Massachusetts Institute of Technology,) his views
underwent a somewhat sudden “metamorphism.” This showed itself
in a marked manner, in 1871, in an address from which we proceed to
quote, but it does not appear at first to have affected his general views
of the Taconic system. The reasons for this change of opinion are no-
where given in any satisfactory manner.

446 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Tn his Presidential Address before the American Association for the
Advancement of Science in 1871, Dr. Hunt said :—

“The Taconic system as defined by him [Emmons] may be briefly de-
scribed as a series of uncrystalline fossiliferous sediments, reposing uncon-
formably on the crystalline schists of the Green Mountains, and partly made
up of their ruins; while it is, at the same time overlaid unconformably
by the Potsdam and calciferous formations of the Champlain, and consti-
tutes the true base of the paleozoic column,—thus occupying the position
of the British Cambrian. . .. . The objections made by Emmons to Rogers’s
view of the Champlain age of the Taconic rocks were threefold: first,
the great differences in lithological characters, succession, and thickness,
between these and the rocks of the Champlain division ....; second, the
supposed unconformable infraposition of a fossiliferous series to the Pots-
dam ; and third, the distinct fauna which the Taconic rocks were supposed
to contain.. The first of these is met by the fact now established that in
the Appalachian region the Champlain division is represented by rocks hay-
ing, with the same organic remains, very different lithological characters, and
a thickness tenfold greater than in the typical Champlain region of Northern
New York. The second objection has already been answered by showing that
the rocks which, as in the St. Albans section, pass beneath the Potsdam, are
really newer strata belonging to the upper part of the division, and contain a
characteristic fossil of the Utica slate. As to the third point, it has also been
met, so far as regards the Atops and Elliptocephalus, by showing these two
genera to belong to the Potsdam formation. If we inquire further into the
Taconic fauna, we find that the Stockbridge limestone (the Eolian limestone
of Hitchcock), which was placed by Emmons near the base of the lower Ta-
conic (while the Olenellus slates are near the summit of the Upper Taconic), is
also fossiliferous, and contains, according to the determinations of Prof. Hall,
species belonging to the genera Euomphalus, Zaphrentis, Stromatopora, Chae-
tetes, and Stictopora. Such a fauna would lead to the conclusion that these
limestones, instead of being older, were really newer than the Olenellus beds,
and that the apparent order of succession was, contrary to the supposition of
Emmons, the true one. This conclusion was still further confirmed by the
evidence obtained in 1868 by Mr. Billings, who found in that region a great
number of characteristic species of the Levis formation, many of them in beds
immediately above or below the white marbles, which latter, from the recent
observations of the Rev. Augustus Wing, in the vicinity of Rutland, Vermont,
‘would seem to be among the upper beds of the Potsdam formation, Thus
while some of the Taconic fossils belong to the Potsdam and Utica formations,
the greater number of them, derived from beds supposed to be low down in the
system, are shown to be of the age of the Levis formation. There is, there-
fore, at present, no evidence of the existence, among the unaltered sedimentary
rocks of the western base of the Appalachians in Canada or New England, of
any strata more ancient than those of the Champlain division, to which, from

VERMONT AND WESTERN MASSACHUSETTS. 447

their organic remains, the fossiliferous Taconic rocks are shown to belong.”
(I. c., pp. 22-24.)

Dr. Hunt further remarked in his Presidential Address : —

“The crystalline infra-Silurian strata, to which the name of the Huronian
series has been given by the Geological Survey of Canada, have sometimes
been called Cambrian, from their resemblance to certain rocks in Anglesea,
which have been looked upon as altered Cambrian. . . . . The Anglesea rocks
are a highly inclined and much contorted series of quartzose, micaceous, chlo-
ritic, and epidotic schists, with diorites, and dark-colored chromiferous serpen-
tines, all of which, after a careful examination of them in the collections of the
Geological Survey of Great Britain, appear to me identical with the rocks of
the Green Mountain, or Huronian series. ... . The gneissic series of the
Green Mountains had, however, as we have seen, been, since 1841, regarded
by the brothers Rogers, Mather, Hall, Hitchcock, Adams, Logan, myself, and
others, as of Silurian age. Eaton and Emmons had alone claimed for it a pre-
Cambrian age, until, in 1862, Macfarlane ventured to unite it with the Huro-
nian system, and to identify both with the crystalline schists of similar age in
Norway. Later observations in Michigan justify still farther this comparison.
.... This view [that the White Mountain rocks were Upper Silurian and
Devonian] adopted and enforced by me, was farther supported by Lesley in
1860, and has been generally accepted up to this time. In 1870, however, I
ventured to question it, and in a published letter, addressed to Professor Dana,
concluded, from a great number of facts, that there exists a system of crystal-
line schists, distinct from, and newer than, the Laurentian and Huronian, to
which I gave the provisional name of Terranovan, constituting the third or
White Mountain series.” (Proc. Am. Assoc. Ady. Sci., 1871, XX., pp. 26-
28, 31, 33.)

We invite the reader’s attention to the use of the term Green Moun-
tain series as the equivalent of the Huronian, and to the statement that
the White Mountain series is newer than the Huronian, hoping that he
will remember it a short distance farther on.

Prof. J. D. Dana, in criticising Dr. Hunt’s Address, remarked (Am.
Jour. Sci., 1872, (3) II., pp. 92, 93) : —

“That he has relied, for his chronological arrangement of the crystalline
rocks of New England and elsewhere, largely on lithological evidence, and
commends this style of evidence ;— when such evidence means nothing until
tested by thorough stratigraphical investigation. This evidence means some-
thing, or probably so, with respect to Laurentian rocks; but it did not until
the age of the rocks, in their relations to others, was first stratigraphically
ascertained. It may turn out to be worth something as regards later rocks
when the facts have been carefully tested by stratigraphy. A fossil is proved,
by careful observation, to be restricted to the rocks of a certain period before it

448 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

is used —and then cautiously — for identifying equivalent beds. Has any
one proved by careful observation that crystals of staurolite, cyanite, or andalu-
site, are restricted to rocks of a certain geological period ? Assumptions and
opinions, however strongly emphasized, are not proofs, It is no objection to
stratigraphical evidence that it is difficult to obtain; is very doubtful on ac-
count of the difficulties ; may take scores of years in New England to reach
any safe conclusions. It must be obtained, whatever labor and care it costs,
before the real order and relations of the rocks can be known. Until then,
lithology may give us guesses, but nothing more substantial. Mr. Hunt’s
arguments with reference to the White Mountain Series, as urged by him in
1870, will be found in this journal, IT, L, 83. Both there, and in his ad-
dress, may be seen the kind of evidence with which he fortifies, or sup-
plements, that based on the character of the rocks. Direct stratigraphical
investigation over the region itself, in which all flexures, faults, and uncon-
formabilities have been thoroughly investigated, is not among the foundations
of opinion which he brings forward. He endeavors to set aside the objection
to his views suggested by the existence of Devonian or Helderberg rocks in
central and northern New England ; but he presents, for this purpose, only
some general considerations, of little weight, instead of definite facts as to the
extent and variety of metamorphic strata that are part of, because conformable
to, these Helderberg beds. Had he studied up these stratigraphical relations
with the care requisite to obtain the truth, and all the truth, perhaps he would
not longer say — it is ‘ contrary to my notions of the geological history of the
continent to suppose that rocks of Devonian age could in that region have
assumed such lithological characters.’ Notions often lead astray.” (See also
Am. Jour. Sci., 1871, (8) IL., pp. 205-207; 1872, IV., pp. 104, 105.)

In replying to Professor Dana, Dr. Hunt states (Amer. Jour, Sci.,
1872, (3) IV., p. 51): —

“With regard to New England rocks, Prof. Dana asserts that ‘there are
eneisses, mica schists, and chloritic and taleoid schists in the Taconic series.’
I have, however, shown in my address that Emmons, the author of the Taconic
system, expressly excluded therefrom the crystalline rocks, which he included
in an older primary system; excepting, however, certain micaceous and tal-
cose beds, which he declared to be recomposed rocks, made up from the ruins
of the primary schists, and distinguished from these by the absence of the
characteristic crystalline minerals which belong to the Green Mountain pri-
mary schists. Again, Prof, Dana states that I make the crystalline schists
of the White Mountains a newer series than the Green Mountain rocks. A
careful perusal of my address will show that I nowhere assert that the rocks of
the third series, on my line of section, are younger than the second series.
Such a view of their relations has, however, been maintained for the last
generation by the Messrs. Rogers, Logan, and many others, all of whom
assigned the crystalline schists of the White Mountains to a higher geological
horizon than the Green Mountains. .. . . My ‘chronological arrangement’ of

VERMONT AND WESTERN MASSACHUSETTS. 449

New England crystalline rocks, as it is called by Professor Dana, so far as it is
my own, is limited to my affirmation that they are all of pre-Cambrian age.
.... As regards the mica-schists with staurolite, cyanite, andalusite and
garnet, I have in my address pointed out the fact that they appear to belong to
a great series of rocks, very constant in character, which have a continuous
outcrop from the Hudson River to the St. John, a distance of 500 miles, and,
in the latter region are clearly pre-Cambrian. I have, moreover, brought to-
gether the evidence of observers in other parts of North America, in Great
Britain, in continental Europe, and in Australia, showing that similar crystal-
line schists, holding these same minerals, always occupy, in these regions,
a similar geological horizon. Prof. Dana hereupon inquires whether any
one has yet proved that these mineral characters are restricted to rocks of a
certain geological period. I answer, that in opposition to these facts, it has
not yet been proved that they belong to any later geological period than the
one already indicated ; and that it is only by bringing together observations,
as [have done, that we can ever hope to determine the geological value of
these mineral fossils.”

Regarding the existence of staurolite, etc., as a criterion of geologi-
cal age, Dr. Hunt wrote, in 1878 :—

“Tt is by a misconception that some have been led to regard the presence of
staurolite, cyanite and andalusite, as exclusively characteristic of the Montal-
ban, a proposition nowhere maintained by the writer, since, although they
have not been found in the oldest terranes, these mineral species have long
been known to occur, in many localities, in the Taconian schists.” (Azoic
Rocks, p. 211.)

We do not understand what Dr. Hunt did mean, in 1872, in his
remarks given above, unless he intended to hold that staurolite, cyanite,
and andalusite were characteristic of Montalban schists ; neither does it
seem to us that any other construction is possible. It is to be further
noticed that, in his reply to Professor Dana above quoted, Dr. Hunt
emphatically denied the correctness of Professor Dana’s statement, that
he (Hunt) made in his Address the “ White Mountains (Montalban)
a newer series than the Green Mountain rocks” (Huronian). It does
not appear to have occurred to Professor Dana that this denial was
not made in good faith by Dr. Hunt, since he (Dana) replied as fol-
lows :—

“Mr. Hunt denies that he makes, in his Address, ‘ the crystalline schists of
the White Mountains a newer series than the Green Mountain rocks’ —I had
read on pages 29 and 33 of the Address approving announcements that Mac-
farlane had made the crystalline rocks of the Green Mountains Huronian ;
and then, on page 34 of the Address, the statement that the White Mountain

series is largely developed in Newfoundland, and that this fact had led him
VOL. vit —No. 11. ; 29

450 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

(Mr. Hunt) to propose for it [the year before] the name of the Terranovan
System. At this point in the Address there is a reference to this Journal of
the preceding year, Vol. L, p. 87, 1870; and consequently by referring back
to this article by Mr. Hunt, I found this Terranovan defined, Mr. Hunt saying
that, according to Mr. Murray, the series comprises ‘several thousand feet of
strata, including soft bluish gray mica slates and micaceous limestones belong-
ing to the Potsdam group, besides a great mass of whitish granitoid mica slates
whose relation to the Potsdam is still uncertain.’ As the Huronian is older
than the Potsdam, and this equivalency of the Terranovan is not corrected in
the Address, I thought I had reason for supposing that Mr. Hunt made the
White Mountain series the newer. I acknowledge I prefer the view he now
presents, since the less definite the statement the better as long as we have no
sufficient facts for a conclusion.” (Am. Jour. Sci., 1872, (3) IV., p. 105.)

Our extracts taken from Dr. Hunt’s Address * show, however, that
he did make the White Mountain series younger than the Green Moun-
tain series, and that Professor Dana was correct. Furthermore, it will
be shown that Dr. Hunt had advocated this view some time previous to
his delivery of the Address; and that later he claimed to have advo-
cated this order of age at the time of the Address and previously. The
reader’s attention is also called to the fact that in Dr. Hunt’s Chemical
and Geological Essays (p. 326) the sentence, “ A careful perusal of my
address will show that I nowhere assert that the rocks of the third
series (Montalban), on my line of section, are younger than the second
series ” (Huronian), is expunged, although the paper purports to be a
reprint of his reply to Professor Dana.

It is possible that the reader will find the reason for this expurgation
in what follows. On May 1, 1871, some three and a half months be-
fore the Address was given, Dr. Hunt said : —

“Tn a communication to the Boston Natural History Society on the 19th of
October last, and subsequently in the American Journal of Science for February
and March, 1871 (pages 84 and 182), I have expressed the opinion that the
porphyries . . . . are stratified rocks, belonging . . . . to the Huronian sys-
tem, or Green Mountain system. ... . I have in that same journal for July,
1870, pointed out the fact that the Eozoén of Hastings county, Ontario, occurs
ina series of crystalline schists which I consider newer than the Huronian,
and the equivalent of the White Mountain gneisses and mica schists.” (Bull.
Essex Institute, 1871, III., pp. 53, 54.)

Dr. Hunt’s remarks, published in the Proceedings of the Boston
Society of Natural History to which he above refers, are as follows :—
“T regard these two types of rocks (quartzo-feldspathic rocks and dioritic

* See ante, p. 447.

VERMONT AND WESTERN MASSACHUSETTS. . 457

and chloritie rocks) as forming parts of one ancient crystalline series, which is
largely developed in the vicinity of Boston, and may be traced at intervals
from Newport to the Bay of Fundy, and beyond. To this same series I refer
the great range of gneissic and dioritic rocks with serpentines, chloritic, talcose
and epidotic schists which stretches through western New England.” (J. c.,
October 19, 1870, XIV., p. 46.)

The references to the American Journal are to a paper stated to have
been read before the American Association, August 20, 1870, a year
before the Presidential Address, and which was published in the
Canadian Naturalist some eight months before that address was de-

livered.
He says, in the first reference to the rocks above referred to in the

Proceedings of the Boston Society :—

“They apparently belong .... to the great Huronian series.” (Am.
Jour. Sci., February, 1871, (3) I., p. 84.)

The second reference reads as follows : —

“The rocks of this White Mountain series are, in the present state of our
knowledge, supposed to be newer than the Huronian system .. . ., to which,
with Macfarlane and Credner, I refer the crystalline schists with associated
serpentines and diorites of the Green Mountains.” (Am. Jour. Sci. 1871
(3) I., p. 182 ; Chemical Essays, p. 194; Canadian Naturalist, 1870, (2) V.,
p. 396.)

In Dr, Hunt’s Azoic Rocks (pp. 222-224) is given part of a letter to
Major T. B. Brooks, under date of February 22, 1871, nearly five
months before the Indianapolis address. Since this letter is given in
full in the Geology of Wisconsin, Vol. III., 1879, pp. 657-660, we pre-
fer to take our extracts from that : —

“You remark about the mica-schists as being supposed by me wanting in
the Huronian of Canada, and you send me Nos. 1215, 1154, 1152, 1153. Now
I have for some time past recognized a mica-schist series which I supposed to
overlie the Huronian, in fact the White Mountain series, provisionally named
by me Terranovan [and since called Montalban]. See Am. Jour., July, 1870.
I was therefore delighted to find in the specimens named well-characterized
White Mountain mica-schists, holding garnets and well defined crystals of
Staurolite [1153]; while the peculiarly knotted mica schist is not less charac-
teristic. These rocks are abundantly spread to the north of Lake Superior, as
last year’s collection show me ; but although I have not there been able to fix
their relation to the Huronian diorites, talcose schists, iron ores, etc., I con-
clude, from the facts seen near Portland in Maine, and those described by
Rogers in Penn., they are overlying rocks, and in some cases at least un-
conformably so. You say that ‘they are the youngest rocks in the region

452 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

belonging to the Huronian.’ I suspect that they belong to the same series. I
distinguish three crystalline gneissic series : I. Laurentian (not to speak for
the present of the Labrador), Il. Huronian, III. Terranovan [Montalban] ;
these being respectively in the United States, the rocks of the Adirondacks,
the Green Mountains and the White-Mountains. I hope you will be able to
decide whether there is any want of conformity between II and III in your
region. I should mention that in Hastings Co., Ontario, the three series all
are represented, and that there is apparently a stratigraphical break between
edelin’.. ites As regards series II, which was in 1862 declared by Macfar-
lane to be the same with the Green Mt. group, I have for some time been
of that opinion, and have briefly expressed it in a paper on the rocks of
E. Mass., read last October to the Bost. Nat. Hist. Soc. (not yet published),
which compares the dioritic, chloritic and hornblendie rocks of the two
series. Their copper, nickel and iron ores are characters in common. My
opportunities for studying the Huronian had been very imperfect, as Mr.
Murray’s collections were so, and were made many years ago, and since re-
main, with few exceptions, packed away. It was not, therefore, till I saw the
Huronian rocks displayed along the coast of New Brunswick, that I realized
how much they were like the Green Mt. rocks, all of the types of which may
be found on the Bay of Fundy from Eastport to the head of the bay... . .
I have thus, I think, touched on the principal points of interest in your collec-
tion, of which the two great facts are the close resemblance, and I believe the
identity, of the great iron-bearing dioritic-talcose series, with Green Mt. series
II, and the equally close resemblance of the rocks, 1215, 1151 to 1154, with the
White Mt. series III, which I conceive to belong to a higher horizon (see on
this a note to my paper on granitic rocks, 2d part, Am. Jour. Sci. for March).”

While in the above letter it is written : ‘“ You say ‘that they are the
youngest rocks in the region belonging to the Huronian.’ I suspect
that they belong to the same series,” — in the ‘ Azoic Rocks,” it reads :
“You say that they are the youngest rocks in the region belonging to the
Huronian. 1 suspect that they belong to a younger series.” (1. ¢.,
p. 223.)

Another letter by Dr. Hunt of the date of May 20, 1878 (Geology of
Wisconsin, III., 1879, p. 660), contains the following :—

“The announcements made in my letter to you identifying the formations
XIX and XX (the micaceous schists, with hornblendie and staurolitic schists
and the white feldspathic gneisses) with the Montalban, which I at that time
(1871) ventured to declare to belong to a newer and distinct series from the
Huronian, were, as you know, an anticipation of some years of the published
conclusions of yours that they are the youngest Huronian rocks, a strong con-
firmation of the great value of the distinctions, which in my letter to you of
February 22, 1871, were presented for the first time.. All my subsequent work
in Pennsylvania (Proc. Amer. Assoc. 1876) and in North Carolina, as well as

VERMONT AND WESTERN MASSACHUSETTS. 453

Fontane’s work in Virginia, have confirmed this. I count this a great point
gained in American stratigraphy — the recognition of the newer gneissic series
above the Huronian, to which I have given the name of Montalban. (The
Terranovan suggested in 1870, was made up of Montalban and Taconian, as I
have since shown.)”

Later, in the Azoic Rocks (pp. 224, 225), Dr. Hunt, in referring to
the first letter given above, says : —

“ The above conclusions as to this overlying gneiss and mica-schist series,
was soon after made known by the writer, in his address in August, 1871,
where it was said that the schists both of the Green Mountain and the White
Mountain series ‘ are represented in Michigan, as appears by the recent collec-
tions of Major Brooks. ... . He informs me that these latter schists are the
highest of the crystalline strata in the northern peninsula. ... . It was these
schists, and the granitoid gneisses, from the Marquette region, which the
writer [Dr. Hunt] so long ago as 1871, referred to the White Mountain or
Montalban series, then, as now, placed by him above the Huronian —a testi-
mony to the value of lithological characters in geology.”

We thus see that Dr. Hunt had for over eighteen months advocated
the view which he so emphatically denied having held ; and further-
more, that after the delivery of his Presidential Address he claimed to
have held it at that time. Also, we have shown that he distinctly
stated the same view in that Address. But it is unnecessary for us to
comment on the methods of Dr. Hunt as revealed in the preceding ex-
tracts ; they speak loudly for themselves.

Professor Dana, in reference to Dr. Hunt’s views regarding the age of
rocks carrying crystals of staurolite, cyanite, or andalusite, remarked as
follows : —

“Now the fact is that those same Taconic rocks, unquestionably of the
Taconic system according to Emmons himself, and, therefore, Hunt attesting,

of Lower Silurian age, contain in some places staurolite erystals.” (Am. Jour.
Sci., 1872, (3) IV., pp. 104, 105.)

Also, in the same paper, Professor Dana thus replied to Dr. Hunt’s
remark, that Emmons expressly excluded from the Taconic system all
crystalline rocks :—

“This exclusion is an easy feat for a speculator with pen in hand, like many
closet feats; but it is more than herculean in actual fact, since the very
Taconic mountains themselves, that is, the very rocks called Taconic by
Emmons, are partly gneiss, gneissoid mica schist, and chloritic taleoid schist,
as well as talcoid schist ; and these rocks are so involved together that specu-
lation will never bring them into that kind of order which Mr. Hunt’s notions
require.” (J. c., p. 104.)

454 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

In a criticism on the Chemical and Geological Essays of Dr. Hunt,
Professor Dana further states (Am. Jour. Sci., 1875, (3) IX., pp. 102,
103) :—

“The reader of the volume will observe that in the Third Chapter the
White Mountain series and Green Mountain series of rocks are made (as had
been done by other geologists) Lower Silurian, and Upper Silurian and Devo-
nian, in age, while in the Thirteenth Chapter (as also mentioned in the preface
to Chapter III) both are pronounced pre-Silurian. In this, the older view, as
I believe I have proved, is the one sustained by the facts. The new view is
wholly speculative, being based on no careful stratigraphical study of the
regions, but mainly upon the assumption that certain kinds of crystalline
rocks are a test of geological age the world over. Since the first announcement
of this doctrine by Mr. Hunt, I have spent many months in the study of the
Green Mountain rocks and those of some other parts of New England, in order
to ascertain whether there is any virtue in the criterion; and I have found
none. Mr. Hunt makes staurolite evidence of pre-Silurian age ; while, as I
have shown, its crystals occur in crystalline rocks of New England that are
not older than Upper Silurian. Such erroneous conclusions make it apparent
that in reading the work the judgment should be held in reserve until the
other side is heard. There is also another more serious reason for this reserve.
For the volume contains a series of misrepresentations of the views of others
wholly unnecessary to the presentation of the author’s opinions, and difficult
to find excuse for.”

Professor Dana, in 1873, after discussing the observations of himself
and others, remarks : —

“From the facts which have been presented it follows that all old-looking
Green Mountain gneisses are not pre-silurian, and, further, that the presence
of staurolite is no evidence of a pre-silurian age. . . . . It is not easy to avoid
the conclusion that the Taconic slates are Hudson river slates. . . . . The Tren-
ton limestone and Hudson River or Cincinnati groups, which properly con-
stitute one series in American Geological History, are then the true Taconic
system.” (Proc. Am. Assoc. Adv. Sci., 1873, XXII. B., pp. 25-29 ; Ameri-
can Naturalist, 1873, VII., pp. 658-660).

Professor Dana, in giving an account of an examination of the Hel-
derberg rocks in the valley of the Connecticut (Am. Jour. Sci., 1873,
(3) VI., p. 348), concludes that staurolite and andalusite occur in meta-
morphic rocks of any age, remarking that
“this Helderberg series in Central New England comprises a large part of the
common kinds of metamorphic rocks, gneiss of several varieties, undistin-
guishable lithologically from the oldest ; hornblende rock and schist ; syenite

gneiss ; coarse mica schist and mica slate ; staurolitic slate.
“A large part of the rocks that have been distinguished as of the ‘ Mont-

VERMONT AND WESTERN MASSACHUSETTS. 455

alban’ or ‘White Mountain series’ in New Hampshire, and regarded of pre-
Silurian age, are here included, and are hence nothing but altered Helderberg
sediments. It is hence far from true that ‘ the crystalline rocks of the Green
Mountain and White Mountain series’ and ‘ the whole of our crystalline schists
of Eastern North America are not only pre-Silurian, but pre-Cambrian in age.’”

In the same article (p. 341) Professor Dana further remarks : —

“ Lithological evidence of a geological age among metamorphic rocks of dis-
tant regions is in general worse than worthless. It is easy to use, and presses
itself on the mind most insinuatingly when a conclusion is eagerly wanted.
.... I have further found that the Earth did not finish up its metamorphic
work in pre-Silurian time, or even by the epoch closing the Primordial, as it
did not its mountain-making.”

For the field evidence upon which Professor Dana founded his con-
clusions, the reader is referred to the original article.

In the Report of Progress of the Canada Geological Survey, for the
year 1873-74, Mr. Selwyn remarks that considerable doubt and uncer-
tainty have been thrown upon the labors of Sir William Logan by arti-
cles from the pen of Dr. Hunt. These articles appear to the present
head of the Canada Survey to indicate that the earlier views of Dr.
Hunt in regard to the true stratigraphical positions of the rocks in
Eastern Canada had undergone an almost entire revolution. This
change of opinion is said by Mr. Selwyn to have been based, so far as
he could understand it, on lithological comparisons exclusively, and he
thus expresses his views in regard to that kind of evidence : —

“ Whether the relative ages of great masses of crumpled and metamorphic
strata can be thus determined apart from, or in the absence of paleontological
and stratigraphical evidence, is a question which, as a stratigraphist of thirty
years’ experience, I should decidedly answer in the negative. The degree and
character of the metamorphism and mineralization which a group of strata
exhibit, cannot be relied on as certainly indicative of geological antiquity, and,
as tending to strengthen this opinion, the recent researches of Mr. Richardson
in British Columbia have shown that epidotic, chloritic and serpentinous rocks,
with crystalline limestones and magnetites, are as characteristic of upper pale-
ozoic, and perhaps also of even later formations when they have been subjected
to an equal amount of plication and folding, as they are of the oldest paleozoic
and protozoic strata, such as those of Eastern Canada and the New England
States.”

In 1875 Prof. J. P. Lesley stated that in Pennsylvania the Huronian
or Green Mountain series was seen to overlie the White Mountain
series ; while he unqualifiedly placed both series in Vermont and New
Hampshire below the Potsdam. (Second Geological Survey of Pennsyl-
vania, D., pp. 65, 66.)

456 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Professor Dana, in a review of Professor Lesley’s remarks, says (Am.
Jour. Sci., 1876, (3) XL, pp. 63, 64) :—

“ Mr. Lesley goes outside of his field in his closing remarks, and states —
what is sustained as yet by no adequate stratigraphical evidence — that the
‘Green Mountain system of Vermont’ and the ‘White Mountain system of
New Hampshire,’ are, like ‘the Laurentian Mountains of Canada,’ older than
the Potsdam; and that the Green Mountain system, one of these ‘three great
mountain systems of the north,’ is Huronian. The observations by Mr. Prime
in Pennsylvania, above mentioned, and the parallel facts in the Green Moun-
tain system to which he draws attention, all point as regards the Green Moun-
tains in the opposite direction. The writer has studied stratigraphically the
Green Mountain region from Connecticut to Vermont, and has found that the
hydro-mica and chloritic hydro-mica slates associated with the limonite beds of
Berkshire are of the same formation with the hydro-mica, chloritic, and mica-
ceous slates of Graylock and the Taconic range; and with the hydro-mica
slates of the ridge lying northeast of Rutland in Vermont, and of others west
and north of Rutland; and with the staurolitic schists of the limonite region
of Salisbury, Connecticut. Since the limestones associated with the slates of
West Rutland abound in distinct Lower Silurian fossils, referred to the Chazy
by Billings, part of the Green Mountain slates and schists are unquestionably
Lower Silurian. What is the age of the rest is not yet positively known.”

In 1878 Professor Dana remarks : —

“Professor Lesley stated in his letter * that the opinions which he had
derived, from the observations of others, more than thirty years since with
regard to New England geology, he now (since the discovery of fossils in lime-
stones among the metamorphic rocks of Vermont, of Bernardston and Littleton
in the Connecticut Valley, and of Eastern Pennsylvania) regards as greatly
strengthened in probability —namely : That Paleozoic rocks make up the
Green Mountains, and also the White Mountains, and that the latter include
beds of Devonian age.” (Am. Jour. Sci., 1878, (3) XV., p. 261.)

This then is a virtual retraction by Professor Lesley of his statement
in 1875 (given before), that the Green and White Mountains were pre-
Potsdam in age.

Professor Dana made the following statement as the result of
an extended series of observationst by himself and Rey. Augustus

* A letter to Professor Dana, giving an account of the discovery by Mr. Prime
of Lower Silurian fossils associated with mica slates in Eastern Pennsylvania.

+ For Professor Dana’s various papers on this subject, see Am. Jour. Sci., 1872,
(3) IIL, pp. 179-186, 250-256; IV., pp. 133, 362-870, 450-453 ; V., pp. 47-53,
84-91 ; VI., pp. 257-279; 1877, XIII., pp. 332-347, 405-419 ; XIV., pp. 86-48,
132-140, 202-207, 257-264; 1879, XVII., pp. 375-388; XVIII., 61-64; 1880,
XIX., pp. 191-200. See also Dwight, Am. Jour. Sci., XVII., pp. 389-392 ; 1880,
XIX., pp. 50-54.

VERMONT AND WESTERN MASSACHUSETTS. 457

Wing (Am. Jour. Sci., 1877, (3) XIV., pp. 202, 203; 1879, XVII.,
p. 387) :—

“From the facts brought forward it is manifest that the limestone schists
an quartzyte, making up the limestone series of Vermont and Berkshire, are
continuous formations, and that they are conformable throughout... . . The
limestone series is made up wholly of Lower Silurian formations ; that is, of
formations not older than the primordial or Cambrian, nor newer than the
Cincinnati or Hudson River group. .... The Taconic mountains of western
Berkshire are a direct continuation of the ‘great central slate-belt’ of Ver-
mont. The two make one range and one rock-formation, and consist of the
same kinds of rocks similarly upturned. ... . In Vermont the Taconic slates
(those of the central slate-belt) overlie the adjoining limestone in one or more
synclinals, as plainly shown in Mount Dorset, Danby Mountain, Equinox
Mountain, Spruce Peak in Arlington, and Mount Anthony in Bennington ;
and in Berkshire they have the same position, as observed in Greylock and
Mount Washington. Hence in both States the Taconic slates overlie, or are
younger than, the adjoining limestone... . . The Taconic schists are, according
to the evidence, of the age of the Hudson River group.”

The limestones and micaceous quartzites of Berkshire County, Mass.,
and elsewhere in New England, were stated by Dr. Hunt, in 1875, to
belong to the White Mountain or Montalban series. (Proc. Bost. Soc.
Nat. Hist., 1875, XVII., p. 509.)

In 1878 Dr. Hunt remarked (Preface, Chemical Essays, 2d ed.,
pp. xix.—xxii.) that the result of his study of the Taconic rocks had
led him

“to conclude that what has been said of them in Essay XIII. Part 1, and in
Essay XV. Part 3, is only true of that portion which Emmons at first in-
cluded in the upper part of his Taconic system under the general name of the
Taconic slates, but in 1855 separated from the underlying portions, and de-
scribed as the Upper Taconic series. This is no other than the Quebec group
of Logan, which is the northward prolongation of the Taconic slates from
eastern New York. .... The strata of this region, and of its extension
north and south, including the western border of the whole Atlantic belt,
from the gulf of St. Lawrence to Alabama, have, as is well known, a general
high dip to the eastward, attended with many dislocations, folds, and inver-
sions ; as a result of which the newer sediments appear to pass beneath the
older ones, and even beneath the still more ancient crystalline rocks of the
belt, geving rise to some of the most perplexing problems in American geology.
The fauna of the Upper Taconic rocks, including the forms found at Troy,
New York, at Georgia, Vermont, and at Phillipsburg, Point Levis, and Bic,
in the province of Quebec, presents, as far as known, nothing lower than
the Menevian horizon, and belongs to the Lower and Middle Cambrian of
Sedgwick. .... The lower Taconic series of Emmons, embracing in ascend-

458 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ing order (1) granular quartz rock, (2) the Stockbridge limestone with its
interstratified and overlying micaceous schists, and (3) argillites, including roof-
ing slates, constitutes a distinct geological horizon of rocks essentially crystal-
line, having an aggregate thickness of about five thousand feet. These are
found resting alike on Laurentian, Huronian, and Montalban strata, and are
overlaid, probably unconformably, by the Cambrian (Upper Taconic). . :
They are apparently identical with the great limestone series which, in Hee.
tings county, Ontario, underlies unconformably the Trenton group of lime-
stones, and near St. John, New Brunswick, is beneath the Menevian slates.”

During the same year the Taconian series was said by Dr. Hunt to
include the statuary marbles of North. America, and to be overlain
“by the Upper Taconic, which is identical with the Quebec Group of
Logan.” (Nature, 1878, XVIII., p. 444; Geol. Mag., 1878, (2) V.,
p. 471.)

In 1879, Dr. Hunt gives us to understand that in 1863, when he
referred the Green Mountain rocks to the Quebec Group, in the ‘“ Ge-
ology of Canada,” he then regarded them as Huronian, but that “ oficial
reasons then, and for some years after, prevented the writer from expressing
any dissent from the views of the director of the geological survey of
Canada.” (Proc. Am. Assoc. Adv. Sci., 1879, XXVIII., p. 285; Am.
Jour. Sci., 1880, (3) XIX., p. 273.)

It would seem from the remarks we have quoted from his papers *
that the “ official reasons” not only prevented his dissenting from Sir
William Logan’s views, but also caused him to affirm their correctness
in the strongest possible manner. And in connection with this state-
ment of Dr. Hunt’s, it will be well to refer to one which follows, made
by him in 1871 :—

“My opportunities for studying the Huronian had been very imperfect.

. It was not, therefore, till I saw the Huronian rocks displayed along the
coast of New Brunswick (1869-70), that I realized how much they were like
the Green Mt. rocks.” (Geol. of Wisc., 1880, III., p. 658.)

How again does Dr. Hunt’s statement made in 1879 agree with that
of 1875, in which reference is made to a paper read in 1863 advocating
the palaozoic age of the rocks of the Green and White Mountains?
The statement made in 1875 reads as follows : —

“ My own extended studies of these rocks in the Green Mountains, in New
Brunswick, and on Lakes Superior and Huron, have since convinced me that

this view is correct, and that the Green Mountain series is represented in the
crystalline strata around the great lakes just mentioned ; and, moreover, that

* See ante, pp. 441-445.

VERMONT AND WESTERN MASSACHUSETTS. 459

both this series and the crystalline rocks of the fourth or White Mountain
series existed in their present crystalline form before the deposition of the
eldest Cambrian sediments.”* (Chem. and Geol. Essays, p. 18.)

The following statement, made by Dr. Hunt in 1873, contains his
own acknowledgment that he maintained, until 1870, views he would
now have us understand he had not believed in since 1863.

“The question of the structure and origin of the Appalachians has been
complicated by the assumption that the crystalline strata which constitute
their higher portions are altered sediments of paleozoic age, rather than parts
of an ancient continent of eozoic rocks which formed the eastern border of the
paleozoic sea, corresponding to the Rocky Mountains on the west. The former
view has been very generally held by American geologists, and was maintained
by the present writer until 1870, when he endeavored to show that the crystal-
line rocks of New England and their lithological representatives both to the
southwest and the northwest are of pre-paleozoic age and in part Laurentian.
[This Journal, I]. L,83.... ].” (Am. Jour. Sci., 1873, (8) V., pp. 267,
268.)

The question arises, whether the geologist, who is desirous of finding
out what Dr. Hunt’s real views on any subject may be at the present
time, or may have been at any time in the past, can feel any confidence
that he is likely to arrive at a satisfactory result. At all events, it has
been shown above that official or other conditions may be to Dr. Hunt a
sufficient reason, not only for withholding his own views, but for strongly
advocating that in which he himself has no belief.

In 1880 Professor Dana held that the Green Mountains were formed
at the close of the Lower Silurian, and sums up the evidence on this
point as follows (Am. Jour. Sci., 1880, (3) XIX., p. 200) :—

“1. The western half of the region between the Connecticut River valley
and the Hudson River, that is, the western half of the Green Mountain area,
is proved to consist of rocks that are (1) of Lower Silurian age and (2) of one
orological system.

“2. The schistose rocks of the eastern half in Vermont are to a large extent
similar to those of the western.

3. The rocks of the central mountain section in Vermont are, in its north-
ern part, identical schists (hydromica, etc.), with those on the east and west
sides of it.

‘4. The western border of the region in the Hudson River valley has its
folded or upturned Hudson River (Lower Silurian) slates, overlaid unconform-
ably by Niagara and Lower Helderberg (Upper Silurian) beds.

“The eastern border of the region in the Connecticut valley at Bernardston,
in Massachusetts, Vernon in Vermont, and the adjoining part of New Hamp-

* The italics are ours.

460 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

shire, has lower Helderberg beds overlying, unconformably, folded or upturned
roofing slates (similar to those on the western side), the Lower Silurian age of
which is not improbable ; and at Littleton in New Hampshire, and on Lake
Memphremagog, in northern Vermont, occur unconformable Upper Helder-
berg (Lower Devonian) beds with fossils... . . In view of these various con-
siderations, the evidence, although not yet beyond question, is manifestly
strong for embracing the whole region between the Connecticut and the Hud-
son (and to an unascertained distance beyond) within the limits of the Green
Mountain synclinorium.”

Professor Dana makes this statement in reference to a letter sent him
by Prof. C. H. Hitchcock (Am. Jour. Sci., 1880, (3) XIX., p. 237) :—

“Prof. Hitchcock also says, in the recent letter to me, after remarking on
his disbelief in ‘Taconism’: ‘ Within the past two years I have gone over
most of the Vermont sections, and have felt that they demonstrated the essen-
tial equivalence of the Taconic system with the Potsdam and the overlying
limestones and slates [of the Lower Silurian]. I have been throughout in
essential accord with you and Mr. Wing.’ He adds that Mr. Wing’s views had
been his for years.”

Professor Hitchcock is further quoted as saying regarding the Report
on the Geology of Vermont (1861), ‘‘ There is nothing in the Report
anywhere favorable to ‘ Taconism.’ ”

In 1877 Professor Hitchcock gave his ideas of the Green Mountain

or Quebec rocks as follows :—

“Sir W. E. Logan has described them under the general name of Quebec
OPOUP s/s He has grouped together a large series of fossiliferous Cambrian
and metamorphic rocks, assuming that the one was the equivalent of the
other. I have endeavored to separate the fossiliferous from the metamorphic
portions, with the assistance of Dr. T, Sterry Hunt... .. From this series,
as proposed by Logan, we must eliminate all the fossiliferous portions and in-
vert the order... .. This is in agreement with the recently quoted view of
Mr. Macfarlane, and has been also insisted upon by Dr. Hunt. Separating
the eastern part of the area called Quebec group by Logan, we may clearly
understand it to be older than the fossiliferous Cambrian of any part of the
world, and therefore to be named Huronian. .... The Vermont Huronian,
save that along Connecticut river, is the southward continuation of the Quebec
croup of Canada. It is divided into two parts by the central ridge of the
Green Mountains, which continues a few miles into Canada. Macfarlane fol-
lows the report on the geology of Vermont in regarding the Green Mountain
ranges as older than the adjacent Upper Huronian. We have in that early
publication (1861) insisted that these Green Mountain rocks underlaid the
green schists upon both sides, . . . . and they are consequently older. The
name Green Mountain gneiss, as applicable to this formation, was in use in

VERMONT AND WESTERN MASSACHUSETTS. 461

1846; and therefore the use of the same geographical designation by Dr.
Hunt, in 1871, for the Huronian, is both inappropriate and improper, on ac-
count of prior usage. The Green Mountains are not Huronian at all, though
flanked by it upon both sides in the northern half of Vermont. They belong
to the Montalban series. Adopting the principle of inversion, as applied to
the members of the Quebec group, we find they overlie these Montalban
gneisses in the proper order of succession. As Macfarlan says, those who once
accepted the theory of the metamorphism of New England seem to retain
erroneous notions of the age of the successive mountain ranges, calling the
Green Mountains newer than the Adirondacks, and the White more recent
than the Green. They are both nearer the Laurentian than the Huronian, in
respect to age.” (Geol. of N. H., 1877, IL., pp. 463, 464 ; see also pp. 10, 11,
25-27, 31.)

