abs

in
a
ye
ie) Wi

Sa fede deed
ee eM en ie
es Keiaca ned

as Vr

f
fi)
ay
i

I
tty

hah
x i ans Ny ete
ea nt ny

iy
¥

5)

RK UN
Fey

on ny ih
)

aris

" AS Rit
j Pie ( HEU tte i
:
Dh DORN ANUS ae Paualieian
1 SCH A, hs A
Une

‘y
o
anit "4 ‘ 4 i ie i it Le ‘ o i ‘s
a“ * red Bh i M4 i ii i ie i } vy
ORE Ade SACD AN Nay RRR i} i near LM

With

LPN) TA ALS
Vedran iy

Noane
DRE he
eer rg

NOURNAL OF GEOLOGY

JULY-AUGOST, 1809

MoE VW ANAL CITE ROCK FROM. LAKE SUPERTOR

Amonc other regions on the northern shores of Lake Superior
examined last summer by the writer for the Ontario Bureau of
Mines the vicinity of Heron Bay, where the Canadian Pacific
Railway first touches the lake when coming from the east, proved
very interesting, a thick series of schist conglomerates with peb-
bles and bowlders mainly of felsite and quartz-porphyry occur-
ring there, mapped by Dr. Bell of the Canadian Geological
Survey as Huronian. Along the rocky shore of the bay, and
also in cuttings on the railway west of the station, good expo-
sures of these rocks are seen, sometimes so rolled out that the
forms of the pebbles are almost, or completely, lost. Crossing
the schist conglomerates are numerous dikes, which unfortunately
were not carefully studied owing to lack of time, though hand
specimens of the more typical dike rocks were taken. In the
field the dikes were considered to consist of diabase, diabase-
porphyrite, and felsite, all common rocks in the western
Keewatin.

Microscopical study of the specimens obtained showed that
the diabase and porphyrite present no unusual features, and that
one of the felsitic-looking rocks is quartzless porphyry of a kind
common in western Ontario. Another rock taken for felsite,

dark red and slightly spotted with green, turns out, however, to
Vol. VII, No. 5. 431

432 A. P. COLEMAN

be of a new type, and will be described here because of its inter-
esting mineralogical and chemical composition.

The specimens were obtained near mile 804 in a cutting on
the railway, one being chosen to represent the freshest material
seen, another weathered, and presenting a mottling of red and
dark green, almost suggesting a variety of amygdaloid. Sections
of the latter specimen are so completely weathered that little of
its original composition can be determined ; but sections of the
fresh specimen show that the greenish spots consist almost
wholly of feldspars having a confused radiating arrangement
giving spherical forms; while the red part is composed of an
isotropic base like a clear glass penetrated by radiating bundles
of green prisms and also larger bundles of feldspar laths, brown
with particles of iron oxide. A little calcite scattered through
the section proves that the rock is no longer fresh.

The vague spheres of feldspar often have an imperfect black
cross in polarized light, and consist mainly of orthoclase, some-
what turbid and specked with brown iron oxide, with a little of
the green mineral intermixed. The rest of the rock contains
some orthoclase also, but consists chiefly of the isotropic substance
inclosing the radiating bundles of prisms referred to before.
The green prisms are fresh in color and appearance, and are
usually distinctly dichroic, dark green when the prism is parallel
to the chief section of the nicol, yellowish-green at right angles
to this position. Extinction is nearly parallel, but angles of 4% °
occur. The larger crystals sometimes have sharpened ends,
The mineral was at first taken for hornblende, but is no doubt
aegyrite. :

The other mineral forming radiating bundles is probably
plagioclase, clearer parts showing twin lamellae, whose angle of
extinction, however, could not be sharply determined owing to
the small size of the lamellae. Many of these plagioclase strips
are reddish-brown and almost opaque, with particles of brown
iron ore.

The only other primary mineral observed, except a few
needles of apatite, is the isotropic base in which the crystals

NEW ANALCITE ROCK FROM LAKE SUPERIOR 433

just referred to are embedded. It is clear and transparent, with
some dusty spots, however, and has not the look of ordinary
volcanic glass. With high powers a delicate, but distinct, sys-
tem of cubic cleavage lines can be seen, proving that the mineral
is isometric and therefore probably analcite, though no crystal
forms were observed.

An attempt was made to isolate the glassy mineral with a
heavy solution, analcite being lighter than any other rock form-
ing mineral belonging to eruptives, and it was found that 17
per cent. of the powder floated when gypsum was used as an
index (spec. grav. 2.32); but when examined with the micro-
scope the powder was found to contain doubly refracting por-
tions embedded in the isotropic ones, and some isotropic portions
were noticed associated with the heavier minerals. Some of the
rock was then treated with strong hydrochloric acid, when
partial gelatinization took place, and it seemed wise to reduce
the whole to dryness to render the silica insoluble. It was
found that 27.76 per cent. of the whole weight went into solution,
omitting, of course, the silica of the mineral which gelatinized
when treated with acid. A second portion treated in the same
way asa check gave 30.35 per cent. of soluble matter. Probably
the first portion taken contained more of the sphaerulitic parts
than the second. An analysis of the soluble part made by myself
gave the following results:

Al,O3 - - - . 10.90
Fe,Q,; - - . Bale
CaO - - - - 108
MgO - - - trace
Na,O_ - - - - 6.60
K,0O - - - - not det.
H,0O (at 100°) - - 69
H,O (at red heat) -- 4.85
CO, - - - - 93

28.13

We may assume that the only minerals in the rock which
would be appreciably dissolved by HCl are analcite, limonite,

434 A. P. COLEMAN

and calcite. If we subtract the lime and carbonic acid, as form-
ing calcite, and the ferric oxide with a proportionate amount of
water (.45 per cent.), as forming limonite, we have left the

following:
Al,O3 - - - - 10.90 pO Sir
Na,O - - = - 6.60 .106 =1
H,O (at red heat) = a) Alghi) IDNA — (2426

Reducing to molecular ratios, alumina and soda are equal,
and water stands at 2%, proportions that correspond to those of
analcite, except for a little too much water.

If the alumina in analcite equals 10.90 per cent. the corre-
sponding amount of silica, four molecules, is 25.49 per cent.,
and the whole percentage of analcite in the rock is almost
exactly 47, nearly one half. In the second part treated
with acid, when 30.35 per cent. proved soluble, the amount of
analcite must be more than half the whole weight of rock taken
If we subtract the percentages of substances found in the first
portion of rock dissolved in hydrochloric acid from the results of
the complete analysis, and also the proper amount of silica to
form analcite with the alumina, soda, and combined water, we
shall have left the materials forming the insoluble ingredients of
the rock. j

The complete analysis given below was made by Mr. H. W.
Charlton, his results being put in column I. In column II an
analysis by Dr. Mann of cancrinite-aegyrite-syenite from Siksj6-
Berg in Dalarne’ is given because of its rather close resemblance
to No. 1; and in column III an analysis of analcite-basalt from
the Basin, Colorado, by W. F. Hillebrand.?

A little more than 46 per cent. of the rock remains unac-
counted for by the partial analysis ; and if we suppose the whole
of the potash to belong to orthoclase and the unused portion of
iron oxide (1.40 per cent.) to belong to aegyrite, we have left

* Neues Jahrbuch fiir Mineralogie, 1884, II, p. 193; as quoted by ZIRKEL, Lehr-
buch der Petrographie, Band II, p. 410.

2 WHITMAN Cross, an Analcite-Basalt from Colorado, Jour. GEOL., Vol. V, No.
7, 1897, p. 689.

NEWAANALCITE ROCK FROM LAKE, SUPERIOR 435

I II III

SHG) Dees 52.73 51.04 45.59
AOS - - 29 1.32
ZrOg - > 03
INO - - 20.05 20.47 12.98
Fe,Og, - 2 : 3-43 1.89 4.97
FeO - -99 2.19 4.70
MnO =- - 14
CaO - - 3.35 2.62 11.09
SrO i073
BaO - sate 7
MgO - - - - - ay. 907 8.36
IONE - - - - 4.77 3°52 1.04
Na,O - - - - - 7.94 11.62 4.53
H.O (at 100°) - . - .69 ? 8 a
H,O (atredheat)- - - 4.85 \ 5-85 3.40
P.O; - - - - trace 27 QI
Cl - 05
COF- - - -93 62

100.01 101.35 99.87
Spec. Grav. - - - - 2.466 2.46

silica, alumina, lime, and soda nearly in the proportions required
for labradorite (Ab. 2: An. 3), though the lime and soda are
about one third in excess of the amount required, the excess
being less than I per cent., however.

Summing up the results arrived at, the minerals forming the
rock have the following percentages :

Analcite - - - - - - - 47.00
Orthoclase - - - - - - 28.24
Labradorite - - - - - - 13.00
Aegyrite - - - - - - 4.04
Limonite - - - - - = | Aa5o
Calcite - - - - - . 1.96

97-83

In this computation moisture removed at 100°, unimportant
percentages of magnesium and barium oxides, etc., amounting
in all to 1.47 per cent., have been neglected.

The composition of the rock as shown by the analysis differs
widely from that of analcite-basalt, as may be seen from a com-

436 A. P. COLEMAN

parison of columns I and III, the latter being more basic, con-
taining less alumina and alkalies, and far more lime and magnesia.
It corresponds fairly well, however, to the composition of nephe-
line syenite, the only important difference being in the amount
of water. The syenite from Dalarne, whose analysis is given in
column II of the table, having its nepheline weathered to a
hydrous mineral, resembles this rock closely in composition, the
only important difference being the larger percentage of soda.
In their unusually low specific gravity, 2.46, also the two rocks
are alike.

One naturally expects to find the dike containing the rock
above described in connection with some boss of nepheline
syenite; but the slight examination hitherto made of the region
by Dr. Bell and myself has not disclosed any area of that rock.

If the analcite rock of Heron Bay had a granular texture, it
would appropriately be named analcite-syenite, after the analogy
of nepheline-syenite; but its peculiar structure of spherical
groups of orthoclase embedded in a ground of analcite contain-
ing radiating bundles of plagioclase laths and aegyrite needles
sets it quite apart from the syenites. It will probably be wise
to give it a separate name, and Heronite, from the name of the
locality where it occurs, is suggested as suitable.

Heronite may be defined as a dike rock consisting essentially
of analcite, orthoclase, plagioclase, and aegyrite, the analcite
having the character of a base in which the other minerals form
radiating groups of crystals. The analcite clearly represents
the magma left after the crystallization of the embedded min-
erals; and it is evident that it can be formed only froma magma
highly charged with water, and therefore under pressure. It is
equally evident that Heronite, like other analcite rocks, cannot
be an effusive, since under those circumstances the water would
escape ;* and that its nearest relatives among effusive as well as
plutonic rocksare to be found in the group containing nepheline.

A. P. COLEMAN.

*Cf. Pirsson, Analcite Group of Igneous Rocks, Jour. GEOL., Vol. IV, No. 6,
pp. 686-688.

CORUNDIFEROUS NEPHELINE-SYENITE FROM
EASTERN, ONTARIO

A CONSIDERABLE area of nepheline-syenite was discovered
about six years ago in Dungannon township, Hastings county,
Ontario, by Dr. F. Adams, who described the rock briefly in his
‘Report on the Geology of a portion of Central Ontario,” and
more fully in the American Journal of Science.* In 1896 corun-
dum was found in the same region by Mr. W. F. Ferrier, and in
the following year Professor W. G. Miller was instructed by Mr.
Archibald Blue, director of mines of Ontario, to examine and
report upon the corundum-bearing rocks. In the course of his
work it was found that the corundum occurred not only in ordi-
nary syenites but also in nepheline-syenite.* In November 1898
the present writer examined an outcrop of the latter rock for
the Bureau of Mines on York branch of Madawaska River at
the northeast corner of Dungannon township or just within Car-
low, several miles from Dr. Adams’ localities, and presenting a
number of new and interesting features.

The rock forms a ridge running nearly north and south for
about 350 yards with a width of about 20 yards, and having a
well defined schistose character, so that at first sight it would be
called gneiss. It is light to dark gray in color, the darker layers
containing much biotite, the lighter ones more nepheline and
plagioclase. On much of the weathered surface numbers of
small crystals of corundum stand out, having resisted weather-
ing better than the other constituents. In hand specimens of
the unweathered rock, however, the corundum is scarcely noticed,
and the rock has quite the appearance of fresh gray gneiss, the
nepheline looking like quartz.

*Geol. Surv. Can., 1892-3, Part J, p. 5; Am. Jour. Sci., Vol. XLVIII, July 1894,
pp. 10-18.

? Bur. Mines, Ont., Vol. VII, pp. 210-212.
437

438 JAS 22, (C(QULISML ANG

Near the southern end of the ridge an irregular dike a few
feet wide crosses the gneissoid rock, reminding one of pegmatite.
It is white and consists of immense individuals of nepheline and
muscovite, often several inches or even a foot long, with small
patches of blue sodalite. No feldspar was seen in the dike,
unlike examples described by Adams,’ and no corundum was
found in it.

As usual in nepheline-syenites there is great variation from
point to point in the rock, easily seen on weathered surfaces and
still more marked in thin sections. Adams finds, as essential
ingredients of the outcrops near Bancroft, nepheline, plagioclase,
and biotite or hornblende in small amounts; but scapolite and
calcite usually occur, as well as various minor accessory minerals.
Thin sections from the locality here described show more variety
in constitution. All the minerals mentioned, except hornblende,
occur, and the feldspars include orthoclase and also a little
microcline as well as microperthite. The soda-lime feldspars are
generally present in much larger amounts than the potash feld-
spars, and seem to have a wide range in composition as deter-
mined by optical means. A few have angles of extinction of
4° or 5° from the twin plane and appear to be albite as in the
rock examined by Adams, others having a very small angle are
probably oligoclase, while a considerable number range from
17° to 23° indicating labradorite. Some have broad and sharply
cut twin lamellae, others very narrow and obscure ones. All
the feldspars are beautifully clear and fresh as a rule, much more
so than those of the associated Laurentian gneisses and granites.

The nepheline also is generally very fresh and, as mentioned
by Adams, has not the color nor oily luster of eleolite, though
it seldom shows crystal forms. Large individuals often contain
inclusions, minute crystals of hornblende, of biotite, and long
rows of tiny dots of a transparent doubly refracting mineral.
Calcite inclusions sometimes occur completely enclosed in fresh
looking nepheline. In one example the somewhat weathered
nepheline contains crowds of slender transparent fibers or

"lbid., p. 11.

CORUNDIFEROUS NEPHELINE-SYENITE 439

somewhat bent cords, having a little the look of apatite but with
a small angle of extinction, perhaps tremolite. Occasionally
decomposition products occur along fissures, having the appear-
ance of kaolin but without any distinct structure.

Scapolite is found in about a third of the sections, sometimes
almost to the exclusion of other colorless ingredients and has
the look of a primary mineral. Its anhedra meet the adjoining
feldspar or nepheline in a sharply defined way with no hint of
weathering in the latter minerals. Muscovite is a very common
constitutent of these rocks, being found in more than half of
the thin sections examined, generally as large primary looking
individuals, sometimes associated with biotite though often with-
out it. Biotite is practically the only dark mineral in the rock,
hornblende not having been observed. As in the specimens
examined by Adams, it is very dark in color and has a very
small axial angle. Augite was found as small blue-green anhe-
dra in one section only. Magnetite was not found, and apatite
was rare.

The most interesting accessory mineral is corundum, which
sometimes occurs in fairly well formed barrel-shaped crystals
half an inch in length, but is usually smaller and often forms
only minute rounded grains. Its color is gray or less often pale
bluish. Owing to the hardness of corundum it was found diff-
cult to prepare sections rich in crystals and only two have been
studied. Under the microscope their high refractive index and
greater thickness than the rest of the section cause the corundum
grains to stand out sharply. They are apt to be arranged in
clusters in association with muscovite, often completely enclosed
in at:

Although the rock here described has a well marked schis-
tose structure, there is nothing in its microscopic characters to
suggest shearing or crushing, no mortar structure nor granula-
tion, and seldom even undulatory extinction to hint at a state of
strain. The rock as a whole is hypidiomorphic granular, and
except corundum none of its constituents show much tendency
to crystalline form.

440 A. P. COLEMAN

The coarse-grained dike with its individuals of nepheline
half a foot wide is not easy to study in thin sections. The
nepheline proves under the microscope to have been slightly
fractured, very narrow fissures being filled with a rather brightly
polarizing mineral, perhaps feldspar. The few inclusions are much
like those of the nepheline in the schistose rock, but in one sec-
tion rather large portions of muscovite are enclosed. The large
crystals of pale lavender muscovite have no unusual characters
except their often perfect idiomorphy as against nepheline and
sodalite. The crystals are not hexagonal in cross section but
four sided having one angle of about 60°. The basal cleavage
is somewhat inclined to the prismatic edges, though a series of
pyramids having a very long C axis makes it difficult to deter-
mine the angle. In thin sections cut across the cleavage this
muscovite has an extinction angle of 3° to 5°.

If single thin sections were to be diagnosed alone four quite
distinct types of rock could be described from this outcrop; a
nepheline-muscovite rock; a rock made up chiefly of scapolite
and muscovite with a little biotite, plagioclase, and nepheline; a
rock containing about equal parts of plagioclase and nepheline
with some mica; and a rock consisting of orthoclase, microcline
and nepheline with some mica. There are, however, transitions
between these varieties, and it’would be unwise to split up what
is so evidently a geological unit into rocks of different names
when the whole is so well defined in general character, though
each hand specimen shows differences from its neighbors.

No analysis has been made of this rock, but one specimen
yielded nearly 10 per cent. of corundum in a heavy solution.
As there was no magnetite nor other heavy mineral present the
separation was very complete, corundum having a much higher .
specific gravity than the other ingredients. Since every mineral
present, except the trifling quantity of calcite and apatite, contains
alumina, nepheline in particular to the extent of more than 30
per cent., this oxide must occur in very large amounts. On the
other hand iron oxides must be very low, since the only iron-
bearing constituent is biotite.

CORUNDIFEROUS NEPHELINE-SVENITE 441

A specimen of nepheline-syenite was obtained from Lan-
caster’s farm, some miles west of the locality just described,
from a small outcrop showing no schistose structure. It is
coarser grained, but of the same color and general appearance
as the rock from York branch. Thin sections show, however,
that it has been subjected to shearing forces, since there is a
granulation round the larger pieces of feldspar and nepheline
suggesting mortar structure. Nepheline is present in large
amounts and also a peculiar type of microperthite having long
fibrous looking inclusions of one feldspar in another. the main
mass being in parts very finely striated (anorthoclase?) with twin
lines making an angle of about 23° with the most marked cleav-
age. Oligoclase and biotite occur in smaller amounts, the latter
as usual very opaque. Some of its outer scales weather to a
bronze-brown color, are dichroic, and have the optical axes much
farther apart than in the fresh mica.

Specimens of a medium-grained white rock dotted with
darker minerals come from a locality not visited by the writer,
in Methuen township, Peterboro county, and are interesting as
containing many dark brown corundum crystals having a bright
bronze luster on basal partings, as well as minute crystals of
magnetite.

Thin sections of one specimen disclose chiefly plagioclase,
finely striated and with a low angle of extinction from the twin
plane; a little microcline, nepheline and muscovite’ making up
the rest of the rock. Sections of another specimen very similar
in appearance contain more muscovite and a large amount of
nepheline, or rather of a turbid decomposition product, con-
fusedly scaly or fibrous, having high double refraction. The
mineral seems to have parallel extinction, fuses readily without
intumescence to a white glass, and gives water in the closed
tube, so that it is no doubt a uniaxial or rhombic zeolite, per-
haps natrolite. The corundum is very opaque so that only
minute particles of crushed crystals can be studied satisfactorily.
It contains many inclusions of two kinds, slender black needles
lying parallel to one another, and brownish-red strips and plates

442 A. P, COLEMAN

somewhat irregularly shaped and placed. The latter are prob-
ably hematite and produce the bronze luster seen on basal
planes of the corundum. Extinction is parallel to the needle-
like inclusions, and there is a rather strong dichroism, violet
when the needles are parallel to the chief section of the lower
nicol and reddish-brown in the opposite position. Some frag-
ments, no doubt parallel to the basal plane, are not dichroic.

The first of the two specimens might be named a plagio-
clasite (anorthosite contains a more basic feldspar) if taken sepa-
rately, but the second does not differ from typical examples of
the York branch nepheline-syenite except in the complete
weathering of its nepheline, and probably both are varying
forms of the same rock mass.

Through the kindness of the director of the Bureau of Mines
specimens of corundum rocks from Raglan township in Renfrew
county, about twenty miles northeast of Dungannon, have been
placed at my disposal. One is white, somewhat schistose, and
much like the Methuen specimens except that it contains biotite,
and that the pale greenish corundum crystals are almost an inch
in diameter and have no bronze shimmer on basal planes.
Under the microscope it is found to consist mainly of plagio-
clase (oligoclase) and biotite, the latter pale greenish-brown,
faintly dichroic and with a small axial angle. There are also a
few large patches of colorless muscovite having a large axial
angle. The specimen has the mineralogical composition of a
diorite, though of a very unusual character; but Professor Miller’
states that nepheline-syenite occurs close by, apparently part of
the same rock mass, though not so highly corundiferous.*

These white rocks were taken for limestone by farmers of
the region, and an attempt was made to burn them for lime, of
course, in vain. Hand specimens, partly fused, were taken from
the kiln and supposed to be nepheline-syenite, many of them
doubtless having that composition; but the one provided for
microscopic examination contains no nepheline. It is evidently
part of a bowlder and is schistose and pale gray to white on the

*Bur. Mines, Ont., 1897, p. 222.

CORUNDIFEROUS NEPHELINE-SVENITE 443

surface, but mottled bright blue and white where broken. Under
the microscope the rock is found to consist of scapolite, soda-
lite and biotite with a very little orthoclase. The scapolite
forms the greater part of the rock, the spaces between its
anhedra being filled with sodalite; the latter blue throughout
when in small portions, but only on the edges when in large
ones, the center being colorless and isotropic. The bowlders are
said by Miller to be blue only after being burnt in the lime-
kiln.

The biotite is deep red-brown in color, has a high absorption
and a wide axial angle, perhaps the result of heating; just
as many dark biotites turn brown by weathering and have a
wider angle between the optical axes.

There are small quantities of an unknown mineral present,
white, transparent and having a low double refraction, so as to
give only dull blue or purple tints between crossed nicols. Two
or three sections of it show an axial image consisting of a black
cross opening out about as far as in many biotites, but without
colored rings. It is optically positive.

About eleven years ago the writer collected a considerable
number of specimens of nepheline-syenite from drift bowlders
in the neighborhood of Cobourg, Ontario, which lies about
south-southwest of the localities referred to above and from
fifty to a hundred miles distant from them. At that time neph-
eline-syenite had not yet been reported from the province.?
In a general way these specimens correspond in appearance and
composition to those that have been described, though a num-
ber of additional minerals occur in them, the more important
being hornblende, augite and garnet, both of the ordinary kind
and melanite, the brown variety. Only one of the specimens
collected then contains corundum; and it, though closely like
the others in appearance, shows little or no nepheline and
resembles in mineralogical constitution, one of the specimens
from Methuen. The purplish-gray corundum crystals are quite
large, and thin sections show the same needlelike inclusions

* Trans. Roy. Soc. Can., 1890, pp. 14-18.

444 A. P. COLEMAN

and dichroism as the Methuen crystals, but not the hematite
plates.
As there is not much doubt that the Cobourg drift bowlders
originated in the nepheline-syenite region to the northeast, they
have been referred to here and may be considered in connection
with the rocks previously described.

In spite of the great variations in mineralogical composition
to be seen in hand specimens all the rocks referred to have
much in common; they are white to gray in color, generally
schistose, often corundiferous, and present the same general
habit, so that in field work they are naturally thrown together
as nepheline-syenite and can be sharply distinguished from
adjoining Laurentian gneisses, granites, and syenites. While
not all of them contain corundum in large amounts they serve
as a general guide to the discovery of the corundiferous rocks
and are so used by prospectors for that mineral. Some of the
ordinary syenites of the region, however, contain corundum also,
and the largest crystals found occur in them.

Just why the magma which has solidified into the groupof rocks
described above should be so versatile in regard to mineralogical
composition is not easily explained; but no other rock known
to the writer shows so great a variety of types within short dis-
tances as may be found in the nepheline-syenites. It may be
that experiments such as those of Morozewicz' will give the clue
to this variability, which seems to depend on the large proportion
of alumina in the original magma. The corundiferous varieties
of nepheline-syenite represent magmas supersaturated with
alumina but not saturated with silica.

A. P. COLEMAN.

™See Review by T. A. JAGGAR: JOUR. GEOL., 1899, Vol. VII, No. 3, pp. 300, etc.

tit wehbe Cr OF SEA BARRIERS UPON ULTIMATE
DRAINAGE

THE causes which determine the location of river courses in
the neighborhood of their discharge into the sea, where the cur-
rents are slow and their power of erosion small, are often quite
insignificant.

If, however, a stream once becomes established in any given
course, and the region through which it flows becomes elevated,
its sluggish current at once becomes active and forms a valley
of greater or less depth. Its tendency through subsequent
changes in the land level is to remain in the valley approximately
as originally formed. This tendency is especially strong if this
original valley is parallel with the strike of the strata.

It is not the purpose of the present paper to discuss the
development of intricate drainage systems along structural lines,
and through long periods of time, but simply to suggest that a
drainage system may sometimes have a portion of its course fixed,
by spits and barrier beaches along the coast line, at the same
time that the sediments which are to form the rocks of its future
drainage area are being deposited ; and also that the drainage
when established thus early may remain more or less fixed
through its subsequent history.

Along coast lines generally, and especially along those of
gently sloping coastal plains, spits, bars, and barriers are more
or less common. For our present purposes these may all be
spoken of as barriers, and so far as the present paper is concerned
it does not matter whether they are composed of sand, gravel,
or coral; neither do the forces by which they are built up need
to be discussed.

The lagoons between the barriers and the shore vary in
length with the barriers, from a few hundred yards to many
miles. Such lagoons are parallel to the shore and_ usually

445

446 J. F. NEWSOM

almost at right angles to the course of the drainage entering
them.

The drainage from the land must pass through these lagoons,
often for almost their entire length before it can reach the sea
through gaps in the barriers or around their ends. Thus it
happens that long, low barriers, often of soft sand, and of
insignificant height, which if inland would be slight obstacles
to erosion, often control large drainage areas (Fig. 1).

Fic. 1.— Barnegat Bay on the coast of New Jersey. The drainage, at present
deflected by the barrier, passes through the bay and into the ocean.

Excellent examples of drainage controlled by barriers are to
be found developed to a greater or less extent along the coasts
of almost all countries. Along our own coasts the most marked
examples are the streams flowing from Texas into the Gulf of
Mexico; Indian River along the east coast of Florida; and the

EFFECT OF SEA BARRIERS UPON DRAINAGE 447

streams emptying into Albemarle, Pamlico, and neighboring
sounds. The drainage in all these localities is deflected many
miles. Many less marked instances of deflected streams may be
seen upon almost any map of a long coast line.

The writer’s attention has been called by Dr. J. C. Branner
to the stone reefs along the coast of Brazil. These reefs bear

Fic. 2 Fic. 3

Fic. 2 shows a shore line whose drainage is deflected by a barrier. The cross-
section shows the relations existing between the barrier, lagoon, new, and older strata.

Fic. 3 shows the arrangement of drainage, as represented in Fig. 2, after the
elevation of the land. The “lagoon portion” of the stream is here shown as being
directly along the contact between the newer and older groups of strata.

the same relation to the shore as ordinary sand barriers, and they
are probably old barriers whose sands early became cemented.
In such cases of early solidification, the ‘‘lagoon”’ portion of
the resulting land stream is, of course, held in position much
more firmly than in the case of loose sands.

448 J. F. NEWSOM

Shore deposits usually have a slight seaward dip. It hap-
pens, therefore, that the streams entering lagoons behind barriers
may not only have their courses determined early in their history,
and that subsequent erosion after the land becomes elevated
tends to deepen the channel in the position determined, but
also that this position is parallel with the strike of the strata.
The subsequent tendency of the stream, therefore, is to remain
in this original course established for it by the lagoon, as shown
in Figs. 2 and 3.

If the coast, along which such stream deflection occurs,
happens to be rising, or if the barriers are being added to from
the seaward side, the barriers, at first narrow and low, may
become gradually wider and higher and finally form a considera-
ble land area. In this new area a new drainage system will
develop, a portion of it being drained landward to its old lagoon,
the rest draining either directly or through a new lagoon, into
the ocean, as shown in Figs. 3 and 4.

If the land level remains unchanged, the lagoon is left inland
and controls the drainage of the region on its landward side
with little or no tendency toward erosion. If, however, the land
becomes slowly elevated, the old ‘lagoon portion” becomes an
active stream and cuts out a channel in and along the strike of
the new rocks. As the shore becomes more and more elevated,
and the stream is left further inland, this portion of the channel
becomes more firmly established in its course. Thus it becomes
an inland stream, which had a greater or less portion of its
length originally established parallel with the coast, with the
contact between groups of strata and also with the strike of the
rocks, and not across the strike or outcrop, as is so commonly
taken for granted for the original courses of streams. (Fig. 3.)

It is obvious from what has been said that the “lagoon por-
tions’’ of streams will be determined in a direction approximately
parallel with the general direction of the contacts of the newly-
formed geologic groups; they may be directly along this line,
or they may be several miles on either side of it.

Fig. I may be taken as a type to illustrate this. Here the

EFFECT OF SEA BARRIERS UPON DRAINAGE 449

barrier of ‘‘alluvium”’ enclosing Barnegat Bay on the coast of
New Jersey is from three to five miles from the contact between
the ‘‘alluvium” and the older beds of gravel, sands, and clays.
If Barnegat Bay were silted up by sediments from the landward

' . . E
c ree) . ) ae x
t 1 cee ht Fs r
4 - a
~ ris eso Serr
1 A .
a ey; Sans Ps
te a
4 . .
’ + .
L i H ees
‘ .
te ie ‘.
L ' i :
ct - >
- Ldn! L— = sy
Bd TO AG :
‘ -
=: e Cer
ae LA ay re
7 \
t ey
c -
Cee

Vig gots aes ae .
«i. New Strate °

Fic. 4 is a further development of Fig. 3; the “lagoon portion” of the old stream
having for the most part settled itself down in the underlying strata. The contact
between the newer strata and the older being shifted seaward by erosion, the line of
contact is some distance to the seaward from the stream. If the underlying older
beds are very hard, the stream might continually shift itself along the line of contact,
instead of cutting down into the hard beds below. A part of the old “lagoon portion,”
instead of cutting down into the underlying rocks, is shown as having been shifted
down the dip of the newer beds, and as flowing parallel with the contact but to the

seaward of it.

side, its lagoon might be shifted close up against the barrier.
If, under these circumstances, this coast should be elevated and
the shore line should be shifted some miles seaward, the ‘lagoon
portion”’ of the resulting stream would be approximately parallel

450 J. f. NEWSOM

to the strike of the rocks, and also to the upper and lower con-
tacts of the particular group of strata formed, though several
miles removed from either of those contacts.

On the other hand, a stream flowing parallel with the contact
and not far removed from it might cut down completely through
the series of strata by which its course was originally determined,
and reach the older underlying rocks. Under such circum-
stances the newer beds through and along the edges of which
the stream originally flowed, would in time be removed by
erosion for some considerable distance from the line of contact,
as shown in Fig. 4.

It is, of course, difficult to point with certainty to streams
at present far inland that have had their courses originally
determined in the manner suggested. This explanation offers
itself, however, for streams that now flow parallel to and in the
neighborhood of contacts between sets of beds of different ages,
as also for streams flowing parallel to preéxisting coast lines.
It is not improbable that many streams flowing with the strike
of strata, and whose courses have been attributed to stream
capture, owe these courses to the simple fact of their having
been primarily established in that position as here suggested.
Many such streams may be seen on any detailed geologic and
drainage map of our eastern and southern coastal region, though
they are by no means limited to such regions.

This explanation is suggested as a probable one in account-
ing for the sudden southwest deflection of the Delaware River
at Bordentown, N. J., and the Potomac near Washington, and
for the sudden turn of the Susquehanna into the upper portion
of Chesapeake Bay, which may be considered as its exten-
sion.

The same explanation is suggested also in, regard to the
Tennessee River for the lower portion of its course where it
flows northward through west Tennessee and Kentucky.

Black River, in Arkansas, flows for almost its entire length
near the line of contact between Tertiary and Paleozoic rocks.
This stream may have had its course originally established,

EFFECT OF SEA BARRIERS UPON DRAINAGE 451

parallel to the old coast line in much the same way that Indian
River, Florida, has its course fixed at the present time.

Many others could be mentioned, but these serve to show
the character of the drainage that might be expected from the
suggested causes.

It is not meant to imply by the foregoing remarks that all
barriers that may be formed will exercise control on the ultimate
drainage. Probably most of those formed are quickly destroyed
as the shore line encroaches or recedes. It is hardly reasonable
to suppose, however, that all barriers formed through past
geologic ages have been disposed of thus easily.

Joun F. Newsom.

STANFORD UNIVERSITY,
California.

SEASON AND TIME ELEMENTS IN SAND-PLAIN
FORMATION

THE SEASON ELEMENT

Tue term sand-plain is here used in the generally accepted
sense, that is, to designate the sand delta formed at the mouth
of a glacial stream as it issued from the ice margin into the stand-
ing waters of a glacial lake or into the sea. The bulk of such a
plain is made up of a succession of layers of fine material slop-
ing at an angle of 15° or more in the direction in which the cur-
rent is moving, or away from the head of the plain. Upon these
layers, which are known as fore-sets, rests a comparatively thin
and nearly horizontal layer of coarse material known as top-sets.
A third class of layers is represented by the horizontally strati-
fied clay beds deposited in front of the constantly advancing
fore-sets, and partly overlain by them in consequence of this
advance. In addition there is sometimes a fourth, but much less
extensive series of layers which have slopes just the reverse of
those of the fore-sets. They are known as back-sets, and are
formed, sometimes by the upward movement of the water as it
leaves the ice and passes up and over the sand-plain,* and some-
times by the settling of the margin of the plain in consequence
of the melting of the ice upon which it may have partially rested.

Wherever sand-plains have been exposed it has been found that
the development of back-sets is insignificant, seldom amounting
to more than twenty or thirty feet even in the largest plains.
It is evident that if the margin of the ice were retreating during
the construction of a sand-plain, the formation of back-sets by
the first method would at once become a prominent feature of
the deposition. It is doubtful if back-sets of this type have
ever actually been noted, and back-sets of any sort are, as we
have seen, of rare occurrence and slight development. This

«Bull. Geol. Soc. Am., Vol. I, 197.
452

ELEMENTS IN SAND-PLAIN FORMATION 453

shows conclusively that the forward growth of the delta must
have been extremely rapid, for an ice margin bathed constantly
by the waters of the sea or a glacial lake could not long remain
stationary. That the time of growth was a short one was early
urged by Davis and is generally admitted by those familiar with
such deposits. Even in the case of many of the larger plains
it seems clear that the time of growth should be measured by
months rather than by years, and the assumption that they are
the result of a single season’s stream work is not unwarranted.

If this view is accepted, the question at once arises as to
whether the plain represents the deposits of the whole, or only a
part of the season of ablation. The first thought would natu-
rally be that they represent the whole, but on more careful con-
sideration this seems less probable. The observations upon sand-
plains show that there was practically no backward melting of
the ice during their formation. The retreat, then, must have
taken place under conditions more favorable to the melting or
breaking up of the margin of the ice sheet than those existing
during the formation of the plains, and to maintain that the
sand-plains represent the whole of the summer periods of melting
would mean the reference of the periods of retreat to the winter
season, a conclusion not in harmony with the laws of nature.

As an alternative, it might be considered that the sand-plains
represent summers of only moderate warmth, while the periods
of’ melting were characteristic of seasons of a considerably
higher average temperature. The melting of the ice, the dis-
charge of the glacial streams, and the amount of detritus, would
all have been increased under such conditions. In reality we
find that often only a slight deposition of sediments took place.
between the stages of sand-plain growth, especially when plains
are but short distances apart, as in the case of the Bar-
rington and Nyatt Point sand-plains, hereafter to be described.
Here the intermediate area is practically free from deposits of an
inter-sand-plain period, indicating that the retreat of the margin
took place during a period when little detritus was being set
free from the ice by ablation.

454 MYRON L. FULLER

A consideration of the conditions obtaining during the clos-
ing stages of the ice sheet leads to the conclusion that the
periods or steps of the retreat in the vicinity of the Barrington
Plain were characteristic of spring, corresponding more or less
roughly to the present months of March, April and May.

Following is a summary of the reasons: (1) The insignifi-
cant development, or complete absence of back-sets in the most
typical sand-plains, show that the retreat was not characteristic
of the summer period. (2) The fall represents a waning, and
the winter a cessation of all the conditions that can in any way
be regarded as favorable to the ice retreat. The retreat cannot,
therefore, be regarded as characteristic of these periods. (3)
Though the actual precipitation may have been no greater than
in the winter months, precipitation in the form of rain probably
reached its maximum in the latitude of northern United States
during the months of early spring. It is well known that water
attacks ice much more rapidly than air at the same, or even
higher temperatures. The period of spring rains must, then,
have been one of rapid ablation. (4) The precipitation of the
winter months must have been mainly in the form of snow, which
according to Upham, would reach a maximum within a com-
paratively short distance of the margin. Under the influence of
the spring rains the deep snow must have rapidly melted, helping
swell the glacial, and especially the superglacial streams to
sizable turrents. The rapidity with which such superglacial
streams cut into the ice is well shown by some of the superglacial
streams of Greenland, which, though usually short and of small
size, have often sunk tosome considerable depth into the ice.
Such streams near the margin of the waning ice sheet would
have rapidly cut through the ice to the very bottom, leaving
detached pieces of various sizes and shapes which, however,
would melt with comparative rapidity. (5) The streams during
the spring, being fed mainly from the melting snow or direct
precipitation, would carry a proportionally small amount of
sediment, and the detritus instead of being deposited at a single
point, as in the case of the sand-plains, would be distributed

ELEMENTS IN SAND-PLAIN FORMATION 455

over a large area as an inconspicuous sheet. (6) In the
summer the ice margin would become stationary and the depo-
sition of the detritus, which was derived almost entirely from
the ablation of the débris-laden ice, would be concentrated at
definite points. ;

Although from the above considerations it seems reasonable
to refer the shorter ice retreats between sand-plain stages to the
spring months, it is probable that the longer retreats represent
longer periods, perhaps in some cases years in length. In this
case the absence of inter-sand-plain deposits may be more
seeming than real, because of the sheet form of such deposits.

TIME ELEMENT

If the months of December, January, and February are
eliminated, as there can be no doubt they should be, from the
time of sand-plain growth, the retreat of the ice and the deposi-
tion of the plain must have taken place inthe remaining nine
months. The distance between sand-plain stages varied from a
fraction of one up to several miles, and three months certainly
seem none too long atime for sucha retreat. If this be so,
the sand-plains, or at least those of modern size, must have been
formed in the six months still remaining.

A study of the conditions now existing in the larger glaciers
of Alaska, showed at once that sucha rate of deposition was by
no means improbable. A calculation based on such conditions
could not fail to be of interest, and would give valuable indica-
tion as to the probability of the general estimates. The results
showed an unexpected and surprisingly close agreement with
the estimates.

Basis of calculations —Evidence as to the time of formation
of sand-plains is afforded; (1) by the bulk of the sand-plain
itself, and (2) by the bulk of the accompanying clays, which
from their mode of formation, are known to be simultaneous in
development and coextensive as to time. The time estimate is
obtained by dividing the bulk by the daily discharge of sedi-
ment of the glacial stream. To find this discharge of sediment

456 MYRON L. FULLER

it is necessary to know the area of the cross-section of the
stream, the velocity of its flow, and the percentage of sediment
carried. The first two values are indicated by the esker and the

ove
Oe d

i

CL

NARRACANSETT BAY.
a}

1 MILF.

Fic. 1.—Map of Glacial Deposits, Barrington, R. I.t
Contour interval, 20 feet.

material of which it is composed. The latter must be estimated
from observations upon glacial streams existing under similar

*The geology is taken from map given by Mr. J. B. Woodworth in Seventeenth
Ann. Rept. U.S. Geol. Surv., Pt. I, Pl. LXII.

ELEMENTS IN SAND-PLAIN FORMATION 457

conditions at the present time. Such observations have been
made by Wright, Reid, and others in regard to the fine sedi-
ments such as make up the so-called glacial clays, and it is upon
these observations that the present estimates are based.

Locality selected. —Conditions favorable to a calculation of
the time of formation from the extent of the plains, or their
associated clays, are in almost every case wanting. In 1896,
however, Woodworth described? and mapped a series of unusu-
ally typical deposits in the town of Barrington, R. I. A visit to
the locality showed the conditions to be almost ideal, and
admitting of calculations of some definiteness. The clays were
selected as a basis of calculation in preference to the sand-plain
itself, because of the greater number and reliability of the
Alaskan observations upon this class of sediments.

FGA

Fic. 2.—Section across Barrington, R. I., showing relations of clays to sand-
plains. A, Terrane of Carboniferous age; B, Glacial drift older than Nayatt Point
stage; C, Clays contemporaneous with the Nayatt Point sand-plain; E, Gravel and
sands deposited upon the melting of the ice along the head of the Nayatt Point plain ;
F, Barrington sand-plain; G, Barrington clays; H, esker; I, gravel and sands laid
down upon the melting of the ice back of the Barrington plain. —J. B. WoopWoRTH:
Seventeenth Annual Report U.S. Geol. Surv., Part 1, p. 987.

Barrington clays.—TVhese clays are exposed at the surface
over an area of about six tenths of a square mile (Fig. 1). On
the south the clays rest against the ice-contact slope of the
Nyatt Point sand-plain, while on the north they extend as a
gradually thinning wedge beneath the Barrington plain, reaching
their northern limit approximately along the ice-contact slope of
this latter plain (Fig. 2). The depth of the clays in the vicinity
of the railroad, as shown by borings, is about sixty feet. With
the exception of one slight break there is a ridge, partly till and

Seventeenth Annual Report U.S. Geol. Surv., Part I, 987, 988; and Am. Geol.,
VoL. XVIII, 161-164, 391, 392.

458 MVRONVE. POLE ER:

partly of modified material, connecting the two sand-plains on
the east, and having an average height of about forty feet. On
the west there is no marked rise between the clays and the
waters of the bay, the latter even at the present time having
access’ to the clays by a fair-sized estuary. The surface of the
clays is practically at sea level.

The clays, which vary from gray to blue-gray in color ware
composed principally of quartz flour—the ultimate product of
glacial scouring—with a comparatively slight intermixture of
true clay. Their amount, allowing for the thinning out in vari-
ous directions, and taking their specific gravity as 2.5, is found
to be approximately 95.3 million tons.

Conditions at time of deposition.—The heights of the two sand-
plains are about fifty feet and indicate a probable height of
water at the time of their formation of at least forty feet above —
the present sea level. The ice on the north, the ridge on the
east, and the Nyatt Point plain on the south would form an
inclosed bay, with practically no opening except at the west.
Here, however, there must have been an opening something like
three fourths of a mile wide and thirty-five to forty feet deep
connecting with the sea and allowing a more or less complete
commingling of the salt and fresh waters.

Into this inclosed bay emptied, as indicated by its esker, a
glacial stream 150 feet wide, with a probable depth of some
twenty feet, and a velocity sufficient at times to move pebbles up
to six inches in diameter. This would indicate a maximum
velocity of a little over six feet per second, but the average
material composing the esker would require a current certainly
not over five feet per second. The discharge of such a stream
would be 15,000 cubic feet per second.

The area of the cross-section of the outlet from the inclosed
bay was about 138,000 square feet, or some forty-six times that
of the glacial stream. If discharge took place uniformly through
the outlet the velocity would have been one and one third inches
per second. If the flow of the fresh water took place as a sur-
face current, as would have been the tendency, a somewhat

ELEMENTS IN SAND-PLAIN FORMATION 459

greater velocity would have resulted, but not enough greater to
have prevented the settling of the sediment. The ebb and flow
of the tide, which is about four feet, would have decreased the
outflow some 25 per cent. during flood tide, and increased it by
a corresponding amount during the ebb.

The average distance through which the water would move
in its passage from the mouth of the glacial stream to the outlet
would be at least a mile. The current, which at the frontal slope
of the sand-plain had a velocity, as indicated by the material
deposited, of some eight inches per second, would decrease until
certainly not over three inches per second at the outlet. Its
passage would require fully four hours.

Sediment of glacial streams. — According to Helland,’ as quoted
by Reid,? the maximum sediment values of their respective
regions are represented by the Unteraar glacier of Switzerland,
which carries .142 grams per liter; the Langedal glacier of Nor-
way, Carrying .513 grams; and Alangordleck glacier of Green-
land, carrying 2.37 grams. Both Wright and Reid found much
more sediment in the waters from the Muir glacier of Alaska,
the former recording a load which reduces to 12.12 grams per
liter,3 and the latter a load as high as 12.98 grams per liter.t As
the Alaskan glaciers most nearly represent the conditions
obtaining during the closing stages of the continental ice sheet,
I have taken Reid’s value of 13 grams (actual value, 12.98
grams) as a basis in calculating the time of formation of the
Barrington clays.

In all probability the sediment discharged by the streams
draining the continental ice sheet was even greater than that of
the most heavily loaded glacial streams of today. I have sought
to neutralize this difference as much as possible by applying as
a mean value to the Barrington deposits the maximum value of
the Muir glacier sediments.

* HEIM’s Gletscherkunde, p. 363.

? Sixteenth Annual Report, U. S. Geol. Surv., Pt. I, p. 457.
3Ice Age in North America, p. 64.

4 Loc. ctt., ps 454.

460 MYRON L. FULLER

Rate of settling.— Recently, in connection with professional
work for the Metropolitan Water Board of Massachusetts, Pro-
fessor W. O. Crosby has incidentally had occasion to determine
the rate of settling of the finer portions (2. ¢., quartz-flour) of both
the till and the stratified drift. No definite maximum limit has
ever been fixed for the grains of quartz flour, but in the experi-
ments in question this name was applied to that portion passing
through a sieve of 170 meshes to an inch. The larger grains are
about 34, of an inch in diameter.

In the experiments, the results of which Professor Crosby has
kindly placed at my disposal, 5 grams of the quartz flour were
introduced at the top of a half-inch tube containing five feet
of water. The time of settling was then taken. The results
showed that fully 75 per cent. of the material settled within
thirty minutes from the time of insertion, and in the majority of
cases none whatever remained in suspension at the end of sixty
minutes. In other cases a distinct turbidity, probably due to
true clay, was still noticeable at the end of this time. This was
determined by filtering and weighing, the amount varying from
a mere trace up to IO per cent.

The results show that even in fresh water the settling of
quartz flour is very rapid, the greater part settling at a rate of at
least ten feet per hour. In the inclosed bay in which the Bar-
rington clays were deposited the water was salt, or at least
decidedly brackish, and the rate of settling must have been much
increased, especially in the case of the finer material, which,
according to W. H. Brewer, will settle as much in salt water in
thirty minutes as it would in as many months in perfectly pure
water.*. There can be no reasonable doubt, then, that practically
the entire amount of sediment brought in by the glacial stream
was deposited within the inclosed bay.

Statement of problem and results.— During a certain stage of
the ice retreat from the region of Narragansett Bay, the area
now covered by the Barrington clays stood at a level some forty
feet below that at present existing, and was covered by a body

Am: J. Sci., TI]; 20, p. 4:

ELEMENTS IN SAND-PLAIN FORMATION 401

of salt or brackish water which rested against the ice on the
north, and was practically cut off from the sea on the east by a
till ridge, and on the south by the Nyatt Point sand-plain. Into
this body poured.a glacial stream with a volume of some
15,000 cubic feet per second, and bearing a load which I have
assumed as a maximum to be 13 grams per liter, amounting to
526,500 tons per day. From experiment it has been found that
material like that of the Barrington clays settles very rapidly,
indicating that practically the whole amount brought in by the
glacial stream must have been deposited within the inclosed area
indicated.

The amount of the clay is some 95.3 milliontons. Dividing
this by the daily discharge of sediment of the glacial stream, she
time of the deposition of the clays is found to be 181 days, or almost
exactly six months.

General application. —Though in the sand-plains of different
localities, the proportion of sand and clay varies greatly, the
Barrington deposits taken as a whole probably represent very
nearly the average conditions. I am satisfied, therefore, that the
results obtained in the case of the Barrington plain, though
strictly speaking they are applicable only to this plain, represent
fairly closely the time required for the formation of the average
sand-plain. If, for the reasons given ona previous page (p. 454),
the ice retreat is considered as taking place in the early spring,
it would follow that these figures represent a maximum, rather
than a minimum, time limit. In the case of large plains, how-
ever, with areas of several or many square miles it may be pos-
sible to consider the period of deposition as extending over more
than one season of melting, there being in the meantime either
no retreat of the ice margin, or a retreat so slight that the inter-
vening space was completely filled, and the sand-plains united
into a single compound plain.

Remarks. — One of the points most strongly emphasized by
the results obtained, is the almost incredible amount of sediment
discharged by the Barrington glacial stream during the few
months of summer activity. The daily discharge of sediment by

462 MYRON L. FULLER

this small stream, not over 150 feet in width, was equivalent to
40 per cent. of that of the Mississippi.*

The small amounts of the coarse material, compared with the
amount of clay, is also a significant feature. It shows fully two
thirds of the detritus brought in by the stream was of the finely
comminuted quartz flour. The velocity was such that had the
current come in contact with the subglacial till to any extent the
percentage of coarse material would have been much greater. Its
absence indicates, therefore, that practically the entire amount
must have been derived from the ablation of the ice. The high
percentage of the finer débris contained within the ice is certainly
a striking feature.

Myron L. FULLER.
MASSACHUSETTS INSTITUTE OF TECHNOLOGY,

Boston, Mass.

tJ. B. WoODWORTH, Zoe. cit., 162.

eit PR rROGRAPHICAL PROVINCE OF ESSEX CO.,
MASS] “GENERA DISCUSSION: AND CONCLU-
SIONS] iV.

Analytical methods.—As far as was possible with the means
at my disposal the methods advocated by Hillebrand’ were fol-
lowed, some slight modifications being necessary owing to lack
of certain facilities in my laboratory. A word must be said in
recognition of the high character of the work of the chemists
of the U. S. Geological Survey. Petrologists generally are
deeply indebted to them for the service they have rendered the
science, not only by the investigation of methods and the very
large amount of excellent work which they have done, but also
for the high standard of excellence which they have set for
other analysts to follow.