In 1875 he said : —

“ His observations led him to believe that Emmons understood the strati-
graphical relations of these rocks (many of them called Taconic by him) better
than most of his contemporaries.” (See Proc. Bost. Soc. Nat. Hist., 1875,
XVIIL., pp. 191-193.)

Professor Dana in a series of papers bearing the title of “On the Geo-
logical Relations of the Limestone Belts of Westchester County, New
York,” (Am. Jour. Sci., 1880, (3) XX., pp. 21-32, 194-220, 359-375,
450-456; 1881, XXL. pp. 425-443; XXIL., pp. 103-119,) has brought
together the evidence bearing on the question of the geological age of
the Green Mountain limestones and associated rocks. He remarks as
follows :—

** As the fossils of the limestone had been discovered only in Vermont, it was
required, in order to extend the conclusions to the rest of the Green Mountain
region, that the Vermont limestone should be proved to be the same strati-
graphically with that of the region to the south, and this was done by ascer-
taining (1) the essential continuity of the limestone from the north to the south
and south-southwest ; and (2) its association with similar rocks from north to
south, under similar stratigraphical relations; and finally (3), by the discoy-
ery of Lower Silurian fossils in the part of these belts of limestone that reach
into and beyond Dutchess County, and also in the associated Taconic schists of
that County. By these means, it has been shown that the schists of the
Taconic range, the limestone belts on either side, and various conformable
schistose rocks and limestone belts farther east and west, are comprised within
the Lower Silurian formation, and that the whole series was displaced together
in the upturning and metamorphism by which the Green Mountains were
made.” (Am. Jour. Sci., 1880, (3) XX., p. 22.

Professor Dana comes to the conclusion, that the limestone of West-
chester County and. New York Island, and the conformably associated

462 THE AZOIC SYSTEM AND JTS SUBDIVISIONS.

metamorphic rocks, are of Lower Silurian age ; also, that the limestone
and the conformably associated rocks of the Green Mountain region,
from Vermont to New York Island, are of the same age. He remarks
furthermore :—

“These Westchester County rocks have been pronounced Montalban. I
know of no facts sustaining such a conclusion. If true, it would follow, from
the above, that the original Montalban rocks — those of the White Moun-
tains — also are Lower Silurian.” (Am. Jour. Sci., 1880, (3) XX., p. 455.)

Of the correctness of these statements in regard to the Lower Silu-
rian age of the rocks in question, it seems to us that there can be no
possible doubt.

NEW YORK.

The mass of the Adirondack Mountains is composed, in large part, of
highly crystalline rocks, among which that called ‘‘ hypersthene rock ”
by Professor Emmons is the most conspicuous and important, forming
as it does the highest portion of the chain, and covering, according to
the same authority, the whole of Essex County. Gneiss, granite, and
syenite are also present over areas of some extent, while mica schist
and tale schist are said to be entirely wanting. The extent and impor-
tance of the masses or beds of magnetic and specular oxides of iron are
also well known. In Professor Emmons’s classification of the Adirondack
formation, gneiss and syenite are put down as being stratified, while the
limestone is considered as being unquestionably of eruptive origin.

The Adirondack area is admitted by geologists — without exception,
it is believed — to be Azoic, or Archean. In view of what has been
stated in the preceding pages with regard to the facility with which the
Azoic rocks of other regions in this county have been assigned to be
Laurentian, Huronian, or Montalban, or moved backwards and forwards
between these three supposed systems to suit the fancy of the theorist,
it seems rather remarkable that the rocks of Northern New York should
have been so little meddled with in this way. Our knowledge of the
geology of the Adirondack region is so exceedingly incomplete, that a
fine field lies ready there for theoretical speculations of a kind simi-
lar to those which we have shown to have been so prevalent in regard
to the rocks of New England. A brief statement will here be given of

NEW YORK. 463

what has been published bearing on the question of the division of the
Adirondack rocks into two or more systems, first calling the reader’s
attention, however, to the fact that no one of the theoretical views
advanced has been supported by sufficient evidence to make its adop-
tion a necessity.

In 1864, Messrs, Hall and Logan announced, in a paper read before
the Natural History Society of Montreal, (Canadian Naturalist, 1864,
(2) I., pp. 368, 369; Am. Jour. Sci., 1865, (2) XXXIX., pp. 96, 97,)
that the gneiss of the New York Highlands “ presentéd all the aspects
and characteristics of that of the Laurentian system, as seen in North-
ern New York and in Canada.” Here it is assumed, as a matter of
course, that the Adirondack region is Laurentian.

Nothing further appears to have been done until Mr. A. M. Edwards
announced, in 1870, the discovery of Hozoéx Canadense in serpentinous
marble from Warren County, N. Y., this indicating, according to him,
the Laurentian age of that rock. (Proc. Lyceum Nat. Hist. New York,
1870, pp. 96-98.)

Later, in 1876, Professor James Hall, in a paper entitled “ Note
upon the Geological Position of the Serpentine Limestone of Northern
New York, and an Inquiry regarding the Relations of this Limestone to
the Eozoon Limestones of Canada,” (Am. Jour. Sci., 1876, (3) XIL,
pp. 298-300,) remarked of the Azoic area in question that the forma-
tions occupying that space, ‘ originally called Primary, and afterwards
Laurentian,” were now known to “ represent several geological periods.”
No proof of this is furnished; but it is further stated that there is a
lower division of the Laurentian, “succeeded by massive beds of labra-
dorite rock and other granite rocks.” The lower division is said to
consist of black hornblendic, gray garnetiferous, and coarse feldspathic
and quartzose gneisses, with extensive beds of magnetic iron ore. The
succession between this lower series and the upper one is said to be un-
conformable. In regard to this unconformability it is further stated
that “the interval between the two series of rocks is not determined,
nor does it appear to be determinable from examinations thus far made
within the State of New York.”

Professor Hall makes a third unconformable series out of the lime-
stone masses of that region, of which rock he says that it “‘ unconform-
ably overlies the upturned edges of the gneissic beds.” He also further
states that this limestone “ does not conform to the upper or labradorite
portion of the system.” Hence, he considers that the limestone iu
question “‘does not belong to the Laurentian system, either lower or

464 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

upper.” He concludes by suggesting the inquiry “ whether the Eozoon
limestones of Canada, which are associated with Laurentian rocks, and
have been referred to that age, are really Laurentian.”

Professor Hall’s idea of making a separate geological formation or
system out of the limestone masses of Northern New York, on account
of their unconformable position, is hardly less remarkable than that of
Professor Emmons, who considered that the peculiar occurrence of this
rock in the region in question could not be accounted for except on the
supposition that they were of eruptive origin. It seems to us, on the
other hand, that these limestone occurrences are, very probably, similar
in character to those of Eastern Massachusetts, which are not a part of
the stratified formation, but rather of the nature of segregated masses,
or chemical precipitates, as will be more fully set forth farther on in
this paper.

Prof. A. R. Leeds, in a paper entitled ‘‘ Notes upon the Lithology of
the Adirondacks,” concluded

“that the rocks of Essex County are part of the Norian System,” and “ that
these norites are a stratified rock, but have undergone a metamorphosis so
profound as to have caused them to be regarded by Prof. Emmons and earlier
observers as unstratified. The dolerites which are found of the same con-
stituent minerals, and are of the mean specific gravity of these norites, have
probably been formed from a portion of these stratified deposits by deeply
seated metamorphic action, and have further modified and greatly tilted the
superposed rocks in the course of their extrusion.” (American Chemist, 1877,
VII., p. 339.)

That these rocks belong to the Norian system was determined by
lithological evidence, which really means no more than this, that gab-
bros coming from different localities look somewhat alike. That the
rocks are stratified is, according to him, shown by the existence of a
more or less complete parallel arrangement of the constituent minerals.
Professor Leeds is a chemist, and not a petrographer; and since his
ideas are obviously simply a repetition of those of Dr. Hunt, his testi-
mony neither adds to nor detracts from the importance of the theoreti-
cal views of the latter.

Mr. N. L. Britton, in 1881, in an article on the geology of Richmond
County, N. Y., (Annals of the N. Y. Academy of Sciences, 1881, II.,
pp. 161-182,) advocates the view that the granite observed by him at
Tompkinsville is an Archean metamorphosed rock. This granite is
said by him to be “very coarsely crystalline in structure,” and no strati-
fication is observable in it. No proof is furnished that it is of meta-
morphic origin.

NEW JERSEY. 465

The serpentine, which forms so conspicuous a feature in the geology
of Staten Island, is thought by Mr. Britton to be a metamorphosed
magnesian limestone. The sections drawn to illustrate the geology of
the region show the serpentine always occurring as a sort of mantle
enveloping the gneiss. These sections, which seem to be a pure fiction
of the imagination so far as the relations of the serpentine and gneiss
are concerned, do not agree with the geology as laid down on the
accompanying map. Since, as is well known, a large part of the thor-
oughly-studied serpentines of the world have been proved to be the
result of the metamorphism“f eruptive masses, it seems more reason-
able to ascribe such an origin to the rock in the region under considera-
tion. At all events, the sections given do not favor the idea of such an
origin of the serpentine as is advocated by Mr. Britton ; nor is it by any
means proven that the belt of metamorphic rocks which runs through
Staten Island is, as he supposes, older than Lower Silurian.

NEW JERSEY.

In the Report of the earliest Geological Survey of New Jersey, by
Prof. H. D. Rogers, the gneissic belt which traverses that State from
northeast to southwest in its northern portion is called primitive, and
the crystalline limestones which accompany it are supposed to be the
result of an alteration of the Blue Limestone by the agency of dikes of
granite. The beds or masses of iron and zine ore, which characterize
the gneissic belt, are said to be “ unequivocally genuine lodes or veins.”
The later Survey, first under the direction of Dr. Kitchell, and later
under that of Professor Cook, agree in making the crystalline lime-
stones a portion of the gneissic formation. In regard to the iron ores,
Professor Cook states (Geology of New Jersey, 1868, p. 44) that the
majority of geologists now think them to be true beds, “which were
deposited as sediments, in the same way as the material for the gneiss
rock.”

By Professor Cook the whole system of rocks, including the gneiss
and crystalline limestones, together with the associated iron and zinc
deposits, are considered as belonging to the “ Azoic formation.” These
rocks are overlain, as represented in the published sections, by the

VOL. VII.— No. 11. 30

466 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Potsdam sandstone in unconformable sequence. It was found by Pro-
fessor Cook that it was not practicable to divide the Azoic of New
Jersey, or to make of it “ any other systematic classification than a geo-
graphical one.” It will therefore not be necessary for us, in this con-
nection, to dwell upon the geology of the lower rocks in this State.
Since, however, this admirably conducted Survey is still in progress, and
it will yet be possible to obtain from it valuable additions to our present
stock of knowledge of that region, it will be well to call attention to
certain points in regard to which evidence is still lacking to prove the
correctness of the common belief about them.

The relations of the different Azoic rocks to one another should be |
most carefully studied, in order to find out whether the supposed gneiss
is, as a whole or in part, sedimentary or eruptive, the laminated charac-
ter not being sufficient to prove its origin, lamination being a very com-
mon character in eruptive rocks. The contacts of the rocks require
very careful examination, as it is only in this way that it will be possible
to make out the relative age, and in most cases the origin, of the rocks
in question. Of the rocks, the first one in order of time should have
its origin determined by study of its intimate structure, and by compari-
son of it with similar rocks of known formation. It would be necessary
to remember that unconformability between the lamination or folia-
tion of an eruptive rock, and the stratification planes of a sedimentary”
one, means something very different from the unconformability of two
stratified deposits. Attention should be specially paid to the kind of
contact made by the supposed Azoic with the Paleozoic, and examina-
tion should be made to see whether the latter at its base is composed
of débris derived from the supposed Azoic. The one case in which the
material of a conglomerate is referred to the gneissic rocks is a doubt-
ful one, and, if correct, would only show that the gneiss is older than the
Oneida conglomerate. (Geology of New Jersey, 1868, pp. 335, 336.)

In the case of the iron ores associated with the Azoic, the evidence
given seems to be insufficient to prove the view either of their sedi-
mentary origin or of their eruptive character. Statements in regard to
the apparent conformable stratification and insensible passage of one
rock into another have been often made, and are easy to make; but
such statements require proof based on most careful observation, made
by thoroughly skilled petrographers, before they can be accepted as con-
clusive evidence in regard to the question at issue.

PENNSYLVANIA. 467

PENNSYLVANIA.

The views of Prof. H. D. Rogers, former State Geologist of Pennsyl-
yania, in regard to the lower formation in the region embraced within
his Survey, have already been briefly mentioned.* Two years later
than the date of the publication to which reference is there made — in
1858, namely —his Final Report appeared. In this Report, Professor
Rogers adheres, essentially, to the ideas maintained by himself in the
article in Johnson’s Physical Atlas. In the introductory chapter to Part I.
of the Final Report, under the heading of ‘‘ Classification of the Metamor-
phic Strata of the Atlantic Slope of the Middle and Southern States,”
he discusses certain questions which pertain to the subject of this
paper. He remarks, that, previous to the light thrown upon the older
rock formations of the Atlantic Slope by the Geological Surveys of Penn-
sylvania and Virginia, these rocks were supposed to constitute but one
group, and were included under the name of “ Primary,” and he then
proceeds to make the following statement : —

“ Karly, however, in the course of those surveys, it came to light that by far
the larger portion of the rocky masses of at least the middle and northwestern
tracts, including much of the Blue Ridge and of the Green Mountains, were of
a different type and age from the oldest metamorphic or true gneissic system.
The evidence in support of this conclusion was, first, an obvious and very gen-
eral difference in the composition of the two sets of strata ; secondly, a marked
difference in their conditions of metamorphism ; and thirdly, and more espe-
cially, a striking contrast in the direction and manner of their uplift, the pli-
cations and undulations of the less metamorphic series dipping almost invariably
southeastward, while the gneiss in many localities has no symmetrical foldings,
but only a broad outcrop dipping to a different quarter.” (J. c., pp. 62, 63.)

From the above statement it would appear that there could have
been no difficulty, in the course of the Survey, of drawing the line thus
said to be perfectly well defined by “‘an obvious and very general differ-
ence tn the composition of the two sets of strata,” by “ marked differences in
their condition of metamorphism,” and finally, by “a striking contrast in
the manner and direction of their uplift.” One is surprised to find, how-
ever, that all the above-stated differences were not realities, but “ indue-
tions,” and that it was not “ wntil a relatively late date in the prosecution
of the Geological Survey of Pennsylvania, that the geologist of that State
detected positive evidences of this physical break, and of a lapse of time be-

* See ante, pp. 440, 441

468 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

tween the two groups of strata, and established, by ocular proof, the correct-
ness of the previous induction.”

In accordance with this latter statement, and not with the former, we
do not find on the general geological map of the State accompanying
the Final Report any indication of the two groups in question. All the
crystalline rocks seem to be indicated by a single color, and included
under the term “ hypozoic.”

teading still farther in Professor Rogers’s Report (J. ¢., p. 63), we are
even more surprised than before, when we learn that

“Assembling all the evidence which we now possess, we have in the Atlan-
tic Slope, by actual demonstration, but one physical break or horizon of un-
conformity throughout the whole immense succession of altered crystalline
sedimentary strata, and within this region but one Paleontological horizon, —
that, namely, of the already discovered dawn of life among the American
strata. This latter plane or limit, marking the transition from the non-fossil-
iferous or azoic deposits to those containing organic remains, lies within the
middle of the primal series or group of the Pennsylvania survey, that is to say,
in the primal white sandstone... . The Primal slates beneath the sand-
stone, and in intimate alternation with it, possess not a vestige of organic life,
nor has any such been yet discovered anywhere within the limits of the Atlan-
tic Slope, or on the northern or western borders of the Great Appalachian
Basin of North America.” .

Farther on in his Report, Professor Rogers remarks concerning his
two systems of rocks, —the Hypozoic or Gneissic, and the Azoic, —
that “the members of the two groups often simulate each other so
closely, and are indeed so identical in mineral aspect and structure, as to
bajjle all attempts at distinguishing them lithologically.” Again, we are
informed that these systems are nevertheless distinct from each other,
and ‘‘susceptible of delineation on the geological map.” But, it is im-
mediately added, “the State geologist did not venture to define them
on the map.”

Before proceeding to notice the results attained by the Second Geo-
logical Survey of Pennsylvania, in connection with the investigation and
classification of the crystalline rocks of that State, it will be well to refer
to the views published by Dr. Hunt at various times between the com-
pletion of the First Survey and the beginning of the Second. This is
the more desirable, because he was employed by the State Geologist
(Professor Lesley) “to collate all the known, supposed, and suspected facts
of American Azote Geology” for publication by that Survey, apparently
as a sort of manual or guide to the mysteries of that department of the
science, for the use of future investigators. Professor Lesley considers

PENNSYLVANIA. 469

that “a debt of gratitude is due Dr. Hunt for his historical monograph,”
although admitting that ‘no final demonstration has been accomplished
by the author [Dr. Hunt] of those problems of superposition, uncon-
formability, and identification, at which so many geologists are still
half despairingly at work.” (Azoic Rocks, p. vii.) Perhaps this ad-
mitted want of success will not be so difficult to account for. when one
takes into consideration some of the views published by Dr. Hunt pre-
vious to his engagement on the Pennsylvania Survey.

In 1861, Dr. Hunt remarked, regarding the Hypozoic or Gneissic
series of Professor Rogers (Am. Jour. Sci., 1861, (2) XXXL, pp. 394,
395) :—

“We have along the great Appalachian chain, from Georgia to the Gulf of
St. Lawrence, a third series of crystalline strata, which form the gneissoid and
mica slate series of most American geologists, the hypozoic group of Prof.
Rogers, consisting of feldspathic gneiss, with quartzites, argillites, micaceous,
epidotic, chloritic, talecose and specular schists, accompanied with steatite, dio-
rites and chromiferous ophiolites. This group of strata has been recognized by
Safford in Tennessee, by Rogers in Pennsylvania, and by most of the New
England geologists as forming the base of Appalachian system, while Sir
William Logan, Mr, Hall, and the present writer have for many years main-
tained that they are really altered paleozoic sediments, and superior to the
lowest fossiliferous strata of the Silurian series. Sir William Logan has
shown that the gneissoid ranges in Eastern Canada have the form of syncli-
nals, and are underlaid by shales which exhibit fossils in their prolongation,
while his sections leave no doubt that these ranges of gneiss, with micaceous,
chloritic, talcose and specular schists, epidosites, quartzites, diorites and ophio-
lites, are really the altered sediments of the Quebec group, which is a lower
member of the Silurian series, corresponding to the Calciferous and Chazy
formations of New York, or to the Primal and Auroral series of Pennsylvania.
Prof. Rogers indeed admits that these are in some parts of Pennsylvania
metamorphosed into feldspathic, micaceous and talcose rocks, which it is ex-
tremely difficult to distinguish from the hypozoic gneiss, which latter, how-
ever, he conceives to present a want of conformity with the paleozoic strata.
To this notion of the existence of two groups of crystalline rocks similar in
lithological character but different in age, we have to object that the hypozoic
gneiss is identical with the Green Mountain gneiss, not only in lithological
character, but in the presence of certain rare metals, such as chrome, titanium,
and nickel which characterize its magnesian rocks ; all of these we have shown
to be present in the unaltered sediments of the Quebec group, with which Sir
William Logan has identified the gneiss formation in question. Besides
which the lithological and chemical characters of the Appalachian gneiss are
so totally distinct from the crystalline strata of the Laurentian system, with
which Prof. Rogers would seem to identify them, that no one who has studied

470 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

the two can for a moment confound them. Prof. Rogers is therefore obliged
to assume a new series of crystalline rocks, distinct from both the Laurentian
and Huronian systems, but undistinguishable from the altered paleeozoic series,
or else to admit that the whole of his gneissic series in Pennsylvania is, like
the: corresponding rocks in Canada, of -paleeozoic age.”

In the Presidential Address of Dr. Hunt before the American Asso-
ciation, 1871, it is stated that Prof. H. D, Rogers has distinguished
three districts in Pennsylvania of various crystalline schists, which, in
his Report on the geology of that State, he included under the name of
Gneissic or Hypozoic rocks. The gneiss of the northern or South Moun-
tain belt is said by Dr. Hunt to be “ lithologically as well as geognosti-
cally identical with that of the Highlands, and belongs like it to the
Adirondack or Laurentian system of crystalline rocks.” The gneiss of
the middle district seems to be regarded as Laurentian, while that of
the third or southern district is referred to the White Mountain series,
with the exception of the middle subdivision, which is said to present
the aspect of the second or Green Mountain series.

Professor Rogers is stated to have placed above the hypozoic gneisses
his azoic or semi-metamorphic series, which Dr. Hunt regards as belong-
ing to the Green Mountain or Huronian series, in regard to which he
remarks as follows : —

“The azoic or so-called metamorphic primal strata are said to have a very
uniform, nearly vertical, dip, or with high angles to the southward, while the
micaceous and gneissic strata of the northern subdivision of the southern dis-
trict of so-called hypozoic rocks, limiting these last to the south, present either
minute local contortions or wide gentle undulations, with comparatively mod-
erate dips, for the most part to the northward. From this, 1 think we may
infer that the nearly vertical strata must be, in truth, older underlying rocks,
belonging, not to the palzeozoic system, but to our second series of crystalline
schists.” (Proc. Am. Assoc. Ady. Sci., 1871, XX., pp. 7-9.)

It seems, although we were, in 1861, emphatically informed that the
“lithological and chemical characters of the Appalachian gneiss are so
totally distinct from the erystalline strata of the Laurentian system, ....
that no one who has studied the two can for a moment confound them,” that
now we are as positively told that part of it is “Uithologivally as well as
geognostically identical with .. . . [the] Laurentian system of crystalline
rocks.”

In 1875 Prof. J. P. Lesley stated that the Huronian or Green Moun-
tain series seems to overlie the White Mountain series in the vicinity of
Philadelphia ; also, that the conglomerate beds of the Primal series hold

PENNSYLVANIA. 471

pebbles of Huronian rocks. (Second Geological Survey of Pennsylvania,
D, p. 66.)

In 1876, he says that the middle zone of gneiss of Rogers is “‘ now
known to be Laurentian.” (/. c., A, p. 136). It is well known that in
general Dr. Hunt claims a reverse order, or that the Montalban overlies
the Huronian.

In 1876 Dr. Hunt referred the ores, found along the borders of the
Mesozoic red sandstone, and including the Cornwall mine, to the Lower
Taconic (Taconian) ; but no evidence was given to show the justness of
this conclusion. (Trans. Am. Inst.*Min. Eng., 1876, IV., p. 320.)

During this year he also referred other rocks in Pennsylvania to the
Laurentian, Huronian, and Montalban. This determination seems to
have been based exclusively on lithological characters, no further evi-
dence except difference in the strike of their supposed stratification
planes being advanced. The Primal. slates and sandstones of Rogers
were regarded by Dr. Hunt as Lower Taconic (Taconian). (Proc. Am.
Assoc. Ady. Sci., 1876, XXV., pp. 208-212.) He also makes the White
Mountain (Montalban) series in the vicinity of Philadelphia to overlie
the Huronian, although Professor Lesley states that the reverse appears
to be the case.

In Professor Frederick Prime’s Report (Second Geological Survey of
Pennsylvania, DD, 1878) the gneissic rocks in Lehigh County are called
Laurentian. In one locality he says that

“the junction of the Potsdam sandstone and Laurentian rocks can be well
seen. The dips of the two rocks seem to be conformable, but this may be
wrong, as the exposure is small and the gneiss apparently has a slight roll.
The gneissic rock is here distinctly bedded.”

It is probable that Professor Prime uses the term ‘“ distinctly bedded ”
for “ distinctly foliated,” terms which have not as yet been proved to be
synonymous. He further says : —

‘Tt is possible that these gneissic rocks which seem to lie conformably with
the sandstone, and which are true gneisses, are in reality Lower Potsdam.”

(l. ¢., pp- 9, 10.)

In 1877, Professor Prime advances some evidence to show that the
Potsdam sandstone was deposited upon the gneiss and made out of its
ruins ; had he deemed this determination a matter of as much impor-
tance as it seems to us to be, he would doubtless have investigated the
matter more closely. It is to be hoped that this may yet be done. He
shows that the mica schists (hydro-mica slates) lie between the Potsdam

472 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

sandstone and Magnesian limestone, conformable with both, and that
they therefore cannot belong to the “ Taconian” of Hunt, as the latter
had stated. Professor Prime also says : —

“Tt is well here to emphasize the fact that these brown hematite ores all
belong to the Lower Silurian limestone formation, since, in 1875, Dr. Sterry
Hunt, after a cursory examination of Ziegler’s Mine in Berks County... .
made the mistake in a paper on ‘The Decay of Crystalline Rocks’ before the
National Academy of Science, of supposing that the hydromica slates belonged
to the Huronian Period :—a mistake into which so eminent an observer as
himself would never have fallen had he been better acquainted with the
region.” (Proc. Am. Phil. Soc., 1878, XVII., pp. 248-254; Am. Jour. Sci.,
1878, (3) XV., pp. 261-269.)

Mr. Charles E. Hall thus indicates the formations of Eastern Penn-
sylvania, in their ascending order (Proc. Am. Phil. Soc., 1880, XVIII,
pp. 435-443) : —

First. A series of granitoid, syenitic, quartzose, and micaceous schistose
rocks,

Second, A series of syenitic, hornblendic and quartzose rocks. He states,
however, that “this series may be the upper members of the first.”

Third. Potsdam ‘sandstone, conglomerate, quartzite, and occasional schis-
tose beds. “ This, the Potsdam sandstone, rests unconformably upon the pre-
ceding two groups. The unconformity is seen at points east of Willow Grove,
where the lower conglomerates contain fragments of the syenitic rocks.”

Fourth. Dolomites, schistose or slaty micaceous beds, limestone, marble,
hydromica schists, and bastard marble. “ This group of limestones and schists
rest on the above group, and are the equivalent of the Cambrian limestones of
the Great Valley.”

Fifth. Hydromica schists, quartzose schists, chloritic schists, and occasional
beds of quartzites and sandy beds and serpentines.

Sixth. Micaceous, garnetiferous schists, limestone, mica schists and sand-
stones. “This group rests unconformably upon the western extension of the
second group.”

Seventh. “The mica schists of Philadelphia, mica schists, hornblendic, gar-
netiferous, talcose schists with soapstone and serpentine. .... They rest
unconformably upon the first, second, third and fourth groups... . . There
are besides these groups probably two serpentine horizons, which are undoubt-
edly unconformable deposits above the second group. I think the northern
belt of serpentine may be considered as altered Hudson river rock ; while the
southern belts are doubtful.”

The slates of Chester, York, and Lancaster Counties (including the
Peach Bottom slates), as well as the serpentines of Radnor, Easttown,
Willistown, and East and West Goshen, are stated to be undoubtedly

PENNSYLVANIA. 473

of Hudson River age. (See also Am. Jour. Sci., 1880, (3) XIX., pp.
413, 414.)

From the above it will be seen that Mr. Hall makes his first and
second groups — which, however, he seems to think may perhaps
belong together — to be older than the Potsdam Sandstone, which over-
lies them unconformably. None of the rest of his groups can, there-
fore, be of Azoic age. This is a result very different from that attained
by Dr. Hunt and others, who have made most of this region pre-Silu-
rian. But Mr. Hall’s views seem to have a substantial basis of obser-
vation, while Dr. Hunt’s cannot be regarded as anything more than
theories based on lithological resemblances. How fanciful these are
may be inferred from the contradictory statements of that author him-
self in regard to the rocks in question.*

By way of illustrating the difficulty of separating the lower formations
from each other in the crystalline belt of Pennsylvania, it may be well
to add one or two extracts from the latest publication of the present
Survey of that State ;— “ The Geology of Chester County, after the Sur-
veys of Henry D. Rogers, Persifor Frazer, and Charles E. Hall. Edited
by J. P. Lesley [State Geologist], C4, 1883.” In this publication two
maps are given, one of which embodies the conclusions reached by Pro-
fessor Rogers, the other those of Mr. C. E. Hall, the region embraced in
these maps being essentially the same, and forming part of Delaware
and Chester Counties. A comparison of these maps will show how
utterly unlike they are ; but perhaps it will be better to quote Profes-
sor Lesley’s own language on this point. He says (J. ¢., p. viii.) : —

“ Tt is impossible to imagine a greater contrast than between these two illus-
trations of opposite views. The great regularity of Mr. Rogers’ belts, the utter
irregularity of Mr, Hall’s areas, strikingly exemplify the difference between the
conclusion arrived at, in a difficult region like this, by the earlier geologist
who made everything bend to his theory of parallel overturned anticlinals and
synclinals, and the observations of the later geologist who is fettered by no
such theory, but is perhaps quite as strongly influenced by a different senti-

ment, viz.: that the Azoic formations spread out over one another with mod-
erate inclinations unconformably.”

Furthermore, the following may be quoted from the same source, as
illustrating the facts that even the later geologists — those, namely,
who have worked longest and most perseveringly in this difficult field —
have not been able to arrive at concordant results, Professor Lesley
remarks (J. ¢., p. 34) : —

* See ante, pp. 469, 470.

474 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

“Since 1858 the district in question has been closely and repeatedly investi-
gated by Prof. Frazer and Mr. Hall, the one approaching it from the west, the
other from the east. They differ radically in their views of the order and -
superposition of the formations, not only from Prof. Rogers, but from each
other ; so that this report will leave several points of geology in almost as great
obscurity as ever.”

Finally, the following may be commended to the consideration of the
reader (/. ¢c., p. 53) :—

“Tt will be seen from the summary of Prof. H. D. Rogers’ observations in
1851, given above, that he was guided everywhere by a theory of parallel anti-
clinal folds in the great Azoic or Hypozoic strata ; and of intermediate synclinal
troughs, some of them wide and deep, others narrow and shallow, but all of
them containing preserved remnants of more micaceous strata, of a later age,
but probably older than the hydro-mica slates of the South Valley hill. In
no respect however does he settle the great question of what the true relation-
ship may be between the older and newer gneisses, — between the newer
eneisses and the talc-mica-schists, — between the talc-mica-schists and the
sandstone (quartzite) — between the quartzite and limestone — between the
limestone and serpentine —in the southern townships of Chester county.
After an apparently copious and precise array of facts the geology of the
whole district remains as confused and obscure as ever. The section along
the Schuylkill is the key to the lock ; but the key will not turn in the lock ;
the door remains closed. ... . We travel to and fro across the hills and find
no clue to guide us out the labyrinth of infinitely various and yet strangely
similar deposits, the strike of which is everywhere more or less doubtful to the
eye and tempting to the imagination.”

VIRGINIA.

Prof. W. M. Fontaine states that certain coarse syenites and granites
in the vicinity of Balcony Falls and the Peaks of Otter, “from their
stratigraphical relations and composition,” are plainly of Laurentian
age. These rocks appear to be regarded by him as being eruptive in
many places. Since he assumes without any apparent evidence, except
the “look” of the rocks, the passage of sedimentary rocks into remark-
able metamorphic forms, and also that other rocks are eruptive from the
same evidence (their “looks ”), his statements relating to crystalline
rocks need in most cases to be accepted with caution until the proof is
presented. It is doubtful if the supposed primordial rocks are of that

VIRGINIA. 475

age. Should they hereafter be shown to be Primordial, all that Pro-
fessor Fontaine’s evidence shows is an older series of rocks containing
eruptive granites, syenites, etc. His writings are far from being clear,
but we are unable to find any proof in them that the granite and syenite
are of different geological age from their associated rocks. (Am. Jour.
Sci., 1875, (3) IX., pp. 14-22, 93-101, 361-369, 416-428.)

It would appear that Prof. J. L. Campbell regards the Laurentian
granites and syenites of Professor Fontaine as eruptive rocks, erupted
since the deposition of the supposed Primordial strata, thus leaving
- only one formation a situ under the supposed Primordial. Professor
Campbell holds, however, that the eruptive syenites and granites are
metamorphosed, and displaced underlying formations. In another lo-
cality he seems to regard the syenite as a “syenitic gneiss (or strati-
fied syenite), which might readily be taken for an igneous rock — so
greatly has it been metamorphosed” ; but he fails to give any evidence
that it is not igneous, or any reasons why it should be regarded as a
metamorphosed sedimentary rock. He also fails to show that the sup-
posed Primordial is composed of the débris of his supposed Archean.
As has been before remarked in other similar cases, it is not here our
intention to assume that the conditions are not as they are assumed to
be ; it is simply our wish to call the attention of the observers to the
fact that their published observations fail to furnish the proof necessary
to be presented before these ideas can be accepted as axioms. They
are not of the nature of self-evident truths. (Am. Jour. Sci., 1879,
(3) XVIIL., pp. 16-29, 119-128, 435-445.)

The latest setting forth of Professor Fontaine’s views on the subject
here under discussion will be found in a letter from himself to Professor
Lesley, dated January 20th, 1883. (Second Geological Survey of
Pennsylvania, Report, C*, 1883, pp. xiii—xvi.) In this letter he clearly
assumes that the division of the Azoic rocks into Laurentian and
Huronian is to be taken for granted as something so clearly established
that it must stand, no matter how difficult it may be to reconcile the
theory with the facts. The Huronian seems to be wanting; that is, he
finds it very difficult to discover rocks having the proper lithological
characters. Thus he says (J. c., p. xiii.) : —

“The Blue Ridge in the northern part of Virginia is, as I take it, much as
it is in your South Mountains of York, &c. The Huronian strata hide very
largely the Laurentian. On the Potomac the latter does not show at all.
.... The Laurentian sinks and expands as we go south in Virginia, and
often has over it a mere remnant of the Huronian. ... . Still farther south-

476 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ward, in the counties of Floyd and Carroll, I could find no typical Huronian,
such as the chlorite rocks, the felsite, &c.”

Throughout the whole of this communication it appears clearly that
Professor Fontaine considers that the terms Huronian and Laurentian
are simply names for certain lithologically peculiar rocks. Chlorite
schists are called “typical. Huronian,” and gneisses “ Laurentian” ; but
it is easy to see from his description that the two, with the other ordina-
rily associated rocks, occur together, sometimes one predominating and
sometimes another, in a manner perfectly characteristic of the Azoic
series as a whole, yet utterly in opposition to their existence as sepa-
rate and distinct systems.

NORTH CAROLINA.

In the Report of Prof. W. C. Kerr on the Geology of North Carolina
(1875), a large portion of the rocks of that State is assigned to the
Laurentian and Huronian formations. Three distinct belts of Lauren-
tian are recognized. The eastern one

“consists of light colored and grey gneisses, which occasionally pass into gran-
ite, but more frequently into felspathic, quartzose (and rarely hornblendic)
schists. In some localities the mica is entirely wanting, and then the rock is
either a dull-reddish, brownish, or whitish massive felspathic rock, trachyte,
euryte, felspar porphyry, &c.” (i. c., p. 122.)

The Edgecombe granite, which Professor Kerr regards as a metamor-
phosed sedimentary rock (gneiss), “ shows no gneissic or foliated struc-
ture, being undistinguishable from true granite.”

In the second area (J. ¢., pp. 123-128), —

“the characteristic and prevalent rocks are syenyte, doleryte, greenstone, am-
phibolyte, granite, porphyry, and trachyte . . . . The most common rock is of
a hornblendic character ; and traps, trachytes, granulytes and porphyries are
confusedly and angularly wedged in among each other, with freyuent veins of
epidote crossing the felspathic species in every direction. ... . The absence of
anything like stratification or foliation is conspicuous throughout the region.
.... If there be any significance in structure or in lithological characters,
this singular body of rocks seems entitled to be placed at the very base of the
Archean age, certainly at the bottom of the Laurentian ; and even below
these, if there be any older rocks exposed anywhere, —the true Azoic or

NORTH CAROLINA. 4TT

Igneous. In the direction of this notion certainly point the absence of strati-

fication, the non-occurrence of limestone, and the great predominance of
syenytes (mostly hyposyenyte), and other iron-bearing and basic rocks. L|

have only placed them as the lower Laurentian, however, since there seems to

be a general disinclination to suppose that the primal igneous core anywhere

shows itself to human inspection. This belt may well be characterized as the

geological axis of the State. The group of rocks just described is bounded on

the northwest by a series of gneisses and feldspathic and occasionally horn-

blendic slates, which extend westward, with little interruption to the Blue

Ridge, and, except a narrow zone of a few miles breadth along the course of that

chain, includes the whole mountain region to the flanks of the Smoky Moun-

tains, through the greater part of its length. These are considered to belong

to the Laurentian proper. . . . . A few miles west of this is a narrow terrane

of syenytes and other hornblendic rocks and granites. .... The predominance

of hornblendic rocks, the absence of mica, and the general absence of stratifica-

tion have seemed to justify the reference of this belt to the lower part of the

series, along with the preceding central zone. ... . Another considerable

area of Laurentian rocks is found beyond the Blue Ridge, occupying most of
the mountain plateau between that and the Smoky Mountains, and in places

constituting the materials of these chains, As stated before, this area may

very properly be considered as only a continuation of the preceding, from

which it is divided by a very narrow and interrupted belt of Huronian slates.

. . « . The rocks of both of these, like those of the preceding area, are foliated
for the most part, and consist of indefinite alterations of the same kinds of
metamorphic strata, — gneiss, hornblendic, feldspathic and micaceous schists,

and occasionally chloritic and talcose slates.”

In regard to the principal Huronian belt, Professor Kerr makes the
following statement (/. ¢., p. 133) : —

“The belt is bounded on both sides by the Laurentian, already described, on
which it lies unconformably, and from which its materials were derived. The
stratigraphy therefore indicates the horizon ofthese rocks to be the Huronian,
and the lithology agrees well with that determination; and the reasonable
course therefore seems to be, to place them as Huronian, until some evidence
shall be found of an organic character, to lift them to a higher geological
plane. The absence, or at least the non-discovery of fossils hitherto, in an
extensive body of slates like those of the middle and west portions of this
tract, so little altered and so well adapted to the preservation of even the most
delicate organisms, and in a region so much studied, and on account of numer-
ous mines, offering so good opportunities for the discovery of fossils if any
existed, is certainly so far confirmatory of the sub-Silurian theory of these
deposits. This is the principal area of Emmons’ Taconic in this State.”

Prof. F. H. Bradley, however, who had made a special study of the
rocks of Eastern Tennessee, subsequently examined a considerable por-

478 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

tion of Western North Carolina, as well as the adjacent regions of
Georgia and Alabama. In a series of papers entitled “ On the Silurian
Age of the Southern Appalachians,” (Amer. Jour, Sci., 1875, (3) IX.,
pp. 279-288, 370-383,) this geologist reaches conclusions which he thus
states : —

“ The rocks of that portion of North Carolina south and west of the Little
Tennessee, together with the metamorphic area of Georgia, north of a line par-
allel with and ten miles south of the Chattahoochee (and probably that south of
this line), and the entire metamorphic area of Alabama, are Silurian or newer,
with the possible exception of two or three small patches not over ten miles in
diameter.” (I. c., p. 280.)

Professor Kerr acknowledges that, if Professor Bradley’s identifications
prove valid, it will probably be found that all the Huronian rocks except
those of the middle and eastern belts will prove to be Silurian. Of
these he remarks (/. c., p. 140) : —

“ But this conclusion will not involve the great middle and eastern belts
which must still remain Huronian, until determined independently to belong
to a later series ; both because they are widely separated from the others, and
because they have lithological and stratigraphical characters of their own, which
would prevent their following any determinations of horizon for the others,
which should be based on these considerations alone.”

In regard to an area adjacent to Tennessee, Professor Kerr says (/. ¢.,
p- 139) :—

“This belt of rocks is colored on the map throughout like the other Huro-
nian belts, and for the same reasons, viz.: that they succeed the Laurentian,
and differ from them strongly in degree of metamorphism and general litho-
logical character, so that the transition from one to the other is obvious along
the whole extended line of contact, and that they have yielded no fossils,
which alone could authorize their reference to a later age. And although the
fact of unconformability can not be asserted for any one of the sections, this may
arise from the circumstance that the disturbance and dislocation of the strata
along this line are extreme, and that no detailed or minute examination has
ever been attempted, and of course nothing short of such examination would
suffice in such a region. And another circumstance of weight is the immense
body of these rocks, which must be allowed, on the French Broad for example,
after every reasonable reduction for folding, a thickness of several miles. Add
these to the primordial or the lowest members of the Lower Silurian, and they
receive a most incredible development downwards, since the rocks along the
Tennessee border referred to this horizon have already a very great thickness.
However, as stated above, these rocks have only been located provisionally.
And it is right to say further that the only examination I have made of this
western Smoky belt, was a mere reconnoisance, mostly on horseback, made in
a few weeks in the autumn of 1866.”