Ignition H,O was determined in dry CO,. It will be seen
from the generally low summation of the rocks high in FeO
that this did not entirely prevent oxidation under the condi-
tions obtaining, but the error will not be high. The precipita-
tion with ammonia was always made twice, and three times in
the case of the basic rocks, in the presence of sufficient NH,Cl.
This is of the utmost importance, as pointed out by Pirsson?
and Hillebrand,3 on account of the tendency of MgO to be
coprecipitated with the Al and Fe hydrates. Neglect of these
precautions has rendered useless many analyses, but it is a point
which is often overlooked. With one exception, MnO was not
determined, since its amount was apparently small and its deter-
mination would have extended considerably the time necessary
for an analysis, and hence lessened their number. Alkalis
were, of course, determined by the Lawrence Smith method.

*CLARKE and HILLEBRAND. Analyses of Rocks. Bull. U. S. Geol. Surv., 1897.
2 PIRSSON, JOUR. GEOL., Vol. IV, 688, 1896.
3 HILLEBRAND, Of. cit, p. 39.

463

464 HENRY S. WASHINGTON

It must be noted that throughout this paper the terms acid
and basic refer only to the relative amount of SiO,, no con-
notation of the amounts of the other oxides being implied.

Use of the term petrographical province-—The idea which
underlies the general use of this term is that of a region of
igneous rocks which possess in common certain characters,
structural, mineralogical, or chemical, and in which the charac-
ters may vary cOntinuously from one end to the other of the
series of rocks represented. The term is usually applied to
large areas embracing several centers of igneous activity, which,
by their similarity in character, may be presumed to be related.
Its application in the title of this paper is somewhat restricted,
and therefore open to criticism, but seems justified on the
grounds of convenience, the evident relationship of the rocks,
and the fact that this region may serve as the type of the
still larger New England one.

In Table I are given my analyses of the

Chemical characters.
rocks of Essex county, with one by Dr. Eakle, and in Table II
the molecular amounts of the various oxides. It is to be borne
in mind that all references to the relative amounts of the oxides
are to their molecular amounts, and not to their percentages as
- obtained in the analyses.

The range in composition is very great, the rocks varying
from basic gabbro with 44 to acid granite with 78 per cent. of
SiO,. Al,O, varies considerably and is notably higher toward
the basic end. The total amounts of iron oxides are rather
high, Fe,O, being low and varying little, while FeO is higher,
especially so in the basic rocks. MgO and CaO behave alike,
being low in the more acid rocks, and suddenly much higher in
the basic. The alkalies areabundant, Na,O more so than K,O,
but, on the whole, do not vary as much as the other con-
stituents.

The rocks as a whole are rather acid, 7. e., they contain more
SiO, than most similar types elsewhere. The granite is
decidedly an acid one, the foyaites more acid than most nephe-
line-syenites, and the same is true of the pulaskites, the akerite

PETROGRAPHICAL PROVINCE OF ESSEX COUNTY .465

and nordmarkite, the tinguaite, sdlvsbergite, and paisanite. In
the basic rocks, on the other hand, the opposite seems to hold
goo d, that they are more basic than usual.

In the next place they are rich in both alkalis, and Na,O
is constantly greater than K,O. On the whole, however, Na,O
does not predominate to such an extent as to stamp the region
as essentially one of soda rocks, but is sufficiently predominant
to determine the character of the types, as shown in the min-
eralogical composition.

In general the rocks are rich in iron oxides, FeO being espe-
cially, and in some cases abnormally, high. It may be men-
tioned that TiO, is high, comparatively speaking, and that BaO
seems to be absent.

The province as a whole then, may be characterized as one
of rocks which are more acid or more basic than normal, high
in alkalis, with Na,O predominating over K,O, high in iron
oxides, especially FeO, rather high in Al,O,, and low in MgO
and CaO.

Mineralogical characters.—We find the main chemical features
well expressed in the general mineralogical composition. Cor-
responding to the high SiO, and alkalis, the prevailing feld-
spars are albite and orthoclase, with quartz-syenites abundant.
The albite molecule is very abundant, giving rise to the charac-
teristic microperthites and the albitic syenites of the litchfieldite
and pulaskite types. At the same time the soda-hornblendes
and soda-pyroxenes are common. The low CaO forbids the
formation of much lime-soda feldspar, which we find to be rare,
and even in some of the basic rocks the plagioclase is more
albitic than usual.

The paucity in MgO is of great influence. Olivine is rare
even in the basic rocks. A striking peculiarity in this connec-
tion is the replacement of the deficient MgO by FeO. This
gives rise to the presence of varieties of minerals normally mag-
nesian, but which are here largely ferrous instead. This is
exemplified by the abundance of the MgO-free biotites, lepi-
domelane and cryophyllite, as well as the occurrence of the

466 HENRY S. WASHINGTON

purely ferrous olivine, fayalite’ in the granite, and the presence
of the MgO-free ‘“ glaucophane”’ molecule in the blue horn-
blendes? of the region.

Discussion of oxide ratios—In Table IJ are given, below the
molecular amounts, several oxide ratios, which we may next
examine, since they serve to differentiate the rocks of the region
into groups.

Na,O

EO
_have seen, though often closely approaching it. A striking fea-
ture is that in ten or eleven cases it is either exactly or very near
a’ whole number; tel, 221, 3:1, 01 O21. Ini tenvothersent
closely approximates to multiples of a half; 1%:1, 2%:1,
314:°1, or 6%:\1. In only three or tour’ cases does atidities
more than about .12 from such figures. There seems to be a
tendency for Na,O and K,O to exist in stoichiometric ratios
with respect to each other. The same is true elsewhere, notably
in the Christiania region, where Brégger3 connects it with the
tendency of the alkalis to such ratios in nepheline and soda-
orthoclase. Such ratios, however, in igneous rocks are by no

This ratio is constantly greater than unity, as we

means general.

When we examine this ratio in the various rocks we see that
it is characteristic of certain rock groups. In the granite, the
quartz-syenite-porphyry and the quartz-syenites it is quite con-
stant, varying only from 1.09 to 1.17. In the aplite dike it is a
little higher, about 1.5. Inthe keratophyre and rhyolite it is still
higher, 1.40 and 2.20. As we go toward the basic end the
ratio increases, being 1.7 and 2.1 in the pulaskites, 2.2, 2.5, and
3.6 in the sdlvsbergites and biotite-tinguaite, and 3.0 in the
foyaites. In the basic rocks, from diorite down, the ratios are
constantly high, varying from 2.6 to 6.6, and is also high, 6,
in the analcite-tinguaite.

t PENFIELD and ForBES: Am. Jour. Sci. (IV), I, 129, 1896.

2H. S. WASHINGTON: Am. Jour. Sci. (IV), VI, 179, 1898.

3BrROGGER: Eruptivgesteine der Kristianiagebietes. I, 165, 1894, and III,
249, 1897.

PETROGRAPHICAL PROVINCE OF ESSEX COUNTY 467

It will be seen that in what are obviously connected series of
rocks there is a regular variation in one direction, an increase
toward the basic end. The most striking instance is the paisanite-
tinguaite series, in which the ratios are 1.23, 2.17, 2.47, 3.62, and
5-97. Also in the pulaskite-foyaite-essexite series, where the
Fatios-are 1,71, 2.00, 3.00, 2.98, and 3.64. The granite, quartz-
syenites, diorites, and gabbros show the relation less well,
though even here the ratio is markedly higher in the basic
members.

These observations leave no doubt of the fact that in Essex
county Na,O increases relatively to K,O as SiO, decreases.
This agrees with the Christiania region, where Brégger* shows
that in the grorudite-tinguaite series the same holds good. In
both cases the effect is due chiefly to increase in Na,O relatively
to SiO,, K,O remaining comparatively stationary. The line
giving the ratio of Na,O:SiO, will show this for Essex county.
Such a variation is not universal, as in other regions exactly the
contrary obtains,” the K,O increasing as SiO, decreases.

It is evident, therefore, that Na,O and K,O differentiate
with respect to each other, a fact to which Pirsson has already
called attention.3 This is of theoretical interest since it indicates
that, notwithstanding their general similarity, there isa difference
between the two alkalis in their functions in igneous rocks, a
subject which space does not permit of being treated here.

FeO

Bes O:
the preceding, ranging from 0.37 to 16.0, but examination reveals
certain ~tregularities:. It is very high in the granite, aplite,
quartz-syenite, and porphyry, and in all the basic rocks. It will
also be observed that it is higher in the dike rocks than in their
corresponding plutonic forms. It is lower in the paisanite and
sdlvsbergites, still lower in the pulaskites and foyaites, as well as

The variations in this ratio are far greater than in

™BROGGER: of. cit., Vol. III, p. 249, note 1, 1897.

?PirssON: Bull. 139 U.S. Geol. Surv., p. 138, note 5, 1896. HARKER: Geol.
Mag., Vol. IX, 203, 1892.

3 PIRSSON: Bull. 139 U.S. Geol. Surv., p. 138, 1896.

468 HENRY S. WASHINGTON

in the rhyolite and keratophyre, and lowest of all in the
tinguaites.

It is evident, granting that these relations are not fortuitous,
which the number of analyses seems to preclude, that this ratio
does not vary with the SiO,, but seems to be dependent here on
the general character of the magma from which the rocks
solidified. Grouping these roughly into two classes according
to their general characters we may say that the ratio is high in
the granito-dioritic group and low in the foyaitic.

It is, it must be confessed, somewhat surprising to find such
a connection between the ratio of the two iron oxides and the
petrographical character of the rocks. Is it indeed the fact
that there is such a difference in behavior between the two
oxides? Do they really differentiate with respect to each other,
or is the relation only apparent and due to other causes, such as
possible oxidation of the ferrous iron in the foyaitic rocks?
In the flow rocks the ratio is low and it seems possible that
their solidification at the surface may have induced oxidation.
But all the other rocks are abyssal or hypabyssal, so that such
an action would seem to be excluded, or at least equally effective
in each. We have also seen that the granito-dioritic dikes show
a uniformly higher ratio than their plutonic analogues. On the
whole we seem driven, as far as the data at hand allow us to
decide, to the conclusion that the two oxides differentiate with
respect to each other and that their ratio is in some way con-
nected with the composition of the magma.

In connection with this ratio we may note the interesting
case of Nos. XV and XIV, the tinguaite and sdlvsbergite, whose
composition is very similar, the total iron oxides being about the
same. Inthe tinguaite the high Fe,O, (ratio 0.52) has con-
ditioned the formation of aegirite, while in the sélvsbergite the
high FeO (ratio 3.31) has conditioned the formation of glau-
cophane-riebeckite as the colored mineral.

Na,O+K,0O

SiO,

Iddings* in the investigation of the relationships of rocks. Here

This ratio has been recently employed by

*IppINGs:: Jour. GEOL., Vol. III, 956, 1895, Vol. VI, 96, 189, Vol. VI, 219, 1898.

PETROGRAPHICAL PROVINCE OF ESSEX COUNTY . 469

it corresponds ina general way with the grouping already used.
In the acid rocks, from granite to akerite, the ratio is low and
fairly constant, varying only from .088 to .121. In the foyaitic
rocks from glaucophane-sélvsbergite to analcite-tinguaite, it is
much higher and also fairly constant, from .156 to .228. Inthe
basic rocks the ratio is again low, the essexite alone showing the
high ratio of .166, analogous to that of the foyaites, as was to be
expected. The ratio of the hornblende-gabbro (.112) is also
in accord with its transitional character between the diorites and
essexite.

A large number of other ratios have been examined, but
without any very significant results. The only one worth
mentions. that:of All| Oo =.He,O.,-CaO--Na,O--K,0.: Inthe
more acid rocks, from pulaskite up, this approximates closely
to unity, but below this there are some other wide variations, the
sesquioxides being deficient, except in the foyaites.

The rock series. —Without going further into details, we may
divide the rocks of Essex county into the following series as
defined by Broégger.*

The first may be called the granito-dioritic, and embraces the
granites, quartz-syenites, quartz-diorites, diorites (which are
partly monzonitic), and gabbro. These are characterized miner-
alogically by the presence of microperthite (albite and ortho-
clase) in the more acid members and plagioclase with some
alkali-feldspar in the basic, and by iron-micas (in the more acid)
and green and brown hornblendes and pyroxenes. Chemically
they show comparatively low ratios of Na,O to K,O and Na, O
ait. Oto oO. and high ratios, of, MeO to, Fe,O7,.

Torthiswis, relatedia.'sertes of dike rocks, including”, the
aplites and microgranites, quartz-syenite-porphyry, and, at the
basic end, probably a part of the diabases. These dike rocks
possess chemical and mineralogical characters similar to those
of the preceding series.

The next prominent series is the /foyaztc, embracing the
pulaskite, litchfieldite, and essexite, and characterized by the

*BROGGER: Eruptivgest. d. Kristianiageb. Vol. I, p. 169, 1894.

470 HENRY S. WASHINGTON

abundance of the albite molecule, lack of lime-soda feldspars,
and presence of nepheline, aegirite, and blue glaucophane-
riebeckite or brown barkevikite. These rocks show high Na, O:
KO: and Na, O-)K7 © :Si@; ratios and low HeOr her Ore

Related to this series are the dikes of the sdlvsbergite-
tinguaite series, and of paisanite, also possibly the camptonitic
dikes. These show chemical and mineralogical characters
analogous to those of the foyaitic series, but vary far more in
composition. i |

These four series, which are very well defined, include nearly
all the rocks examined. Among the exceptions the horn-
blende-gabbro occupies, as we have seen, a position intermediate
between the diorites and essexites, and may be reasonably
regarded as a transitional and connecting form. The flow rocks
are abnormal. In certain respects they seem to be allied with
the granito-dioritic rocks, while other characters suggest affinities
with the foyaites. The question is a difficult one to decide.
The orbicular syenites, which are present in very small amount,
are almost certainly related to the granito-dioritic series, though
lack of an analysis leaves the question uncertain. By its mineral-
ogical characters and by its ratios the Quincy granite belongs to
a foyaitic series, forming the most acid member of it, and cor-
responding to the paisanites among the dike rocks. As it belongs
to the Blue Hills Complex, quite outside our region, it will not
be discussed further.

Relations of the various types—As a preliminary to the deter-
mination of the genetic connection of the various rocks, it will
be well to obtain some idea of the relative amounts of the
different types represented. For obvious reasons it is, of course,
not possible to do this with certainty or accuracy. If we assume
that the areas shown on the geological map are dependent on
the relative volumes (which may or may not be the case) we
shall get an estimate, which, though very far from being accurate
or wholly satisfactory, may be considered provisionally to -
express the relation in a general way, and which will probably
be sufficient for our present purpose.

PETROGRAPHICAL PROVINCE OF ESSEX COUNTY 471

An examination of Mr. Sears’ map, together with a considera-
tion of my own observations, permits me to estimate, 7 @ very
rough way, the relative percentage areas given in the following
table, in which are also given the relative volumes, reduced to
percentages, calculated from these data. This estimate, it must
be observed, includes only the main area of igneous rocks,
excluding the area of sedimentaries and gneisses, etc., which
covers the western part of the county, as well as the quartz-dio-
rite area near Newburyport, since the northerly extension and
connections of this are unknown to me.

Rock Area, % Volume, %
Granite - - - 30 Cyne
Quartz-syenites - - 24 26.4
Diorites - - - 28 33.4
Foyaites - - - 2 0.6
Essexite - - - I O:2
Gabbro- - - - . I 2
Acid Dikes - - - I 0.2
Basic Dikes' - - =e 3 122
Rhyolite?—- - - 10 0.6

It will be seen that the granites and quartz-syenites constitute
nearly two thirds of the total, the diorites one third, while all
the others make up only three percent. This result is of special
interest since this region is generally regarded by petrographers
as essentially one of nepheline-syenites. They occur, it is true,
but form only a small, though important, part of the complex.

tShaler (of. czz., p. 583) estimates the area of the dikes of Cape Ann at 5 to Io
per cent. As dikes are apparently less abundant elsewhere I have reduced this con-
siderably, especially as my observations lead me to think it too high.

2As these are flow rocks their depth will be small compared to their area, and I
have therefore estimated their volume at only a tenth of that calculated on the basis
of the other rocks.

31 have recently received from Mr. Sears a large and representative collection of
the diorites of-the main western Ipswich-Danvers area. Although time is lacking for
proper microscopical and chemical study, they are evidently quite basic, and to all
appearance approximate very closely to those already described, chemically and
mineralogically.

472 HENRY S. WASHINGTON

Assuming that the figures given in the table above are
roughly true (which is quite hypothetical), it will be of interest
to calculate the composition of the magma as a whole. The
results of this calculation, which are admittedly crude and of
little reliability on account of the character of the data employed,
are as follows:

SiO; LiO,; Al, O7, He, On, He®@,) Mz @ i: Ca@t Na, Oy Ke © Ee @ rere:
GijasiaeLs0 14.5 167 An Opp aneLiw7 2.00 (2 3574. Ol O14 —OOr

The result corresponds in general with the idea of the magma
derived from examination of the analyses, though it is perhaps
somewhat higher in MgO and CaO, and hence more monzo-
nitic, than we might have expected. Of the rocks analyzed it
approaches most closely to that of the akerite (No. X), but it
shows less SiO, and alkalies, and more MgO and CaO than this.
A rock of this composition would probably be found among the
more basic akerites or more acid diorites.

Leaving this aside for the present it will be evident that the
main course of differentiation (assuming that such has taken
place), has been to form a large series of granites, quartz-syen-
ites,and-diorites, which pass into one another more or less grad-
ually through transition forms. Among these there is a quite
gradual gradation of the oxides, as will be seen on reference to
the table of analyses. A rather peculiar feature is the increase
of Al,O, in the basic members, which is quite unusual. Parallel
series from other regions analogous to this might be mentioned,
but it seems scarcely worth while to do so.

The series of granito-dioritic dikes, which correspond so
closely both mineralogically and chemically to the granolites,
must be classed as aschistic’, z. e., which are not separate differ-
entiation forms of their magmas, but only dike forms of the
partial magmas which solidified elsewhere as granolites.

The foyaitic series presents a somewhat different problem.
These rocks are evidently connected genetically with the main

*BROGGER: of. cit., Vol. I, p. 125. I am in some uncertainty in thus rendering
into English BROGGER’Ss words aschist and diaschist. The termination -ic would seem
to be better than -ous or -ose, which latter is already in use in schistose, denoting
structure.

PETROGRAPAICAL PROVINCE OF ESSEX COUNTY 473

series, bot{h on geological grounds and petrographical, such as
the transition forms between the essexite and diorites. They
represent, however, a distinctly different magma; one not only
more basic, but richer in Na,O and Al,O, and poorer in CaO,
MgO, and FeO. They arealso notable for the fact that consider-
ing their very small amount they are relatively more differen-
tiated than the main magma. This is in accordance with obser-
vations on nepheline-syenite regions elsewhere, which, it is well
known, carry not only a very great number and variety of rare
component minerals, but also show a comparatively large num-
ber of rock varieties. _

Since it has been shown that in the granito-dioritic series
Na,O tends to increase relatively to K,O as SiO, decreases, and
at the same time as it increases inversely as SiO,, it follows that
in the course of a differentiation of such a magma there should
be an enrichment of Na,O at the basic end. The rocks of the
foyaitic series may then be held to represent the further differ-
entiation products of such a basic, soda-rich portion of the main
magma, this further differentiation taking place in accordance
with the tendency of magmas rich in soda to differentiate, while
in the more acid portions the relations would remain more simple.
This explanation is essentially that of Pirsson* to account for
the phonolitic dikes of the Judith Mountains.

Lack of space forbids the full discussion of the foyaitic dike
rocks, comparing them with the main types as Brogger has done,
but the evidence goes to show that the paisanite, sdlvsbergites,
and tinguaites are probably to be regarded as diaschistic dikes,
i. e., further differentiation products of the foyaitic magma, and
not simply dike forms of this. This is analogous to the Chris-
tiania region, where Brégger? has shown that the dikes of the
grorudite-tinguaite series are diaschistic.

The differentiation probably laccolithic.—We have now to examine
the question as to where the differentiation of the Essex county
magma took place. Are the rocks, as we see them, due to

*PIRSSON: Eighteenth Ann. Rep. U. S. Geol. Surv., p. 573, 1898.

? BROGGER: of. cit, p. 127 ff.

474 HENRY S. WASHINGTON

successive injections of liquid magmas and the differentiates* of a
more deeply seated magma, only part of which was released from
the reservoir, or are they the differentiates zm set of a body of
magma which was injected in a more or less homogeneous con-
dition from below? Is the differentiation, in other words,
‘deep magmatic,” or “‘laccolithic ?’? Very thorough and care-
ful field study is necessary to decide this question, study
which it has not been possible for me to undertake. At the
same time, certain considerations seem to point to the conclusion
that the differentiation at Essex county was laccolithic, and that
the complex may possibly be regarded as a laccolith. I can
only point out very briefly the facts on which this conclusion
rests, leaving the further study and settlement of the question to
others.

Comparatively very few differentiated laccolithic masses have
been studied, but those which we know best show a basic border
and more acid interior, with, in some cases, an intermediate zone
of medium composition. Prominent examples of these are
Brandberget, in Gran;3 Carrock Fell+ in England, and the
especially beautiful and instructive ones described by Weed and
Pirsson, notably, Square Butte,’ Yogo Peak,® and Bear Paw
Peak? in Montana.

On looking at the geological map of Essex county,® it is
seen that the main granite area is to the east, extending in
large patches from Cape Ann westward,and ending in this

*I use this term as synonymous with and more convenient than “‘ differentiation
product.” It is formed analogously to the word soéz‘e.

? BROGGER: Quart. Jour. Geol. Soc., Vol. L, p. 29 ff., 1894, and Erupt. gest. d.
Christ. geb., Vol I, p. 153, 1894.

3 BROGGER: Quart. Jour. Geol. Soc., Vol. L, p. 31, 1894.

4H{ARKER: Quart. Jour. Geol. Soc., Vol. L, p. 311, 1894, and Vol. LI, p. 125,
1895.

5 WEED and Prrsson: Bull. Geol. Soc. Am., Vol. VI, p. 389, 1895.

© WEED and Pirsson: Am. Jour. Sci. Vol. L, p. 467, 1895.

7 WEED and Pirsson: Amer. Jour. Sci., Vol. I, p. 351, 1896.

8 The map here given is copied from the revised one of Mr. Sears,some omissions
being made on account of the greatly reduced scale. An attempt has been made to
show approximately the small foyaite area along the Beverly Shore.

PETKROGKAPHICAL. PROVINCE OF ESSEX COUNTY +475

fouR. GEOL., Vol. VII, No. 5 PiPAe. Vil

——-
NEW HAMPSHIRE ee :
= =
a 1-7,
42,50
Mie Dir 2 Ne Toe)
O C FEF AN
3
'
- L
; —— Z foacien i\{j g
ee I! 2
<r - \ seh
= ————— | tf 42°40
AND Oy & — == = | De 3
af
——= A 2A
E55ex P ) f #é
| is
3 i
ea “ ee
y ¢ 8 - q
MAP
GEOLOGICAL
oF /
ESSEX COUNTY, MASS. : o
{EDUCED FRON THE REVISED MAP OF a f °
‘ | a 5 rite ¥ oe
J.H.SEARS ; anes ee ag *
ETIN OF TNE ESSEX INSTITUTE, VOL. XXVIII, 1895 2 | 2 $
14 Seale of Mites Hh y B
2! IH}
LEGEND ill ace %
INGLANDE GAANIT! 7TRAHYOLITE 7 { | } q S
ARTZ—-SYGNITE. BMVSCOvITE—BIOTIT! q t 42°30
GRANITE 7 12 I ss & ae
be a | bé
RITE 9 GRANITIC ENEISS Wy |
— Ee YF ‘
aaTZ-DIORITE JoZoVSiTe aed comonar 7EZ
cnciss
eoro 1 SCMIST and SANDSTONE FS 2 y Yy e vA
nschiste MAS 8 CHUS £F& TTS
GZ
(AIT Band GS3EXITE WCANBRIOAN = 7 Wj rt
ly |
j 5
!
D
7s 70155" ase A XY

476 HENRY S. WASHINGTON

direction in a broad zone which runs north-northeast from
Beverly to Ipswich. Interspersed with the granite and surround-
ing some of the smaller areas is quartz-syenite, which is not met
with west of the granitic zone, except in two small patches.
West of the granite area, and forming also a broad zone running
north-northeast, is the main area of diorite, which curves around
to the south, forming the Salem area, and is also met with as
strips and tongues in the granite areas. West and northwest of
the diorite are found sedimentary and metamorphic rocks, of
which something will be said later. The ‘small area of foyaitic
rocks lies near Salem, south of the western parts of the granite
and quartz-syenite areas. The gabbro is only met with at the
extreme south, on the small promontory of Nahant with patches
of metamorphosed Cambrian sedimentaries. To the south near
Lynn, and north near Newburyport, are areas of rhyolite, a
small patch of which is also found at Marblehead Neck, south-
east of Salem. :

There is then a rather regular arrangement, the acid rocks
being to the east and the basic diorites surrounding them to
west and south, lying on the outside next to the nonigneous
rocks. This is suggestive of the arrangement of the rocks in
the ordinary type of differentiated laccolith.

In the ‘next’ place, according to Mr Sears: map and hus
description of the sedimentary rocks,’ we find that the dips of the
sedimentaries and metamorphosed rocks, which form the western
part of the county, are in general to the northwest or north-
northwest, z. ¢., away from the igneous area. This is also
suggestive of a laccolithic mass, and the few small areas of sedi-
mentaries metamorphosed by contact with the igneous rock,
which are met with here and there through the igneous areas,
may be considered to be remnants of the original cover. In
fact, Mr. Sears, himself, indicates the conclusion that the mass is
an anticlinal laccolith, when he says:? ‘The position of these
two metamorphosed crystalline sedimentary beds signifies that

®

tSEARS: Bull. Essex Inst., Vol. XXII, p. 1, 1890.
?SEARS: Bull: Essex Inst., Vol. XXIII, p. 15, 1891.

PELROGRAPHICAL PROVINCE OF HSSEX COUNTY _A77

they are remnants of an anticlinal fold of the Cambrian sedi-
ments, perhaps produced by the intrusion of the eruptive granite
magma from beneath them.’’*

A further fact, which is in favor of laccolithic differentiation,
is the radical difference of opinion of the two observers, Wads-
worth and Sears, who are best acquainted with the region, as to
the order of succession of the igneous rocks. Leaving the
dikes out of consideration, and adopting the nomenclature of
this paper, Wadsworth? gives it as follows, beginning with the
earliest: gabbro and diorite, quartz-syenite, nepheline-syenite,
granite, and rhyolite. Sears,3 on the other hand, gives granite,
quartz-diorite, essexite, diorite, nepheline-syenite, and quartz-sye-
nite, gabbro, rhyolite. This argument is not conclusive, since the
differences of opinion are perhaps explicable on the ground of
lack of good exposures, etc., but in the case of two good
observers, who made a careful study of the region, they are sug-
gestive of the fact that there is no ‘‘order of succession” in the
usual sense of the term, and which we would not expect to find
in the case of a differentiating laccolithic mass of magma.

Lastly, it may be mentioned that the rocks are just what we
might expect to find as the differentiates of a magma, such as
this was, when laccolithically differentiated. The transition types
which exist between the various members, and the “schlieren,”
such as those in the diorite of Marblehead, are also in favor of
this hypothesis, as is also the greater abundance of dikes in the
granites as compared with the diorites, since it seems reasonable
to suppose that many cracks formed from below would penetrate
the granite, and not the overlying diorite zone.

Several objections may readily be brought against this hypoth-
esis, among which may be mentioned, the asymmetric character
of the complex and the absence of quartz-syenite between the
granite and diorite, where we should expect to find it. The first

tA similar structure is apparently suggested by Hopss (Amer. Geol., Vol.
XXII, p. 110, 1899) for the area about Waltham, southwest of our region.

? WADSWORTH: Geol. Mag., p. 209, 1885.

3 SEARS: Bull. Essex Inst., Vol. XXVII, p. 109, 1895.

478 HENRY S. WASHINGTON

objection may be met with the fact that such asymmetric lacco-
liths are known, and are to be looked for in certain conditions of
the surrounding strata.t Further, the presence of the coastal
fault line and the Atlantic Ocean to the east is a sufficient explana-
tion for the disappearance of a large part of the mass on this side.’
The irregularity of the quartz-syenite is a more serious objection,
and is, perhaps, best explained by the admitted fact that the lac-
colith must have been of a decidedly irregular shape, owing to
the conformation of the strata into which it was intruded. It is
possible, also, that considerable faulting may have taken place.
The microscope shows that most of the rocks have been sub-
jected to pressure, such as would be consequent on crustal
movements. It must be noted that I am here using the term
laccolith in a broad sense, as Cross and Pirsson have done to
include ‘‘all thick lenticular (in this case elongated) masses which
have domed up the strata, and have over the greater part of their
area a roof of sediments’’3 (here largely disappeared through
erosion, glacial, and otherwise). The actual presence of this last
feature is not essential to the idea, since any cover may be
removed by erosion without affecting the original character of
the mass.

It may also be remarked that, as far as can be seen, the
course of differentiation would be the same whether, as in a true
laccolith, the intruded magma bulged up the overlying strata, or
entered an arch space formed otherwise.+ From the petrological
standpoint the mechanics of the process are of secondary impor-
tance. The chief point of my suggestion is that the differentia-
tion was laccolithic and of a mass zx stfu, and not deep magmatic,
and the rocks the results of successive intrusions. In the one

™W. Cross: Fourteenth Ann. Rep. U. S. G. S., p. 236 ff, 1895. | PIRSSON:
Eighteenth Ann. Rep. U.S. G.S., pp. 555, 581, 1898.

?Mr. SEARS (Bull. Essex Inst., Vol. XXII, p. 16, 1890) notes the occurrence of
Cambrian limestone at Jeffrey’s Ledge, in the Atlantic Ocean, about twenty miles east
of Cape Ann.

3 PIRSSON: @oc. cit., p. 581.

4For an example of the latter cf. WATTS: Rep. Brit. Assoc. 1886, p.670 and Proc.
Geol. Assoc., 1894, p. 341.

PEPROGRAPHICGAL PROVINCE OFVESSEX COUNTY. 479

case the rocks are all genetically connected, in the other pos-
sibly not.

Conclusion and summary.— My view, then, of the structure of
the complex and genetic relationships of the rocks of Essex
county is as follows. The igneous area represents possibly a
section through an elongated, irregular, anticlinal, laccolithic
mass, with a N. NN. E.—S.S.W. trend, intruded into already dis-
turbed Cambrian strata. The plutonic igneous rocks represent
the products of a laccolithic differentiation in this magma, and
not successive intrusions. The magma was rather acid, rich in
alkalies and ferrous iron, and possibly did not differ materially
from the calculated composition given on page 472. This course
of differentiation produced primarily and most abundantly the
granites, quartz-syenites, and diorites, with their corresponding
aschistic dikes as Machschube. A secondary local differentiation
of the more basic differentiates of this process gave rise to the
foyaites and essexites, while the rocks of the paisanite-tinguaite
series are probably diaschistic dike forms of these. At a much
later period, after erosion had removed much of the covering of
the granolites, the rhyolites were erupted, from some unknown
vents. Lastly, here, as so often elsewhere, the diabases were
injected into the much cracked complex.

Comparison with other regions—So much space has been
devoted to the previous discussion that a few words must suffice
for this topic. From the references to the Christiania region
throughout the paper and comparison of the analyses, the general
correspondence between the two is evident. There are differ-_
ences in details, such as the more acid and somewhat less soda-
rich character of the Essex county rocks, abundance of diorites
here and of laurvikites and laurdalites in Norway, etc. But it may
be said that the general course of differentiation was essentially
much the same in both, a fact which supports the theory that
the variations of rocks are largely subject to physico-chemical
laws, and are not fortuitous and due to the composition of the
surrounding rocks and other external circumstances, as Johnston-
Lavis and Becker would have us believe.

480 HENRY S. WASHINGTON

A comparison could also be instituted with the other igneous
rocks of the New England region, going to show that great
similarities exist. But our knowledge of most of the other igne-
ous regions of New England and Canada is so scanty that the
time does not seem ripe for this. It will be sufficient to note
that some of the rocks of Essex county show great analogies
with, for instance, those of Litchfield, Maine, and Red Hill and
Mt. Ascutney, New Hampshire. Farther west, in the Adiron-
dacks and near Montreal, the character of the magma seems to
be different, as has been pointed out recently by Cushing,’
though there are many resemblances.

HEnryY S. WASHINGTON.

tH. P. CusHING: Bull, Geol. Soc. Amer., Vol. X, p. 191, 1899.

PETROGRAPHICAL PROVINCE OF ESSEX COUNTY 481
TABLE -1I.
I Il Ill IV Vv VI Vil VIII 1X xX XI XII
SiO, 77.6% 77-14 76.49 73.93 71.40 70.64 68.88 63.36 67.35 66.60 64.28 63.71
AO? ; 0.25 0.29 | trace 0.18 ae 0.90 0.19 | trace 0.60 0.76 0.50 | trace
AO Spee Numa e || Mbeewul) ates on | teas sce san os vane Sieve Ro bere coe uae Bie?
NO Saageemrnee II.94 12,24 11.89 12.29 14.76 15.34 14.77 16.58 15.05 15.05 15.97 18.30
Fe,0,. 0.55 0.29 1,16 2.91 1.68 1.83 0.64 0.90 I.23 I.07 2.91 2.08
FeO... 0.87 1.04 1.56 5S 0.72 I.I0 4.64 3.24 4.76 4.42 3.18 2.52
Min OMe eee ae. trace trace trace trace trace trace trace trace 0.05 | trace trace trace
IMPOR ies «sires trace 0.06 | trace 0.04 0.55 0.52 0.37 0.45 0.03 0.36 0.03 0.09
(CHO ere somes 0.31 0.35 0.14 0.31 0.10 1.24 1.74 1.85 0.55 2.21 0.85 1.18
Ba Oeeaece cis cevell aces: Aree Reese none mee ada aciscerers sree ieee none none ele
INGO SRE 3.80 4.64 4.03 4.66 4.79 5.23 3.83 3.907 4.42 4.03 7.28 6.39
IX6(O) aera aaa 4.98 4:47 5.00 4.63 5.16 3-55 4:07 5-27 6.08 5-42 5.07 6.21
lal Oh Gure) amen trace trace 0.12 nae Reon 0.14 0.06 0.18 0.16 Bree'l|” kaso 0,09
Hie © (ignit), .-.- 0.23 0.14 0.38 0.41 1.46 0.38 0.24 0.17 0.17 0.41 0.20 0.17
EN) ee apse a austen ct fy vaveere ae (ld ite. chose e[hiw wroey ee scaantt istoveree® sige Ncevstecea Mb U dice ssssb || Ptineeee 0,08 fe
100.54 | 100,66 | 100.77 | 100.91 | 100,62 | 100.87 | 100.33 | 100.97 | 100.45 | 100.33 | 100.33 | 100.74
Sint (Giisecescens 2.618 650 | 2.642 2.632 2.6096 2.690 | 2,612 2.703 2.686
ati. To2C: TIC wm lesen ney On| | ware Oy 17°C, r7°C. |ev222@3 ||) 127.
TABLE I— Continued.
XIII XIV XV XVI OVI | VT |) XI XX XXI | XXII | XXIII} XXIV
S103. 63.09 61.05 60,05 59.31 58.77 56.75 51.82 47.12 46.99 46.59 45-32 43.73
PUO RR Sees sacs 0.45 0.34 O.1I 0.32 0.31 0.30 2.15 3.27 2.92 1.41 1.94 4.23
ZrO Ree etc 0.06 sapiet la @sacscti| y pee eas O.II sated tee | wecieces eee |S oecved || wanes ame
WAM OF tore cosacege 18.50 18.81 19.97 22.50 22.04 20.69 17.06 14.43 17.94 17-55 18.99 20.17
Fe,0, 2.90 2.02 4.32 1.93 1.54 3.52 1.07 3533 2.56 1.68 3.78 4.32
FeO. 1.36 3.06 1.04 1.40 1.04 0.59 8.60 ay At 7.50 10.46 9-78 6.93
MnO trace trace 0.79 | trace trace trace trace rire heretic Seidl By cdoe |) come
MgO 0.16 0.42 0.23 0.17 0.19 OIL 4.87 | 6.05 3.22 7.76 4.68 3-01
(CAO RGEaSrRneaee I,00 1.30 0.91 0.46 0.74 0.37 8.59 9.63 7.85 10.64 9.19 10.99
iBaO.... Saheter none seies ee none mone) |) 2-0 aes none ee ferig Meee seeatevens
INa,O .. 7.25 6.56 7.69 7.98 9.62 Te Ay 3.44 2.58 6.35 3.31 3.78 2.42
IK \ OBrien 5.23 6.02 3.24 4.08 4.89 2.90 1.77. T,rr 2.62 0.72 2,12 1.45
B@(r10%);. .... 0.21 are 0.15 0.15 0,07 0,04 O.II Ope || ogee 0,10 0,09 0,08
BO(ignit).....; 0.62 0.78 | 1.26 Te12 0,90 3.28 0,20 0.34 0.65 0.07 0.31 1,02
DEO soa sccrcnes ee Cl —or20u | mee oo |r Cl=o0,28 Bee ne OFO4 ul |eraee. neu) emer 0.15
100.83 | 100.36 | 100,04 99-42 | 100.82 | 100,18 | 100.58 99.85 99.60 | 100,29 99.98 99.40
Bist oes efvats 2.055 2.708 2.599 2.596 2.474 §3.072 2.919 3.047 2.075 3.058
z2°C, Bes T2C, |) 1° e2ue. 12° Toca err Cu | petra Oon| ger reG.
Granite. Rockport. XIII. Pulaskite. Salem Neck.
Aplite (mean). Bass Rocks. XIV. Solvsbergite. Coney Island.
Paisanite. Magnolia. XV. Tinguaite. Gale’s Point. (Eakle.)
Granite. Quincy. (Blue Hills.) XVI. Foyaite. Great Haste Island,
Keratophyr, Marblehead Neck, XVII. Foyaite. Salem Neck,
Rhyolite. Marblehead Neck. XVIII. Tinguaite. Pickard’s Point,
Quartz-syenite-porphyry. Squam Light. XIX. Diorite. Marblehead.
Nordmarkite. Wolf Hill. XX, Diabase. Rockport.
Enclosure in Granite. Rockport. XXI. Essexite. Salem Neck.
Akerite. Gloucester. XXII. ‘‘ Camptonite.”” Salem Neck,
Sdlvsbergite. Andrew’s Point, XXIII. Hornblende Gabbro, Salem Neck.
Pulaskite. Salem Neck. XXIV. Gabbro. Nahant.

482

HENRY S. WASHINGTON

TABLE II.
Ta Ila IIIa IVa Va Via Vila | VIIla IXa Xa Xla XIla
SiO,. 1.204 1.286 1.275 1.232 I.190 1.177 1.148 1.139 1.123 I.1I0 I.O7I 1.062
INOS Geonde .II7 .120 s1L7 .120 +145 «150 +145 .163 .148 148 +156 179
Hex Osea +003 .OOI 1007 .018 sO1L -O1L .004 .006 .008 .007 .018 013
FeO .O12 .O14 .022 .022 -O10 -O14 .064 -045 .066 .061 2044 -035
WIEO) Sone cs6 dee .002 a .OOT .O14 013 009 .OIL -OOT -009 oor .002
CaO +005 .006 .002 006 .002 .022 +031 033 .O10 039 .O15, 2021
Nias Osea .06O1 .075 .065 :075 .077 .084 .062 .064 -O71 20605 sL7, .103
KS ORGS: create share -053 .048 1053 +049 -055 -038 1053 .050 .065 .058 -054 .066
EO) Setsnas: l I.15 1.56 I.23 1.53 I.40 2.21 1.17 1.14 1.09 I,12 2.17 1.7L
KOR eas J
1s OP Ba eicetce
———_ 4.00 I4,00 3.14 1.22 0.91 1,28 16,00 7.50 8.25 8.71 2.44 2.69
IREAOW closure
a Ke ae
aE eS .088 096 .092 .IOL III 104 2100 +105 .I2I «IIL +156 +159
ROA rae na
NavOMaae
= -047 -059 sO51 .061 .065 -O71 2054 .057 .063 +059 -IIO 2097
SiOPaasace
TABLE II.— Continued.
XIIIa ; XIVa XVa | XVIa | XVIla |XVIIla| XIXa } XXa | XXla | XXIla|XXIIa} XX1Va
SiO siteccniece 1.052 1.018 1.001 0.989 0.980 0.946 0.864 0.785 0.783 0.777 0.766 0.729
ANZOR peecomene 181 183 .196 .221 .222 203 167 «142 -176 .172 186 -198
Fe,O; .018 -013 .027 .O12 .o10 -022 -O12 .02T .o16 -O1L .023 -027
HeOim es .O14 043 .O14 01g -O14 .008 +120 Sr03) +105 anit .136 .097
NRO Mine gato 004 .OII 2005 +004 +005 +003 .122 «151 .080 -194 .117 -098
CaO .018 .023 016 008 013 .007 +153 172 .140 .I90 164 .196
NERO Hegsaeooce .I17 «158 -123 -129 +155 185 056 042 .102 1053 -061 -039
K,0 Seri 1050 004 034 -043 -052 -031 .O1Q ,O12 .029 -008 .023 .O15
NEVO} Es ocuoae
o5 2.09 2.47 3.62 3.00 2.98 5.07 2.95 3.50 3.64 6.63 2.65 2.60
ReOpe aay
——- 0.78 3-31 0.52 1.58 1.40 0.37 10,00 7-74 6.57 13.19 5.67 3.96
IQOAOR aeanaoe s
K,0:.
Nene 164 218 157 174 -211 228 086 .069 166 .078 «112 .074
We
Nias Om ee seic
ae III “155 -123 +130 +157 +195 .065 2053 2130 .068 .080 -053
Hikageeodd so

WePRECULIAR DEVONIAN DEPOSIT IN NORTHEAS?-
ERN ILLINOIS

THE village of Elmhurst is in the eastern edge of DuPage
county, Illinois, on the Chicago and Northwestern Railway, fif-
teen miles west of the Wells Street Station in Chicago. On the
north side of the railway track, about one mile west of the
station, are the Elmhurst quarries. The rock quarried, which
is the buff or bluish Niagara dolomite of northeastern Illinois
and Wisconsin, has been excavated to a depth of about thirty
feet,

At this locality the limestone is much fractured by two sets
of gentle folds whose axes have a general north-west south-east
and north-east south-west direction, joint cracks being well
developed. Some of these cracks are several inches in width,
and are in general filled with a black or blue clay. At one
point, in the south-east face of the quarry, about eighteen feet
below the glaciated surface of the rock, one of these joints is
somewhat enlarged to form a narrow triangular opening about
six inches in width at the base and about sixteen inches in
height. This opening, instead of being filled with clay, as are
all the other larger joints in the quarry, is filled with a breccia
composed of angular fragments of the adjacent limestone,
imbedded in a dark brown arenaceous matrix. This matrix is
abundantly fossiliferous, containing immense numbers of fish
teeth, and a smaller number of Lzngwla shells and other brachio-
pods, which indicate its Devonian age.

The situation of this most peculiar occurrence of Devonian fos-
sils, deeply buried in the Niagara limestone, is shown in the
accompanying illustrations. Figure 1 is a near view, showing
the Devonian material filling the triangular opening to the left
of the hammer. Figure 2 was taken from a greater distance, in
order to show the position of the opening in the face of the

483

484 STUART WELLER

quarry about eighteen feet below the surface. The species of
fossils recognized are as follows: ;
Fish teeth.
Ptyctodus calceolus N and W.

Diplodus priscus Eastman n. sp.
Dipledus striatus Eastman n. sp.

Brachiopods.
Lingula ligea H.?
Orbiculoidea newberryt H.?
Ambocoelia umbonata Con.

The most abundant species is Ptyctodus calceolus, whose tri-
tors are present literally by the hundreds. This species is char-
acteristic of the middle and upper Devonian faunas of the inte-

Inte ate

PECULIAR DEVONIAN DEPOSIT IN IELINOIS 485

rior of North America. It has been recorded? from Canada,
Milwaukee, Wis., western Illinois, Missouri, lowa,and Manitoba.
The Elmhurst specimens are generally smaller than those usually
found in Iowa and other localities, but there seems to be no essen-
tial difference in form. The remaining fish teeth are two new

FiG. 2:

species of the genus Dzplodus which have been described by Dr.
Cakes Hastman,

Among the brachiopods, the one identified as Lingwla ligea is
the most abundant. It was originally described from the Ham-
ilton in New York, but it also occurs in the Upper Devonian of
the same state and has been recorded from the Devonian in

* Iowa Geol. Surv., 1898, Vol. VII, p. 114; Am. Nat., 1898, Vol. XXXII, p. 476.

486 STUART WELLER

Nevada. Ambocoeliaumbonata,a single individual of which has been
observed, is a common Hamilton species in New York, although
a variety of the same species also occurs in the Upper Devonian.
Orbiculoidea newberryt, also represented by a single observed
specimen, has been recognized only in the Waverly series of
Ohio, near the base of the Carboniferous.

The presence of Ptyctodus is certainly indicative of the Devo-
nian age of the fauna, but Dzplodus has previously been recog-
nized only in Carboniferous strata, and the presence of two
species of this genus with the Waverly species of Orbiculoidea
would seem to indicate a very late Devonian age.

The presence of a fauna of this age in such a situation, is of
extreme interest. Thenearest point where Devonian strata form
the surface rock is probably in northwestern Indiana, but that
region is so heavily drift covered, and has been so. little studied,
that the exact distance from Elmhurst to the nearest Devonian
strata in that direction cannot be determined with accuracy.
Furthermore, the Devonian strata known in northern Indiana,
are the black shales, and do not contain a fauna with Ptyctodus.
The nearest actual outcrop of Devonian is at Milwaukee, Wis.,
eighty miles north of Elmhurst; and the nearest outcrop to the
west is near Rock Island, Ill., one hundred and thirty miles
away. At both of these localities Ptyctodus calceolus occurs, but
the strata are believed to be somewhat older than the material
from Elmhurst.

The presence of this Upper Devonian fauna at Elmhurst, bur-
ied as it is deep down in the Niagara limestone, indicates with
certainty that during the greater part of Devonian time, the
region now known as northern Illinois was above sea level. It
was part of what was probably a large land surface, stretching from
the Wisconsin land on the north to the Ozark land of Missouri
on the south. The waters which collected upon this land sur-
face in part percolated through the underlying rock strata and by
solution increased the size of many joint cracks. Ata later per-
iod, near the close of the Devonian, when the sea again occupied
the region, sand was sifted down into these open joints, and with

PECULIAR DEVONIAN DEPOSITAN JELINOTS 487

it the teeth of fishes which inhabited the sea thereabout. It is
perhaps possible that the opening which has in recent time been
uncovered at Elmhurst, was during this late Devonian time large
enough for the entrance of some of these fishes, and that they
sought this opening for shelter, much as fishes at the present time
enter similar openings.

The manner of communication between this opening and the
surface is not clearly shown in-the field, but arenaceous material

FIG. 3.

with fragments of fish teeth is seen clinging to the quarry face
to the left of and above the opening. This material may be
rather indistinctly seen in Fig. 1, being represented by the dark
blotches upon the lighter colored rock in the position indicated.
This rock face is one side of a joint whose opposite side has been
removed, through which there may have been communication
between the buried opening and the sea bottom above. The

488 SROART MVE EEE Ke

Devonian material is not continuous forany great distance back
from the quarry face, as will be seen in Fig. 3, this figure being
a view taken nearly at right angles to that shown in Fig. 1,
after the rock to the right of the opening against which the
hammer leans in Fig. 1, has been removed. The Devonian mate-
rialin the figure is the darker rock above and to theright of the
hat, the line of demarcation between it and the limestone above
being sharply defined ; it is seen to thin out rapidly back from
the quarry face.

At the base of the triangular opening, between the two beds
of limestone that come in contact at that point, the Devonian
“material extends both to the right and to the left for several feet,
forming a bed an inch or two in thickness between the two lime-
stone beds. This bed has every appearance of having been depos-
ited upon the lower limestone bed before the upper one was
laid down, but in reality it was deposited at a much later date in
a cavity which existed there near the close of Devonian time.

The sort of unconformity presented by this occurrence of
Devonian sediments deeply buried in the Niagara limestone is
peculiar. No description of any similar occurrence has been
observed in the literature, and it may be designated by the name

subterranean unconformity.
STUART WELLER.
THE UNIVERSITY OF CHICAGO.

DESCRIPTIONS -OR” NEW (SPECIES “OF DIPLODUS
TEETH. FROM THE DEVONIAN OF NORTHEAST-
FERN ILLINOIS

ISOLATED tricuspid teeth with a minute median denticle, sim-
ilar to those of the Carboniferous and Permian genus Pleuracan-
thus, are provisionally grouped under the name of Dzplodus, and
it has been customary to distinguish the so-called Diplodont
and Cladodont types of Elasmobranch dentition according to
the relative sizes of the median and lateral cusps. But since the
discovery of Chlamydoselache in recent seas and the remarkable
Pleuropterygi from the Cleveland Shale (Upper Devonian), it
appears that the above types of dentition were common to sev-
eral groups of primitive sharks, thus vitiating all generalizations
based on the distribution of detached teeth. That species
founded on such variable and fragmentary remains can have
only a provisional value, pending the discovery of other parts of
the skeleton, is further emphasized in the case of some Pleuracanth
fishes, which have several forms of ‘‘ Diplodus”’ teeth occurring
in different parts of one and the same mouth.

As will be pointed out in the following, there are forms of
Phoebodus teeth intermediate between Dzplodus and Cladodus.
This is interesting on account of the close parallelism displayed
by teeth adapted for piercing among more or less widely sepa-
rated groups, but as for throwing light on the interrelationships
of these ““genera”’ is wholly without significance. ‘The earliest
and most primitive forms of piercing teeth are typified by Profo-
dus and Dolodus from the Lower Devonian of Campbellton,
New Brunswick. Cladodus is first met with in the Corniferous
limestone of Ohio, and the two new Lzplodus species described
below are the oldest known representatives of that genus. Mr.
Stuart Weller, who discovered the material and kindly invited
its description, regards the horizon as Uppermost Devonian.
The locality is near Elmhurst, Illinois.

489

490 C. Rk. EASTMAN

Diplodus priscus sp. nov. (Pl. VII, Figs. 1, 2)

Teeth minute; the two principal cusps of dental crown divergent and
slightly inclined backward, robust, conical, round in section, without lateral
carinae; coronal surface marked with relatively few, prominent, slightly
curved striae extending from the base nearly to the extremities on the anterior
face, but shorter and usually fainter on the posterior face. Median denticle
slender, sometimes much reduced, or in one specimen apparently wanting
altogether. Anterior border of root slightly produced downward ; lower surface
concave, elliptical in outline ; posterior button present.