SOUTH CAROLINA. 479

In 1878 Dr. Hunt referred part of the gneisses of North Carolina to
the Laurentian, but found “ indications of a belt of Huronian schists,”
while the “thin bedded gneisses with highly micaceous and hornblendic
schists,” which Professor Kerr had regarded as Laurentian, he referred
to the Montalban.

It results quite clearly from the study of what has been published
by Professors Kerr and Bradley, that there has been no satisfactory
reference of any of the rocks of North Carolina older than the Triassic
to their proper place in the geological series. Professor Kerr's Lauren-
tian and Huronian include all the existing stratified formations in that
State below the Trias, and, judging from what is known of the geological
structure of the Appalachian belt farther north, it is highly probable
that Professor Bradley was right in referring a considerable portion of
the metamorphic rocks of North Carolina to the Paleozoic. At all
events, it is safe to say that, with our present uncertainty in regard to
the geological age and structure of the region in question, there can be
no reason for dividing the older rocks into Laurentian and Huronian
other than on purely theoretical grounds.

SOUTH CAROLINA.

But little is known in regard to the older crystalline rocks of South
Carolina. Mr. Lieber, the former State Geologist, describes different
varieties of them ; but he gives no clue to their geological position, and
but little information is afforded as to their order of succession. Dr.
Hunt, however, has endeavored, on the basis of Mr. Lieber’s description,
to range the various rocks of this State within the systems described by
him as occurring farther north. He says (Proc. Am. Assoc. Ady. Sci.,
1871, XX., pp. 10, 11):—

“ Tt is easy, from the reports of Lieber on the geology of South Carolina, to
identify in this State the two types of the Green Mountain and White Moun-
tain series. The former, as described by him, consists of talcose, chloritic, and
epidotic schists, with diorites, steatites, actinolite-rock, and serpentines. . . . .
The great gneissic area of Anderson and Abbeville districts is described by
Lieber as consisting of fine-grained gray gneisses, with micaceous and horn-
blendic schists, and is cut by numerous veins of pegmatite, holding garnet,
tourmaline, and beryl. These rocks, which have the character of the White

480 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Mountain series, appear, from the incidental observations to be found in
Lieber’s reports, to belong to a higher group than the chloritic and serpentine
series, and to dip at comparatively moderate angles.”

We have not been able to find in Mr. Lieber’s reports any evidence
that the gneissic rocks of Abbeville and Anderson districts were con-
sidered by him as newer than the chloritic and serpentine series. On
the contrary, the granites and gneisses are again and again stated to

be the oldest rocks in the State.

GEORGIA.

In Georgia, according to Dr. George Little, the State Geologist, there
are no Azoic rocks; but Dr. Hunt on lithological grounds referred some
gneisses (granites) to the Montalban, and some slates probably to the
Taconian.

TEXAS.

Mr. S. B. Buckley, State Geologist, in his various reports, describes
various forms of eruptive, crystalline, and metamorphic rocks as occur-
ring in that State. In his First Annual Report he defines the Azoic
as follows : —

“The Azoic are igneous rocks, destitute of animal and vegetable matter,
thrown up from below, or rocks altered by contact with such melted matter.

. . Some of the Azoic rocks are the oldest known, and others not, for there
are granites in Texas, . . . . which have been thrown up during the forma-
tion of the rocks of the older Silurian.” (J. ¢., pp. 15, 16, 76.)

In his Second Report, Mr. Buckley recognizes two distinct ages —
the Azoic and the Eozoic— as forming “ Archean time.” In the Azoic
he includes the granites and their associated rocks destitute of fossils ;
viz. shales, mica schists, gneiss, hornblende, porphyries, etc. There are

said to have been two or more periods of the upheaval of the canter,
one probably later than the Cretaceous.

Since it is so evident that Mr. Buckley under the head of Azoic
includes rocks of very different ages, it will not be necessary for us to

TENNESSEE. 481

dwell at large upon his work, which is of no importance in reference to
the question before us. The views he appears to hold with regard to
the eruptive and older stratified rocks in general are quite analogous
to those of Prof. C. H. Hitchcock, which have already been presented, as
well as to those of the geologists of the Fortieth Parallel Survey, to
which reference will be made a little farther on.

TENNESSEE.

Prof. J. M. Safford, in his first Report on the Geology of Tennessee,
1856, referred the metamorphic rocks of the State to the Azoic, separat-
ing them into two series: the semi-metamorphic, and the metamorphic.
In the Final Report (1869) the metamorphic rocks were regarded as
Azoic or Eozoic ; but he states that they can be traced in part to un-
metamorphosed beds, and from what follows it will be seen that he
regarded them as in part formed from and in part conformably under-
lying the Ocoee group, which he referred to the Potsdam. He says of
the metamorphic rocks of the State : —

“With reference to age, I have no reason for believing that this group,
within Tennessee, includes the metamorphosed beds of any formation of more
recent date, than the Ocoee Conglomerate and Slates. A portion of the beds
are certainly referable to the Ocoee Group ; the remainder, although conform-
able, may be older, and most likely are. There are sections which show
clearly the change of the conglomerate, and its associated rocks, into gneiss and
mica, and other slates. In approaching, for instance, the Ducktown region,
from the west, the pebbles of the conglomerate gradually lose their forms,
becoming more and more, small, shapeless masses of quartz, and yet discern-
ible, even when the gneissoid or complete metamorphic character is seen. In
the northern part of the State, at many points, the passage of the Ocoee beds
into gneiss, is gradual and apparent. A considerable part, indeed, of our meta-
morphic rocks, can be, I think, thus referred to these beds. The question as
to the greater age of other parts, is not so easily settled, and must remain open
for the present. I know of no sufficient reason for referring any of these rocks
to the Huronian or Laurentian series of Canada.” (J. c., pp. 177, 178.)

Prof. Frank H. Bradley holds that all the metamorphosed rocks in
Tennessee were Silurian. (Am. Jour. Sci., 1875, (3) IX., pp. 279-288,
370-383.)

VOL. VII.—Nno. 11. 31

482 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

ARKANSAS.

It appears that Dr. David Dale Owen regarded the crystalline rocks
of Arkansas as eruptive, stating that the sedimentary rocks have been
shattered, uptilted, and broken by them. He also gives localities in
which they overlie the slates. His evidence, what there is of it, would
indicate the correctness of his views, but it is far from being as com-
plete as would be desirable.

MISSOURI.

There is no published evidence showing that the crystalline rocks of
Missouri proved to be older than the Silurian are of different ages, or
that most of them are not eruptive. They have been assigned to the
Laurentian and Huronian, but solely from their lithological characters.

MICHIGAN AND WISCONSIN.

A short time ago a discussion of the various theories regarding the
crystalline rocks of the region adjacent to Lake Superior, and especially
its southern shore, was published by one of the authors of the present
paper.* In that work the evidence by which the theories in question
have been sustained was pretty thoroughly examined, and it now re-
mains, therefore, only to add that which is necessary in order to bring
the discussion down to the present date. Some little repetition and
recapitulation will, however, be advisable, in order that the reader of
this paper may have a clearer idea of the points here discussed.

The copper-bearing rocks of Lake Superior have been considered by
some geologists as a distinct formation, older than the Potsdam sand-
stone adjacent to which it lies. The principal evidence in support of
this opinion was supposed to have been obtained at the falls of a branch
of Torch River, known by the name of Douglass Houghton. Here the

* Notes on the Geology of the Iron and Copper Districts of Lake Superior. By
M. E. Wadsworth. This Bulletin, ante [Vol. VII., or Geol. Series, Vol. I.],
pp. 1-157.

MICHIGAN AND WISCONSIN. 483

trappean or cupriferous series was said to end, and to have abutting
against its edges strata of the Potsdam. The latter was also said to
contain fragments of the other, necessarily older, rock. These facts were
thought to prove that the copper-bearing rocks formed a sea-shore bluff,
along the base of which the sandstone was deposited with its trappean
fragments. In order that the reader may understand the condition of
things at that point, it will be necessary for us to indicate the structure
of the copper-bearing rocks themselves. They consist of a series of old
lava flows (diabase and melaphyr), intercalated between beds of con-
glomerate and sandstone. The traps are known to be lava flows, by
the baking and induration of the immediately underlying rock ; by the
fact that tongues and dikes extend from the overlying trap down into
the rock beneath ; by the scoriaceous character of the upper portion of
the traps, and the coarser crystallization of their lower parts ; by the
macroscopic and microscopic evidences of flowing, etc. That they in
each case were in situ before the immediately overlying rock was depos-
ited, is shown by the facts that they have not affected it in any way, and
that they present on their upper surface the irregularities and rounded
knobs which lava flows are known to have, especially when exposed to
water action ; by the presence of rounded fragments of the underlying
trap enclosed in the overlying conglomerate ; by the absence of frag-
ments of the overlying rock in the underlying one, and by the absence
of any marks of intrusion of the traps between different beds.
Sometimes the lava flow was followed by another, without any appar-
ent long exposure of the former ; then again the interval between the
two succeeding flows was so great, that sandstones and conglomerates
having a thickness of from a few inches to half a mile (Marvine) were
deposited between them. Of course from this it followed that the
surface of the underlying trap suffered denudation, and that afterwards
the conglomerate was deposited unconformably upon it. This was
the general mode of formation throughout the series on Keweenaw
Point. The general condition of things may be correctly indicated by
the statement, that in going from the east towards the west the cu-
priferous series is found to be made up of an increasing number of lava
flows and a diminishing number of conglomerates, until a point is
reached where the volcanic activity culminated, when the flows dimin-
ished and the conglomerates increased, until the Western sandstone was
reached. It would follow from the mode of formation, that whenever a
sandstone or conglomerate was laid down on the trap, denudation of the
latter would take place and fragments of it be enclosed in the uncon-

484 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

formably overlying detrital rock ; and this would hold good not only of
the intercalated beds, but also of the Western sandstone. All these
evidences of denudation would then be merely signs of sequence of time, .
and not of a difference in geological age. Precisely similar facts may
be observed at the present day wherever a lava flow has an opportunity
to reach the shore of the sea.

The question, then, whether the copper-bearing rocks are a formation
of a geological age older than the Lake Superior sandstone, is to be
ascertained, if at all, on the eastern, and not on the western side. It
has just been pointed out on what evidence the Eastern sandstone was
said to be younger than the traps; but a careful examination of the
region in question showed its incorrectness. At the Douglass Houghton
Falls the stream passes over a cliff of trap, and then winds through a
gorge having high and very steep banks. It was very natural that, in
ascending this stream from Torch Lake to the Falls, the hasty observer
should be led to believe that the sandstone and conglomerate extend in
an unbroken band up to the cliff at the latter locality, and regard it as
an old sea-shore bluff. This would especially be the case should he
confine his observations to the stream, and not attempt to explore the
clayey, slippery, difficult sides of the ravine. ‘The writings of previous
observers give no evidence that they did more than to follow the bed of
the stream ; and they all concurred in stating that the sandstone was
horizontal, or nearly so, up to the Falls, at which place the trap was said
to be first met. When Dr. Wadsworth examined the locality, in 1879,
he not only explored the bed of the stream, but also the bluffs on both
sides. These examinations showed that the sandstone and conglomer-
ate were not horizontal, but that they had a gradually increasing dip as
the Falls were approached from 5° up to 25°, while on both sides of the
stream the traps were found holding the same relations to the sand-
stone and conglomerate that they have been stated to hold elsewhere in
the series. These traps had been masked and concealed by the falling
rock and earth ; but, on digging, foot after foot of the junctions of a num-
ber of the lava flows and their adjacent sandstones were exposed. The
flow nearest Torch Lake is about two feet in thickness, lying between
two beds of sandstone, all having a dip of 20°. Junctions of these beds
and the flow were exposed by excavating along a distance of about
twenty feet. The trappean pebbles seen by former observers at the
Falls were seen to have been derived from the underlying trap, as they
are throughout the entire series, and not from the supposed old sea-
shore bluff. In the same way, the sandstone and conglomerate were

MICHIGAN AND WISCONSIN. 485

carefully followed up by the Hungarian River from Torch Lake, and
the same condition of things observed. (Ante, pp. 113-116.)

These observations are of a kind to exclude any probability of a mis-
take; they are clear, and definite. Moreover, they explain the errors
of previous observers, and until refuted, if they can be, they conclu-
sively show that the Eastern sandstone and the copper-bearing series are
one and the same geological formation, although differing in time se-
quence. It is a remarkable circumstance, that, while this evidence is so
clear and explicit, the more recent writers have carefully avoided any
mention of it, but have endeavored to discuss the subject on theoretical
grounds chiefly.

It now becomes necessary to follow in greater detail some of the writ-
ings of others previous to 1879 and later, owing to the importance
claimed for them in the more recent discussions. The first to demand
our attention is a paper by Prof. R. D. Irving on the relations of the
Huronian, Keweenawan, and Potsdam Series. He states (Trans. Wisc.
Acad. Sci., 1873-74, IL., pp. 117-119) :—

“The conclusions, then, that I would draw are these : —

“1, The Copper Bearing and Huronian Series were once spread out horizon-
tally one over the other, and owe their present highly tilted position to one
and the same disturbance.

“9. That subsequently — after a long period of erosion —the horizontal
Silurian sandstones were laid down over, and against the upturned edges of
the Copper Bearing Series, filling also the synclinal, in Ashland county, which
lies between the northward and southward dipping sandstones.

“3. That hence the Copper Bearing Series is more nearly allied to the Ar-
chan, than to the Silurian rocks.

“ One fact observed, however, seems at first difficult of explanation on this
hypothesis. In Douglas county, as already said, the horizontal sandstones can
be traced to their exact junction with the southward-dipping traps. But, in
several places, the sandstones present a very remarkable change as the trap is
approached. On passing up the gorge of Black River, whose sides are perpen-
dicular exposures of rock over one hundred and fifty feet in height, towards
the south, the horizontal layers of sandstone are suddenly seen to change from
their ordinary position to a confused mass of broken layers, dipping in every
conceivable direction, and increasing in confusion as the trap is approached,
until, finally, the whole changes to a confused breccia of mingled trap and
sandstone fragments. This appearance is presented along both sides of the
gorge, for a distance of 300 feet, and I am assured by my assistant, Mr. E. T.
Sweet, by whom all observations in Douglas county were made, that it is cer-
tainly due to no mere surface misplacement. The same appearance is pre-
sented on one of the other northward flowing streams in Douglas county, on a

486 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

much diminished scale however, the undisturbed sandstones reaching within
twenty feet of the trap. On all other of these streams, the sandstone is undis-
turbed, The explanation which first suggests itself to account for these dis-
turbances is naturally, that they were caused by the ejection of the traps
through the already formed sandstones. In answer to this it may be said that
it is very difficult to see how just such a disturbance as this could have been
caused in this way, the sandstones presenting no appearance of baking or other
indication of heat, but seeming rather to have been crushed by a pressure from
the south. Next the trap it is crushed to a confused mass, a little further a
few layers of sandstone become distinguishable, still further these are all dis-
tinct but broken and pitching in every direction, and finally they grade into
regular unbroken horizontal layers. It may also be said that the proofs
already given of the greater age of the copper bearing rocks, as compared with
the horizontal sandstones are so strong as to necessitate some explanation of
these disturbances other than the one just mentioned. The only one that I
can offer, is this ; the traps being deep seated are, as it were, independent of
the more superficial sandstones, and would, if impelled to move by any force,
move independently of them. Now avery slight movement of the traps north-
ward against the sandstones would produce all the phenomena observed. Such
a movement is not at all difficult to explain.” (See also Am. Jour. Sci., 1874,
(3) VIIL., pp. 46-56.)

In 1879 Professor Irving adopted, in part, a different mode of ex-
plaining the phenomena observed above. He remarks : —

“Tt appears that at the contact there isin many cases a confused brecciated
mass of sandstone and crystalline-rock fragments, some of which are of great
size, while in places they become rounded, and the rock passes into the ordi-
nary conglomerate. These peculiar appearances, only in one case reaching to
any considerable distance from the crystalline rocks, are to be attributed in the
first place to the naturally confused mode of deposition on the cliffy shore of
the waters in which the sandstones were originally deposited, but, as I have
shown in another place, a slight movement northward of the deep-seated crys-
talline rocks against the more superficial sandstone would account for much.
Another thing tending to confuse would undoubtedly be the chemical action,
which, as is well known, is so apt to be set up with unusual energy along
the contact of dissimilar formations.” (Geol. of Wisc., 1880, III, pp. 17,
307.)

Mr. E. T. Sweet, in his report in the same volume, (p. 337, see also
pp. 349, 350,) states in regard to the same phenomena, that “on Mid-
dle river, the original lines of deposition have been entirely obliterated,
and the very argillaceous sandstone transformed into a transverse cleav-
ing slate, somewhat micaceous.” This shows the incorrectness of Pro-
fessor Irving’s statement that the sandstones present ‘“ no appearance of

MICHIGAN AND WISCONSIN. 487

baking or other indication of heat.” It seems to us that the phenom-
ena observed can best be explained by supposing that dikes intruded
themselves after the sandstone was in position, and it is surprising that
observations of a more thorough nature were not made so that the
question should have been settled. The fracturing, the upward bending
of the layers of sandstone, its induration and metamorphism, are all
ordinary occurrences in the contact*of intrusive matter with the adja-
cent rock, and other explanations should not be resorted to until ren-
dered necessary by the facts observed. No such phenomena have been
observed in the contact of the Azoic with the Paleozoic rocks in the
vicinity of the Great Lakes. In fact, it seems from Professor Irving’s
own language that he would hardly have adopted the explanation he
did, if Messrs. Pumpelly and Brooks had not previously endeavored to
sustain the view that the copper-bearing rocks are older than the Pots-
dam sandstone.

Again, it is not shown that these traps are of the same age as those
of Keweenaw Point. The only evidence advanced would be quite as
effective to show that many of the dikes in the granites and schists of
the Azoic, or even the traps of Nova Scotia, are Keweenawan. More-
over, if a lateral thrust is necessary to explain certain facts seen, the
phenomena observed could be as well accounted for in this way on the
supposition that the sandstone was traversed by a dike, as by the hy-
pothesis that it was a newer formation abutting against the Cupriferous
series.

In another place Professor Irving states :—

“ Fortunately, however, we have at hand a more absolute proof than this, of
the age of the Keweenawan System, for at the Dalles of the St. Croix river,
thirty miles above its junction with the Mississippi, and on the west line of
Wisconsin, we find horizontal sandstones and shales, crowded with characteris-
tic Primordial fossils, lying upon the irregular and eroded surface of a Kewee-
nawan inelaphyr. The contact is finely exposed, and the sandstone near the
junction is full of rounded and angular fragments of the underlying melaphyr.
This place was described by Owen, but, so infected was he with the prevalent
ideas of intrusive rocks, that he looked upon the melaphyr as the newer of the
two, disregarding the overwhelming evidence of direct superposition, of the
undisturbed condition of the sandstone, and of the melaphyr pebbles and boul-
ders it contains..... It is evident enough, then, that we have here proof
absolute that the Keweenawan series belongs below the base of the Paleozoic
column of the Mississippi.” (Geol. of Wisc., 1880, III., pp. 23, 24, 339, 396,
397, 423 ; Trans. Wisc. Acad., 1875-76, III., pp. 45-52 ; Owen, Geol. Survey
of Wisc., Iowa, and Minn., pp. 164, 165.)

488 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

In Prof. T. C. Chamberlin’s Report, prepared from the notes of the

late Moses Strong, it is stated of the same locality : —

“This locality presents the most clear and unequivocal evidence that the
Copper-bearing series is much older than the Potsdam sandstone of our state,
so much older, indeed, that there was time for the very extensive wearing
down of the former before the latter was deposited.” (Geol. of Wisc., 1880,
III., pp. 416-419.)

Professor Irving later carried his work into the Michigan region, and
thus states the conclusions at which he arrived : —

“The series is older than the Cambrian and younger than the Huronian —
the separation from the former being by an intervening disturbance and ero-
sion, and from the latter by an intervening erosion, and possibly also by an
intervening folding and alteration.”

He further found the acidic rocks, from which most of the Keweenaw
conglomerates were derived, in place, and adopted the published view of
Dr. Wadsworth (ante, pp. 113-122), that these rocks are old rhyolites
and trachytes. (Report of the Director of the United States Geological
Survey [2d Annual], 1882, pp. xxxi.—xxxiv.) Irving also adopted the
theory of a synclinal structure of the region, first announced by Foster
and Whitney. ;

Mr. A. R. Selwyn later claimed that he had not expressed any opinion
regarding the age of the trap and sandstone of Lake Superior, forgetting
the previous expression of his views that they were Huronian (see ante,
pp. 106, 108), but gives as the result of his studies in 1882 the view
that

“they occupy the geological interval elsewhere filled by those divisions of the
great lower paleozoic system which underlie the Trenton group. Various
considerations point to the Potsdam and Primordial Silurian (Lower Cambrian)
as their nearest equivalents. .... They are essentially volcanic, sub-aerial,
and sub-aqueous formations, and in every sense analogous to the wide-spread
tertiary volcanic rocks of Australia and other regions. The only differences
are their greater antiquity and the consequent greater changes and modifica-
tions they have undergone through the operation of long-continued metamor-
phic agencies, disturbance, and denudation ; though these changes are far less
than those which rocks of the same age, and to some extent similar origin,
have undergone in eastern America and in Britain.” (Science, 1883, I., pp.
11, 221.)

It is obvious that these views are identical with those published by
Foster and Whitney in 1850. (Ante, pp. 76-131; see also Science,
1883, I., p. 39.)

MICHIGAN AND WISCONSIN. 489

Professor Irving in reply to Mr. Selwyn stated that “the copper-
bearing rocks underlie unconformably — and with an immense uncon-
formity —a series of sandstones holding Cambrian fossils.” He further
remarked “that the copper-bearing strata also underlie unconformably
the eastern sandstone of the south shore of the eastern half of Lake
Superior.” He also complains that the evidence of himself, Sweet, and
Chamberlin regarding the Taylor’s Falls locality had been ignored by
others. (Science, 1883, I., pp. 140, 141, 359, 360, 422.)

It was in reply immediately pointed out by Dr. Wadsworth, that
the above-mentioned observations had neither been ignored nor denied ;
but that the trouble was that the Wisconsin geologists themselves
had ignored the simplest principles of the geology of eruptive rocks,
which they themselves admit these to be. (Science, 1883, I, pp. 248,
249.)

In the mean while Dr. Hunt stated that the

“view of the continuity of the cupriferous series with the Potsdam (St. Mary)
sandstone was maintained by Whitney ; but Logan, in 1863, put forth strong,
and to most minds conclusive, reasons for believing that the highly inclined
cupriferous rocks at the east end of the lake pass unconformably below this
sandstone.” (Science, 1883, I., pp. 218, 219.)

It was then pointed out by Dr. Wadsworth, that

“the evidence advanced by Logan, which Dr. Hunt finds so convincing, was
mainly a difference in dip between the traps and sandstones at localities several
miles apart ; and that all the evidences, as Logan himself says, only ‘seem to
support the suspicion that the sandstones may overlie unconformably those
tocks, which, associated with the trap, constitute the copper-bearing series.’ ”
(Science, 1883, I., p. 307.)

Prof. N. H. Winchell then, in agreement with Foster and Whitney,
and with Selwyn, remarked with reference to the statements of the
latter : —

“T concur with him in the sweeping affirmation, ‘ that there is, at present,
no evidence whatever of their [the cupriferous rocks] holding any other place
in the geological series’ than that of the ‘Potsdam and primordial Silurian’;

and I would also add, that there is much incontestible evidence that they can
hold no other.” (Science, 1883, I., p. 334.)

Later, Prof. T. C. Chamberlin summed up the various reasons for
supposing that the Keweenaw rocks were distinct from the adjacent
sandstones. They were: the different stratigraphical relations ; differ-
ences in thickness and in constitution; unconformity; the inherent

490 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

consistency of this view ; the dynamic simplicity of this view ; and the
discovery by the United States geologists of a like series in the Grand
Caiion of the Colorado. He in no wise meets the direct evidence pre-
viously given, that the sandstone and traps are one and the same forma-
tion, while his arguments ignore the mode of formation, i. e. they would
be of value only if both the eastern sandstone and the copper-bearing
rocks were of exclusively sedimentary origin. (Science, L, pp. 453-
455.) ©

Since so’ much has been claimed for the Taylor’s Falls locality, it will
be necessary to pay some attention to the connection of this with the
known copper-bearing rocks of Michigan. Beginning at the Nemakagon
district, some granites and diabases are found on opposite sides of the
Nemakagon River. A thousand feet below is more diabase. About 250
yards south is a small exposure; then, about 100 yards west, another.
Four miles northeast is to be found a series of diabase ledges extending
for a quarter of a mile. About twelve miles northwest of this is a belt

“nearly thirty miles in length, over which are scattered, in comparative pro-
fusion bare or slightly concealed ledges... .. With two exceptions — viz., a
sandstone and a conglomerate — the series is formed of trappean rock, mainly
diabase and diabase-amygdaloid.”

After passing over an intervening space of about thirty-six miles, dia-
base and quartz porphyry were met with in the Clam Falls district.
From this locality on there is a series of outcrops varying from one
fourth of a mile to about five miles apart, extending to the Taylor’s
Falls region (St. Croix district). (Geol. Wisc., 1880, III., pp. 399-415.)

We see then that these rocks, according to the testimony of the Wis-
consin geologists, have been mainly determined on lithological evidence,
and that when any outcrop of a diabase or melaphyr was found it was
placed without question in the Keweenawan series. Again, these out-
crops are widely separated by drift-covered regions, and thus far the
Wisconsin geologists have not advanced the slightest proof that the
St. Croix diabase is the same as the Michigan lava flows. .

Dr. Owen stated in regard to this locality, that the trap had

“forced its way through highly fossiliferous strata, breaking up the beds im-
mediately overlying it, entangling and partially indurating the fragments,
without, however, tilting or metamorphosing the adjacent beds in any percepti-
ble degree. The fossils, even of the beds almost in contact with the trap
dykes, are in a perfect state of preservation, and the strata themselves have no
dip perceptible to the unassisted eye in the hillside where they are exposed.”
(Geol. Surv. Wise., Iowa, and Minn., 1850, pp. 164, 165.)

MIULHIGAN AND WISCONSIN. 49]

In a foot-note Dr. Owen also states that the remains of the shells
can be “ detected in fragments enclosed in the trap, and so much al-
tered as to be distinguished with difficulty from the surrounding green-
stone.” It seems hardly possible that Owen conld have made these
statements if part of the trap at least was not intrusive in the sand-
stone.

Mr. J. H. Kloos (Zeits. Deutsch. Geol. Gesells., 1871, XXIIT., pp. 417-
448 ; Geol. Minn., 10th Ann. Report, for 1881, pp. 175-200) states that
he found the sandstone horizontally overlying the trap, or diabase as we
—in agreement with Rosenbusch — should prefer to call it. He also
observed a conglomerate made up of the ruins of the diabase ; but the
relations of the conglomerate to the sandstone were not ascertained.

Prof. N. H. Winchell claims that the sandstone in this locality is not
the Potsdam, but belongs to a higher formation. This view he holds
on account of the physical characters of the rock, as well as differences
in the fossils it contains. (Geol. Minn., lst Ann. Report, pp. 68-80.)
Later, Professor Winchell considered the St. Croix sandstone as belong-
ing to the Quebec group, and as overlying the Potsdam sandstone, to
which latter he referred the copper-bearing rocks of Keweenaw Point.
(Geol. Minn., 10th Ann. Report, pp. 123-136.)

_ From what has been given it can readily be seen that Messrs. Irving
and Chamberlin have failed to recognize the simplest features of the
geology of mixed eruptive and sedimentary rocks ; and that the condi-
tions upon which they place so much reliance to prove the correctness
of their views are exactly those which occur (excepting the presence of
fossils) whenever a sandstone or conglomerate is found intercalated in
the copper-bearing series. If their evidence is good, then we have
“proof absolute” that the Keweenawan series— the copper-bearing
rocks —is composed of as many distinct geological formations as there
are beds of sandstone and conglomerate intercalated in them. So far as
their yet published work goes, all their evidence has not advanced one
step beyond that which was made known thirty-three years ago, and it
is strictly in accord with the views of Foster and Whitney as then
stated. Were this not the case, there is as yet not the slightest pub-
lished evidence that the St. Croix traps belong to the copper-bearing
series: they may be older or younger, while considerable evidence is
given by Professor Winchell to show that the sandstone there is more
recent than the Potsdam. Moreover, there is positive evidence that
the copper-bearing rocks are part of the Eastern sandstone formation on
Keweenaw Point. It seems, then, that the Keweenawan series owes

492 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

its origin and perpetuity in part to erroneous observations, and in part
to erroneous deductions from correct observations.

Prof. N. H. Winchell, in his Report for 1881, gives a summary of the
geological opinions held regarding the copper-bearing rocks, which sum-
mary he appears to have made up with additions, but without acknowl-
edgment, from that previously given by Dr. Wadsworth (ante, pp. 107-
109), using also the more complete exposition of views presented on
pp- 76-107. For an authoritative expression of Dr. Wadsworth’s views
he does not refer to this work (pp. 1-157), which was at that time in
his hands, but to a brief abstract only. (Proc. Amer. Assoc. Ady. Sci.,
1880, XXIX., pp. 429, 430.)

In the article previously referred to (this Bulletin, pp. 1-76), it was
claimed by Dr. Wadsworth as the result of an examination of the litera-
ture relating to the Azoic region of Michigan, together with a consider-
able amount of study both in the field and in the laboratory with the
aid of the microscope, that, in accordance with the early published views
of Foster and Whitney, the granite was eruptive, as were the green-
stones (diabase, melaphyr, etc.), part of the iron ore and Jaspilite, the
peridotite, etc.; and that these eruptive rocks, united with the sedi-
mentary ones, made up the Azoic system; while there was no evidence
existing to show that this formation could be separated into two divis-
ions. It was pointed out that, in the subsequent Survey of the Lake
Superior region by Messrs. Brooks and Pumpelly, great ignorance of the
simplest principles of geology and lithology had been displayed, and
that no confidence could be placed in the results at which they professed
to have arrived.*

We now pass to the consideration of some later publications relating
to the Azoic rocks of Michigan.

In 1881, the fourth volume of the Report of the Michigan Geological
Survey, by Dr. C. Rominger, was published. The author of this Report
appears to have known nothing of the work of others, excepting that of

* It might further have been shown that, although Major Brooks professed in his
Report to give a history of the scientific exploration of the Iron District of Lake
Superior, he entirely ignored the work of Messrs. Foster and Whitney, by whom that
region was first geologically mapped, and the important localities of iron ore laid
down. It might also have been shown that the geological map of the Lake Superior
region published by Messrs. Brooks and Pumpelly was, to a considerable extent, a
copy of that of Foster and Whitney, and that not the slightest acknowledgment was
made for thus incorporating into their own work the geology of extensive areas
which had never been examined with any detail either by themselves or by their
assistants.

MICHIGAN AND WISCONSIN. 493

Mr. T. B. Brooks ; consequently numerous statements are put forth by
him as original, when in fact they had been previously published by
others. Had Dr. Rominger been more conversant with the literature
of the district, many errors into which he has fallen would have been
spared him, since he is essentially a paleontologist. However, he ap-
pears to have worked conscientiously, aud to have endeavored to ascer-
tain the truth so far as he could.

Regarding the so-called Laurentian granites, Dr. Rominger states : —

“ According to my own observations the granites of Marquette are eruptive
masses which came to the surface after the Huronian beds were already formed,
and by their eruption caused, not only the great dislocations of the Huronian
formation, but the half molten plastic granite masses induced by their contact
with the Huronian rock-beds, also their alteration into a more or less perfect
erystalline condition, and commingled with them so as to make it an embar-
rassing task to find a line of demarcation between the intrusive and the in-
_truded rock-masses.” (J. c., p. 6.)

He also points to the fact that lamination is no proof of stratification,
stating that he had “in several instances seen narrow intrusive granitic
dyke-masses similarly laminated by the parallel arrangement of the’
mica scales in them.” (/. c., p. 16.)

Dr. Rominger further proceeds : —

“The granites, considered in their present surface position, are, in relation
to the stratified sedimentary rocks of the Huronian series, actually the younger
rock, so far as the intrusion of very large masses of granite between the strati-
fied sediments can be demonstrated by clearly observable facts, and as the
other larger bodies of granite inclosing them [the so-called Huronian schists]
from two sides are in direct continuity with the vein granites, and lithologi-
cally identical with them.” (J. c., p. 22.)

While Dr. Rominger regarded part of the basic rocks as truly erup-
tive in the form of dikes and lava flows, he recognized also the intrusive
nature of much of the remainder ; but being unable, from lack of litho-
logical training, to distinguish between the older eruptives and their
associated schistose rocks, he — like Mr. Brooks — confounded them to-
gether, and adopted for explanation the following theory, difficult of
comprehension, and certainly not at all consonant with the facts ob-
served in the district, the difficulty lying with the observers, and not
with the rocks : —

“From such a standpoint, the various crystalline hornblende rocks found in

association with the granites could be considered as remelted, completely
metamorphosed, Huronian sediments, on account of their nearest proximity to

494 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

the volcanic focus, while those more remote from it did not altogether lose
their sedimentary structure, but still became altered, and frequently streams
of the lower melted or emolliated plastic masses broke through them, filling
transverse ruptures or entering between the ledges parallel with the bedding.”
(i. ¢., p. 23.)

The rocks thus united Dr. Rominger classed as the “ Dioritic Group.”
He showed, as Dr. Wadsworth had already done, the incorrectness of
Major Brooks’s work, and how little reliance could be placed on his con-
clusions.

Dr. Rominger appears to have found in the Menominee iron region a
condition of things very similar to that existing in the Marquette dis-
trict, and arrived at similar conclusions. (/. c., pp. 240, 241.) His idea
that the Marquette and Menominee schists are Huronian means nothing
beyond this, that they appear to him to be lithologically similar to the
rocks called Huronian in Canada; while — so far as his actual work
goes — he reaches conclusions regarding the relation of the granitic and
schistose rocks identical with those advocated by Foster and Whitney
thirty years before. The result of Rominger’s work is decidedly opposed
‘to the division of the Michigan Azoic into two or more formations.

The question of the origin of the iron ores was not only discussed in
the previous portion of this Bulletin, but also elsewhere. (Proc. Bost.
Soc. Nat. Hist., 1880, XX., pp. 470-479.) The following indorsement
of these views, with permission to publish it, was received from Mr. A.
R. C. Selwyn : —

“T believe with you that many of our great Archean iron-ore beds are of
eruptive origin, while others are stratified iron-sandstones, analogous to those
which are now forming along the northern coasts of the St. Lawrence Gulf by
the combined action of the rivers and the waves on the more ancient (probably
eruptive) ore beds. But such magnetic ores always contain from 40 to 50 per
cent of insoluble matter (probably chiefly silica), a much larger proportion
than those which are presumably of eruptive origin.”

Professor Dana, in opposition to the view of the eruptive origin of the
iron ore and jaspilite, claims that conformability is the evidence used
principally in deciding that the ores and schists are alike in their mode
of origin. He also attempts to decide the point by appeals to other
regions. It seems to us that the origin in each region is to be proved
by the study of the district itself, and that arguments from analogy
when used alone are fatally defective.

The question of conformability was the one examined, and upon
which the decision regarding the origin of the iron ore was made. A

MICHIGAN AND WISCONSIN. 495

careful examination of the literature showed that there was no published
evidence of more than a superficial study of the relations of the ore to
the associated schists; but all was based on theoretical views. Now
the examination described previously was made for the express purpose
of determining the relations of the ores and schists, without regard to
any one’s views. It showed that — wherever their relations could be
determined — they were those of an eruptive rock in contact with a
sedimentary one. These things were described and figured, and no one
has yet attempted to meet the evidence, either to deny it or explain it
away.

Two other attempts to discredit this view, besides that of Dana, were
made. One was by Prof. J. S. Newberry, who, being evidently unable to
meet the evidence given, contented himself by remarking that ‘‘to be
asked to believe that.the ore sheets are intrusive is a greater strain
upon my credulity than it can endure.” In other words, he takes espe-
cial pains to show that scientific questions are with him merely a matter
of theoretic belief, and not one of evidence and facts. (‘The Genesis
of our Iron Ores,” School of Mines Quarterly, Nov., 1880, p. 8.)

The second attempt was made by Dr. A. A. Julien, who likewise
ignored the evidence, and confined himself to saying, “ The mineralogical
constitution and infusibility of these ores, their distinctly sedimentary
lamination, etc., clearly testify to the unsoundness of these hypotheses.”
(Proc. Phila. Acad. Nat. Sci., 1883, pp. 335-346 ; Trans. N. Y. Acad.
Sci., 1882, II., pp. 6-8, 13-17.) If these ores are regarded as an extru-
sion from the molten interior of the earth, their mineralogical constitu-
tion and infusibility have no bearing upon the question ; but, on the
other hand, if they are of sedimentary origin Dr. Julien must explain
how it was that later they became plastic, so as to become intrusive, as
they plainly are. That they are distinctly sedimentary in their lamina-
tion, or that the jaspilite is a fine silicious sand, we deny. Messrs. Ju-
lien and Newberry both show in their writings that they have not made
themselves acquainted with the mode of occurrence of the Marquette
iron ore, either by observations in the field, or by study of the published
descriptions. Dr. Julien’s paper is especially replete with errors.

Passing now to the Azoic rocks of Wisconsin we find that in 1876
Mr. E. T. Sweet pointed out a supposed unconformability between the
Laurentian and Huronian at Penokee Gap, stating (Trans. Wisc. Acad.,
1875-76, IIL, pp. 43-44) : —

“When the railroad cut is completed at this locality, the absolute junction
of Laurentian and overlying Huronian will doubtless be exposed. There can

496 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

be no doubt of the unconformability of these formations, approaching each other
as they do with a persistent opposite dip and somewhat different strike. Un-
conformability has been shown to exist between the Laurentian and Huronian
in Michigan, but this is the first time it has been proven in Wisconsin.”

Of the same supposed unconformability at Penokee Gap, Prof. R. D.
Irving remarks (Am. Jour. Sci., 1877, (3) XIIL, p. 308) :—

“The crystalline rocks of Wisconsin include unquestionably two distinct
terraces, the one lying unconformably upon the other, as is beautifully shown
at Penokee Gap, on Bad river, in the Lake Superior country. Here a white
siliceous marble of the Huronian, overlaid by hundreds of feet of distinctly
bedded slaty rocks, and dipping northward, is to be seen within twenty feet
of large ledges of dark colored amphibolic gneiss, whose bedding planes dip
southward and strike in a direction diagonally across that of the more northern
beds. There are no doubt instances where the two series are difficult to sepa-
rate, similar rocks occurring in both groups, but the existence of the two is
incontestable.”

In the third volume of the Geology of Wisconsin (pp. 94, 98, 108,
116, 117, 248-250) accounts of the unconformability of the Laurentian
and Huronian are given, but the kind of contact when seen was not
observed. But if the Laurentian rocks are eruptive, then of course there
would be unconformability. The proof advanced was, that the folia-
tion of the granite and gneiss dipped at a different angle from that of
the Huronian rocks. Here, as in the case of the Keeweenaw series, the
Wisconsin geologists failed to take into account the conditions neces-
sary to prove their points; while Professor Irving, without giving any
evidence of value, made out a beautiful fault — on paper — at the Peno-
kee Gap. So far as can be judged from the evidence presented by these
geologists, it appears that they have in Wisconsin the same structure as
exists in the Azoic of Michigan, namely, a series of mixed sedimentary
and eruptive rocks.

From the following extracts it will be readily seen that there are no
other than lithological grounds for assigning these rocks to the Huro-
nian and Laurentian: that they are two distinct formations they en-
tirely fail to prove.

Major T. B. Brooks states (Geol. of Wise., 1880, III., p. 468) :—

“No rocks affording to me the slightest suggestion of a conglomeritic struc-
ture have been found in the Laurentian system, its rocks being always highly
metamorphosed, and often so much so as to destroy all traces or suggestions of
bedding.”

In the same report (p. 531) Mr. Brooks also points out several areas
of granite in which this rock was found to be intruded into the supposed

MICHIGAN AND WISCONSIN. 497

Huronian. There seems not the slightest reason to regard this as any-
thing different from the so-called Laurentian granite, and this strength-
ens the probability of the view that the so-called Laurentian granite is
really eruptive in the so-called Huronian. (Avte, pp. 22, 70, 71.)

In 1880, Professor Irving gives as the reasons for assigning the rocks
which are placed in the Laurentian in Wisconsin to that system, their

“ close lithological similarity — the only marked difference being the absence
of crystalline limestones in the Wisconsin area — of similar structural relations
to the Huronian, Keweenawan, and Lower Silurian systems, and of probable
direct continuity with the Canada Laurentian through the upper peninsula of
Michigan and underneath the waters of Lake Superior.” (Trans. Am. Inst.
Min. Eng., 1880, VIII., pp. 480, 481.)

Of the Huronian in the same article it is stated (p. 483) : —

“The rocks of this series have been called Huronian by Brooks, and, in the
writer’s judgment, correctly so, on account of their similarity to the Canada
Huronian, with which they not improbably have a direct connection under-
neath the Silurian of the eastern part of the peninsula, but more especially
because they evidently occupy the same geological interval as the typical
Canadian series, exhibiting the same non-conformity with an underlying
gneissic and granitic system.”

It appears, then, that the only evidence that the Wisconsin geologists
have that the Laurentian and Huronian are what they purport to be is
lithological ; and they have advanced no sound argument showing that
they form distinct ages in the Azoic System. The relation of the two
supposed series is not that which is seen when the Paleozoic comes in
contact with the Azoic, or what it would be naturally were the Huro-
nian laid down on the pre-existing Laurentian. The contacts — when
these contacts have been figured — appear rather to be those made by
eruptive rocks with prior existing ones. The geologists before men-
tioned have assumed, not proved, the sedimentary metamorphic origin
of all the rocks in question, and on the correctness of that assumption
depends their argument. They have failed to observe the phenomena
of the contact, when seen, beyond the mere fact of a differeut dip to
the foliation observed. In fact, they have failed to prove any of the
points essential to establishing their conclusions.

Later, Irving advanced, as if original with himself, the view that the
so-called greenstones or diorites of the Marquette district were eruptive,
and that the hornblende was secondary after augite. This too when
the portion of this Bulletin relating to the Iron and Copper districts of
Lake Superior (ante, pp. 1-157) had been sent him, in 1880, at his own

VOL. VII.— No. 11. 32

498 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

special request. Although professing to indicate the microscopic work
which had been previously done, he ignores completely that given in the
pages before mentioned, which anticipated him in almost every point.
(Am. Jour. Sci., 1883, (3) XXVL, pp. 27-32, 155.)

In 1866 Prof. James Hall referred some gneiss and granite on the
Redwood River to the Laurentian, and some quartzites in the valley of
the Minnesota River to the Huronian. ‘This was done solely on litho-
logical grounds, while the two series of rocks were not seen together.
(frans. Am. Phil. Soc., 1869, (2) XIII., pp. 329-340.)

It would seem that Dr. F, V. Hayden held that the quartzite was
most probably supra-Carboniferous, Triassic, or possibly Cretaceous.
This was on account of fossils which were found in some quartzite in
the adjacent region. (Am. Jour. Sci., 1867, (2) XLUL., pp. 15-22). Part
of Professor Hall’s views were regarded as untenable by Prof. N. H.
Winchell. (Bull. Minn. Acad. Sci., 1874, pp. 100, 101.)

In 1872 Prof. N. H. Winchell divided the “ granitic and metamor-
phic rocks” extending across Minnesota from the northeast to the
southwest into Laurentian and Huronian; on what grounds does not
appear. (Report on the Geological Survey of Minnesota, 1872, pp. 64—
67.)

In 1880, in the Report of the Geological Survey for 1879 (p. 26),
Professor Winchell remarks : — ;

‘‘We hence see the Potsdam in its extension to Duluth involved with these
igneous rocks, in upheaval and metamorphism, and cannot resist the conviction
that the whole series known as the Upper Copper Bearing Rocks, or as the
Keeweenian, or as the Quebee Group, on different authorities, was correctly
assigned to the Potsdam at first by Messrs. Foster, Whitney and Hall in 1849,
and subsequently by D. D. Owen.”

The evidence on which he relies in making this statement is the fact
that the copper-bearing rocks at Duluth are seen to be continuous with,
and to form part and parcel of, the Potsdam sandstone as it extends
from that point into Wisconsin. This view of Professor Winchell’s
harmonizes with that which has already been shown by us to exist in
Michigan. The Minnesota geologists have not furnished any evidence,
other than that based on lithological resemblances, to uphold the divis-
ion of the Azoic system into the two series Huronian and Laurentian.
Moreover, it seems to be the fact that in this State, as well as in Michi-
gan, the supposed Keweenawan is nothing more than Potsdam.

THE FORTIETH PARALLEL SURVEY. 499

THE FORTIETH PARALLEL SURVEY.

The results of the Fortieth Parallel Survey, in so far as the geological
and lithological investigations are concerned, will be chiefly found in
the first, second, third, and sixth volumes of the series of publications
of that Survey. These volumes will be referred to in the following
pages simply as I., II., III, and VI.

The first of these, in the order of publication, is Volume III. This
bears the title of ‘ Mining Industry,” and is chiefly devoted to practical
matters connected with mining and metallurgy. It is therefore of
minor importance to us in connection with our present inquiry.

The second in order is that of Professor Zirkel, Volume VI., bearing
the date of 1876. This volume is devoted to setting forth the results
of a microscopical examination of the lithological collections of the Sur-
vey. The next is Volume II., containing the descriptive geology, by
Messrs. Emmons and A. Hague. This volume comprises the whole
geological work of the Survey, discussed in a geographical order. It
bears the date of 1877 on the title-page. Volume I, by Mr. King,
entitled ‘Systematic Geology,” was issued last of all, in 1878. It
contains, as its title imports, a systematic discussion of all the geologi-
eal, lithological, and chemical investigations of the Survey, treated in
chronological order, or in that of the geological age of the formations.
In the present necessarily brief examination of that part of the work of
the Fortieth Parallel Survey which is connected with the subject of the
present paper, the relation between Volumes I. and II. should be borne
in mind, and will be best understood on reading the following statement
by Mr. King :—

“« The purpose of this volume [I.] is to present, as briefly as possible, a sys-
tematic statement of the data collected, and the induction we have been able
to make. In Volume II. will be found a continuous description of the geo-
logical facts observed, treated geographically. ... . Whoever wishes to know
the structure and details of given features should consult that volume.”

In the first place it will be noticed that Mr. King begins his volume
with the consideration of what he calls the “ Archean.” Nothing being
said in the way of defining what is meant by this term, it would natu-
rally be supposed that it was employed with the same meaning as that
intended by Professor Dana,* by whom the name Archean was intro-

* See, in reference to this point, farther on, page 547.

500 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

duced into geology as the equivalent of the Azoic of Foster and Whit-
ney. By them this latter term was used to designate the rocks which
had assumed their present position prior to the deposition of the low-
est member of the Lower Silurian.* Thus, for instance, in accordance
with this view, granite erupted after the Jurassic epoch could not be
called Archean. It does not appear, however, that Mr. King had this
idea clearly present in his mind while writing the volume in portions ;
at least, this is the result to which an examination of the work leads us.
In fact, at the beginning of the chapter headed “ Archzwan,” he says : —

“ At intervals over the whole mountainous area west of the 100th meridian,
masses of gneiss or crystalline schists, with their associated marbles, dolomites,
and quartzites, and eruptive bodies of granite, porphyries, gabbros, &c., are
found to underlie more recent strata.”

The rocks here mentioned he then immediately proceeds to desig-
nate as “these Archean bodies,” without any limitation as to their
geological age.

In order, therefore, that we may ascertain how far there is evidence
justifying the calling of these various “ bodies” Archean, according to
the original geological meaning of that term, it is desirable that we
should take up some of the more important regions where this “ Ar-
chean ” occurs, and examine briefly the evidence by which its geological
age has been established.

The first supposed Azoic (Archzean) rocks with which we have to do
are those of the Colorado (Laramie) Range. The rocks of this range
are granites and gneisses, with a very little mica schist (I., p. 22). It is
evident that Messrs. King, Emmons, and Hague in general regard as
a gneiss any granitoid rock which possesses in the slightest degree a
parallel arrangement of its constituent minerals. It is also evident
that in most cases they call this condition stratification.

Regarding this range we find no proof advanced that the granites and
gneisses are stratified, and not eruptive, except the foliation above men-
tioned. Since it may be claimed by some that Professor Zirkel by his
microscopic observations proved these and other granites to be of meta-
morphic sedimentary origin, it is perhaps well to look at his evidence.
He distinctly states (VI., p. 59) that the diagnostic characters that he
has given as distinguishing metamorphic, older eruptive, and younger
eruptive granites from one another, “are valid only for the examined
rocks of the Fortieth Parallel, and that it is not allowable to generalize
from them for other countries.” From this it is evident that these

* See Dana’s Manual of Geology, 2d ed., 1875, p. 148.

THE FORTIETH PARALLEL SURVEY. 501

characteristics were not the result of any previous study, but solely of
the investigation of these particular rocks. Since Professor Zirkel
never studied the rocks of the Fortieth Parallel Survey in the field, and
since these diagnostic characters were obtained from those rocks only,
how was it possible for him to know which were metamorphic, which
older eruptive, and which younger eruptive granites ?

Mr. King states that the supposed Archzean rocks were proved to
be of that age, not only by their lithological characters, but also by
their being seen in contact with the Potsdam and some presumably
Cambrian rocks. These contacts were not within the limits of the For-
tieth Parallel Survey, and he gives us no information in regard to their
characters. (I., p. 21.)

Mr. Hague’s statement, however, goes to show that in point of fact
these rocks were upheaved in some parts since the Triassic ; in others,
since the Jurassic; and in others, since the Cretaceous (II., pp. 6-93).
This demands that one of two theories should be adopted ; either that
these rocks were pushed up in a solid body, or that they were eruptive.
In the former case, they are regarded as ancient land bodies, about
which the later formations were deposited, all being subsequently up-
lifted by the granite upthrust. We fail to find any evidence in the
publications of the Survey that examinations were made to see if the
later formations (except the Tertiary and Cretaceous) contained débris
from the supposed Azoic (Archean) ; or to ascertain whether the con-
tacts were those of one rock laid down upon another, or eruptive,
or such as would naturally occur in case a solid mass was thrust up
through another. In fact, no evidence in regard to these points is
adduced, except the statement that the supposed later formations lie
unconformably against the Archean, which unconformability would ex-
ist in any of the before-mentioned cases. Had evidence been seen, we
cannot imagine it would have been passed over in silence. So far as
this district is concerned, the oldest rocks in contact with the granitic
rocks are of Carboniferous age. The supposed Azoic rocks are con-
sidered to be Laurentian on the strength of lithological resemblances,
and they are also said to constitute one formation. In the district in
question, however, it is impossible to prove them to be older than the
Carboniferous ; and by neglecting to give the evidence, if any existed,
they are not shown to be older than the beginning of the Cretaceous.
(ep. 299.)

_ The gabbro of this range, which, according to Dr. Hunt, has the char-

acters of the Norian (Proc. Bost. Soc. Nat. Hist., 1878, XIX., p. 276),

502 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Mr. King says is eruptive through the granites (I., p. 27), while Mr.
Hague makes the same statement (II, p. 13). If this gabbro is
Norian, and Mr. King is correct in stating it to be eruptive through the
Laurentian granites, it follows that the Norian formation is older than
the Laurentian ; or else that the supposed Laurentian granites are not
of that age, — that is, if we are to accept the theories of Dr. Hunt and
some of his followers: he, however, holds that the granite (gneiss) of
the Colorado Range is Laurentian. (J. ¢., p. 276.)

The Medivine Bow Range is referred by Mr. Hague, “ with consider-
able hesitation,” to the Huronian, and this reference is said to be “ based
entirely upon lithological evidences.” Part of the rocks are sedimen-
tary ; but a large portion regarded by Messrs. King and Hague as sedi-
mentary has not been proved by them to be so. The question still
remains, therefore, How much of the supposed Huronian characters is
due to eruptive agencies and their concomitants, and how much to geo-
logical age? The evidence advanced by Mr. Hague shows that the
upheaval of the range was not completed until at least as late as the
Cretaceous epoch, while, in fact, no proof is given that it is older than
Tertiary. It was seen in contact with no rocks known to be older than
the Triassic, although beds supposed to be of Carboniferous age were
observed in one locality. The kind of contact formed by these Huronian
rocks with the supposed later ones was not noted; neither do we have’
any information given that débris from the Huronian were found in the
other formations, until high up in the Tertiary. Had such débris been
observed it unquestionably would have been mentioned, since not only
here, but in the Colorado Range, the occurrence of such material is no-
ticed in the Tertiary.

The supposed Huronian formation has not then been proved to be older
than the beginning of the Tertiary, and in the present state of geologi-
cal science it is impossible, if the age of the other formations has been
correctly determined, to prove it older than the Carboniferous. We do
not find any evidence given that the uplift of the Park Range took place
prior to the Cretaceous ; there being here the same absence of proof as
was indicated in the case of the two preceding ranges. In this case,
however, no rocks older than the Triassic were found in contact with
the supposed Archean, and yet the range —on lithological grounds,
purely —is assigned to the Laurentian. The evidence in regard to
Rawling’s Butte seems to be the same as that relating to the Park
Range, through the Archean schists of which Mr. Emmons remarks
that basalt is seen to have been erupted.

THE FORTIETH PARALLEL SURVEY. 503

The next series of supposed Archean rocks is in the Uinta Range.
The rocks there, according to Mr. King, are quartzites and hornblendic
and hydro-mica schists. Another quartzite unconformably overlying
it, and said to contain fragments of the Archzean (I., p. 154), is referred
with doubt to the Carboniferous. Im some places the Archean gives
evidence of having been uplifted since the Fox Hill Cretaceous (II.,
p- 268). Mr. Emmons, it seems, would refer these rocks to the Huro-
nian on account of their lithological characters.

The Wahsatch Range was regarded as the type of the Archzean (Azoic)
exposures in the district covered by Mr. King’s survey. It is, how-
ever, more difficult to make out from the writings of Mr. King and
his coadjutors what they believe its history to have been, than it is to
learn their ideas of any of the other districts within their field of ex-
ploration. It would also seem that in some places their views regarding
the origin of the granites, and the geology of the Wahsatch Range, in
general, had decidedly changed during the time which elapsed between
the publication of Volumes VI. and I.; Volume II. representing the
later transition period, with a still greater change since Volume III. was
published. In order to give some idea of the views of Messrs. King,
Emmons, and Hague, it is necessary to quote to some extent from their
writings, as well as from Volume VI.

At the time of the publication of Volume III. (1870), it seems Mr.
King held that the granites were all of eruptive origin, and of Jurassic
age ; while the stratified rocks in his district were regarded as conform-
able from ‘‘the early Azoic up to the late Jurassic period.” In that
volume Mr. King says (III., pp. 2, 3) of the region covered by his
Survey .: —

“The greater part of the rock is a series of conformable stratified beds,
reaching from the early Azoic up to the late Jurassic period, when these level
beds were compressed into vast mountain corrugations and elevated above the
sea in a general, wide, and high plateau. Accompanying the upheaval and
crumpling of this great oceanic family, and bursting from its fractured folds,
are important masses of granite, penetrating the axes of the flexures and break-
ing through lateral fissures. Quartz-porphyries, felsite rocks, and notably
syenitic granite, with occasional occurrences of granulite and greisen, ac-
company the ejections of granite. The date of their orographical period is
assigned to the late Jurassic on grounds which will be found fully discussed
in the first volume of the present series... . . This Exploration has demon-
strated that all the parallel ranges of the Great Basin, including the chain
of the Wahsatch, tts eastern wall, belong to the same system [Jurassic] of
upheaval.”

504 THE AZOIC SYSTEM AND ITS SUBDIVISIONS,

Not only were the grounds on which the Jurassic age was assigned
to the granite not subsequently discussed, but in point of fact an entire
change of view took place previous to the publication of Volume I., the
reason for this absolute reversal of opinion in regard to a fundamental
point in the geology of the Cordilleras being nowhere given, and —
what is still more inexplicable — no allusion being made to it.

Mr. Emmons, in describing part of the same range (the Wahsatch),
states (IL, pp. 355, 360-363, 365) : —

“ A body of Archzean slates and granite is surrounded, and partly covered,
on all sides except the west, by a conformable series of sedimentary rocks, of
an agerezate thickness of over 30,000 feet, extending in age from the Cambrian
to the Jurassic inclusive. The granite mass, though eruptive, has not been
protruded through this immense thickness of overlying rocks, but their beds
were deposited around and over a submerged mountain-range of granite sur-
rounded by Archean rocks ; and subsequent elevation, flexure, dislocation,
and erosion have produced the conditions represented on the map, where it
will be seen that of this conformable series, now bent and twisted, different
horizons from the Cambrian up to the Middle Coal Measures are at different
points in contact with the granite body. Of the immense arch which once
covered this body, the western half has been faulted down, while the top of
the arch, with its thickness of 30,000 feet of rock masses, has been broken up
and worn away by atmospheric agencies. . . .. In Big Cottonwood Caion,
.... isasmall exposure of granite. ... . It is difficult to say whether this
rock should be considered as part of the main granite body, which it does not
resemble very closely, or with the later outbursts of granite-porphyries and
diorites, which are found intersecting the sedimentary rocks of this region.
These dikes of porphyry and diorite are very frequent, especially around the
Clayton Peak mass and in the region where the mineralization of the beds has
been most developed. . . . . Near this granite or diorite body of Big Cotton-
wood Cafion, in one of the beds of the upper part of the Wahsatch limestone,
is a dike about 20 feet wide, of syenitic granite-porphyry, so classed by Zirkel,
which resembles the granite in general appearance. . .. .

‘‘The Paleozoic beds of this region, which fold around and partly cover the
granite body, have been subjected to intense compression and local metamor-
phism, twisted and contorted in every direction, faulted and dislocated, and
penetrated by intrusive dikes and mineral veins. .... The great belt of
Wahsatch limestone, which forms the main stratigraphical landmark in these
formations, . . . . forms massive cliffs at the southern head of Little Cotton-
wood, and here already, in the mantling of white, through its general blue
color, shows the commencement of the metamorphism which has marbleized
its beds in great degree from here to the mouth of Mill Creek Cafion, where
they disappear beneath the Salt Lake plain. This belt includes, as has
already been stated, the three groups of Lower Coal-Measures, Sub-Carbon-

— a

THE FORTIETH PARALLEL SURVEY. 505

iferous, and Nevada Devonian. .... Between Little Cottonwood and Amer-
ican Fork ... . all these beds standing at high and varying angles, and being
much broken and contorted.”

In Volume I. Mr. King remarks (pp. 44-48) : —

“The Archean rocks in the explored portions of the Wahsatch are exposed
at intervals along the west front of the range for nearly 100 miles, and are
composed of granites, garnet rocks, aplitic schists, and a very extended series
of gneisses and hornblendic schists, with subordinate quartzites, The man-
ner of their exposure is of very great interest, involving the most extensive
dynamic action observed within the limits of the Fortieth Parallel Exploration.
The chain of out-crops clearly represents an old Archean range of bold con-
figuration, which has been buried beneath an enormous accumulation of
Palzozoic and Mesozoic sediments. It was this buried Archean range which
controlled the position and direction of the modern Wahsatch Range. After
the uplifts took place, and the Palaeozoic and Mesozoic strata were thrown into
their present inclined position, a great longitudinal fault occurred throughout
this whole portion of the range, by which the entire western half of the ridge
was thrown downward from 3,000 to 40,000 feet, and is now entirely buried
beneath the Pliocene and Quarternary formations of the Salt Lake basin. The
present abrupt west front of the Wahsatch is the standing face of this great
fault, and here the Archean rocks are seen to occupy the core of the range,
unconformably underlying the Paleozoic series, and rising to different strati-
graphical horizons in the overlying series. In the southern portions of Map
ILI., in the region of Cottonwood and Little Cottonwood caiions, is exposed an
approximately conformable series of 30,000 feet of Paleozoic strata, overlying
the granite and schists which there together form a portion of the early
Archean surface. The origin and nature of the granites at this point are
obscure. There seem to be two distinct types —a granitoid gneiss, having a
decided stratification, and an apparently eruptive body, which possesses in an
interesting degree the conoidal structure so prominently developed in the
granites of the Sierra Nevada, About fifteen miles south of Salt Lake City
the Palzozoic beds are thrown into a broad semicircular curve, having a con-
vexity to the east and a varying dip always away from the centre of this curva-
ture. The ends of the strata of this great flexure advance westward until they
approach the region of the great fault, their eroded edges forming the foot-hills
of the range. The centre and nucleus of this immense curvature is a body of
Archean rock, composed partly of schists, but principally of a great central
mass of granite and granitoid gneiss, having its best exposures in Little Cot-
tonwood Canon and the peaks to the south, and again in the Clayton’s Peak
mass, where it rises like an island through the strata of the Lower Coal Meas-
ure limestone and the Weber quartzite... . . Although in Clayton’s Peak,
and again near the lower end of Little Cottonwood Cafion, the rock possesses
all the physical habit of a truly eruptive granite, and although in the Clayton’s
Peak region the granite has undoubtedly been a centre of local metamorphism

506 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

and of metalization, yet, from the position of the overlying strata, a prepon-
derance of evidence points to the belief that, whether eruptive or not, it is still
of Archean origin; hence its relations with the later stratified series are only
those of rigid underlying masses, and the local metamorphism observed in the
limestones near the granites is strictly. mechanical, and not to be mistaken for
the caustic phenomena of a chemically energetic intrusion. It should be men-
tioned, however, that it possesses, both in its interior composition and in a
peculiar conoidal structure, close affinities with the unmistakably eruptive
granites of the Sierra Nevada ; and it is quite possible that subsequent study
will determine the presence here of two distinct granites, the one having a
regular bedding and belonging to the stratified Archzean series, the other of
conoidal structure and eruptive origin. The main body extends about twelve
miles northeasterly, from the trachyte slopes of the Traverse Hills to the
head of the Little Cottonwood Caiion. Its greatest north-and-south expansion
is through Lone Peak, a line about eight miles long. South of the mouth of
Cottonwood Cafion a narrow isolated patch of granite appears involved in the
Archean schists... .. Passing up Cottonwood Canon, no sharp line of division
between the structureless granite and the bedded gneissoid form is observable ;
but there appear gradually more and more planes having an easterly dip, until
finally they approach the regularity of gneiss bed-planes, and the minerals are
seen to possess a vague general parallel arrangement. ... . The mineralogical
differences through all these bodies of granite are indeed slight; changes of
texture and arrangement produce a decidedly varying petrological effect, but in
general they are granites, containing — besides the normal orthoclase, quartz;
and biotite — plagioclase, hornblende, titanite, and apatite in high proportion ;
all but the apatite being visible to the naked eye. ... . There are present in
this neighborhood, then, two distinct families of rocks: first the Archean,
consisting of schists and granite ; second, the vast, conformable post-Archean
group of sediments. Wherever observed, the region of contact between the
two families displays no marked metamorphism on the part of the sedimen-
tary series, and within the Archean series no such transitions as would lead to
the belief that the granite is only a more highly metamorphic form of the erys-
talline sedimentary series ; on the contrary, the contact is so clearly defined,
and the rocks are mineralogically so dissimilar, that it is very evident that the
granite is either an intrusive mass or else an original boss over which the
Archean sedimentary materials were deposited. While the granite itself bears
a very close resemblance to the Californian eruptive granites, its relation to the
flexed Paleozoic strata would indicate that they were bent around a solid body,
not that a plastic granite intruded into the bent Paleozoics. The absence of
granite dikes penetrating the immense sedimentary series would strengthen the
belief that the granite antedated it. It is also noticeable that the dip and
strike of the Archean schists west of the granite body are entirely discordant
with the overlying Cambrian series, the former striking northeast and dipping
northwest, the latter striking northwest and dipping southeast, this unconform-
ability being preserved up tothe contact. Supposing the whole Archean body

el

THE FORTIETH PARALLEL SURVEY. 507

to have been thrust upward and eastward when the flexure of the Paleozoic
series took place, the present dip of the Archzan schists and quartzites would
indicate that before the great Wahsatch uplift they were ina nearly vertical
position, flanked to the east by the granite mass,”

We may now investigate a little more in detail the question of the
nature and origin of the granite, as well as the theories put forth by
Messrs. King and Emmons, to account for the stratigraphical position
of the rocks of the Wahsatch Range. In examining further we find
that Mr. King divides the eruptive granites of his survey into four
types (I., p. 107), and remarks : —

“This classification, based upon field observations, is interestingly carried
out by Zirkel, whose microscopic examinations in every way confirm the field
arrangement.” (1., p. 109.)

Of these types the Wahsatch granite is taken as the youngest ; but
he says :—

“There is absolutely no evidence whatever in favor of the belief of granitic
extrusions later than the Archeanage..... As an instance of how dangerous
any attempt to correlate age by petrologica] features alone really is, may be
cited the Jurassic granite of California and the granite of the Cottonwood
region on the Wahsatch, which is unmistakably Archean. They are posi-
tively identical down to the minutest microscopical peculiarity.” (I., p. 111.)

We now turn to the work of Professor Zirkel, whose manuscript was
revised by Mr. King and his assistants previous to its publication. And
since all his information in regard to the field relations of the rocks was
obtained from them, we may assume that his statements give a fair idea
of Mr. King’s views at the time of its publication. He remarks : —

“The decidedly eruptive granites may be divided into two classes: one em-
braces those older rocks that are of ante-Jurassic age ; the other, those which
have obtruded themselves through the Jurassic strata. For the enormous
mass of eruptive granite of the Sierra Nevada, Professor Whitney has demon-
strated a Jurassic origin; and, although not definitely proven, a similar age is
assumed for a considerable class of granites along the Fortieth Parallel, whose
petrographic constitution and habitus are identical with those of the Sierra
Nevada. The full details of the reasons of this assignment will be found in
the chapter upon granites in Vol. I. of this series. When, therefore, in this
memoir, Jurassic granite is spoken of, the intention is to designate that family
of which the Sierra Nevada occurrence is the type in age and constitution.
. . . . Clarence King has long since shown that the eruptive Jurassic granites,
and only these, are characterized by the presence of macroscopical titanite.”
(VL, pp. 39, 40.)

It has been seen that Mr. King divided the eruptive granites into

508 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

four groups, a classification which, as he states, Professor Zirkel’s “ mi-
croscopic examinations every way confirm”; but, in point of fact, the
latter divides them into two classes, the older eruptive granites contain-
ing no titanite, and the younger eruptive or Jurassic granites which
are characterized by the presence of that mineral. (VI., pp. 58, 59.)
The Wahsatch granite is regarded as the most characteristic type of
the younger or Jurassic granites bearing titanite. (VI., pp. 50-52.)
We have been unable to find in the writings of Messrs. King, Emmons,
and Hague any statement why their ideas of the age of these granites
underwent so radicala change after 1876,— any reference to new evi-
dence discovered, or to the views previously held, — or how, in the light
of what Professor Zirkel says in the chapter upon granite, he can be
quoted as then sustaining Mr. King’s views as published in 1878.

If Mr. King’s ideas regarding the origin of the supposed Archzean are
correct, thus far he has not been able to show that the rocks with which
the Archean is in contact are older than the Quebec group. In fact,
he and his assistants have failed to bring forward any proof of value in
support of their position. Rocks found in contact with others show
by their relations, as a general rule, whether they (1.) were deposited
against them as a sea-shore cliff; (2.) have been pressed against and
through them asa solid mass; (3.) were chemically deposited in con-
tact ; (4.) came as intrusions, overflows, or in any other way. Each oc-
currence has its own individual characters. These characters, in the
study of cases like the preceding, should be known from the examina-
tion of rocks whose origin and relations are known. We fail to find
any evidence in their publications that Mr. King and his assistants
looked for that proof which, if their views are correct, should exist in
overwhelming abundance.

Where sedimentary rocks of Potsdam age have been deposited in
contact with the Azoic rocks of Lake Superior, they show by the en-
closed fragments that they were derived from the latter; they show, on
examination of the contacts, that the Potsdam was deposited against a
water-worn cliff; no sign of mechanical, eruptive, or any other force,
except the impact of water, is to be observed. Had there been other
forces acting to any amount along the contacts their effects would have
been visible, and their history could be made out to a greater or less
extent. So in the case of the Wahsatch Mountains, if the Paleozoic
rocks were deposited against such cliffs as Mr. King imagines to have
existed, the evidence to prove this should have been sought for. Abun-
dant débris from the cliffs ought to have been found in the Paleozoic

THE FORTIETH PARALLEL SURVEY. 509

sediments. There cannot be a stratified deposit laid down upon a pre-
existing surface, conforming to its irregularities in such a manner as to
present itself in the form of continuous layers. Yet Mr. Emmons
describes such a phenomenon: hence the only conclusion following his
views is that the solid granite slid up along the bottom of the quartzite,
bending it so as to cause it to conform with the irregularities of the gran-
ite, and this elevation of the solid granite must have .metamorphosed
the limestone, and corrugated and uptilted all the adjacent formations ;
yet with all this the gentlemen studying the locality fail to show any
evidence that the granite was solid at the time. Is it possible that an
enormous mass of rough jagged granite could have been pushed like a
huge rasp in contact with quartzites, limestones, etc., and have left no
trace of its movement upon them? So, too, if it were intrusive, it
should in like manner show by its contacts that such was the case.
Instead of raising so extraordinary a fabric of theory on so slender a
basis of facts, it would have been better to study the region a little
more thoroughly. To us it appears highly probable that the granite
was of eruptive origin, and of later than Archean age. It is certain
that the section of the Wahsatch Range given in the Atlas of the
Fortieth Parallel Survey does not conform to the theories of Messrs.
King and Emmons ; and, moreover, that it represents impossible strati-
graphical conditions.

Views very similar to those here expressed by the writers of this
paper have already been published by Professor Geikie, Director of the
Geological Survey of Great Britain, in an article having as its title, ‘On
the Archean Rocks of the Wahsatch Range” (Am. Jour. Sci., 1880,
(3) XIX., pp. 363-367). From this paper the following extract is made,
and it will be a sufficient indication of the light in which Mr. Geikie
regards the geological speculations of Messrs. King and Emmons touch-
ing the structure and age of the range in question.

“ According to the Reports of the Exploration of the 40th Parallel, the Wah-
satch Mountains consist of a central core of Archzan rocks, composed partly of
granites and partly of various quartzite, schists, and other crystalline masses.
These rocks are represented as having formed an island in the Paleozoic sea ;
and Mr. King asserts that the island must have presented to the west an
almost precipitous face of 30,000 feet, or upwards of 53} miles —an altitude
exceeding that of any mountain chain. Round this lofty Archzan island the
whole of the Paleozoic and Mesozoic sediments are said to have been deposited
to a depth of from 30,000 to 40,000 feet, in one continuous uninterrupted
series. Subsequent terrestrial movements, acting along the line of the original
island, have upraised the surrounding sedimentary masses, and the ancient

510 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

crystalline rocks have once more been revealed by denudation. Now the fact
of the existence of a cliff more than 5} miles high would require to be estab-
lished by very carefully collected and convincing evidence. It was with very
considerable curiosity, therefore, that I paid a visit to the Cottonwood district,
where the evidence was said to be most complete. I must frankly own that I
failed to observe any grounds on which the assertion appeared to me to be
warranted. One would naturally expect that if a mass of strata 30,000 feet
thick had been laid down against a steep slope of land, its component beds
ought to be full of fragments of that land. ach marginal belt, representing
an old shore-line, should be more or less conglomeritic ; at least, there ought to
be occasional zones of conglomerate, just as at the Peet day, we have local
gravel beaches on our shores. But I could find no trace of pebbles. It would
of course be presumptuous in me to assert that they do not exist ; but they are
not mentioned by Mr. King, nor by Messrs. Hague and Emmons, and yet, as
their evidence would he so important, we can hardly suppose that these writers
observed them and made no reference to the fact. But not only have no peb-
bles of the Cottonwood granite been recorded as occurring in the overlying
Paleozoic rocks, it is admitted that these rocks become metamorphosed as they
approach the granite. The natural inference to be drawn from these facts,
one might suppose, would be that the granite is later in date than the rocks
overlying it. Mr. King admits that the granite has been undoubtedly the
centre of local metamorphism, but this change he regards as ‘ strictly mechani-
cal and not to be mistaken for the caustic phenomena of chemically energetic
intrusion.’ How he would discriminate between a mechanical and chemical
cause producing precisely the same ultimate effect he does not explain. ... .

“But if I am correct in regarding the Wahsatch granite as of post-Carbon-
iferous date, then we are relieved from the uncomfortable incubus of these
primeval mountains. We are not required to believe in the existence of a cliff
54 miles high, which maintained its position and steepness during the greater
part of all geological time. And we are spared the necessity of a colossal frac-
ture of 30,000 feet on the west side of the Wahsatch Mountains.”

We see no reason for proceeding further in the examination of the
work of the Fortieth Parallel Survey. Enough has been said to give a
sufficient idea of its character and value, as bearing on the question
before us. In brief, the whole matter may be thus summed up : —

All the crystalline and the eruptive rocks, between the Wahsatch and
the borders of California, with the exception of the modern volcanic
ones, have been called by the geologists of this survey “ Archean.” In
not a single instance, so far as we are able to make out, has there been
positive proof given that the rocks thus assigned were really of that
age. In many cases the stratigraphical conditions are of a kind that
such proof could not possibly have been obtained. In order to main-
tain the view of the Archean age of the rocks in question in certain

HAYDEN’S SURVEY. 511

regions, the most extraordinary, and as it seems to us impossible,
dynamic conditions have been invented, and sections drawn which are
not consistent with the theories advanced, nor with the observations of
Professor Geikie, nor with those of the senior author of the present
paper. An attempt has been made to divide the granite into eruptive
and metamorphic ; and it is claimed that the division thus made in the
field was supported by the independent microscopical examination of
Professor Zirkel. In point of fact, however, it appears that the latter
only observed certain differences between two sets of rocks submitted to
him by the geologists of the Fortieth Parallel as having been deter-
mined, in the field, to be eruptive and metamorphic. These differences,
however, are considered by Dr. Wadsworth to be non-essential, and not
such as would, in the case of other specimens from other regions, justify
the lithologist in assigning rocks so differentiated to different origins.
Indeed, Professor Zirkel, as already stated,* admits this. Furthermore,
it appears that at the close of the field-work the crystalline and granitic
rocks of the ranges of the Great Basin west of the Wahsatch were con-
sidered by Mr. King as being of post-Jurassic age, in accordance with
the observations and results of Professor Whitney and his assistants on
the Geological Survey of California ; but that some years later, at the
time of the publication of the volume of Systematic Geology, these rocks
were all classed as Archean, without any reference to the fact that so
radical a change of views on a point of so much importance had taken
place, and with no sufficient evidence for its support. It needs hardly
be added, that any reference to a division of the Archzan (Azoic) into
sub-groups in the Fortieth Parallel reports can only be looked upon as
wholly without importance or value, otherwise than as indicating certain
mineralogical resemblances to rocks described as occurring in Canada
and elsewhere.

HAYDEN’S SURVEY.

In 1868 Dr. F. V. Hayden remarked that the “ metamorphic rocks ”
in the valley of the Chugwater (Wyoming) were probably of Laurentian
age, but it is not stated upon what evidence this opinion was founded.
(Report of Commissioner of the General Land Office, 1868, p. 232;

* See ante, p. 500.

a THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

U.S. Geological Survey of the Territories, 1867, 1868, and 1869, [1873,}
prrd:)

In the Report of the U. S. Geological Survey of Colorado and New
Mexico, 1869, (pp. 22, 73, 87,) and in the publication last mentioned
above (pp. 122, 173, 187), Dr. Hayden presents a clear statement of
his views regarding the supposed Laurentian rocks in the region ex-
amined by him. He gives, however, no evidence in support of these
views. It is simply a profession of faith, in the following words :—

“T have assumed the position that all the rocks of the West are, or were,
stratified, and that where no lines of stratification can be seen, as In some of
the massive granites, they have been obliterated by heat during their meta-
morphism. .. . . This iron occurs in the gneissoid rocks, or what is called
the Laurentian group, to which group, I believe, all the gneissie and perhaps
the entire mass of metamorphic rocks of the Rocky Mountain system belong.
I have assumed the position, in all my investigations, that there are but two
classes of changed rocks in the West, viz., igneous and metamorphic, and that
the oldest granites which form the nuclei of the loftiest mountain ranges were
once aqueous rocks, deposited in the same manner as the limestones or sand-
stones of our most modern formations. ... . The gold and silver lodes of this
Territory [Colorado], so far as they are observed, are entirely composed of the
gneissic and granite rocks, possibly rocks of the age of the Laurentian series of
Canada,”

On the same page from which the last remark is copied, Dr. Hayden
distinctly shows that he regards the foliation of gneissoid rocks as sy-
nonymous with bedding and stratification. Had all our geologists been
as frank regarding the theoretical views upon which their work is based,
it would be far easier to estimate the value of their observations.

In the Annual Report for 1870 the same view of the age of the rocks
in the valley of the Chugwater was repeated. Of the rocks on the
north side of the Uinta Range, near the head-waters of Bear River, Dr.
Hayden remarks : —

‘Tn all this series of strata, from the red beds to the oldest quartzites, I was
able to detect no unconformability. ... . Tam inclined to believe that the
upper beds are Silurian, that they pass gradually down without any break in
the sequence of time to rocks of Huronian age. The purplish quartzites are
almost precisely like those which occur at the Sioux Falls in Dakota, and at
the Pipestone quarry, in color and texture, which Professor Hall regards as
Huronian age.” (J. ¢., pp. 14, 50.)

The above quartzite appears to be the Weber quartzite (Carbonif-

erous) of the Fortieth Parallel Survey, and the Uinta sandstone (Devo-
nian) of Major Powell (Systematic Geology, p. 152; Geology of the

9

HAYDEN’S SURVEY. 513

Uinta Mountains, p. 70). Hence, as it appears, considerable difference
of opinion exists as to its age. Mr. S. F. Emmons apparently inclined
to regard it as Cambrian (Descriptive Geology, p. 199), while Professor
Marsh and Dr. C. A. White thought it probable that it was Silurian
(Am. Jour. Sci., 1871, (3) I., p. 193 ; Annual Report, 1876, p. 23). In
his Annual Report for 1871, (p. 39,) Dr. Hayden remarked : —

“The precious metals, as gold and silver, are found, so far as my observa-
tions have extended, entirely in the metamorphic rocks which hold a position
below all groups of strata that we have been in the habit of regarding as Pale-
ozoic. Whether they belong to the series denominated in Canada the Huronian
or Laurentian, we have no data to decide positively ; but inasmuch as they are
all clearly stratified rocks, they are plainly of sedimentary origin.”

In the Report for 1873, Dr. Hayden stated that

“the underlying metamorphic rocks [near South Park] are made up in part of
quartzitic sandstones, full of rounded pebbles of quartz, which would indicate
that they might belong to the Laurentian series.” (J. c., p. 41.)

In the Report for 1874, (pp. 190, 191, 239,) Dr. F. M. Endlich held
that the granite and other so-called metamorphic rocks were formed
from the metamorphosis of the Silurian and Devonian rocks in the dis-
trict studied by him.* These rocks appear to be the same as those
called Archzean by the other members of the Survey. (See also Report
for 1875, p. 113.)

In the Annual Report for 1875, Dr. A. C. Peale makes the following
statement :—

“ Sufficient data have not yet been obtained to determine the exact age of the
metamorphic series, although, as Marvine remarks of those farther east, [An-
nual Report, 1873, p. 139,] ‘ the prevalence of siliceous and granitic types recalls
the descriptions of Laurentian areas.’ In one place the schists are very dis-
tinctly stratified, consisting of dark micaceous schists, with seams of quartz
and feldspar. These may be of Huronian age, although we cannot trace their
relations to those of the other Archzan rocks, as they are exposed in an isolated
area at the bottom of cafions distant from the other outcrops.” (J. c., p. 64.)