About a dozen examples (chiefly fragmentary) of this spe-
cies were obtained by Mr. Weller, the largest of which has a
total height of 8mm. One fragment, consisting of the root
only, has an elliptical, concave base, with axes measuring 5 mm
and 7mm; a similar but smaller root has axes of only 2mm
and 3mm respectively. Each of the cones shown in Fig. 2 has
eight vertical striae on the anterior face, but if any were present
on the posterior face, they occurred higher up than on the part
preserved. The length of the median denticle is conjectural, as
the tip is missing from all specimens. The intermediate space
is occupied by a groove in the tooth shown in Fig. 2, and to all
appearances no denticle was present here. This, of course, must
be looked upon as an exceptional variation.

Diplodus striatus sp. nov. (Pl. VII, Figs. 3, 4)

Of this species only a few fragments were obtained by Mr.
Weller, the largest and most perfect being shown in the accom-
panying figures. It attains apparently about twice the size of
the preceding form, and is readily distinguished by its finer stri-
ation, shallower root, and somewhat compressed section of its
principal cones. The striae on the anterior face all curve uni-
formly in a spiral direction (Fig. 4, left-hand figure), but on the
posterior face the tendency is to curve outward on either side of
the median line to the lateral margin of the cones, where they
terminate, exactly as in some species of Cladodus (e. g., C. striata-
tus Ag.). This condition is partially indicated in the right-hand
illustration of Fig. 4, but other specimens show it more dis-
tinctly. One or two fragmentary cones have the striae less

NEW SPECIES OF DIPLODUS LEETLH 491

prominent and less numerous on the posterior face, and near
the base they may become obsolete altogether. None of the
specimens show the full length of the median denticle, but it
was apparently long and slender. Further material will be
required before the characters of this species can be adequately
defined.

Phoebodus politus Newberry (Pl. VII, Fig. 5)

The two new species of Diplodus described above differ from
most Pleuracanth teeth in an important character which they share
in common with Cladodont dentition, and that is the striation of
the coronal surface. The concave under surface of the root,
peculiar projection of the front margin shown in Figs. I, 2, and 5,
together with the posterior “button,” are features quite as char-
acteristic of Phoebodus as of the two species of Diplodus just con-
sidered. As already stated, the form of teeth exhibited by
Phoebodus is intermediate between Cladodus and Diplodus. Start-
ing with the latter genus, the transition to Phoebodus is accom-
plished by imagining the median denticle to increase in size
until it equals the lateral cones. Further increment in size of
the median cone, or reduction of the lateral cusps, which
amounts to the same thing, transforms the tooth into Cladodus.
It is noteworthy that in Cladodus, when several lateral denticles
are present, the outermost are almost invariably the strongest,
and the smaller ones would thus correspond to the intermediate
denticles of Phoebodus.

Phoebodus politus and other Devonian species have the inter-
mediate denticles well developed, as shown in Fig. 5, but in an
unpublished’ species discovered by Professor W. C. Knight in the
Permian of Nebraska, and also in the Triassic P. bvodiet, only the
three principal cones are present. While the coronal surface is
striated in the earlier species of Phoebodus, it later becomes
smooth, and the same observation holds true of Dzplodus. All
three genera under consideration appear to have had teeth

*The original specimen is listed as ‘‘ Diplodus sp. nov.” in Professor Knight’s
article on The Nebraska Permian in the last number of this JOURNAL (pp. 372-374).

PLATE Will

jour. GEOL., Vol Vi sNows

NEW SPECTES OF DIPLODUS TEETH 493

complicated in one way or another in the beginning, eventually
becoming more simplified. But, although mutual resemblances
and even intergradations exist, these all seem to be due to paral-
lelism of adaptive modifications.

C. R. Eastman.

MUSEUM OF COMPARATIVE ZOOLOGY,
Cambridge, Mass.

EXPLANATIONS OF FIGURES.

Fic. 1,2. Dzplodus priscus sp. nov. Anterior face.

Fic. 3. Diplodus striatus sp. nov. Anterior face.

Fic. 4. Diplodus striatus sp. nov. Anterior and posterior views of a large
detached cone, apparently belonging to same species as Fig. 3. Originals of Figs.
1-4 from Upper Devonian, near Elmhurst, Ill.

Fic. 5. Phoebodus politus Newb. Anterior face. Cleveland Shale, Lorain
county, Ohio. Original in Museum of Comparative Zodlogy, Cambridge, Mass.

All figures enlarged five times the natural size.

DIPTERUS IN DHE AMERICAN), MIDDEE, DEVONDAIN

Last summer, while engaged in field work in Muscatine
county, lowa, the writer found a tooth of Dipterus calvini East-
man in the Cedar Valley limestone at Fairport, on the north
bank of the Mississippi. It belonged to a horizon some eight
or ten feet below the highest ledges of this limestone exposed

Fic. 1.—A tooth of Dipterus, sp., from the base of the Cedar Valley limestone,
near Buffalo, lowa, natural size.

in the county. A few feet below these ledges there are seen
two black layers of porous bituminous rock.*

This horizon is characterized by a fauna more rich in lamelli-
branchs and gasteropods than that of the ledges below. There
is also to be found one or two species of Cranaena and a form
of Strophaeodonta demissa with coarser costae than usual. This

*These ledges have been called the Straparollus ledges. See Iowa Geol. Surv.,
Viol EXe PIV aL:

494

DIPTERUS IN THE AMERICAN MIDDLE DEVONIAN 495

fauna comes in above the ledges from which Owen collected
fossils that he referred to the Chemung (‘ Spirifer euruteines,”’
CEG);

Lately I have found another somewhat more strongly tuber-
culated tooth of Dipterus, (see Fig. 1) near Buffalo, lowa, at a level
about 25 feet lower down in the same limestone. The ledge from
which this tooth came, contains S¢trzatopora rugosa and Megisto-
crinus latus. It is directly under the ledges in which Spirifer
parryanus first appears. It has yielded teeth of Ptychtodus and
fragments of Dinichthys pustulosus. Some coral-bearing ledges,
full of fossils, he four or five feet above it.* The ledge belongs
to the Hamilton as described by Worthen in Rock Island county,
Illinois, on the opposite side of the Mississippi, and comes in
some fifteen or twenty feet above its base.

While this fish is reported from the Lower Devonian in
Europe and Great Britain, it has not before this, I believe, been
observed as low down as the Middle Devonian in America, to
which age American geologists have referred the fauna of this
limestone. .

J. A. UDDEN.

2Megistocrinus bed. Iowa Geol. Surv., Vol. LX, Pl. VI.

STUDIES FOR STUDENTS

A CENTURY OR PROGRESS IN, PALE ONDOLOEN

THE presence of fossils in the rocks was observed by the
ancient priests of Egypt, by the Brahmans of India, and by many
other ancient peoples. In some cases the bones of gigantic
mammals, such as the mammoth and mastodon, were observed,
and, being considered as human bones, they gave origin to many
of the beliefs inthe existence of races of giants. The Greeks
and Romans also observed fossil shells, bones, and plants, and
some of their philosophers speculated as to their origin, although
little or no progress was made in their study. Some of these
men believed that the shells found preserved in strata far inland
were really the shells of once living animals, while others, with
Theophrastus, ‘‘supposed them to be produced by a certain
plastic virtue latent in our earth.”

It was not until the early part of the sixteenth century that
geologic phenomena began to attract the attention of the Chris-
tian nations. At that period an animated controversy sprang up
in Italy concerning the true nature and origin of marine shells
and other fossils found abundantly in the strata of the penin-
sula. In the year 1517 extensive excavations were made in
Verona, which brought to light a multitude of curious petrifac-
tions, and furnished matter for speculation to different authors.
Among these was Fracastoro, who declared ‘that fossil shells
had all belonged to living animals, which had formerly lived and
multiplied where their exuvie are now found.’”’ He exposed the
absurdity of having recourse to the plastic force of Theophrastus,
which had power to fashion stones into organic forms, and also
demonstrated the futility of attributing the situation of the shells
in question to the Mosaic deluge, a theory that was obstinately
defended by some. Fracastoro, however, had but few com-
panions in his clear and philosophical views, and for nearly

496

AjCGENE ORY OF PROGRESS IN PALEONTOLOGY 497

three centuries two simple and preliminary questions were
vigorously discussed— (1) whether fossil remains ever belonged
to living creatures, and (2) whether, if this be admitted, all the
phenomena could not be explained by the deluge of Noah.

Throughout all this long controversy regarding the nature
and origin of fossils, little was done in the way of description of
fossil forms; but with the reformation of the system of nomen-
clature by the introduction of the binomial system, instituted by
Linneus during the latter half of the eighteenth century, the
way was opened for amore accurate description of fossils than
had been practicable previously. Linneus himself described
and named some species of Silurian fossils from Sweden, among
which may be mentioned the well known and widely distributed
Atrypa reticularis and Halysites catenulatus, although the genera in
which these species are now placed are of later date.

The real scientific study of fossils may be said to have begun
with about the opening of the present century. William Smith
(1790), in England, had recognized the value of the fossil con-
tents of the rocks in tracing the strata over extended areas, but
he did not devote his time to the description and naming of the
fossils which he found. At about this same time rich stores of
beautifully preserved fossils were discovered in the immediate
neighborhood of Paris. The labors of Cuvier and Brougniart
upon the vertebrates, and of Lamarck upon the fossil shells of
this area, constitute some of the earliest really scientific investi-
gations of fossil organisms. In fact, it may be said that Cuvier
laid the foundation of the science of paleontology, when in 1797
he called attention to the fact that elephant bones discovered in
the Paris basin were different from the bones of living species,
and thus drew a distinction between living and extinct animals
as implying present and past groups of living organisms.

Many of the works on paleontology published in the early
part of the present century exhibited little or no attempt at
classification of the materials described. The classic work of
James Sowerby, entitled ‘ Mineral Conchology,” which was pub-
lished in seven volumes, the first of which bears the date 1812

498 STUDIES POR STUDENTS

on the title-page, and the sixth 1829, a work in which very many
of the species of British fossils were originally described, may be
taken as a type of this group of works. In the arrangement of
the matter included in these volumes no attempt is made at
classification, either zodlogically or according to the geologic
horizons in which the fossils were found. It is simply a paleon-
tologic scrapbook, as it were, of descriptions and illustrations of
fossil species. One plate, with its accompanying descriptions,
may be devoted to Tertiary gastropods, the next to Paleozoic
brachiopods, a third to Cretaceous ammonites, a fourth to Ter-
tiary gastropods again, and so on, the total number of plates in
the whole work being 648.

Following the early period in which there was to a great
extent an absence of classification, the classification of fossils
gradually developed along two distinct lines. On the one hand,
with the increase of knowledge and with the progress in taxon-
omy of living organisms, the zodlogical classification of fossils
made rapid strides, and many orders, families and genera founded
wholly upon fossil forms were established, and were fitted into
the scheme of classification of all organisms, making it far more
complete than it could ever have been made from the study of
living organisms alone. On the other hand, there grew up a clas-
sification of fossils into faunas, so that a whole series of extinct
faunas, from the earliest Paleozoic time to the recent, were recog-
nized. It also gradually came to be established that the sequence
in time of extinct faunas, in their larger characteristics, was the
same for all parts of the world where fossils were found.

For many years these two systems of classification of fos-
sils went forward hand in hand, but with the development of
the science the two paths along which progress was being
made became more and more divergent, until at the present
time the two divisions of the subject have become fully differ-
entiated.

It is of interest to trace the differentiation of these two lines
of progress in the life work of such a paleontologist as the late
James Hall, whose career extended over more than half a century.

AYCENTURY OF PROGRESS IN PALEONTOLOGY: ‘499

In the earlier volumes of the paleontology of New York, the
faunal classification of fossils is predominant. Many new species
and genera are described as members of the faunas under discus-
sion, there being no elaborate investigations into the natural tax-
onomic grouping of organisms. In volume four of the work we
begin to see the deviation of the line of investigation toward the
biologic side, the faunal grouping being made subordinate to the
taxonomic. This same subordination is seen in volumes five, six,
and seven, while in volume eight we find the faunal classification
entirely displaced, and the whole volume devoted to the treat-
ment of the genera of Paleozoic brachiopods. We have, there-
fore, inthis series of volumes an exhibition of the development of
the science asillustrated by the life work of oneman, from the fau-
nal classification in 1847, through the mixed faunal and biologic,
to the purely biologic classification in 1894.

This differentiation of the science, which has become nearly
accomplished at the present time, is well exhibited in the charac-
ter of the paleontologic monographs which have been published
during the past decade or less. On the one hand such works as
Wachsmuth and Springer’s monograph of the ‘‘Crinoidea Came-
rata,’ a work which is strictly biologic in its treatment of this
extinct order, is an illustration of one division of the subject, and
on the other hand may be mentioned Walcott’s ‘‘ Fauna of the
Olenellus Zone,” where the biologic treatment of the fossils is
made entirely subordinate to their faunal associations.

While these two branches of paleontologic science have been
differentiating, the older method of investigation has by no means
disappeared, and during this whole century of progress there
have been appearing constantly contributions to paleontology of
the ‘‘scrapbook”’ order. Among the more recent of these made
upona large scale may be mentioned the series of bulletins which
have been issued from the Illinois State Museum of Natural His-
tory during the past decade. In these contributions some
hundreds of species have been described, belonging to various
classes and orders of organisms and from various geologic hori-
zons, but they have contributed little or nothing either to the

500 STUDIES FOR STUDENTS

taxonomy of the subject or to the faunal relationships of the
fossils described. Such work, however, is valuable even today in
so far as it is accurately done, because it relieves the investigator
in the more special lines of research from a vast amount of
labor. Every species of fossil must have a name as a sort of
handle by which it may be manipulated, but with the more spe-
cial workers in the subject, the description of species and the
giving of names is but a means to an end, the discovery of new
species not being the ultimate result sought after.

The biologic division of paleontology consists of the study
of the structure and organization of individuals, of their ontoge-
netic development, of the relationship pf species to species and
of genera to genera, and of their phylogeny, all with the ultimate
end of establishing as nearly as possible a natural classification of
all organisms. A large proportion of all the work being done
today among fossil vertebrates comes into this category. Among
the invertebrates much work of a high order is also being
accomplished. The recent contributions by Beecher upon the
structure, ontogeny, and classification of trilobites and of brach-
iopods may be mentioned, also the contributions by Hyatt and
others upon the cephalopods.

The faunal study of fossils is intimately connected with geol-
ogy, in fact no history of the earth, from the period beginning
with Cambrian time, can be made complete when the life history
is excluded, and for this reason this faunal study of fossils is
coming to be called paleontologic geology. Instead of taking
a single species or any taxonomic group as the unit of study, as
is done by the biologist, organic societies, those organisms which
lived in a single locality under similar environment during a lim-
ited period of time, are the subjects of investigation. The fossil
societies or faunas are dissected into their various elements, their
relation to the environment in which they existed are studied,
their relations to neighboring societies or faunas, both in time
and space, and their migrations are the subjects of investigation.
The study is a history of organisms in its broadest sense, and it
is just as truly an historical study as is the study of human his-

A\CENI ORY OF PROGRESS IN PALEONTOLOGY 5Ol

tory. In fact many parallels may be drawn between this history
of faunas and the history of the races of men.

Those organisms which are preserved in the sedimentary
rocks, and among which our historical investigations may be car-
ried on, are to a large extent the marine organisms which inhab-
ited the shallow seas which have existed in past time upon the
continental platforms, both on the borders and in the interiors of
the continents. The life of the dry land, that of the fresh
waters, and the aérial life, cannot have been preserved except
under exceptional conditions. The ancient life of the abysmal
depths of the oceans is unknown to us because of the entire, or
at least approximate, absence of abysmal sedimentary deposits
upon the continents.

Among the earlier geologists of the century, whose indi-
vidual observations were limited to comparatively small geo-
graphic areas, at a time when the literature of geology and
paleontology was but limited, the notion grew up that identity
of fossil species and identity of age of the strata containing the
fossils always went together. But gradually, with the increas-
ing knowledge of living marine organisms, especially of their
geographic distribution into more or less distinct provinces
limited by physical conditions such as temperature, depth, ocean
currents, purity of water, etc., and with the broadening knowl-
edge of fossils themselves, when it came to be realized that the
same organisms did not live everywhere at the same time in the
past, but that, as now, there were also during all geologic time
distinct zodlogic provinces inhabited by distinct faunas, and, fur-
thermore, that these provinces were constantly changing their
geographic boundaries, then the task of accurate or even
approximate correlation of strata over any great distances from
their fossil contents seemed to become almost hopeless. Indeed,
so hopeless did the task seem to some that in 1862, in his pres-
idential address before the Geological Society of London, Hux-
ley’ said: ‘‘ For anything that geology or paleontology are able
to show to the contrary, a Devonian fauna and flora in the British

1@, 1..G. S\, Vol. XVII, p..46:

502 STUDIES FOR STUDENTS

Islands may have been contemporaneous with Silurian life in
North America and with a Carboniferous fauna and flora in
Africa. Geographical provinces and zones may have been as
distinctly marked in the Paleozoic epoch as at present, and
those seemingly sudden appearances of new genera and species,
which we ascribe to new creation, may be simply results of
migration.”

It was doubtless due to this seemingly more or less chaotic
condition of the geographic distribution and the geologic range
of fossils, that the majority of the students of extinct life during
the latter part of the century have turned their attention to the
biologic rather than to the geologic problems involved; but these
very investigations which the biologists have made have mate-
rially assisted the paleontologic geologist in his researches. The
biologic paleontologist may, and often does, carry on his investi-
gations and make valuable contributions with little or no knowl-
edge of the geologic phases of the science save the more or
less dogmatic assertions of text-books. But the paleontologic
geologist must of necessity follow closely the results of his bio-
logic brother, though his own investigations may be something
entirely different. In fact, the perfection of the taxonomy of
fossils is to the paleontologic geologist but one of the means to
an end, and not the ultimate end sought. The two divisions of
the science may be compared with the ancient and the modern
methods in the study of human history. The biologic division
may be compared with the older method of historical study, in
which the lives of a few conspicuous characters monopolized the
whole study. On the other hand, the investigations in paleon-
tologic geology may be compared with the modern scientific
study of history, in which the evolution of society is made most
prominent, the conspicuous characters being considered as the
results of social conditions rather than as their causes.

At the present time it is believed by most, if not all, geolo-
gists and paleontologists that the great geologic systems repre-
sent practically the same time-periods throughout the world.
It is also believed by many that the limits of the recognized

ANCENLURY (OF PROGRESS LN: PALEONTOLOGY 503

geologic periods, in so far as they are really natural divisions of
geologic time,’ are practically contemporaneous. It is also
believed that about three divisions in each period may be usually
detected with much certainty throughout the world, although the
constitution of the faunas may vary to a considerable degree.

It becomes the task of the paleontologic geologist to inves-
tigate the fossil faunas, the organic societies of past time.
Through a study of the geographic distribution of species and
genera and their relationships to preceding and succeeding
forms, the approximate limit of the zodlogic provinces of past
time are determined, and from these data approximate restora-
tions of the ancient geography are made. From a study of the
changing physical conditions and the changing faunas are deter-
mined the migrations which we now know to have taken place
and which Huxley suggested as a cause of sudden changes of
fossil faunas.

Among fossil faunas as a whole there are two conspicuous
types, (1) the cosmopolitan faunas and (2) the provincial faunas.
At different periods of the earth’s history these two types of
faunas have been dominant. During Silurian time, for instance,
there seems to have been in existence a great cosmopolitan,
shallow-water, marine fauna, which is represented in America, in
Europe, in Australia, and New Zealand, and probably will be
discovered also in the other continents. The conditions for the
development of such a fauna seem to have been the presence of
widespread, shallow seas upon the continental platforms, epi-con-
tinental seas, as they have recently been called.*? With broad
seas of this sort around the borders of the continents, and
extending into the interior by means of great tongues or lobes,
and with conditions approximating base-levels upon the land,
there would be a great limestone forming epoch, and with the
probable atmospheric conditions of such an epoch3 the tempera-

™See “The Ulterior Basis of Time Divisions and the Classification of Geological
History,” by T. C. CHAMBERLIN, JouR. GEOL., Vol. VI, p. 449.

2Jour. GEOL., Vol. VI, p. 602.
3JourR. GEOL., Vol. VI, p. 609.

504 STUDIES FOR STUDENTS

ture conditions upon the earth would be far more nearly equa-
ble than they are today, so that the same species could live both
in the tropics and in the polar regions, as the distribution of the
fossils indicates to have been the case, Under such conditions
the shallow-water marine organisms would have the most favor-
able opportunity for intercommunication with all parts of the
world, and there would be developed just such a cosmopolitan
fauna as we know existed in Silurian time.

The Devonian period gives us a good illustration of the pro-
vincial typeof faunas. During this period the shallow-water marine
faunas exhibit a great diversity in various parts of the world. The
Devonian faunas in New York, or even in southern Illinois, have
less in common with those of Iowa, than have the Silurian faunas
of the interior of North America with those of Europe or even
with those of Australia. The Devonian faunas of Europe are also
different from the American, and, furthermore, they differ among
themselves. In South America and other parts of the earth there
are still other types of Devonian life. The evidence afforded by the
distribution of species and genera indicates without a doubt that
the provincial development of faunas was one of the most con-
spicuous characteristics of the period. This type of develop-
ment was, of course, brought about by the greater or less isola-
tion of great shallow-water tracts in different parts of the world,
in each of which the evolution of the life progressed along its
own peculiar lines, molded by the particular environmental con-
ditions which obtained in each tract or province. Because of
the more or less complete isolation of these various provinces,
and the absence of shallow-water paths along which intercom-
munication between distant parts of the earth was possible, the
development of a cosmopolitan fauna such as existed in Silurian
time was out of the question.

In addition to the provincial development of the Devonian
faunas, the life history of the period is complicated in a still
further degree by reason of the continuous changes in the

See “A Systematic Source of Evolution of Provincial Faunas,” by T. C.
Chamberlin, Jour. GEOL., Vol. VII, p. 597.

A CENTURY OF PROGRESS IN PALEONTOLOGY 505

geographic limits of the provinces themselves. The major
development of the several great Devonian provinces was, in all
probability, in shallow seas upon the borders of the continents,
and the more important changes in their areal distribution was
probably due to the cutting away of barriers formed by the more
or less elevated rim of the continents, and the extension of lobes
of the sea into the interior, so forming interior epicontinental
seas. It is in the sediments of these interior epicontinental
seas that the greater portion of all our Paleozoic life records
are preserved. The borders of the continents are the chief
regions of disturbance during periods of dynamic activity,
so that the records of the life in the normal border prov-
inces of such a period as the Devonian are to a great extent
destroyed.

If we were able to possess ourselves of sufficient data in
regard to the border provinces, it is probable that no sharp life
breaks would be found, but in the interior epicontinental seas,
the case is very different. By the slow cutting away by erosion
of the barrier rim, or by the local sinking of the land, communi-
cation is established successively between the interior seas, and
first one and then another of the great border provinces, and
there are successive incursions of very different faunas, which
make their appearance in the interior very suddenly, although
their evolution has been in progress in some border province
during a long lapse of time. As an illustration of such a sudden
appearance of a fauna into an interior epicontinental sea, the
fauna of the Corniferous in eastern North America may be
mentioned. This fauna with its large number and variety of
corals, its great number of cephalopods including the first goniatite,
and, most of all, the host of armored fishes, appears with com-
parative suddenness, probably from the north through Hudson
Bay, and includes many organisms which could not possibly have
been derived from the preceding Devonian faunas, the Oriskany
and Helderberg. The evolution of this fauna had probably been
in progress during all the preceeding time since the Silurian in
its more or less isolated province, but its appearance in the

506 SILUDIES FOR STUDENTS

interior epicontinental sea of Devonian time in eastern North
America was relatively sudden.

Such a sudden appearance, in a series of sedimentary rocks,
of a new fossil fauna, with apparently no genetic predecessors in
the immediate region, may be compared with the sudden appear-
ance in North America during the sixteenth century of the
advanced culture and civilization of Europe among the savage
tribes which had occupied the continent previous to that time.
Although the appearance in America of the white man with his
advanced culture was sudden, and his influence spread so rapidly
that it soon drove into practical extinction the preéxisting and
less advanced culture of the Indian, it was really the culmination
of a long and gradual development, in Europe, of the art of
building and sailing ships. Ina similar way the sudden appear-
ance of a new fossil fauna in a series of sedimentary rocks may
be but the culmination of some physical change which has been
in progress during an extended period of time. The submerg-
ance or the erosion of a land mass may be slow, and may con-
tinue through a long lapse of time, but the culmination of the
phenomenon will be when the land passes below sea level, thus
removing a barrier and allowing the immigration of a marine fauna
into a region previously occupied by a very different assemblage
of organisms. The conflict following such an immigration may
be compared with the conflict between the Indian and the Euro-
pean cultures in America.

The resulting fauna from any such incursion and mingling
within an interior sea, as has been described above, will of course
be different from either of the original faunas. The Corniferous
fauna in eastern North America, in addition to that element
which came in from the outside, contains also an element which
may be traced directly back to the preceding Oriskany or Hel-
derberg faunas which had inhabited the same region. When the
German tribes made their incursions into the Roman Empire,
bringing in a new culture, the old Roman civilization and culture
was not entirely destroyed, but there was built up a new civiliza-
tion and a new culture, differing from either the Roman or the

AZGENTURY OF PROGRESS: IN PALEONTOLOGY 507

German, which included elements from each. In the same way
a resultant fauna, formed by the mingling of two or more faunas,
will contain elements from each which can be detected by a care-
ful study and dissection of the entire assemblage of organisms.

In general, the species in any fossil fauna fall into one of two
categories: (1) indigenous evolution species, or those whose
ancestors have lived in the same region and whose evolution has
there taken place, and (2) immigration species whose ancestors
have lived in some other geologic province and whose sudden
appearance in the fauna under consideration is due to an immi-
gration from the outside. It is the work of the paleontologic
geologist to investigate each species of the fauna he may be
studying, to determine in which category each belongs, and in
the case of the immigration species to determine in what part of
the world or in what geologic province its previous evolution
has taken place, and what are the probable paths of migration.

In the historical study of fossil faunas it is interesting and
suggestive to draw parallels with the history of human races.
Until comparatively recent times there has been a remarkable
provincial development of the races of men. Among the more
primitive peoples a range of mountains or a great river was a
sufficient barrier to prevent migration, because, as in the case of
the provincial faunas, they had not means at hand for intercom-
munication between the separated provinces. But there has
been a gradual development among the human races, of means of
communication, first by beasts of burden and later by mechanical
devices, until today, through the agency of the great ocean
steamers, the transcontinental railways, and the telegraph, no
corner of the inhabitable earth can be said to be isolated. With
the increased facilities for intercommunication, there is being
developed a great cosmopolitan human race, which will in time
inhabit the whole earth, just as in far-away Silurian time there
was developed, by reason of the widespread shallow waters upon
the continents, a cosmopolitan fauna which reached from North
America to Australia.

The questions involved in this faunal history of the earth are

508 STUDIES FOR STUDENTS

complicated, but the fossils imbedded in the rocks are the data,
and these are far more indisputable than are the data upon which
ancient human history is being built. A recent writer gives the
following definition of ancient history :* ‘A confused jumble of
traditions, distorted to suit special pleaders; then rejumbled, and
mixed, and confused, and redistorted according to the design of
each new writer—the story of noble actions of big-minded men
recast in the crucible of petty intellects, untrained in public life
and unfit to grasp even the commonplace—the story of petty
actions seized upon by enthusiasts and exalted into a nobility
which would have been beyond the recognition of the original
actors—all sorts of stories attempted to be told by weak, inca-
pable men without purpose, or by unconscientious men or wilful
liars with a purpose—obscure acts twisted into curious shapes in
the brains of industrious writers—truth taken by well-meaning
men and so changed by ignorance and lack of comprehension
and unfitness to judge that it loses all semblance of its original
self and becomes a misshapen, irrecognizable, utterly twisted and
contorted thing, without much more than a vestige of fact upon
which it is supposed to be based. This is ancient history.” If
the human historian is able to build up a story of the human race
from such data, how much more certainly will the paleontologic
geologist, by diligent study and investigation of his absolutely
indisputable data, be able to build up a creditable history of the

life of the earth since Cambrian time.
STUART WELLER.
THE UNIVERSITY OF CHICAGO.

*JOHN BRISBEN WALKER, in The Cosmopolitan, March 1899, p. 476.

EDITORIAL

‘“ApouT a Reform in Nomenclature” is the title of a com-
munication in the issue of Sczence for July 28, by A. L. Herrera,
of the National Museum of Mexico. Preliminary to a specific
suggestion, attention is called to the almost insupportable burden
into which the nomenclature of the natural sciences has grown
and to the imminent need of reform. The meaninglessness of
many current names is a serious hindrance to the dissemination
of science. ‘‘The language of science is more difficult than sci-
ence itself.’

The need of reform can scarcely be urged too strenuously,
and every voice raised. in its interest is welcome. There is,
nevertheless, occasion for great circumspection in the adoption
of substitutes for the present names. It is possible, perhaps, to
make matters even worse than they now are. There is some
ground for the suspicion that this might be true of the proposed
reform, the chief features of which are as follows:

The generic names of animals to end in ws, those of plants
in a, and those of minerals inz,; minerals, to have generic names
formed from abbreviations of the names of their chemical con-
stituents, as sulphurzinct, sphalerita; the generic names of plants
to be preceded by abbreviations of the family names, as Rosa-
spirea limbata ; with a similar device for the names of animals.

One of the most serious faults of the present binomial sys-
tem is its instability, due to changes of reference of species to
genera. This is especially true in paleontology where the
original data were imperfect and new discoveries are being con-
stantly made, and are sure to continue to be made for a long
time to come. Now, to add the name of the family in the form
of an abbreviation-prefix would introduce another variable factor,
one, perhaps, even more subject to change than the generic

509

510 EDITORIAL

reference. Furthermore, the addition of the prefix would make
the already cumbrous nomenclature still more ungainly. Reform
should move in the direction of simplicity and fixity as well as
significance.

In naming minerals there is no occasion for the introduction
of the bungling binomial system. There would be an obvious
advantage in deriving the names of minerals from those of their
chemical constituents, as suggested, but if this is done a uni-
form terminal syllable is a pedantic superfluity. Szdfozinc would
sufficiently show that the subject was not a plant or an animal,
without the terminal 7. So also the Sphalerita becomes nearly
needless and quite incongruous, as it belongs to the meaningless
system which it is proposed to eliminate. In place of it a sylla-
ble to express the form of crystallization would carry out the
fundamental idea.

The most hopeful suggestion yet made for mineralogical
nomenclature proposes that the names shall consist simply of a
combination of syllables which shall indicate the’ crystalline
form and the essential chemical constituents, since these are the
characterizing elements. The main difficulty of such a system
lies in securing brevity and euphony. It would be easy enough
to improve upon the present uncouthness in the main, but not to
reach good phonic combinations in all cases. Much could be
done, however, by leaving out all useless lumber and all super-
fluous tailpieces, by reducing the abbreviations to their lowest
terms, and by giving them the best possible combining forms.
If this required that some liberties be taken in forming the
abbreviations it would be merely introducing into language that
regard for economy and utility which characterizes progress in
all the live arts. pieaKG ile

REVIEWS

RECENT BOOKS ON PHYSIOGRAPHY

Rivers of North America. A Reading Lesson for Students of Geog-
raphy and Geology. By IsraEL C. RussELi. Pp. 326. G. P:
Putnam’s Sons, 1898.

Earth Sculpture, or the Origin of Land-Forms. By JAMES GEIKIE.
Pp. 397. G. P. Putnam’s Sons, 1898.

Physical Geography. By Witv1am Morris Davis, assisted by
WitiiAM Henry Snyper. Pp. 428. Ginn & Company, 1899

These three volumes deserve the careful attention of teachers and
students of physical geography and geology, not only in secondary
schools, but in colleges as well. Some of them should also appeal
to a large class of readers who are lovers of nature, though their work
is not in educational lines.

Professor Russell’s book is well described by its explanatory title,
“A Reading Lesson for Students in Geography and Geology.” In
this volume the author has presented in readable form the leading pro-
cesses and principles involved in the history of rivers. In addition,
he has introduced, as the title suggests, much descriptive matter con-
cerning the rivers of our own continent. ‘The matter is not too tech-
nical for the high school student who is serious in his work, and will
be read with profit by college students who have rarely had a physio-
graphic topic so well presented on the printed page.

The scope of the book is in a measure indicated by the headings of
the various chapters: The Disintegration and Decay of Rocks; Laws
Governing Streams ; Influence of Inequalities in the Hardness of Rocks
on Riverside Scenery ; Material carried in Suspension and in Solution ;
Stream Deposits; Stream Terraces; Stream Development; Some of
the Characteristics of American Rivers; The Life History of a River.

In treating of these various topics the author has made no attempt
to be exhaustive, for the book has been prepared, not for the profes-
sional geographer, but for the general student who has had too little

S11

512 REVIEWS

readable matter at his command. The advanced student may wish
that the book were fuller and more explicit at some points, while others
into whose hands it will fall, will wish it more elementary. Such
infelicities are not to be avoided, and it would have been difficult, on
the whole, to have made a better selection of material. Important
topics have not been omitted, and unimportant and irrelevant ones
have not been introduced. Throughout the book the modern nomen-
clature of rivers has been used, and on this account those who have
not followed the progress of geographic science during the last ten
years will find it to their advantage to read the book in course, rather
than otherwise.

The volume has some effective illustrations, though their number is
too small (17 plates and 23 figures in text), which add to its otherwise
attractive appearance.

Professor Geikie’s volume deals with the processes involved in the
development of topography, and with the results which these processes
have effected. The first chapter is devoted to a general discussion of
the agents of denudation. The principles and processes of denudation
are then studied with immediate reference to land masses affected by
various types of structure. The topographic forms developed in
regions of horizontal strata at various stages in the progress of denuda-
tion and under various conditions are first considered. The same
principles and processes are then applied to regions where the strata
are inclined, and the topographic results under these conditions are
described and illustrated, as in the preceding case. Passing from the
more simple to the more complex, the effects of denudation in regions
of folded and highly disturbed strata are next set forth, and numerous
cuts are introduced illustrative of the more complex topographic forms
which result from denudation where the stratigraphy is complicated.

The consideration of the topographic forms developed by denuda-
tion in regions possessed of various types of stratigraphy is followed
by a consideration of the topographic effects of faults, and of volcanic
and other types of igneous action. Unfortunately the last of these
topics is less adequately illustrated than most of the preceding. The
lack of illustrations here may be less serious than it would have been
elsewhere, since illustrations of the topographic effects of volcanic
action are among the most common in our geographies. Nevertheless,
the absence of abundant illustrations seems to us a defect.

REVIEWS 513

Following the discussion of these topics, a chapter is devoted to
the topographic features which depend for their existence upon the
character of the rock rather than upon the position of its beds. The
topographic effects of structure other than stratification and the results
of the varying composition of rock are considered.

To the topographic effects of glaciation two chapters are given, and
while the text is clear, no virtue which it possesses can compensate for
the entire absence of cuts illustrative of the points described. Nowhere
are illustrations more needed, and in no field are they more easily
obtained. ‘The topographic effects of eolian action, involving a brief
consideration of dunes and of rock sculpture effected by the wind, and
of the surface effects of underground water, are next considered. In
the case of the last topic, illustrations are again altogether wanting.

A chapter is given to the discussion of basins (depressions without
outlets), and illustrations showing the real nature of basins are intro-
duced which will tend to correct the prevalent erroneous notions con-
cerning the shape of these topographic features. The topography of
coast lines is briefly discussed, and too meagerly illustrated. It is with
regret that the lack of illustrations is repeatedly referred to, but in a
book of this sort, which deals almost exclusively with the forms of the
surface, the lack of illustrations is especially serious.

The volume closes with a classification of land forms. It is to be
especially noted that the classification comes in the right place, after
(and not before) a consideration of the processes of earth sculpture
and their results, and therefore when the reader is for the first time in
a position to appreciate the force and the meaning of the classification.
This is a point which the writers of books intended to be educational
would do well to note. Many of our text-books are lumbered with
elaborate synoptical classifications preceding the discussion of the
things which are classified. When the classification in such positions
is reached by the student he has no comprehension of its meaning,
and too often does not refer to it after the chapter is read.

In spite of the one notable defect which has been referred to, Pro-
fessor Geikie’s book is to be heartily commended to students and
teachers of geography.

Professor Davis’s book differs from the others in being a text-book.
The author has followed traditional lines to the extent of including
in the volume a consideration of the atmosphere and the ocean as well

514 REVIEWS

as the land; but he has departed from traditional lines in according
to the former topics but brief treatment, while the larger part of the
book is devoted to the geography of the land. The author is under-
stood to believe that the subject of meteorology should be separated
from that of physical geography (of the land) and pursued as a distinct
subject in the secondary schools. Whatever may be said of the desira-
bility of this change, it is not likely to come about at present, and for
a good while to come such attention as is given to meteorology in the
secondary schools is likely to be in connection with physical geography.
If this be true, the consideration of the atmosphere in this volume
seems to us too brief; on the other hand, the selection of material is
excellent, and in so brief a space it would have been difficult to present
a more satisfactory outline of the subject. The inadequacy of the
treatment, however, appears to be recognized by the author himself,
who indicates that it should be supplemented by “local observations
and by the construction and study of weather maps.” Brief appendices
give some suggestions for this observational and constructional work,
but the average teacher in the secondary school will find these sugges-
tions still more inadequate than the text they supplement. Much
fuller directions will need to be given to teachers in the secondary
schools before the majority of them can difect the sort of work which
Professor Davis rightly advises.

The consideration of the ocean is likewise exceedingly brief (34
pages). Both the selection of material and its presentation are excel-
lent, but the small amount of space devoted to the subject is insufficient
to give even all the important points with which the student of the
subject, even in an elementary way, should be acquainted.

As already noted, the larger part of the book is devoted to the
consideration of the land surfaces, and it is not too much to say that
the geography of the land is presented in an essentially new light.
Here traditional lines are not at all followed, and no one whose knowl-
edge of the subject has been derived from other text-books can read
this without learning much concerning the subject and concerning the
methods of presenting it. The descriptive element enters more largely
into this volume than into most recent books on physical geography.
Topographic types are illustrated by descriptive references to specific
areas, many of which have not been well known to professional geogra-
phers. In other words, concrete illustrations of general types abound,
and they are drawn from wide sources and are definitely pictured.

REVIEWS 515

Plains, plateaus, and mountains as topographic types are considered in
order, and many illustrations of the various phases of these general
types, drawn from all parts of the world, are introduced. ‘The treat-
ment of coastal plains is especially happy. The question might be
raised whether the idea of the coastal plain is not carried rather far
when, under the heading of “Ancient Coastal Plains,” areas very dis-
tant from the sea, and which now have nothing to suggest their
‘“‘coastal”’ relations, are discussed. Thus “ the ancient coastal plains”
of Wisconsin seem to us a little remote for consideration in an ele-
mentary physical geography. The teacher who is a geologist as well as
a geographer will know how to treat this subject ; but it seems to us
likely that the text will fail to convey the right notion of these ‘“‘ancient
coastal plains,” which are no longer coastal plains, to many pupils if
not to many teachers.

The important chapters on Rivers and Valleys is excellent, and
should prove effective with classes if they have the guidance of skillful
teachers.

A significant chapter of the volume is entitled Climatic Control of
Land Forms. Here are considered such topics as the effect of climate
on streams and their work; salt lakes; the life of arid regions ; glaciers
and ice-sheets and their work. It must be confessed that the fashion-
ing of the land surface by the continental ice-sheet of North America
seems doubtfully placed in a chapter with the above title, for while
glaciation was of course a result of the climate of the time, the topog-
raphy which the ice fashioned is as really the work of the ice as the
topography developed by rivers is their work ; and it can hardly be said
that glaciers and ice-sheets are more directly controlled by climate
than rivers are. The discussion of glacial topography under the cap-
tion of Climatic Control of Land Forms, therefore, seems to us not
the happiest possible arrangement. The volume closes with an excel-
lent chapter on Shore Lines. Numerous brief appendices are added
which will be helpful to the teacher of the subject.

Throughout the volume emphasis is laid on the effects of geogra-
phy on human development, and references to historical incidents, as
influenced by topography, are frequent. This is a phase of the subject
which is most welcome.

In a book which is so thoroughly good it may seem gratuitous to
mention defects, but there is one which seems to us somewhat serious.
There is an occasional lapse into an obscure style, resulting from the

516 REVIEWS

introduction of ideas for which adquate preparation has not been made,
or from the two brief exposition of complex phenomena. The result is
that the pupil, if not his teacher, will sometimes be staggered. From
actual experience with a group of teachers, it has been found that a
large proportion of them do not catch the idea of a cuesta (p. 133),
and it is not easy to see what good purpose the introduction of the term
serves, for the pupils who will use this volume. ‘The defect referred to
above will, it is to be feared, interfere with the usefulness of this very
excellent book.

The volume is abundantly illustrated (261 figures and ro plates)
and every illustration is to the point. Half-tones have been excluded,
and engravings put in their place. There can be no question but that
in most cases the engravings are much more effective than reproduc-
tions directly from photographs, for the non-essential features are
omitted, and the essential features brought into prominence. We have
seen no text-book on this subject in which the illustrations so uniformly
illustrate the exact points which they were meant to illustrate, and in
such a way that their meaning cannot be mistaken.

The three volumes mentioned above put new and rich resources
into the hands of teachers and students of physiography, and should
result in great improvement in the teaching of the subject.

Rebs:

Transactions of the Kansas Academy of Sciences, 1597-8. Vol. XVI.

This volume of 320 pages indicates a laudable degree of activity in
various scientific lines. The presidental address by Dr. S. W. Williston
on “Science in Education” is an admirable exposition of the existing
status and current tendencies of education in liberal and professional
‘ines and contains excellent suggestions relative to desirable changes
in which science shall be a larger factor. The papers in geology and
paleontology are six in number as follows: Physiography of Southeast-
ern Kansas, by George I. Adams; /usulina cylindrica Shell Structure,
by Alva J. Smith; New Developments in the Mentor Beds, by A. W.
Jones; Fossil Turtle Cast from the Dakota Epoch, by C.S. Parmenter :
Deep Well at Madison, Kan., by F. W. Bushong ; Correlation of the
Coal Measures of Kansas and Nebraska, by J. W. Beede.

AME Ce

REVIEWS BET

lowa Geological Survey, Annual Report, 1898, Vol. IX. By
SAMUEL CALVIN, State Geologist; H. F. Barn, Assistant
State Geologist.

Statistics of Mineral Production. By S. W. BEYER; Geology o7
Carroll County, H. F. Bain; Geology of Humboldt County, T
H. McBripe; Geology of Story County, S. W. BEYER;
Geology of Muscatine County, J. A. UppDEN; Geology of Scott
County, W. H. Norton; Artesian Wells of the Belle Plaine
Area, H. R.Mosnar. Thirteen plates, 56 figures, 14 maps.

This volume of the reports of the Iowa State Geological Survey
serves to. corroborate the high opinion already established among the
geologists of the United States of the work of this organization. The
record of the Iowa survey has been one of uninterrupted excellence in
both the theoretical and the economic phases of its work. The list of
the corps engaged in the work of 1898 is of itself sufficient to invite
inspection of the report.

Each of the county reports gives a systematic exposition of the
physiographic and economic features of the geologic field under con-
sideration, each being emphasized as the peculiar characteristics of the
district demand. ‘To many ofthe reports is appended a discussion of
the forestry of the areas studied.

In the geology of Carroll county the physiography is of exceptional
interest, since the tract is bisected diagonally by the edge of the Wis-
consin drift sheet. Consequently the northeastern and southwestern
parts of the county display topographic features in admirable contrast
as the result of these relations. The Middle Coon River follows this
drift margin in a general way, receiving numerous tributaries with sec-
ondary and tertiary branches from the area of Kansan drift westward,
while from the Wisconsin drift there is only one important tributary
and that without branches. The erasure of post-Kansan drainage by
the Wisconsin invasion is illustrated by a number of examples. The
Coon River, flowing across the northeast part of the county has con-
structed a makeshift course from ‘‘bits of old captured valleys, and
new trenches which it has cut for itself.”

The stratigraphy of Carroll county includes an exposure of a Car-
boniferous limestone, probably of the Des Moines series. The Creta-
ceous is represented by several exposures of the Dakota sandstones and

518 REVIEWS

conglomerates. Some of these conglomerates include silicified Niagara
and Devonian fossils as part of the clastic materials. A few Cretaceous
fossils have been identified. Undoubted chalk rock of the Niobrara,
containing abundant /zoceramus labiatus, is exposed in one locality
in association with the Dakota sandstone.

The Pleistocene deposits are considered in detail. A new develop-
ment from the field investigation is the demonstration that much of
the extra-Wisconsin drift, hitherto provisionally correlated with the
Iowan, belongs to an anomalous phase of the Kansan, which shows
many peculiarities, near the border of the Wisconsin, due either to some
protecting influence during the period of post-Kansan erosion, or to
some subsequent modification referable to the presence of the loess and
the proximity of the Wisconsin drift. The loess is called lowan inage
and lies beneath the Wisconsin, except at some places where a thin
mantle of it covers the edge of the latter, evidently as a recent wind
deposit. The loess of this region is not of sufficient depth to have
developed its own peculiar type of topography.

The coal prospect for Carroll county is an exceedingly uncertain
problem and, in Dr. Bain’s opinion, is to be solved only by the drill,
and that only at large expense, chiefly because of the great depth of
the drift. Moreover, the great distance from the known outcrops of
coal make it possible that the productive measures may have thinned
out altogether in Carroll county. The other mineral resources of the
county are inconsiderable. The water supply is entirely sufficient.
The area includes several artesian wells.

The report for Carroll county is fairly representative of the method
and character of the work done in the other counties and only special
details of the other papers demand consideration. Mr. T. H. McBride,
in the report upon Humboldt county, identifies the Kinderhook and
Saint Louis of the Mississippian series and the Des Moines of the Coal
Measures. The latter is covered by the glacial series, of which the pre-
Kansan, Aftonian, Kansan, Buchanan and Wisconsin are recognized.

The Wisconsin sheet is merely a thin veneer, conforming to the
previously established Kansan-Buchanan topography. This is worthy
of note in the light of other observations on the relations of recent
drift sheets to underlying unindurated formations. The somewhat
paradoxical inference is suggested that the ice sheet was normally less
competent to disturb the surface of a deep formation of loose materials
than the surface of an exposed indurated rock. A gravel formation,

REVIEWS 519

as itwas being overridden, became the basal part of the ice and
exhausted to a degree its transporting capacity, forming the effective
load of the natural stagnation zone at the base of the ice. Over a rock
surface, on the other hand, the ice may have possessed its maximum of
transporting and abrading power.

A unique detail in the drainage of Humboldt county is the practice,
reported of draining kettle-hole lakes in certain districts by sinking
wells through impervious layers to a porous stratum. The method
appears to be effective and economical, though its sanitary bearing
upon the drinking water of the region may be worthy of consideration.

A notable feature of Mr. Beyer’s report on Story county, also of
Professor Udden’s on Muscatine county, is the determination of defor-
mations. The gentle flexures, of which the Skunk River anticline is a
type, are suggestive when considered with similar structures which have
been reported at many points in the exposures of different formations
across the upper Mississippi basin. The reiterated recognition of such
structure suggests that the phenomena of crustal shortening have been
restricted by no means to the mountain belts of the coastal regions
but that these gentler flexures, affecting such immense areas, may have
been, inthe aggregate, an equally notable factor in the adjustment of
the external masses of the earth to internal changes.

Mr. Beyer gives an excellent report on the stratigraphy, including
many valuable well records. ‘The discussion of the development of
the Skunk River system is an instructive physiographic study. The
course of the pre-Wisconsin channel, the transference of much of the
Skunk River drainage area to the Des Moines system by the Wisconsin
invasion, the post-glacial struggle of the stream toward readjustment,
form the substance of a finely developed discussion. Remains of the
Mammoth are reported by Mr. Beyer from an excavation four or five
feet below the surface of the Wisconsin drift. Coal, clay and building
stones are the economic products of Story county.

The report on Muscatine county by Professor Udden is characterized
by carefully derived conclusions and is rendered thoroughly readable
by the excellent style of presentation, and enjoyable by the variety of
new and sharply observed phenomena. ‘The stratigraphy of the county
includes the Gower stage of the Niagara, Wapsipinicon and Cedar
Valley stages of the Hamilton, Sweetland Creek beds of the Upper
Devonian, Kinderhook group of the Mississippian and the Des Moines
stage of the Coal Measures. This article contains an exhaustive discussion

520 REVIEWS

of the drift with many close, but distinctly drawn, discriminations. The
following Pleistocene formations are recognized : anteglacial silts, pre-
Kansan, Aftonian, Kansan and Illinoian. The anteglacial silt isa new
division. Itis explained as having been formed by water and wind ahead
of the invading pre-Kansan ice-sheet. If that be its origin, it might
properly belong with the pre-Kansan drift and the division would appear
unnecessary. If every aqueous deposit of the drift should receive a
special name, the clarifying effects of analysis would soon be lost in
confusion. ‘The economic products of Muscatine county include coal,
though in unprofitable amount, small quantities of gas, building
stones and clay.

The geology of Scott county, by Professor W. H. Norton, contains
much fresh information. ‘The passages in the paper dealing with the
history of the drainage and with the stratigraphy are of special value.
Touching the former, this region is particularly interesting because of
its location at the southern limits of the driftless area and the con-
sequent complexity of the drift phenomena arising from the mutual
interference of the ice lobes at this place.

The report on the artesian wells of the Belle Plaine area by H.R.
Mosnat gives a thorough exposition of the geology of the water-bearing
formation, the amount of the flow and the source of the water. ‘The
computations rising from the study of flow and supply develop many
facts which simplify to a great degree the conception of the combina.
tion of conditions appropriate to the formation of artesian wells. A
most significant passage is that discussing the rate of movement of the
underground water through materials of different texture. It is
estimated that nineteen years would be required for the water of the
aquifer to move in a direct line from Vining to Ladora along the major
axis of the artesian area. Hence, the writer concludes, the great exhaus-
tion of the water body brought about at Vining by the remarkable flow of
the great Jumbo well when it was opened, will not affect the flow at
Ladora before the year 1905. He also shows the limited extent of sur-
face actually necessary to supply the water for the aquifer and the ade-
quacy of the rainfall to produce the supply without any recourse to the
extravagant superstitions which have made this artesian area ‘the
eighth wonder of the world” in the minds of the inhabitants of the
region. ‘The discussion is closed with a paragraph on the uses of the
water, which largely relegates the wells to the category of interesting

REVIEWS Om

geological phenomena whose practical and economic value is doubtful
or, at any rate, decidedly limited.
This volume is carefully printed and amply illustrated by expressive
and well selected photographs, sections and sketch maps.
J. W. FIncuw.