In the Annual Report for 1877, (p. 156,) Dr. F. M. Endlich, in a
tabular view of the formations of the Sweetwater district, divides the
Azoic rocks into three systems. The oldest of these, called Prozoic,
consists of massive granite. The third, called Huronian, likewise con-
sists of granites, less massive than those of the first system, and con-

* The area between the meridians of 107° and 108°, and the parallels of 37° 15!
and 38° 15/, at the head of the Rio Grande and the Rio Animas.
VOL. v1I.— No. 11. 33

514 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

taining darker-colored micas. The intermediate system, to which the
name of Laurentian is given, is said to be made up of schists ‘“ composed
of quartz, feldspar, hornblende, and mica.” This classification seems to
be purely a mineralogical one, and not justified at all —in so far, at
least, as the giving of the names Huronian.and Laurentian is concerned
— by anything observed in the field. Indeed, Dr. Endlich himself states
that,

“although special examinations were made to determine whether the different
mineralogical constitution of the {metamorphic or Archeean] rocks remained
constant within certain zones, no applicable data upon this point could be
obtained. .... Within the main chain the stratoid segregation of the granites
is not very completely carried out... .. It would require the most careful
examinations, conducted on a liberal scale, as to time, to elicit evidence bear-
ing upon the former condition of this metamorphic area.” (J. c., p. 66.)

Much the same may be said, with truth, of the division of the Azoic
series into sub-systems by Dr. Hayden’s assistants, Professor St. John
and Dr. A. C. Peale. The former assigns the crystalline rocks of the
Teton district to the Laurentian and Huronian systems, placing the
granites and gneisses in one division, and the quartzites and slates in
the other, there being no stratigraphical basis whatever indicated for
this arrangement. The reference to the Huronian is, indeed, suggested
only with doubt by Professor St. John. (/. ¢, p. 480.) The same is
true of the division of the Archzean into ‘ Huronian?” and “ granite,”
given by Dr. Peale. (/. ¢., p. 612.)

It appears on examining the published volumes of the Hayden Sur-
vey, as well as from personal investigation of a part of Central Colo-
rado by one of the authors of the present paper, that through the whole
extent of the Cordilleras, and especially in the Rocky Mountain region
proper, the axes of the mountain chains are usually made up of erystal-.
line rocks, entirely destitute of fossils. These rocks are chiefly granites
and gneissoid granites ; slates occur in extremely subordinate quantity.
In the northern portion of the chain, where the entire Palzeozoic series,
including the Potsdam sandstone, is developed, there could be no hesita-
tion in assigning these when not eruptive to the Azoic or Archean. But
it is not certain that there is any Archean proper in the whole range of
the Cordilleras; and in most cases it is beyond doubt true that the
axes of the chains have been erupted and the stratified masses uplifted
at a period much later than the Azoic. Thus, for instance, we have in
California post-Jurassic and post-Miocene eruptive granitic centres or
axes, in the Sierra Nevada and Coast Ranges respectively.

WHEELER’S SURVEY.— JONES'S SURVEY. 515

Furthermore, in the Central and Southern Rocky Mountains we find
that a large portion of the lower divisions of the series of stratified rocks
is wanting. Thus in the Front Range of Colorado the crystalline masses
are directly overlain by rocks generally admitted to be of Triassic age.
In such cases, and in these regions, we have the same difficulties which
occur in the Appalachian ranges; it is—or at least has been up to
the present time — very difficult for most geologists to clearly distin-
guish, either in the field or in the cabinet, between metamorphic erup-
tive and metamorphic sedimentary rocks.

WHEELER’S SURVEY.

In the Reports of the Geographical and Geological Survey west of the
one hundredth Meridian, under Capt. Geo. M. Wheeler, we have seen
no evidence advanced to prove the occurrence in the supposed Azoic
areas examined by that Survey of distinct geological formations.

Of the rocks called “ Archean” in the region explored in 1878 and
1879, embracing portions of North Central New Mexico and South Cen-
tral Colorado, Professor Stevenson says : —

‘No absolute evidence exists to settle the age of these rocks. Lithologically
they bear close resemblance to the Laurentian series of the east, and at more
northern exposures within the Rocky Mountain region they have been re-
ferred by all observers to that age. The coarse gneissoid and often conglom-
erate granite immediately underlying the Carboniferous at many localities may
possibly be of somewhat later origin.” (Wheeler’s Report, Vol. III., Supple-
ment, p. 72.)

JONES'S SURVEY.

In a Report upon the Reconnoissance of Northwestern Wyoming by
Capt. Wm. A. Jones, in 1873, Prof. Theo. B. Comstock remarked on
the Azoic rocks examined by him :—

“There are some slight reasons for placing a portion of the oldest of these

rocks in a group nearly equivalent to the Laurentian system of the East, but it
must be confessed that none of them are based upon much better foundation

516 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

than a certain similarity to that formation in lithological characteristics. Their
position upon the stratigraphic chart is, therefore, entirely provisional.” (lJ. ¢.,
p- 106.)

POWELL’S SURVEY.

In the publications of the U. S. Geographical and Geological Survey,
under Major J. W. Powell, we are able to find but little relating to the
subdivision of the supposed Azoic rocks examined by that Survey.

In a “Report on the Geology and Resources of the Black Hills of
Dakota,” by Henry Newton and Walter P. Jenney, published in con-
nection with Major Powell’s Survey, and revised by Mr. G. K. Gilbert,
the granite is shown to be eruptive along the foliation of the schist, and
not a sedimentary rock. An attempt is made to divide the rocks of the
region into two ages, Laurentian and Huronian ; but they do not appear
lithologically to have the characters of either formation. The division
into two groups is stated to be'a lithological one only, as the two series
conform in strike. A diversity of dip is said to have been observed at
one point, but that observation is not insisted upon.

Furthermore, however, we find it stated that “the lithological evi-
dence fails to give even its feeble support to the theory that the two
Archean groups of the Black Hills are the representatives of the two
Archeean groups of Canada.” (J. ¢., pp. 45-80.)

CALIFORNIA.

The geological investigations of the California Survey, carried on from
1860 to 1874, show that the gold-bearing slates of the Sierra Nevada
are of Jurassic and Triassic age. No fossils older than the Carbonifer-
ous have ever been found in that range. The Mesozoic series has been
uplifted by eruptive granite, which forms the axis of the chain, On
these uplifted rocks strata of the Cretaceous epoch rest unconformably
and almost without disturbance. Hence it is a well-established fact —
the geological age of the different formations having been made out by
the discovery of fossils at numerous localities, and reference to their

CALIFORNIA. 517

proper position by skilful paleontologists —that the upheaval of the
Sierra Nevada took place between the Jurassic and Cretaceous epochs.

In like manner, the age of the strata making up the Coast Ranges of
California has been shown, by discovery of fossils in numerous localities,
to be Cretaceous and Tertiary. These strata have been uplifted at
various times during the Tertiary epoch, in some regions even as late as
the post-Pliocene.*

Of course, such being the case, there can be no rocks in California
which can be properly said to belong to the Azoic system (Archean).

In view of these facts, for the purpose of throwing further light on
the methods and theories of Dr. Hunt, as set forth to some extent in
the preceding pages, it will be well to quote some of the remarks pub-
lished by him at various times in regard to the rocks of California.

In 1866 Dr. Hunt stated :—

“The notion that gold belongs only to rocks of Lower Silurian age, was
many years since disproved by its discovery in the Upper Silurian slates of
eastern Canada, and more recently, it has been shown that the great gold
mines of California are in strata far more recent, and chiefly of the Jurassic and
Triassic periods.” (Geol. of Canada, 1866, p. 196.)

In 1868 Dr. Hunt again states : —

“The auriferous rocks of California belong to the Mesozoic period, being of
Jurassic age.” (Gold Region of Nova Scotia, 1868, p. 11.)

In 1877, however, Dr. Hunt visited California for the first time, and,
having spent several days in the Sierra Nevada, published the following
statement (Am. Assoc. Ady. Sci., 1877, XXVI., p. 266; Proc. Bost. Soe.
Nat. Hist., 1878, XIX., pp. 276, 277; Macfarlane’s “ Geologist’s Trav-
elling Hand-Book,” p. 13 ; Azoic Rocks, p. 244) :—

“Eruptive granites are found in California, where they abound among the
foot-hills of the Sierras, in Placer and Nevada counties. The crystalline
schists observed by the speaker in these counties, and in Amador county, are
Huronian, and have all the characters of the Huronian series as seen in the
eastern regions of North America, and of the pietri verdi of the Alps. To this
horizon are also to be referred the similar crystalline rocks of the Coast range
of California, as seen near San Francisco and San Jose. The auriferous veins
which, in the Rocky Mountains, intersect the Laurentian gneisses, are found

* See Geology of California, Vol. I. passim ; and, for full information in regard
to the geological age of the rocks of the gold-bearing belt, ‘‘ The Auriferous Gravels
of the Sierra Nevada of California,” Contributions to American Geology, Vol. I.
pp. 34-39.

518 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

in the Sierras alike in the Huronian schists and in the eruptive granites, which
probably penetrate the Huronian series.”

Dr. Hunt stated that the crystalline schists of the Sierra Nevada
examined by him have ‘all the characters of the Huronian series
as seen on the great lakes.” (Proc. Bost. Soc. Nat. Hist., 1878, XIX.,
p- 276.)

In 1880 Dr. Hunt further stated that the gravel at the Blue Tent
placer mine, in Nevada County, California, is “made up in great part
of the débris of the crystalline Huronian schists of the region, including
much greenstone or diorite rock.” (Trans. Am. Inst. Min. Eng., 1880,
VIIL., p. 452.)

The present writers, having had occasion to make a prolonged and
most careful examination of the rocks of the Sierra Nevada, and of the
Coast Ranges of California, as well as of those of the south shore of
Lake Superior, take occasion to remark, that no such resemblances as
those pointed out by Dr. Hunt have any real existence. The rocks of
the California Coast Ranges, even where most metamorphosed, differ,
both microscopically and macroscopically, from those of the Sierra
Nevada, and specimens from the two regions in question would never
be mistaken for each other by any one having even a moderately well

trained eye. In the same way, the slaty crystalline rocks of the Sierra .

Nevada differ nearly as much from those of the Azoic regions of Lakes
Huron and Superior as do the basaltic lava-flows of the latter region
from those of Mount A2tna. Macroscopically, the rocks of the two
series could never be confounded with each other, and microscopically
the differences are equally striking. Hence it appears that, while the
palzontological evidence is entirely averse to the dicta of Dr. Hunt in
reference to the Huronian age of the Coast Range and Sierra Nevada
rocks, even the lithological characters are quite as little in harmony
with his views. Recalling what Professor Dana has remarked in refer-
ence to the Lower Silurian age of Dr. Hunt’s Vermont Huronian, it
may here be added, that the latter has, by what he has published in
regard to California, made out the Huronian to be also Mesozoic and
Tertiary, so that this formation may be said now to represent, according
to Dr. Hunt’s views, the whole geological column from top to bottom.

OO

PART. JL

Résumé, and General Discussion.

THE great length of the preceding division of this contribution to our
knowledge of the older geological formations of the United States and
the adjacent northern region makes it necessary for us to offer, in this
second and concluding portion of our work, but a brief synopsis of the
conclusions at which we have arrived in the study of these older rocks.
We have already set forth, in considerable detail, the theories which
American geologists have held at various times in regard to those older
crystalline rocks to which the names Archzean and Azoic have been com-
monly applied, and in doing this we have had special reference to the
necessity or possibility of dividing that series of rocks into two or more
distinct groups. We have given the evidence on which these various
theories were based with considerable detail, because the facts which
developed themselves, as we pursued our inquiry, were so extraordinary
that we felt it to be doubtful whether our statements would be accepted
as truthful unless we presented the reader with the means of verifying
them at once, on the spot, without the necessity of examining a long
series of volumes, some of which are only to be obtained with the
greatest difficulty. More work has, however, been done by us, both in
the field and in the laboratory, in the investigation of the subject here
discussed, than the cursory reader of the present article would per-
haps be inclined to suppose; and we trust that the opportunity may
yet be furnished us for carrying this work still farther in the same
direction, and for presenting the whole body of the results which we
have reached, as well as those which may hereafter be attained, in a
fuller form than it is possible for us to do at the present time.

We think that it is impossible for any unprejudiced worker in this
department of science to peruse with care the preceding pages, and not
feel obliged to admit that the geology of a large portion of this country,
and especially that of Canada and New England, is in an almost hope-
less state of confusion. We think that it must have been made clear
to the candid mind, that the geologist would find himself completely
baffled who should endeayor to obtain any definite knowledge of the real

520 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

nature and order of succession of the rocks which cover so large a por-
tion of the region in question from the study of that which has been
published with regard to them. We believe that we are justified in
going still farther, and saying that our chances of our having at some
future time a clear understanding of the geological structure of North-
eastern North America would be decidedly improved if all that has been
written about it were at once struck out of existence. That this con-
dition of things is largely due to the erroneous observations and theories
of the Canada Survey, which to a large extent have been adopted and
blindly followed on this side of the Dominion boundary, is a statement
the truth of which we think no one who has carefully studied the evi-
dence presented in the preceding pages will not feel obliged to admit.
While not desiring to conceal the fact that some of the problems pre-
sented in the course of the study of the older rocks are extremely
difficult, we find it clearly proved that want of knowledge, want of
experience, and a desire to produce sensational theories, have brought
about this condition of confusion. Some of the salient points which
have presented themselves in the course of this investigation into the
history of geological opinion in this country will therefore now be passed
in review, and the subject then left, for the present, to the reader’s
candid consideration. .

The establishment of the Silurian System by Murchison opened the’
way to the discussion of the question whether the lowest limit of life in
the geological series had been, or was likely to be reached. The fact
that in England the lower fossiliferous rocks are greatly disturbed and
metamorphosed, and that consequently their order of succession is very
difficult to make out, rendered it much less easy to arrive at any defi-
nite conclusions in regard to this question than it was in countries like
Bohemia and the United States, where the Silurian strata, over large
areas, rest in undisturbed succession upon each other. Before, however,
the investigations of Barrande had led him to infer that there was a
distinct limit to traces of life in the descending order of formations,
Murchison had arrived at this result, led thereto by his geological work in
Scandinavia, which country he had visited in connection with his recon-
naissance of European Russia, and where a large amount of detailed
investigation of the lower rocks had already been made by the able
Swedish geologists, all of which was placed at his disposition.

The first use of the term “ Azoic,” with an approach to a definite
meaning, was made by Murchison, with reference to the rocks of Scan-
dinavia. His statement was as follows : —

RESUME, AND GENERAL DISCUSSION. 521

“On this point we have recently convinced ourselves, by clear and indisput-
able sections, that the lowest beds charged with anything like animals or vege-
tables are the exact equivalents of the Lower Silurian strata of the British
Isles, and that these have been distinctly formed out of, and rest upon, slaty
and other rocks which had undergone crystallization before their particles were
ground up and cemented together to compose the earliest beds in which or-
ganic life is traceable. To the crystalline masses which preceded that paleozoic
succession to which our researches were mostly directed, we apply the term
‘Azoic,’ not meaning thereby dogmatically to affirm, that nothing organic
could have been in existence during those earliest deposits of sedimentary mat-
ter, but simply as expressing the fact, that in as far as human researches have
reached, no vestiges of living things have been found in them, so also from
their nature they seem to have been formed under such accompanying condi-
tions of intense heat and fusion, that it is hopeless to expect to find in them
traces of organization. .... In the term Azoic rocks, we include all the
crystalline masses belonging to the ancient group of gneiss, together with
ancient granitic and plutonic rocks by which they have been invaded.” *

It will be noticed that Murchison considered that his “ Azoic”” rocks
—in Scandinavia, at least— seemed to have originated under such
conditions that the existence of organic life at the time of their forma-
tion was impossible; yet, as he hastens to add, he was not willing
“dogmatically to affirm” that these rocks might not contain fossils.
It is not easy to understand exactly what Murchison meant by these
two evidently contradictory statements; but this want of tenacity of
opinion in regard to the truly azoic character of the infra-Silurian rocks
was still further exemplified in the various editions of his ‘ Siluria,” in
the course of which we see the author passing gradually from an up-
holding of a series of necessarily non-fossiliferous “ bottom rocks,” up to
a positive recognition of the Laurentian and Huronian systems of the
Canada Survey, and the admission that the rocks designated as “ Azoic”
and said to be necessarily azoic, did furnish proofs of the existence of
life on the globe at the time of their formation.t

* Proc. Geol. Soc. London, Vol. IV. (1845), p. 602. The Geology of Russia in
Europe, and the Ural Mountains, Vol. I. (1845), p. 10.

+ In the first edition of ‘‘Siluria” (1854), the rocks called in ‘‘ Russia and the
Ural Mountains” Azoic are designated by the term ‘‘ Bottom Rocks,” and they are
said to “lie below all those formations in which there are the slightest vestiges of
Silurian life.” These rocks are also said to have been ‘‘ formed, as I [Murchison]
believe, at a period when the heat of the earth was antagonistic to the existence of
living beings.” In the third edition of the same work — the second is not at hand
for reference — the Azoic rocks are designated as ‘‘ primeval” and “fundamental,”
and it is said that ‘‘ they may have been formed ata period when the heat of the
earth was antagonistic to the existence of living beings.” In the fourth edition of

522 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Barrande, in his earliest communication embodying the results of his
life-work among the Paleozoic rocks of Bohemia (1846), did not use the
term “primordial,” which he later adopted, and in which he included
the lowest zone of life ; but he speaks of his division “‘C” as “ forming
the base of the Protozoic rocks, according to the latest classification
of the Rev. Professor Sedgwick.” His (Barrande’s) groups “A” and
“ B” constitute the ‘‘ Lower Division,” comprising all the Azoic forma-
tions, subdivided into two groups, their upper one (‘‘B”) being identi-
fied by him’as the equivalent of Sedgwick’s Cambrian, — the confusion
in geological nomenclature caused by the introduction of this term hay-
ing begun as far back as these earliest days of discussion in regard to
the Azoic.and Paleozoic rocks.

It appears, however, that Sedgwick, as late as 1854, had not arrived
at any definite conclusions in regard to the existence of an Azoic series,
for he says of his Cambrian, “that it seems to contain no organic re-
mains.” But he hastens to add, that the answer to the question when
organic life began ‘“‘is involved in inextricable obscurity.” *

In 1851+ Messrs. Foster and Whitney made known the existence of
a series of rocks on the south shore of Lake Superior, in regard to which
they wrote as follows : —

“ Below all the fossiliferous groups of this [the Lake Superior] region, there

is a class of rocks, consisting of various crystalline schists, beds of quartz, and

saccharoidal marble, more or less metamorphosed, which we denominate the
Azoic System. This term was first applied by Murchison and De Verneuil to
designate those crystalline masses which preceded the Paleozoic strata. In it
they include not only gneiss, but the granitic and plutonic rocks by which it
has been invaded. We adopt the term, but limit its signification to those
rocks which were detrital in their origin, and which were supposed to have
been formed before the dawn of organized existence.” {

It is now known that a large part of the vast region adjacent to Lake
Superior on the north and east, and included within the limits of Can-
ada and British North America in general, is occupied by rocks which
by their infra-Silurian position and lithological character belong in the

** Siluria”’ (1867), the Azoic is called “ Laurentian,” and is regarded as being ‘‘ the
base of all Paleozoic deposits.”

* British Paleozoic Rocks and Fossils, 1854, Introduction, p. xxxii.

+ A synopsis of their results had in the previcus year (1850) been presented to
the Department of the Interior, and in this the nature and geological position of the
“ Azoic System” had been clearly set forth. Senate Documents, 2d Sess. 31st
Cong., 1850-51, II., Doc. 2, pp. 147-152.

t Foster and Whitney’s Report on the Geology of the Lake Superior Land Dis-
trict, Vol. Il. The Iron Region, together with the General Geology, 1851, p. 3.

a

RESUME, AND GENERAL DISCUSSION. 523

Azoic of Foster and Whitney. These rocks had been met with by the
geologists of the Canada Geological Survey, and were designated by
them in the Report of Progress for 1845-46 as the “ Metamorphic
Series,” * their geological position not having been clearly ascertained,
nor the question considered whether the lowest Lower Silurian really
formed the base of the fossiliferous strata, so that rocks underlying
them unconformably could properly be called Azoic.

After the publication of Foster and Whitney’s Report—in 1854,
namely — Mr. Logan, the chief of the Canada Survey, recognizing the
fact that the term “metamorphic” had no special significance as desig-
nating the geological age of any group, since rocks in any part of the
series may be metamorphic, adopted for the Azoic of Foster and Whit-
ney the designation of ‘“‘ Laurentian,” a name previously proposed by
an eminent authority for a group at the other end of the geological
series, and already in current use—an act of great injustice, as we
have already pointed out.t Neither was any reference made in the
report of the Canada Survey, in which the name “ metamorphic ” was
exchanged for that of ‘‘ Laurentian,” to the fact that the geological
position of these rocks had previously been definitely established, and
another name given to them by the American geologists working on
the southern side of Lake Superior.

Furthermore, owing to the inability of Mr. Logan to distinguish be-
tween the Azoic quartzites of Lake Huron, and the very dissimilar
sandstones, conglomerates, and interbedded volcanic rocks of Keweenaw
Point, utter confusion was introduced into the geology of the region of
the Upper Great Lakes —in the minds, at least, of those accepting the
dicta of the Canada Survey as authority — a condition of things which
was not fully rectified until many years later. f

For some time after the introduction of the term “ Azoic” into the
geological nomenclature by Foster and Whitney, that term was current
among geologists in this country. Dana, in the first edition of his
“Manual of Geology,” the Preface of which bears the date of Novem-
ber 1, 1862, and in the revised edition, issued in 1871, in which it is
stated that the work “has received such alterations as seemed to be

* See ante, pp. 331 et seq.

t+ See ante, pp. 7, 338. Also, Am. Jour. Sci., (2), XXIII. 305-314 ; Proc. Bost.
Soc. Nat. Hist., XX1. 121, 122.

t See a statement in reference to the results attained by the Geological Survey of
Canada, published by A. R. C. Selwyn, present chief of that Survey, in ‘‘ Science,”
number of February 9, 1883.

524 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

required by the results of recent geological research,” adopts the term
* Azoic,” but not in the exact sense in which it was used by Foster
and Whitney. He includes under that designation all the rocks which
were in existence at the time animal life began, stating his views in the
following words : “ The Azoic rocks constitute the only universal forma-
tion. They cover the whole globe, and were the floor of the oceans and
the rocks of all emerged land when animal life was first created... . .
Whatever events occurred upon the globe from the era of the elevated
temperature necessary to fusion, down to the time when the climate
and waters had become fitted for animal life, are events in the Azozc
age.”

But farther on (/.c., p. 145), Dana advocates the idea that there
may have been life on the globe during the Azoic period, for he says,
“The term ‘ Azoic,’ as here used, implies absence of life, but not neces-
sarily of the lowest grades.” He then gives the following “reasons in
favor of the existence of life of some kind [in the Azoic].” 1st. The
formation of limestone strata. 2d. The occurrence of graphite in the
limestone and other strata. 3d. The occurrence of anthracite in small
pieces in the iron-bearing rocks of Arendal, Norway, which rocks are
probably Azoic in age. He then proceeds to give reasons why, suppos-
ing the existence of life of some kind, it is more likely to have been
vegetable than animal. But he distinctly admits (/. ¢, p. 147) that
“whenever the earliest plant, however minute, was created, then the
grand idea of life first had expression, and a new line of progress in the
earth’s history was announced.” And, still farther on (/.¢., p. 178), he
admits that “the life of the Potsdam period is the beginning of the system
of life deciphered in American geological history.”

In the second edition of his Manual, the Preface of which bears date
March 1, 1874, Dana takes a position in reference to the Azoic sys-
tem materially different from that previously occupied by him. He
now introduces the term ‘‘ Archean,” and defines ‘ Archean Time” as
“the beginning, including a very long era without life, and finally that
in which appeared the earliest and simplest forms of plants and ani-
mals.” Farther on, however, (J. c., p. 146,) he says, that ‘ Archzan
time includes strictly, as its commencement, an Azote age, or the era in
which the physical conditions were incompatible with the existence of
life. But this era, so far as now known, is without recognizable records ;
for no rocks have yet been shown to be earlier in date than those which
are now supposed to have been formed since the first life began to
exist.”

RESUME, AND GENERAL DISCUSSION. 525

In view of the contradictions and confusion of ideas thus shown te
prevail among the most eminent geologists in reference to the nomen-
clature of the oldest crystalline rocks, no one can do otherwise than
admit that it is quite time that some more definite understanding
should be had of this whole subject, and, as a contribution toward this
desirable end the following remarks are submitted.

There are two essentially different ways of looking at the rocks which
make up that portion of the earth which is accessible to investigation.
One of these has reference to the manner in which these rocks have
been formed ; the other, to the chronological order in which they have
come to occupy the position which they now hold. Roughly speaking,
it is this idea which forms the basis of a division of the science of ge-
ology into two quite distinct departments, Dynamical and Historical
Geology. For the study of the former a knowledge of lithology and
petrology is indispensable, while the latter is chiefly an application ‘of
the results of paleontological investigation to questions of synchronism
and order of succession in the rocky strata.

In considering other worlds than our own, no more important ques-
tion could be asked in regard to them than this: Are they inhabited,
or does organic life exist upon them? The only reason why this ques-
tion is not oftener asked or more discussed is, that it is one to which a
definite answer cannot now be given, while there seems to be extremely
little chance that there will ever be any change in this respect. It is
not beyond the bounds of possibility that some meteoric fragment may
be dropped upon this earth bearing evidences of the existence of life on
another world ; but, up to the present time, the aspect of such bodies
as have come to us from outside our own atmosphere has not been
of a character to encourage any expectation that such an event may
occur in the future. Still, it will hardly be denied by any one that
proof of the existence of life on any of the planets, or any other of the
heavenly bodies, would be accounted one of the most interesting revela-
tions ever made to the human race. Similarly, to fix in the order of
events through which this earth has passed the epoch when life began
to exist on the globe, must be admitted to be a problem of high impor-
tance ; and, as intimately connected with this, and of similar interest,
would necessarily be the inquiry whether any rocks could be pointed
out in regard to which it could be affirmed with truth that they were
deposited, or brought into their present position, before the appearance
of life on the earth.

Here, however, a point suggests itself as of importance in connection

526 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

with the present inquiry ; namely, that while there may be rocks which
are azoic because no life existed when they were formed, there are
others which from the very nature of their mode of formation and
occurrence could not show any indication of the presence of life, even
although it may have existed on the same planet, and in the immediate
vicinity of the rocks in question at the time they were deposited or
placed in their present position. Thus, no one would expect to find
signs of life in lava, or in the granitic masses originally constituting a
part of the earth’s crust, and which were formed at a time when the
temperature and other conditions could not have been favorable to the
development of life, but which may have been raised since their for-
mation into perhaps close proximity to strata replete with the remains
of organized beings.

On looking over the subject of the existence of “ Azoic” rocks —
that is, of such formations as are destitute of evidences of the presence
of life at the time of their formation or deposition —we find that
there are several categories in which such rocks may be classed.

lst. We may have strata, once fossiliferous, in which the evidences
of life have disappeared in consequence of the metamorphic changes
which those rocks have undergone. Experience shows that such cases
are not uncommon ; but that, usually, the geological age of such meta-
morphic strata may be recognized, either by means of their position
with reference to strata of known age, or by tracing the metamorphosed
formation to such a distance from the source of the alteration in ques-
tion that we find the formation manifesting itself in its original condi-
tion. To such metamorphic strata we should never have occasion to
apply the term “ Azoic,” since we should clearly recognize the fact that
their azoic character was something which did not originally belong to
them. |

2d. Rocks may be azoic, even if laid down when life was existing on
the globe, provided the local conditions were not favorable to its devel-
opment at the particular locality under consideration. Thus, much the
larger portion of the Potsdam Sandstone of Lake Superior is entirely
destitute of traces of life; yet, as there are occasionally — even if very
rarely — localities where this rock is fossiliferous, we should not think
of separating the fossiliferous portions from the non-fossiliferous, or
of calling them by any special name, in consequence of the absence of
traces of life in them.

3d. Again, rocks must necessarily be azoic, when formed or originat-
ing under such conditions as were incompatible with the existence of life.

i

RESUME, AND GENERAL DISCUSSION. 527

The original crust of the earth must have been azoic, if we adopt the
views held by the large majority of geologists, that our globe has cooled
from a former condition of igneous fluidity. The volcanic and eruptive
rocks must necessarily be azoic, because they have come from the heated
interior of the globe, reaching the surface, for the most part, in a melted
condition. We do not, however, designate the eruptive and volcanic
rocks as “ Azoic” ; the fact that they are necessarily in this condition is
assumed as something self-evident.

4th. We may have rocks formed under such conditions as were not
inimical to life, but yet azoic, because life had not begun to exist on the
globe at the time of their deposition. These, according to our view,
would be the rocks properly designated by the term “ Azoic,” and the
body of rocks having this character might properly be called the
* Azoic System.” And we think that, in view of what has here been
set forth, no one will deny that it is important that, if there are such
rocks, they should have a special designation, and that the term
“ Azoic” would be a proper one to apply to them.

This, however, is exactly what was done by Foster and Whitney,
in 1850, when they gave the name of the ‘ Azoic System” to a body of
strata, originally —in part, at least — of sedimentary origin, which did
not show by their character that life could not have existed at the time
of their deposition, but which proved, on examination, to be entirely
destitute of fossils, and which, moreover, were found everywhere to
underlie unconformably other stratified formations which were recog-
nized as containing the lowest known forms of organic life.

Over thirty years have elapsed since these rocks were designated as
forming the Azoic System, and the point at present at issue is, whether
anything has been discovered in geology which renders this designation
improper, unnecessary, or undesirable, or which justifies the adoption of
either one of the terms “ Laurentian” or “Archean,” or both, the ques-
tion of the propriety of dividing the Azoic System into two or more
groups being one to be examined farther on.

The introduction of the name “ Laurentian” by the geologists of the
Canada Survey has been already commented on, and it has been shown
that this term, as first used by Mr. Logan, was the exact equivalent of
the Azoic of Foster and Whitney. That being the case, the question
of the propriety of this action on the part of the author of the new
designation may be left to the good sense of the reader, who will judge
for himself whether replacing a designation already in use by another
one, previously employed by another geologist with a totally different

528 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

meaning, is a justifiable proceeding. And it will be noticed that any
objection to the word Azoic, based on the ground that the formation in
question had been found to contain organic remains, and therefore not
to be properly called Azoic, was not in order at the time Mr. Logan
introduced the term Laurentian, as it was not then pretended that these
lower rocks were fossiliferous.

We proceed now to a discussion of the desirability of adopting the
term Archean, introduced by Dana; and, with this end in view, it will
be necessary to look a little more minutely into the way in which it is
used by this geologist. It will not have escaped the notice of the reader,
however, that much in this discussion turns upon the question whether
the so-called Azoic, Archzean, or Laurentian rocks are, or are not, destitute
of traces of organic life. Hence, in order to clear the way for what is
to follow, it will be well to take up this question at once.

To those familiar with the geological literature of the past twenty
years, it will be evident that the only essential point before us is this:
Is the Lozoén a “thing of life”? If it is not, then all the accessory
evidence that the Archzean rocks are fossiliferous falls away of itself,
as we shall endeavor to show, as being utterly intangible and unsatis-
factory.

Without going into anything like a detailed account of the various
publications issued by the Canada Survey, or under its inspiration,
having it for their object to prove that there is a fossiliferous group of
rocks below the lowest Lower Silurian (the Potsdam or Primordial),
and of the discussion in regard to this point which has been going on
during the past twenty years, we may content ourselves with giving a
brief résumé of the facts connected with this rather remarkable chapter
in the history of our geological progress.

Another name having been given by the Canada Survey to the rocks
previously known as Azoic, it became desirable that the formation thus
newly designated should be shown to be a fossiliferous one. For this
purpose that problematical body now so well known under the name of
the Lozoin was brought forward, and at the present time there exists
quite a voluminous eozodnal literature.*

The first announcement in connection with the subject of the Eozoén
was made by Mr. Logan, in his Report for the year 1858. In 1859 he
exhibited specimens at the meeting of the American Association for the
Advancement of Science, but went no farther at that time than to

* For a chronological catalogue of this literature, see ‘‘ An Old Chapter of the
Geological Record,” ete., by W. King and T. H. Rowney, London, 1881, pp. ix-liv.

RESUME, AND GENERAL DISCUSSION. 529

say that he was disposed to consider these specimens ‘‘as fossils.” In
1864, Dr. Dawson, in his Address before the Natural History Society
of Montreal, announced that he had “arrived at the conclusion that
théy [the fossils in question] are of animal nature, and belong to the
very humblest type of animal existence known, that of the Ahzzopods.”
He adds, that ‘the discovery of this remarkable fossil, to be known as
the Hozoin Canadense, will be one of the brightest gems in the scientific
crown of the Geological Survey of Canada.” *

This preliminary announcement was followed by several elaborate
papers, by Messrs. Logan, Dawson, and Hunt, published in the Quar-
terly Journal of the Geological Society, as well as others by Dr. W. B.
Carpenter, published in the Proceedings of the Royal Society, in which
it was claimed that the fossil in question was a Foraminifer ; or, to use
Dr. Carpenter’s exact words, “ that the Hozoédn finds its proper place in
the Foraminiferal series, I conceive to be conclusively proved by its
accordance with the great types of that series in all the essential char-
acters of organization, — namely, the structure of the shell forming the
proper wall of the chambers, in which it agrees precisely with Mum-
mulina and its allies; the presence of an ‘intermediate skeleton, and
an elaborate ‘canal-system,’ the disposition of which reminds us most
of Calcarina ; a mode of communication of the chambers when they
are most completely separated, which has its exact parallel in Cyclo-
elypeus ; and an ordinary want of completeness of separation between
the chambers, corresponding with that which is characteristic of Car-
penteria.” F

From this time forward the Eozodn began to be an important matter.
The authority of Dr. Carpenter, at first, bore down all opposition ; and,
with few exceptions, geologists and palzontologists gave this gigantic
Foraminifer a place as the “earliest known representative on our planet
of those wondrous powers of animal life which culminate and unite
themselves with the spirit-world in man himself.” $

Gradually, however, there came a reaction from the shock of this
stupendous discovery, which first manifested itself in a denial, on the
part of Professor Harkness (1865), of the organic nature of the Eozoin.
This was followed in the succeeding year by an elaborate paper by
Messrs. King and Rowney, in which they maintained that the Hozodn
Canadense must be relegated to the inorganic kingdom. From this

* Canadian Naturalist, 1864, p. 220; Am. Jour. Sci., (2), XXXVII. 232,
t Quarterly Journal of the Geological Society of London, XXI. 64,
+ Dawson, ‘‘ The Dawn of Life,” p. 1.

VOL. VII, —No. 11. 34

530 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

time forward, no year has failed to add something to the literature of
this subject. But it must be admitted that the opponents of the
organic character of the Eozodn have been on the whole decidedly in
the minority. This problematical body has, almost without exception,
gone into the various text-books of geology, in all countries where that
branch of science is cultivated, with at most, in some instances, a vague
intimation that there were some persons who were not disposed to
accept the Eozodn as a relic of organized existence.

It was not an easy matter for those convinced that this body was sim-
ply a mineral to furnish satisfactory proof of the correctness of their
opinion ; for when it was said by them that they could discern nothing
necessarily organic in the specimens of Eozobn which they had exam-
ined, it could always be replied, from the other side, that these op-
ponents of the Eozodn had not had the opportunity of studying the
series of specimens in the collections of the Canada Survey, and that
these were so complete and convincing in character that every one to
whom this privilege should be granted would be compelled to acknowl-
edge that opposition to the views of Messrs. Dawson and Carpenter had
no basis of fact. ;

In 1875, however, Professor Mibius of the University of Kiel, having
discovered a Rhizopod, to which he gave the name of Carpenteria Rha-
phidodendron, and which appeared to him, at first, to have an astonishing”
resemblance in its structure to that of the Eozoén, determined to make
a thorough investigation of the Canadian supposed fossil, and, for this
purpose, solicited material from all quarters. As he appeared to be, if
not convinced, at least quite desirous of being convinced, of the organic
nature of the Eozoén, he was supplied with all the best material in the
hands of Dawson and Carpenter. Indeed, the latter, as Professor Mobius
states, gave him one thin section, which he had never before allowed
to go out of his hands, on account of its furnishing such important evi-
dence of the organic nature of the Eozoon.*

The work in which the results obtained by Professor Mobius are
given to the world is remarkable, especially, for the number and clear-
ness of the illustrations which accompany the text, and they are of

* “Professor Carpenter hatte die grosse Giite, mir vortreffliche Praparate zu
schicken ; ja, er vertraute mir einen Diinnschliff zum Studium an, den er seines
hohen beweisenden Werthes wegen noch niemals aus den Hiinden gegeben hatte.”
Mobius, in ‘* Der Bau des Eozoon Canadense,” ete., p. 177. In spite of this, we find
Dawson claiming that the results obtained by Mobius should not be accepted as

valid, because the latter ‘‘had access merely to a limited number of specimens.”
Am. Jour. Sci., (3), XVII. 197.

—

RESUME, AND GENERAL DISCUSSION. 531

special value as allowing every one to see for himself just what the speci-
mens amounted to, which were held by Carpenter and Dawson to fur-
nish full evidence of the organic character of the Eozoin. The exact
position of Professor Mobius when he began the investigation, and the
result to which he attained, can be easily made out from the following
sentence, in which the whole thing is summed up in a few words: “I
began this investigation with the hope that I should succeed in prov-
ing, beyond possibility of doubt, that the Eozodn was organic. The
facts, however, led me to the opposite conclusion.” *

The value and importance of the investigations of Mobius have been
acknowledged by Zittel, who thus expresses his opinion of the nature of
the Eozoén: “ In spite of the repeated answers of Dawson and Carpen-
ter, this long struggle to maintain the organic nature of the Eozoén
may well be admitted to have been brought to an end, and with a result
unfavorable to that view, by the exhaustive memoir of Mébius.” To
this emphatic testimony on the part of Zittel may be added the equally -
positive statement, to the same effect, of the eminent palzontologist,
F. Roemer, who thus states the case: “Finally, Mébius undertook an
exhaustive microscopical investigation of this body [the Eozoon], in car-
rying on which he was able to make use of the best material in the pos-
session both of Dawson and Carpenter, and he reached the positive and
unquestionable result [sicheres unzweifelhaftes Ergebniss] that the sup-
posed Hozoén is simply an inorganic formation [Bildung] consisting of
serpentine and chrysotile in limestone. Consequently, by far the larger
majority of geologists and paleontologists will consider this question as
definitively settled, and will be all the more ready to do so, since the
occurrence of a fossil of this character in the oldest crystalline limestone
was, on general principles, in the highest degree improbable.” +

It is believed that in this country no geologist or palxontologist of
eminence has distinctly put himself on record as being opposed to con-
sidering the Eozoéu as a fossil. We have, however, a statement of
Professor Leidy —a high authority on the lower forms of animal life,
and who at the same time is familiar with minerals —to the effect
that he, in 1877, “was not fully convinced of its [the Eozoén’s] animal
nature.” ¢

Apart from the evidence so skilfully presented by Mébius, as well as
by Carter, Rowney, and King, we have that of our own obtaining, and

* 7. ¢., p. 189.
t F. Roemer, Lethza Paleozoica, 1880, p. 285.
t Proceedings of the Academy of Natural Sciences of Philadelphia, 1877, p. 20.

532 ‘ THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

which we consider entirely decisive of the question, and in favor of the
mineral nature of the Eozoén. The fact of the occurrence of the so-
called ‘‘eozodnal structure” in some of the limestone deposits of East-
ern Massachusetts has been repeatedly admitted both by the advocates
and the opponents of the organic character of this peculiar body.* By
most geologists these calcareous masses have been considered to be in-
terbedded with and an original portion of the formation, and supposed
to be beyond doubt of sedimentary origin.

In 1871, however, after a careful study of the eozoénal limestones of
Chelmsford, Bolton, and Boxborough, Mr. L. 8. Burbank claimed that
these were not true stratified deposits laid down with the gneiss, but of
subsequent formation to that rock, and of vein-like character; and that,
in consequence of this, the Eozoédn must be of mineral, and not of ani-
mal origin. These views were sustained by Messrs. W. H. Niles and
J. B. Perry, —the latter extending his observations so as to include the
_ locality at Newbury. Mr. Burbank gave figures illustrating the mode
of occurrence of the limestone, and these seemed to furnish strong evi-
dence in support of his views.T

Most of these localities have been studied by us, with especial refer-
ence to the origin and mode of occurrence of the calcareous material.
At Stoneham, the limestone was found to occur in an indurated argil-
lite, which is cut through by dikes of diabase (diorite), ete. The cal-
careous mass, lying approximately in the direction of the strike of the
enclosing rock, frequently cuts across its lamination planes, so as to
include masses of the argillite; and portions sometimes extend for a
considerable distance across the stratification, so as to have the charac-
ter of fissure veins. The limestone is entirely crystalline, and shows
upon its borders that intense chemical action has there taken place, as
it is greatly altered and filled with epidote and such other silicates
as are ordinarily found resulting from conditions of the kind here sug-
gested. While one of the dikes was .seen to intersect the limestone,
others were found to have been cut off by it. These latter dikes
abutted directly against the limestone, and along the line of junction of
the two rocks were the same evidences of intense chemical action which
were seen at the edge of the calcareous mass in other places.

From this it follows that this limestone is a segregated or vein-like
deposit, of earlier date than some of the dikes, but posterior to the

* See ante, pp. 411, 419.
+ Proc. Bost. Soe. Nat. Hist. 1871, XIV., 189-204; Proc. Amer. Assoc, Adv.
Sci., 1871, XX., 262-266, 270-276.

RESUME, AND GENERAL DISCUSSION. 533

time of the formation of the larger portion of them. It would seem
from these observations that the calcareous mass was the result of the
action of thermal waters during the time of the dying out of the vol-
canic forces which have been shown to have formerly been active in
Eastern Massachusetts.*

The limestone localities at Chelmsford, so fully described by Mr.
Burbank, were also carefully examined by us. They are included in
gneiss, and are extremely irregular, sometimes coinciding in direction
with the lamination of the enclosing rock, and at other times cutting
across it. So irregularly are the gneiss and limestone locked together
that their relations to each other could, in our judgment, only be ex-
plained by admitting that the calcareous material is a segregated
deposit. This ‘‘eozodnal” limestone is entirely crystalline, and filled
with scapolite, actinolite, and other silicates ; while the Eozoén is most
abundant and best preserved in the most decidedly crystalline portions
of the calcareous deposit. No dike was seen to be cut by the limestone ;
but one, of melaphyr, about two inches wide, was seen traversing it.

We have also studied the deposits of limestone in Newbury, known
as the ‘‘ Devil’s Den” and “ Devil’s Basin.” The relations of the cal-
careous mass to the enclosing rock at these localities are very similar
to those already indicated for the others, and do not allow of explana-
tion in any other way than by admitting that the limestone is a segre-
gated deposit. The evidences of intense chemical action are here also
plainly revealed by the presence, in the calcareous mass, of silicates,
such as wollastonite and garnet. Moreover, the rock in which the lime-
stone is enclosed — the country rock — is, as we think, an eruptive one,
belonging with the older basalts, but of course much changed from its
original character.

This view of the segregated nature of these deposits was, moreover,
entirely freed from anything which it might have of a theoretical nature
by our finding at Devil’s Basin—the locality in which the Eozoén
occurs —that the country rock was cut by dikes of eruptive rock,
which squarely abutted against the limestone on the side without
intersecting it. Also, the ends of the dikes next to the limestone
showed the same intense chemical action and resulting secondary sili-
cates that the country rock in like position does. All this indicates, in
the most unmistakable manner, that the country rock was formed, and
that dikes traversed it, before the limestone was there. In short, the cal-
careous mass has been introduced since the formation of the enclosing

* Harv. Univ. Bull., No. 22, pp. 359, 360.

534 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

rock, and consequently could not by any possibility be an original con-
temporaneously bedded structure ; neither could it be fossiliferous, any
more than an ordinary veinstone could so be.

For the purpose of accounting, to a certain extent, for the extraordi-
nary delusion which has prevailed among paleontologists with reference
to the organic character of the Eozoén, a few words may here be added.
In the first place, attention may be called to the fact, that the discovery
of traces of organic life in such rocks as lavas and granites, and even
in slags and meteorites, has become one of the common occurrences of
the present day. <A long list of names might be cited of scientific
observers who have enriched geological literature with “ gems” of this
kind. The reasons of this are in part to be found in the desire to do
something sensational, and in part to the entire ignorance which pre-
vails among many zodlogists and paleontologists as to the great variety
of forms occurring in the mineral kingdom, which it only requires an
imaginative temperament to endow with the attributes of organic struc-
ture. Symmetrical grouping of minute crystals, dendritic markings,
radiated aggregations, fibrous structure, and many other commonly
occurring forms in which minerals are found, have, each in turn, served
as a basis for a new genus, family, or order in the animal or the vege-
table kingdom. :

A complete list of all the books and papers which have appeared
within the past twenty or thirty years, —that is, during the latest epoch
of geological enlightenment, — having for their object the display to the
scientific world of dazzling “gems” of the Eozoén family, would form
quite a lengthy document. Space can only be found for alluding to a
few of these which are of special interest as bearing — more or less di-
rectly —on the Eozoén question, either as showing how the sponsors of
this supposed organism have allowed themselves to be deceived in other
and parallel cases, or how far, in general, those can go who have once
taken up the idea that the peculiar mineral forms with which they are
unfamiliar, and which have a superficial resemblance to the work of
living organisms, are really such.

As Dr. W. B. Carpenter is the person who, more than any one else, is
responsible for the generally prevailing belief in the organic nature of
the Eozoén, it will be well to call attention, in the first place, to a com-
munication of this eminent authority, published in “ Nature,” and
headed “ New Laurentian Fossil.” In this he remarks, in reference to a
specimen furnished him by a gentleman who had been “ for some years on
the outlook for fossils in the Laurentian rocks of Scotland,” as follows : —

RESUME, AND GENERAL DISCUSSION. 535

“The fabric seems to have consisted of superposed layers of calcareous shell
substance, whose continuity is frequently interrupted... .. The state of
preservation of the fossil thus corresponds exactly with that of the Silurian
Stromatopora, to which, indeed, it bears a strong general resemblance. ... .
The shelly layers are as distinct in character from the calcite contents of the
chambers, as are those of the Nummulites of the pyramid-limestone with
which they agree in their remarkable hardness, corresponding with that of
porcellanous shell. Altogether I have no hesitation in concurring with Prof.
H. A. Nicholson, Prof. Geikie, and Mr. Etheridge in affirming it to be so
unmistakably organic, that, if it be claimed by mineralogists as a ‘ rock struc-
ture,’ a large number of universally-accepted fossils will have to go along with
it. As it is essentially calcareous in its composition, there is no room for the
hypothesis of its production by the process of ‘mineral segregation,’ which is
maintained by certain mineralogists . . . . to have been adequate to the pro-
duction of the alternating layers of serpentine and calcareous shell-substance
in the Canadian Hozodn. And though mineralogical analysis might not im-
probably detect small particles of various minerals in its substance, their pres-
ence no more establishes its claim to be regarded as a mere rock structure,
than does the presence of siliceous films . . . . in a piece of corai-limestone.”’ *

Some weeks later Dr. Carpenter acknowledged that the fossil thus
elaborately described by him was not calcareous, but that it consisted
“of alternating layers of feldspar and quartz—the former simulating
an organic structure like that of Stromatopora, and the latter occupying
what had been supposed to be the cavities of that structure — together
constituting what is known to petrologists as ‘ graphic granite.’ ” F

In this case, however, Dr. Carpenter might claim that, having made
a mistake, he was ready and willing to withdraw his statements after he
had been shown to be in error; and that, having done this, the value of
his testimony in regard to the Eozodn was not thereby impaired. As
an offset to this, we will proceed to show that in the case of one of the
fundamentally important features of his supposed Foraminifer he was
also as much mistaken as he was in regard to the graphic granite, and
that he has admitted himself to be so; but that he did not make this
admission until after having persisted in his error for many years, so
that we are left entirely in the dark as to how long we must wait before
being able to find out what his final opinion will be ina matter of this kind.
The point is this: Dr. Carpenter, after having, at various times during
an interval of fifteen years, called attention to the so-called ‘“ proper
wall” or “nummuline layer” of the Eozoén, the existence of which he
said that he had been able ‘ most satisfactorily to determine,” and which
he considered to be ‘‘a point of the highest importance in the determiia-

* Nature, 1876, XIV. 9. t Ibid., 68.

536 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

tion of the affinities of Eozoin,” * has recently admitted that he was entirely
mistaken in all this, and has conceded the fact claimed by the opponents
of the organic character of this supposed fossil, that this nummuline
layer was simply the mineral chrysotile in one of its ordinary forms of
occurrence, namely, in bands or layers of finely fibrous material.

In describing certain rocks of New Hampshire called by him “ green-
stones,” and assigned to the Huronian formation by Prof. C. H. Hitch-
cock, Dr. Hawes made the following statements : —

“Tn the microscopic study of these massive chloritic rocks, or metadiabase,
I have found certain forms which appear to be of organic origin. . . . . It has
the structure of a tabulated coral, resembling much a Chetetes ; but on account
of its minuteness, in connection with other characters, there is little question
but that it is a fragment of a rhizopod mass or foraminifer ;$ and a close
resemblance to a Stromatopora will be noticed... .. These forms seem to be
abundant in the rock. . ... The specimen figured is the most perfect that I
have seen ; but smaller fragments are abundant, and as they are apparently
alike in dimensions, they sustain the supposition of the organic origin of all.
. . «+ These forms, distributed through the massive rock, have a structure,
... » which cannot be attributed ‘to crystallization. They seem to make it
evident that rhizopods must have been living over the sea bottom during the
accumulation of these sediments, and became buried in the mud which is now
the material of the rock. These forms are composed of silicates... .. Yet
upon placing a drop of acid upon one of them it effervesced for a short time;
showing that carbonate of lime existed in it— perhaps part of that of the
original foraminifer.

“The presence of these remains of rhizopods in the metadiabase is addi-
tional evidence of the sedimentary origin of these rocks ; and they also confirm
the view that the metamorphism was feeble in its degree, since it allowed of
the preservation of these forms. . . . . Everything points to quiet waters dur-
ing the original deposition,§ and finally to gentle metamorphism.” |

* Quart. Jour. Geol. Soc., XXI. 62.

+ This retraction, on the part of Dr. Carpenter, of one of the most essential fea-
tures of the Eozodn has not, so far as we know, been published; but it was made in
public at a meeting of the Boston Natural History Society, and repeated in private
at the Museum in Cambridge, in presence of one of the authors of this paper.

t The reader will be tempted, at this point, to exclaim with Dr. Carpenter,
‘Truly, as I have had occasion before to say, ‘there is no limit to the possibilities
of Foraminifera!’” (Nature, XIV. 9.)

§ It may be said that these rocks have been examined by Dr. Wadsworth, and
their microscopic characters found to be identical with those of the altered diabases
of Eastern Massachusetts, which occur in unmistakable dikes, cutting argillite (Primor-
dial ?). The field evidence, Mr. Huntington states, indicates that Hawes’s rocks
were in dikes.

|| Am. Jour. Sci., 1876 (3), XII. 129-187.

RESUME, AND GENERAL DISCUSSION. 537

The supposed fossils were examined by Principal J. W. Dawson, who
pointed out their resemblance to parts of Hydroids, Bryozoans, Ento-
mostracans, and some Devonian plants, or lastly to some supposed
Laurentian fossils of Giimbel. He also says: ‘On the whole, though
these objects are unlike any purely mineral substance with which I am
acquainted, and are probably fragments of some organic body, I do not
think it possible at present to indicate with any certainty their probable
affinities.” * These fossils also appear to have received Dr. Hunt’s in-
dorsement.f

Later, Dr. Hawes, having in the mean time studied in Europe, frankly
acknowledged that his supposed fossils were simply the alteration pro-
ducts of titaniferous iron, stating: ‘“‘The other gentlemen who have
seen these specimens, and have published opinions in reference to them,
are very excusable, on the ground that they [Dawson and Hunt] saw
but single specimens, and are not professed experts in microscopic min-
eralogy. The author has paid some attention to the subject, under
competent instruction, since the paper referred to was published.” t

In view of what has been stated above, it would seem that Messrs.
Dawson and Carpenter ought not again to claim to have any right to
the expression of an opinion on points like those involved in the
question of the organic character of the Eozoén, since they have both
shown themselves entirely unacquainted with elementary mineralog
and lithology.

Of all the upholders of the organic nature of the Eozoén, there is no
one whose work is so curious and instructive — from the point of view
of one desirous of ascertaining how far the determination to find traces
of life in everything can carry an observer —as is that of Otto Hahn.
This author is an entire believer in the organic character of Eozoén ;
but is surprised that any one should be so blind as not to recognize that
it is a plant.§ Fifteen different plant forms are described by him as
made out from his Eozoén sections, and each is gifted with a distinct
name. One animal appears to have had the exclusive range of this
wonderful vegetation, the Z%tanus Bismarki/ The title of the work in

* Am. Jour. Sci., 1876 (3), XII. 395.

+ Proc. Am. Assoc. Ady. Sci., 1876, XXV. 208.

+ Geology of New Hampshire, III., Part IV. pp. 40, 41; Am, Jour. Sci., 1878 (3),
XVI. 396.

§ ‘‘ When I now look through my thin sections and find in them the plainest evi-
dences of reproductive cells (Brutzellen) belonging to the plant, . . . . Iam obliged
to believe that all those who worked at the Eozoin, myself included, were smitten
with blindness,” (Hahn, Die Urzelle, ete., p. 19.)

538 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

which all this is revealed is as follows: ‘The Primeval Cell, together
with the Proof that Granite, Gneiss, Serpentine, Talc, certain Sand-
stones, also Basalt, and finally Meteoric Stones and Meteoric Iron, con-
sist of Plants.” This is only the carrying a little farther of the same
style of observation as that to which we are indebted for the Eozoén,
and that some one should follow this line of research to the highest
pitch of absurdity seemed to be the one thing wanting to give the
Eozoén the coup de grace.

As already mentioned, it is held by Dana, as well as by many other
geologists, that the occurrence of limestone in the Azoic series is evi-
dence of the existence of life at the time of its formation. The same
view is also maintained with reference to the presence of graphite in
these rocks. In upholding these views it is the authority of Bischof
which is chiefly followed. This author, in his classic work on chemical
geology, declares in the most positive manner that those geologists who
believe that the earth has cooled from a condition of igneous fluidity can-
not do otherwise than admit that all the carbon on and in the earth is
of secondary origin, that is to say, was not present in the primeval earth
(in der Schépfungsperiode nicht vorhanden war). The statements which
he brings forward to sustain this view are, however, not correct.

The first of these alleged facts is, that carbon could not have existed
in contact with the oxides of iron and the other metals in a melted
magma, because it would necessarily have been oxidized to carbonic
acid and carbonic oxide.* In answer to this it may be stated, that, if
graphite cannot exist, it certainly can be formed, under these conditions,
since it is a well-known fact, daily witnessed by those engaged in blast-
furnace operations, that this material separates out in distinct crystal-
line plates and scales from the melted iron as it cools ; moreover, the
presence of graphite in furnace slags is a matter of not infrequent occur-
rence. The presence of graphite in the metallic iron meteorites may
also be mentioned in this connection, as strong evidence that carbon
can exist in connection with melted iron, or be in some way separated
from it. This graphite occurs in some cases in nodules completely
enveloped in the metallic mass. In the iron-bearing basalts of Green-
land, graphite is also found both in the metallic iron and in the basaltic
rock, in which this metal is enclosed.T

* Bischof, Jahrbuch der chemischen und physikalischen Geologie, 2d edition,
I. 662, 663.

+ See Térnebohm, in K. Svenska Vet. Akad. Handlingar, Band V. No. 10; also,

Daubrée, Géologie Experimentale, p. 555. Lawrence Smith, Mémoire sur le Fer
Natif du Groenland, in Ann. de Chim. et Phys., (5), XVI. 452-505.

RESUME, AND GENERAL DISCUSSION. 539

Furthermore, Bischof states as additional evidence of the truth of
his assertion that carbon cannot have existed in the primeval earth, that
this element is not found in the unstratified crystalline rocks which,
according to the views of the plutonists, were lifted up from beneath.
(“Da die ganze Gruppe von nicht geschichteten krystallinischen Ge-
steinen, welche nach Ansicht der Plutonisten von unten heraufgehoben
werden, in ihrer Masse keinen Kohlenstoff enthalten,” etc. )

This, again, is an entire mistake on the part of Bischof. The lar-
gest and most important deposit of graphite in the world — that of the
Alibert mine —is described by various geologists who have seen it as
occurring in granite, or as lying between granite and syenite. In fact,
the normal occurrence of graphite may be said to be in the older gneis-
sic and schistose rocks, in which it either forms lenticular masses of
greater or less size, or is disseminated through the rock in scales, or
thin layers.

One of the most celebrated known localities of graphite is in Bavaria,
in the so-called Passauer Wald, where it has been for a long series of
years extensively worked. Giimbel has made a thorough investigation
of this region. The rock in which the graphite is contained is gneiss,
called by this geologist ‘“‘Graphitgneiss,” because the mineral in ques-
tion is disseminated through the rock just as the mica is, forming
apparently an integral part of it ; not —as Giimbel thinks is evident —
replacing the mica, but being an original constituent of the gneiss. To
use his own words: ‘‘ We must therefore consider the graphite to be as
much a primary formation [primaire Bildung] as are the other minerals
of the gneiss, of which it makes a constituent part.”

Graphite occurs in the crystalline limestones associated with the
older crystalline or azoic rocks ; but not —so far as we know —aggre-
gated into masses of sufficient size to be anywhere an object of prof-
itable exploration. The normal mode of occurrence of graphite in
limestone seems to be in the form of thin scales disseminated through
the rock, and these scales are larger and more distinctly developed
where the limestone is most crystalline.

Indeed, so far are the statements of Bischof from the truth, that it
may be stated, as the result of geological observation up to the present
time, that true graphite is “almost exclusively confined to granite,
gneiss, quartz, mica-slate, crystallized limestone, and the older slates.” *

That graphite has been formed from vegetable matter, at least in a
manner similar to that in which coal has been, as is claimed by so

* Jukes and Geikie, ‘‘ The Student’s Manual of Geology,” 3d edition, 1872, p. 56.

540 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

many geologists, seems to us in the highest degree improbable, for
the reason that true graphite has never been found —so far as our
"knowledge goes — in connection with coal, whether the latter be in its
ordinary bituminous condition or in its nearest approach to pure carbon
as anthracite, as it ought to be if it was formed in the same way in
which coal has been, and was only the carrying forward of that process to
the last stage of carbonization. If graphite was the final result of the
working of the agencies by which vegetable matter has been turned
into anthracite, it seems impossible that, somewhere in the vast area
covered by the anthracitic formation in this and other countries, there
should not be at least some distinct traces of graphitic material found.

It is stated in the various text-books of mineralogy and geology, that
graphite has been formed by the passage of dikes of eruptive rock
through coal beds. This, however, does not seem to be confirmed by
the result of more recent and more careful observations than those made
in the days to which many of the statements in our text-books belong.
So far as our own observations go, the tendency of the eruptive rocks,
in their passage through coal, is to change this into a material very dif-
ferent in character from graphite. :

Much of what is called “ plumbago” is by no means graphite. _ It is,
rather, a mixture of particles of carbonaceous matter with rock; the
result being, in certain cases at least, a refractory material which can
be used for some of the purposes for which graphite is employed. We
repeat, therefore, that we have never seen, and know of no authentic
account of any one else having seen, pure graphite and coal so associ-
ated together as to make it necessary to believe that the former was
produced by the decomposition of vegetable matter, as we have abun-
dant reason to believe that coal in all its forms has been.

The graphite which is formed artificially at the present day is, so far
as we know, exclusively the result of operations carried on at a high
temperature.* The separating out of graphite in cast-iron and slags,

* The same may be said of the more or less successful attempts to make artificial
diamonds. The experiments of Mr. Hannay in this line, in which he claims to
have succeeded in forming this gem, although by no means affording any encourage-
ment for the belief that it can be manufactured with pecuniary profit, seem to have
resulted in the production of something which had the physical characters of the
diamond. High temperature and immense pressure were the most important factors ;
but it is stated by Mr. Hannay that the presence of nitrogen seemed to be a sine qua
non. This last-mentioned item may be noticed in connection with what is said
farther on in the text in reference to the part played by cyanogen in the formation of
artificial graphite.

RESUME, AND GENERAL DISCUSSION. 541

and the formation of the material in gas retorts, are striking instances
of this.

The most abundant source of artificial graphite, however, is in con-
nection with the manufacture of soda by the Le Blane process ; for
here the quantity produced is so large that it has been seriously pro-
posed to use it for the manufacture of lead pencils. This graphite,
according to R. Wagner, is formed at a certain stage of the process of
converting the caustic soda into the carbonate; at which time the
cyanogen present — which must have resulted from the preceding treat-
ment of the saline mass at a high temperature in the reverberatory
furnace — undergoes decomposition, the carbon separating out in the
form of graphite. The same origin is claimed by Wagner for the
graphite occurring in cast-iron. According to him, it is not the carbon,
dissolved in the iron itself, which separates out when the latter cools and
solidifies, but that which is derived from the decomposition of the cya-
nides present in large quantity in the iron as well as in the slag. These
cyanides undergo decomposition, the carbon appearing as graphite, and
the nitrogen going off in the form of ammonia, well known to be one
of the products of blast-furnace operations.*

Thus it appears that we know of no other way in which graphite can
be artificially formed than indirectly in connection with, or as one of
the results of, some process or Ee carried on at a very high
temperature.

The position assumed by Bischof with reference to the diamond is also
based on imperfect knowledge of the facts connected with the occur-
rence of this most remarkable substance. It was Bischof’s idea that
the diamond was formed in the superficial detrital material of recent
age, in which this gem had until within a few years been exclusively
found. He believed that it was simply a result of the decomposition of
organic matter, under conditions which prevail everywhere ; so that, if
his view were the correct one, the diamond, instead of being the most
precious of gems and being found in exceedingly te quantity, should
be literally “as common as dirt.”’

The facts in regard to the diamond, from the standpoint of our
present knowledge, are simply these: Wherever detritus of crystalline
rocks occurs unconsolidated, so that it can be cheaply “handled,” —
that is, moved and washed, — there gold either has been in former times
or is now being obtained, although not by any means always in remu-

* See Sitzungsberichte der phys.-med. Gesells. zu Wiirzburg, 1869, p. xxii. ; also,
Wagner's Jahresbericht, 1872, p 57.

542 THE AZOIG SYSTEM AND ITS SUBDIVISIONS.

nerative quantity. Most of these detrital deposits, where rich enough
to pay for working, have already been washed over, and have become
exhausted of their gold. Those which are still the object of exploita-
tion on a large scale usually produce diamonds as well as gold ; as, for
instance, Australia and California, not to speak of the less important
Appalachian gold-fields. It is true that the quantity of diamonds thns
produced is very small, so that there would not be the slightest proba-
bility that the auriferous gravels could ordinarily be worked with profit
for this gem ; although we have reason to believe that by the common
methods of gold-washing much the larger proportion of the diamonds
would be lost or passed over unseen. Still, we are obliged to admit
that the diamond must originally have had its birthplace in the same
crystalline rocks from which the gold has been derived, and out of
whose detritus both these precious substances are washed. There is no
more reason to suppose that the diamonds were formed in the gravel
posterior to its abrasion from the solid rock than that the gold was.

The occurrence of the diamond in Brazil, in the detrital formations,
in no respect differs from that indicated for California and Australia,
except that these are localities where this gem is unusually abundant,
and where the detrital material is more ferruginous than it ordinarily is.
The diamonds have been deposited in a modern gravel, made up of the
ruins of a much older crystalline formation ; and this gravel has been,
in places, reconsolidated into a rock by having become impregnated
with a ferruginous solution. Whether the diamonds came originally
out of the crystalline metamorphosed sedimentary rocks, or out of the
eruptive masses with which these are associated — the eruptive mate-
rial often predominating very largely over the sedimentary: this we
know not, as the diamonds are always found loose, in crystals, and sepa-
rate from any of their original matrix.

In fact, it is only within a few years that we knew anything definite
about the occurrence of the diamond in its original matrix. The
locality we refer to is, of course, South Africa, where this gem occurs,
within certain well-defined limits, in much larger quantity than was
ever before known. But here the matrix, or enclosing rock, is unques-
tionably eruptive. It not only has the mineralogical characters of an
eruptive rock, but the whole style of its occurrence is such as to stamp
it as unmistakably volcanic. Everything about the South African
diamond-bearing localities is remarkable and exceptional ; and thus far
the theory of the origin of the diamond has been but little advanced
by the observations made in that region. All that can safely be said

RESUME, AND GENERAL DISCUSSION. 543

is, that it seems as if the idea that a high temperature had been one of
the factors in the mysterious operation of making the diamond had
received a certain additional amount of corroborative evidence in conse-
quence of the association of that gem with volcanic materials in the
most productive diamantiferous district the world has ever known.

That the conditions under which this precious gem has been formed
are very exceptional, can be safely inferred from the extremely small
amount of the material which has been originated. Not that the dia-
mond is limited, or almost exclusively so, to one locality, like certain
minerals, — as, for instance, cryolite and red oxide of zinc. It occurs,
on the contrary, all over the world, but never —so far as yet observed
— in masses weighing more than a few hundred grains; while, if all the
specimens of this gem which go to help make up the crown-jewels of all
the empires and kingdoms of the world were put together, their united
weight would certainly not exceed a few pounds.*

The inference from that which has been stated above is, that we are
not justified in assuming that the occurrence of graphite in the azoic
rocks is a proof that this material has resulted from the action of or-
ganic agencies, or, in other words, that life existed on the globe at the
time these rocks were deposited. The fact that no recognizable traces
of such life have ever been found in connection with the graphite of the
Azoic series, is decidedly an important item in this connection ; and we
consider that geologists are not justified in assuming the presence of life
when they not only have no positive evidence of its existence, but when
the theoretical probabilities are strongly in opposition to this view.

The idea that the presence of carbonate of lime must necessarily be
taken as a proof of the former existence of life—as is so positively
asserted by Bischof, Dana, and many other geologists —seems to us
entirely at variance with the facts. It is impossible for any one famil-
iar with the mineralogical occurrence of carbonate of lime to deny that
the formation of this material is a process which is going on, in innu-
merable localities and on a grand scale, without the intervention of
organized existences.

Every metalliferous vein is likely to have, and in many instances
such veins do have, the metallic sulphides which they contain — sul-
phur being by far the most common mineralizer of the metals — more
or less completely converted into carbonates at their outcrops. Thus,
while chalcopyrite is the most common ore of copper, the carbonate of

* The total weight in the rough of thirteen of the largest and most celebrated dia-
monds in the world was only a little over a pound.

544 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

the oxide of this metal is very frequently found, and sometimes in
large quantity, in and near the outcrop of such veins. Water takes
carbonic acid from the air, and, percolating downwards, converts a great’
variety of mineral substances more or less completely into carbonates.
This is a process which may be said to be going on everywhere on a
grand scale.

Calcareous spar (calcite) is one of the most common of veinstones,
occurring in very large masses, both in regular veins and in those
masses which belong to the segregated form of metalliferous and min-
eral deposits.

Again, carbonate of lime, or of lime and magnesia, is among the most
commonly occurring products of the alteration of eruptive rocks.

Much of the crystalline limestone, or marble, which occurs in the
Azoic series, seems to us to belong to the segregated form of oceur-
rence. Some of it is certainly of this character, as has been already
mentioned in connection with the question of the organic character of
the Eozoén. If any of it is really bedded limestone — that is, rock which
was formed contemporaneously with the formation of the beds with
which it is associated — it seems to us clear that there are stronger rea-
sons for believing that this has been the result of a chemical precipita-
tion, than that the calcareous material has been formed through the
agency of life.

In default of other evidence of the presence of the results of organized
existence in the azoic rocks, it has been maintained by some that the
occurrence of ores of iron in extraordinary quantity in that series fur-
nished the desired proof. The facts are, however, that some at least of
the iron thus occurring is of eruptive origin; that the oxide of iron is a
mineral commonly and abundantly found making an essential compo-
nent of volcanic rocks ; that metallic iron is so found in large quantity,
— in one region, at least ; that there is strong reason for believing that
metallic iron forms, if not the whole, at least a large part, of the earth’s
interior ; and, finally, that a large portion of the material which comes
to us from outside our planet is metallic iron. All this, we think, is
amply sufficient for a refutation of the theory, that the presence of the
ores of iron is a proof of the existence of life at the time when the rocks
were formed in which those ores occur. ;

That it should be seriously maintained that the presence of sulphur
is evidence of the presence of organic agencies, seems to us still more
extraordinary than that the ores of iron should be so regarded. Sulphur
is one of the most abundantly diffused of the elements. The sulphu-

RESUME, AND GENERAL DISCUSSION. 545

rets of the various metals occur all over the world in vast quantity, and
as low down as mining has ever penetrated. The facility with which the
metallic sulphurets are decomposed by water when at a high tempera-
ture, and again the liability to decomposition, in a variety of ways, of
the sulphuretted hydrogen thus formed, are matters familiar to those
who are moderately well acquainted with elementary chemistry. We
need, in this connection, only state the simple fact, that, only a few
years ago, nine tenths of all the sulphur consumed in the world was
obtained from a region where all the facts show clearly that this sulphur
was the result of volcanic agencies. This alone is sufficient evidence on
the point in question.

It has also been claimed that the presence of apatite in the Azoic
rocks was an indication of the existence of life at the time these rocks
were deposited. Since phosphoric acid, probably largely in the form of
phosphate of lime, has been found in almost every kind of eruptive
rock, including granite, porphyry, and both ancient and modern lavas,
it seems that the theory which makes this mineral necessarily the
result of organic agencies, is not supported by facts. The earliest
plants and animals which required phosphoric acid for their develop-
ment cannot have taken it originally from the atmosphere, since it does
not exist there. They must, therefore, have obtained it from the earth,
unless we are willing to admit that it was created by them.

In view of all that has been set forth in the preceding pages, we con-
sider that we are fully justified in saying that the results of geological
investigation during the past thirty-five years have given no encour-
agement to the idea that below the well-known Primordial zone — the
Potsdam sandstone of American geologists — there is another series of
fossiliferous rocks. We think that the nomenclature of the forma-
tions should be made to correspond with the actual facts, rather than
with views which have no other than a theoretical basis. It would no
doubt be in harmony with the ideas and wishes of many palzeontolo-
gists, that there should be found a series of rocks occupying the position
of the Azoic system replete with organisms of a lower type than that
of the “ Primordial Fauna” of Barrande.* This desire has, no doubt,
powerfully contributed to the general acceptance of the Eozodn as a
relic of life, although — as it seems to us— the entire absence of forami-
niferal life in the lowest Silurian, throughout the world, places the

* “Tn his address to the British Association at Bath, he [Lyell] naturally
revelled with delight at the discovery of the Zozoon Canadense in the Lower Lau-

rentian.” — Murch, in Geol. Mag., II. (1865), 98.
VOL. Vil. —No. 11. S 35

546 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

evolutionists who accept the Eozoén in a more difficult position than
they would occupy if they rejected it altogether. It would be better
for them to take the ground occupied by F. Roemer, and say that “ the
strata containing the Primordial Fauna are the oldest fossiliferous rocks,
either because the rocks which are still older were originally unsuited
to the preservation of traces of life, or had become so in consequence of
subsequent changes, or else because the organisms which preceded the
Primordial Fauna were of too perishable a character to be preserved.”
At all events, let them recognize, with Roemer, that, so far as our pres-
ent knowledge goes, there are no fossils older than those of the Pri-
mordial Fauna.

Of all the results of geological and paleontological investigations
during the past half-century, there is no one so remarkable as the reve-
lation of the existence of the so-called Primordial Fauna. It is now
clearly established that there was a time when life was represented by
a few forms, which were essentially the same all over the globe. What
has long been known to be true for Europe and America has been
recently supplemented, for Asia, by the investigations of Richthofen in
China, where the peculiar primordial fauna seems to be largely devel-
oped, bearing, as Professor Dames remarks,* “an astonishing resem-
blance” to that of North America and Scandinavia. We have, namely,
in China, the same intermixture of trilobites, either belonging to the
genus Cloncocephalites, or closely related to it, together with the usual
primordial brachiopods, Orthis and Lingulella, which everywhere char-
acterize the oldest rocks in which any “ decipherable traces” of life
have been found. And, as if in utter contempt of all theories, we find
the trilobites disappearing entirely in early geological times, while the
brachiopods remain almost or entirely unchanged up to the present
epoch.

We have thus, as we think, clearly established the truth of the state-
ment, that the stratified rocks designated as Azoic by Foster and Whitney,
and included within the Archzean of Dana are—so far as present evidence
goes — non-fossiliferous. A persistent search for nearly half a century,
in all parts of the world, for traces of life in infra-Silurian formations
has not resulted in success. We consider, therefore, that geologists who
prefer the guidance of fact to that of theory, and who respect the law of
priority in nomenclature, will continue the use of the name Azoic for
the rocks described under that name by Foster and Whitney. At the
same time, it is desirable that a more definite understanding should be

* China, Vol. IV. p. 7.

RESUME, AND GENERAL DISCUSSION. d47

had as to the nature and age of the rocks to be designated by that term,
with especial reference to the name “ Archean,”
as already mentioned, and which has of late years to a considerable
extent replaced both the Azoic of the Lake Superior Survey and the
Laurentian and Huronian of the Canada geologists.

Dana, in that edition of his Manual in which he first introduces the
term Archzean, expressly says that “this formation [the Archean] was
first distinctly recognized in its true importance in the Report of Fos-
ter and Whitney on the Lake Superior region, where it was named ‘the
Azwic system,” so that the natural inference would be that he intended
his “ Archean ” to be the exact equivalent of the ‘‘ Azoic” of the Lake
Superior geologists. As defined by him, however, this new designation
has by no means the same signification as has the term which it was
apparently intended to replace.

In endeavoring to ascertain, by examination and comparison of the
statements made in reference to the Archean in the latest edition of
Dana’s Manual, what rocks this author really did mean to include in
that formation, we find considerable difficulty, so vague and contradictory
are the expressions of his views on this point.

We are distinctly told, however, that “ Archean Time” includes “the
era in which appeared the earliest and simplest forms of animals”; it also
embraces, as we are informed, “an era in which the physical conditions
were incompatible with the existence of life.” Thus it appears evident that
the author of the term Archean clearly intended to include under that
designation a series of stratified fossiliferous rocks, and also other rocks,
which preceded these in age, and were formed before life existed on the
globe.

But we are informed by the same author, that the first appearance of
life, of whatever rank that life might be, was an event of the highest
interest in the geological history of the earth. We would go even far-
ther than that, and say that it was an event far transcending in impor-
tance any other one which has ever taken place on this planet. And,
bearing this in mind, we would insist that so great a transformation in
the earth’s condition should be recognized in our geological nomencla-
ture. At all events, it would, as it seems to us, be in the highest degree
unphilosophical to call by the same name rocks which not only differed
in their geological age, but also in regard to the all-important point of
having been formed before and after the introduction of life upon the
globe,

The facts are, however, that the fossiliferous portion of Dana’s

introduced by Dana,

548 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Archean is only theoretically fossiliferous. He admits that “no dis-
tinct remains of plants have been found in it.” Yet, as his theoretical
views demand that plants should have existed before animals, he has
no hesitation in asserting that the presence of graphite is “strong evi-
dence that plants of some kind were abundant.” He even goes so far
as to state what these plants “must have been,” namely, marine dAlge,
lichens, and fungi. At the same time, although admitting that the
Eozodn is a somewhat doubtful organism, he thinks that “animals of
the lowest division of animal life were probably abundant” (in the
Archeean).

If it be true, as Dana believes, that there existed, at a time previous
to the epoch of the Lower Silurian, an abundance of animal and vege-
table life, then the strata deposited at the time this life existed should
be enrolled among the fossiliferous groups, with a special name indicat-
ing the relations which this life held to that of succeeding groups. They
certainly should not be called Azoic, nor should they, on the other hand,
be designated as Archzean, that name being used at the same time to
include rocks necessarily destitute of traces of life and belonging to
another epoch.

The truth is, however, that — so far as the present state of our knowl-
edge goes — the abundance of life with which the Azoic is endowed is only
a theoretical abundance. One could not well make a new paleontological
subdivision based on graphite and calcite ; hence the theoretically zoic
rocks have had, of necessity, to remain with the practically azoic.
Whenever a new fauna shall have been clearly recognized as actually
existing below the Primordial, then the fact will no doubt receive wel-
come recognition, and the “Age” or “ Epoch” be designated in accor-
dance with the nature of the fauna thus made known.

Dana, however, not only includes in his Archean the Azoic Series of
Foster and: Whitney, by him considered, on theoretical grounds, as being
a fossiliferous formation ; but he embraces under that designation, not
only the granites and old voleanic rocks- associated with the Azoic, and
which tuok their present position before the lowest Silurian strata were
deposited, but all eruptive, and indeed all crystalline rocks, with the
exception of such as are the result of the metamorphism of strata of
Silurian or post-Silurian age.

This is not only the necessary and logical inference from Dana’s defini-
tion of the term Archeean, but it results clearly from his special desig-
nation of the rocks which he embraces under that name. The crust of
the earth, according to his view, is Archean; or, as he says, this is the

RESUME AND GENERAL DISCUSSION. 549

“only universal formation.” He further remarks, that the Archean
rocks “‘ extended over the whole globe, and were the floor of the ocean
and the material of all emerged land when life first began to exist.”
Moreover, he expressly enumerates among the occurrences of Archean
rock those areas of the earth’s crust “which, in the course of the
upturnings of mountain-making, have been pushed upward among the
displaced strata, and in this way have been brought out to the light.”

Thus, according to Dana's definition of the term Archean, it would
be legitimate to include under that designation the granitic axis of the
Sierra Nevada, although that mass of rock seems clearly to have as-
sumed its present position at some time near the close of the Jurassic
epoch. In fact we do not see how it would be possible not to admit that
Etna, for instance, belongs to the Archzean, as defined by Dana, since
this volcano certainly consists of material which has been “pushed up-
ward” during the process of “ mountain-making,” and which evidently
formed a part of the exterior portion or crust of the earth.

The only way in which we could avoid designating all eruptive rocks,
including those of which modern volcanoes are built up, as Archean,
would be by taking issue in regard to exactly what is meant by that
frequently used term, the “crust of the earth.” A discussion of this
question would, however, lead to no very satisfactory result ; for it is
probable that hardly any two geologists would agree in their views, if
required to set forth exactly what they considered to be meant by the
phrase in question.

It is true that Dana does not follow out his own definition to its logi-
cal end; since he, for instance, speaks of the eruptive rocks of the
Connecticut Valley, not as Archean, but as Mesozoic. Others, however,
seem to have taken his language as it would appear on the face of it to
have been intended that it should be taken, and have called eruptive
rocks of various ages Archean, without any reference to the geological
time of their appearance in their present position, but solely because
they appear to have formed a part of the original “crust.”

That this method of grouping and nomenclature is entirely unphilo-
sophical, it seems hardly necessary for us to state. The first and most
important question in geological research is always, To what period does
the formation under investigation belong? If stratified, what geological
age is indicated by the fossils it contains? If eruptive, at what time was
it erupted? To class geological formations of different ages together is
extremely undesirable, and can only be admitted when the treatment of
the subject is a purely petrological one ; as if, for instance, we should

550 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

speak of “sandstones,” including those of all geological ages, but in
such connection as would make the fact that the rock was sandstone the
only point of importance with reference to the question under inyesti-
gation.

We would then call the eruptive rocks associated with the Azoic, and
which took their position in that formation before the deposition of the
Paleozoic formation upon them, Azoic eruptive, designating the special
rock by its lithological name. To the eruptive rocks of later date, we
would respectively give the designation corresponding to that of the
age or period when those rocks assumed their present position.

The granitic axis of the Sierra Santa Monica, therefore, is not an
Archean rock, but is a Tertiary eruptive, granitic, intrusive or axial
rock, because it took the position in which we now see it during the
Tertiary epoch.*

We come now to the second branch of our inquiry; namely, to the
consideration of the question whether the Azoic series can properly be
separated into two or more divisions, as has been done by the Canada
Survey and by those who have followed its lead.

If we adopted the views and nomenclature of Dana we should at once
admit that a division of the Azoic (Archean) into two distinct groups
was not only desirable, but imperatively necessary, since we can conceive
of nothing more unphilosophical than placing stratified fossiliferous rocks
in the same category with non-stratified and necessarily non-fossiliferous
ones. To designate by the same term the stratified deposits of Lake
Superior, which have remained as they now are since a time prior to
the deposition of the Lower Silurian, and the eruptive granitic axis of a
range which was not in existence until after the close of the Miocene
Tertiary, seems to us entirely unreasonable, even from our own point of
view, namely, that the Lake Superior rocks are in fact Azoic : how much
more so, then, from the standpoint of Dana, who considers these same
rocks to be fossiliferous !