RECENT PUBLICATIONS

—Ami, HENry M. Ona New or Hitherto Unrecognized Geological Horizon
in the Gas and Oil Region of Western Ontario. Extract from Journal
Canadian Mining Institute, Vol. II, pp. 186-191. Ottawa, 1899.

—ANDERSSON, GUNNAR. Studier Ofver Finlands Torfmossar och Fossila
Kvartarflora. Bulletin de la Commission Géologique de Finlande. No.
8. Helsingfors, 1898.

—BARRIOS, Dr. CHARLES. Sketch of the Geology of Central Brittany.
Reprinted from the Proceedings of the Geologists’ Association. London,
1899.

—BouLeE, MARCELIN. Note sur de Nouveaux Fossiles Secondaires de Mada-
gascar. Bulletin du Muséum dv’histoire naturelle. Paris, 1899.

Note Préliminaire sur les Débris de Dinosauriens Envoyés au Muséum par
M. Bastard.

—BouLe, MARCELIN and GUSTAVE CHAUNET. Sur]’Existence d’une Faune
d’Animaux Arctiques dans la Charente a l'Epoque Quaternaire.

—BOovutTwELL, J. M. Bibliography of Geographical Works Published in the
United States in 1898. Bulletin of American Geographical Society, Vol.
XXXI, No. 3.

—BRIGHAM, A. P. The Eastern Gateway of the United States. From the
Geographical Journal for May 1899.

—BROADHEAD, G. C. Reports on Boone County and the Ozark Uplift.
Vol. XII, Part III. Geological Survey of Missouri. Jefferson City, 1898.

—Bulletin of the Gulf Flora and Fauna. Ruston, La., 1899.

—Department of Mines and Agriculture. Records of the Geological Survey
of New South Wales, Vol. VI, Part II, 1899. Sidney, Australia.

—GERLAND, Pror. Dr. GEORG. Beitrage zur Geophysik Zeitschrift fiir
physikalische Erdkunde Herausgegeben. III Band, 1 Heft, and IV
Band, 4 Heft. Leipzig, 1899.

—HILLEBRAND, W. F. and H. W. TURNER. On Roscoelite. With a Note
on its Chemical Constitution by F. W. CLARKE. American Journal of
Science, Vol. VII, June 1899.

—Hosss, Wu. H. Goldschmidtite,a New Mineral. American Journal of
Science, May 1899.

A Spiral Fulgurite from Wisconsin. Jdzd., Vol. VIII, July 1899.
522

RECENT PUBLICATIONS 523

—Iowa Geological Survey, Annual Report, 1898. Vol. Il. Des Moines,
1899.

—LEFORT, F. Fausseté de l’Idée Evolutioniste Appliquée au Systeme
Planétaire ou aux Espéces Organiques. Lyon, 1899.

—Manila, Observatoire of. Boletin Mensual, 1897.

Baguios o Ciclones Filipinos. P. ALGUE, S. J., Director.
La Erupcion del Volcan Mayon en los Dias 25 y 26 de Junio 1898. P.
JosE Coronas, S. J.

—Moorg, J. Percy. A Snow-Inhabiting Enchytreid (Mesenchytraus soli-
fugus Emery) Collected by Mr. Henry G. Bryant on the Malaspina Gla-
cier, Alaska. Natural Sciences, Philadelphia, 1899.

—SEARS, JOHN H. Biotite Tinguaite Dike Rock. Catalogue No. 960. From
the Bulletin of the Essex Institute, Vol. XXIX, 1897.

—STEINMANN, HERR. Die Entwickelung des Diluviums in Siidwest Deutsch-
land. Zeitschr. d. deutsch. geolog. Gesellschaft. Jahrg. 1898. Freiborg.

—Transactions of the Kansas Academy of Sciences. Vol. XVI, 1897-8.
Topeka, 1899.

—TurRNER, H. W. The Occurrence and Origin of Diamonds in California.
From the American Geologist, Vol. XXIII. March 1899.

—WAHNSCHAFFE, FELIX. Ueber das Vorkommen von Glacialschrammen auf
den Culmbildungen des Magdeburgischen bei Hundisburg. Berlin, 1899.

THE

JOURNAL OF GEOLOGY

SHPTEMBLER-OCTOBER, 1600

THE OZARKIAN AND ITS SIGNIFICANCE IN
THEORETICAL GEOLOGY.

I. THE OZARKIAN.

In 1886 I published a paper entitled ‘“‘A Post-Tertiary Eleva-
tion of the Sierra Nevada, as shown by the River-beds.” ' Again
in 1891 I published a paper on “ The Mutual Relations of Land
Elevation and Ice Accumulation during the Quaternary Period.”?
The following paper may be regarded as a continuation of the
lines of thought suggested by the two preceding.

By continued reflection on the enormous changes that
occurred in the western part of the continent at the end of the
Tertiary, I have been led to recognize the existence of an epoch
of long duration and of great importance immediately preceding
the time of the invasion of the ice sheet. On account of its
great importance this epoch certainly deserves a distinctive name.
For want of a better, I adopt that of the ‘ Ozarkian,” given it
by Hershey. ,

Ehstory of the name.—The epoch was first recognized by Hil-
gard and more distinctly by McGee, as the post-Lafayette uplift,

*Am. Jour. Sci., Vol. XXXII, p. 167, 1886.

? Bull. Geol.. Soc. Am. Vol. I, p. 329.
Vol. VII, No. 6, 525

526 JOSEPH LEE CONDE

shown by extensive erosion of the Lafayette gravels all over
the southern states. But a distinctive name was first given it by
Hershey,’ who called it Ozarkian in commemoration of its work
in the formation of the remarkable gorges of the region of the
Ozark Mountains. He, however, fully recognized its importance
as a time of general uplift and erosion, but regarded it as only
an episode comparable with the Kansan or Iowan episodes of the
Glacial epoch. The name was adopted, though somewhat reluc-
tantly, by McGee (Sci. III, 796, 1896), and its importance more
fully recognized,’ but he regards it as belonging to the Pliocene
and not the Quaternary. This point we shall discuss later. A
little later (Am. Geol. XVII, 389, 1896) Upham also adopts the
name, and, like Hershey, refers it to the early Quaternary, but
advances it to a primary division of that period comparable with
the Glacial. But even yet, it seems to me, its full importance is
scarcely recognized unless it be by McGee, and its true signifi-
cance entirely overlooked. Indeed both its importance and its
significance are brought out in strong relief only by the study of
its phenomena in the western part of the continent and especially
in California.

If with Upham we divide the Quaternary period into three
epochs, the Ozarkian, the Glacial, and the Champlain, then the
Ozarkian was by far the longest, in fact, longer than both the
others put together. Or again, if the Quaternary be divided
into two epochs, the Ozarkian and the Glacial, the Champlain
being merged into the Glacial, as is commonly done by Euro-
pean geologists, then of the two, the Ozarkian is by far— perhaps
by many times——the longer. In many ways the Ozarkian is
strongly contrasted with the other epochs of the Quaternary. If,
for example, we adopt the division into three epochs, these are
characterized each in its peculiar way ; the first, by elevation; the
second, by ice accumulation ; the third, by depression ; the first,
by immense erosion; the second, by glaciation and drift deposit ;
the third, by stratified deposits in seas and lakes.

t Science III, 620, 1896.

2“The reference of the Ozarkian to the Pleistocene would multiply by many
times the commonly recognized duration of that period.” McGee, Sci. III, 796, 1896.

THE OZARKIAN AND ITS SIGNIFICANCE 527

The Ozarkian has heretofore attracted little attention, because
until very recently geological history was supposed to be
recorded only in stratified rocks and their contained fossils; but
this being a period of continental elevation and enlargement, it
has left no strata exposed to view. Geological history was at
that time recorded only by erosive work. So far as stratified
rocks and fossils are concerned, this is a period of lost record—
it is a lost interval.

I said that the real importance and significance of this epoch
is best seen on the western part of the continent. I must justify
this assertion by a comparison of the phenomena in different
parts of the continent.

1. The eastern part—I\n the eastern part of the continent, the
work of erosion of this time is seen in the so-called old river-
beds deeply underlying the present beds and extending beyond
their limits on each side, and especially continuing beyond the
limits of the present continent, as submerged channels trenching
the submerged continental shelf, notching deeply its margin and
opening out into the abyssal waters of the true oceanic basin.
It is shown also not only in the deep gorges of the Ozark region,
not only in the deep and widespread erosion of the Lafayette
gravels in the south, but also in the highly emphasized topog-
raphy underlying the drift all over the glaciated region of the
north. By means of the submerged channels the amount of ver-
tical elevation of the eastern portion of the continent has been
estimated as certainly not less than 3000-5000 feet and may
have been much greater. Similar evidences of elevation are
found on the Pacific coast and also on the coasts of Europe and
of Africa. We have every reason to believe that it was a time
of almost universal continental elevation and enlargement.

Heretofore these old rivers of the east have been referred,
like those of the west, to the Tertiary times and called Tertiary
river-beds; although it is admitted that they were occupied and
deepened by the ice of the Glacial times. The Tertiary erosion
was supposed to have graded insensibly and continuously into
that of the Glacial, but the greater part was attributed to the

528 JOSEPH LE CONTE

Tertiary; and the post-Tertiary erosion was supposed to be
wholly Glacial. According to my view, on the contrary, the
post-Tertiary erosion was by far the greater and was pre-Glacial
in time, z. ¢., Ozarkian.

In the eastern portion of the continent, therefore, the Ozar-
kian grades into the Tertiary, but is well marked off from the
present by the depression and sedimentation of the Champlain.

2. The mid-continental or plateau region.—In the plateau
region, on the contrary, the Ozarkian work is: sharply marked
off from the Tertiary, but grades insensibly into that of the
present.

It is well known that the plateau region has been rising ever
since the end of the Cretaceous—that from being the lowest
part of the interior continental basin, it has become the highest
part of the continental arch. The amount of elevation during
this time has been at least 20,000 feet, about 12,000 of which
has been carried away by erosion, leaving still 8000 feet of gen-
eral elevation. Of this enormous general erosion, the largest
part—shown by the receded and still receding cliffs — prob-
ably belongs to the Miocene. The canyon-cutting is certainly
post-Miocene. The outer canyon (of the Grand Canyon) ten to
fifteen miles wide and 3000 feet deep, belongs to the Pliocene;
while the inner gorge, 3000 feet deep but very narrow, belongs
to the post-Pliocene, 2. ¢., to the Ozarkian and the present.

I said the Tertiary work is sharply marked off from the
Ozarkian but the Ozarkian grades insensibly into ‘present. The
evidence of this is given by Dutton, as follows:

Between the Pliocene work of the formation of the outer
canyon, and the subsequent work—Ozarkian to present—the
cutting of the inner gorge, there was an interval of rest marked
by a wide shelf between the two. The rising and the down-
cutting was continuous during the Pliocene until finally the river
reached its base level of erosion and rested from further down-
ward cutting and commenced to sweep from side to side widen-
ing its channel, until the canyon walls were nearly ten miles
apart. Then began the Ozarkian rise and the beginning of the

THE OZARKIAN AND ITS SIGNIFICANCE 529

cutting of the inner gorge, which has continued to the present
time. The elevation during the Tertiary was regional, the eleva-
tion which commenced with the Ozarkian was continental or even
more widespread. In the east there was a sharp demarcation
of the Ozarkian from the present erosion by the Champlain
depression and sedimentation ; which depression, as I suppose,
was determined by the weight of the ice sheet. But in the
plateau region there was no ice sheet—it did not extend so
far —and therefore there was no depression and therefore no
interruption of the erosion to the present time ; for the rising is
still progressing. The whole series of phenomena in this region
may be well explained by a local rise continuous from the end
of the Cretaceous till now, except that it was interrupted at the
end of the Pliocene by the Lafayette depression of McGee and
afterwards greatly enhanced by the general continental elevation
of the Ozarkian.

3. Serra region. — But it is in the Sierra region alone that we
find the Ozarkian erosion-work sharply marked off both from the
Tertiary on the one hand and from the present on the other. It
is here therefore that the distinctive Ozarkian work can be best
studied.

Brief history of the Sierra-—Yhe Sierra Nevada, as is well
known, was formed at the end of the Jurassic by lateral pressure
and strata-folding in the usual way. What kind of a mountain
it was at that time, how high, and what its configuration we
know not ; forthe continuous erosion of the Cretaceous and Ter-
tiary times had nearly swept it clean away. The cycle of its
mountain life had reached its last stages. By continuous erosion
it had been reduced to a peneplain, with its wide-sweeping
curves of broad shallow channels and low-rounded divides.
The rivers had reached their base levels and rested. This was
the work of the Cretaceous and Tertiary.

Then came the post-Tertiary rejuvenation of the mountain

‘As the term Ozarkzan had already been used by Broadhead for a Lower Silurian
series in the Ozark region (Am. Geol., XI, p. 260, 1893) there may be an admissi-
bility of its use in this connection. If so, I would propose the name Sverran as far
moye appropriate.

530 VOSE PAH ALTEANGONTE

life; by the formation of a fissure on the eastern slope, the
hheaving of the whole mountain block on its eastern side with a
great eastern fault-scarp,; the transference of the crest to the
extreme margin with great increase of the western slope and
consequent revival of the erosive energy of the rivers. Coinci-
dent with this in middle California there was a great outpouring
of lava which ran in streams down the western slope, filling up
the old river beds, and displacing the rivers. The displaced
rivers, with recently and fiercely aroused energy, immediately
commenced cutting new channels, which are now 3000 to 6000
feet deep, and far below the old; so that these latter are left
with their lava-covered gravels high up on the present divides
This was the work of the Ozarkian. This intensely interesting
geological story has been so often told that we only recall here
its outlines in order to apply them to the case in hand.

In southern California, beyond the limits of the lava flows
this post-Tertiary elevation and revival of erosive energy was
fully as great, or even greater than in middle California; but the
rivers were not displaced, and therefore they continued to cut in
the same places, but to far deeper levels ; so that the margins of
the wide old river beds with their gravels are left hung up high
on the sides of the present canyons.? The distinction, however,
between the wide shallow tertiary troughs and the deep narrow
post-Tertiary canyons is equally sharp here.

We have spoken thus far only of the deep canyons which
trench the western slope as being of post-Tertiary origin ; but the
same is true also of the whole scenery of the high Sierra. It all
belongs to the post-Tertiary, and its bold, rugged, savage gran-
deur is due to its extreme recency. The wildness of youth has
not been yet tempered and mellowed by age.

It is evident then that the Ozarkian is here sharply marked
off from the Tertiary. How is it in regard to its relation to the
present? In the lower parts of the canyons the Ozarkian grades
insensibly into the present, for the rivers are still, cutting. But

tAm. Jour. Sci., Vol. XX XII, 167, 1886.

2 Am. Jour. Sci., Vol. XXXII, 174, 1886.

LAE VMOLARIMGAN AND ITS SIGNIFICANCE 531

in their upper parts the two are separated by the glacier erosion.
The upper canyons were occupied by glaciers, and the compari-
son of these upper with the lower canyons shows that while their
forms were modified, and perhaps their depths somewhat
increased, they were not made by thisagency. This was mainly
the work of the post-Tertiary but pre-Glacial times, z.¢., of the
Ozarkian. But the glaciation serves to show how much has
been done by water since the Glacial,z. ¢., during the present
times; and we find it very insignificant.

In conclusion, no one who sees and reflects upon the prodi-
gious work done in the Sierra since Tertiary times can resist the
conviction that even making all due allowance for exceptional
energy and rapid work, determined by high slope and also for
other causes of rapid work explained in a previous paper,’ the
time necessary must have been enormous—many times as great
as any reasonable estimate of the duration of the Glacial epoch.

II. SOME MODIFICATIONS OF MY PREVIOUS VIEWS.

In the article already alluded to, on the “Relation of Land
Elevation and Ice Accumulation” I attempted to reconcile the
two antagonistic views in regard to the attitude of land during the
Glacial epoch. According to some writers the land in high latitude
regions was greatly elevated ; according to others it was on the con-
trary depressed. According to the one, the intense cold and ice
accumulation was the direct result of the elevation, and a subse-
quent depression produced a moderation of the climate and a
melting and final disappearance of the ice ; according to the other,
the ice accumulation was not coincident with the elevation and,
therefore, there must have been some other cause for the cold and
ice accumulation. In the paper referred to I showed that all the
phenomena might be satisfactorily explained by supposing that
the elevation was the cause of the cold—the cold the cause of
the ice accumulation— the weight of the accumulated ice the
cause of the depression—the depression the cause of returning

* Origin of Transverse Mountain Valleys, Univ. Chronicle, Vol. I, No. 6, p. 179,
1898.

532 SOSERTIMEENGON DLE

warmth — the warmth the cause of the melting and retreat of the
ice,and finally that the removal of the ice-load was the cause of
the re-elevation to the present condition; but—and this is the
distinctive feature of my view—that in all these cases che effects
lagged behind the causes. 1 showed that this was so in all cases
of accumulated effects, but would especially be true in this case.
To illustrate these relations I used a diagram which I here pro-

*Serfiary Present

Fic. 1.—Diagram showing the relations of land elevation and ice accumulation
during the Quaternary. A&W—course of time and also the present status of earth
crust. The dotted line shows elevation if it had not been interfered with by the
ice-load.

duce. The legend will sufficiently explain it. By this view the
Quaternary consists of two epochs, the Glacial and the Cham-
plain, of nearly equal lengths. The one characterized by eleva-
tion and cold, the other by depression and warmth, but the
extreme of ice accumulation lagged behind the extreme of
elevation as seen in the figure.

I am more and more convinced that the principle of lagging
is a true one and even more important than I at that time sup-
posed. I now believe that I did not at that time make the lag-
ging, especially in the matter of the accumulation of the ice-
load, great enough. We must make a distinction in this regard
between the intensity of the cold and the thickness of the
accumulated ice. The cold probably responded somewhat
promptly to the land elevation, but not so the ice accumulation.
This was a very slow process and might lag to any degree
behind the elevation and the cold. This we now proceed to
show.

1. Snowfall depends on cold, but still more upon moisture.

THE OZARKIAN AND ITS SIGNIFICANCE 533

Now there is nothing in the way of supposing — but on the con-
trary much reason to believe—that the period of great elevation
was one of comparative dryness and that the climate became
moister in the latter part when the elevation was not so great.
This would make the ice accumulation lag behind the elevation
and the cold.

2. But again: We must, of course, make a wide distinction
between the annual snowfall and the rate of accumulation ; for
this latter is the result only of the annual excess of snowfall over
waste by melting and evaporation, and this excess may be to any
degree small.

2 AGeitas, the wvceness atid therefore the wezgkt ot the
snow that we are here concerned with, it must be remembered
again that there is still another and much more important source
of waste antagonizing local accumulation and therefore increase
of thickness, viz., the run-off—not the run-off as water but as
ice by glacial motion. After a certain thickness is attained this
run-off completely balances the annual excess over waste by
evaporation and melting, and prevents, farther increase of thick-
ness. This is the case now in all glacial regions. In the Alps,
the Himalayas, etc., there is no indefinite increase of thickness
because the run-off by glacial motion completely balances the
annual excess. Similarly in Greenland, and the Antarctic con-
tinent although there is great excess of snowfall over waste
by evaporation and melting, yet there is no increase in the
thickness of the ice sheet because the excess is balanced by the
run-off of the ice into the sea and the formation there of ice-
bergs which are carried away by oceanic currents.

So also in Glacial times, after a certain thickness of snow had
accumulated on any given area— say the Canadian highlands —
the farther increase would be prevented, because balanced by
the ice-sheet motion in all directions. Any increase of thick-
ness would require not only excess but zucrease of excess and
would be extremely slow because always kept in check by the
increased run-off.

To sum up: Suppose, then, the highlands about Hudson

534 JOSE RAAT CONTE,

Bay to have been the center of elevation, of ice accumulation
and of radiating run-off: Suppose farther, that the elevation
commenced about the end of the Pliocene and was the cause of
the cold. Then considering the previous warmth of the Tertiary
times, it is probable that the elevation would go on for a long
time and reach a considerable degree before there would be any
snowfall at all in this region, and still much longer time before
there would be annual excess over waste by evaporation and
melting, z. ¢., before there would be perpetual snow. After per-
petual snow was reached, under the effect of the ice-sheet motion
tending ever to bring about equilibrium, the increase of the
thickness of the ice sheet must have been extremely slow. In
fact, it is evident that no such thickness as actually occurred could

Fic. 2.—Diagram showing supposed relation of land elevation to ice accumula-
tion, as now revised.

have been attained at all, but for the subsidence of the earth-crust
under the weight of the ice. The increased thickness was con-
ditioned upon and waited on the subsidence. I believe, there-
fore, that an increase of one inch per annum would be an extrav-
agant estimate. At this rate it would take 150,000 years to
make a thickness of 12,000 feet, which is the estimate of Dana.
To this must be added the much greater time before the per-
petual snow was formed at all.

Under the light of these estimates and especially of these
new views of a long Ozarkian epoch preceding the glacial epoch,
I would therefore modify my previous diagram, making the begin-
ning of the ice accumulation much later and making both the
Glacial and the Champlain much shorter than before, as shown in
the revised diagram, Fig. 2. The greater distinctness of the
Ozarkian from the Glacial is shown

THE OZARKIAN AND ITS SIGNIFICANCE : 535

III. SIGNIFICANCE OF THE OZARKIAN.

In my papers on Critical Periods tn the History of the Earth, in
1877 and in 1898" I try to show that there are periods of great
and widespread changes in the earth’s crust, in climate, and in
organic forms. These I call ‘‘critical periods’”’ and insist that
they separate the primary divisions of geological, time, viz., the
eras. Being periods of great elevation and enlargement of con-
tinents, they are to a great extent “lost intervals,” z. ¢., periods in
which the usual record of stratified rocks and contained fossils
is interrupted. The last of these was the Quaternary. The
Ozarkian was largely a lost interval so far as stratified record is
concerned.

Great cycles in the evolution of the earth—Now an era, 7. é.,
the time from one critical period to another, must be regarded
as one great cycle of widespread changes; during which, how-
ever, there may have been and indeed undoubtedly were, sub-
ordinate and more local cycles. Such a great cycle was the
Paleozoic, very regular in its course in this country. Such another
great cycle was the Mesozoic, but affected in this country with
a well marked subordinate division at the end of the Jurassic.
Still another such great cycle and again very regular in this
country was the Cenozoic, and such another, I am convinced, is
even now commencing. I have called it the Psychozoic.

I have supposed these to be cycles in the evolution of the
earth. They are,’ therefore, such in every department alike.
They are cycles in the evolution of earth-forms, constructively,
2. ¢., by tntertor forces in continental elevation and mountain for-
mation. They are cycles in the evolution of earth-forms, destruc-
tively, t.e., by extertor forces and erosive sculpturing. They are
cycles of evolution in climatic conditions. And, finally, as the
result of all these, they are also cycles in the evolution of organic
forms and their geographical distribution. Most of these various
forms of cyclical movement I have discussed in my previous
Papers, especially “thatmin’ 1895. These, therefore, 1 merely

* Am. Jour., Vol. XIV, 99, 1877. Bull. Geol. Dept. Univ. Cal., Vol. I, 314, 1895.

536 SO STEP TT MIE AG OINGRE:

mention and pass on. Some, however, I discuss fully now for
the first time.

1. Cycles of constructive forms.—Of the four great kinds of
earth movements treated of in my address as President of Geo-
logical Society of America, December 1896," the greatest, viz.,
that by which are formed oceanic basins and continental arches,
being determined by unequal radial contraction in the secular
cooling of the earth, which in its turn is the result of an original
heterogeneity in the density and especially in the conductivity of
different parts of the earth, must have a cycle coéxtensive with
the life of the earth itself, and therefore may be left out in this
discussion. But superimposed on this greatest, there are other
cycles of oscillations of the earth’s crust over wide areas—of
continental elevation and depression, accompanied with the for-
mation of great mountain ranges. These are the cycles of next
importance, and with which we are here concerned; for they
determine all other cycles mentioned above, and therefore the
occurrence of what I call critical periods. They are demon-
strated by the widespread unconformities which occur at these
times. Upon these, again, are superimposed still lesser cycles
which, however, do not concern us here. I have sufficiently
treated of these, both great and small, elsewhere, and therefore
pass on.

2. Cycles of climatic conditions. — Coincidentally with the
changes by continental elevation and depression with their
attendant mountain-making, there have undoubtedly been con-
current changes in climatic conditions of many kinds, especially
of temperature. These changes were, on the whole, probably
gradual throughout the era, but culminate and oscillate in the
critical period which closed it and constituted one of its most
marked features. The two most conspicuous examples are those
which occurred at the end of the Paleozoic and at the end of
the Tertiary. The early Paleozoic was eminently an oceanic
period. During the whole Paleozoic there was, in this country
at least, a gradual elevation and enlargement of the continent,

t Bull. Geol. Soc. Am., Vol. VIII, p. 113, 1897.; Sci., Vol. V, p. 321, 1896.

THE OZARKIAN AND ITS SIGNIFICANCE 537

slow at first, but rapidly increasing toward the end and culmina-
ting in the formation of the Appalachian chain. Concurrently
with this there was, almost certainly, a gradual decrease of tem-
perature rapidly culminating at the end in something approach-
ing, at least, a true glacial epoch in the Permian. Similarly,
there was probably, during the Tertiary, a gradual elevation and
increase of land and diminution of temperature, culminating
somewhat rapidly at its end, in the Ozarkian elevation and the
Glacial ice sheet. Similar changes occurred at other critical
periods, but less conspicuously.

I have been accustomed, in default of any other and more prob-
able cause, to attribute the increase of cold directly to the increase
of elevation, although admitting its possible insufficiency. It is
this apparent insufficiency that constitutes the only justification
of extra-terrestrial theories of Glacial climate, such as Croll’s,
etc. Recently Professor Chamberlin has contributed to the Jour-
NAL OF GEOLOGY* some admirable and suggestive speculations on
the cause of these cycles of climate and of life. According to him,
the continental elevation is not the direct, but mainly the zudz-
vect cause of cold, by the exhaustion of the supply of CO, in
the air by continuous rock-decay during these land-periods.
This supply is supposed to be restored from the interior of the
earth through fissures, etc., produced by the commotions of these
times. He, moreover, correlates these changes in elevation and
in temperature in a most suggestive way with alternating richness
and poverty of life and corresponding alternations of limestones
and sandstones. I cannot, of course, dwell on these very sug-
gestive views, but only draw attention to the fact that the cycles
of which Professor Chamberlin speaks correspond to the smaller or
subordinate cycles spoken of on pages 536 and 537, and of to the
great cycles separated by critical periods and constituting eras.
Nevertheless, there is no reason why similar causes acting with
greater intensity at long intervals should not determine the
greater cycles also.

3. Cycles of geographic diversity of organic forms and of rates of

*JouR. GEOL., Vol. VI, pp. 597, 609, 1898.

538 JOSE PETER GON TLE

evolution.— We have already explained in a previous paper’ how,
during the course of a cycle, the geographical diversity of
organic forms in isolated regions becomes greater and greater
indefinitely as long as isolation continues, until finally synchronic
correlation of strata in different regions becomes difficult or
impossible. But that during critical periods (and to less degree
at other times) there occur wide migrations and mingling of
faunas and corresponding obliteration of geographical diversity,
only to commence again with new isolations and a new geo-
graphical diversity increasing again with time. ‘Thus there are
alternations of increase and obliteration of faunal diversity. This
idea has an important bearing on the doctrines of synchrony and
homotaxy. At the beginning of a great cycle immediately after
a critical period, geographical faunas commence, as it were, all
abreast; synchrony and homotaxy are now in harmony. As
time goes on, the newly mingled but re-isolated faunas develop
in different directions and at different rates, become more and
more divergent in character, and more and more different in
grade of evolution. Synchrony and homotaxy become more
and more discordant, until at the end of the cycle it becomes
extremely difficult or even impossible to correlate strata of dif-
ferent countries synchronically. Then there comes another
critical period of widespread oscillations of crust and readjust-
ment to new conditions of equilibrium with accompanying oscil-
lations of temperature and wide migrations of species and
mingling of faunas and floras, hastening the steps of evolution
everywhere, but obliterating geographical diversity, and, as it
were, evening up again synchrony and homotaxy, only to com-
mence a new cycle by re-isolation.

An attempt is made to roughly represent this process by a
diagram (Fig. 3). In this diagram two cycles are represented.
In the first, Europe is ahead, and increasingly so as the cycle
goes on, and Australia is most lagging. In the second, North
America is ahead. In each the divergence between synchrony
(the full waving lines) and homotaxy (the horizontal dotted

* Bull. Geol. Dept. of Univ. of Cal., Vol. I, p. 314, 1895.

Grades of Evolution

THE OZARKIAN AND ITS SIGNIFICANCE 539

lines) becomes greater and greater until the end of the cycle,
when there comes a critical period of wide migrations of species
(represented by the horizontal arrows), a mingling of faunas, a
fiercer struggle for life, together with the more active operation
of other factors of evolution, and a consequent hastening of the
steps of evolution everywhere, but especially in the lagging
areas, to a more or less even general line. In the second cycle

N- Am * Europe S Afr? Austr

Fic. 3. Diagram showing the general relations of synchrony to homotaxy in
geological times. Full lines represent the same time in different places (synchrony),
Horizontal dotted lines represent equal stages in evolution (homotaxy).

the same process begins and progresses, except that now America
is ahead, and increasingly so until the next crisis; when the syn-
chronic lines are again evened up to parallelism with the homo-
taxic. If it were not for these occasional evening-ups a general
geological history based on organic remains would be impossible.

The whole process may be likened to a long army line
marching abreast over a broken country, led by officers, who
may be compared to the dominant types. Soon the line

Graces. or S2Volui1 om

540 JOSEPH EE CONTE

becomes irregular, and more and more so, until it is no longer
discernible and all seems confusion. At certain intervals the
leaders run along the lines hastening up the laggards until the
line is re-formed. But the re-formed line again soon becomes
irregular and falls into confusion, and is again re-formed, and
so on.

Of course partial and more or less local readjustments of
synchrony and homotaxy take place at intermediate times at the
end of subordinate cycles. Sometimes in the general readjust-
ment some locality may be left out. This is the case with Aus-
tralia today. The last wide migrations and minglings of faunas
and obliteration of geographical diversity, viz., that during the
Quaternary, did not reach Australia, and therefore its fauna is
still far behind in the race of evolution. .

4. Cycle of topographic forms by eroston.— But there is still
another cycle, and one with which we are especially concerned
here, viz., the cycle of erosion-forms. Every critical period is a
time of the formation of great mountain ranges, and the crisis is
usually named after the mountain range which forms its most
conspicuous monument. Thus we have the Appalachian revolu-
tion, closing the Paleozoic ; the Cordilleran, closing the Mesozoic.
The pre-Cambrian crisis might well be called the Laurentian,
and the one we are now specially dealing with, viz., the Quater-
nary or Ozarkian, might well be called the Basin Ranges revolu-
tion; for not only the basin ranges, but also the Sierra Nevada,
the Coast Ranges of California, and the Mt. St. Elias Range of
Alaska were either formed or else rejuvenated at that time.

Thus with every critical period there are new mountains
formed and old ones rejuvenated; new lands formed by emer-
gence of sea bottoms and old ones elevated or depressed. Thus
new constructional forms are made and a new cycle of destruc-
tional or erosive forms inaugurated. These forms pass gradu-
ally through the stages so graphically described by Professor
W. M. Davis and others, the final result being the so-called
peneplain. Of course, there are subordinate, intermediate, and
more local cycles; and therefore at the end of the great cycle

THE OZARKIAN AND ITS SIGNIFICANCE S41

we may have examples of both old and new topography. But
in any case a critical period, being the beginning of a new great
cycle, after such a period we have only or mainly new topogra-
phy. This is the true and conclusive answer to Professor Tarr’s
objection to Professor Davis’ far-reaching deductions from the
supposed discovery of the remnants of former peneplains.
Professor Tarr objects that if there be any such former pene-
plains there ought to be peneplains formed now and in the pres-
ent geological epoch—that the very foundation of geology as
an inductive science consists in the use of causes and processes
now in operation as the basis of reasoning on phenomena of
earlier times. Yes, causes and processes now in operation, but not
results and forms now existent and produced in the present
epoch. Causes and processes are constant, or nearly so, but
resulting forms pass through a regular cycle of evolution-
changes. Now the dast cycle 1s just commenced. We must wait
at least a few millions of years before we can expect to find
peneplains made out of the recently inaugurated and highly
emphasized topographic forms. Asa note of warning against
hasty generalizations Professor Tarr’s paper cannot be too
highly commended. We are all too apt to be carried away by
a new idea. It is apt to become a fashion of thought for which
we are ever seeking confirmation ; and in all complex and imper-
fectly understood questions, what we seek earnestly for we are
very apt to find. It is possible, yea, it is probable, that the pene-
plain idea has been overworked; that many of these ancient
peneplains exist only in the fervid imagination of the too ardent
seologist, Nevertheless, the: principle is a true one and
undoubtedly a very fertile one. Geological history has hereto-
fore been based almost wholly on the results of sedimentation.
It is time that it should be based also, and equally, on the
results of erosion. These results may be more difficult of inter-
pretation, but difficulties ought only to stimulate investigation.
Is the Ozarkian Tertiary or Quaternary? Finally, we are now
prepared to return to the question of place of Ozarkian in the
geological classification. After what has been said the answer

542 VOSEPTGEE GON Ls

to this question is plain. Critical periods, as I have shown in
previous papers, are the great landmarks separating the primary
divisions of geological time—the eras. They are the compara-
tively fixed points between which we correlate periods as best
we can by comparison. Now, if the Quaternary be indeed one
of these and the last, then it is evident that the Ozarkian, being
a time of great elevation and enlargement of continents, and
therefore a period of lost record, belongs par excellence to that
period. It is the most important and characteristic part, and
the part which determined the whole succession of changes
which inaugurated a new order of things, viz., Present; a new
era, viz., the Psychozoic. The Tertiary was a period of compara-
tive quiet, of gradual changes, and abundant life. The Ozarkian
commenced the series of evolutionary changes which inaugu-
rated a new era and is the most characteristic and important
epoch in the series.

That the Ozarkian belongs to the Quaternary, therefore, is
certain. But the question still remains: to what era should we
attach the Quaternary ? Upham thinks that to be consistent I
ought to put it in the Psychozoic, because man was introduced
in the Quaternary.* On the contrary, I believe it should be
allied with the Cenozoic. The Permian, too, is a_ transition.
revolutionary, critical period between the Paleozoic and Mesozoic,
But after much discussion it has been put with the Paleozoic.
The Laramie is the transition, revolutionary, critical period
between the Mesozoic and Cenozoic. Again, after long dis-
cussion, it has been put in the Mesozoic. So, also, the Quater-
nary is the transitional, revolutionary, critical period between
the Cenozoic and Psychozoic. After some discussion it will
undoubtedly be put in the Cenozoic with the Tertiary. It is
true that man, the characteristic dominant type of the Psychozoic,
was introduced in the Quaternary. But here, also, the analogy
with other critical periods holds good. A new era begins when
the readjustment and the new order is established. Reptiles
were introduced in the Permian, but the reign of reptiles did not

*Am. Nat., Vol. XXVIII, p. 980, 1894.

THE OZARKIAN AND ITS SIGNIFICANCE 543

begin until the Trias. Mammals were introduced in the Mesozoic,
and even true mammals—eutheres—probably in the Laramie,
but the reign of mammals did not begin until the Tertiary. So,
also, man was introduced in the Quaternary and possibly even
in the Pliocene, but for a long time he struggled doubtfully for
mastery with the great beasts of that time. His supremacy was
not established until after the Glacial epoch, 7. e., with the
Psychozoic.

All I insist on, however, is that the Quaternary, wherever it
is put, must all go together. It must not be split and its most
characteristic part separated and put inthe Tertiary. There may
be, indeed, some good reasons for putting it @// in the Tertiary,
and analogy will bear this out. For example, it is customary to
make three periods in the Carboniferous, viz., the Mississipian,
the Coal Measures, and the Permian, but there is a growing
tendency to unite the Permian with the Coal Measures as its
uppermost transitional stage. Again, we may divide the Mesozoic
into Triassic, Jura, Cretaceous, and Laramie, but it is more
usual and probably best to unite the Laramie with the Cretaceous
as its uppermost transitional stage. So, also, it is customary to
divide the Cenozoic into two periods, Tertiary and Quaternary,
but it may possibly be better to regard the Quaternary as the final
transitional stage of the Tertiary, and thus to divide the Tertiary
into four epochs, the Eocene, Miocene, Pliocene, and Pleistocene.
All I insist on is that its most characteristic part and that which
determined the whole series of changes characteristic of this
time should not be separated from the rest.

A PLEA FOR PSYCHOZOIC AS AN ERA.

I again take occasion to insist on the present, as the begin-
ning of a new era—the Psychozoic—separated from the Cenozoic
by the last great critical period, the Quaternary. This must
be so if the Quaternary be indeed a critical period comparable
with those that separated the previous eras. That it is such is
shown by the fact that it has all the characteristics of such
periods. It is characterized (1) by widespread oscillations of

544 JOSEPH LE CONTE

the earth’s crust; (2) by the formation or rejuvenation of great
mountain ranges ; (3) by the formation of new constructional
forms, and the inauguration of a new cycle of erosion forms ;
(4) by great climatic oscillations ; (5) by wide migrations and
minglings of faunas and floras, and fiercer struggle for life, and
rapid changes of organic forms by wholesale destruction of old
forms and evolution of new forms ; (6) by more rapid steps of
evolution, but a partial obliteration of previous geographic
diversity, and the inauguration of a new cycle of increasing
diversity ; and (7) by the introduction of a new dominant type
—man, who is now becoming more and more the great agent of
change in the new era, especially in organic forms.

There can be no doubt that we are now in the midst of a
change more sweeping and rapid than has ever before taken
place in the history of the earth, but which we imperfectly
appreciate because we are in the midst of it, and therefore lose
the perspective. Why then should we hesitate to recognize
that the present is indeed one of the prime divisions of geologi-
cal time? It is more: it is that which alone gives significance
to all that precedes.

JosErpH Le Conre.

AN ATTEMPT TO FRAME A WORKING HYPOTHESIS
OF THER CAUSE OF GLACIAL PERIODS ON AN
MUMOSERMERIC - BASIS *

THERE are hypotheses and working hypotheses. The sugges-
tion that the last glacial period was caused by the passage of the
solar system through a cold region of space may be styled a
hypothesis, but scarcely a working hypothesis in the geological
sense, for it does not form the groundwork or incentive of
geological inquiry. An astronomer might be moved to hunt
for the cold spot, but it has no inspiration for the geologist.
General suggestions of a possible cause do not reach the dignity
of working hypotheses until they are given concrete form, are
y/ fitted in detail to the specific phenomena, and are made the
' agents of calling into play effective lines of research. The con-
struction of a concrete working hypothesis suited to stimulate
and guide investigation in a wholesome manner, and to take its
place in competition with other hypotheses of like working
potentialities, thereby inducing a more searching scrutiny of
the phenomena and a more varied application of interpretations,
represents the higher limit of present reasonable aspiration. It
is much too ambitious to hope for a demonstrative solution of
the origin of the earth's glacial periods by first intention in the
present state of knowledge.

The hypothesis here offered is not worked out into satisfac-
tory detail at all points, but it is hoped that it is sufficiently
matured to justify a preliminary statement. In forming it,
which has been the work of several years, I have found, or
seemed to find, the phenomena of past glaciation intimately
associated with a long chain of other phenomena to which at

* A brief statement of the salient features of this hypothesis was given in a paper
entitled A Group of Hypotheses Bearing on Climatic Changes, Jour. GEOL., Vol.

V, pp. 653-683, Oct.-Nov. 1897. For earlier history see footnotes on pp. 654 and 681
of that paper.

545

546 T. C. CHAMBERLIN

first they appeared to have no relationship. This chain led on
and on until it became connected with many of the most funda-
mental problems of geology. When once an inquiry into the
history of the atmosphere and its possible functions in the past
was raised, there seemed no resting place until the origin of the
atmosphere — and with it the origin of the earth — was reached.
The inquiry raised profound skepticism regarding some of the
most firmly accepted doctrines of the original state of the
earth, its internal constitution, and the great dynamic forces
that have controlled the larger phases of its history. A series
of new, or partially new, hypotheses relative to these fundamental
phenomena seemed to be necessary to fill out the group of
alternative theories requisite to cover the ground of legitimate
doubt based on specific reasons for doubt. In other papers I
have given a partial expression to the hypotheses framed to
cover these points.* The exposition of these has not in all cases
been sufficiently ample to give them good working form, but
has perhaps been sufficient to show their general relationship to
an atmospheric hypothesis of glaciation.

The hypothesis here offered is confessedly connected in my
own mind with these ulterior and more fundamental hypotheses,
but it does not seem to me that it is necessarily so connected.
To be sure, if it is assumed, following a prevalent custom of the
past, that the original atmosphere was a vast gaseous envelope
embracing essentially all the carbonic acid that is now locked
up in limestone and other carbonates, and all that is represented
by coal and other carbonaceous matter, and that the atmospheric
history has been essentially a progressive depletion of this origi-
nal supply, I do not see how the proposed hypothesis can be
entertained, at least for the earlier glaciations. But if it be

tA Group of Hypotheses Bearing on Climatic Changes, Jour. GEOL., Vol. V,
No. 7, 1897. The Ulterior Basis of Time Divisions and the Classification of Geologic
History, zd2d., Vol. VI, No. 5, 1898. A Systematic Source of Evolution of Provincial
Faunas, 7bzd., No. 6, 1898. The Influence of Great Epochs of Limestone Formation
upon the Constitution of the Atmosphere, z/¢¢, Lord Kelvin’s Address on the Age
of the Earth as an Abode Fitted for Life, Science, N. S., Vol. [X, No. 235, pp. 889—
901, June 30, 1899, and Vol. X, No. 236, pp. 11-18, July 7, 1899.

WVPOITE STS (OF (CACSE.OF GLACTAL PERIODS 547

assumed that as early as Paleozoic times the atmosphere had
some such constitution as it possessed in later geological times,
and that its history has been a contest between the agencies
of atmospheric supply and the agencies of atmospheric deple-
tion, and that the constitution of the atmosphere at any time
has been dependent upon the relative rates of supply and deple-
tion, then the hypothesis may be entertained quite independ-
ently of all views of the origin of the earth and the atmosphere
and of internal dynamics.

Previons advocacy of an atmospheric hypothesis.—The general
doctrine that the glacial periods may have been due to a change
in the atmospheric content of carbon dioxide is not new. It
was urged by Tyndall a half century ago and has been urged by
others since. Recently it has been very effectively advocated
by Dr. Arrhenius,’ who has taken a great step in advance of his
predecessors in reducing his conclusions to definite quantitative
terms deduced from observational data.* The great labor
involved in this and the specific results springing from it place
his contribution on a much higher plane than the general sug-
gestions of those who had preceded him. Valuable as these
general suggestions were, they must still be regarded as falling
much short of working hypotheses, since no attempt was made
to show that changes in the content of carbon dioxide of such
a degree as would be compatible with the continuity of life and
with other limiting geological conditions were quantitatively
competent to produce the effects assigned them; nor were
modes of inquiry into this essential matter suggested. It is one
thing to point out a theoretical causa vera, and quite another
thing to give good reasons for believing that it is quantitatively
sufficient, and to open lines of inquiry for demonstrating that it
is so. This Dr. Arrhenius has done and apparently with great
success. While his results are doubtless to be regarded as sub-
ject to modification when more full and exact data are at hand,

tOn the Influence of Carbonic Acid in the Air upon the Temperature of the
Ground, by SVANTE ARRHENIUS, Phil. Mag., April 1896, pp. 237-276.

2 See review of his paper in this number of the JOURNAL, p. 623.

548 TEC CLLANMIB TRIE IN,

it is apparent upon inspection that they can be very largely
modified and still fall within the limits of the conditions of the
case. This will perhaps appear more evident in the course of
the subsequent discussion. In so far as the deductions of
Arrhenius and the accompanying views of Professor Hégbom *
fail to definitely postulate operative geological agencies compe-
tent to produce the requisite variations in the constitution of the
atmosphere, and to give reasons for believing that such agencies
were in operation at the times requisite to produce the effects
assigned them, they fall short of furnishing an ample working
hypothesis from the geologist’s point of view. This, of course,
is the function of the geologist rather than the chemist and the
physicist. Professor Hégbom has made a valuable contribution
to the general doctrine of consumption and supply.

To form a good working hypothesis in a geological sense, it
is furthermore necessary to assign subsidiary agencies working
in an oscillatory manner correspondent with the oscillations of
glaciation now so well authenticated by observation.

Specttic requisites of a working hypothesis.—It is obvious that
it is necessary at the outset to assign agencies capable of reduc-
ing the amount of the carbon dioxide of the atmosphere at the
time of the glaciations. If there were no other glaciation than
that of the Pleistocene period, and if there were no kindred
phenomena needing to be elucidated at the same time, it might
be sufficient to point to the well-known abstraction of carbon
dioxide from the atmosphere in the formation of limestones and
carbonaceous deposits, and there rest the case, with the impli-
cation that further production of limestones and carbonaceous
deposits would insure further glaciation, and that the permanent
and final winter of the earth is at hand. A very slight compu-
tation of the rate at which carbon dioxide is now consumed is
sufficient to show that an effective depletion of the atmosphere
is near at hand unless there be sources of supply approximately
equal to the depletion. But recent depletion touches only the

1 SVENSK KEMISK TEDSKRIFT, Bd. VI, p. 169 (1894). Quoted in Dr. Arrhenius’s
paper, p. 269.

WNMPOLMESTS OF “CAUSE OF GLACIAL PERIODS 549

easier part of the problem. Whatever may be thought of the
supposed signs of cold periods at other early periods, the evi-
dences of glaciation in India, Australia and South Africa near
the close of the Paleozoic era are so abundant, so specific, and
so well attested, that they cannot be ignored, and any hypothe-
sis that assumes to account for glacial periods must take serious
cognizance of these and must meet the strenuous issues that
spring from their early age and from the mildness of the periods
following them. It seems to the writer almost equally necessary
to take cognizance of the salt and gypsum deposits of various
periods, which imply degrees of aridity in relatively high lati-
tudes scarcely equaled at the present day. If the atmospheric
line is followed, it seems necessary to postulate a reduction of
carbon dioxide near the close of the Paleozoic era—to say
nothing of other early times — so effectual as to produce glacia-
tion between 20° and 35° latitude on both sides of the equator,
a glaciation the deposits of which aggregate a greater thickness
than those of Pleistocene times, and whose oscillations, marked by
thick accumulations of coal, were even more remarkable than
those of the Pleistocene glaciation. If a depletion of the carbon
dioxide of the atmosphere sufficient to produce this glaciation
at this relatively early stage in geological history is postulated,
it is necessary to assign agencies for the reénrichment of the
atmosphere in carbon dioxide to account for the mild climates
in high latitudes in Jurassic, Cretaceous, and Tertiary times. In
short, it is necessary to assign competent operative geological
agencies which shall produce effective depletion alternating with
effective reénrichment of the atmosphere from an early period
in its history down to the present time. If the salt and gypsum
deposits, and the prevailing red beds, with arkose elements, be
regarded as the products of exceptional aridity, and if this be
assigned to the localization and intensification of heat and mois-
ture due to the removal of carbon dioxide, as subsequently set
forth, it is necessary to multiply the oscillations from enrich-
ment to depletion very notably, and to extend the alternating
action at least as far back as the close of the Silurian period

550 T. C. CHAMBERLIN

when the great saline deposits of New York, Ontario, Ohio,
Michigan and adjacent regions were laid down.

Primary assumptions— (1) It is therefore assumed as the
working basis of the hypothesis that the carbon dioxide of the
Paleozoic atmosphere was at certain stages not essentially greater
than it is today, that at the specific epochs of great saliferous
deposition and of glaciation it was reduced to a quantity notably
less than the present content, while at other and intervening
stages its amount exceeded the present content by some multiple
—these latter periods being those in which the wide extension
of marine epicontinental life took place. For myself, I am dis-
posed to extend the assumption of a measurably limited atmos-
phere back to the very beginning. To this I am led in part by
the conviction that the gravitation of the earth is incompetent to
hold an atmosphere very greatly beyond the amount so assumed,
and by the much more speculative consideration that the earth
may have grown up by slow accretion rather than rapid concen-
tration, and that hence the early development of the atmosphere
was controlled by limitations much like those that have affected
it in its later history. But, as already remarked, this assump-
tion is not regarded as vital to the hypothesis. (2) Wrapped up
in the foregoing postulate is an assumption of the essential
correctness of the doctrine of Arrhenius that variations of the
atmospheric carbon dioxide falling within limits compatible with
life and with other geological phenomena, are competent to
effectively change the thermal state of the atmosphere. This
needs further statement.

The functions of carbon dioxide.— By the investigations of Tyn-
dall,t Lecher and Pretner,? Keller,3 Roentgen, and Arrhenius,5 it

* Heat as a Mode of Motion, 6th ed., pp. 345-349, 1892. Contrib. to Mol. Physics,
pp. 38. 117, 421, 1888.

2 Sitzungsberichte des Akad. der Wissenschaften d. Wien (2). Vol. LX XXII, p.
851 (2), Vol. LXXXVI, p. 52.

3Am. Jour. Sci. (3), Vol. XXVIII, p. I90.

4 Poggendorfs Annalen (2), Vol. XXIII, p. 1259.

5 Phil. Mag., Vol. XLI, pp. 237-279.

A brief statement of the conclusions’ of these authors is given in the article of Mr.
Tolman in this number, p. 586. See also his review of Dr. Arrhenius, p. 623.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 551

has been shown that the carbon dioxide and water vapor of the
atmosphere have remarkable power of absorbing and temporarily
retaining heat rays, while the oxygen, nitrogen, and argon of the
atmosphere possess this power in a feeble degree only. It fol-
lows that the effect of the carbon dioxide and water vapor is to
blanket the earth with a thermally absorbent envelope. Their
absence would leave the surface of the earth essentially exposed
to the free impact and free radiation of the solar rays, measura-
bly, though of course not entirely, as if the earth were devoid of
atmosphere. A reduction or an increase in these constituents
would produce corresponding partial effects. The general
results assignable to a greatly increased or a greatly reduced
quantity of atmospheric carbon dioxide and water may be sum-
marized as follows :?

a. An increase, by causing a larger absorption of the sun’s
radiant energy, raises the average temperature, while a reduction
lowers it. The estimate of Dr. Arrhenius, based upon an elabo-
rate mathematical discussion of the observations of Professor
yLangley, is that an increase of the carbon dioxide to the amount
of two or three times the present content would elevate the
average temperature 8° or g° C. and would bring on a mild cli-
mate analagous to that which prevailed in the Middle Tertiary
age.* On the other hand, a reduction of the quantity of carbon
dioxide in the atmosphere to an amount ranging from 55 to 62
per cent. of the present content, would reduce the average tem-
perature 4° or 5° C., which would bring on a glaciation compa-
rable to that of the Pleistocene period.

The amount of moisture in the atmosphere, other things being
equal, is directly dependent upon the temperature, and the tem-
perature in turn is dependent upon the amount of moisture in
the atmosphere. This reciprocal dependence renders the aqueous

t The action has two phases that in an exhaustive exposition would need separate
statement, (1) the absorption of solar rays before they reach the earth, and (2) the
absorption of the rays radiated by the earth. The latter have longer wave-lengths on

the average and are relatively much more affected by the constitution of the atmos-
phere.

2 Dr. Arrhenius, loc. cit.

552 TL AG GLLANMIBIETALETN,

vapor a vacillating factor subject to the control of any other
agency which increases or decreases the atmospheric temperature.
Whenever therefore an increase of carbon dioxide raises the
temperature, it increases the quantity of water vapor and this by
its thermal absorption further increases the temperature and
calls forth more vapor and this action and reaction continue in
diminishing force until an equilibrium is established. A decrease
in carbon dioxide decreases the temperature and thus lessens the
water vapor, and this further lowers the temperature and inaugu-
rates a reversed series of actions and reactions. Fluctuation in
the quantity of carbon dioxide therefore is attended not simply
by its own individual effects, but by these auxiliary effects also.
The carbon dioxide becomes therefore the determinative factor,
and the question of the thermal absorption of the atmosphere
may be discussed for convenience as though it were solely
dependent upon the fluctuations in the content of this con-
stituent, although this will not be strictly exhaustive.

6. A second effect of increase and decrease in the amount
of atmospheric carbon dioxide is the equalization, on the one
hand, of surface temperatures, or their differentiation on the
other. The temperature of the surface of the earth varies with
latitude, altitude, the distribution of land and water, day and night,
the seasons, and some other elements that may here be neglected.
It is postulated that an increase in the thermal absorption of the
atmosphere egualizes the temperature, and tends to eliminate the
variations attendant on these contingencies. Conversely, a
reduction of thermal atmospheric absorption tends to zntenszfy all
of these variations. A secondary effect of intensification of
differences of temperature is an increase of atmospheric move-
ments in the effort to restore equilibrium. Increased atmos-
pheric movements, which are necessarily convectional, carry
the warmer air to the surface of the atmosphere, and facilitate
the discharge of the heat and thus intensify the primary effect.
In the case of a naked earth, the radiant energy of the sun fall-
ing directly upon the tropical belt is concentrated in space, and
subject to the minimum reflection; in high latitudes, the rays

FV POTHESES: OF CAUSE OF GLACIAL PERIODS 553

are spread over greater space, and are subject to greater relative
reflection because of the low angle of incidence. In the case of
an earth swathed in a thermally absorptive mantle, the direct
equatorial ray is absorbed in traversing the atmosphere to a less
extent than the ray of higher latitudes because it penetrates a
less depth of atmosphere, while the amount of reflection from
the atmosphere is small in both cases, so far as the transparent
elements are concerned. In so far therefore as the temperature
effects are dependent upon the absorption of the incoming rays,
the greater depth of atmosphere penetrated in the higher lati-
tudes makes important compensation for obliquity of incidence.

In the case of a naked earth, or an earth clothed with a non-
absorptive atmosphere, the solar rays which are tangential to the
polar regions have no heating influence upon the earth, while in
the case of an earth clothed with an absorbent atmosphere, simi-
lar rays are partially absorbed, and serve to warm the earth. In
the polar regions, therefore there is a very radical difference
between the effects of an absorbent and a _ non-absorbent
atmosphere. The same holds true of the heating effects of the
morning and evening sun. With a non-absorbent atmosphere,
the tangential morning and evening rays pass through and are
lost; in a thermally absorbent atmosphere, they are effectually
retained.

In so far as the incoming rays are absorbed in the atmosphere
their immediate effects are chiefly felt in its upper strata and their
influence upon the surface of the earth is lessened. This is due to
the fact that the upper regions are penetrated by rays of all the
various wave-lengths that emanate from the sun, while the lower
portions are penetrated only by such rays as are left after the
selective absorption of the upper atmosphere. The degree of
this absorption of the rays of long wave-lengths is such that com-
paratively little further absorption takes place in the basal por-
tion of the atmosphere, according to the interpretations of
Arrhenius. One effect of increasing the absorptive capacity of
the upper air by increasing the amount of carbonic acid is an
increase in the elevation of the strata chiefly heated by the

554 T. C. CHAMBERLIN

incoming rays and the consequent reduction of the thermal
gradient of a vertical column of the atmosphere. As a result
there is less effective tendency to convection and less discharge
of heat from the atmosphere.

In high latitudes, besides this effect, it is also to be noted
that with an increase of the absorptive capacity of the upper
atmosphere, rays that previously passed through the higher strata
with little absorption are arrested and contribute heat to the
upper air. The same is true of morning and evening rays at high
elevations.

In the case of the outgoing rays, which are absorbed in much
larger proportions than the incoming rays because they are more
largely long-wave rays, the tables of Arrhenius* show that the
absorption is augmented by increase of carbonic acid in greater
proportions in high latitudes than in low; for example, the
increase of temperature for three times the present content of
carbonic acid is'21.5 per cent. greater between 60° and 70° N.
latitude than at the equator. The maximum thermal effects
also lie in higher latitudes for the summer months than for the
winter months. On the other hand, when the carbonic acid is
reduced to 0.67 of the present content, the maximum winter
variation is felt between 30° and 4o° N. latitude. If the car-
bonic acid be further reduced, the maximum variation found by
extrapolation falls at and below 30”, the latitude of the Carbon-
iferous glaciation. It is not intended, however, to imply that
this would be sufficient in itself to produce that glaciation.

An atmosphere having a relatively large percentage of carbon
dioxide and water, 7. ¢., an absorptive atmosphere, has a higher
heat content than a non-absorptive one, and its circulation in
latitude more effectually equalizes the temperature with the same
degree of movement.

Similar considerations are applicable to the effects of land
and water areas. In so far as the atmosphere absorbs the incom-
ing rays in passing through it, the amount that reaches the sur-
face of the earth is reduced. To this extent the possibility of

~IZOC. cit., Pp. 200:

I

HVPROLTHESTS“OFSCAUSE OF GLACIAL PERIODS. 555

differential effects between the sea and land is lessened. On the
other hand, in the absence of absorptive and diffusive effects, the
tropical rays fall with full intensity upon the surface. On the
land they promptly heat the immediate surface, and the heat is
as promptly radiated away. On the sea, neglecting reflection,
they penetrate deeply into the water until they are absorbed.
The upper layer of the sea is therefore heated to a notable depth,
and radiates its heat away with relative slowness. The result is
‘an intensification of the differences in average temperature of
the land and the sea. This action is quite familiar, but perhaps
not the point here urged—that this difference is dependent on
the atmospheric effects upon the incoming as well as outgoing
rays. If the atmosphere were so far robbed of its absorbent
factors, carbon dioxide and water, as to give great intensity to
this differential effect, the result might be an average tempera-
ture of the land below the freezing point, while that of the sea
might be relatively warm. It seems clear that at some point
short of an absolute thermal transparency a stage would be
reached where the average temperature of the land would sink
below zero, while yet the sea, barring convection in latitude,
would retain a comparatively mild temperature. There would
then apparently arise, even in low latitudes, the conditions of
glaciation.

Without following out these lines into greater detail, the
more pertinent deductions may be summed up in the following
propositions: A reduction of the thermal absorption of the
atmosphere would intensify the differences of temperatures
/ between (1) the basal and the upper portions of the atmosphere ;
(2) low and high latitudes; (3) land and sea; (4) night and
day; and (5) the seasons. In short, it would intensify tempera-
ture differences generally, and would lead to (1) greater local
heat, as well as greater local cold; (2) to greater local dryness,
as well as greater local moisture; (3) to more intense move-
ments of the atmosphere in the endeavor to maintain equilibrium ;
and (4) to lower average temperature. The effect of reducing
the absorbent factors is the intensification of differences.

556 T. C. CHAMBERLIN

On the other hand, an increase in the absorptive factors renders
ineffectual, in a corresponding degree, the variations of altitude,
of latitude, of land and sea, of day and night, and of the seasons,
and conduces to an equable and mild temperature, to gentle and
yet thermally effective circulation, and to higher average tem-
perature. As Arrhenius has remarked, “ The geographical,
annual, and diurnal changes of temperature would be partly
smoothed away if the quantity of carbonic acid was augmented.
The reverse would be the case (at least to a latitude of 50° from

yy

the equator ) if the carbonic acid diminished in amount.

AGENCIES OF DEPLETION AND ENRICHMENT

It now becomes necessary to assign agencies capable of remov-
ing carbon dioxide from the atmosphere at a rate sufficiently
above the normal rate of supply, at certain times, to produce gla-
ciation; and on the other hand, capable of restoring it to the
atmosphere at certain other times in sufficient amounts to pro-
duce mild climates. :

These agencies on both sides belong to two classes, the per-
manent and the temporary, and the distinction has practical
importance.

Sources of permanent loss — Permanent depletion results from
the consumption of carbon dioxide in the transformation of the
silicates of the original earth, and of volcanic products into the
carbonates of the secondary strata. It is fairly safe to assume
that the original earth’s surface was composed of material of the
general class represented by the igneous rocks and the basement
complex. These, it is needless to say, consist largely of silicates
with which are associated certain quantities of certain gases to be
considered more fully hereafter. These silicates, where exposed
to the weathering action of the atmosphere, become decomposed
and take the form of carbonates (with less quantities of sul-
phates, phosphates, etc.) and of residual silicates and oxides
(kaolin, quartz, ferric oxides, etc.). Neglecting the minor trans-
formations which do not concern us here, the operation may be

TUE OC CIE pes 205:

HVPOTHESTS OF “CAUSE OF GLACIAL PERIODS 557

characterized as carbonation, and consists essentially of the sub-
stitution of carbonic acid for the silicic acids. The carbonic
acid is derived, in the main, from the atmosphere. In their
soluble condition, the carbonates so formed are largely bicar-
bonates. This is the only form in which calcium carbonate is
appreciably soluble, and the same is true in a less degree of mag-
nesium carbonate. The monocarbonates of potassium and sodium
are highly soluble, but the bicarbonates also appear in solution.
Practically the carbonates of these alkalis usually become
changed into other salts (sulphates, chlorides, etc.) and the car-
bon dioxide that may have been temporarily locked up with
them is set free by the change, or enters some other combina-
tion. The magnesium and calcium carbonates are also in part
changed to other salts. But for the purposes of this discussion,
which is concerned chiefly with the final issue and not with the
transient stages of these compounds, it is sufficient to note that
the chief result of the decomposition of the original silicates is
the formation of calcium and magnesium carbonates, which are
deposited as limestones and dolomites and thus lock up carbon
dioxide at the expense of the atmosphere. The amount so taken
from the air in the known geological periods has been variously
estimated at from 20,000 to 200,000 times the present content ;
indeed estimates have gone beyond the last figure. When it is
considered that 44 per cent. of all pure limestone and a higher
per cent. of all pure dolomite is carbon dioxide, it 1s obvious that
the total quantity is very large, and its computation is dependent
upon the estimate of the total amount of limestone and dolomite
IMthe crust Of, the: earth,

A second source of permanent loss consists of the consump-
tion of carbonic acid by plants and the fixation of the carbon in
carbo-hydrates, hydro-carbons and other carbonaceous compounds
which ultimately take the form of coals, bitumens, oil, gas, and
perhaps most important of all, disseminated organic matter in
the sedimentary series.

Exceptions—Some hydro-carbons have probably been pro-
duced by inorganic action, notably those derived from carbides

558 T. C. CHAMBERLIN

-(Moissan) formed within the earth and extruded from it. Some
carbonates probably have been formed by carbonic acid con-
tained within the rocks or extruded from the interior. In cer-
tain phases of the problem, deduction is to be made for such
carbonaceous compounds and carbonates as are formed in the
sea by marine plants and other agencies which derive their
carbonic acid from the sea water; but in the general discussion
of the question, the carbonic acid of the sea must be reckoned
in with the carbonic acid of the air, for the two are in equi-
librium and constitute essentially and potentially one body.
The necessity for this assumption will be more obvious when we
come to discuss the function of the ocean in influencing the con-
stitution of the atmosphere.

Sources of permanent gain.— Over against these sources of
secular loss there are certain sources of gain. If the assump-
tion that the constitution of the atmosphere has varied through
only moderate limits within the known ages be adopted, it is
necessary to postulate sources of supply of a competency approxi-
mately equal to the sources of loss. The data for such postu-
lation are exceedingly unsatisfactory and a function of the
hypothesis should be to stimulate investigation in these lines
which have been barely touched by serious inquiry.

a. Gain from the interior— The crystalline rocks of the sur-
face of the earth have been shown by the recent examinations
of Tilden* to contain very notable quantities of gas, consisting of
hydrogen in preponderance, carbon dioxide and carbon monoxide
in large percentages, and nitrogen and marsh gas in small quan-
tities, with water vapor, but with a practical absence of oxygen.
Twenty-five analyses, including ancient and modern volcanic and
even some metamorphic rocks, gave an average volume of gas
equal to about four and a half times the volumes of the contain-
ing rocks. A computation on this basis shows that an atmosphere
equivalent in mass to the present one would be contained in a
very superficial rind of the earth, and that if this volume of

*On Gases Contained in Crystalline Rocks and Minerals: W. A. TILDEN,
Chemical News, April 9, 1897.

HYVPOTMESTS OF CAUSE {OF GLACIAL PERIODS 559

included gases be constant for the whole body of the earth, it
contains potentially a multitude of atmospheres.

It is a familiar fact that enormous quantities of gases are
ejected from volcanoes during their active periods. It has been
very generally assumed that these gases and vapors, among which
steam vastly preponderates, have a surface origin, and there can
be no doubt that this is true of some notable part; but, on the
other hand, there is abundant ground for the belief that another
notable part is brought from the interior and is a real contribu-
tion to the earth’s atmosphere and hydrosphere. It may not be
possible at present to demonstrate this, but inquiry in this
direction is invited. There seem to be no means of estimating
from present data even approximately the volume of gas which
is given forth, but it is certainly large. There are grounds for
believing that the gases of the interior escape by other than
volcanic vents. The deep rending and sharp shock of the earth
in seismic movements, the stresses and fissuring of readjustments,
the disintegration of crystalline rocks, and the resources of slow
diffusive penetration are among these. So far as the setting free
of carbon dioxide by decomposition of the containing rock is
concerned, it is to be noted that the chemical action which sets
it free involves a consumption of carbon dioxide very greatly in
excess of the amount liberated, so that, as computation will
show, the total effect of the process is one of loss which the
internal gases only very slightly modify. This, of course, is not
true of mechanical disintegration.

b. Exterior sources of gain The meteorites which are con-
stantly falling to the earth contain included gases, often in great
volume. They also contain carbonaceous matter which is par-
tially burned in passing through the air. The nature of the
included gases is notably similar to those of the crystalline
rocks, hydrogen and carbon dioxide being the leading constitu-
ents with nitrogen in very subordinate amount and free oxygen
essentially absent... Water vapor appears in both meteorites and

™See numerous papers of A. W. WRIGHT in Am. Jour. Sci., notably Gases con-
tained in Meteorites, Am. Jour. Sci, 3d series, Vol. XII, No. 69, Sept. 1876.

560 T. C. CHAMBERLIN

crystalline rocks, but it is impossible to say how far it was
absorbed from terrestrial sources. It has even been suggested
that all the gases both of meteorites and of the crystalline rocks
were simply absorbed from the air and not brought in from with-
out; but their proportions are so different from those of the
air that it would be necessary to assume an extraordinary
selective power to make this possible ; for oxygen must be wholly ~
rejected as a gas; nitrogen, though greatly preponderant, must
be almost neglected ; carbon dioxide must be absorbed in great
quantities relatively ; carbon monoxide, though very rare in the
atmosphere, must be taken in abundantly; while the hydrogen,
which is scarcely detectable in the atmosphere, must be absorbed
in superlative amounts. It is difficult to conceive how a mete-
orite passing rapidly through the air can have absorbed many
times its volume of an element which does not appear in the air
in detectable quantities. However, I am unable to say that the
analyses were made sufficiently soon after the fall of the mete-
orites to make this point conclusive. But, at any rate, the
hypothesis of selective absorption is confronted with grave
difficulties and the alternate hypothesis that the gases are
brought to the earth in the meteorites seems the more probable.
The emanations from comets support the view that meteorites
are charged with gases in extra-terrestrial regions. Here again
inquiry is needed and experimental tests are obviously sug-
gested.

If gases are brought in with meteorites, it is probable that
independent molecules are flying through space and are caught
up by the earth. The modern doctrine of molecular velocities,
which holds that gases are liable to escape, and presumably are
escaping constantly, from planetary bodies, carries the presump-
tion that individual molecules are flying through space with some
degree of frequency. Astronomical phenomena, to be sure, seem
to indicate that the quantitative value of these cannot be very
great, but as definite data are yet wanting and we are dealing
with vast lapses of time and slow processes of depletion, making
need for slow processes of accretion only, this agency may

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 561

deserve a place among the undetermined sources of atmospheric
material.

It is among the possibilities that the sun itself may be a direct
source of atmospheric feeding. The speed at which the solar
prominences are projected from the sun has been observed to
exceed the parabolic velocity of the sun;" that is, the rate of
projection is such that if the outer atmosphere of the sun does
not effectually interfere, the gases are shot away beyond even
the sun’s control. A much less speed could carry the gases to
the earth, so that, unless the outer atmosphere of the sun inter-
poses effectual barriers, it is not improbable that gases are
thrown as far out as the orbit of the earth. The earth probably
cannot hold hydrogen, the chief gas of these prominences,
permanently as such, but it may do so when combined with oxy-
gen. The shooting of solar hydrogen through our atmosphere
would lead to the formation of water, because, even at ordinary
temperatures, such of the molecules of oxygen and hydrogen as
collided with the requisite velocity would enter into union.
There seem therefore grounds for placing this among the possi-
ble but undetermined sources of supply for our atmosphere and
hydrosphere. When the mystery of the zodiacal light and the
gagenshein shall be solved, it is possible that demonstrative
evidence of our relations to the extreme projections of the solar
atmosphere may be available.

In the present state of extreme uncertainty relative to all
these possible sources of supply, a hypothesis which necessarily
involves them proceeds with uncertain steps and must perforce
wait patiently for more definite determinations, but the pressing
of a hypothesis which lays emphasis upon them is but giving
effect to the fundamental mission of all working hypotheses.

VARYING RATES OF ACTION

By the terms of the hypothesis the state of the atmosphere
at any time is dependent upon the relative rates of loss and gain.

tThe Story of the Sun, by SiR RoBERT BALL, pp. 185-188; The New Astronomy,
LANGLEY, p. 61.

562 LT. 6 CHAMBERETN,

It is of supreme importance therefore to consider irregularities
in the action of the sources of loss and gain.

Varying rates of gain—The constancy or irregularity of the
sun’s contribution—assuming it to make a recognizable contri-
bution—is quite unknown. It would presumably be dependent
upon the internal explosive action of the sun concerning which
all thought is as yet highly speculative. So far as its relations to
geological periods are concerned, it would probably be either an
essentially constant factor or one which would not fall in syste-
matically with any special phase of geological progress, and
could not be regarded as a codperative factor in any definite
phase. It might be progressively increasing, as the sun concen-
trates, or progressively diminishing.

Much the same is to be said with regard to possible sources
of supply from meteoric and similar extra-terrestrial sources.

The extrusion of gases and vapors from the interior has been
presumably periodic, because the conditions of molten eruption
and of mechanical disruption have probably been periodic rather
than constant. No specific determination of the periodicity of
volcanic action has yet been made out, but the testimony of
present geological data is to the effect that vulcanism has been
more frequent and intense at certain periods than at others.
This is clearly true for individual grand divisions of the earth,
and seems to be true of the earth at large, notwithstanding the
fact that vulcanism was a more or less local phenomenon. While
a definite periodicity, specifically connected with other phe-
nomena, cannot now be affirmed, the tentative proposition that
vulcanism has been more abundant in great periods of readjust-
ment than in periods of quiescence may be entertained. The
connection with those periods seems sometimes to have been
very intimate and immediate, and at other times more remote.
So far as disruption of the rocks constitutes a means of escape
for internal gases, there should obviously be a close connection
with periods of readjustment. In a rather general and uncertain
way, then, it would seem necessary to assume, in a working
hypothesis, that the enrichment of the atmosphere from internal

HVPOTHESTS OF CAUSE OF GLACIAL PERIODS 563

sources has proceeded more rapidly at or about the periods of
crustal disturbance. This, as we shall see, coincides practically
with the periods of depletion from atmospheric action on the
surface, and hence, so far forth, the two processes tend to neu-
tralize each other and preserve the constancy of the earth’s
atmosphere. The hypothesis must therefore recognize that it
was only when one agency fell behind the other in its com-
petency that its specific results became manifest, and then only
by the difference in their respective effects.

Varying vates of loss.—The rate of chemical action of the
atmosphere on the surface of the rocks is believed to have been
intimately connected with the extent and height of the land area,
considering the earth as a whole. There were qualifying con-
ditions, as we shall see, but notwithstanding, this is regarded as an
important law. It is madea fundamental postulate of the hypoth-
esis, and the vitality of the hypothesis as a working instrument
of investigation hangs very largely upon it. It is obvious that
theyereater the suriace-area of rock exposed ‘to the effective
action of the atmosphere, the more rapid will be the rate of
disintegration, other things being equal, and the more rapid the
consumption of carbon dioxide. *

The rate of carbonation of the rock is dependent upon
elevation as well as superficial area. The disintegration of rock
is the most active by far in the zone lying between the surface
and the level of permanent underground water, technically the
water table. It is in this zone that the atmosphere and the
moisture of the earth combine to give the greatest chemical

t Oxygen is also consumed in the decomposition of average rock, but in less
amount than carbonic acid, and as the amount of oxygen in the air is very much
larger than that of carbon dioxide, the part consumed is far less critical. In an
exhaustive study of the constitutional history of the atmosphere, the loss and gain of
oxygen must be considered, and certain very interesting and important phases of
atmospheric variation are probably connected with the production and consumption
of the oxygen, but, as indicated, they are much less immediate and critical in the
consideration of thermal problems with which our hypothesis is more especially con-
cerned, and for the sake of simplicity the oxygenation of the rocks may be tempora-

rily neglected; and for like reasons the many minor reactions may also be ignored
and attention confined to the carbonation.

564 ll... €. CHAMBERLIN

activity. It is established by the most ample observation in
mining, that below the permanent water level disintegration has
made slow progress compared with that in the zone above the
water level. Now the thickness of the zone between the surface
and the permanent water level is intimately dependent upon the
general altitude. Ina continent reduced approximately to base
level, this zone is exceedingly thin. Ina region much elevated and
deeply dissected by erosion, the thickness of the zone is very
much greater. As between a continent with an average eleva-
tion of 2000 feet, at the climax of dissection following a crustal
readjustment, and a continent of similar area with an average
elevation of 300 feet, during a period when it is approximately at
base level, the average depth of the aérated zone above the
water level, probably varies more nearly with the square of the
elevation than as a direct multiple of it. It is improbable, how-
ever, that the chemical action is augmented at so great a ratio.
Probably greater warmth and more abundant vegetation are
correlated with the lower altitudes, and both these aid chemical
action. This in turn is somewhat offset by the greater mechan-
ical disaggregation which results from changes of temperature
and from gravitative influence in the more elevated condition.
Making all allowances that seem required for the offsetting
factors, it would still appear that the elevated condition
increases the activity of decomposition in a very notable degree.

Below the permanent water level, the advantage probably
also lies greatly with the higher elevation. The action of sur-
face water upon the deeper rock is dependent upon the unbal-
anced hydrostatic pressure which promotes underground
circulation and forces the water through the crevices and pores
of the rock. If the underground water stands near sea level,
there is little unbalanced hydrostatic pressure to promote active
circulation and thereby carry the surface waters, enriched with
atmospheric gases, down into the lower strata and bring them
into action. The atmospheric waters precipitated upon the
surface run away chiefly at the surface, and fail of the contact
necessary for action. On the other hand, in an elevated region

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 595

there is a potential hydrostatic pressure measured by the differ-
ence of altitude of the surface of the ground water and the
surface of the sea which tends to cause the waters to flow
through the rock and thus find a tortuous way to the equilibrium
of the sea level. A deep underground circulation is therefore a
function of high altitude, and, correlated with that circulation,
is chemical activity proportionate to the enrichment of the sur-
face waters with chemically active agencies, in the present
instance, carbon dioxide in particular. This deeper circulation,
correlated with hydrostatic pressure, is enhanced by the greater
degree of fissuring of the rock which attends elevated tracts, for
in the process of elevation, writhing and cracking are notable
incidents, and, in addition to this, the gravitative tensions which
necessarily attend an elevated position lend their aid in the pro-
duction and opening of crevices. Precisely the opposite con-
ditions prevail at low levels. The protruding superficial portion
of the land is the most fissured part and when it has been cut
away by erosion the basal remnant is normally less open to the
penetration of water. It would appear from a consideration
of these several associated influences that disintegration and
decomposition are facilitated by elevation in a very important
degree.

If, therefore, there were times in the history of the earth
when there were general readjustments of its bodily form to
accumulated internal stresses, resulting in extensive elevations,
embracing not only the formation of mountains and plateaus,
but the general warping outwards of the continental platforms,
and the bowing downwards of the ocean basins, attended by the
withdrawal of the sea, so that the land area was extended and,
at the same time its average elevation increased, and a portion
of it rent and crushed, it is believed that the carbonation of the
rocks must have been accelerated by some notable multiplier
and that the rate of consumption of the carbon dioxide of the
atmosphere must have been correspondingly promoted; and
this is made an important postulate of the hypothesis.

At least two periods of such very general and notable

566 TNC ACGHAMBERLITN

elevation appear to be well authenticated by present geological
data, imperfect as they are for certain quarters of the earth.
These periods occurred near the close of the Paleozoic and of the
Cenozoic eras respectively. Closely connected with these two
periods are two well authenticated glacial periods.

If, on the other hand, there were periods of prolonged
quiescence of the earth’s body during which the lands were cut
down well towards base level, they would be accompanied by a
progressive slackening of the rate of disintegration, and a corre-
sponding reduction in the rate of atmospheric loss of carbonic
acid, giving opportunity for the agencies of repletion to over-
take and surpass the agencies of depletion. It is believed that
there was a series of such periods among which the Cretaceous
is best authenticated.

During a prolonged period of relative quiescence the
encroachment of the coast lines upon the land, if elevated,
becomes notable. In addition to this, the material removed
from the land and deposited in the sea raises the water level,
and when the degradation is notable this rise amounts to an
appreciable factor. This aids the coast action by lifting it
above the restraining influences of its own products, which, by
shoaling the water off shore, tend to break the force of wave
action. The notion is also entertained that during periods of
readjustment the continental masses are apt to be lifted beyond
the plane of perfect isostatic equilibrium, and that there follows
a tendency to slowly creep back into equilibrium, accompanied
by a general tendency of the continental platform to flatten out
under gravitative stress. The continental platforms are to be
regarded as having elevations above the abysmal ocean bottom
of perhaps 12,000 feet, and, as their average gravity is two and
a half to three times that of the water which surrounds them,
there remains a large excess of gravitative stress tending to
cause the continents to spread laterally.

The combined effects of these agencies is a transgression of
a thin edge of the sea upon the land. Now, such extensive
transgression took place on all the great continents in the Upper

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 567

Cretaceous period, and this fact may be taken as indicating that
the planation which reached so pronounced an expression on
the American continent at that period affected nearly or quite
all the continents in some similar measure. An inspection of
the whole range of geological history shows periods of similar
transgression accompanied by the development of luxurious and
cosmopolitan marine faunas of the shallow-water type which in
themselves imply the conditions here postulated.’

If this be a correct view it is obvious that at such periods
the areas of land exposed to atmospheric action were notably
reduced by sea encroachment, and that at the same time the
lowness of the land greatly limited the depth of atmospheric
activity by reducing the zone between the surface and the water-
table and by reducing the hydrostatic penetration of surface
waters. As already remarked, there is to be counted in offset
probably warmer temperature, a higher degree of moisture, and
a more abundant vegetation, but it is not believed that this
approaches, even remotely, to a full offset to the reduction due
to low elevation and reduced area.

If the foregoing views are correct there were certain periods
in the history of the earth when carbonation proceeded with
multiplied activity, separated by other periods during which its
activity was greatly reduced. The intensification and the reduc-
tion differ by some notable multiplier of the average rate.

In working application, the hypothesis tentatively recognizes
as periods of land extension attended by rapid carbon dioxide
consumption, (1) the close of the Silurian and the opening of
the Devonian, (2) the Permian and early Triassic, and (3) the
Pliocene and Pleistocene. To this category may perhaps also
belong, though the evidence at present is less adequate, (4) the
early Cambrian, (5) the closing Ordovician and opening Silurian,

*For further statement of these views, see The Ulterior Basis of Time Divisions
and the Classification of Geologic History, Jour. GEOL., Vol. VI, No. 5, July—
August, 1898, pp. 449-462; A Systematic Source of Evolution of Provincial Faunas,
Jour. GEOL., Vol. VI, No. 6, Sept.—Oct., 1898, pp. 597-608; The Influence of Great

Epochs of Limestone Formation upon the Constitution of the Atmosphere, zé77., pp.
609-621.

568 PC. (CHAMBERLIN,

(6) the close of the Jurassic and the opening of the Lower Cre-
taceous, and (7) the transition period between the Cretaceous
and the -EKocene. “In these” periods, there are jevadencesiot
declared intensifications of climatic influence expressed in wide-
spread and thick deposits of salt and gypsum and in great series
of red sandstones and marls, and, in the two most notable cases,
by pronounced glaciation in middle and low latitudes.

On the other hand, it regards the following as periods of sea
extension attended by the active freeing of carbon dioxide
through the agency of prolific lime-secreting life, as hereafter
set forth: (1) the middle Ordovician, (2) the middle Silurian,
(3) the sub-Carboniferous, (4) the late Jurassic, (5) the Upper
Cretaceous, and (6), less notable, the later Eocene and earlier
Miocene. During these periods there is evidence of extensive
limestone deposition spreading out widely on the continental
platforms, attended by very mild and equable climates very
nearly uniform for all latitudes.

SOURCES OF TEMPORARY LOSS AND GAIN

The discussion has thus far taken note of the original carbo-
nation of the silicates of crystalline rocks only. These crystal-
line rocks, according to Dr. Tillo,t occupy something over 20
per cent. of the surface of the land. There remains nearly 80
per cent. occupied by secondary rocks which now claim attention.

Sources of temporary loss—The function of the secondary deposits.
—To a large extent the material of the secondary deposits
underwent chemical decomposition and carbonation preliminary
to its deposition, indeed as a prerequisite to its derivation. In
so far as this process was incomplete in the earlier stages, it was
continued during any subsequent state of exposure, but this
action belongs under the preceding head of original carbonation.

In the erosion of tracts of secondary rocks the limestones
and dolomites are dissolved and carried down to the sea essen-
tially as bicarbonates. In the strata they existed as monocar-
bonates. Their solution involves the taking up of a second

* Berghaus Atlas.

WIV ROTMESISIOPACAU SE OF GLACIAL PERIODS 569

equivalent of carbonic acid to render them bicarbonates, and
this second equivalent is derived essentially from the atmosphere.
There is herein a source of temporary loss, temporary because
the second equivalent of carbon dioxide remains associated with
the bases in the sea only until deposition takes place, when it is
set free. It is to be noted that a second equivalent is also taken
up in the formation of original carbonates if they are dissolved.
As the crystalline rocks occupy only a little more than 20 per
cent. of the land surface and are probably not removed as fast
as the secondary rocks, not more than about one fifth, probably
not more than one tenth, of the bicarbonating carbon dioxide is
associated with original carbonation. The remaining four fifths
or more are occupied in bicarbonating and dissolving the calca-
reous and magnesian portions of the secondary rocks. It follows
that the ratio of carbon dioxide now taken out of the atmosphere
as second equivalent in any unit of time, to that taken out as
first equivalent, is probably fully five to one, and not unlikely as
high as ten to one. This ratio would not necessarily hold for
past periods, but in all those under consideration the second
equivalent was undoubtedly very much greater than the first.
Accepting, for the purposes of a rude estimate, the data of T.
Mellard Reade,’ the amount of carbon dioxide removed annually
by original carbonation, reckoned by proportional area, is 270
million tons, the amount temporarily removed as the second
equivalent of the bicarbonates is 1350 million tons ; the amount
. simply transferred from the land to the sea as the first equivalent
of the carbonates previously formed is 1080 million tons; the
total mass taken from the atmosphere annually being therefore
1620 million tons, and the total mass removed to the sea 2700
million tons. Besides uncertainties in the original estimate of
Reade, the first item is subject to correction (probably large) for
the slower rate of disintegration of the crystalline rocks. This
is, however, somewhat offset by weathering action on the sili-
cates that remain undecomposed in the secondary rocks, and on

t Addresses, Geol. Soc. of Liverpool, 1876 and 1884, quoted in Dana’s Manual,
p. 191.

570 T. 6. CHAMBERLIN,

the late volcanics which are not all included in the 20 per cent.
of the land area reckoned as crystalline. The second item is sub-
ject to correction to the extent that the salts were normal car-
bonates and not bicarbonates.

Reciprocal sources of temporary gain—The second equivalent
of the carbonates in the ocean is subject to easy removal under
suitable conditions, and reénriches the atmosphere by diffusion
into it from the ocean. The conditions under which this is set
free are of critical importance to our hypothesis. We have to
consider (a) saturation, (6) chemical reactions and dissociations,
and (c) organic action.

a. Absence of general saturation—In the absence of other
agencies of removal the accumulation of calcium bicarbonates in
the ocean would go forward to the point of saturation, if there
were a sufficient amount producible. It would then be depos-
ited as limestone, and the second equivalent of the carbon diox-
ide would be set free. There is little reason to think, however,
that general saturation has been reached during the known por-
tion of the earth’s history. In local basins subject to peculiar
conditions, saturation certainly has been attained, as the marls
of the great saliferous deposits testify. The present approach
to oceanic saturation in calcium carbonate is apparently only
about 40 per cent. If the ocean in former times had reached
saturation in calcium carbonate and any notable precipitation
had followed, the precipitate should appear as a distinctive con-
stituent of the clastic deposits. While calcareous matter which -
might be so interpreted occurs in some of these deposits, there is
a notable absence of anything of the kind in many others where it
might be expected, and the general character of the sandstones
and shales seems more concordant with the accepted view that
they were laid down in waters that did not, except in special
cases, directly deposit calcareous matter. In view of the proba-
ble presence of lime-secreting organisms, the problem is gener-
ally rather to account for the paucity of calcareous matter than
its abundance in the clastic deposits. The explanation is doubt-
less found in the undersaturation of the sea water and its ability

BVP OTTE SES OLMCAOSE, OF GLACIAL PERIODS. 571

to dissolve calcareous relics. This view is supported by the par-
tially dissolved condition in which calcareous fossils are so com-
monly found in the sediments of practically all the ages. The
inference, therefore, to be drawn from the character of the sedi-
ments, and from the partial solution of calcareous fossils, is that
the ocean, as a whole, has not generally been saturated with
calcium bicarbonate during its known history. Murray has made
us aware that at the present time the greatest depths of the
ocean dissolve calcareous relics so freely as to prevent their
accumulation.

6. Inorganic chemical reactions.— Viewed comprehensively
the sea water consists of such solutions as have been carried
down from the land in past times, modified by concentration and
deposition. No important constituent has been totally removed.
The land and sea waters have therefore the same fundamental
constitution, but the salts of the former enter the sea in a more
dilute form and in different proportions from those contained in
the latter. Aside from organic action, and from exceptional
inorganic agents such as may arise from submarine volcanic
action and like incidental sources, essentially all occasion for
chemical reaction when land waters are added to sea waters, is
limited to a readjustment of the equilibriums of the common
constituents of the two commingling waters. Following the
simple doctrines of the old familiar ‘‘ chemistry of results,’ the
addition of a dilute solution of salts of the alkalis and alkaline
earths to amore concentrated but not saturated solution of thesame
salts would neither occasion precipitation nor the evolution of
gas, for every acid is mated with a base, and all are much below
the point of saturation. According to the old interpretation the
bases of the sea salts are, in the main, mated to stronger acids
than those of the land waters, and these combinations will not
be changed on the entrance of the latter. So, also, the small
amounts of strong acids of the land waters are already mated
with the strong bases in the main, and largely form the same
combinations as those of the sea waters. Such interchanges as
follow involve a double reaction essentially without the freeing

572 TSC GLAMIB TIME,

of acid or base. Under the old method of interpretation the sea
salts, according to Dittmar, consist of —

Percentage Total Tons
Sodium chloride’ - - - 77.758 35,09 Onxel Our
Magnesium chloride - - - 10.878 FLOgdu xan Ome
Magnesium sulphate - - 4.737 22 exehOue
Calcium sulphate - - - 3.600 1, 6001x) lO
Potassium sulphate - . © 2 2.465 TAR 3 Or?
Calcium carbonate - - > Opeyills TOOrx: TOs
Magnesium bromide - - O:217, LOONXa1 One

100.000 460,283 Xx) LOW 4

A rude average of the composition of land waters and of the
amounts of salts carried to sea annually, founded on the esti-
mates of T. Mellard Reade, is here given for comparison.

Approx. percentage ‘Tons annually

Calcium carbonate : = - =) 50 27 OORXaTOS
Calcium sulphate - = = = 20 1,080 x 108
Magnesium carbonate - - - ae) days 216 x TOe
Magnesium sulphate - - - 4 DUS) 5: 1K)?
Sodium chloride - : = = Sel 216 x 10°
Potassium and sodium, 2 : 6 Roe
Sulphates and carbonates
Silica - - - - = = EMA B78) Xx1Oe
Other substances - - - - 5 270) XeLOl
100 5,400 x 108

These tables do not embrace the second equivalent of carbonic acid.

From these data it appears that it would require only a little
over eight and one half million years for the land waters to
bring in a gross amount of salt equal to that of the ocean, but it
would require very different periods to bring in the individual
constituents. It would take 166 million years to bring down
the sodium chloride, but fonly about 1.5 million years to bring
down the calcium sulphate, and only about 60,000 years to
bring down the calcium carbonate. It appears therefore that
there must be agencies constantly removing the calcium carbon-
ate and the calcium sulphate at relatively high rates. These
particular figures are subject to all the uncertainties involved in

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 573

Reade’s primary estimate, but they probably represent approxi-
mately the relative ratios, and show the general nature of the
eliminations that are requisite to change accumulating land
waters into sea waters.

While these general statements of the nature and limitations
of chemical action, based on the more familiar doctrines of the
older chemistry, are doubtless essentially true, the refinements
of modern chemistry teach that there is an intricate series of
dissociations and exchanges of acidic and basic factors, and of
the various ions, in an effort to establish and maintain a new
equilibrium between the salts, required by their new proportions
and their new states of dilution. As the land waters contain a
relatively large percentage of bicarbonates of calcium and
magnesium, the readjustment affects these especially, with the
result that probably a minor percentage of the second equivalent
of carbon dioxide is set free. It seems necessary to state this
with qualification on account of the extreme complexity of the
reactions, and the incompleteness of existing data; but the
Challenger, and similar investigations show that the quantity of
second equivalent of carbon dioxide is less than sufficient to
raise all of the carbonates into bicarbonates. This deficiency is
apparently limited to 20 per cent. or less of the theoretical
amount required. More rigorous experimental determination is,
however, greatly needed.

It is probable that the second equivalent of the land waters
is, deficient in some like degree, but this has not been experi-
mentally determined. If this be true, it must reduce the estimate
of the carbon dioxide brought down to sea, and also the amount
set free by dissociation. The total amount of carbon dioxide
which may be supposed to be set free by inorganic reaction in
the sea in its present state of concentration, is therefore probably
much less than 20 per cent. It is obvious from the preceding
considerations, and others that will follow, that to maintain the
atmospheric status even approximately there must be a nearly
or quite complete return of the second equivalent of carbon
dioxide by some means. This is also implied by the fact that

574 T. C. CHAMBERLIN

the oceanic deposits are not bicarbonates in any notable degree.
The chief agencies of this return are held to be organic, and will
be considered presently.

The chief compounds of both the land and sea waters are
sodium, potassium, magnesium and calcium chlorides and
bromides ; sodium, potassium, magnesium and calcium sulphates;
sodium, potassium, magnesium and calcium carbonates and bicar-
bonates ; in other words, every combination which may take place
between the acids and bases involved. Besides these salts there
are, theoretically at least, the several acids and bases and a com-
plete series of ions as well. There is a continuous dissociation and
reunion in the effort to maintain equilibrium. The extent of the
dissociation is dependent, among other things, notably upon the
degree of concentration of the solution and upon its temperature.
In an especial degree the extent of the freeing of the second
equivalent of carbon dioxide is believed to be dependent upon
this dissociation as influenced by temperature, and it is thus a
vital consideration in realizing the function performed by the
ocean during glacial episodes when its temperature was greatly
changed. This function is made the subject of a special study
in the paper of Mr. Tolman in this number of the JouRNAL."

Mr. Yolman’s studies have been founded upon Dittmar’s
experiments, and seem to show that the amount of carbonic acid
freed from the bicarbonates by dissociation is very sensibly
influenced by such changes of temperature as are necessary,
according to the deductions of Dr. Arrhenius, to produce
extended glaciation, on the one hand, and a mild climate in the
arctic regions, on the other. In this he finds support for the
suggestion which I made in a previous paper? that the ocean
during a glacial episode instead of resupplying the atmosphere,
in the stress of its impoverishment, would withhold its carbon
dioxide to a certain extent, and possibly even turn robber itself.
On the other hand, when the temperature is rising after a glacial

Pp. 585-618.

2A Group of Hypotheses Bearing on Climatic Changes, Vol. V, No. 7, 1897,
p. 682.

WROLHE STS OF CGACSE OF GLACIAL PERIODS: 575

episode, dissociation is promoted, and the ocean gives forth its
carbon dioxide at an increased rate, and thereby assists in
accelerating the amelioration of climate.

c. Organic action.— The elimination of the vastly preponder-
ating percentage of calcium salts in the land waters, involving
aureduction, froni’ 7o' per cent: in these toless than 4, percent.
in sea waters, is assigned mainly to marine life. With the
calcium sulphate we do not seem to be specially concerned
here except so far as indirectly it may become involved in the
reactions which eliminate the calcium carbonate. It would
appear obvious, however, from the fact that its ratio is reduced
from about 20 per cent. in the land waters to about 3.6 per cent.
in the sea waters that it suffers much secular loss. The reduction
of the calcium carbonate from about 50 per cent. in the land
waters to about one third of I per cent. in the sea waters is a
fact of prime importance.

The amplest and most familiar geological observation shows
that the elimination takes place mainly as normal carbonate of
lime in the form of shells and skeletal parts of various marine
animals, and of some plants. The gross fact of observation is
the disappearance of great quantities of calcium bicarbonate
from the water, and its reappearance as the secretions of animals
and plants in the form of normal carbonate. Whatever may be
the specific steps involved in their life economies, it seems
essentially immaterial to consider here whether the animals and
plants take their lime directly from the calcium carbonate, and
set its surplus carbonic acid free, or whether they take it from
calcium sulphate, and by using carbonic acid, derived ultimately
from the waters also, convert it into carbonate, setting free the
sulphuric acid to attack in turn the calcium carbonate of the sea,
and thus by circuitous process free its carbonic acid, or whether
the procedure follows any other indirect course; for the final
result, when balanced all around, seems to be essentially the
same. It may even trench on the organic cycle without essentially
changing the final result. The important thing to be observed
is that the process is dependent upon sea life, and varies with its

576 T. C. CHAMBERLIN

activity. There is no free supply of any competent discharging
agency independent of sea life.

Variations of lime-secretion by sea life-—The amount of lime-
secreting sea life is greatly influenced by the temperature of the
sea and by favorable habitat. Lime-secreting sea life, both
plant and animal, is greatly favored by high temperature and
reduced by low. In support of this the following statements
from the Challenger Report’ and other sources may be offered,
in which I have italicized the significant parts :

Species of algae which secrete carbonate of lime are abundant in the
shallow waters of the ocean. In the ¢vopical regions especially there are
massive species of Lzthothamnion, Lithophyllum, Halimeda and other genera
that make up a large part of some coral reefs and of the surrounding coral
sands and muds. Zwo hundred fathoms is probably the extreme limit at
which any of these organisms live in the ocean.

Rhabdospheres are especially developed in eguatorial and tropicac
regions, and are rarely met with in regions where the temperature of the
surface water falls below 65° F. (18.3° C.). Coccospheres, while abundant
in tropical waters, are found further north and south than the Rhabdospheres ;
they are present even where the temperature on the surface is as fow as 45°
F., (7.2 C.); indeed, Coccospheres attain their greatest development in Zem-
berate regions. These organisms are absent or vave in coast waters affected
by rivers; they especially flourish in the pelagic currents of the open ocean.

. In Arctic and Antarctic waters Coccospheres and Rhabdospheres are
replaced by similar minute alge whzch do not, however, secrete rods and
disks of carbonate of lime on thetr outer surfaces.

Rhabdoliths and Coccoliths—the broken down parts of Rhabdospheres
and Coccospheres— play a most important part in all deep-sea deposits, wzth
the exception of those laid down in polar and subpolar regions.

Of all the organic remains met with in marine deposits, by far the most
frequent are the shells of Foraminifera, it may be safely said that these
organisms or their fragments are present in every average sample of marine
mud, clay, ooze or sand. ... Wearly all the spectes are confined to tropicas
and subtropical waters, they gradually disappear from the surface-nets as
the polar regions are approached, the dwarfed forms Globigerina pachyderma
and Globigerina dutertret, being the only species met with in Arctic and
Antarctic waters. . .'. Jz the calcareous oozes from tropical regions, the shells
of all the spectes inhabiting the surface waters are observed in enormous
abundance, but these same spectes are never met with in deposits from polar

TE ZLOMS artis»

* Challenger Report, Deep Sea Deposits, pp. 257, 258-261, 263, 31 and 266.

/

WV ROTHESTS OF CAUSE OF GLACIAL PERIODS i.

There are not more than twenty or twenty-two species of pelagic Forami-
nifera, yet so numerous are the individuals of the species that they usually
make up over go per cent. of the carbonate of lime present in the calcareous
oozes of the abysmal regions of the ocean... .

The bottom-loving Foraminifera—those belonging to the Benthos—avre
more abundant in the shallow water, than in the deep-sea deposits, and
occasionally a single species may occur in such abundance in shallow depths
in some regions as to make up the greater part of a deposit. . .

The presence of large numbers of Pteropod and Heteropod shells indicates
tropical or subtropical regions, and relatively shallow depths. Abundance of
the shells of pelagic Forminifera indicates the same regions, but when found
without the shells of pelagic mollusks they indicate a greater depth than
when these latter are present. . .: The presence or absence, and the size
of Rhabdoliths, Coccoliths and Coccospheres gzve zmportant indications as to
latitude and depth —the first predominating in tropical regions, the two latter
being better developed in temperate regions, and a// disappear from the
deposits as the polar waters are approached.

*A large number of these pelagic mollusks (Pteropod and Heteropod)
secrete carbonate of lime shells, and this ts especially the case in tropical
waters. In folar regions the place of the shelled species is taken, with the
exception of one or two small species of Limacina, by a shed/-less shecies.
The shells of the tropical species make up a large part of some tropical and
subtropical deposits from moderate depths, in which there is a relatively
small quantity of land débris. Like the pelagic Foraminifera these pelagic
Mollusca attain their greatest development in the warm oceanic currents,
and diminish both in the number of species and the size and mass of the shells
as the colder currents of the polar regions are approached.

Reef-forming corals are confined to waters which, through even the
coldest month, have a mean temperature not below 68° F. Under the equator
the surface waters in thehotter part of the ocean have the temperature of
g5° F. in the Pacific, and 83° F. in the Atlantic. The range from 68° to 85°
is, therefore, not too great for reef-making species."

An isothermal line crossing the ocean where this winter temperature of
the sea is experienced, one north of the equator, and another south, bending
in its course toward or from the equator, wherever the marine currents
change its position, will include all the growing reefs of the world; and the
area of waters may be properly called the coral-reef seas.

Over the sea thus limited coral reefs grow luxuriantly, yet in greatest pro-
fusion and widest variety through tts hottest portions.*

I have found no specific statements relative to the dependence
of common mollusks on temperature, but the enumeration of the

Dana: Corals and Coralline Islands, p. 83.

578 TC: CHAMBERLIN.

species in different latitudes clearly indicates that they are less
abundant in the arctic provinces than in the tropical, from which
it may perhaps be safely inferred that the lime-secreting function
of the mollusks is increased by warm temperature.

In the foregoing quotations references are made to the
preference of certain forms for shallow waters. The great pre-
ponderance of lime-secreting species on the shoal areas— 100
fathoms or less—is too familiar to need emphasis.

In other articlest I have endeavored to show that there were
certain stages in the earth’s history when the seas were extended
widely over the continental platforms, affording conditions
extremely favorable to the multiplication of lime-secreting
shallow-water life. I endeavored to connect these, on an obser-
vational basis, with the great limestone-producing epochs of
geological history and to show that these were correlated with
genial climates over high and low latitudes alike. On the other
hand, I endeavored to show that there were other periods during
which the land area was increased and the sea restricted, result-
ing in a great reduction of this normal habitat of the chief lime-
secreting forms of life. I endeavored to show that so far as the
lime-secreting life is concerned, the freeing of carbonic acid was
promoted during periods of extended seas and that it was.
retarded during periods of extended land. This holds good
when considered simply from the standpoint of available area,
but it becomes still more true if, as this hypothesis maintains,
the extension of sea-area was correlated with favorable tempera-
ture, while the restriction of sea-area was correlated with adverse
temperature. The only pelagic life that enters much into the
problem is that which occupied the superficial waters of the open
ocean. The area of this increased and diminished concurrently
with the extension and contraction of the sea.

* A Systematic Source of Evolution of Provincial Faunas, Jour. GEOL., Vol. VI,
No. 6, pp. 597-608.