If the Azoic rocks are really azoic, as we believe, then it follows, as

* Although some geologists and lithologists are unwilling to accept the fact of
the ovcurrence of an axial mass of granitic rock uplifting rocks of Tertiary age,
yet it is nevertheless true. Every feature which ought theoretically to characterize
such an occurrence, if it had really taken place, is present in the section offered by
the Santa Monica range. The sharp uplifting of the stratified beds in the immedi-
ate vicinity of the intrusive mass; the remarkable metamorphic action of the granitic
central axis on the adjacent stratified deposits, and the return of them to their nor-
mal conditions at a distance from the cause of the uplift: all this is plainly to be
seen, and there is but one explanation for the ensemble of the facts. —J. D. W.

RESUME, AND GENERAL DISCUSSION. 551

a matter of course, that the series thus designated can only be separated
into sub-systems on purely lithological grounds: if they are fossilif-
erous, as held by the Canada Survey, then it is equally clear that any
subdivisions proposed for them should have a palzontological basis.

It is true that the Canada Survey did, for a time, uphold the idea that
the Laurentian and Huronian were to be separated from each other on
fossiliferous grounds, namely, that the one contained the Eozodn and the
other did not; but this rather unsatisfactory basis of classification was
soon abandoned. Later, it has been maintained by Mr. Murray, of the
Newfoundland Survey,* that certain peculiar forms, supposed to be of
organic origin, were characteristic of the Huronian of that region. Of
one of these supposed fossils (the Aspzdella) the paleontologist of the
survey could only say that ‘its general aspect is that of a small Chiton
or Patella” ; but he hastens to add, that “it is not probable, however,
that it is allied to either of these genera.”t To us, the general aspect
of the fossil in question, as figured by Mr. Billings, is that of a concre-
tion intersected by small irregular cracks, and much more resembling
the so-called Septaria than anything organic.

Specimens of Aspidella sent us by Mr. Murray, however, do not
resemble in any respect the fossil figured by Mr. Billings. There are
several indistinct impressions on the fragment of rock, neither of them
like that fossil, and none of them necessarily of organic origin, at least
so far as we are able to discover. They look more like spray markings
than anything else with which we are able to compare them.

Of equally dubious character is the otber of these so-called fossils, by
which it is believed by the Canada geologists that the Huronian can be
separated from the Laurentian. We refer to the Arenicolites spiralis,
mentioned by Mr. Billings in the “ Paleozoic Fossils,” ¢ of which no de-
scription is given by him, it being only said to “occur near St. John’s,
in the Huronian.” It is added, however, that “a more detailed descrip-
tion will be given hereafter.” The real nature of this supposed fossil has
already been sufficiently indicated by Dr. Wadsworth.§ Whether the
Arenicola didyma, and the Arenicolites sparsus, of Salter, are or are not of
organic origin, it is unnecessary here to inquire. That palzeontologist con-
siders them “ burrows of annelides.” We see little resemblance between
these forms as figured by him and the Arenicolites of the Canadian Survey. ||

* See ante, p. 380.

+ Geological Survey of Canada, Paleozoic Fossils, Vol. II. Part I. p. 77.

El. ¢., p- 11- § Science, I. 39.

|| A large number of specimens of the Arenicolites were collected by Dr Wads-
worth in the vicinity of St: John’s.

552 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

In the latter we see no indication that anything possessed of life had
to do with their formation. The Arenicola is mentioned by Zittel,
together with many other equally problematic bodies, which that
eminent paleontologist dismisses with the remark that ‘these names
have no zodlogical significance.” *

Since paleontology affords no assistance in dividing the Azoic (Ar-
cheean or original Laurentian) into two or more sub-systems, it remains
to be seen what does justify such a division ; and here a few remarks in
regard to systems in geology will be desirable. No fact is better or
more generally recognized than this: that geological time can only be
kept by the aid of paleontology, the entire systematic classification of
the formations, and their separation into “ages” and “epochs” being
exclusively based on the order of succession of organic life. No one
would think of defining the period of a geological event by saying that
it took place in the “sandstone epoch,” or in the “limestone epoch.”
3ut this is, in point of fact, essentially what has been sought to be done
in dividing up the Laurentian first into two groups, the Laurentian
and Huronian, and afterward into various other subdivisions, as shown
in the preceding pages. Such subdivisions, when the work has been
well done and the order of superposition of the rocks correctly deter-
mined, may be of value, but only of local value, and they must be recog-
nized as having no claims to be considered generally applicable to all
regions.

To what depths of confusion geologists have descended in their en-
deavors to make out a distinct order of succession in the various litho-
logical developments of the Azoic, and in their determination to uphold
the divisions introduced by the Canada Survey, must have been made
thoroughly apparent by what has been given in the preceding pages.
We have seen the rocks moved about, from year to year, like the pieces
in a Chinese puzzle, in a vain attempt to create the desired figure. And
when to a false theoretical basis has been added entire incompetence in
matters of geological observation and lithological determination, the
confusion which has resulted has—as has been shown — become some-
thing almost incredible.

We may now proceed to consider, a little more in detail, how such
methods as have been shown in the preceding pages to be current in the
study of the crystalline rocks have come into vogue in this country, and
to some extent abroad. That this has taken place largely through the
influence of the Canada Survey under its old organization, it is thought

* Zittel, Traité de Paléontologie, Tom. I., 1883, p. 576.

RESUME, AND GENERAL DISCUSSION. 553

no one will deny; and for the purpose of throwing light on the origin
of the methods in question we naturally seek to ascertain what were the
principles by which that survey was governed. No one conversant with
the history of that organization will doubt that its methods and pur-
poses were arranged and formulated by the geologist who was its head
during the first twenty-seven years of its prosecution: that none of his
subordinates did originate them, may readily be inferred from the fact
that the second in authority had been trained as a midshipman, having
previous to his joining the survey had no other experience than that
gained on the Ordnance Survey of Great Britain, while he remained
essentially an explorer and a stratigraphical geologist in all his methods.
That the one who for so many years served as the mouthpiece of the
Canada Survey did not prescribe its methods, can be readily inferred
from his own statement,* that, for “ official reasons,” he did not dissent
from Logan’s views, the correctness of which he for many years doubted ;
and from the fact that at the very time when he says he did not believe
in these opinions he was warmly supporting them in print. This is
further enforced by the fact, that, almost as soon as Logan resigned,
Hunt began to endeavor to overturn the work of the survey and the
teachings of his previous years. In fact, he has quite recently started
on a third crusade, with principles designed to upset all he has written
before.f

The only other officials who, before the closing years of Logan’s work,
bore any prominent part in the study of the older crystallines were a
young civil engineer, and two persons whose knowledge of geology’ had
been chiefly acquired by practical cultivation of the soil.

Logan alone then seems to have been the motive power of the survey ;
and it now is necessary to ascertain in what way and under what influ-
ences he was prepared for his geological work.

From Harrington’s Life of Logan we learn that the latter was em-
ployed in the counting-house of his uncle, in mercantile pursuits, from
1817 until about 1831, when he went to Wales as the business manager
of some copper-smelting works in which his uncle was interested. Later,
he added to this the business of coal mining. Since he requests his
brother to purchase and forward to him “some good work on mineral-
ogy and geology, Dr. Dickson will be able to tell you which are best,”
we may infer that he not only knew nothing of the subjects of, or the

* See ante, p. 458.
t The Origin of Crystalline Rocks. Abstract of a paper read before the Royal
Society of Canada, May 21, 1884.

554 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

workers in, geology or mineralogy, but also that he, at that time, had no
books relating to these subjects, although he was then thirty-three years
of age.*

In 1833 he appears to have begun his mineralogical and geological
work in an amateurish way ; and later to have undertaken to lay down
the geology of the “South Welsh Coal Basin” on the maps of the Ord-
nance Survey. A description of the geological map thus made consti-
tuted his first scientific paper, which was readf in 1837, at which time
he was thirty-nine years of age.

Logan gave up his business in Wales in 1840, proceeded to Canada ;
and, in 1841, visited the coal-fields of Nova Scotia and Pennsylvania.
At the time of his appointment as Director of the Canadian Survey, in
1842, the only scientific papers he had read before any scientific body
(only one of which had been published) were devoted to questions
relating to the geology of coal; and in their recommendations of him
for the directorship De la Beche, Murchison, Sedgwick, and Buckland
placed all their emphasis on his skill as a geological surveyor of coal-
fields. £

It can thus be seen that Logan, who was forty-four years old, had
reached an age when most men’s ideas and methods are fixed, the re-
mainder of their lives being spent in developing them. He was purely
a stratigraphical geologist, having had experience only in the study of -
the well-marked stratified formations. Having then and ever after “only
a limited knowledge of chemistry, mineralogy, and paleeontology,” § and,
so far as we can learn, no acquaintance with crystalline and eruptive
rocks, beyond that acquired in the examination of some dikes in the coal
measures, Logan was set at work in a country in which he was brought
face to face with some of the most difficult problems with which a
geologist has ever had to cope— problems which demanded for their
solution a training entirely different from that which he had. Now at
the period when Logan began his study of geology, and during much of
the time when he was the head of the Canadian Survey, the rival theories
of Werner and Hutton were yet bones of contention, in a disguised form,
while Lyell’s publications were exerting a great influence. If we turn
to Logan’s early reports on the Canadian geology it will be seen that
in the study of the older crystalline rocks he follows Lyell implicitly.

* Harrington’s Life of Logan, 1883, p. 50.

+ Proc. Brit. Assoc., 1837, VII. (sec.), 83-85.
¢ Harrington’s Life of Logan, pp. 126-132.

§ Ibid., p. 397%

RESUME, AND GENERAL DISCUSSION. 555

The latter held that the foliation planes in all gneisses were the results
of stratification and proof of deposition from water — the sediments
subsequently having been altered by subterranean heat. Those rocks
which had been classed as primary, Lyell called hypogene, dividing them
into an unstratified or plutonic series and an altered or metamorphic
series. He also contended that “all the hypogene strata, beautifully
compact and crystalline as they are, have once been in the state of
ordinary mud, clay, marl, sand, gravel, limestone, and other deposits
now forming beneath the waters.” *

Following the above views of Lyell we see Logan at the outset giving
the name “ Metamorphic Series” to the older crystalline rocks, assum-
ing that the planes of foliation were stratification planes ; and stating
that the “‘syenitic gneiss” or granite possessed “an aspect inducing the
theoretical belief that they may be ancient sedimentary formations in
an altered condition.” ft Such a belief, if simply looked upon as a the-
ory, to be proved or disproved by the light of future evidence to be
carefully sought for, would not have done great harm; but such was
not the method of the Canada Survey, whose officers never took one
step toward ascertaining the correctness of their theoretical belief. Yet
we find Logan declaring, in 1863, that the Geological Survey had
shown, in 1846, that the Laurentian consisted of “a series of meta-
morphic sedimentary strata underlying the fossiliferous rocks of the
province,” Hunt, in 1855, making a similar statement.

One who carefully reads the reports of that survey can hardly fail to
observe that the entire geology of the crystalline rocks was worked out
on the supposition that they were stratified, and that the laws of their
relations were those that Logan had employed in the study of coal-
fields, a difference in the dip or strike of the foliation being considered
sufficient for the establishment of a new geological formation. No
examination seems to have ever been made for the purpose of ascer-
taining the origin and history of the rocks in question.

We will now proceed to examine, a little more in detail, the way in
which the Azoic or Laurentian rocks came to be divided into two groups
—the Laurentian and Huronian. This division originated in the con-
founding by Logan of the basaltic volcanic rocks interbedded with the
Potsdam sandstone of Keweenaw Point with the basic or greenstone

* Lyell’s Principles of Geology, 1833, 1st ed., III. 367, 374, 376; 1834, 3d ed.,
IV. 280, 281, 292; and all subsequent editions of the Principles and Elements, or
Manual.

t Ante, pp. 331, 332. $ Ante, pp. 338, 342..

556 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

portion of the Azoic of Foster and Whitney as developed north of Lake
Huron. The two series possess nothing in common beyond the fact
that both are basic and both carry copper— one in the native state and
the other in the form of the sulphide. Instead of admitting that the —
acidic and basic rocks of the Azoic formed one mixed series of eruptive
and detrital rocks, Logan here left the gneissic and granitic rocks in the
Laurentian and placed the basic ones in a new series—the Huronian —
on account of the known unconformability of the Keweenaw Point rocks
with the Azoic. Later Logan admitted sub sclentio the mistake he had
made in tniting the Keweenaw Point rocks with those north of Lake
Huron, thereby abandoning the data on which the Azoic was separated
into two series; yet he persisted in his two divisions, which from that
time forward in reality rested exclusively on a lithological basis.

The publication, in 1863, of a volume ostensibly giving the evidence
and data as obtained during the previous years of the survey, but which
in reality presented as proved that which had only a theoretical basis,
with the evidence largely omitted or disguised, contributed greatly to
the overlooking of the previous reports, and the acceptance of this as a
correct statement of results obtained, and of the nature of the evidence
by which they were supported. This was further aided by the persist-
ent misrepresentations of the facts made by Hunt, as pointed out in the
preceding pages. These misrepresentations have been so persistent and
glaring that we are compelled to say that we consider that Hunt’s
“Chemical and Geological Essays,” his “ Azoic Rocks,” and his publica-
tions generally, cannot be taken as any authority as to what he or any
one else has previously taught or held, until his quotations and state-
ments shall have been carefully compared with the original publications.
In this matter we are fully in accord with that which Dana has again
and again earnestly claimed.

If we examine the often repeated statement that the Huronian un-
conformably reposes on the worn edges of the Laurentian and contains
the débris of the latter, it will be found that in every case in which the
rocks referred to these two formations were found in contact in the
Canadian district (seven in number), the Huronian, with but two excep-
tions, is said to be conformable with and to generally pass imperceptibly
into the Laurentian. In one of these two exceptions the rocks show
mutually intrusive relations, and in the other the Huronian abuts
against and runs under the Laurentian.

In all cases in which pebbles and fragments of the Laurentian have
been found in the Huronian, they were seen occurring high up in the

~

RESUME, AND GENERAL DISCUSSION. 557

latter series, and not forming basement conglomerates. All the other
so-called proof of unconformity has been made out of the fact that the
strike of the foliation in the two formations when not in contact has
been found to be discordant — worthless evidence unless the rocks ob-
served in both formations be proved to be sedimentary and the foliation
be shown to be coincident with the stratification. Now if the Lauren-
tiun was an old metamorphosed sedimentary formation which had been
upheaved and contorted, and on whose worn edges the Huronian had
been laid down, the evidence of the fact ought to be overwhelming in
amount after the country has been studied for so many years. Wher-
ever the Primordial is found in contact with the Azoic, the basement
conglomerates and the worn edges of the older Azoic are to be found,
and a like condition should be observed if the Huronian is distinct from
the Laurentian. But such is not the case, even Selwyn going so far as
to declare that the supposed unconformity cannot “be said to be based
on or in accord with the stratigraphical observations of either Logan,
Murray, Bell, or myself.” *

It is well known that any eruptive rock so soon as it comes in contact
with erosive agencies will yield fragmental material even before it is
cold, and that much eruptive matter is ejected in a fragmental state, so
that in a mixed series of eruptive and detrital rocks nothing is more
common than to have the débris of one enclosed in another, without
thac enclosure proving that the rocks differ in geological age. This is
well known to be the case with the copper-bearing rocks of Keweenaw
Point, and it has been shown that the iron ores of the Marquette dis-
trict, which form a constituent part of the so-called Huronian, are over-
lain by a conglomerate containing the débris of the former — yet both
‘are by every geologist placed in the same series.

The basis of fact which forms the main support of the twofold division
_of the Archzean — including under that designation all rocks lying below
the lowest fossiliferous series—is this: the axial or eruptive portions
of disturbed and mountain regions are largely’ granitic and gneissoid in
character. These granitic, granitoid, and gneissic masses are brought to
light in the cores of great mountain chains, where long-continued uplift
of the original crust of the earth has, through a succession of geological
ages, been furnishing the material from which the sedimentary forma-
tions were built up. That the gneissic or gneissoid rocks are closely
allied to the distinctly granitic and not necessarily metamorphosed strati-

' fied deposits is clear to us, as the result of long-continued investigations

* Notes on the ‘‘ Life of Sir W. E. Logan,” 1883, p. 3.

558 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

in regions where rocks of this kind occur. Not that all gneisses are of
this character ; but those are ordinarily so which with granite make
up the axial masses of disturbed regions. That the parallel structure
of the materials forming gneiss is not necessarily the result of sedimen-
tation seems to us clearly to result from that which has been done both
in experimental and field geology within the last few years. It can-
not be denied that a foliated arrangement or a parallel disposition of
the mineral elements of various sedimentary rocks can be, and often
has been, induced in them after their deposition, and that this parallel
arrangement is not by any means necessarily coincident with the planes
of stratification. This fact alone is absolutely conclusive in favor of
the idea that parallel arrangement of the mineral constituents of a rock
— in other words, a gneissic structure, in rocks of the granitic family —
is not proof of sedimentation.

Overlying the granitic and gneissic axial rocks we are likely to find
—and in many cases do find —the stratified masses which were formed
from the pre-existing crust themselves usually highly metamorphosed,
because formed at a period of great chemical and mechanical activity.
With these stratified and highly altered masses are associated eruptive
materials — both interbedded and injected in dike-form — these also
often greatly metamorphosed, and to such an extent that their original
character is only with difficulty, and with the aid of the microscope, to
be recognized. This protrusion or forcing out of eruptive materials
seems to have followed the preceding uplift of the original crust, if not
as a necessity, at least as something extremely likely to occur, as is
shown by the fact that in so many great mountain chains we find vol-
canic activity more and more predominating with the progress of geo-
logical time. Since these eruptive materials come from a gradually in-
creasing depth below the surface of the original crust, they are more
basic than this, and, since as a rule they contain more iron than that
crust, are darker-colored than the masses by which they are directly
underlain. Hence the detrital beds formed from the débris of these
more basic materials are themselves of a dark color, and as a result of
their metamorphism we have the various slates, argillaceous, talcose,
and chloritic, which so commonly rest upon the granitic and gneissoid
rocks which form the core or axis of the disturbed region. With these
slaty rocks are also associated limestone masses, which — so far as our
observations go —are not ordinarily interstratified with the slates, but
are of the nature of segregated deposits, having been formed poste-
rior to the formation of the sedimentary beds with which they are asso-

RESUME, AND GENERAL DISCUSSION. 559

ciated, while the metamorphic agencies were at work making over the
beds into the crystalline form in which we mow see them. Similar re-
sults have here and there been produced, although not on so grand a
scale, during the succeeding geological ages, as we see exemplified in the
veins and segregated deposits of later times, which are so well known
to those who have occupied themselves with the study of vein phe-
nomena. That these segregated masses of calcareous materials, which
occur as veins and which are often metalliferous, are the result of or-
ganic agencies, no one who has studied them with care has ever for a
moment supposed ; and, as has been already stated, we believe that all
the evidence is strongly in favor of the idea that the calcareous masses
of the Azoic are also deposits from aqueous solution without the inter-
vention of living organisms.

Pursuing the investigation still further, it is seen that the efforts of
Logan to apply the principles of his stratigraphical geology to the crys-
talline rocks led naturally to the adoption of supplementary principles
in order to sustain the sedimentary character of the rocks and to aid
in their identification. Since the two series could not be distinguished
by paleontological evidence, it became necessary to uphold the idea
that lithological characters could take the place of palzeontological ones
as a basis for the arrangement of rocks in chronological order, and their
division into groups. But this required that a still more important
step be taken, — namely, to insist that all crystalline rocks were of
Azoic age and that all non-crystalline detrital ones were Paleozoic or
later; and this principle is now openly or tacitly assumed in all work
in which the Canadian methods are followed. To say that crystallines
necessarily differ in geological age from the non-crystallines, is equiva-
lent to claiming that the crystalline lava that has flowed from Vesuvius
is not of the same geological age as that of the ashes and mud which
preceded and followed its eruption ; for such we have found in some
districts to be the exact relations of the older crystallines to the non-
erystallines. Furthermore, it is now known that fossils occur in Scan-
dinavia, Belgium, California, and elsewhere in crystalline rocks, —as,
for instance, ammonites in greenstones.

In the application of their principles the Canadian Survey found it
convenient to still further differentiate the rocks that had been classed
with the Laurentian and the Huronian, and especially with the latter,
since these are in part eruptive, in part detrital, and in part probably
segregated deposits, so that their entire conformability with one another
could not be expected. The first to be thus separated were the coarsely

560 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

erystalline basaltic rocks, or the gabbros, which, on the ‘theoretical
belief” that they were stratified, and on account of their cutting across
the strike of some of the limestone belts — as any eruptive mass natu-
rally would — were placed in a system newer than the Laurentian
proper. Subsequent investigations have shown that these gabbros are
—§in part, at least —interbanded with the Laurentian limestones, so
that they must be of the same age as those limestones, or else later in-
trusions. That they are eruptive rocks is the testimony of the present
director of the Canadian Survey, and is in accord with the investigations
of the best petrographers the world over; while our own investigations
in the Adirondacks have led us to similar conclusions. Moreover they
have been found by us occurring in dikes in the granite of Eastern
Massachusetts.

Further, the Hastings series, although at first looked upon as con-
formable with and said to pass gradually into the Laurentian, was, on
account of its having limestones associated with it and in conformity
with the earlier results of Vennor, placed as an overlying formation.
Vennor’s work, however, having been continued ten years longer, ap-
peared to demonstrate that the Hastings series was continuous with a
lower portion of Logan’s Laurentian. But Hunt, accepting the earlier
work and ignoring the later labors of Vennor, has made out of the
Hastings schists and granites the Montalban, and out of the limestones
and quartzites the Taconian.

Again the felsites (orthopyres, petrosilex, etc.), which are known to
be the old representatives of the modern rhyolitic lavas, and like them
to occur in dikes, or to take the form of lava-flows, ashes, etc., and
which were first united with the Huronian, have now been erected into
a separate series — the Arvonian.

Only lithological principles are now used in making these divisions,
and every fact pertaining to the origin and relations of these rocks is
ignored ; and since, while it is assumed that all these rocks are sedimen-
tary, they were found to occur in dikes and other eruptive forms, it
became necessary to hold that all eruptive (including voleanic) rocks
were the products of a metamorphic (aqueo-igneous) action. Hence
it was claimed that all these rocks had been deeply buried and then
denuded,* and most extravagant views became current regarding de-
nudation.

It thus came about that the coarser-grained granitoid and gneissic
rocks were set apart as Laurentian; the gabbros and some of the more

* Advocated by Lyell in 1833 and later.

RESUME, AND GENERAL DISCUSSION. 561

coarsely crystalline diabases and diorites were erected into the Norian ;
the felsites and quartz porphyries were placed as the Arvonian; the
finer-grained diorites, diabases, melaphyrs, and chlorite schists were
formed into the Huronian; the more friable granitic and gneissic rocks
with the mica schists were classed as Montalban; and the quartzites,
limestones, and argillites were united into the Taconian. Of course in
each case the metamorphic fragmental forms of each rock were placed
with the rocks they resembled, while the other forms of crystalline rocks
were distributed through the groups. We give below these arrange-
ments in a tabular form; and in order to aid those geologists who
believe in the lithological subdivision of the crystalline rocks into
geological formations, we would propose another arrangement, which will
be still more in harmony with their views. Thus we would place all
the granites, gneisses, and syenites in the Laurentian ; erect the mag-
netites, menaccanites, hematites, and their associated jaspilite into a
new series ; do the same for the peridotites, including the serpentines ;
but leave the Norian, Arvonian, and Huronian as they now stand. Fur-
ther, we may place the porphyrites in a new group; limit the name
Montalban to the mica schists, and the Taconian to the limestones;
and place the quartzites, conglomerates, and argillites in three additional
and distinct groups. All these divisions can be supported by quite as
satisfactory evidence as that on which the formations now accepted are
sustained. For instance, there is indubitable evidence that the Mar-
quette iron ores are unconformable with the Huronian ; the segregated
limestones with their associated rocks ; the eruptive peridotites, and the
resulting serpentines, with theirs, ete.
‘

Present Chronological Arrangement of the Crystalline Rocks.

LAURENTIAN. : ee
Granites and Gneisses.

Coarse-grained Trachytic
Rhyolitic Rock. ‘

Coarse-grained Basaltic 7 Gabbro, and some Diabases
Rock. ‘ Norran. ; and Diorites.

{ Coarse-grained compact

Compact Rhyolitice and .
Jaspilitic Rocks.

Fine-grained Basaltic k

vay Felsite, Petrosilex, Quartz
PET TERA | Porphyry, Jaspilite.
§ Diorite, Diabase, Melaphyr,

HURONIAN. Chlorite Schist.

Rocks.

Friable Granites, Mica

Trachytie and Metamor- ‘
Schists.

phie Rocks.

Quartzites, Limestones

¢
MOoNTALBAN. /
} and Argillites.

Metamorphic Rocks. TACONTAN.

VOL. VII. —NO. 11. 36

562 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

Proposed Chronological Arrangement of the Crystalline Rocks.

LAURENTIAN . . . . Granites, Gneisses, and Syenites.

SIDERIAN. . . . . . Magnetite, Hematite, Menaccanite.

OpH1AN . . . . «. © Peridotites, including Serpentines.

Norran . . . « .« ~ Gabbros, coarse Diabases and Diorites.
ARVONIAN . . . .~ « Felsite, Quartz Porphyry, Petrosilex, Jaspilite.
PORPHYRIAN, . '.. . Porphyrites.

Huronran . . . . . Diorites, Diabases, Melaphyrs, Chlorite Schists.
MonTALBAN . . . .« Mica Schists.

CrRYSTALLIAN . . . ~ Quartzites, Quartz Schists.

TacoNIAN . . . «. - Limestones.

GLACIAN. . . . ~. - Conglomerates.

PELODIAN « js +s «./) Adeallipess

It would seem that enough has been given to show that the basis of
the subdivisions of the Azoic rocks in Canada was a purely theoretical
one, and that Logan’s methods and opinions were such, when he com-
menced the survey, that no different result could have been anticipated.
It was just as if a geologist should apply the principles used in study-
ing the undisturbed strata of the Mississippi Valley, or the Grand Cation,
to the elucidation of the structure of Mt. Autna, and attempt to divide
its flows and dikes into distinct geological formations. One may take
the utmost care in all his measurements, may count every step from
Gaspé to Georgia, and make most beautiful maps and sections ; yet, if
he is unable to determine the characters of the rocks he is mapping, his
work is worse than worthless, for every obscure dike that is met with
and every segregated mass of limestone causes a new fold and contor-
tion to be inserted. From the fact that the surface distribution only
was sought in the Grenville series — in which the limestones are prob-
ably of chemical origin — it would appear to us that no reliance is to
be placed on Logan’s much vaunted work and sections here, beyond the
question of surface distribution ; and such seems to be the case with all
his and his assistants’ work on the crystalline rocks.

The present director of the Canada Survey appears to be sincerely
endeavoring to base his work on better methods than those current
under Logan’s administration. All who are interested in the solution
of the difficult problems of Appalachian geology will sympathize with
him in these efforts; for, as has been already suggested, that which is
done in Canada will, ¢f well done, be of great assistance to those working
on the south side of the Dominion line.

APPENDIX.

Srvce the first part of this work was put in type, another report on
the geology of Keweenaw Point has been published by Professor Irving,
in the Third Annual Report of the Director of the United States
Geological Survey. The state of our knowledge up to the time of the
casting of that portion of the work has been presented on pages 76-157,
482-492. in Irving’s report the before-mentioned observations (ante,
pp. 115, 116, 482-484) of Wadsworth at the Douglass Houghton Falls
are accepted and pronounced correct in every particular but one.
Irving then acknowledges that the copper-bearing rocks are continuous
with the eastern sandstone below the falls; but in order to escape the
dilemma in which this places him, he says that below on the stream is
a covered space between the true eastern sandstones and those which
every previous observer had called such, and that here is the junction
between the sandstone and Keweenawan series. This space he said
Wadsworth had bridged over in his imagination. To this the latter
replied, “that, by digging in the stream and on the banks of the
ravine, he had actually traced (not imagined) the relations of these
rocks, going from those dipping five degrees up to those dipping
twenty-five degrees, and that they were seen to form a continuous
super-imposed series, no such cliff as imagined [by Irving] existing
between them.” *

Irving further claimed that at the junction of the sandstone and
traps on the Hungarian River (ante, pp. 113-115) the sandstone was a
loose piece, or, if not, the basaltic rock surely was, and that the prevail-
ing dip of the saridstone was to the southeast. To this “ Wadsworth
replied that the dips given in the report [Irving’s] appeared to have
been taken from the frost-dislocated rock on the sides of the stream,
while his [Wadsworth’s] were taken in the bed of the stream, when the

* Science, 1884, III. 553..

564 THE AZOIC SYSTEM AND ITS SUBDIVISIONS.

water was exceptionally low. He further stated that the sandstone at
the junction was continuous with that seen below ; that it extended
across the stream and into the banks on both sides; while the baking
and induration of it showed that it must have been overflowed by some
heated rock. Again: the basaltic rock extended across the stream into
both banks, and was found to underlie the conglomerate, and that he
dug the débris of the former out of the overlying base of the latter, All
this, he said, showed conclusively that these rocks were in situ, and
proved that here the eastern sandstone and Keweenawan series were
one and the same ; also that this series could not be maintained, as first
established.” *

Irving further denies the general correctness of Wadsworth’s pre-
viously published statement relating to the sandstone quarry near
Torch Lake (ante, pp. 117, 118), and maintains that, while he (Irving)
finds traces of the trappean material in the sandstone, he does not find
any of the porphyry material belonging to the conglomerates of the
“Keweenawan series.” This claim proves too much, for if this sand-
stone had been deposited against the mixed lava flows and detrital
rocks of the copper-bearing series as Irving holds, and made up of their
ruins, there the sandstone should be full of their débris, and the old
thyolitic and trachytic material ought to be far longer retained than the
more easily perishable basaltic material; since even in the sandstones
intercalated with the traps the basaltic débris is comparatively rare.
Now Irving’s statements are directly opposed to his own views; and the
same may be said of the testimony of all those who claim that the sand-
stone near the traps is composed of different materials from those of the
detrital rocks of the so-called Keweenawan series.

Wadsworth has since re-examined the specimens in the collection
made with express reference to retaining the evidence in behalf of his
previous statements, (ante, pp. 117, 118,) and he reiterates those state-
ments with the exception of this correction, that on page 117, third
line from the bottom, the word felsitic is misprinted feldspathic, as the
context shows. He finds in these specimens an abundance of the bi-
pyramidal quartz peculiar to ancient and modern rhyolitic rocks, and
also the variation between the bedding planes and jointing, both being
evident in the hand specimens. The previous statement (ante, p. 488),
that Irving had adopted Wadsworth’s view that the pebbles of the Ke-
weenaw conglomerates were largely old rhyolites and trachytes, Irving
denies, since the director of the U. S. Geological Survey had misstated

* Science, 1884, III. 553.

APPPENDIX. 565

his (Irving’s) views.* Irving, in his claim that in “the Keweenaw series
occur, as I was the first to announce, so far as I am aware, original
masses, not only of basic but also of acid eruptives, and of eruptives of
intermediate acidity, the various kinds constituting a continuous series
from the most basic to the most acid,” * is incorrect, since all this was
distinctly announced some thirty years before in the Report on the
Copper Lands by Foster and Whitney (1850, pp. 58, 59, 70, 71, 78,
79) in the language of the science of that time.

In the Third Annual Report before referred to, Irving further incor-
rectly states that Foster and Whitney regarded al/ the acidic or jaspery
rocks as metamorphosed sandstones, and all the conglomerates and sand-
stones as friction detritus.t

In Irving’s report there is further given a description of the micro-
scopic characters of the acidic rocks of the “ Keweenawan series,” in
such a manner as to lead any one not conversant with the history of the
subject to suppose that Irving was the first to make such an examina-
tion, although he was perfectly well aware of Wadsworth’s previous la-
bors in that direction (ante, pp. 113-112).

Attention has been previously called to his proceeding in the same
manner in reference to the Marquette rocks (ante, pp. 497, 498). This
statement was, however, met by Irving in a sophistical and mislead-
ing manner, and by a denial the correctness of which we do not grant.
Later, Irving appears to have tried to correct his former injustice to the
best of his ability.t

Nothing appears in the recently published first and third volumes
of the final report of the Wisconsin Survey calling for any modification
of the earlier part of this work, since one volume is devoted to a theo-
retical discussion of assumed data, and in the other all the Azoic areas
contained only one of the divisions of such rocks made by the Wisconsin
geologists, and they are assigned to such divisions on lithological evi-
dence only.

* Amer. Jour. Sci., 1883 (3), XXVI. 321, 322.

t Foster and Whitney, Copper Lands, 1850, pp. 58, 59, 70, 71, 78, 79, 103, 109.
t Amer. Jour. Sci., 1883 (3), XXVI. 321, 322; 1884, XXVII. 130-134.

AvcusT, 1884,

INDEX.

[Bull. Mus. Comp. Zodl.,

ACTINOLITE, joining quartz grains, 54 ;
needles of, in garnet, 47 ; secondary ori-
gin of, 39, 47.

Actinolite rock, contact with granite, 53.

Actinolite schist, relation to the iron ore, 35.

Agassiz, A., Eastern sandstone deposited
later than the trap, 96; geological. struc-
ture at Douglass Houghton Falls, 115;
mistakes the views of Foster and Whit-
ney, 96; relation of sandstone and trap
near Torch Lake, 95, 96.

Agassiz, L., on the origin of copper deposits,

Alteration products in plagioclase, 56.

Amygdaloid at base of traps, 81; defined,
128; deposited by water, 94; presence on
Keweenaw Point denied by Bayfield, 77.

Amygdaloidal structure, origin of, 78, 81,
84, 86, 87, 88, 100, 101, 123, 129.

Amygdules, composition of, 130.

Analcime, igneous origin of, 80.

Andesite, probable occurrence of, 37, 38.

Apatite, in an old trachyte, 120; in gneiss,
57; microlites of, 37.

Argillaceous detritus, alteration and crystal-
lization of, 58.

Argillite, 28; south of Marquette, 37.

Asbestus, chrysotile mistaken for, 66.

Ash-bed, confounded with detrital deposits,
112, 113; copper deposits in, 125; how
formed, 91, 112: poor in copper near
veins, 125; structure of, 125; tongues
of, in trap, 113; tongues of trap in, 125.

Atlantic Mine, character of copper deposit
at, 129; supposed “ash-bed” of, 125;
thermal water action at, 125, 126.

Augite, alteration to hornblende, 37, 46:
altered to hornblende and chlorite, 39;
altered to hornblende and viridite, 42; al-
tered to viridite, 37: cut by feldspar
erystals, 37, 42; forming cores in horn-
blende, 37.

Australia, origin of placer gold of, 17.

Azoic age of iron region, 26.

_ Azoic system, defined, 7, 8, 9; first proposed

by Foster and Whitney, 7; its relation to

Geol. Series I. No. 1.}

the Silurian system, 9; lithological char-
acters of the, 8, 9.

Bacon, D. H., 131.

Banding, no proof of stratification, 28.

Bannan, Benjamin, volcanic origin of iron
ore, 16.

Barite at McComber Mine, 51.

Basalt, alteration of, 70.

Basaltic rocks, alteration of, 105.

Base, alteration of, 37, 40, 44; alteration
products taken for, 44; forming stone
cavities, 42; globulitic form of, 40;
unaltered globulitic, 44.

Bauermann, H., derivation of copper from
the sandstone, 127; origin and sequence
of minerals 95 ; on the deposition of the
copper, 94, 95.

| Bayfield, H. W., granite and trap of Kewee-

naw Point older than sandstone, 77 ; “ Old
Red ”’ age of sandstone, 77.

Beaches, sea, in iron district, 31.

Bell, Robert, copper-bearing rocks of Per-
mian or Triassic age, 97.

Bete Grise Bay, dip of sandstone at, 88.

Bibliography of the Geology of Lake Supe-
rior, 133-157.

Bigsby, J. J., Cambrian age of sandstone,
90 ; sandstone of “‘ Old Red” age, 77.
Biotite, alteration product of hornblende,

56; connecting quartz grains, 54; cut
by muscovite, 56; in granite; derived
from schist, 54; secondary origin of, 36,

42, 46, 47.

Bohemian Mountains, origin of, 86.

Bolton, G. D., 132.

Braintree, Massachusetts, slates of, 72.

Breccia, overlying iron ore, 30.

Brooks, T. B., assumption that foliation and
stratification are coincident, 25; bedded
character of the iron ore, 18, 19; coneln-
sions based on lithological characters, 24;
copper-bearing rocks conformable with
Huronian, 99, 100; evades the conclu-
sions logically resulting from his own
work, 24; formation xx. of, 71, 72;

rat INDEX.

granite dikes never seen in the Marquette
Series, 74; his methods of work, 71;
Lake Superior sandstone, always horizon-
tal, 100; no basis for formations of, 75 ;
on Huronian age of granite, 24; on indi-
cations of stratification, 18; on Lauren-
tian age of actinolite rock, 53; on
magnesian schists, 20; on origin of
“soft hematites,’ 20; on the original
state of the iron ore, 32; on the perido-
tite of Presque Isle, 75; on the quartz-
ites, 30, 31; origin of diorite, 20; plasti-
city of iron ore, 21; “quartzite’’ of
Republic Mountain, 34; report on the
iron district, 18-22; sedimentary origin
of iron ore, 20, 21; unconformability of
the Laurentian and Huronian formations,
22.

Brooks (T. B.) and Pumpelly (R), East-
ern sandstone younger than the copper-
bearing rocks, 98, 99; the copper-bear-
ing rocks conformable with the Huronian,
98, 99.

Burt, W. A., reports on iron district, 3-5.

CALCIFEROUS FORMATION, presence of, 103.

Calcite, in spike-like forms, 126.

Calcite veins, igneous origin of, 82, 83, 90.

California, origin of placer gold of, 16, 17.

Calumet and Hecla Mine, character of
copper deposit mined, 129; contact of
sandstone and trap at, 110; copper de-
posits of, 127; microscopic study of peb-
bles from, 118-120; sheet copper at,
126.

Cambrian Age, Huronian the equivalent of,
13; of Keweenaw Point sandstone, 90.
Canada, relations of Laurentian and Huro-

nian in, 72.

Canada, West, copper mines said to be the
most important in America, 106.

Carp River, age of rocks of, 4; quartzite of,
9; sandstone and quartzite of, 22, 23, 60.

Cascade Range, iron ore and quartzite of,
33; ore and jasper of, 32, 33.

Central Mine, a fissure vein, 129; best vein-
stone at, 130; copper deposits of, 127.
Chamberlin, T. C., report of the Wisconsin

Geological Survey, 66.

Champion Mine, intrusive granite at, 57;
ore of, 836; rocks of, 45.

Chazy age of Keweenaw Point sandstone, 95.

Chemist, duty of, 69.

Chlorite, alteration product after augite, 39 ;
alteration product after hornblende, 56;
in quartzite, 59.

Chlorite Schist, formed from a dike, 48;
occurrence of, 20, 21.

Chocolate River, age of rocks of, 4.

Chromic oxide, not in Presque Isle perido-
tite, 61.

Chrysotile, mistaken for asbestus, 66.

Clay, masses in sandstone, 118.

Cleavage, no proof of stratification, 28.

Cleaveland Mine, lamination of schist, 41 ;
relation of ore and schist at, 31.

Cliff, Captain, 131.

Cliff Mine, copper deposits of, 127 ; diabase
Ofeadaule

Conglomerate, formation of, 84, 87, 128;
local nature of, 122, 128; marks old sea-
beach in Huronian, 31; of Keweenaw
Point, lateral moraine formations, 85; of
Presque Isle containing dolomite pebbles,
23; origin of, 122; overlying iron ore,
30; overlying peridotite of Presque Isle,
63; pebbles of melaphyr at base, 115;
thermal water action on, 116; thickness
of, 100; copper deposited in, 83, 127.

Conglomerate mines, mode of formation,
1265 Lie

Connecticut, sandstone of, 79; trap of, 81.

Contact of diorite and schist shown in thin
section, 37. .

Continents, relative ages of American and
European, 9.

Cooper and Patch, Messrs., 182.

Copper, concentration of, 92, 102, 109;
conditions of deposition, 180; deposi-
tion of, 88, 90, 92, 97, 109; deposits
mined for, 128, 129; derived from ores
in older rocks, 109; derived from the
sandstone, $1; description of spikes, 126:
fillmg joints, 126; finely disseminated in
lava, 126; in conglomerate mines, 126;
of volcanic origin, 76 ; originally dissemi-
nated in the traps, 92, 102, 109; origi-
nally from primitive rocks, 81; origi-
nal material brought up by the trap, 81 ;
mode of occurrence of, 86, 124; profita-
ble deposits of, 76, 77; reduction of, 90,
92, 93; replacing melaphyr pebbles, 126 ;
torn from-Azoic rocks by the trap, 94;
united to silver, 79, 51, 105, 106, 109;
use of, by Indians, 92.