The Influence of Great Epochs of Limestone Formation upon the Constitution of
the Atmosphere, JouR. GEOL., Vol. VI, No. 6, pp. 609-621.

PIV POUL SiO OL ICA OS OF GLACIAL PERIODS 579

THE FORMATION OF ORGANIC COMPOUNDS AS AN AGENCY OF
ENRICHMENT AND DEPLETION

The familiar fact that plants produce complex carbon com-
pounds at the expense of the carbonic acid of the air, and that
animals, aided by plants, by combustion, and by decay, decom-
pose these compounds, and return a portion to the air as carbonic
acid need not be dwelt upon. These reciprocal processes con-
stitute a cycle which, in so far as it is mutually compensatory,
affects the constitution of the atmosphere only in temporarily
locking up carbon in the transient organic matter. The cycle,
however, is not complete at any time, and has fallen far short of
being complete at certain times. A portion of the carbon com-
pounds are not reconverted into carbonic acid, and this residuum
has been sealed up in the strata, and represents so much of
depletion of the atmosphere. When this residuum was large
there was a hastening of the process of robbing the atmos-
phere. When it was small it put less tax upon the agencies of
supply. In its concrete application, the hypothesis recognizes
one notable period of residual accumulation, the Coal Measures.
Subordinately it recognizes others, as the Huronian and the late
Cretaceous. Perhaps the Coal Measure period is the only one
in which the excess of carbon composition over decomposition
was so great as to seriously influence the constitution of the
atmosphere, considered by itself alone, though this is open to
question. A computation of the carbonic acid locked up in
coal and similar carbonaceous deposits compared with that
locked up in the limestones shows that the former is greatly
inferior to the latter, from which it is inferred that the organic
factor has been much the less influential in producing variations
of atmospheric constitution, per se, than through its relations to
the carbonates.

Respecting the organic cycle itself, it is obvious that when
the sum total of vegetable and animal life increases, the amount
of carbonic acid locked up in the living organisms is increased,
and wice versa. The total mass of all the vegetable and animal
living matter on the earth is some small fraction of the total

580 T. C. CHAMBERLIN

amount of free carbon dioxide. It does not seem possible now
to arrive at any closely approximate estimate of this ratio.
Johnson’ expresses the belief that the growth of plants would
exhaust the carbonic acid of the atmosphere in 100 years if there
was no return. The average length of time during which plant
products remain as living tissue is probably greater than one
year, and much less than ten years, which would make the
total amount of the carbonic acid so locked up a quite small per
cent. of that in the air. The amount of carbon locked up in
the tissue of marine life which probably was not embraced in
Johnson’s estimate, would somewhat notably increase the figure,
but if oceanic life is considered, the free carbonic acid of the
ocean must be considered also which would greatly reduce the
ratio.

A study of the life of the geological periods seems to indi-
cate that there were very notable fluctuations in the total mass
of living matter. To be sure there was a reciprocal relation
between the life of the land and that of the sea, so that when
the latter was extended upon the continental platforms and
greatly augmented, the former was contracted, but notwithstand-
ing this it seems clear that the sum of life activity fluctuated
notably during the ages. It is believed that on the whole it was
greatest at the periods of sea extension and mild climates, and
least at the times of disruption and climatic intensification.
This factor then acted antithetically to the carbonic acid freeing
previously noted, and, so far as it went, tended to offset its
enmiectss

THE FUNCTION OF THE OCEAN AS AN ABSORBENT OF CARBON
DIOXIDE

The atmosphere penetrates the ocean by simple diffusion
according to the laws of gas diffusion, modified slightly by
hydrostatic pressure, and this must be considered in close com-
putations, but is too small a factor to seriously affect the larger
issues.

*How Plants Feed, p. 47.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 581

Absorption of carbonic acid.—Independently of this the ocean
has a specific power of absorbing carbonic acid. It is important
to note that this power of absorption is greatly affected by
temperature, as shown by the following table of the variations
for pure water :*

I volume of water at o° dissolves 1.7967 volumes of carbon dioxide.
PMs sian iS Pare ee AAO En oases :

I hate HY On : Tenody7 a a a af

I Ur a ipa Hised oe 1.0020

I te a A 2 Ole ‘e 0.9014 a oe “s ec

The precise rates of absorption for sea water are not accu-
rately determined, and, indeed, are determinable with difficulty
because, experimentally, they are complicated with the ‘‘loose”’
carbonic acid of the bicarbonates which is liable to be constantly
freed by dissociation. The rates appear to be something less
than those that obtain in pure water. Mr. Tolman has discussed
this factor in his paper already referred to.

Release of absorbed carbonic acid.—Theoretically both the
carbon dioxide diffused through the ocean and that dissolved in
it should be in equilibrium with that of the air. Its quantity is
dependent upon the temperature of the ocean and upon the
partial pressure of the carbon dioxide of the air. Whenever the
temperature of the ocean is raised a portion of its dissolved car-
bon dioxide is given forth. Whenever the partial pressure of
the carbon dioxide of the air is reduced a portion of the free
carbon dioxide in the ocean diffuses forth to reéstablish the
equilibrium. The tendency to equilibrium is always present,
though the constant variations of temperature and partial pres-
sure prevent its complete realization at any particular time. If
there were no counteracting influence the free carbon dioxide of
the ocean would act as though it were a part of the air, and as
the carbonic acid of the latter was consumed, that of the former
would come forth into it.

But with loss of atmospheric carbon dioxide there is a reduc-
tion of temperature, and this increases the absorptive: power of

t Treatise on Chemistry, Vol. I. ROscorE and SCHORLEMMER, Pp. 724.

582 Le Cy LLANELLI TIN

the ocean, which then tends to prevent the escape of the car-
bonic acid. Low temperature is, therefore, antagonistic to
atmospheric resupply. Mr. Tolman has attempted to ascertain
the relative value of increased absorptive power and reduced
partial pressure, and, though the data are insufficient for final
conclusions, finds them about equal. The withdrawal of carbon
dioxide from the air does not therefore call forth a proportionate
amount of free carbonic acid from the sea. Indeed, it calls forth
so little that the rate of atmospheric depletion is probably not
appreciably retarded by it.

Summation.— Before proceeding to make special application
of the hypothesis to the recognized glacial periods it may be
serviceable to bring together into briefer statement the fluctuat-
ing features of atmospheric gain and loss.

1. Of the agencies of original or permanent supply, the
internal group have probably fluctuated in some rude proportion
to the disruption of the crust of the earth; the external group
are beyond tangible treatment, but for aught that appears may
be regarded as essentially uniform.

2. Of the agencies of permanent depletion, the conversion
of silicates into carbonates (the chief factor) is assumed to have
fluctuated essentially with the extension and restriction of the
land; the formation of carbonaceous deposits fluctuated with
the well-known conditions that presided over coal accumulation.

The agencies of permanent supply and of permanent loss are
both regarded as rather slow in action and as being on the whole
mutually compensatory, and indeed as being in some degree self-
regulative since increase of supply naturally increases consump-
tion and reduction of supply ultimately reduces the consumption ;
but these relations are believed to be subject to sufficient fluctu-
ation to give a basis for pronounced climatic changes.

The sources of temporary supply and waste are much more
rapid in action and apparently more intense and voluminous in
results within any brief period.

1. The sources of temporary loss are: (a) the locking up of
carbon dioxide in bicarbonates while in solution as their second

VIVROTAHESTS\OPICA USE, OF GLACTAL, PERIODS 583

equivalent (the great factor); (0) the absorption of carbon
dioxide in sea water; and (c) its consumption in forming organic
matter.

The first and greatest of these is definitely connected with
extension and elevation of the land, and the second is largely a
sequel to it, dependent upon the temperatures it induces, while
the third does not usually codperate with these two, but father,
to the extent of its limited competency, offsets them.

2. The sources of temporary enrichment embrace: (a) the
discharge of the second equivalent of carbon dioxide in the sea
by life action (the great factor), and (4) by dissociation ; (c) the
diffusion into the air of carbonic acid absorbed in the sea water
due to higher temperature antagonized by reduced partial pres-
sure, and (2) the freeing of carbonic acid both in the air and the
ocean by the decomposition of organic matter.

These sources of fluctuation are definitely correlated with the
elevation and extension of the land, on the one hand, and the
extension of the sea and the reduction of the land, on the other.
During an extensive elevation of the land, silicates are converted
into carbonates at an increased rate and the limestones and dolo-
mites are dissolved and carried to the sea more rapidly, both
processes involving an acceleration of the consumption of carbon
dioxide. Correlated with this extension of the land is a reduc-
tion of the sea area attended especially by a lessening of the
area of the continental shelves which are the habitat of the chief
lime-secreting life, while the area available for pelagic surface
life is also lessened. Reduction in the lime-secreting life retards
the incidental process of freeing carbonic acid and returning it
to the atmosphere. The result is a reduction of temperature
which in turn increases the ability of the ocean to absorb carbon
dioxide and reduces the dissociation of the second equivalent of
carbon dioxide, thus further reducing the returning process and
increasing the capacity of the ocean to hold carbon dioxide not-
withstanding the reduction of the partial pressure in the atmos-
phere. The reciprocating processes are thus temporarily affected
in opposite directions so as to conjoin their results.

584 Ne (Op (Gla lAAH eT DIRT EIUN

In periods of sea extension and of land reduction (base-level
periods in particular), the habitat of shallow water lime-secret-
ing life is concurrently extended, giving to the agencies that set
carbon dioxide free accelerated activity, which is further aided
by the consequent rising temperature which reduces the absorp-
tive power of the ocean and increases dissociation. At the same
time, the area of the land being diminished, a low consumption
of carbon dioxide both in original decomposition of the silicates
and in the solution of the limestones and dolomites obtains.
Thus the reciprocating agencies again conjoin, but now to
increase the carbon dioxide of the air.

These are the great and essential factors. They are modi-
fied by several subordinate agencies already mentioned, but the
quantitative effect of these is thought to be quite insufficient to
prevent very notable fluctuations in the atmospheric constitu-
tion. As a result, it is postulated that geological history has
been accentuated by an alternation of climatic episodes embrac-
ing, on the one hand, periods of mild, equable, moist climate
nearly uniform for the whole globe; and on the other, periods
when there were extremes of aridity and precipitation, and of
heat and cold; these last denoted by deposits of salt and gyp-
sum, of subaérial conglomerates, of red sandstones and shales,
of arkose deposits, and occasionally by glaciation in low lati-
tudes.

T. C. CHAMBERLIN.

[ The continuation of this article in the next number will embrace a discussion of
thé application of the hypothesis to known glacial periods, and to the oscillations from
glacial to interglacial epochs, together with the agencies of localization, and a sug-
gestion regarding the superposed minor oscillations. |

THe CARBON DIOXIDE OF THE OCEAN “AND ITS
REEATIONS< tO° RE CARBON: DIOXIDE OF THE
PVVIOS PEE RE 2

OUTLINE.
I. Introduction.
(1. Mass action.

2. Dissociation.
Den Lawton dilite mes, 3: Heterogeneous equilibrium and the change
in the solubility of one salt due to the
presence of others.
ee Hydrolitic dissociation.
(1. Class I.
3. Solution of gasesin pure ; 2. Class II. { Physical solubility.
3. Carbonic acid. ( Chemical solubility.
4. Amount of gases dissolved.

water.

4. Solution of gases in salt (1. Class 1. Oxygen, Nitrogen, etc.
solutions. 2. Carbonic acid.

1. Amounts.

5. The ocean salts. 1 : oo tte
2. Degree of dissociation.

6. The ocean gases. 1 Te Dose pIETOBEy and argon.
2. Carbon dioxide.

. Simple Solution.

AS Eis COs.

. Modified by the ocean salts.

. Maximum amount held thus in the

SW NN

ocean under the laws of gas absorp-
tion.

5. Ditto. As second equivalent of
bicarbonate.

7. Relation of the atmospheric and oceanic CO,.
1. CO, of the bicarbonates.
2. Dissociation of the bicarbonates.
3. Degree of dissociation as a function of temperature and pressure.

* Especial thanks are due to Dr. Chamberlin, Dr. Stieglitz and Dr. Lengfeld, of
the University of Chicago, for careful revision of this article and many valuable sug-
gestions.

585

586 CVS Ai) OLM AR

4. Effect of variation of pressure and temperature postulated by Dr.
Arrhenius. (a) Upon bicarbonate in the waters of the temper-
ate zone. (4) Upon bicarbonates in equatorial waters. (c)
Upon bicarbonates in colder waters.

5. Changes in volume of the belts due to cold water advancing
southward.

6. Conclusions.

Tus subject has come to have special importance on account
of the investigations of Professor Arrhenius* and Dr. Chamberlin,?
on the effects of the atmospheric CO, upon the climate of the
earth. Some of the earlier important contributions on the sub-
ject are as follows:

Tyndall calculated from his experiments that the absorption
of radiant heat by atmospheric CQO, is eighty times that of the
oxygen or nitrogen, and that water vapor has an absorbing
capacity of ninety-two times that of oxygen or nitrogen.3

By repeating and extending Tyndall’s experiments, Dr.
Lecher and his colleague, Pretner, concluded that carbon dioxide
is the only agent in absorbing the sun's heat, and maintaining
the earth’s temperature above that of space.4

Mr. J. S. Keeler criticised the above and stated that the heat
is absorbed by carbon dioxide and some other agent; either
water vapor or matter in suspension.’

Professor Réntgen showed that water vapor has a marked
absorption band in the ultra red and, therefore, plays an important
part in maintaining the present surface temperature of the earth.®

Paschen demonstrated that both these gases play important
parts in the atmosphere’s heat absorption, and that sometimes
one, and sometimes the other is the predominant factor.’

Phil. Mag... Vola XWiippy237—270:

2Jour. GEOL., Vol. V, 1897, pp. 663-683. Also this No., pp. 545-584.

3 Introduction of Chemical and Geological Essays, T. S. Hunt.

4Sitzungsberichte des Akad. der Wissenschaften d. Wien (2) Vol. LXXXII, p.
851 (2) Vol. LXXXVI, p. 52.

5 Am. Jour. Sci. (3) Vol. XXVIII, p. 190.

° Poggendorf’s Annalen (2) Vol. XXIII, p. 1259.

7 Phil Mag., S. 5, Vol. XLI, No. 251, April 1896, p. 239.

CARBON DIOXIDE OF THE OCEAN 587

The discovery that this constituent of the atmosphere is an
important dynamic factor among geological agencies has led us
to investigate the eighteen potential atmospheres of carbon
dioxide in the ocean. This at once leads us to a consideration
of the chemistry of the ocean, and here we find that the indefi-
niteness of our notions upon this subject is not so much due to
lack of data, for that has been collected by individuals and
by well equipped expeditions, as to erroneous conceptions of
the relations and reactions that obtain between the several
constituents of a mixed solution. Important investigations
involving large outlays of time and money have been rendered
nearly valueless, because they were based upon assumptions
which were accepted without proof, and which are now
known to be false. The importance of the first principles
which govern solution and precipitation in such a solvent
as water (and which have but recently been formulated )
justify a review of some of them as an aid to the interpreta-
tion of the reactions taking place in that great laboratory the
ocean."

Mass action.2—I\t will be remembered that Berthollet in 1803
was the first to conceive of chemical reactions as governed by
equilibrium, dependent both on the mass and the affinity of the
constituents. The value of his discovery was not realized
because he unfortunately did not believe chemical compounds to
have definite compositions.

In 1864 Goldberg and Waage re-stated the law of mass
action, which may be developed as follows. Let us consider
any two substances, A and B uniting to form two other sub-
stances C and D.3

All simple reactions that have been carefully studied have
been shown to be reversible, therefore, as soon as any of C and

‘Complete discussion of the laws of dilute solution, etc., may be found in any of
the up-to-date text-books on physical chemistry.

2,W. NERNST: Theo. Chem., pp. 353-455, etc., 117-150. OSTWALD’s Outlines of
Chemistry.

3 GOLDBERG and WAAGE: Videnskabernes Selskabs Forhandlinger, 1864.

588 CVR OS PESROLIV AN,

D is formed there will be a union of C and D to form A and B.
This reversible reaction is expressed thus :"
feel 2) orcs (68s 0 DY

Let the degrees of concentration of the active masses, z. ¢., the

masses in’ units*volume ot A, B, Cand D be) respectively
~,9,p and g’. The unit measure of concentration is the gr.
equiv. per liter. “Let K be the rate of “combination of unit
masses of A and B, and K’ that of C and D. Now the magni-
tude of the reaction of A upon B is evidently K pg (for the
number of impacts of A upon B depends directly on their con-
centration) and that of C and D is K”. p’ g’. Now when
equilibrium is established, the reaction of A upon B =the reac-
tion of C upon D or Kpg—K’ p’ gq’ (the law of mass action).

Dissociation.— From the study of electrolysis? of salts, Clausius
was compelled to assume that at least a small portion of the salt
was dissociated into its positive and negative ions, Na Cl, for

instance, into the positive ion (Na) and the negative ion (Cl).

Arrhenius3 found that the osmotic pressure of a dilute solution
of a salt in water, is that which it should have if a large propor-
tion of the molecules of the salt are split into two smaller
molecules (Na Cl for instance, into Na and Cl) and also that this
change in osmotic pressure is a function of the electric conduc-
tivity. He was therefore compelled to conclude that practically
all of the salt may be dissociated in very dilute solutions, but, in
more concentrated solutions the proportion dissociated becomes
smaller. It then became evident that this action is reversible
and is expressed

+ nets
Na + Cl 2== NaCl.

S

* A simple illustration of a reversible reaction is the evaporation of water in an
enclosed dish. Particles of water leave the liquid to form the superincumbent layer
of water gas. As soon as any of the gas is formed it in turn gives back water par-
ticles to the hquid. Equilibrium is established and there is apparently no farther
evaporation when the number of particles given off by the liquid equals the number
of particles returned by the gas.

? Ges. Abh. (sep. papers) II, 135, 1867.
3 ZEITS: Phys. Chem., Vol. I, pp. 631 ff.

CARBON, DIOXIDE OF THE-OCEAN 589

Then, according to the law of mass action——
ke QO KS c

where a and @ are the concentrations of the ions (Na and Cl)
and ¢ of the dissociated salt."

GO KS its 7

Seo e

This K is called the ionization or dissociation constant, and is
a constant under constant temperatureand pressure, but is different
tor each different salt.

Salts, strong acids and bases (hydrochloric acid, sodic hydrate,
etc.) are the substances most dissociated, while the weaker acids
and bases (acetic acid, ferric or ammonium hydrate, ete: ) sare
dissociated to a less degree, z. e., the constant K is smaller.

It follows directly from equation (2) that the more diluted the
solution the more complete is the dissociation. If the strength
of the solution is such that concentration @ and 6 are each rep-
resented by 2 andc by 4; and then the concentration of all be
decreased so that a@ and 6 become 1, we find by substitution in
the equation (2) that c also must become 1, and the ratio of
dissociated to undissociated or molecular salt, is 1:1 instead
Ofmtat 22

Fleterogeneous equilibrium. We may have some undissolved
substance (C) in contact with a saturated molecular solution (C, )
of the same substance which is dissociated, more or less, into its
ions (Aand B). The concentrations are a and 6 for the ions, ¢c for
the undissolved (solid) salt. and c, for the undissociated dis-
solved part of C. Equilibrium being established between the
solid C and the molecular solution of the solid (C2—C,),
the equation is

1: (3)
But the concentration of a solid at given temperatures and pres-
sures is a constant (its specific gravity) (¢ —K,), therefore

* This simple formula is not strictly accurate in the case of electrolytic dissociation
but is correct enough for our purpose.

590 CV RUS ES LOLMVAWN

K
CS Ks 4
1 1K 3 ( )
Now the dissolved undissociated part of the salt dissociates into
its ions
< ab e
(Co) os, (5)
1
but substituting from (4)
ab —K,K,=K. (6)

This K is called the constant of solubility, or the ion product.
This is the law governing precipitation of electrolytes, and under
it there are three cases.

(a) ad> K.

(b) Zo

(c) ad< K.

(a) If ad is greater than K the action goes A + B
and again C, >C, therefore we have precipitation.

(b) If a= K, we have equilibrium, and neither precipitation
nor solution takes place.

(c) If aé is less than K the action goes

Ce >A+ BandC a Ga
that is solution takes place.

Now, if we mix solutions of two or more salts, besides the
undissociated salts which were present in the separate solutions
in equilibrium with their respective dissociated ions, we will
have in the mixture also the salts that can be formed by the
union of the positive ion of each salt with the negative ion of
each of the other salts. From the foregoing the following

= C

1?

propositions are derived :

Proposition 1.—Mixed solutions of two or more salts will
contain all the salts that can be made by the combination of
the ions of the original salts together with the free ions.

Proposition 2,—Ogf all these salts that one will be precipitated
first whose product of ionic concentration first exceeds its con-
stant of solubility or ion product.

If a salt be added to a mixture of salts in solution, there is
added not only the salt itself but its ions also. If one of the

CARBON DIOXIDE OF THE OCEAN 591

salts of the original mixture have an ion in common with the
new salt (as for instance Clin Na Cland KCl), then the product
of the ionic concentration of each salt is increased. Now if,
before mixing, this product for either salt nearly equaled its
constant of solubility, the increase may be enough to bring
about precipitation. If, for instance, to a solution of lead chlo-
ride, which is not altogether insoluble in water, is added a
sufficiency of K Cl, this addition. causes a precipitate of lead
chloride, since the addition of the Cl ions of the potassium
chloride causes the product Pb x Cl? to be larger than K
where Pb =concentration of lead ions, and Cl = concentration
of chlorine ions. .

If, however, the salt added has no ion incommon with ions
of the other salts, it will take away from the ions of all the
salts to form some of all the undissociated salts that result from
the combination of the two new ions with all the ions of the
original salts, therefore the product of ionic concentration for
all the salts is decreased, or, in other words, the solubilities of all
the salts are increased. Hence,

Proposition 3.—In a mixture of salts those with a common
ion increase the ionic concentration of each, aiding precipitation,
and those without a common ion decrease ionic concentration of
each, and retard precipitation, each increasing the solubility of
the other

Hydrolytic dissociation.—Water, which is one of the weakest
of acids, is itself dissociated into hydrogen and hydroxy] ions
(HO z= + OF); but this takes place to a.very slight
extent only. Kohlrausch found that at 18° C. for water dis-
tilled in a vacuum there is less than one gram of hydrogen ions
in two million liters of water,t and Ostwald, Arrhenius, and Weis,
and Kohlrausch? in later experiments (see reference below),

found about one-sixth of this dissociation by other methods.
Of course these free ions will react with ions of the salts in

tW. NERNST: Theo. Chem., pp. 658-662.

2F, KOHLRAUSCH and AD. KEYDWEILLER, Zeits. f. Phys. Chem., XIV, pp.
317-330.

592 CYRUS F. TOLMAN

solution to form some undissociated acid and base (Na Cl +
HOH Z2=. NaOH +2 HCl). But: sincetthere asisuchwa wemy
small amount of free dissociated ions of water and the disso-

ciation constants of sodic and hydrochloric acid are large, this
action is very slight. However, the salts of the weakest acids
and bases are affected more by the same amount of dissociated
water than those of the stronger ones, because, as shown by
equation (2); K is smaller, therefore a larger amount of the
undissociated acid, or base, exists in proportion to the ions.

Water when heated becomes more dissociated, and therefore
a stronger acid, and this fact is sometimes made use of in the
analytical laboratory, and is an important factor determining the
composition of minerals deposited from hot solutions.

Solutions of gases in pure water—Ilf a gas dissolves in a sub-
stance with which it is perfectly neutral, that is, if no chemical
reaction takes place between the gas and the solvent, then the
amount of the gas dissolved in the liquid at a given tempera-
ture varies directly with the gaseous pressure, or partial pressure,
if there be more than one gas.

Now, if any gas were absolutely neutral to the solvent, and if
on solution its molecule suffered no change in constitution, we
should get the same amount of heat absorbed or given off in the
solution that would be absorbed or radiated by the same
amount of gas brought to the density of the dissolved gas.

But upon solution in water it is found that some gases suffer
a larger heat change than can be explained by any mere physi-
cal change in volume, while others have the same or nearly the
same change in temperature, as that calculated upon the
assumption of simple physical absorption. It has been shown
that the gases with this large heat change upon solution undergo
besides physical diffusion, a chemical change, more or less exten-
sive. Therefore, gases may be arranged in two classes. The
first class is composed of those gases which have but a slight
reaction with water, and are sparingly soluble in that menstruum,
and the other, of those which have large coefficients of solubility
and which react with water to form definite compounds.

CARBON DIOXIDE OF THE OCEAN 593

Of the former, those found in the ocean are nitrogen, oxy-
gen, argon, etc., and of the latter, none are found in appreciable
quantities, but we may take ammonia as a good example. This
last unites with water to form NH,OH which compound is
known to exist as such... The behavior of carbon dioxide
towards water places it between these two classes. It unites
with water to form H,CO,. This acid has never been sepa-
rated as such, but doubtless exists.2 This action does not give
such a large coefficient of solubility as is characteristic of the
gases of the second class.

The solution, then, of oxygen, hydrogen and argon, etc., is
simple diffusion due to the attraction between the molecules of
the solvent and those of the gas, while the solution of CO,
in pure water includes (1) a diffusion of the gas molecules
between water molecules and (2) a chemical reaction between
the gas and water molecules to form carbonic acid.

Bunsen 3 has determined the solubility of the carbon dioxide
for different temperatures as follows :

Solubilityrot CO lun i-Oy71 vol. TO at fdeorees and, 760
mm. pressure dissolves V vols. CO, cas reduced to o ©. and
700 =: pressure:

toc, V. tC V7, t7 C; V.

fe) 1.7967 7 1.3339 14 1.0321

I 1.7207 8 1.2809 15 1.0020

2 1.6481 9 We2 su 1 16 0.9753

3 1.5787 Io 1.1847 U7 0.9519

4 1.5126 TE Li1416 : 18 0.9318

5 1.4497 12 1.1018 19 0.9150.
6 1.3901 13 1.0653 20 0.9014

In the above table the solubility is determined for pure CO,
unmixed with other gases under 760™™ pressure. For low
pressures the solution of the gas is proportional to the pressure
or the partial pressure of the CO, .

™PROFESSOR MALLET, Am. Chem. Jour., Vol. XIX, pp. 804-809.
? DAMMER, Anorg. Chem. II, 1, p. 871.

BUNSEN’s Gasometry, pp. 287, 128, 152.

594 CYRUS Fi TOLMAN

The atmosphere, of course, is not pure CO,, but a mixture
of gases in the following proportions : Oxygen, 20.9 vol.; nitro-
gen, 79.1 vol., of which 01.18 per cent. belongs to that group
of gases called argon,’ CO, .03 vol.

At any given temperature the amount of the atmospheric
gas dissolved in pure water is the product of the amount dis-
solved under 760™™" pressure of the pure gas by the partial
pressure of gas in the air. This holds for the carbon dioxide in
spite of the chemical reaction CO, + H,O ——= COR hs
may be seen as follows:

Let a, 4, and ¢ be the concentrations respectively of CO,,
iO yand hy, COZ ithenretone

b
=: Ky,
G

but the water is so greatly in excess that its concentration, 4, can
be considered as a constant (K,) or

&
a

Therefore the amount H,CO, |c]| varies directly with the amount
CO, [a] dissolved, and this is proportional to the partial pressure
of the gas. Making the calculations from Dittmar’s tables, we
find that one liter of pure water at 15° C. dissolved from the
atmosphere).32° of €@O,,.7.2 of oxygen, and 13.2..01 angen
and nitrogen.’

The absorption of gases in salt solutions.—The researches of J.
Setchenow? show us that a gas dissolved in salt solution obeys
the same laws as if the salt were not present, if there is no
chemical reaction between the gas, the salt,and the solvent. In
this case, however, the attractive power between the molecules
of the solvent and the gas is partially satisfied by the salt mole-

«Chem. News, 72 p. 308. Comptes Rendus de |’ Academie des Sciences, CX XI,
p. 605.
?Challenger Reports, Vol. I, pp. 167-168.

3 Ann. de Chemie: pp. 226-270.

CARBON DIOXIDE OF THE OCEAN 595

cules. From some of his tables we find that for a solution of
the strength of the oceanic brine the diminution of the solubility
for gases of this class is somewhere near 20 per cent. (Joc. cit.
PP: 245-259).

If, however, there is a chemical reaction between the gas and
the salt, the solubility is increased by so much. Oxygen, nitro-
gen, and argon do not react with the salts of the ocean, but
COG does, The carbonic acid dissociates into its ions, and
these ions react with the ions of the salts to form small quanti-
ties of undissociated compounds. This reaction has an appreci-
able effect only where the original salt is formed from weak
acids and bases. From Mr. Setchenow’s tables* for Na Cl
solution of the strength of the sea water we gather that this
increase for CO, would not be over 20 per cent. of that dissolved
by pure water (.3” per liter, a quantity wholly negligible).

The ocean salts.,—The average temperature of the surface of
the ocean is about 15°C.

The proportion of the different salts in the ocean, Professor
Dittmar finds to be wonderfully constant for all parts of the sea
water. He gives the following analysis for the salt :

Gl, = - - - - - 5 5.292%
Br - - - - - - .1884
5SOz - - - - - 6.410
COs = - - - - - .152
CaO - - - - - 1.676
MgO - - - - - - 6.200
K,0 - - - - - 1agQ2
Na,O - - - - - 41.234

Basic O (equivalent to Hologen) —12.493
100

This table we have recalculated for the percentages of the
ions according to modern usage, and in order to facilitate subse-
quent discussion, as follows :

mIcoe. cit.p. 240:

? Phys. Chem. Chall. Exp., Vol. I. Narrative of the Cruise of H. M. S. Chal-
lenger, 1885; Ency. Brit. XXI, pp. 611 to 614.

596 CYRUS F. TOLMAN

(Clg Ma oieid omen. aes 5= 202%
(Br) eee ee eenTtes
(SO,) - - - 7.692
(COs) ia - - - .207
(Na) ere Maggie cy 30-503
(K) As) aiiea la aa Tl
(Mg) a meat 3.725
(Cay ene igs ene Tao,
99-999

While the average constitution of the salts remains a constant,
the salinity of the ocean is variable. Averaging 327 analyses,
it is found that the average amount of salt is 34.7 grams per
kilogram sea water, or taking the average specific gravity of the
ocean as 1.026, about 35.6 grams per liter.

Applying this to the second table, we find that the total
number of grams of the different ions per liter is as follows:

(C1) - - - - 19.68
(Br) - - - - = 0:07,
(SO,) - - : - 2.74
(CO3) - - - - 0.08
(Na) - - - - 10.89
(K) - - - - =) 10:4
VI Soren Meira oi 1.33
(Ca) - - - - = 0243
35-69
Dividing by the equivalent weights, Dividing the relative strength of the

we find the relative strength of the ions bivelant ions by 2, we find the relative
per liter to be as follows, where the nor- number of ions.

mal solution (one which contains as many

grams per liter as the equivalent weight

of the substance) is taken as unity.

Relative strength per liter Relative No. of ions
(Nee OSS > NG .Colk (Nees Ge. Bebo
(Br) 7 = - 0.0009 ‘“ (Br) i . 2 9
(On v= - OORT? (SO,) : is 285
(CO; = = OLOO27 ean (CO3) if i cf 13
(Na) : ; 0.47 mY (Na) - - - 4700
(IQ) 2 ee LOTR mas (K) aot en SC.
(Mg) z : Osan « (Mg) - 3 e 560

«€a)i = - = O1O22) Ms (Ca) - - =e LO

CARBON DIOXIDE OF THE OCEAN 597

In the light of the previous discussion, we see that there
must be sixteen different salts and eight different ions in the
solution, under the supposition that the salts with bivalent ions
dissociate completely into their metal and acid ions, and always
neglecting the subordinate elements, such as strontium, iodine,
gold, etc. Since, however, in a solution as strong as the sea
water, there are two reactions in the dissociation of the salts
having one bivalent ion, viz.:

+ ae =
Na,SO, => (Na) + (Na) + (SO,)
Na,SO, 2 (Na) + (NaSO,)

there are also these extra ions, viz., (Na SO,), of the bivalent
acids and bases. Also instead of simply the salt of the radical
CO, (normai carbonate) we have both the bicarbonate of the
acid radical (H CO,) and the acid radical itself.

From the propositions of the theory of dilute solutions it is
possible to develop equations whose solutions will give the pro-
portions of the various undissociated salts and of the free ions,
but these computations would be of little value because of their
complexity, and because the ocean water is too strong a solution
for a numerical application of the equations developed for dilute
solutions.

However, assuming that the constant K is of the same order
of value for all the salts, and that the concentration of the free
ions may be expressed by the relative number of ions calculated
under the assumption that the salt is completely dissociated
(see table p. 596), and neglecting the presence of the bicarbonate
ion, we see that the relative amount of the undissociated salts
will be expressed roughly by the products of the concentration
of their respective radicals, and, therefore (from table p. 597) 1)
Na Cl, 2) Mg Cl,, 3) Na SO, exist in molecular form in great-
est quantity, the rest following in about the order:

598 CYRUS F. TOLMAN

4) - - - - - - = CaGly
ye - - - - - - Ke Gl
6) - . - - - - - MgSO,
Tie ic = “ - = = = Na.CO;
8) - - - : - : - NaBr
9) - - - - - : - CaSO7
10) - - - - - - GSO)
In) - - - - - - MgCO,;
12) - - : : - 2 - MgBr,
13) - = - - - - = CaCO;
14) - - - - - - BK COn
15) - - 2 - - - - CaBr,
16) - - - - - - = KBr,

If we examine the following table of Kohlrausch for K Cl
and apply it to all the salts of the ocean, comparing the
strengths of the oceanic solutions with the strengths of the K Cl
solutions given in the table, we can form an approximate idea of
the proportions of the molecular or undissociated salts to their
respective free ions.’

Per cent.

dissociated

N. molecules
I - - - = = = 75
5 - - : . - - = agits)
aI - - - - - - - .86
,oI - - - - - - - BY Loy
.OO1 - - - - - - - .98
.OOOT - - - - - - = = 500

Under N is the strength of the solution where the normal
solution is taken as unity.

From the above table and the one on p. 597 we conclude that
somewhere about 80 per cent. of the sodium chloride is disso-
ciated into its ions. We cannot judge so well about the sodium
sulphate or magnesium chloride, but they also have some con-
siderable amount of molecular salt, possibly more than of the
sodium chloride. The potassium chloride is somewhere around
90 per cent. dissociated, and the potassium bromide, the last of
the series, is practically completely dissociated.

The ocean gases—TVhe gases found dissolved in the ocean

* NERNST: Theo. Chem., p. 314.

CARBON DIOXIDE OF THE OCEAN 599

water are nitrogen, oxygen, argon, and carbon dioxide. The
nitrogen, argon, and oxygen are absorbed into the ocean directly
from the air. Since the ocean is very generally agitated into
waves, we may suppose that the gases dissolved in the outer
portion of the surface water are in direct equilibrium with those
of the air. The surface waters are being saturated with gas at
temperatures varying with the daily and seasonal changes.
Therefore, if there is no depletion or increase of these gases
due to chemical or organic agencies we may assume roughly
that the ocean, on the average, contains these gases in a propor-
tion which may be calculated from the coefficients of absorption
for the average temperature of the surface of the sea, which we
assume to be 15° C. Therefore, to find the average amount of
nitrogen, argon, and oxygen dissolved in the ocean we must
determine their respective coefficients of absorption for sea
water. From the remarks on the effect of salts on the solution
of gases we should expect that the salt water would dissolve a
little less of the above-mentioned gases than fresh water, because
(1) salts in solution decrease the solubility of gases, and (2)
because none of the gases react chemically with the ocean salts.
The following table, which is taken from a larger table of
Dittmar, shows that these theoretical conclusions are correct:

* AIR DISSOLVED PER LITER.!

Pure water Sea water
= 5° - - - - Se meets 272,
oo - - - . 29.54 DOohO
5° - - - - - 26.09 21.08
Io° - - - - - BRB 18.92
15° - - - - =, 21-16 7.17,
20° - - - - ; 19.33 15.72
Die - - - - - 17.80 14.44
307% == : = ; = 16.49 13.44
abe ; 5 : = else 12.53
AO oie = ; : : 14.37
45° 5 : 5 ; = 13+50
50° - - - - 12578

toc. cits, pp. 172 and 175.

600 CVROS Fe LOL MAN.

Taking, therefore, the coefficient of absorption for sea water
as given by Dittmar’, we find that at 15° C. the sea water
dissolves 5.83° of oxygen and 11.34“ of nitrogen and argon,
which is less than shown by the figures given on page 594
for the absortion of pure water. We find on comparing these
figures with the average of the gases as found in the Chal-
lenger analyses that the amount of the nitrogen and argon
is near the amount calculated for the temperature of the water
at the time it was collectéd, as we might expect in view of the
mixing, etc., it undergoes. The oxygen, however, is always low,
as it is used up in the oxidation of the organic matter in the
ocean. It is almost up to the calculated amount in the surface
water but a very large deficit in the deeper water. We may
suppose, then, that the above figure for nitrogen and argon is
approximately correct, but that the oxygen figure is considerably
too high.

It is evident that we have a very different case to deal with
in the solution of the CO, inthe ocean. We have already found
three ways in which the gas is held in solution. (1) Simple
physical absorption; (2) united with the water to form (H,CO, );
(3) held by equilibrium reactions with the salt ions. The total
that can be held in these three ways at atmospheric partial pres-
sure of the gas and at the average temperature of 15° is about
0.3, of (COs per liter onescaywater:

Now, under the assumption that the partial pressure of
the CO, increases with the depth of the ocean; and that the
rate of this increase obeys the same laws as the increase of
atmospheric pressure with the depth of the atmosphere, and,
taking the average depth of the ocean at the large figure of
three miles, we find a formula developed by Professor Woodward ”
that the pressure at that depth is 4.4 that at sea level. Also assum-
ing that a//the ocean is at a temperature of 0° C. (instead of only
the portion at great depths) we find as a maximum estimate the
ocean cannot hold over 2.4° CO, per liter dissolved as a gas,

TAL OCUCIt ep 13 Os

?Communicated in a letter to Dr. Chamberlin.

CARBON DIOXIDE OF THE OCEAN 601

according to the laws of gas absorption; this it is to be noted,
under the unrealizable conditions of a uniform temperature of
o° C. and an average depth of three miles. But Mr. Buchanan
found that on boiling, sea water gives an average 45™8 or 23%
CO, per liter, or ten times the greatest amount the ocean could
hold as a gas under more favorable conditions than those of the
present time. Mr. Jacobson found go™s upon distilling the water
to dryness. Mr. Buchanan thought that this great excess of
CO, over that which could remain in solution under atmospheric
pressure of CO, must be held in some sort of loose combination
with one of the salts, and he decided upon the sulphates as the
retaining agent. Such a misinterpretation, of course, might be
expected at that time from the imperfect knowledge of the
nature of the solutions. Before determining the free CO,, there-
fore, he precipitated the sulphate with barium chloride, and
unfortunately he must have obtained a mixture of Ba SO, and
Ba CO,, so that his numerous determinations are all probably
somewhat too small.

But in spite of this his analyses show that the ocean contains
about eighteen times the CO, of the atmosphere. Now, bear-
ing in mind Professor Arrhenius’ statement, ‘‘that to lower the
temperature of the temperate region 5°, and bring on glaciation,
the CO, of the atmosphere needs to be diminished to from 62
per cent. to 55 per cent. of its present value,’* the following
questions suggest themselves :

1. How is the excess of the CO, found in the ocean at the
present time held in solution ?

2. Is it in equilibrium with that of the air?

3. If so, what proportion of the ocean gas will be brought
out into the air by a diminution of the partial pressure of the
CO, to an amount from 62 per cent. to 55 percent. of its present
value?

4. How much will the consequent fall of temperature
increase the ocean’s capacity for CO, ?

5. What is the relation between these two?

PWocscit. pp:237—270:

602 COVROSTE SD ROLMARN,

In its immediate action, the ocean certainly has a moderating
effect upon the temperature of the land. The great amount of
heat necessary to raise the temperature of the water one degree,
together with its vast evaporating surface, distributes the warmth
received during the day over the night, much of the excess of
the heat of summer throughout the winter, and the great downpour
of radiant energy upon the tropics over the temperate and frigid
zones. Whe question) then arises: In’ the greater cycles ofmthe
variation of the earth’s climate (whether dependent directly or
only in part upon the fluctuations of the carbon dioxide content
of the atmosphere) does the ocean still play the beneficent rdle
of protector against the advances of the greater winters, furnish-
ing the atmosphere some of its enormous supply of CO, asa
blanket against the cold? Or, does the increasing cold cause
the ocean, like a selfish monster, to keep a more grasping hold
on the precious gas as the need of it becomes more imperative ?

1. Besides the CO, which may be absorbed by the ocean
from the air, it receives the gas (1) from the respiration of
aquatic animals (2) from the decomposition of organic matter
(3) from the interior of the earth through springs, etc., and (4)
from the bicarbonates brought in by the rivers.

We find from analyses of the water of the ea rivers*
of Europe, that about 60 per cent. of the entire mineral content
of the river water is calcium carbonate dissolved as calcium
bicarbonate. This calcium bicarbonate then is the great source
of the extra carbon dioxide of the ocean. When this bicarbonate
mixes with the ocean it is no longer strictly speaking, calcium
bicarbonate, but mostly bicarbonate ions in equilibrium with
small amounts of sodium, magnesium, calcium and potassium
bicarbonates.

2. The various bicarbonates have been subject to numerous
investigations since the researches of H. Rose? in 1835. These
contributions show that sodium, potassium, ammonium, and

* BISCHOF, Chemical and Physical Geology, Vol. I, pp. 76, 77.

?Journal fiir Praktische Chemie, Neue Folge 10, 1879, pp. 417-444. Zeits. fiir
Anorg. Chemie., Vol. XVII, pp. 170-204.

CARBON DIOXIDE OF THE OCEAN 603

magnesium bicarbonates, partially dissociate at ordinary temper-
atures into the normal carbonate, giving out CO,. Treadwell
and Reuter have shown in the latest and most complete research
on the subject (see reference above) that when calcium carbon-
ate is dissolved under different partial pressures of CO,, that
the proportion of calcium to carbon dioxide, indicates that prac-
tically a pure bicarbonate, and not a mixture of bicarbonate and
carbonate, is present in the solution.

The difference between the sodium, magnesium, etc., bicar-
bonates on the one hand, and the calcium bicarbonate on the
other is seen from the following: (1) For the dissociation of
magnesium bicarbonate we have in a saturated solution,

Mg (HCO,;), == Mg CO, + H,CO,.

We have seen that the H,CO, is directly in equilibrium with the
CO, in the air; therefore at a given temperature, the degree of
dissociation depends upon the partial pressure of the CO, in air.
With variations of temperature, the colder the water, the larger
is the portion of bicarbonate present, and therefore, the larger
is the proportion of carbon dioxide in the ocean to that in the
air. (2) For calcium bicarbonate we have :

€ai(HiCO,), === CaCO, + H,CO,.

But Ca CO, is very slightly soluble, and therefore practically a
constant for a saturated solution. Therefore, we do not have a
mixture of bicarbonate and appreciable quantities of the carbon-
ate, but the salt in solution is nearly all bicarbonate, and by
lessening the partial pressure of the CO,, Ca CO, is precipitated
from the saturated solution and the bicarbonate decreases.
However, this difference between Ca (THEO) , and Mg
(HCO,), which Treadwell has emphasized, only holds for
saturated solutions. It is evident that for an under-saturated
solution of Ca (HCO,), we may have a larger proportion of
normal carbonate than in the saturated solution and still no
precipitation. Also, in ocean water (see p. 591), the numerous
different salts tend to increase the solubility of the normal

604 CY ROS ES TOLNIAW:

carbonate, and allow perhaps a somewhat greater dissociation of
the bicarbonate into carbonate. The bicarbonate in the ocean
is, as shown above, not calcium bicarbonate, but bicarbonate of all |
the bases in solution, so that Treadwell and Reuter’s investiga-
tions upon pure calcium bicarbonate in saturated solution cannot be
taken to prove that the bicarbonates of the unsaturated sea water
cannot be dissociated.

‘ As direct evidence that the ocean is not saturated with cal-
cium acid carbonate, we find (1) of the many hundred bottles
of the Challenger’s samples of sea water, from all depths and
collected at all temperatures, kept several years, only one or two
showed deposit of lime.t (2) Seashells from the bottom of,
the Pacific show corrosion and resolution.* Pteropod shells and
foraminifera tests are slowly dissolved as they sink. The
Pteropod shells are not found below fifteen hundred fathoms,
and two thousand eight hundred fathoms is the limit for the
globigerina ooze. (3) Thoulet found by actual experiment
that sea water will dissolve calcium carbonate from shells, corals,
etc. (4) Usiglio, studying the evaporation of the Mediterranean
water at Cette, found that no precipitate was formed until the
specific gravity of the sea water increased from 1.02, the specific
gravity of the unevaporated water, to 1.0503 when the first
precipitation begins, composed largely of calcium carbonate with
ferric oxide.5

DEGREE OF BICARBONATE DISSOCIATION.

From twenty-seven analyses by Jacobson, we find an average
Of O1.47% per liter of tree CO, and 12072 °CO. inethe monmmal
carbonate, or the bicarbonate is so dissociated that 25 per cent.
of its second equivalent of CO, is lacking.®

THEOCACIt Pz 2.

2JouR. GEOL., Vol. I, p. 504.

3 Loe. cit., p. 221.

4Comptes Rendus, Vol. CVIII, p. 753.

5Encyl. Brit., Vol. X XI, p. 229.

®Uber die Luft des Meerwassers Ann. der Chemie und Pharm., Vol. CLXVII
(1873), pp. 1-38.

CARBON DIOXIDE OF THE OCEAN 605

From several hundred determinations of Buchanan, we strike
diveaverase, Of 45" tree CO. per liter, to, 53.472 CO,” per
liter of the frst equivalent, z. e., only 84 per cent. of the second
equivalent is found in the ocean. Mr. Jacobson’s analyses show
a larger per cent. of the carbonates than were found in the
Challenger’s samples, which might be expected, as Jacobson’s
were collected only trom the North Sea into which flow the great
lime-bearing rivers of northwestern Europe.

To prove positively that the ocean bicarbonate dissociates
into carbonate and free CO,, Professor Ditmar shook in the air

Jom porature.

Volume dissolved.

iS 7 tb 14 “A Ld oe

Fics. I and 2 represent respectively the effect of temperature on the solubility of
CO, in pure water, and upon the dissociation of Na H CO,.

Fic. tis taken from table on page 593 and under 760 mm pressure CO,. The
temperature is recorded on the ordinate, and on the abscissa are the volumes of CO,
»bsorbed, compared with the volume of water in which it is dissolved.

a sample of sea water, that had an excess of CO,, and found
that CO, was given off, and that the ratio of the two equiva-
lents was 100:84 at 13° C., exactly the same, it happens, as we
found from averaging Buchanan’s analysis. Therefore we may
consider it as certain that the largest part of free CO, in the

606 CYTOSOL MAW,

ocean is held as the second equivalent of bicarbonate, and that
this is held in equilibrium with the gas in the air.

We know then from the above that the dissociation of the
bicarbonate is a function of the temperature, and also of the
partial pressure of the superincumbent CO,. The solubility of
CO, as agas not attached to form bicarbonate, is also a
function of temperature and pressure, but that these functions
are not the same, may be seen from an inspection of the

Discociation Jension, in mm Niercary.

Loo 20 400 Sto ba0

Fic. 2 is plotted from Dr. Dibbett’s tables.* On the ordinate are the temperatures
and on the abscissa the increase of the dissociation of the Na H CO, in mm of mer-
cury which represents the loss of the second equivalent of CO, from the solution.

accompanying curves. Professor Ditmar has experimented upon
the effect of changes of partial pressure and temperature upon
the CO, in the ocean. This includes both the effect upon the
portion simply dissolved and that as second equivalent of
bicarbonate. We shall discuss these results under Professor
Arrhenius’ hypothesis of lowering the surface temperature to

*Ueber die Loslichkeit und.die Dissociation des sauren kohlens Kaliumes, Natri-

urns und Ammomiums, Journal fiir praktische Chemie, neue Folge 10, 1879, pp. 417-
444.

CARBON DIOXIDE OF THE OCEAN 607

an average of 10° C., and the diminution of the partial pres-
sure he has postulated as sufficient to cause this drop in temper-
ature.

We find from Professor Ditmar’s investigation (see tables and
figures, pp. 609 and 610) that as the waters of the ocean become
warmer, the effect of a change in the partial pressure of atmos-
pheric CO, upon the bicarbonate dissociation becomes greater,
while near zero a change in partial pressure has no effect on
the dissociation of the bicarbonates of the ocean. On the

Sa

6

# &

Volume dissolved.

0 h y z s

Fics. 3 and 4 show the relation between the partial pressure of CO, and its solu-
bility in pure water on the one hand and the solubility of Ca Hy (CO3), on the other.

Fic. 3 represents the simple law of gas absorption that the amount dissolved is
directly proportional to the partial pressure. The pressure is plotted on the ordinates
in mm of mercury and the volume of gas absorbed on the abscissa.

other hand, the effect of any postulated fall in temperature,
causing the bicarbonates to take up COg, is the greatest at the
temperature just above 0°, and becomes less for higher temper-
atures. So that a fall in temperature of the colder waters of
the ocean is correlated with the greatest absorption of CO,, and
without the counteracting effect of decreasing partial pressure.
In equatorial waters, however, the fall in temperature does not

608 CYRUS F. TOLMAN

produce so great an increase in the absorption of the CO,, and
the effect of decreasing tension of atmospheric CO, approaches
a maximum.

These facts, therefore, naturally divide the discussion into
three parts. Under Professor Arrhenius’ postulates as to change
in temperature and pressure, we shall discuss the relative effect
of these two opposing factors in the temperate waters whose
temperature is the average surface temperature of the ocean,
viz., 15° C. (2) Ditto for the tropical waters whose temper-
ature is above 15° C. (3) Ditto for the polar waters whose
temperature is below this.

>
6,
3
5
a £
FS
:
Z a

Ca (H COs), in omy. per litre

0 20 #0 60 By Ji [26

Fic. 4 is from Treadwell’s and Reuter’s dissertation (see reference, p. 603). The
partial pressure is represented on the ordinate in mm of mercury and the amount of
calcium bicarbonate dissolved in m. g. in the abscissa. At atmospheric pressure 15°
C. the amount dissolved in pure water at saturation is 38.5 m. g. per liter, which is
much less than the amount of bicarbonate in the sea, as we might expect from the
previous discussion.

The only experiments which have been made upon sea water
(and so under the actual conditions of the problem) are repre-
sented in Fig. 5. Professor Ditmar took a special sample of
deep ocean water which was so charged with CO, as to have its
bicarbonate fully saturated with CO,. This he shook violently
in a bottle constantly renewing the air until there was no more

CARBON DIOXIDE OF THE OCEAN 609

loss of CO, from the water and no more gain in the air above
the water. The carbon dioxide remaining in the water was thus
determined, and the degree of the bicarbonate dissociation cal-
culated. This was repeated for various temperatures.

The table is as follows :*

t N Pure Air Ordinary Air
(n.) (n r)
2 200 1.90
2 200 2.04
2 52 2.06
fe) 200 1.70
13 50 : 1.84
15 100 1.63
15 200 1.50
20 200 1.42
25 53 1.53
32 52 1.33
32 52 1.89
32 150 In6¢

equals temperature. N-number of times air was renewed
until loss of CO, from water ceased. n,=ratio of first to the
second equivalent of CO, in bicarbonate when shaken in air
free from CO,, where 2.00 represents fully saturated bicarbonate
and 1.00 simply the normal carbonate. n,=the same for ordi-
nary air.

These experimental data do not permit the drawing of any
very accurate conclusions. Professor Ditmar states that these
are only preliminary, and has promised us a completion of this
work, which we await with impatience. However, we must
needs use what we have, and referring to curve 5, we see that
at 15° the ocean will contain about 83 per cent. of the total
second equivalent of CO,,and at 10°, about 88 per cent. of it,
or an increase of 5 per cent. of the second equivalent which is
represented by the line a—é in figure. For pure air artificially
freed of CO, at 10° the dissociation goes through 70 per cent.
but Professor Arrhenius does not postulate a complete removal

Enyce. Brit., Vol. X XI, p. 612.

610 CYRUS F. TOLMAN

of CO, from the air, but a diminution of from 62 per cent. to
55 per cent. of the present partial pressure of the gas, and this
decrease in dissociation caused by the decrease of the partial

25"|

£0"

Jemperaturo,

wT

Frepertion of bicackonate dissociated.

200 1b [kb L70 160 40

Fic. 5 is plotted from Professor Ditmar’s table on page 609. The figures in the
table are not very constant, but we have taken those that seem to correspond best with
each other. On the ordinate are the temperatures, and on the abscissa the dissocia-
tion of the ocean bicarbonate, 2.00 representing fully saturated bicarbonate and 1.00
normal carbonate, the partial pressure of CO, in the curve (1) is that of the atmos-
phere as it is at the present time and for curve (2) there is 0 pressure of that gas.
The two curves have been plotted arbitrarily to cut a 0°, but Professor Ditmar shows
that there is probably no dissociation at 2° to 3° above zero.

The line cf connects the two curves at 10° (the temperature of the temperate
regions Dr. Arrhenius postulates to develop a glacial period) and the points d@ and e
show the bicarbonate dissociation at a partial pressure of CO. reduced respectively to
62 and 55 per cent. of its present value. a@ 6 represents the decrease of the dissocia-
tion of the bicarbonates due to fall of temperature from 15° to 10°) andc¢cd and c e the
increase of the dissociation due to a decrease of 62 per cent. and of 55 per cent. of the
present value of the partial pressure of CO, inthe air. a@' 6’ andc'd' andc’ e’
represent the same factors for a decrease of temperature from 21° to 16° and the same
decrease as postulated above in the partial pressure of the CO,.

pressure of the gas is represented by lines c—d and c-e; so that
the dissociation will be between the two, that is, viz., from 76
per cent. to 81 per cent.,z. ¢:, these data show that) the falling

CARBON DIOXIDE OF THE OCEAN 611

temperature counteracts within 2 per cent. to 4 per cent. of the
total CO, as second equivalent, the effect of the decrease in
the partial pressure.

These estimates are of course founded on too small an experi-
mental basis, and the data themselves show too great disagree-
ments to conclude that the decrease of the dissociation due to
the falling temperature, counteracts exactly within 2 per cent. to
4 per cent. of the second equivalent of CO,, the increase due to
the diminishing partial pressure ; but we may conclude ‘hat they
ave probably of the same order of magnitude, or that a—d is com-
parable in length with c—d or c-e.

All this however, is under the proposition of Professor
Arrhenius, that a 5° lowering of the average climate of the
temperate regions will bring on glaciation. We have still to con-
sider the effect of the waters of the equatorial region on the one
hand, and those of the higher latitudes on the other.

The average temperatures of the ocean waters at the surf
line between 45° north and south latitudes, are as follows :?

For the belt between 15° north latitude, and 15° south latitude, 26 degrees
centigrade.

For the belts between 15°-30° north latitude, and 15°—30° south latitude,
21 degrees centigrade.

For the belts between 30°-45° north latitude, and 30°-45° south latitude,
17 degrees centigrade.

The average temperature between 45° north latitude and Ate
south latitude, at the depth of 1500 fathoms is between 2°—3°
centigrade.

Professor Ditmat has found that at temperatures between
18°—21° C. that the dissociation tension of the bicarbonates of
the sea water is five ten-thousandths of an atmosphere. On the
other hand, at temperatures near zero, the dissociation does not
take place, and the tension of course becomes nil. (See table
above. ) |

The partial pressure of the CO, in the atmosphere at the
present time is about three ten-thousandths. Therefore, he con-

‘Compiled from tables Challenger’s Rep., Vol. I, Table VI, at end of volume.

612 CYRUS F. TOLMAN

cludes that the warmer portions of the ocean are constantly
supplying CO, to the atmosphere, and the colder portions are
always removing it.’

The falling temperature which causes the glacial period must
affect the temperature of the surface of the equatorial water,
especially after an ice advance is inaugurated, but how much we
cannot estimate. Taking the average surface temperature of
these waters as 21°, and postulating the same fall of tempera-
ture as for the temperate waters, we see that the line a’ 0’ rep-
senting the decreasing dissociation due to the falling tempera-
ture, is much shorter than the line c’d’ or c’ e’, representing
the increase in the dissociation caused by the decreasing partial
pressure of CO,. However, the data upon which this part of
the curve is based are much more conflicting and less satisfactory
than those represented by the curve at 10°. But we may con-
clude that in the equatorial region the diminishing partial pres-
sure has a greater effect than the postulated fall of temperature.
But, with the increasing cold, the heated areas which can
give off carbonic acid to the air are greatly diminished, espe-
cially after the glaciation has commenced, and this acts directly
counter to the diminishing partial pressure.

‘In the northern seas whose surface temperature is near zero,
each molecule of carbonate has the power to take up carbonic
acid until it becomes a fully saturated bicarbonate. Just how
much increase this area will undergo on an approach of a glacial
period we cannot well estimate, but perhaps we can get a fair
idea of it by comparing the area of the ocean contained within
the circle of latitude which bounds the northernmost point of
Greenland glaciation with that contained within the circle bound-
ing the southern limit of Pleistocene glaciation. The ratio
- between these two areas is 2:5. These figures may not even
approximately represent the real increase of the cold waters
during glacial times, but they emphasize the fact. of an actual
and great increase in the amount of these waters.

The table on p. 609, as stated before, shows that at low tem-

tChal. Rep., Vol. I, pp. 212, 213.

CARBON DIOXIDE OF THE OCEAN 613

peratures the decrease in the partial pressure of the atmospheric
CO, has practically no dissociating effect upon the bicarbonates
of the ocean, and therefore that the large increase in the
capacity for absorbing CO, is not affected by the diminishing
partial pressure.

To sum up then: (1) the increase in the ocean’s capacity for
CO, at low temperatures, and (2) the invasions of the polar
waters toward the equator, both tend directly to rob the atmos-
phere of CO,, unaffected by any diminishing partial pressure of
that gas. In the temperate waters the effects of increasing cold
and decreasing partial pressure seem to be fairly evenly bal-
anced, with a possible advantage for the diminishing partial
pressure, against which must be reckoned a decrease in the
amount of these waters. In the equatorial waters the effect of
the decreasing partial pressure exceeds that of falling tempera-
ture, counterbalanced by a large decrease in the amount of
these waters.

This division of the ocean with three belts shows us clearly
the factors in the problem, but does not give us means by which
to find the relative values of these factors—that is, to show us
whether or not the intensifying factors, such as falling tempera-
ture and increasing areas of polar waters and decreasing areas
of equatorial waters, more than counteract the effect of the
diminishing partial pressure of the CO, over the temperate and
equatorial waters.

In order to get some rough comparative value of these fac-
tors without pretending to get any accurate quantitative estimate
of their actual value, we have tried to estimate the volume of the
ocean water, whose temperature is reduced from 7° to 2°, from
12° to 7° and from temperatures above 12°, etc., and to calcu-
late the amount of CO, these volumes of the waters can absorb
on account of their lower temperature on the one hand and to
estimate the greatest amount of CO, that might be freed from
the tropical waters compatible with their restricted volumes on
the other hand.

As shown in Fig. 6, we have assumed that the polar waters

614 CVROS Fa TOLMAN,

(viz. those with temperature of 2°-3° C.) will advance south-
ward at least as far as the southernmost limit of the ice-sheet.
Therefore, we have started the line a 0 at 60° N.and S. latitude .
(the latitude of the southern Greenland glaciation) and the line e
h at 37° (the latitude of the southernmost Pleistocene glaciation
in North America). With this postulated southern advance of
the cold waters, there must also have been a rise of these cold
waters toward the surface. The amount of this rise is undeter-
minable at present. But since we have used Dr. Arrhenius’
estimate of a drop of 5° in the temperature of the surface waters,
we may assume the same fall of temperature for the body of the
ocean. A given fall in temperature of the surface water must

4% LAT. is,
fe" 7° ra

as

60° 45? Jo* 17 OF Sa Jo? #5? 60° Se B®
ec a e r x —— Jo eee) o Cc
4 =z
$00
lam —.
¥

(320)

tow

Fic. 6.—Section of ocean from north to south pole. Ocean taken at average
depth of 2000 fathoms. Portion below 1500 fathoms has temperature below 2° to 3° C.

Line adc incloses section of ocean whose temperature is now above 2° to 3°.
Line e fA limits the equatorial and upward migration of the polar waters during maxi-
mum Pleistocene glaciation, when the ice reached the latitude 37° N.

Line m & x ditto for waters with Pleistocene temperature of 2° to 7°.

Above line # & # ditto for water of higher temperature.

take a very long time to communicate itself throughout the body
of the ocean, but the larger the period during which the surface
waters maintain their low temperature the more completely does
the body of the ocean lose its extra heat.

At 1500 fathoms the temperature of the temperate and
equatorial waters is 2°-3° C. above zero; therefore, the maxi-
mum depth which the line a—c reaches is placed at d. At 300
fathoms the warm waters have a temperature of about 7°.
Therefore, we place here f on the line ef, designating the
maximum advance upwards of the polar waters.

Point & on m-k-n is 150 fathoms below the surface and at that

‘ All temperatures calculated from tables of temperatures, given in Vol. I of the
Challenger Reports.

CARBON DIOXIDE OF THE OCEAN 615

depth the equatorial waters have average temperature of 12°.
Therefore, this will be the limit of the waters of the belt that
had temperatures of 2° to 7° during maximum glaciation. Above
K are the waters which now have temperatures above 12°, and
during glaciation temperatures above 7°.

To get a correct conception of this section of the ocean
waters from pole to pole, we must multiply the length given
here by 550.

The portion of the ocean below 1500 fathoms is already
down to the limiting temperature; therefore, its carbon dioxide
content is not subject to fluctuations. This leaves out of the 18

5)

atmospheres of ‘free’? CO, about 13 atmospheres above the
1500 fathom line.

The volume of these waters is divided as follows:

go° to 60° N. and S. latitudes, - - - 11%
60> tor3'7: sc gs = = = 2
B77 to 6° “ ““ x = 5 65

Now, the volume of water included between adc and efh
is considerably over one half that above the 1500-fathom line,
or it holds about seven atmospheres CO,, and a change of tem-
perature from 7° to 2° represents a change in the dissociation
otsthe bicarbonates. from 1.9 to 2:00 (see Pig. 5; p. 610): or
more than a 10 per cent. increase in the ‘free’ CO,. . Therefore,
this advance of the cold waters upward and toward the equator
represents an increased capacity of the ocean for CO,, equal

to about seven tenths that of the present atmosphere.
The waters above mun represent those which now have a

temperature above 12° C. (we neglect the warm surface waters
now spread far poleward by the warm currents), and it 1S in tne
warmer of these waters that the diminishing partial pressure of
the CO, may cause a loss of CO, from the ocean.

Now this volume represented by m £m is considerably less
than 2 per cent. of the volume above the 1500 fathoms line, so
that for a limiting case if ad? the second equivalent were lost in
these waters, instead of only at most a small portion of it, it would
amount to less than one third that gained by the advance of the

616 CYVROSSESTOLEM AN:

cold waters, and in the actual case probably not more than one
fortieth of the same.

Admitting all the inaccuracies of our assumption, still it
seems to be clear that with falling temperature ¢he ocean will dis-
solve CO, from the air.

The effect becomes more pronounced as the glaciers become
more extensive and thus directly chill the ocean waters. We
offer this as the most important accumulative factor causing the
great extent of the glacial invasion, acting until overcome by a
number of opposite agencies.

Dr. Chamberlin’ has shown that the amount of CO, in the
atmosphere at any one time, and therefore the climate of the
earth at that time, depends upon the value of the ratio of the
supply of the gas to its depletion. Besides the continuous sup-
ply that the atmosphere receives from the interior of the earth
and from planetary space and the continuous depletion due to
the formation of the carbonates in place of the igneous alkali
earth silicates, there are variations in the ratio of supply to
depletion dependent upon the attitude of the land and water.

A large exposure of land surface is correlated with a rapid
solution of calcium and magnesium carbonates, and this solution
is accompanied by a change from the normal carbonate to the
bicarbonate form, and therefore represents a loss of CO, from
the atmosphere.

On the other hand the formation of the normal carbonate by
lime-secreting animals causes a direct liberation of the second
equivalent of the bicarbonate. Therefore extensive oceans and
abundant marine life are correlated with warm climate, and
restricted seas and elevated land cause loss of CO, and colder
climate.

Now, to investigate the réle the ocean plays in this conflict :

1. The chief agencies in the removal of the carbon dioxide
from the air are (a) the formation of the carbonates from the
silicates ; (b) the solution of the carbonates as bicarbonates.
These are dependent upon the attitude of the land and water,

*See PROFESSOR T. C. CHAMBERLIN, JOUR. GEOL., Vol. V, p. 682.

CARBON DIOXIDE OF THE OCEAN 617

the elevated land being accompanied by rapid disintegration
and erosion. The increasing cold only slightly affects this
process (a’) by the decrease in vegetation; (b’) by the slight
decrease in chemical activity of the CO,; (c’) by the freezing
of the ground, preventing free percolation of the underground
water, etc. But it aids disintegration by frost action, etc. (c)
The polar seas constantly absorb CO, from the atmosphere.
The increasing cold, with the increasing volume of cold waters,
therefore adivectly robs the atmosphere of the CO,. This process
is not so marked in the warmer waters, because of the counter-
acting effect of the postulated diminishing partial pressure of
CO...

2. The supply of CO,, outside of that of plutonic and extra-
terrestrial origin comes (a) from the dissociation of bicarbonates
in equatorial waters. The decreasing partial pressure aids this
and the restricted area of warm water counteracts it. (b) The
second equivalent of bicarbonate freed by lime-producing ani-
mals. The fall of temperature directly affects this most impor-
tant source of supply, as it is well known that a fall of a few
degrees in the ocean water would wipe out whole genera of test-
producing animals.

To sum up, then: Accepting Dr. Chamberlin’s proposition
that the advance of a cold period is primarily dependent upon
the altitude of land and water, the effect of the ocean is both to
remove the atmospheric carbonic acid gas by the southern and
upward invasion of the cold waters, and to decrease the supply
of CO, to the atmosphere by the destruction of the lime-secret-
ing animals. Therefore we conclude that the ocean very greatly
entensifies the secular variation of the earth's temperature, although
acting as a moderating agent in the minor cycles.

It is interesting to note what a different state of affairs we
would have if the CO, in the ocean were simply dissolved as a
gas from the atmosphere according to the laws of gas absorp-
tion. A diminution of the partial pressure of the CO, in the
atmosphere, as postulated, would bring out of the ocean 38 to
45 per cent. of its great store of CO,. A lowering of 5° in

618 CYRUS F. TOLMAN

temperature from 5° to 0° would only produce an increase in the
solubility of the gas of 24 per cent., and from 20° to 15° of 14
per cent., and so, under such conditions, an excess Of 14 stort
per cent. of all the CO, in the ocean would have to be removed
and consumed before a cold period could be inaugurated.
Although future investigations may cause a modification of
Dr. Arrhenius’ estimate, and such a change will affect some of
these conclusions, the principles on which they are based will
not be affected. If it be found that on account of certain
intensifying agencies, or for other reasons, it is not necessary to
postulate so large a decrease of the CO, of the atmosphere, or if
this decrease is accompanied with a greater fall of temperature
than 5°, then the depleting effect of the ocean will become more
marked. If, however, the estimated decrease of the atmospheric
CO, is too small, the intensive effects may be lessened, but

probably not completely destroyed.
Cyrus F. ToLman, Jr.

te DI TORIAL

Ir is gratifying to know that the excellent work of the
Missouri Geological Survey is to be continued and that it is
even proposed “to eliminate all ornamental or irrelevant fancies
and go directly after the fundamental facts which make the only
logical foundation for a geological survey.’ It is true that
among the ‘“‘ornamental”’ facts to be eliminated are such things
as ‘Engineering Instruments, Photographic Apparatus, Labora-
tory Equipments” and a few others which ordinary geologists
have come to consider indispensable. However, it is no ordi-
nary man or ordinary plan of work that Missouri now has on its
hands. In a recent St. Louis interview the state geologist
announces that ‘‘The rocks have never been differentiated in
Missouri and Arkansas ’’—thus setting aside at one stroke of the
pen all the results of former work in the region. Fortunately
such a dire condition is not to be allowed to continue, and the
new state geologist proposes to issue at once a preliminary report
in which ‘1. will differentiate the rocks: to a finish.* He also
proposes to give ‘photographic views of two or three of the
best exposures of each rock in the state,” from which we may
infer that since his Azennzal Report was issued he has fallen into
evil ways and has begun to lean a little on the ‘‘ ornamental”
and ‘‘irrelevant’”’ aids of other members of his profession. This
new work is to be very thorough and the sedimentary rocks are
to be taken, “one at a time, irom Z to A.”

Incidentally he will courteously give in the report a synopsis
of a new ‘‘cosmic philosophy” which he has worked out ‘ with
only physics, logic and consciousness as guides.” With such
noble companionship it is no wonder that ordinary grammar is
considered out of place. At least we may judge this to be true

from such statements as, ‘‘ Several dykes of diabase were crossed
619

620 EDITORIAL

in the county, as well as rumors of rich deposits, etc.”* This
sentence gives one some new light on classification and will per-
haps obtain for the doubter pardon for his skepticism whether
the new differentiation is to be so very thorough after all.
When diabase dikes and rumors are classed together, there seems
room for doubt as to the closeness of the classification. How-
ever, all things are possible to one who can explain dolomite as
formed in Sargasso seas and can settle the glacial problem in
one short page. The proposed preliminary report will be
eagerly awaited ; the Azennial is all too brief a pleasure.
lefale 18.

t Biennial Report of State Geologist, 1898, p. 36.

REVIEWS.

The great Ice-dams of Lakes Maumee, Whittlesey and Warren. By
FRANK BurRsLey TayLor, Fort Wayne, Ind. American
Geologist, July 1899, Vol. XXIV, pp. 6-38, Pl. II and III.

Two years ago Mr. Taylor contributed to Pleistocene geology a new
working hypothesis.’ Pointing out that the recessional moraines left
by certain lobes of the Laurentide ice sheet on plains or in broad
smooth valleys were characterized by regularity of interval, he postulated
that this regularity was caused by a definitive rhythm in the general
conditions controlling the magnitude of the ice-field; whatever may
have been the cause of the general wasting of the ice, its action was
modified by a concurrent cause of a rhythmic nature, which alternately
promoted and opposed the wasting. Under the joint action of the two
causes the ice front first retreated with comparative rapidity, then
halted, readvanced slowly over part of the abandoned territory, and
finally halted a second time before beginning a second cycle ; and each
recessional moraine marks the position of the ice front at the close of
such a cycle. This hypothesis, if well founded, is of far reaching
importance. It affords a basis for the correlation of moraines in widely
separated districts, and for the mapping of the ice sheet at various stages
of its final waning. It affords a regularly graduated chronologic
scheme of classification. It leads to an estimate of the duration of a
definite portion of geologic time, far superior to any based on phenom-
ena of erosion. And it probably assists in the discussion of the cause
of the ice age.

When the hypothesis was first presented it was applied to the mak-
ing of a time estimate. In the present paper it is applied to local
geology, the correlation of moraines and associated phenomena in a
district about Lakes Erie and Huron. After a general discussion of
the function of the ice front as a dam to retain glacial lakes, and of the
theoretic relations of successive positions of the dam to cols, and the

™ Moraines of Recession and their Significance in Glacial Theory. JOUR. GEOL.
Vol. V, 1897, pp. 421-465.

621

622 REVIEWS

resulting location of shore lines and channels of outlet, an account is
given of the actual positions of the ice-dam within the district and of
the resulting series of glacial lakes. A map of moraines includes not
only data from various sources previously publisht, but important new
material, especially for the Canadian peninsula, and is adjusted to the
subject in hand by the indication of the theoretic continuations and
connections of partly surveyed moraines. Other maps show the glacial
lakes, outlined with detail and confidence not only on the land side,
where their shores are still preserved as dry beaches and terraces, but
also the ice side, where all actual vestige has necessarily disappeared.

Lake Maumee, in the western part of the Erie basin, lasted during
three oscillations of the ice front, growing larger with each shitting of
the dam. At first its discharge was at Fort Wayne and thence down
the Wabash River; afterwards part of its surplus escaped across the
“thumb” of Michigan at Imlay, running westward to the Lake Michi-
gan basin. In the later part of its life the broad upland of the penin-
sula of Canada was a nunatak. Lake Whittlesey, succeeding Lake
Maumee in the same basin, held place for a single morainic cycle. The
Canadian upland, no longer a nunatak, formed part of its northeastern
shore, separating two ice lobes. Its discharge crost the thumb of
Michigan at Ubly to a lower glacial lake, Saginaw, and thence ran
westward through the Pewamo channel across the lower peninsula of
Michigan. Lake Warren, uniting Lakes Whittlesey and Saginaw, at
the level of the latter, endured for four morainic cycles, being
greatly modified in outline by the successive changes of the retaining
dam and becoming eventually much larger than its predecessors.

It is to be noted that the author did not delay the publication of
his generalization until the ground had been wholly covered by obser-
vation nor until all the observations made use of had been verified.
While guarding against misapprehension by constantly drawing the line
between fact and theory, he has freely used his working hypothesis for
purposes of local interpolation. ‘To whatever extent his local gener-
alizations are deductions from theory they will eventually, through
the extension of observation be made to serve as tests of the theory.

Taylor dwells on the peculiar significance of the Ubly channel as
an evidence of the existence of glacial lakes and a glacial dam, and
closes with a general argument (drawn out by criticisms of J. W.
Spencer) in support of the fundamental theory that the ice sheet
served as a dam for the retention of lakes.

REVIEWS 623

A corollary of some interest, not mentioned by the author, relates
the history recorded by recessional moraines to that associated with
Niagara gorge. From the beginning of the last ice retreat at Cincin-
nati Taylor counts seventeen moraines to Rochester, beyond which
point new conditions enter, making the continuance of the analysis a
matter of great difficulty. But just at the close of the term represented
by these moraines the Niagara began its work, so that the moraine
history is complemented by the river history. ‘Together they represent
all the time since the latest ice maximum, a period whose measure-
ment in years is far more valuable to science than the determination
of the age of the great cataract. Postulating the astronomic cycle of
the precession of the equinoxes as the cause of the morainic cycle, tine
approximate time covered by the morainic history is computed (by the
reviewer) at 315,000 years. This is so long a period in comparison
with the most ample of modern estimates for the age of the Niagara
that the uncertainty as to Niagara’s age is of little moment in consider-
ing the sum of the two periods. Broadly stated, the hypothesis that
the recessional moraines are functions of the precessional cycle esti-
mates the time since the last maximum of glaciation at 300,000 to
400,000 years.

GLK G.

The Influence of the Carbonic Acid in the Air upon the Temperature
of the Ground. By PROFESSOR SVANTE ARRHENIUS. Philo-
sophical Magazine and Journal of Science, Vol. XLI (Fifth
Series) 1896, pp. 237-276. La Revue Générale des Sciences,
Mai, 1899, pp. I-22.

Professor Arrhenius was led to investigate this subject by the debates
among the Swedish geologists upon the cause of the glacial and inter-
glacial climates of the Pleistocene. The conclusion that none of the
current hypotheses are satisfactory or at all competent to explain the
observed phenomena led him to calculate the quantitative effect of any
given variation in the amount of atmospheric carbon dioxide upon the
temperature of the earth’s surface. The fact that the carbon dioxide
and water vapor are the chief agents in retaining the heat radiated from
the earth’s surface had long been known qualitatively and even the
relative values of the selective absorption of radiant energy for the
various atmospheric gases had been determined, but it remained for

624 REVIEWS

Professor Arrhenius to show the exact effect of any given change in
the carbon dioxide content of the atmosphere upon the surface tem-
perature of the earth.

The essential work of the physicist and mathematician having now
been done by him, it remains for the geologist .to investigate the various
sources of supply and depletion of carbon dioxide and to determine if
possible if there have been any variations of such an order of magnitude
as to produce the results observed.

Professor Arrhenius explains in his papers that the air retains heat
(light and dark) in two different ways: (1) The heat suffers a selective
diffusion as it passes through the air. This is greatest for the rays
having short wave-lengths (ultra-violet) and insensible for those of long
wave-lengths which form the chief part of the radiation of a body of the
temperature of the earth, viz.,15° C. (2) The gases themselves have
the power of absorbing selectively the light and heat of certain wave-
lengths. The carbon dioxide and the water vapor have this power of
selective absorption to a far greater extent than the oxygen, nitrogen
or argon, and this absorption is not distributed evenly throughout the
spectrum but occurs in certain definite bands which are best developed
in the ultra-red portion which represents the rays with long wave-lengths
such as are given off by bodies with a low temperature.

There are two ways in which to measure the amount of the heat
absorption by the carbon dioxide and the water vapor: (1) by measur-
ing directly the amount of heat absorbed by such quantities of these
gases as they appear in the atmosphere, and at a temperature of
15° C., and (2) by measuring the amounts of heat received from the
full moon at different heights above the horizon. ‘The amount of car-
bon dioxide through which the rays pass is evidently a function of
altitude of the moon above the horizon, while that of the water vapor
depends both upon the altitude and the humidity of the air.

Professor Arrhenius takes the second method and from Professor
Langley’s observations on the heat received from the full moon at
various altitudes above the horizon he calculates the amount of heat
absorbed by the two gases by an atmosphere having the present average
amount of carbon dioxide and the average amount of water vapor,
viz., ten grains per cubic meter at the earth’s surface. The full moon
has, however, a surface temperature of 100°, and he introduces the
corrections necessary to apply the above to a body with the temper-
atumerOLenigie Ke:

6

REVIEWS 625

With these data it is not difficult to calculate the effect of any change
in the amount of carbon dioxide upon the temperature of the surface
of the earth. The temperature of the earth’s surface is theoretically in
equilibrium with that of the atmosphere. Now if by any increase in
the amount of the carbon dioxide the atmosphere retains more heat
than before, it will radiate more heat to the surface of the earth. ‘The
‘surface temperature then will rise until there is again an equilibrium
between the two. This rise is governed by Stefan’s law which states
that the intensity of the radiation is proportionate to the fourth power
of the er

From these data Professor Arrhenius finds that if the carbon dioxide
is increased 2.5 to 3 times its present value, the temperature in the
arctic regions must rise 8° to 9° C. and produce a climate as mild as
that of the Eocene period. A diminution to 0.62 to 0.55 of its present
value must cause a fall of from 4° to 5° C. and give us a glacial period.

It is to be noted that in every case throughout the calculation Pro-
fessor Arrhenius has preferred to slightly underestimate the effect of
the carbon dioxide than to risk a possible overestimate. Also where
he has been compelled to use interpolation the limit of error has been
well within the degree of accuracy of the observations upon which they
are founded.

The tremendous interest of these considerations, not only as a basis
for the interpretation of the past history of the globe but also for the
prophecy of its future, demands an investigation of the problem along
the lines of direct experiment, as a supplement to the elegant calcula-
tions of Professor Arrhenius. Cyrus F. Touman, Jr.

Special Report on Gypsum and Gypsum Cement Plasters. By G. P.
GrimsLey and E. H. S. Baitey. University Geological
Survey of ‘Kansas, Vol) V. Pp. 183,30 plates. Topeka,
1899.

Among the minor mineral industries of the country those connected
with gypsum have been, so far as literature is concerned, heretofore
neglected. The present report is accordingly particularly welcome.
‘The papers so far accessible have been, in the main, devoted to the
description of local deposits and the technology of the gypsum industries
has not been described before in any adequate manner. ‘The present
volume includes not only a description of the Kansas gypsum. beds

626 REVIEWS

but brief notes on the gypsum of other states and countries and a full
discussion of the mining and milling processes. The body of the work
is by Dr. Grimsley while Professor Bailey contributes a welcome chapter
dealing with the chemistry of the subject.

In 1897 Kansas produced 50,045 tons of gypsum which had a value
of $252,811. It was a little behind Iowa in production and ahead in
values; the difference being in the large proportion of the Iowa prod-
uct sold as land plaster. Aside from these two states Michigan and
New York are the main producers. The Kansas gypsum is found in
three fields; the Northern or Blue Rapids area mainly in Washington
and Marshall counties, the central or Gypsum City area of Salina,
Dickinson, and Marion counties, and the southern or Medicine Lodge
area in Comanche and Barber (misprinted Barton on map) counties.
The beds occur in the Permian of Prosser’s classification and the
deposits include the original rock deposits and the derived gypsum
earths which are of recent origin. These gypsum earths are the dis-
tinctive beds of the Kansas-Oklahoma district and are thought to be
marsh deposits deriving their peculiarities from the secondary deposi-
tion of gypsum in clays. ‘They are used in the production of gypsum
cements and are mined by ordinary surface methods. The rock
gypsum is won by underground mining on a room and pillar system,
of which a more detailed account would have been valuable, and are
used in the production of plaster of Paris and other products.

The Kansas milling practice does not seem to differ from that of
other districts especially, though the Stedman disintegrator has been
introduced and a cooling air blast is used at one point to elevate the
calcined plaster. Here as elsewhere grinding is in the main done by
stones and it seems peculiar, in view of the great progress of recent
years in fine grinding machinery, that the numerous experiments in
the direction of cheaper and more expeditious grinding have never
borne fruit inthe gypsum industries. Burning is done in the ordinary
Marsh calcining kettle. It would seem that in the case of the gypsum.
earths at least the rotary furnaces now so much used could be applied
to advantage.

In the discussion of the set of the plaster Dr. Grimsley has con-
tributed some highly interesting and valuable microscopic studies in
which he shows, in brief, that the strength of the set plaster depends.
upon the formation of a network or felt of fine lath-shaped crystals and
that the quickening agents in this setting process are the few small.

REVIEWS 627,

crystals present in the dry plaster. This accords well with all the known
facts in the case and is furthermore in line with Jameson’s observations
on the setting of Portland cements. It explains some of the pecu-
liarities of the behavior of retarders though in the matter of that vexed
subject but little that is new is brought out. If the subject of the
strength, and rapidity of set of the gypsum cements could have been
gone into a little and illustrated by tensile strength and other tests it
would have added greatly to the value of the book and have aided in
defining the sort of situations in which these cements could be used to
best advantage. In the form of hard white finish they now dominate
the market so far as interior work is concerned but the advisability of
using them for wall work in any general way is open as yet to some
question. This is particularly true in view of the strength and cheap-
ness of magnesian limes and the availability of non-sulphate cements.
Dr. Grimsley’s report is a valuable one, particularly in its technical
as distinguished from its geological phases. It will undoubtedly have
a large influence on the gypsum industry of the state and is a credit to
the vigorous Kansas Survey. H. F. Bain.

American Cements. By Urian Cummincs. Pp. 299, 8vo. Rogers
& Manson, Boston. 18098.

In the rapid introduction of Portland cements in this country the
importance and value of the Roman cements bid fair to be overlooked.
At present there is what the author fittingly nominates a ‘‘craze”’ for
quick setting, high testing cements, and the slower setting, cheaper
grades are looked upon in many quarters as of very little value. Mr.
Cummings’ long experience in the manufacture of cement and his wide
interest in the subject admirably fit him to discuss it. In this little
book he has gathered together much scattered information and has
added very much from his own experience. His interpretations of
the chemical processes involved in the making and the setting of
cements will. doubtless arouse much opposition; particularly in his
plea for the magnesian cements, but where so much is uncertain any
hypothesis backed with such facts as Mr. Cummings marshals must
necessarily receive careful attention. Taken as a whole the book is
one of which no one interested in cements and the utilization of our

limestones and shales, can afford to remain in ignorance.
ie BAIN.

RECENT FUBLICATIONS

—Agricultural Journal, published by the Department of Agriculture, Cape of
Good Hope, August 1899.

—Baur. G., and Case, E. C. The History of the Pelycosauria, with a
Description of the Genus Dimetrodon, Cope. Reprinted from the Trans-
actions of the American Philosophical Society, Vol. XX.

— BEECHER, CHARLES EMERSON. The Origin and Significance of Spines.
A Study in Evolution. Am. Jour. Sci., July to October, Vol. VI, 1898.

—Crospy, W. 0. Geology of the Wachusett Dam and Wachusett Aqueduct
Tunnel of the Metropolitan Water Works in the Vicinity of Clinton,
Mass. Reprinted from the Technology Quarterly, Vol. XII, No. 2, June
1899.

Archean-Cambrian Contact near Manitou, Colorado. Bull. Geol. Soc.
Amer., Vol. 10, pp. 141-164, Pls. 14-18. Rochester, March 1899.

— Dana, Epwarp S._ First Appendix to the Sixth Edition of Dana’s System
of Mineralogy. John Wiley & Sons, New York, 1899.

—Day, Davip T. Summary of the Mineral Production of the United States.
in 1898. Extract from the Twentieth Annual Report of the Survey,
1898-9, Part VI. Washington, 1899.

—DeE LORENZO, GUISEPPE. Reliquie di Grandi Laghi Pleistocenici Nell”
Italia Meridionale. Napoli, 1808.

—DumBLE, E. T. Notes on the Geology of Sonora, Mexico. From the
Transactions of the American Institute of Mining Engineers, New York
Meeting, February 1899.

— DryYGALSKI, Dr. ErRIcH. Die Eisbewegung, ihre physikalischen Ursachen.
und ihre geographischen Wirkungen. Abdruck aus Dr. A. Petermanns.
Geogr. Mitteilungen, 1898. Heft III. Berlin, 1899.

—FIsHER, Rev. O. On the Residual Effect of a Former Glacial Epoch
upon Underground Temperature. Philosophical Magazine for July
1899.

—Geological Survey of Georgia. Clays of Georgia. By George E. Ladd,
Ph.D., Assistant State Geologist. Atlanta, 1899.

—Geological Survey of Western Australia. Bulletin No. 3. The Geology
of the Coolgardie Gold Field. By Torrington Blatchford, B.A., F. G. S-.
Assistant Government Geologist. Perth, 1899.

628

RECHL NI POBLICA TIONS. 629

— GREENLY, EDwArD. The Hereford Earthquake of December 17, 1896.
From the Transactions of the Edinburgh Geological Society, Vol VII.

— HawortTHu, ErASmus. Mineral Resources of Kansas for 1898. Annual
Bulletin, University Geological Survey of Kansas. Lawrence, 1899.

— Hopkins, T. C. Feldspars and Kaolins of Southeastern Pennsylvania.
Reprinted from the Journal of the Franklin Institute, July 1899.

— HuBBARD, Lucius L., State Geologist. Keweenaw Point with Particular
Reference to the Felsites and their Associated Rocks. Accompanied by
ten plates and eleven figures. Geological Survey of Michigan, Vol. VI,
Part It,

—Indiana Department of Geology and Natural Resources, Second Annual
Report, 1898; W.S. Blatchley, State Geologist. Indianapolis, 1899.

—lIowa Academy of Sciences, Proceedings for 1898, Vol. VI. Des Moines,
1899.

—Iowa University. Bulletin from the Laboratories of Natural History, Vol.
V, No. 1. Report on the Ophiuroidea Collected by the Bahama Expe-
dition in 1893. By Professor A. E. Verrill. Iowa City, September 1899.

—KAHLENBERG, Louris. Difference of Potential between Metals and Non-
Aqueous Solutions of their Salts. Journal of Physical Chemistry, Vol.
III, No. 6, June 1899.

— KAHLENBERG, Louis and Epwin B. CorpELAND. The Influence of the
Presence of Pure Metals upon Plants. Transactions of the Wisconsin
Academy of Sciences, Arts, and Letters, Vol. XII, pp. 454-474. Madi-
son, 1899.

—LAnG, O. Die Bildung der oolithischen Eisenerze Lothringens. . Sonder-
Abdruck aus “Stahl und Eisen,” 1899. Nr. 14.

Kalizalzlager. Mit. 4 Abbildungen. Berlin, 1899.

De la Formaiion des Cavernes A Propos des Effondrements d’Eisleben.
Bruxelles, 1897.

Ein Beitrag zur Bildungsgeschichte des Harzgebirges. Mit 2 Profil-
skizzen.

—READE T. ME.LuARD, C.E., F.G.S.. The Gypsum Boulder of Great
Crosby. Plates II, III, IV. Foraminiferal Boulder Clay, Riverside,
Seacombe, Cheshire. Reprinted from the Proceedings of the Liverpooi
Geological Society, 1898-9. Liverpool, 1899.

—SARDESON, F. W. Lichenaria Typa W.and S. Am. Jour. Sci., Vol. VIII,
August 1899.

— SMITH, JAMES PERRIN. Larval Stage of Schloenbachia. Reprinted from

the Journal of Morphology, Vol. XVI, No. 1, 1899. The Atheneum
Press, Boston.

630 RECENT PUBLICATIONS

—STANTON, T. W. Mesozoic Fossils of the Yellowstone National Park.
Extract from the “Geology of the Yellowstone National Park,’ Mono-
graph XXXII of the U. S. Geol. Survey, Part II. Washington, 1899.

—United States Geological Survey: Nineteenth Annual Report 1897-8,
Part I, Director’s Report, including Triangulation and Spirit Leveling ;
Part IV, Hydrography; Part VI, Mineral Resources of the United
States, 1897, Metallic Products, Coal and Coke; Monograph XXXI,
Geology of the Aspen Mining District, Colorado, by Josiah Edward
Spurr. Atlas to accompany Monograph XXXI on the Geology of the
Aspen Mining District, Colorado.

Maps and Descriptions of Routes of Exploration in Alaska in 1808,
with General Information Concerning the Territory. (10 maps.) Wash-
ington, 1899.

—WHITEAVES, J. F. The Devonian System in Canada. Vice Presidential
Address, Forty-eighth Annual Meeting of the American Association for
the Advancement of Science, held at Columbus, Ohio, August 21-26,
1899. The Chemical Publishing Company, Easton, Pa.

— WoopwortH, J. B. Some Glacial Wash-Plains of Southern New Eng-

land. From the Bulletin of the Essex Institute, Vol. XXIX, 1897.

THE

FOURNAL OF GEOLOGY

OCTOBER— NOVEMBER, 7S99

Cie erelOCe NM SKULL OP CALIFORNIA AND) KEE
FLINT IMPLEMENTS OF TABLE MOUNTAIN

Tue celebrated skull from Calaveras. county, California,
claimed to have been found at a depth of 130 feet in the aurifer-
ous gravel deposits of a Pliocene river ‘‘beneath the lava, in the
cement, and in close proximity to a completely petrified oak”’
was exhibited by Professor J. D. Whitney at the Chicago meeting
of the American Association for the Advancement of Science in
the month of August 1868.

At that time the attention of the Association in general ses-
sion was directed by the writer to certain conditions and _ pecul-
iarities of the relic which made it unreasonable to accept it as
coming from the deep gravels of a river. The objections then
made to the skull as evidence of man’s great antiquity do not
appear to have been reported or recorded, having been given in
the course of the discussion and not in a paper of record.

One chief reason for the rejection of the skull as coming
from the gravelly bed of an ancient river is the entire absence on
its surface, or on its broken edges, of any marks of attrition.
If the skull had ever been rolled along the bed of a river with
the bowlders and gravel, it would bear the marks of the violent
pounding and wearing action to which any bone or object occur-
ring in such gravels is subjected. In fact, a hollow bone or least
Vol. VU, No. 7, 631

632 WM. P. BLAKE

of all a human skull, could not remain intact, or even so well
preserved a fragment as the skull in question, under such violent
and abrasive conditions—conditions resulting in the rounding
of the edges of pebbles and bowlders and in flattening out pel-
lets of gold.

Those familiar with the auriferous gravel deposits, even of
slight depth in modern rivers, know how the smaller materials
fill every interstice of the bedrock, and, in the case of the bones
of the mammoth and of the mastodon, how the foramens of the
teeth and any cavity of the more solid bones of the jaw become
filled up solidly with fine gravel, often cemented, and sometimes
holding pellets of gold. Bones found in river gravels show the
effects of attrition and wearing. All the thin plates, asperities,
and sharp edges disappear under the violence to which they are
subjected in running water transporting gravel.

In the Calaveras skull no such conditions are found. It was
found hollow, nearly empty as left by the decomposed brain, not
filled with gravel or sand, of a river deposit, and the broken
edges were sharp and not abraded. This condition alone is suf-
ficient evidence that the skull and the gravel in which it was said
to occur were not parts of the same deposit and contemporane-
ous in origin in the river bed.

But certain objects were found in the skull—other bones, an
ornament of some kind, and the shell of a snail, partially cemented
together and to the skull by a deposit of calcareous tufa. All
these objects indicate surface origin and interment, and their
presence is not reconcilable with any theory of the entombment
of the skull in auriferous, deep-seated gravel.

Since the exhibition of the skull at Chicago a full description
of it, illustrated by a full-sized drawing, has been published by
Professor Whitney." By reference to this drawing it will be
seen that all the fractured edges of the bones (for it is not an
entire skull) are sharp and angular, and do not show signs of
abrasion.

tContributions to American Geology, Vol. I. The Auriferous Gravels of the
Sierra Nevada, California, by J. D. Whitney, gto, Cambridge [U. S.], 1880.

THE EEIOCENESSICOLE (OF CALIFORNIA 633

The presence of calcareous tufa is adverse to the theory of
the occurrence of the bonevin the deep gravel. The tuia is an
incrustation ; its presence indicates surface evaporation and con-
centration of calcareous waters. It does not occur in this case
as a permeating solution forming a cement for deep gravel, but
as an investing crust deposited on and around the bone, although
it is claimed that a chemical change in the bone has resulted.
The cementing material of the deep gravels is generally siliceous
rather than calcareous, or if calcareous it permeates the mass
and unites the pebbles and grains of sand into a rock-like mass.

The description states: ‘‘In cutting away the mixed tufa
and gravel which covered the face and base, several fragments of
human bones were removed, namely, one whole and one broken
metatarsal; the lower end of a left fibula and fragment of an
ulna as well as a piece of a sternum.” ‘These bones and frag-
ments of bones might have belonged to the same individual to
whom the skull had appertained, but besides these there was a
portion of a human tibia of too small size to be referred to the
same person.’ There were also fragments of the bones of a
small mammal. Under the molar bone of the left side, a small
snail shell was lodged, partially concealed by one of the small
human bones which was wedged into the cavity. This shell was
recognized by Dr. J. G. Cooper as Helix mormonum, a species
now existing in the Sierra Nevada. Cemented to the fore part
of the roof of the mouth was found a circular piece of shell
four tenths of an inch in diameter, with a hole drilled through
the center which had probably served as an ornament. Several
very small pieces of charcoal were also found in the matter
adhering to the base of the skull.’’?

I have given this full quotation that there may not be any
mistake. Professor Whitney is certainly to be commended for
his complete presentation of evidence which is sufficient, in my
judgment, to show that he was dealing with the relics of an
Indian burial place rather than a fossil from the ancient gravels.
It is not possible to conceive that this mixture of human bones

* [bid., p. 268.

634 WM. P. BLAKE

of portions of at least two individuals, an ornament, charcoal,
and a snail of an existing species, or of any species—a thin
fragile shell—could travel together in the bed of a river and be
concentrated in one spot, in fact, in one mass. It is incredible.

Much stress in the discussion upon the authenticity of this
relic is placed upon the statement of the miner that he found
the skull in his mine; that he found it there lying on the side of
the channel with a mass of driftwood. While this statement of
finding bones and driftwood together at that depth tends to dis-
credit the statement it may be accepted, but with the question,
how did the skull get there? The best explanation is found in
the statement of another miner who had a claim in the vicinity
that in going home one evening he picked up the mass, and, in
passing his neighbor’s shaft, threw it down to frighten him, and
get him to go home to supper. The skull was then ‘“‘ discovered”
and taken to Angel’s Camp, where, after resting for a time in the
window of the apothecary, it attracted the attention of Dr. Jones,
of Murphy’s camp, and was made known to the scientific world.

This is the story as told to me by eyewitnesses and partici-
pants. Thus the silent but convincing testimony of the skull
itself, and of human testimony, are against its reception as evi-
dence of man’s antiquity.

But while the authenticity of this skull as a Pliocene fossil
is questioned and challenged by most authorities, it is often
accorded a quasi-recognition rather than an unqualified rejection.
For example Professor G., Frederick Wright relying partly upon
new evidence presented by Mr. Becker at the meeting of the
Geological Society of America in 1891 appears to be convinced
of the genuineness of the skull and states “‘it would seem unreas-
onable any longer to refuse to credit the testimony.’’*

The most satisfactory and common-sense discussion of the
merit of this skull as evidence with which I am acquainted is
that by Principal Dawson in his work enitled Fossil Men.? After

* WRIGHT, “Man and the Glacial Period, p. 296.

?Fossil Men and their Modern Representatives, by J. W. Dawson, LL.D.,
F.R.S., F.G.S., Montreal, 1880, pp. 344-347.

LHE PLIOCENE SKULL OF CALIFORNIA 635

giving five cogent reasons for the non-acceptance of the Cala-
veras skull as evidence of the existence of man in Pliocene times
he sums up as follows: ‘‘The above reasons are, I think, quite
sufficient to warrant any geologist in declining to accept the
human remains of the California gravels as other than those of
American Indians of modern periods.”

Quatrefages makes two references to the Calaveras skull.
In one he writes: ‘‘Much has been said about the skull discov-
ered by Whitney in California. Unfortunately, the description
of this specimen has not appeared so that doubts have on sev-
eral occasions been expressed as to the existence of the fossil
itself. The recent testimony of M. Pinart has removed them,
but has at the same time created the most serious doubts as to
the antiquity of this specimen, which seems to have been found
in disturbed grounds.”’*

Again, in discussing the succession of the two great types of
skulls, he states ‘that at present everything argues in favor of
the anteriority of the dolichocephali. In America the only
known fossil skull leads to the same conclusion.” ?

In the foregoing citation of the conclusions of Dr. Dawson
it will be noted that he groups together the evidence presented
by the skull and those from other human remains in the Cali-
fornia gravels. This tendency is shown, also, by Dana, who,
after mentioning the doubts of the authenticity of the skull,
writes: ‘‘ Whitney also mentions the discovery of flint implements
in the auriferous gravel in other parts of California. The fossil
plants of the gravels are referred to the Pliocene (or partly
Miocene) by Lesquereux. The few mammalian remains include
the Champlain mastodon and elephant, but in some places
Pliocene species. Some recent land shells were contained in
the earth filling the cranium.”

To anyone not familiar with the localities, the modern and
ancient gravels, and the occurrence of flint implements, the

*A. DE QUATREFAGES, The Human Species. Int. Sci. Series, D. Appleton &
Co., 1888, p. 291.

? Ibid., p. 299.

636 WM, P. BLAKE

conclusion would, I think, be a fair one that both the mammalian
remains and flint implements occur in the same gravels, or horizon,
in which the skull is claimed to have been found. So far as my
knowledge extends this is not so. J am not aware that it has
been claimed that flint implements, or even the remains of the
mammoth and the mastodon have been found where the skull
was said to occur. That flint implements have been found in
association with the remains of the large mammals there is little
doubt, but as to the age of such gravels, and whether or not the
implements may not have been washed in from higher levels or
superficial deposits of a far later origin I am not able to bear
conclusive testimony. The subject requires most careful and
extended investigation, the fact being always kept in mind that
in the gigantic placer mining operations of California there is a
concentration upon the bedrock of all heavy objects which may
have been originally in the surface soil or any part of the banks
of gravel between the soil and the bed of the ancient river.

In all river and creek channels of modern streams, and even
in what are called dry arroyos or gulches, there is a possibility that
in seasons of flood or of great accumulation of rushing water
from showers or cloud-bursts objects lying on the surface, such
as stone implements, pestles, mortars, metates, flint chips, etc.,
may be swept onwards in the gravel and sunk to the very bed-
rock and become buried by deposits twenty feet thick, and pos-
sibly more and all in the space of an hour or less. The loss of
iron safes in different places in California and Arizona, the safes
wholly disappearing, and similarly the loss of quicksilver in
flasks while crossing a swollen torrent are familiar examples.
Heavy objects, like gold, in swiftly moving water are carried to
the lowest point possible and are covered from view by heavy
deposits of gravel and bowlders. The finding, therefore, of
Indian stone mortars at a considerable depth in gravel in a
modern stream valley is not good evidence of antiquity.

In regard to the concentration of objects on the bedrock of
placers, when there is sluicing or washing by the hydraulic
method on a large scale, miners are familiar with the fact that

THE PLIOCENE SKULL OF CALTFORINTA 637

nails, spikes, shot and bullets are frequently found in cleaning
up the sluices. In one instance, known to the writer, a small
cast-iron casket containing the remains of an infant in alcohol
was found in cleaning up a sluice after a long run by the hydraulic
process upon a bank of gravel some thirty feet deep.

THE TABLE MOUNTAIN RELICS

Much has been written regarding the flint implements in great
variety and perfection of workmanship collected from Table
Mountain near Angels Camp by the late Dr. Snell. It was
stated by him that they were found under Table Mountain, the
lava cap of an old Pliocene river. I must confess to have for a
time lent credence to this view of their occurrence. I reported
the facts as I then understood them at the Congress of Arche-
ologists at Paris in 1867.