Copper-bearing rocks, conformable with the
Huronian, 99 ; easterly dip of, 26; Huro-
nian age of, 108; Keweenawan age of,
108; lava flows, 86-88, 100-103, 105 ; ly-
ing between the Huronian and Potsdam, |
99, 105, 107 ; of calciferous and Potsdam
age, 94; Permian age of, 97; Quebec
age of, 94, 97; Taconian age of, 105;
Triassic age of, 97, 108; unconformable
to the Huronian, 105.

Copper deposits, associated with heavy beds
of trap, 126; not contact forms, 127;
origin of, 89, 91-95, 106, 107, 130, 181.

INDEX.

ili

Copper district, history of geological views in | Diorite, alteration products in, 36, 37; con-

regard to, 76-107.

Copper Falls Mine, ash-bed of, 125; best
veinstone at, 130; character of copper
deposits mined, 129; copper spikes at,
126; Owl Creek, vein of, 129; relation
of traps and sandstone at, 110-113;
proofs of water action at, 125, 126.

Copper Harbor, rocks of, 80.

Copper pyrites, reported abundant in the
iron district, 4.

Copper veins, origin of, 79, 80, 82, 84, 85,
88, 89, 90, 91, 92, 103, 106, 107, 108,
109.

Cordilleras, rhyolites of, 118, 119; volcanic
rocks of, 48.

Credner, H., dikes near Marquette, 36; onthe
geology of the iron district, 17; on the
original condition of the iron ore, 32.

Crosby, W. O., iron ores and jasper a “‘ red
clay ” deep-sea deposit, 25.

Cumming, J. G., glacial action in early
geological ages, 85.

Danpow, S. H., volcanic origin of iron ore,
Ls 17.

Dana, J. D., copper in contact deposits, 127 ;
on the formation of veins and the altera-
tion of rocks, 106, 107; on the origin of
copper deposits, 89, 93, 94; on the origin
of the iron ore, 13; Potsdam and Calcif-
erous age of the sandstone, 93 ; his theory
of the copper deposits not based on facts,
131; Triassic age of the sandstone, 93; on
the union of copper and silver, 105, 106.

Davies, D. C., errors in his work on ‘‘ Met-
alliferous Minerals and Mining,” 25, 26.

Dawson, J. W., his theory of the deposition
of the copper, 92, 93.

Dead River, granite of, 56.

Deer Lake, diorite of, 42, 43.

Detrital deposits of iron ore and jasper, 30,
Bae

Devitrification, in rhyolites and felsites, 33.

Diabase, alteration form of, 46; an altered
basalt, 111; decomposition of, 43 ; erup-
tive in Eastern Massachusetts, 72; micro-
scopic study of that of various localities,
39, 40, 42, 45; not mined on Keweenaw
Point, 111; an old crystalline basalt, 39.

Diallage, in peridotite, 60, 61.

Dike, at Old Washington Mine, variations
in structure of, 48; step form of, at Salis-
bury Mine, 42.

Dikes, near Marquette, microscopic study of,
36, 37; of iron ore and jasper, 30, 31,
32; of magnetite, 36; of schist, 48.

Diller, J. S., on the eruptive origin of felsite,
72.

taining fragments of rocks, 39; erupted
later than the jasper and ore, 51, 52;
eruptive origin of, 17, 26, 46; eruptive
through schist, 41; foliation of eruptive,
47; garnet-bearing, of Republic Mountain,
47; hill of, between Salisbury and Lake
Angeline Mine, 49, 50; interstratified
eruptive, 23; interstratified with schists,
14, 15, 17, 19, 20, 26; intrusive at Light-
house Point and Picnic Island, 23; and
at Republic Mountain, 47; microscopic
examination of, from various localities, 39,
41, 42, 44, 45, 46,47; mineralogically
like the schist, 37; of Marquette district
and the traps of Keweenaw Point the
same, 12; passage into schist, 40 ; relation
to jasper and iron ore, 51, 52; resem-
bling chlorite schist, 42 ; resembling horn-
blende schist, 45 ; sedimentary origin of,
advocated by various writers, 14, 17, 18,
19, 20, 25, 26, 40; younger than the
Huronian, 17; secondary origin of min-
erals in, 46.

Dolomite, of Presque Isle, 2, 3, 10, 23 ; sec-
ondary origin of, in peridotite, 61, 62, 64,
65; stratified, of Rominger, 61; veins of,
64.

Douglass Houghton Fall, geological struc-
ture at, 95, 96, 115, 116.

Drift agencies, in earlier geological times, 85.

Eacte River Mine, H. D. Rogers on,
82, 83.

Eclogite, microscopic study of, from Old
Washington Mine, 48.

Edwards Mine, eruptive character of iron
ore, 35.

Emerson Adit, at Copper Falls Mine, 110,
BENE

Enstatite, alteration of, 61; in peridotite,
60, 61.

Eozoén Canadense, alteration structure re-
sembling, 114,

Epidote, in Republic Mountain granite, 54 ;
secondary origin of, 37, 42, 56, 120.

Epidote veins, relation of, 84.

Favtt, on eastern side of Presque Isle, 64.

Feldspar, alteration of, 39, 42; decomposi-
tion of, 38, 114, 117, 119, 120 ; decompo-
sition products in, 55,56; inclusions in, 36;
inclusions of base in, 87, 44; replaced by
kaolin, 43 ; secondary origin of, 113, 114,
119; stone inclusions in, 42; unstriated
form sometimes due to alteration,55.

Felsite, alteration of, 38; dikes of, 38, 39;
eruptive characters of, 38; fluidal strue-
ture in, 88; intrusive, of Hastern Massa-

iv

chusetts, 72 ; jointing of, 37 ; microscopic
study of, 38, 39, 118-120; its occur-
rence near Marquette not noticed by
Julien, Credner, Brooks, or Rominger, 38 ;
originally identical with modern rhyolites,
38, 39; its occurrence in the iron region,
75; its present difference from rhyolite
due to alteration and depth, 38, 39; its
relation to rhyolite, 118, 119.

Ferrite in pebbles, 113.

Field evidence, value of, 43, 74.

Fluid cavities in quartz, 38, 39, 44, 45; ly-
ing in fissures, 54.

Fluidal structure, 28 ; in felsite, or rhyolite,
38, 118, 119; segregation of minerals
along lines of, 38; in granite parallel to
contact planes, 57.

Foliation not necessarily coincident with
stratification, 25; no proof of stratifica-
tion, 72; of granite a fluidal structure,
57; relation to pressure, 53.

Forest Copper Mine, sandstone at, 100.

Fossils, absence of, explained by thermal
water action, 116.

Foster, J. W., description of the iron region,
15, 16; on age of sandstone, $4; advo-
cates the sedimentary origin of the iron
ores, 6; on the origin of the “ soft hema-
tite,” 16.

Foster, J. W., and Whitney, J. D., azoic
age of district, 26; on the Carp River
sandstone, 60; definition of the Azoic
System, 7, 8, 9; on the formation of
amygdaloid and conglomerate, 86, 87, 88 ;
the results of their geological work sus-
tained, 131; the iron age in geology, 9;
on the metamorphic rocks, 8,9; on the
mode of occurrence of copper, 86 ; objec-
tions to their view of the relations of the
copper-bearing rocks and Eastern sand-
stone in the vicinity of Torch Lake, 122 ;
objection to their view of the structure of
Presque Isle, 62, 63, 76; on the occur-
rence of the iron ore, 7; on the geologi-
cal age of Eastern sandstone, 122; on the
geological structure of Keweenaw Point,
86-89, 96, 97; on sand concretions in shale,
121; on the origin of the copper veins,
88; on the Potsdam age of the sandstone,
87; on the Presque Isle serpentine, 62 ;
on the relations of the trap and sandstone,
111; their Report on the Geology of the
Lake Superior Land District, 9; Silurian
age of the sandstone, 86; their theory of
the origin of the iron ore sustained, 68 ;
the traps a succession of lava flows, 86.

Garnet, altered forms of, 53; columnar
structure of, in schist, 48; dodecahedral

INDEX.

7

crystals in diorite, 47; films of hematite
surrounding, 48; inclusions in, 47; in
diorite, 46; secondary origin of, 47.

Garnetiferous rock, microscopic study of, 48.

Geikie, A., microscopic distinction between
lava flows and intrusive masses, 111; ex-
ceptions thereto in the Lake Superior dis-
trict, 111.

Geological theories of copper district, 76-
109; of iron district, 1-27.

Geology of Lake Superior, bibliography of,
133-157.

Glass, an unstable rock form, 125.

Gneiss, cut by diorite and diabase, 58; mi-
croscopic study of, from various mines,
57, 58; modified in contact with granite,
55; origin of, 57; sedimentary origin of,
26, 58

Granite, contact with a garnetiferous actino-
lite rock, 52, 58 ; cutting diabase, 39; cut-
ting quartzite, 55; cutting schist, 52, 57 ;
eruptive in Huronian, 55; eruptive, of
Eastern Massachusetts, 71, 72; eruptive
origin of, 11, 24; foliation of, 52, 53;
Huronian age of, 24, 25; igneous origin
of, 10; intrusive in schists, 55; Lauren-
tian age of, 14, 15, 19, 24, 25, 52; mi-
croscopic study of, from various localities,
53-57; passage of foliated into non-foli-
ated forms, 57; passage into greenstone,
2; passage into serpentine, 2; of Picnic
Point, 39; Potsdam age of, 91; presence
of, in iron region, 75; red, intrusive in
gray gneiss, 55; of Republic Mountain,
52-55 ; section of intrusive, in gneiss, 57 ;
sedimentary origin of, 14, 25; younger
than Huronian rocks, 53.

Granite Point, relations of granite and sand-
stone, 1, 2

Granite porphyry, microscopic study of,
114, 117.

Graphic granite, alteration structure resem-
bling, 114, 115, 117, 119, 120.

Gray, A. B., report on iron district, 4.

Greenstone, a metamorphosed sedimentary
rock, 80; defined, 128; of Keweenaw
Point, 111.

Greisen, eruptive origin of, 54, 55; a modi-
fication of granite, 55; of Republic Moun-
tain, 44, 53-55.

Groundmass, alteration of, 43.

Hau, JAMEs, maintains the Potsdam age
of the sandstone, 93.

Hancock Mine, ‘‘ash bed” not found at,
112; 1138:

Hancock, Michigan, conglomerates at, 121.

Hematite, a decomposition product, 59; al.
teration product of magnetite, 39 ; crystal.

INDEX. Vv

lizing out of molten magmas, 69; erup-
tive with silica, 68; films of surrounding
magnetite and garnet, 48; forming a dike,
30; secondary origin of, 36, 48.

Hematite, “‘soft,’’ at Jackson Mine, 32;
composition of, 51; conditions of forma-
tion, 50; not bog-iron ore, 51; origin of,
16, 20, 25, 70; origin and characters of,
49-52; probable deposit near Lake Ange-
line Mine, 50.

Hodge, James T., origin of copper and sil-
ver veins, 84.

Home Mine, sandstone and ore at, 32; jas-
per dikes at, 32.

Hornblende, alteration of, 114, 117, 120;
alteration product after augite, 37, 39, 42,
46; altered to chlorite and biotite, 56;
foreign in andesite, 119 ; secondary origin
of, 36, 37; pseudomorphs after fragments
of, 38.

Houghton, D., his views in regard to the
geology of the copper region, 77-81;
geology of iron district, 2,3; geology of
Presque Isle, 2, 3, 62; variability of his
views, 108.

Houghton, Michigan, conglomerate west of,
121

Hubbard, B., on the geological structure of
Keweenaw Point, 82; on the geology of
the iron district, 3, 4; on metamorphism,
5; on the Porcupine Mountains, 83, 84;
traps eruptive in sandstone, $2.

Humboldt, Michigan, granite intrusive in
schist, 57; the rocks and ore of, 35, 36.

Hungarian Falls, sandstone at, 113.

Hunt, T. S., his erroneous observations in
Eastern Massachusetts, 72; his views in
regard to the copper region of Lake Supe-
rior, 93, 94, 99, 105; hematite a proof
of presence of organic matter, 14; his
views in regard to the iron region, 13,
19, 24; indefiniteness of his statements,
109; objects to decomposition theory
of origin of “‘soft hematites,’ 51; not
personally acquainted with the iron dis-
trict, 40; on the Presque Isle serpen-
tine, 62; on the sedimentary origin of

_ greenstones, 25.
Huronian and Laurentian in iron region,

Huronian, conformable with Laurentian, 25;
contact with Laurentian not observed, 24,
25; according to Hunt, equivalent of the
Cambrian, 13; eruptive granite in, 55;
including rocks of two distinct ages, 31 ;
relation to Laurentian, 70, 71; younger
than the Laurentian, 22, 24.

Huronian age, according to Bigsby, distinct
from the Cambrian, 14; of iron district,

13, 14, 15, 17; of Presque Isle serpen-
tine, 62, 64.

Huronian rocks in iron region, 24; uncon-
formable with the Laurentian, 22.

INDIANS, the customs of, 92; use of copper
by, 92.

Tron age of geology, 9.

Iron district, country rocks of, 28, 29;
eruptive rocks of, 46; geological struc-
ture of, 75; historical discussion of, 1-
26; Huronian age of, 13, 14, 15, 17;
jasper and iron ore of, 28-36; not visited
by C. T. Jackson, 6; object of the in-
vestigation of, 27; sea-beaches in, 31;
summary of geological views on, 26, 27.

Iron ore, breaking through schist, 31 ; chem-
ical and metallurgical objections to erup-
tive qrigin of, 68, 69; has the color and
streak of hematite, but is magnetic, 33;
cutting schist, 31; a deep-sea deposit, 25;
its deposition considered due to the pres-
ence of organic matter, 14; dikes of, 30,
32; difficulty in mining, 31; history of
its discovery, 8, 4, 18; eruptive charac-
ters of, 32; eruptive origin of, 27, 67;
form of eruption, 68; form of masses of,
29; Huronian age of, 14, 15, 17; inter-
laminations of, with jasper, 29; igneous
origin of, 7, 9, 10; not interstratified
with schists, 67; intrusive character of,
35; at Ishpeming, 30, 31; junction of,
with chlorite schist, 30; the Laurentian
age of, 13; limits between it and the jas-
per, 33; magnetic in contact with dikes,
43 ; magnetic state induced by secondary
causes, 34; manner of intrusion, 35; in
Marquette district, 6, 7, 14, 15; in Me-
nomonee region, 3, 6, 7 ; in metamorphic
rocks, 7; originally magnetite, 17; mi-
croscopic study of, intrusive in quartzite,
33; at Negaunee, 31, 32 ; in octahedrons,
33; origin of, 12, 13; its origin a matter
of economic importance, 29 ; the original
state of, 32, 34; plasticity of, 21, 67;
according to Rivot, of Potsdam age, 91;
proof of its intrusive character, 67; its
relations to the country rock, 30-36; re-
lation to schist, 31; secondary deposition
of, 33 ; sedimentary origin of, maintained
by various geologists, 6, 138, 14, 15, 17, 18,
20, 21, 22, 24, 25, 27; not in veins, 19,
29; wedge-shaped masses of, 31, 33.

Tron, oxides of, their action in reduction of
the copper, 90, 92, 93, 97; precipitation
of copper by, 130.

Iron, the protoxide of, an agent in the depo-
sition of copper in veins, 90.

Iron, titaniferous, decomposition of, 48.

vi

Irving, R. D., on the copper-bearing rocks,
104; on Keweenawan granite, 71; rela-
tions of trap and sandstone, 104; unity
of foliation and stratification, 25.

Ishpeming, Michigan, contact of diorite and
schist, 41; gneiss south of, 55; iron ore
of, 30, 31; quartzite of, 59; red granite
south of, 56; serpentine of, 65, 66;
“soft hematite’ mines of, 49, 50.

Isle Royale, geological structure of, 86, 87.

Isle Royale Lode, thermal water action on,
124.

Jackson, C.'T., the copper mines of Lake
Superior probably not of permanent value,
81; copper and silver, of igneous origin,
81, 85, 86; copper veins valuable only in
the amygdaloid, 86; on the deposition of
the copper, 90; on drift agencies in early
geological times, 85 ; on the formation of
the zeolites, 91; on the geology of Ke-
weenaw Point, 80-82; the igneous origin
of calcite veins, 90; “ New Red” age of
sandstone of Lake Superior, 80, 85; the
New Red sandstone of Upper Silurian age,
89; origin of amygdaloid sandstone and
conglomerate, 84, 85; on the origin of
the ‘“‘ash-bed,”’ 91; various opinions in
regard to the age of the sandstone, 84,
89, 93.

Jackson Mine, diabase of, 48; intrusion of
iron ore in schist, 31; jasper of, 33;
“soft hemetite ” at, 32, 51.

Jasper, associations of, 29 ; brecciated struc-
ture of, 32; not coincident with lamina-
tion of schist, 31; cutting schist, 33;
a deep-sea deposit, OB: dikes of, 30, 32.
eruptive nature of, 35, 67; fluidal strue-
ture in, 33; fragments in quartzite, 59;
interlaminations with iron ore, 29 ; lim-
its between it and the ore, 33; micro-
scopic study of, 33, 34, 44; at Negaunee,
31, 32; relation to diorite, 51, 52; up-
lift of, 51, 52.

Jaspilite, proposal and definition of the term,
75, 76.

Joint planes, no proof of stratification, 28 ;
taken for bedding planes, 117.

Julien, A. A., dikes near Marquette, 36;
doubts the presence of diabase in iron re-
gion, 45.

Junction line between diorite and schist, 40,
Al.

Kao.tn, pseudomorphs after feldspar, 43 ; at
Salisbury and McComber Mines, 50, 51.

Keweenaw Bay, dip of sandstone, 88.

Keweenaw Point, copper deposits mined on,
128, 129; geological structure of, 76, 77,

INDEX.

78, 79, 80, 81, 82, 85, 86, 87, 96, 97,
116, 127.

Keweenawan Series, numerous geological
ages in, 118.

Keweenawan System, no basis for, 72,

Keweenian Group, name first used by Hunt,
99.

Keystone Mine, magnetite dike at, 36.

Kimball, J. P., on origin of iron ore, 16; on
the structure of the iron district, 15, 16.

Koch, Fr. C. L., on metamorphic rocks, 11;
description of iron region, 11.

Lake ANGELINE Minz, diorite of, 42.

Lake Gogebic, copper-bearing rocks near,
98.

Lake Huron, azoic rocks of, confounded by
Logan with Keweenaw Point traps, 90.
Lake Superior Mine, greenish quartz rock of,
49; iron ore and jasper at, 30 ; microscopic
study of the jasper of, 33; oven-shaped

structure in, 51.

Lake Superior Region, eet of observa-
tion in, 27, 28, 73; rocks of mixed
er uptive and sedimentary origin, 27.

Lamination, of jasper, 30 ; not proof of sedi-
mentation, 28; of Picnic Point eruptive
granite, 55; of the schists, 67, 68; of
schist between dikes, 41; of schist cut by
iron ore, 31.

Laumontite, red feldspar mistaken for, 121.

Laurentian, conformable with Huronian, 25 ;
contact with Huronian not seen, 24, 25 ;
doubtful basis of, 72; a name first applied
to post-Tertiary deposits by Desor, 7;
younger than the Huronian, 22, 24.

Laurentian age, of the granite, 14, 15, 17;
of the iron ore, 13.

Laurentian granite, eruptive in Huronian,
70.

Laurentian rocks, in iron district, 24; un-
conformable with Huronian, 22, 24;
younger than the Huronian, 22.

Lava, scoriaceous form of, preserved, 113.

Lava flow at Presque Isle, 9, 10.

Tava flows, mining of old, 124.

Lavas, geological age of, determined litho-
logically, 72.

Lesley, J. P., errors made in quoting the
“Metallic Wealth of United States,’ 12,
13; opposes the igneous origin of any
iron ore, 12.

*TLeucoxene,” alteration product after iron
ores, 37.

Lherzolite of Presque Isle, 60-65.

Lighthouse Point, diorite of, 23.

Literature of the geology of Lake Superior,
132-157.

INDEX.

Lithologists who have studied Lake Supe-
rior rocks, 74.

Lithology, defects of its methods, 74; of
iron district, 2, 7.

Limestone, associated with serpentine, 66.

Limonite, botryoidal ore of Pendill Mine,
bl.

Lingule in sandstone, 26.

Locke, J., on Presque Isle serpentine, 62;
metamorphic origin of Keweenaw Point
rocks, 79, 80; on quartz veins, 6.

Logan, W. E., on the Calciferous and Pots-
dam age of the copper-bearing rocks, 94 ;
Cambrian age of sandstone, 90; confusion
of Azoic with copper-bearing rocks, 91;
eastern sandstone of Chazy age, 94; er-
roneous statement of Houghton’s views,
83; sandstone older than Potsdam, 83.

McComper Ming, minerals of, 51; geologi-
cal structure of, 51.

Macfarlane, T., maintains the Permian age
of the Lake Superior sandstone, 94; op-
poses Selwyn’s views, 106.

Magnetite, octahedrons of, 30, 33; caught
up by a dike, 45; dikes of, 36; altered to
hematite, 39; network form of, 66;
produced in the alteration of olivine, 61 ;
surrounded by hematite films, 48; rec-
tangular network of, 61; its relations to
martite, 34, 35.

Maine, trap of, 81.

Malachite on Keweenaw Point, 76.

Manganite at McComber Mine, 51.

Marcou, J., on the igneous origin of copper,
90; maintains the New Red age of the
Lake Superior sandstone, 90; copper
veins dike formations, 90.

Margarophyllites in garnet, 53.

Marquette, dikes near, 36, 37, 38; sand-
stone of, 60.

Marquette region, Laurentian and Huro-
nian in, 22; stratigraphy of, 19 ; iron ore
in, 6, 7; sediraentary rocks of, 74, 75.

Masonite microscopically like ottrelite, 45.

Massachusetts, Hastern, geological methods
followed in, 72.

Martite, relations to magnetite, 34, 35;
octahedrons of, 33.

Marvine, A. R., on the formation of the
copper-bearing veins, 103 ; on the con-
centration of the copper in the veins, 102 ;
his geological observations sustained, 131;
relation of trap and sandstone, 111; on
conglomerate beds, 100 ; origin of amyg-
daloid structure, 100, 101; supports the
views of Foster and Whitney, 103; his
report on copper-bearing rocks, 100-108 ;
on metamorphism, 101, 102.

Vil

Melaphyr, an altered basalt, 111; dikes of,
at Coppper Falls Mine, 111, 112; fre-
quently mined on Keweenaw Point, 111 ;
glassy material formerly in, 125, 126;
impregnated with copper, 130; locally lim-
ited, 128; microscopic examination of,
from junction with jasper, 44; micro-
scopic study of, from Washington Mine,
43; pebbles of, replaced by copper, 126;
at Portage Lake, 94; relation of first lava
flow to underlying sandstone, 114, 115;
richer in copper near a vein, 125.

Menominee district, granite of, 24, 71;
iron ore in, 3, 6, 7; Laurentian in, 22;
Huronian rocks of, 22.

Metamorphic rocks, origin of, 3, 5, 6, 7, 8,
9, 10, 11, 14, 15.

Metamorphism, the agent of, 35; of crystal-
line rocks, 8, 9, 14, 15; exciting cause
of, 27; of traps and sandstones, 101, 102;
of schists, 26.

Mica, in argillaceous sandstone, 116; sec-
ondary origin of, 38; greenish, in quartz
rock, 49.

Michigan geologists, defective methods of,
118.

Microcline in granite, 57.

Microlites, of apatite, 37; in feldspar and
quartz, 56; in quartz, 38, 44.

Microscope, use of, in the study of rocks, 73,
74,

Microscopie analysis, insufficient to prove
origin of rock, 43.

Microscopic distinction between lava flows
and intrusive rocks, 111.

Microscopic examination of Lake Angeline
diorite, 42.

Mineral Point Railroad, microscopic study
of pebbles from, 120.

Mining, destructive of geological evidence,
68.

Montalban series in the iron region, 24.

Mud-flows in shale, 121.

Miller, A., copper reduced by organic mat-
ter and oxide of iron. 92.

Murray, A., Huronian age of iron district,

Muscovite, cutting biotite, 56; folia of, in
feldspar, 57; in feldspar, 56.

NEGAUNEE, Michigan, eruptive diorite at,
41 ; “soft hematite’ mines of, 51.

Nevadite, 72.

New England, methods of observation in, 73.

New Jersey, sandstone of, contemporaneous
with that of Keweenaw Point, 79.

New Red sandstone of Upper Silurian age,
89, 90.

New York Mine, quartzite of, 59.

Vill

Newberry, J. S., on the origin of iron ores,
23, 24.

Norian, in Kastern Massachusetts, 72 ; erup-
tive basaltic (gabbro) forms, 72.

North Island, diabase and diorite of, 39.

Nova Scotia, trap of, 81.

OLIVINE, action of magma on, 40; altera-
tion of, 42, 61; in diabase, 40, 42, 43,
45; foreign in basalt, 119; greenish
pseudomorphs of, 61; in peridotite, 60,
61; presence of, in iron region, 75 ; pseu-
domorphs after, 36.

Ontonagon district, structure of, 104, 105.

Ontonagon River, origin of copper of, 76 ;
sandstone on west fork of, 100.

Organic matter, precipitation of the copper
by, 92, 95, 109, 180.

Orthoclase, secondary origin of, 37.

Osceola Mine, microscopic study of pebbles
from, 119.

Ottrelite, microscopic characters of, 45.

Ottrelite schist, formation of, 36, 75; mi-
croscopic study of, 45; production of, 45.

Ovifak, Disko, iron-bearing basalt of, 18.

Owen, D. D., on the age of the sandstone,
84, 90.

Owl Creek Vein, mass copper of, 130.

Patmozoic AGE of rocks of Hastern Massa-
chusetts, 72.

Palmer Mine, eruptive character of jasper
at, 32.

Peck, Samuel, credited with first discovery
of iron ore in the iron district, 4.

Pendill Mine, geological structure of, 51.

Penokee Gap, unconformability of Huronian
and Laurentian at, 25; Huronian and
Laurentian at, 24.

Peridotite, alteration of, 61-66; contact
with sandstone, 2, 3; eruptive origin of,
64; place of, in lithological nomenclature,
65; of Ishpeming, 65, 66; of Presque
Isle, 2, 3, 42, 60-65, 75; microscopic
study of, from Presque Isle, 60-62; re-
lations of, to sandstone at Presque Isle,
10.

Permian age of copper-bearing rocks, 97.

Petherick Mine, ‘‘ash-bed”’ at, 112.

Phenix (old) Mine, “‘ash-bed” at, 112;
diabase of, 111; a fissure vein, 129.

Picnic Island, diorites of, 23, 39.

Picnic Point, granite of, 39, 55, 56 ; micro-
scopic study of rocks of, 39, 40; rocks of,
29, 40, 74.

Pittsburg and Lake Superior Mine, micro-
scopic section of iron ore intrusive in
quartzite, 32.

Plagioclase, cutting augite, 42.

INDEX.

Plasticity of iron ore, jasper, and chlorite
schist, 67.

Porcupine Mountains, geological structure
of, 76, 77, 84.

Porodite, use of the term, 60.

Porphyry, formation of, 84.

Portage Lake, copper deposits of, 94; dip
of sandstone at, 82; melaphyr at, 94; old
lava flows mined at, 124; trap at, 86.

Portage Lake district, copper deposits mined
in, 128, 129; no fissure veins in, 124;
“slates” of, 121.

Porter’s Island, 80.

Potsdam age, of all Lake Superior rocks,
12; of iron region, 26; of Keweenaw
Point sandstone, 82, 84, 87, 90, 103,
104.

Potsdam sandstone, source of materials in,
60; microscopic study of, 60,

Prehnite, igneous origin of, 80.

Presque Isle, dolomite of, 3; forming an
island in the Potsdam Sea, 23; geologi-
cal structure of, 2, 3, 9, 10, 23, 60; peri-
dotite of, 75 ; peridotite and serpentine of,
60-65.

Pseudo-amygdaloidal structure, origin of,
100, 101, 128, 129, 130.

Pseudomorphs after olivine, 36.

Pseudo-stratification, 28.

Pumpelly, R., on alteration of basaltic rocks,
105; on black inclusions in garnet, 47 ;
copper-bearing traps, diabases, and mela-
phyrs, 105 ; on the deposition of the cop-
per by protoxide of iron, 97 ; derivation of
copper from sandstone, 126, 127; geo- .
logical report on the copper district, 100;
pre-Potsdam age of copper-bearing rocks,
99; ‘‘specular slate ore,” pseudomorph
after chlorite schist, 20.

Pyrite, in felsite, 38.

Quartz, bearing fluid and vapor cavities,
38, 39, 114, 117, 119; containing double
pyramidal inclusions, 120; crystals in
sandstone with unworn facets, 117; de-
vitrification form of, 38; fluid inclu-
sions in, 43, 44, 45, 55; foreign, in
rhyolite and felsite, 119; grains formed
by fissuring of a silicious mass, 53, 54;
heat action on, 33; inclusions in, 44,
54-59; microlites in, 38; prismatic
structure of surrounding ring, 48; sec-
ondary origin of, 33, 36, 37, 38, 39, 47,
113, 114, 117, 119, 120; stone cavities
in, 38, 119, 120; structure of, in felsite,
118, 119; with unworn facets in sand-
stone, 60; water-deposited, 63.

Quartz Porphyry, rhyolitic character of, 119.
See Felsite.

INDEX.

Quartz Rock, intrusive character of, 49 ;
microscopic study of, from Lake Superior
Mine, 49.

Quartz, Veinstone, microscopic examination
of, 51 ; fluid cavities with moving bubbles,
51.

Quartzite, of Brooks, at Republic Mountain,
34, 35; of Carp River, 9; defined by
Zirkel, Lasaulx, and Hawes, 58 ; eruptive
form of, 34, 85; eruptive origin of, 11;
formed of detritus of jasper and iron ore,
59; granite intrusive in, 55; Huronian
age of, 22; an indurated sandstone, 58,
59; microscopic study of iron ore intru-
sive in, 88; microscopic study of, from
Ishpeming, 59; microscopic study of,
from Jackson Mine, 59, 60; microscopic
study of, from New York Mine, 59; mi-
croscopie study of Brooks’s, from Repub-
lic Mountain, 54; of the New York Mine,
30; origin of, 9; overlying ore, and con-
taining fragments of it, 32; ripple-marks
in, 9, 25.

Quebee Group, Lake Superior sandstone be-
longing to, 93.

Quincy Mine, working on an old lava flow,
125 ; character of ore deposit, 129.

RatnpDnopP impressions in shale, 121.

Republic Mountain, diorite of, 45, 47, 49 ;
granite of, 52-55; greisen of, 44, 55;
magnetic silicious schist of, 47 ; ore and
rocks of, 84; “quartzite ” of, 34, 35.

Rhyolites, felsites originally identical with,
38, 39, 118, 119.

Rhodochrosite, at McComber Mine, 51.

Ripple-marks, 9, 25, 79, 121.

Rivot, L. E., his ideas in regard to Lake
Superior geology, 11, 12, 91.

Rominger, C., on the conformability of
Laurentian and Huronian, 25; dikes near
Marquette, 36; on the geological age of
the Kastern sandstone, 122; on occurrence
of “soft hematite,” 50 ; on the Ontonagon
district, 104, 105; on Presque Isle serpen-
tine,62 ; on therelation of the copper-bear-
ing rocks to the sandstone, 103, 104; on
the relation of the sandstone and quartzite,
22, 23.

Rocks, all subject to alteration, 28, 34;
alteration accompanied by reerystallization,
34; alteration of, a passage from an un-
stable condition towards a more stable one,
125; association of, 28; banding of, no
proof of stratification, 72; basie eruptive,
of iron region, varieties of, 46; causes
of induration of, 125; determination of
age of, by lithological characters, 94; ge-
ological age, told microscopically, 73, 74 ;

ix

their history, 28; intrusive garnet-bear-
ing actinolite probably altered andesites
and basalts, 49 ; intrusive, of iron district,
70; the microscopic study of, 73, 74;
mode of determining origin of, 68 ; names
given to local modifications of, 55 ; origi-
nal characters of, lost, 834; passage of dif-
ferent forms into one another, 40, 69;
requirements for study of altered forms,
74; resemblance does not prove identity,
27, 28; sedimentary origin of eruptive,
11, 12; superficial study of, 69.

Rocks, crystalline, origin of, 14, 15; passage
of different forms into one another, 4, 5,
14, 27, 37, 69; pre-Paleeozoic age of, 5.

Rocks, eruptive, crystallization of, 72; of
iron district, originally basalts, 46.

Rock structures, origin of, 28.

Rogers, H. D., copper-bearing rocks semi-
fused materials, 83; on the copper de-
posits, 82, 83; crystalline rocks of Choc-
olate and Carp Rivers of Primal or Pots-
dam age, 4; New Red age of Keweenaw
Point sandstone, 83.

Rogers, W. B., Potsdam age of sandstone,
93.

Rottermund, Count de, report of, 91, 92.

Ruggles, D., on the origin of copper veins,

80.

St. Mary’s River, sandstone of, 77.

Salisbury Mine, geological structure of, 50 ;
“soft hematite ” of, 49, 50.

Salt cubes, in granite, 25; in quartz, char-
acteristic of Huronian granite, 56.

Sand, concretions of, in shale, 121.

Sandstone, action of trap on, 82; composed
of trachytic and rhyolitic material, 114,
115, 117, 119, 120; contact with quartz-
ite, 22, 23; containing trappean detritus,
110, 111; curved stratification of, 63;
formed of granite detritus, 60; formed
from voleanie débris, 117, 118; impreg-
nated with iron ore, 32; microscopic
study of indurated, 114, 115; origin of,
122, 128; precipitation of copper in, by
organic matter, 94, 95, 109; pebbles of
quartzite in, 113; its relation to Presque
Isle peridotite, 63, 64; its relation to the
traps, 109-113, 118; ripple-marks in,
79; stalactites of, 118; thermal water
action on, 63, 117; Torch Lake quarry
of, 117; on western side of copper-bear-
ing rocks, 120, 121, 122; microscopic
study of feldspathic, 60.

Sandstone, Eastern, dip of, 118-119; geo-
logical age of, 122; relation to traps,
108; younger than the copper-bearing
rocks, 98, 99.

x

Sandstone of Keweenaw Point, age of, 108;
belongs to the Quebec group, 93, 97;
Calciterous age of, 93, 94; Cambrian age
of, 90; cause of absence of fossils in, 85;
of Chazy age, 94; of ““New Red” age,
79, 80, 81, 89, 90, 93, 97; of “Old Red”
age, 77, 80; origin of, 82; of Permian
age, 94; of Potsdam age, 82, 91, 93,
103, 104, 107; pre-Potsdam age of, 83.

Sandstone, Western, of same age as the
traps, 121, 122.

Schist, composed of basaltic detritus, 37;
contortion of stratification planes of, 67 ;
garnet-bearing, of Republic Mountain, 47 ;
granite intrusive in, 55; Huronian age
of, 14, 24, 52; lamination cut by iron
ore, 31; microscopic study of, 36, 37, 47,
48, 53, 58; mineralogically like diorite,
37; passage of magnesian, into dioritic
rocks, 20 ; its relation to the iron ore, 31;
sedimentary origin of, 26, 48; uplifted
by granite, 53; welded to granite, 53.

Schooleraft, H. R., falsification of original
documents in his “ Summary Narrative”
of 1854, 10, 11; his views in regard
to the copper region of Lake Superior,
76.

Schoolhouse Mine, conglomerate at, 30;
dike of jasper at, 30.

Sedimentary origin of eruptive and crystal-
line rocks, 11, 12, 14, 15; of the iron
ore, 6, 14, 15. ‘

Sedimentary rocks, rapid deposition of, 118.

Selwyn, A. R. C., on the Huronian age of
the copper-bearing rocks, 106.

Serpentine, an alteration form of peridotite,
61, 66; an alteration product of olivine,
42; on the formation of, 75; microscopic
study of, from Ishpeming, 65, 66; net-
work structure of, 61; origin of, 64, 65;
of Presque Isle, 60-65.

Shale, raindrop impressions, ripple-marks,
and mud-flows in, 121.

Shelden and Columbian Mine, character of
copper deposit at, 129.

Silica, eruptive with hematite, 33.

Silver, its union with copper, 79, 81, 105,
106, 109.

Spherulitic structure, produced by alteration,
118, 119, 120.

Stone cavities in feldspar, 42 ; formed from
devitrified base, 42; in quartz, 56.

Sweet, E. T., unconformability of Lauren-
tian and Huronian, 24.

TACHYLITE, altered form of, 44.

Talc, in ottrelite schist, 45.

Teal Lake, diorite of, 41; lamination of
schist at, 41; quartzite of, 9.

INDEX.

Thermal waters, action of, 49, 50, 51, 116,
117, 123, 124, 125, 126.

Titanite, in granite, 56.

Torch Lake, sandstone quarry at, 117.

Tourmaline, in eclogite, 48; crystals in
diorite, 45; in ottrelite schist, 45; pres-
ence of, in iron region, 75; in radiating
groups of crystals in quartz, 45.

Trachyte, microscopic study of, 118, 114,
117, 120; pebbles of, 113.

Trap, action on the sandstone, 86-88, 101-
103; age relative to Hastern sandstone,
108 ; amygdaloidal and scoriaceous on
upper surface, 110; characters and rela-
tions of, 104, 109-113, 118, 128; denu-
dation of, before sandstone was deposited,
113; evidence that they are lava flows,
127, 128; pseudo-stratification of, 86 ;
sends tongues into the “ash-bed,”’ 113;
tongues of, extending into sandstone,
110; metamorphic sedimentary origin
of, 91.

Triassic age of copper-bearing rocks, 97.

Trichites in quartz, 59, 120.

UNCONFORMABILITY, based on foliation and
lamination, 71; uot proof of distinct age,
31.

VAPOR CAVITIES in quartz, 39.

Veins, filling of, 124, 129: of iron ore, 29;
variations of, 129; width of, 124.

Veins fissure, formation of, on Keweenaw
Point, 123.

Vein material, derived from the traps, 123.

Veinstones, character of best forms, 130.

Viridite, replacing augite, 42; replacing
base, 37. :

Voleanic action, earlier than Tertiary times,
119; gradual increase and diminution of,
122.

Voleanic origin of the copper-bearing rocks,
where shown, 131; of copper veins, 80.

Warwick, Rhode Island, masonite of, 45.

Washington Mine, rocks of, 43, 44, 45.

Washington Mine (new), dikes of ore at, 36.

Washington Mine (old), relations of iron
ore and actinolite schist, 35.

Water, action of percolating, 123, 129.

Whitney, J. D., alternations in formation of
zeolites, 95; chemical analysis of Presque
Isle serpentine, 14, 62, 65; “ Metallic
Wealth of the United States,” 90; igneous
origin of iron ore, 7, 10; on the iron dis-
trict, 7.

Whittlesey, C., copper-bearing rock contin-
uous with, but below, the sandstone, 94;
eruptive origin of granite, 24; Huronian

INDEX. xl

age of schists, 24; pre-Potsdam age of | Wright, C. E., metamorphic origin of gran-

sandstone, 90.

Wichmann, A., diorite of, 37; on eclogite,
48; on feldspar crystals, 44; limits be-
tween jasper and ore, 33; on olivine-dia-
base, 70; on the Presque Isle serpentine,
62; report on the rocks of the iron dis-
trict, 66; use of term quartzite, 58, 59;
originally formed products in feldspar, 55,
56

Winchell, A., on the iron district, 17, 18;
sedimentary origin of iron ores and dio-
rites, 17, 18.

Wisconsin geologists, defective methods of,
107, 118; on the Keweenawan series, 107.

ite, 25; origin of “‘soft hematite,’ 25;
relation of Laurentian and Huronian, 25 ;
salt cubes in quartz, 25, 56 ; sedimentary
origin of iron ore, 25; unity of foliation
and stratification, 25.

ZEOLITES, formation of, 91, 93.
Zircon crystals in quartz and feldspar, 56 ;

in granite, 57; microlites of, in quartz,
57, 59.

Zirkel, Ferdinand, “inserted substance” a

base, 37; originally formed products in
feldspar, 55, 56.

i

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