But later investigations have satisfied me that these relics
"were entombed in the surface soil and accumulations of the slope
of the mountain just below the jutting, overhanging cliffs of the
lava, which afforded excellent protection from the weather, and
were no doubt occupied as habitations or dwellings analogous to
the cliff-dwellings of New Mexico and Arizona, but without any,
now visible, exterior wall or construction. There is no reason
for associating these flint implements in any way with the occur-
rence of the skull, or with the bones of the great mammals.

Wy. P. BLAKE.

UNIVERSITY OF ARIZONA,
March 1899.

A GRANITE-GNEISS IN CENTRAL CONNECTICUT

THE granite-gneiss* to be described occurs on both sides of
the Connecticut River, some five miles east of Middletown. It
cuts the schists of the eastern crystalline area of Connecticut, a
short distance east of their contact with the Triassic sandstone.
Its distribution is shown on the accompanying map (Fig.1).? It
forms an oval area inthe mica schist, and, at its northern end,
is continued northward by a series of beds varying from a few
inches to many feet in thickness, lying parallel to the enclosing
schists. The largest of these is a direct continuation of the
main granite-gneiss mass, and all are probably parts of the same
intrusion. As the distance from the main area increases, these
beds gradually thin out and disappear from the schists.

The only previous work on the geology of this region is that
of Percival,3 who recognized this granitic rock only on the east
side of the river, and united that part of it with a large mass of
granitic-gneiss to the north, with which it is probably not con-
nected. He does not consider the origin of any of the gneisses.
It ‘has not been possibie to use Percival’s results except in a
general way, and the work done in this region by the writer is
essentially de novo.

The rock is a medium to fine-grained biotite-gneiss. The
color varies from white or light gray to dark gray, according to
the amount of biotite. In a few cases the rock is almost or
quite massive, but usually it is well foliated. The granite-gneiss
is cut by several sets of joint planes, of which one set is nearly

"In this paper a gneiss of granitic composition and of unknown origin is called
a granitic gneiss; if of igneous origin, a granitic gneiss. See C. H. GorDON in Bull.
Geol. Soc. America, Vol. VII, p. 122.

2 That portion of the western boundary of the granite-gneiss north of the river is
largely covered by river terrace, and for about a mile along the eastern border, near
Great Hill pond, outcrops are rare. With these two possible exceptions, the “sup-
posed boundary,” so-called, is believed to be very nearly the true boundary.

3J.G. PeRcIVAL: Report on the Geology of Connecticut. 1842, pp. 222, 224.

638

GRA NITE-GNEISS IN CONNECTICUT 639

LECEND,

Localities teferred tf in text are numbered
= “Qugen’- gneiss. Yo Quarries
iY Granulite \ Diptand strike
SU we Near or @xacl boundary
\ ye Upposed boundary,

ny
One Mile,

ae
seh AIR UNE RY
{

t)
/ So H
pas N
(Sag SO Ficor ;
Sy Riv & ’
SSS R r)
Ep U
on)
ae
Pia es
oy =f x
fe 3 a
8: a
“
®

2 ie

‘ =
* TX Benvenve Qu. wi
x
iz ;
ty

J

Fic. 1. Map of the Granite-Gneiss Area.

r

640 LEWIS G. WESTGAWE

or quite parallel to the foliation, giving the rock a bedded
appearance (Fig. 2. Map,1). Several quarries have been opened,
and the attempt has been made to market the rock as a building
stone. It is handsome when first quarried, but stains quickly,
and so is of use only for foundations, etc.

Fic. 2. Bedded Granite-Gneiss, Maromas Quarry.

I. THE GRANITE-GNEISS IS ERUPTIVE.

1. General stratigraphical features—A rounded or elliptical
form, like that taken by this granite-gneiss, is common in the
case of eruptive granites. The narrow belt that runs into the
schists from its northern end is decidedly subordinate to the
larger mass of which it is an offshoot. Thenorthwest direction
of the longer axis of the granite-gneiss area is doubtless deter-
mined by the strike of the enciosing schists. The irregularity
of the boundary on the west side of the granite-gneiss indicates

GRANITE-GNEISS IN CONNECTICOT 641

the same origin as does the general form of the area..° At
several points, too, along the western border and southern end
of the granite-gneiss (Map, 2), the line of contact cuts across
the strike of the foliation of the enclosing schists. This is not
noticeable at all of the localities at which actual contacts between
the two rocks can be seen, though it is at one or ‘two, but it
comes out on mapping the dip and strike of the schist. This
foliation of the schists seems to be a stratification foliation and
not a secondary structure, because (1) it is parallel to the alter-
nating beds of schist and fine-grained micaceous gneiss which
make up the schist formation, and (2) the dip and strike of the
foliation is not uniform throughout the area, but varies through
all possible changes.

2. Contact Phenomena.— At some of the localities where the
exact contact of the two rocks is seen there is the clearest proof
within narrower compass of the eruptive character of the granite-
gneiss (Map, 3). The line of contact is frequently irregular, the
granite-gneiss often cuts across the foliation ot the schist or
sends tongues into the schist; and sheets of schist, partly torn
from the main schist mass, occur projecting into the granite-gneiss.

As the granite-gneiss occurs in the midst of completely crys-
talline schists, any considerable contact metamorphism of the
surrounding rocks would not be expected. In many granite
intrusions into crystalline rocks no contact metamorphism is
seen. In the present case besides quartz, feldspar, biotite and
occasionally hornblende, the schists carry at times garnet,
staurolite, cyanite and tourmaline. The latter often seems to be
connected with the pegmatite dikes which cut the schist. None
of these less common minerals is more abundant near the con-
tact or can be considered a result of the metamorphic action of
the granite-gneiss.

It is sufficient merely to mention at this point another evi-
dence of the igneous character of the granite-gneiss, namely, the
fine-grained granulitic character which it assumes at some points
about its border. This endomorphic metamorphism of the
granite-gneiss will be described more fully below.

642 LEWIS G. WESTGATE

3. Inclusions.— One of the most striking proofs of the eruptive
character of the granite-gneiss is the presence of inclusions of
schist within its boundary. These are seen at a number of
localities in widely different parts of the area, and commonly
not far from the border (Map, 4). They vary in size from a few
inches to many feet in length, and may be of linear or very
irregular form. The material composing them is a biotite-schist,
or a fine-grained biotite-gneiss, similar to the schist series around
the gneiss and often showing the minute folding which in places
is characteristic of the latter. The inclusions occur both in the
more massive and in the more foliated varieties of the granite-
gneiss, and also in the granulitic facies which occurs at some
points about the border.

At this point it is well to describe an occurrence which,
while not a proof of the igneous origin of the granite-gneiss,
is best understood in connection with inclusions. At several
localities in the southern half of the granite area, occur isolated
bands of schist of uniform thickness, running parallel to the
foliation of the immediately adjacent granite-gneiss. They
cease at a greater or less distance, but their actual termination
cannot be seen because of lack of outcrops. They show sharp
contacts with the enclosing granite-gneiss and in one or two
cases tongues of the latter enter them at a low angle,
showing them to be inclusions. And as even those schist bands
which do not show an apparent eruptive contact lie within an
area of rock which is certainly in largest part eruptive, it is most
likely that all such occurrences are inclusions. - These band-like
inclusions vary from a few feet to several score of feet in thick-
ness, and are sometimes several hundred feet in length. Their
direction is variable and is independent of the foliation of the
schist lying nearest to them outside of the granite-gneiss area.
Their sheet-like character was evidently determined by the
strong foliation of the schists through which the granite-gneiss is
here eruptive. It is, however, along the east side of the granite-
gneiss that the amount of this foreign material is greatest.
Here the mica-schist is associated with considerable dark,

GRANITE -GNEISS IN CONNECTICOT 643

thin-bedded gneiss and schist which contain both biotite and horn-
blende, and with amphibolite. These dark bands of gneiss and
schist are not here variable in direction, but run parallel to the
boundary of the granite-gneiss, and agree in dip and strike with
the schist east of itand with themselves. Yet undoubted igneous
contacts occur between these dark gneisses and schists, and the
lighter granite-gneiss which occurs between them. The granite-
gneiss which in other parts of the area replaced almost entirely
the schist through which it came, here merely forced its way
into fissures parallel to the foliation of the country rock. The
distribution of this belt of mixed rock is shown on the map.
As already pointed out the granite-gneiss gradually disappears
as we go north.

4. Schheren.—-\n a number of places where the granite-gneiss
is most massive, it encloses patches of darker material or
schlieren—basic segregations of the granitemagma. These are
best seen in the Benvenue and Maromas quarries. The schlieren
are of uniform composition, finer grained than the enclosing rock,
have a larger proportion of biotite, and often contain hornblende,
which is almost wholly wanting in the ordinary granite-gneiss.
They are rounded, elliptical or irregular in outline and always
elongated parallel to the foliation so as to form lenticular patches
and in extreme cases bands. This lenticular and frequently
sheet-like form is probably due to movement in the partly
differentiated magma previous to thes olidification of the rock.
Such darker and more basic portions are very common in gran-
ites and have been regarded as a strong indication of the eruptive
origin of the rock in'which they are found. In the Benvenue
quarry where these schlieren occur,:the rock also holds irregular
inclusions of schist.

Associated Pegmatite Dikes—Although the presence of abun-
dant pegmatite dikes~about a granitic area would not in itself
be a proof that the rock in question was eruptive, it would
be an interesting and corroborative fact. In the opinion of

* ROSENBUSCH : Massige Gesteine, p.62; G. H. WILLIAMS, XV., Ann. Rept. U.S.
Geol. Surv., p. 662.

644 LEWIS G. WESTGATE

Brégger,’ Williams,? Crosby,3 and others, the presence of one or
more parent masses of less acid plutonic rocks is to be expected in
such regions of abundant pegmatite dikes. The pegmatite dikes
of central Connecticut are abundant, and are widely known for
the variety and beauty of the minerals they have furnished col-
lectors. They occur in dike-like masses in both gneisses and
schists, but more abundantly in the latter, and they both cross
and run parallel to the foliation of the enclosing rocks. Their
contact with the gneisses and schists is sharp and they frequently
contain inclusions of the same. There are two other considera-
ble areas of granitic biotite-gneiss in the region, one to the south
and the other to the north of the area under consideration. The
former shows no sign of igneous origin and seems to be the basal
member of a series of conformable gneisses and schists which
form a northward pitching anticline. The study of the latter
area is not yet completed. The evidence so far collected seems
to indicate that it is largely composed of eruptive material; but
even so the Middletown granite-gneiss ‘s more centrally located
with reference to the dikes and would more likely be the rock
genetically connected with them. The schists which surround
it are more filled with pegmatite. The hills near the Connecticut
River, just west of the granite-gneiss, are known as the ‘“‘ White
Rocks,” from the prominent outcrops of pegmatite, and the
schist east of the granite-gneiss is also cut by quantities of the
same rock. This abundance of pegmatite dikes would lead us
to expect one or more centrally located masses of granite with
which they could be connected, and the area of granite-gneiss
we have been describing seems to answer the expectation It
does not appear that the dikes radiate from it; rather they
follow in a general way the foliation of the schist. They do,
however, appear to grow more abundant toward the granite-gneiss.

In connection with the evidence brought forward to show the
eruptive nature of the granite-gneiss it is interesting to know

* Zeit. fiir Kryst., Vol. XIV, 1890, or Canadian Rec. Sci., Vol, VI, p. 33.

2 Fifteenth Ann. Rept. U. S. Geol. Surv., p. 680.
3CRosBy and FULLER, American Geologist, Vol. XIX, p. 151.

GRANITE-GNEISS IN CONNECTICUT 645

that the granitic biotite-gneiss to the south, which has already
been mentioned as constituting the lowest member of an
anticlinal fold, and which appears from its field relations to be
a sedimentary rock, wholly lacks the various characteristics of
igneous origin possessed by the granite-gneiss. The miner-
alogical and structural characters which come out in a micro-
scopical study of the rock, and which will be described below,
are also in harmony with the belief that the granite-gneiss, in
spite of its general and pronounced foliation, is an igneous rock.

II. PETROGRAPHY OF THE GRANITE-GNEISS

1. Lhe ordinary type-—TVhe ordinary form of the granite-
gneiss is a light-colored, rather fine-grained biotite-gneiss. The
amount of biotite varies considerably. Where it is most abun-
dant, the rock is a dark-gray, well-foliated gneiss ; where least
abundant, the rock is light-gray and of a quite granitic appear-
ance. In no case does it become perfectly massive. The grain
of the rock allows of its being split along the foliation into curb-
stones, but not, as in the case of some of the other gneisses of
the region, into flagstones. In the main body of the granite-
gneiss the strike of the foliation is approximately N. 45° W.;
the dip, 30° N. E. Joint planes cut the granite-gneiss in sev-
eral directions, one nearly or quite parallel to the foliation, others
at right angles. The rock is handsome when first quarried, but
has proved useless as a building stone, because it rusts on
exposure.

Microscopically the rock is a granitic mixture of feldspars
and quartz, in which lie small plates of biotite. The biotite is
abundant, generally with a pronounced parallel arrangement, to
which the foliation of the rock is due. Hornblende is almost
wholly absent. Ina single section green hornblende occurs in
amount subordinate to the biotite and it can be seen in a very
few exposures in the field. The feldspars usually present an
allotriomorphic, granitic aggregate of grains. Orthoclase is most
abundant. An acid plagioclase is of common _ occurrence.
Microcline also occurs in smaller and more irregular grains.

646 LEWIS G. WESTGATE

Both orthoclase and microcline frequently show a fine microper-
thitic intergrowth, with a second feldspar. In a larger number
of sections some orthoclase and plagioclase grains show a grano-
phyric intergrowth, with a second mineral, probably quartz,
which takes the form of narrow irregular, curving or angular
inclusions, converging toward the center of the feldspar grain.
This granophyric intergrowth is absent from the probably sedi-
mentary gneisses to the south, and seems to be characteristic of
those of igneous origin. Quartz occurs in irregular but some-
what rounded interstitial grains, and is also common in drop-
like inclusions in the feldspars, which occasionally approach a
a dihexahedral shape. Titanite, in small, rounded, and lenticu-
lar grains, is the most common accessory. A very little apatite
and magnetite occur. In about one half of the sections there is
evidence of a slight amount of crushing. In the section where
this is best shown, some of the quartz grains have been elon-
gated, broken into separate areas, and granulated about their
border and along lines of fracture; and between the feldspar
grains are lines of smaller grains, which seem to have come from
the fracturing of the feldspar, Yet in this section considerable
portions show no evidence of crushing, and in many slides no
proof of crushing exists.

2. Schlieren.— The biotite-gneiss, especially where it is more
massive, often contains schlieren of darker color and finer grain,
which have already been referred to and partly described in the
discussion of the igneous origin of the granite-gneiss. Sections
from these schlieren resemble closely the ordinary granite-
gneiss. They are granitic in structure, but with a distinct folia-
tion. Green hornblende is present, but is less abundant than
the biotite. Orthoclase, plagioclase, and microcline occur in
abundance in the order named. A few feldspar grains show the
granophyric intergrowth already mentioned. Quartz and micro-
perthite are absent. Titanite is acommon accessory. The pres-
ence of hornblende and absence of quartz, while keeping the
other essential structure and characters of the granite-gneiss,
indicates that these darker patches are an integral part of the

GRANTTE GENISS [N CONNECTICUT 647

granite-gneiss, only somewhat more basic than the general rock.
The absence of any evidence of crushing in the sections shows
that their present lenticular and banded form was attained while
the rock was still unsolidified.

3. Lhe ‘‘augen’’-gneiss— Frequently the granite-gneiss be-
comes a decided ‘‘augen’”’-gneiss. Its distribution is indicated
as nearly as possible on the map. It attains its best develop-
ment along the northeastern border of the granite-gneiss and
in the narrow tongue that runs north into the schist. The
‘“‘augen’’-gneiss often passes gradually into the ordinary granite-
gneiss, with which it is identical in mineralogical composition
and in structure, with the single exception of the occurrence of
sub-porphyritic feldspar crystals and aggregates. A surface
broken at right angles to the foliation shows a light gray gneiss,
dotted with more or less distinct ‘‘augen” of white or pink feld-
spar, averaging three fourths of an inch in length, and with a
parallel arrangement, around and between which run the lines of
biotite flakes. The feldspar of the ‘‘augen” often reflects light
as a single crystal, either simple or a Carlsbad twin, and rarely
this crystal is roughly rectangular, yet it never possesses crystal
boundaries. Quite commonly the cleavage surface of these
broken crystals shows dull rounded areas of feldspar which are
differently oriented grains included within the larger crystal.
Where a single crystal occurs it forms the irregularly margined
core of the “‘auge”’ and is surrounded by a dull white rim com-
posed of an aggregate of fine feldspar grains. As the core is
pink and the rim white, there is a further contrast between
the two. Much more often than not, however, the reddish core
does not reflect as a unit, but consists of an aggregate of grains,
still flesh-colored and coarser than the rim. In other cases the
‘‘augen”’ consist of aggregates of white feldspars without any
reddish cores.

It looks very much in the hand specimen as if those reddish
cores of the ‘“‘augen,” which are composed of an aggregate of
grains, were derived from the fracturing of single grains, which
in some cases seem to remain partly intact at the center. But

648 LEWIS G. WESTGA TE

where such an aggregate is examined microscopically it is
seen to be composed of feldspars of different species which
show no evidence of crushing. One section (Fig. 3) showed
such an aggregate consisting of a very irregular Carlsbad twin of
orthoclase at its center, partly or completely enclosing irregular
grains of orthoclase, plagioclase, and microcline, all containing
small rounded grains of quartz. There was no evidence of
crushing; no evidence of derivation of the smaller grains from

Fic. 3.— An “auge” of the “augen”’-gneiss (X 18). The dark area on the
upper right side is beyond the border of the section. Opposite, below, is the border
of clear feldspar grains with a little biotite. :
the central orthoclase grain. About this central aggregate was
a zone of clearer feldspars. The red cores, then, of the ‘‘augen,”’
both single grains and aggregates, are original crystallizations.
The case may be somewhat different with the white rims which
in many cases surround the red cores. These do show some
evidence of crushing, and may be in part derived from periph-
eral crushing of the red cores, possibly accompanied by some
recrystallization, for the feldspars here have a fresher appearance

GRANITE-GNEISS IN CONNECTICUT 649

than those in the central part of the ‘‘augen.” Yet the absence
of evidence of extensive crushing, and the fact that many of the
“augen’’ consist wholly of white aggregates of feldspar which
under the microscope show no evidence of crushing, lead us to
suspect that even these white aggregates, which sometimes
occur as borders around the red cores and sometimes constitute
‘‘augen’”’ by themselves, may be, in large part, original crystalli-
zations. The fact that these ‘“‘augen” do not include to any
extent plates of biotite, but that the lines of biotite flakes curve
around them, seems to point to the formation of the ‘‘augen’’
previous to the complete solidification of the rock. The ‘‘augen’’-
gneiss, like the granite-gneiss of which it is a local variation, is
of igneous origin. If we suppose that the first step in its forma-
tion was the separation of small orthoclase individuals or aggre-
gates of feldspar, mainly orthoclase, but containing plagioclase
and microcline, which received their parallel arrangement before
the final solidification of the rock, and which may have been
subsequently somewhat reduced by crushing, we shall have the
most probable explanation of the ‘‘augen’’-gneiss phase of this
granite-gneiss,

The foliation of the granite-gneiss does not seem to be in
the main a dynamic result. Evidence of crushing is found in
many sections in the form of wavy extinction of the quartz and
lines of finer material between the larger quartz and feldspar
grains, and crushing may be responsible in part for the parallel
structure of the rock. Yet in many sections of the well-foliated
gneiss the microscope shows no evidence of crushing at all. It
seems more likely that the arrangement in a common plane of
the biotite and, in the ‘““‘augen’’-gneiss, of the often rather tab-
ular grains of orthoclase is a result of movement in the partly
solidified magma. The character of the schlieren points to the
same conclusion. In ordinary granites the schlieren are not
stretched, but are roughly equidimensional, and such we may
suppose their original form to have been in the present case.
Had they been drawn out to their present distorted condition
subsequent to the solidification of the rock, they could hardly

650 LEWIS G. WESTGATE

fail to show evidence of such a movement in the distortion and
crushing of their individual mineral particles, but such is not
the case. Anda rock subjected, while still incompletely solidi-
fied, to such an extensive movement as is indicated in the present
instance by the form of the schlieren, would naturally have the
elements which had already crystallized out, in this case biotite
and, locally, individual grains and aggregates of feldspar,
arranged in a more or less parallel manner.

4. Granulite.—For a mile along its western border, and fora
somewhat greater distance about its southern end, the granite-
gneiss shows a granulitic facies towards the contact. At other
points both the ‘‘augen’’-gneiss and the ordinary granite-gneiss
may occur unchanged in immediate contact with the schist.
The width of this granulite border is not constant ; it varies from
two or three feet to many yards. Where typically developed, it
is a fine-grained, light gray or brownish rock, sometimes pure
white and lacking all traces of dark minerals. This pure
white granulite is present only at a few places and imme-
diately at the contact. Small garnets are usually present.
The rock has asugary texture, and when somewhat weath-
ered often crumbles under the pressure of the fingers. Micro-
scopically it is a fine-grained aggregate of orthoclase, an
acid plagioclase, microclineand quartz. The structure is the
so-called granulitic of M. Levy' and the panidiomorphic of
Rosenbusch.?

The quartz and feldspar form an aggregate of variously
oriented rounded grains of uniform size, which are not, however,
bounded by crystal planes. With the scarcity of biotite, the
foliation becomes indistinct or wanting. In one case garnet
grains form fine lines on the broken edge of the rock. No evi-
dence of crushing exists.

*M Lévy: Classification des Roches Eruptives, Pp. 30.

? ROSENBUSCH: Massige Gesteine, p. 461. In this connection see TURNER:
Geology of the Sierra Nevada, Sixteenth Ann. Report U.S. Geol. Surv., Pt. I, p. 737.
Granulite (M. Lévy) is synonymous with aplite (Rosenbusch). Rosenbusch regards

aplites as typically dike rocks, yet recognizes their occurrence as acid border phases of
granite intrusions. /ézd., p. 65.

GRANITE ~GNETSS IN CONNECTICUT 651

At several localities the granulite can be followed from the
contact and can be seen to pass gradually into the ordinary
granite-gneiss. The changes on passing from the contact are as
follows: (1) The rock becomes coarser, loses its granulitic
structure and assumes a granitic structure. (2) The garnet dis-
appears, biotite becomes abundant and is accompanied by the
ordinary accessories of the granite-gneiss, titanite, magnetite and
apatite. (3) Small grains of granophyre and microperthite

Fic. 4. Granulite (X18).

appear. These are common among the feldspars of the granite,
but are wholly lacking in the granulite. Of these characters the
granulitic structure and the presence of garnet extend farthest
from the contact and often at a distance of many yards the
richly biotitic granite-gneiss becomes garnetiferous and shows a
decidedly saccharoidal texture.

Bands of granulite occur interbedded with or cutting across
the schists near the contact. These bands are often less than an
inch in thickness, and may connect with the main mass of the

652 LEWIS G. WESTGATE

granulite. A few of the smaller bands contain much muscovite
and are well foliated. The granite-gneiss sometimes assumes a
granulitic facies about inclusions. A good example of this
occurs at one end of the Benvenue quarry, west of theriver. A
fifteen-foot mass of schist is caught in the granite-gneiss, which
is dark gray and thick-bedded, but at the contact with the schist-
inclusion changes to a fine-grained, white granulite with minute
scattered flakes of biotite.

The eruptive nature of the granulite is clear. It cuts across
the bedding of the surrounding schists ; it sends apophyses into
them; it holds inclusions of them. That it forms one geological
body with the granite-gneiss is shown by its gradual passage into
the latter at several points. It is not a crushed granite, as its
position about the border of the granite and the absence of
any microscopical evidence of crushing would show. It is an
example of original endomorphic contact-metamorphism of the
granite-gneiss,_more acidic and finer grained than the main
body of the rock. The fineness of grain and the granulitic
structure may be due to more rapid cooling of the magma in the
neighborhood of the contact, though there is no reason why the
conditions and consequently the structure of the granite-gneiss
should be different at these points from what they were about
the whole border of the granite. The more acidic character of
the rock at the contact has not been satisfactorily explained.
Similar phenomena have been observed elsewhere,’ notably about
some of the granite intrusions of France.

Besides the contact granulite described above, granulite
occurs in three distinct forms. It occurs (1) as bands, generally
not over a foot in thickness, cutting the granite-gneiss in or
across the foliation and often becoming coarser and somewhat
pegmatitic. In many cases these bands appear to grade some-
what abruptly into the surrounding rock. They are in a sense
later than the granite wall-rock and may mark a closing stage
of igneous activity, before the granite had fully hardened. it

‘ROSENBUSCH, Massige Gesteine, p. 65. References to articles by BARROIS on
several of these granites are given on p. 14.

GRANITE-GENISS IN CONNECTICUT 653

occurs (2) as a white, fine-grained granulitic portion of some of
the pegmatites. (3) One or several dikes of gray granulite cut
the dark gneisses which occur associated with the granite-gneiss
along its northern border (Map, 5). Their position is shown on
the map. Each of these varieties has its own peculiarities and
all differ from the contact granulite. They are probably all
later than this last and are merely mentioned here for the sake
of completeness.

5. Darker and more foliated granite-gneiss—Along the north-
eastern side of the granite-gneiss area is a belt which has already
been noticed, in which the granite-gneiss alternates with schists
and with dark, more or less hornblendic gneisses and amphib-
olites. This area is indicated on the map. Associated here
with the granite-gneiss and with these other rocks is a third
type, in a way intermediate, yet more closely related to the
granite-gneiss. These last rocks are darker and more foliated
than the granite-gneiss. They are frequently marked by lentic-
ular-linear white patches, up to a third of an inch in thickness,
composed of an aggregate of feldspar grains. From this char-
acter they may be named “‘spotted-gneiss.”” They agree micro-
scopically in structure and in mineral composition with the
granite-gneiss. There are only two differences: (1) anincrease
in the amount of biotite and, asa consequence, a better developed
foliation, and (2) the presence in some cases of hornblende.
Sometimes they show microscopical evidence of crushing. They
form eruptive contacts with the schists which are cut by the
granite-gneiss.

The relations of the spotted-gneiss and the amphibolites are
not wholly clear, and these relations are probably different in
different cases. The two rocks are distinct petrographically.
The contact between the two is an eruptive contact. If the
amphibolites are older——-and their stronger banding and folia-
tion might well suggest as much—it matters not to the under-
standing of the granite-gneiss whether they are of igneous or
sedimentary origin; they are in either case earlier rocks cut by
the granite-gneiss. But in many cases they are probably later.

654 LEWIS"G. WESTIGATE,

For eruptive amphibolites occur abundantly in the schist and
presumably sedimentary gneisses outside the granite-gneiss area,
and at one point within the granite-gneiss (Map, 6) banded
amphibolites occur grading into massive hornblende-gabbro, and
this basic rock becomes finer grained toward the contact where
it cuts across the foliation of the granite-gneiss. Some of these
amphibolites, then, are certainly younger than the granite-gneiss
and cut it. Some may be older than the granite-gneiss.

The relation of the spotted-gneiss to the more ordinary
granite-gneiss is not altogether clear. In some cases parallel
bands of the two le in sharp contrast. Again within limited
areas a complete series of intermediate rock types occur. The
spotted-gneiss seems to be a somewhat more basic rock derived
from the same magma as the granite-gneiss. In part, however,
it looks as if the two were not strictly contemporaneous. The
spotted-gneiss may have been intruded into the granite-gneiss,
or vice versa, although both find their origin in the same molten
body and were the products of a single igneous intrusion.

Lewis G. WESTGATE.

SOME NOTES -ON THE LAKES AND: VALLEYS "OR
THE UPPER. "NUGSUAK PENINSULA; “NORTH
GREENLAND"

INTRODUCTORY STATEMENT

Tue Upper Nugsuak peninsula is located in north latitude
74° 5’—-15'; is 25 to 30 miles long, averaging from four to
six miles in width, and has a due southwest trend with the general
coast line of Greenland. This part of the coast is characteristi-
cally rough and rugged. The marginal strip —at present ice-
free — is intersected by numerous fjords, which, in many cases,
penetrate to the very edge of the ice-cap, cutting the uncovered
land into numerous islands and peninsulas. A considerable part
of the uncovered lands is occupied by lakes.

The peninsula is limited on its north and south sides, by fjords
descending to depths of not less than 300 to 500 fathoms, and
varies in elevation up to nearly 3000 feet. The hilltops have a
general elevation of 1000 to 2000 feet. Its surface is a very
rough and irregular one; is cut up bya network of deeply incised
valleys, the seaward extension of which add to the ruggedness
of the coast line.

The general appearance of the inter-valley areas—hills and
ridges—is that of a well rounded moutonnée torm, which pre-
vailingly show among the lower hills a highly polished sur-
face, while the higher peaks are as uniformly angular, and are
very much less subdued topographic types. Some of the valley
slopes are steep, often times precipitous, often with large talus

* The writer wishes to express his indebtedness to the Cornell University Expedi-
tion of 1896, under the directorship of Professor R. S. Tarr, and of which the writer
was a member, when this work was made possible. Further acknowledgments are
due Professors R. S. Tarr and A. C. Gill, and Messrs. E. M. Kindle, J. O. Martin and
J. A. Bonsteel for valuable aid and suggestions — especially Professor Tarr, who kindly
read and criticised this paper in manuscript.

655

656 THOMAS L. WATSON

heaps at their bases. The slopes have been trenched and fur-
rowed by running water derived from the melting ice and snows.
The scarred and shattered surface everywhere testifies to the
great rapidity of frost action. The results of glaciation are con-
spicuous over all its parts, attesting the fact that the ice-cap has
over-ridden its entire surface at some previous time. Remnants
of local glaciers still exist among the higher peaks of its north-

ern border. Bowlders are abundant, while the paucity of till is
quite marked.

Owing to much variation in texture, the intimate relation-
ship of rock structure to topography is well marked, as shown in
the case of the dikes of basic rock —diabase (?) — found cutting
the gneiss in various directions. The gneiss has been intricately
folded and contorted.

LAKE CLASSIFICATION

No large lakes are found on the peninsula. The basins vary
in size from one and a half miles in length down to the merest

LAKES AND VALLEYS OF NUGSUAK PENINSULA 657

pool. The largest water bodies are confined for the most part
to the large valleys; but many tarns are scattered over the higher
lands. Bothtypes are, with one or two possible exceptions, true
rock-basins, since they are entirely surrounded by rock in place ;
for there is rarely enough till for a dam. Based primarily on
origin, the lakes are grouped under ‘‘ Rock-basins due to glacial
origin,” and on position, are further grouped as (a), highland,
and (0), valley lakes.

ROCK-BASINS OF GLACIAL ORIGIN

The highland lakes.— On account of their salient features, not
all the highland lakes can be ascribed as the direct products
of glacial erosion; but it is certain that all of them owe their
origin, either entirely or in part, to glaciation. Therefore, since
this class is in part directly and in part indirectly the products of
glaciation, and since no differentiation of those that are ice-
scoured basins from those that are perhaps only partially due to
glaciation, can be effected, they are both grouped as highland
lakes of glacial origin.

This entire group of lakes is composed of small tarns and
pools of very shallow depth. Their distribution is apparently
controlled entirely by the weaker rock structure. Where the
joint planes were numerous and intersected, tiny lakes were often
found. Generally, the larger highland basins were found
developed in the direction of the strike of the gneiss, and had
resulted from the removal of the softer layers of gneiss, by some
process of erosion. Still others were observed where these
planes of weakness were not apparent, but, in some cases, could
probably be ascribed to the result of chemical or mechanical
weakness, due to mineral distribution. The lakes are prevailingly
irregular in outline, and contain varying amounts of weathered
débris scattered over the bottoms of their basins, which is very
probably due to recent action.

Their size, distribution, position and intimate relationship to
rock structure, and irregularity of outline are sufficient evidence
of their having resulted, in part, from differential atmospheric

658 THOMAS L. WATSON

erosion. Scarcely any doubt exists against
the large share of these tarns having resulted
directly from differential ice scouring along
the line of weaker rocks. In other cases,
however, the basins have been more or less
modified by the ice advance, which served
to remove the preglacial decay, resulting in
some instances, ina probable deepening from
this cause.

Evidence has been brought forward by
others, proving that not all trace of minor
preglacial form was destroyed by the ice
advance over portions of this and the Baffin
land coast. Furthermore, that in itsadvance,
all the preglacial decay was not removed,
but that a somewhat roughened and irregu-
lar surface resulted from such action, mostly
along the lines of rock weakness. To the
combined action, therefore, of differential
preglacial weathering and ice erosion, along
the lines of weak structure, are due most, if
not all, of the group of highland lakes.

Concerning the origin of this type of lake
along the Greenland coast and other simi-
larly glaciated lands in the arctic latitudes
Professor Tarr says :*

It is noticeable near Cumberland Sound, as well
as in Turnavik, and in Hudson’s Strait, and indeed
in Greenland, that there are many basins of small
size, surrounded entirely by rock. While some of
these have no doubt been scoured out by differential
ice erosion, the position of many of them along the
lines of weaker rocks, indicates that they represent

differential preglacial weathering. The advance of
the ice in these cases has served to remove the

WDARR) Re) (St:@ Amer. iGeolaarso7.) Vols XOX nip ps
195, 196.

apiice

East

Lake bottom

West

ke

Sea level

——

Lake ‘bottom

Sea level

bone bottom

Profile of valley marked AB

Scale # =foo inches.

rs ‘

Fi

LAKES AND VALLEYS OF NUGSUAK PENINSULA 659

decayed rock, and perhaps to deepen the depressions formed by this action,
though ice erosion would not in this case be the prime cause for the basin.

These [ rock-basins] seem to be depressions caused rather by preglacial
decay than by glacial erosion, They are oftenso small and bounded by walls
so angular that origin by ice scouring seems impossible."

The valley lakes.—The line, marked ‘‘AB” on the map, indi-
cates the position of one of the largest valleys on the peninsula,
with seaward termination on the east and west sides, and is from
three and a half to four miles in length. Fig. 3 shows cross-
sections, with reference to sea level, of the east and west ends of
this valley. ‘‘A’”’ was sketched at a point in the valley 165 feet
above sea level, while “‘B” is only 15 feet above. Neither of
these has been platted to any scale. A glance at the two is
sufficient to note the contrast in outline of the two ends of the
valley. The south end, A, is filled in on all sides to an unknown
depth with perfectly angular blocks of large dimensions. This
difference in valley width for the two ends is due, probably, in
a great measure, to preglacial conditions. It is more than likely,
that the preglacial divide was located near the south end of the
valley, with its western end farther down stream, and therefore
wider. The west end of the valley is fully three fourths of a
mile wide, with inclosing walls rising 1000 feet and more above
the bottom, sloping at a steep angle—less than 45°.

The valley further holds the largest lakes distributed along
any one of the valley bottoms (see Fig. 2). Careful soundings
were made of all the lakes located in this valley, and two showed
their bottoms to be considerably below sea level. The position
in the lakes where soundings were taken are marked on Fig. 2.
After the sounding data were obtained, several possibilities
naturally suggested themselves to account for this condition, in
the lakes. A close examination of all the conditions, however,
resulted in the elimination of all save one of the possibilities.
Stream erosion with subsequent depression is eliminated on the
ground of extreme irregularity of valley bottom. On the north
and near the west end of the valley, the attitude of the strata is

1 /bid., Bull. Geol. Soc. Amer. 1897, Vol. VIII, p. 255.

THOMAS L. WATSON

660

"pna “M
“pNa "al

a
/

gy Koyo Lo NolLoIS~SSolA obi y

Noto |B0.2 S wercea oer emerm em np eae pa

eaCg

ae

c

‘Old

fA pno 2} cal

822n Woyno epee

g

SS

Ss
Y b

Ray 0 ~<

LAKES AND VALLEYS OF NUGSUAK PENINSULA 661

that of an overturned fold, whose axis is at right angles to that
of the valley. The position of the strata proved that at no
point could the valley owe its origin to folding. Rock structure
and position were also opposed to origin by differential weather-
ing. The tracing of the same and equivalent strata on the two
sides of the valley would preclude faulting. Damming by depo-
sition of morainic material is untenable, since no moraines of
any extent occupy any portion of the valley.

The only other possibility to account for these lakes is that
of ‘‘zce erosion.” A brief description of the lakes in this series,
with the closely associated glacial phenomena, will best show the
evidence for their glacial origin.

The first lake is the only one of this series with bottom above
sea level. It is located 60 feet below the valley divide and 165
feet above the surface of the middle lake. It is more or less
saucer-shaped in outline, and is, with the exception of the east
side, entirely inclosed between highly polished and striated
moutonnée forms.

ithe middle lake, marked lake No; 2 0f Pig.:2, lies immie=
diately against the high, precipitous south wall of the valley,
and inclosed entirely by moutennée forms on its north, south,
and west sides. It is entirely surrounded by rock in place with
its bottom 39 feet below sea level. The moutonnée forms on
the north side of the valley are highly polished and planed, with
glacial grooves and striae greatly intensified, reaching from the
lake’s surface up to an elevation of 100 feet. These are coinci-
dent with the trend of the valley.

The space between the middle lake and lake No. 3 of Fig.
3, is occupied by moutonnée forms of well-rounded outline and
slight elevation. Lake No. 2 drains into lake No. 3 through a
rock channel some 50 yards across and about 100 yards long,
carved between the close-lying moutonnée hills.

The lake occupying the west end of the valley lies, for most
of its length, immediately against the high, precipitous north
side. It is something over a mile in length, very narrow, and
quite irregular in outline, closely resembling a stream. It is

662 THOMAS L. WATSON

15 feet above sea level, and in its deepest part —near its head —
is 150 feet below sea level. Perfectly developed glacial grooves
and striae, with direction coincident with the axis of the valley,
extend for quite a distance along the south border of the lake.
The outlet channel is cut into solid rock, and averages from
four to five feet in depth, with a U-shaped cross-section. The
overflow passes over a low point in the divide between the lake
and fjord on the southwest side of the valley. The divide is
highly glaciated, and stands 25 to 50 feet above the lake level.
As can be seen from Fig. 3, the portion of lake near the outlet
is dotted with moutonnées rising to a slight elevation above the
waters and forming a group of small islands in the lake.
Rowlders of varying dimensions are found poised in various
positions over the tops of nearly all the largest roches mouton-
nées in this valley. It will be further observed that the valley
axis, AB of map, is approximately coincident with a westward
advance in the general glacial movement over the peninsula.
Further, that the largest and deepest water bodies are located in
the northwestern portion of the peninsula, which portion is shown
in a subsequent part of this paper to have been subjected to a
period of more or less intense local glaciation. On the high
hilltops forming the southwestern limits of the valley are found
remnants of once larger local glaciers.

- As aclass, the valley lakes observed on the peninsula, range in
size from something over a mile in length down to the smallest
size basin. In outline, some were saucer-shaped—width and
length about equal—but generally the length greatly exceeded the
width, and when so found were invariably characterized by irregu-
larity of outline. They varied from a few feet to 150 in depth, and
in all cases their circumferences were marked by rock in place,
proving them to be true vock-basin lakes. With but few excep-
tions they are prevailingly shallow and filled, more or less around
their edges, with rock fragments derived from the valley sides,
due to shattering by frost. Approximately eight to ten feet
above summer water level and along the edges of parts of a few
of the larger lakes were noted slender but perfectly formed

LAKES AND VALLEYS OF NUGSUAK PENINSULA 663

beaches. These may represent storm levels, or they may be the
result of climatic changes. While the valleys probably cannot
in all cases be ascribed to the same cause, the lakes associated
with the valleys are, apparently, the result of differential ice
erosion, and are true rock-basins, since they are walled in by
rock zm setu on all sides.

Dust wells and pools on the tce-surface—The marginal surface
area of the glacier ice was found dotted with numerous circular
holes, varying from a quarter of an inch to several feet in
diameter, and averaging probably several feet in depth. These
were filled nearly to their tops with water, and their bottoms were
invariably covered with a thick layer of dust. Professor Barton’
has described the same condition to the south of this locality
in the Umanak district, where he states, that the pits are con-
fined to a marginal zone of about one mile in width, beyond
which, and towards the interior, the ice surface becomes com-
paratively smooth. Professor Chamberlin? has observed the
same conditions farther north along the west coast, and has
fully discussed their origin in a previous number of this
JOURNAL.

Other larger pools were seen. Professor Tarr3 noted an
especially large one, occupying a depression in the ice, of about
one quarter of a mile in length in the direction of its longest
axis, very shallow in depth, and revealing clear smooth ice,
with no sediment over its bottom. No observation was made
concerning its outlet, and Professor Tarr states that the pool
probably represents a case of differential meeting.

Lakes due to other causes — Along the ice margin, lakes were
found, in places, formed by the usual ice marginal processes.
A majority of these marginal lakes are due to a walling in of the
numerous depressions of the extremely irregular surface of the
peninsula, by the more or less steep ice-front on one side, and
the slopes of the depressions of the land on the other. Each of

U@prcit., pa2 lo:

2Jour. GEOL., Glacial Studies — Greenland, IV, Vol. III, 1895, p. 215.

3 Communicated by letter to the writer.

604 THOMAS L. WATSON

these was fed by a marginal stream flowing along the ice front,
which was, in turn, made up from the numerous smaller streams
flowing off of the ice at its front. In some instances the lakes
had been recently drained revealing heavy and conspicuous silt
deposits, which necessarily were irregular in position, as is char-
acteristic of marginal lakes. Some were found draining through
tunnel outlets in and under the ice.

Morainal formed lakes, both by means of the masses ponding
back the waters, and as kettles occupying the depressions in the
morainal accumulations, were not uncommon.

Lakes noted at other points.—Rock inclosed bodies of water
similar to those on the upper Nugsuak were noted at the follow-
ing points: Turnavik Island, off the middle coast of Labrador ;
Big Savage Island, Hudson Strait ; Icy Cove, the extreme south-
ern coast of Meta Incognita; Niantilik, Cumberland Sound ; and
at several places along the Greenland coast to the south of the
Upper Nugsuak peninsula. So far as observation extended their
origin and development have been essentially the same.

At Niantilik a large number of typical rock-basins, resem-
bling in every respect the Nugsuak lakes, were observed. Where
studied, these were found developed in true strike valleys, and in
case of the larger ones, roches moutonnées islands of slight eleva-
tion and formed by the hard layers of steeply tilted gniess were
found. The character of these lakes left no doubt as to their
being true rock-basins formed in part by ice erosion. Their
entire circumferences were in many cases encircled by rock in

place.
THE VALLEYS

No grouping of the valleys according to direction could be
effected, since they were found trending with all points of the
compass. An apparent series of major valleys were observed,
cutting the peninsula in a direction varying from an almost east
and west course to one at nearly right angles to this, which
invariably had a seaward termination.

In a very general way, the larger valleys are best described
as being very deep and broad, somewhat U-shaped in outline.

LAKES AND VALLEVS OF NUGSUAK PENINSULA 665

There are wide variations, however, from the steep sided and
precipitous profile to that of considerably gentler slope. Frost
action has wrought widespread results on the original glacial
outlines of this form, resulting generally in a modification tend-
ing toward a less precipitous outline.

It has already been stated that numerous dikes of a basic
eruptive rock, probably diabase, are found cutting the gneiss in
an approximately vertical attitude. The basic dike rock of the
peninsula has yielded more readily to the attack of the
atmospheric agencies than the inclosing gneiss. Subsequent
ice advance removed most of the residual decay, resulting in some
instances, in the ice eroding considerably below the line of actual
decay, determining thereby one set of the major valleys. The
U-shaped outline is especially applicable to this type of valley.

Similar conditions apparently prevailed at Turnavik, Labrador,
as on the Nugsuak. The rock is a coarse porphyritic gneiss cut
by dikes of a basic eruptive, many of which have been eroded
to a depth of some 20 to 25 feet by the ice, and in some of which
residual decay was still to be seen, indicating a greater preglacial
decay of the dike than country rock.

In the Umanak district of North Greenland, Professor Bar-
ton,* observed that the dikes of eruptive rock had not been
eroded below the level of the inclosing gneiss, but instead,
they were found, in some instances, standing “out in relief above
the oneiss:,”

No petrographic study has been made of the rocks in the
localities mentioned above, hence it would not be safe to say
whether the difference could be accounted for on lithologic
grounds, or whether it is due to a difference in glacial conditions.

A second type of valley, but of minor importance, on account
of slight development, was noted, the origin of which was trace-
able to the etching out of the softer rock layers in the highly
tilted strata by differential atmospheric weathering, and can
therefore be classed as strike valleys.

Subsequent to the period of widespread general glaciation,

* BARTON, GEo. H., Technology Quarterly, 1897, 10, 236, 237.

666 THOMAS L. WATSON

the northern ends of the valleys have undergone considerable
modification from a period of local glaciation, which is now con-
fined to the northern side of the peninsula, and in its last declin-
ing stage Owing to the work of local glaciation, more or less
contrast is observed in the topography of the opposite ends of
the approximate northwest-southeast trending valleys (see
Fig. 3). Glacial filling, principally bowlders with some till;
abundance of typically developed roches moutonnées, glacial
grooves, striae, planing and _ polishing, conspicuously char-
acterize all of the major valleys.

A large number of the major valleys were associated with
dikes of basic rock. So far as studies were extended, the mass
of fact pointed to the conclusion, that this type of valley was
due to differential preglacial decay with subsequent ice erosion.
The entire set of major valleys, everywhere viewed on the penin-
sula, are distinctly preglacial; and while their origin was not
apparent in every case, they have all suffered considerable
subsequent modification from ice erosion.

A parallelis probably found in Canada, where Dr. Robt. Bell’
has observed greenstone dikes protruded into granites. The
dikes have subsequently been worn out and at present form

valleys occupied by lakes and streams.
Tuomas L. Watson.
GEOLOGICAL SURVEY OF GEORGIA,
Atlanta, Georgia.

IBELL, Dr. Rost., Bull. Geol. Soc. Amer. 1894, V, 364.

ENE AE VP LO. PRAME A WORKING HYPOTHESIS
OF SHE sCAUSE OF GLACIAL, PERIODS, ON AN
ATMOSPHERIC: BASIS

(Continued)

SPECIAL APPLICATION OF THE HYPOTHESIS. TO THE KNOWN
GLACIAL PERIODS

Ir now remains to specifically apply the hypothesis to the
recognized glacial periods. At present only those at the close
of the Paleozoic and Cenozoic eras are sufficiently determined to
require discussion.

The mapping of the Pleistocene glacial deposits is sufficiently
complete to show their great features, and reveals a strong
development in the northern hemisphere, and at the same time
a quite peculiar localization. The analysis of the deposits has
progressed far enough to show that the glacial period was
marked by pronounced oscillations of both the major and the
minor kind. Interglacial epochs of a declared character may be
assumed to be fairly demonstrated, while the glacial epochs
themselves were attended by rhythmical stages of progress, as
most pointedly brought out by recent detailed field work in the
Mississippi and St. Lawrence valleys, notably that of Mr. Leve-
rett and of Mr. Taylor. These rhythmical features are made the
subject of a special discussion by Mr. Taylor in a paper entitled
‘“Moraines. of _Recession and their Significance in ‘Glacial
liheory. =

To be really applicable to Pleistocene glaciation a working
hypothesis must therefore not only postulate agencies capable
of producing a glaciation covering the American plains down to

JOUR. GEOL., VolvV., No: '5, 1807; pp. 421-405. See also “The Great: Ice=
Dams of Lakes Maumee, Whittlesey, and Warren,” American Geologist, Vol.
XXIV, No. 1, July 1899, pp. 6-38, and the review of this paper by MR. GILBERT in
the last number of the Jour. GEOL.

667

668 LC CLA MG TALON

37° north latitude, and mantling also the plains of middle
Europe and high altitudes quite generally, but it must assign
agencies for the oscillations which attended it.

General cause—The atmospheric hypothesis finds a genera]
cause for the Pleistocene glaciation in that notable extension
and elevation of the land which reached a climax near the close
of the Pliocene period.” lt isi) not, however, through jtsmdinect
topographic influence that this was accomplished, though this may
have been incidentally tributary, but through its effects on the
constitution of the atmosphere. The recently named Ozarkian
or Sierrian period embraces the specially effective stage of this
great land area, and it is with much pleasure that I support the
emphasis laid upon the significance of this period by Professor
Le Conte in his paper in the last number of the JouRNAL,” though
I interpret that significance in different terms. The wide extent
and high elevation of the land at that time are so strongly set
forth by Dro We Conte as to leave no (need ror additional
emphasis here.

A rude estimate of the land area in Middle Tertiary times,
when the climate was mild far to the north, gives about
44 million square miles. A similar estimate for the Ozarkian
or Sierrian period gives about 65 million square miles, while the
received estimate of present land is about 54 million square
miles. Taking the Middle Tertiary area as a basis of compar-
ison, the land was increased in the Ozarkian period about 47
per cent., and afterwards fell off to the present area, which is 23
per cent. greater than that of the mid-Tertiary. It is probably
conservative to estimate that the average elevation of the
Ozarkian land was at least two or three times, perhaps three or
four times, as great as that of the mid-Tertiary. Combined in
the light of the suggestions previously made regarding elevation,
these indicate a very great change in the effective contact of the
atmosphere with the earth. If we measure the actual contact
by the surfaces of the grains, pores, fissures, and minute crevices
with which the air and the atmospheric waters come in contact

* Pp. 525-544.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 669

—and this is the true contact area—the increase will appear
impressive.

As in other cases, there was here also a self-accelerating
action. As land was elevated, its underground water level was
at first carried up measurably with it and lay near the surface.
Trench-cutting accompanied it, to be sure, but at a slower rate.
As the declivity increased the cutting and transportive power of
the drainage increased, and as the dissection of the land pro-
ceeded, the water level was lowered and the effective zone of
atmospheric contact augmented. The very process of degrada-
ion, up to a certain stage, increased the facilities for the chem-
ical action of the atmosphere. In general it may be observed
that degradation reacts upon itself favorably for atime. The
cutting of certain of the western plains into ‘‘bad lands” and
the gullying of the cultivated fields in certain parts of the south-
ern states are striking examples of current self-accelerating
processes of the more mechanical sort.

Concurrent with this increase of the atmospheric contact-
area on land there was a reduction of sea surface, the habitat of
lime-secreting life, and, xofa bene, an almost complete oblitera-
tion of the epicontinental seas and sea-shelves which were the
parts of the sea bottom that were by far the most prolific in
carbonic-acid-freeing marine life. Shallow-water marine life
must have been very generally driven down on the abysmal
slopes and on to such limited deeper shelves as may have been
brought within reach by the lowering of the seas. The conse-
quent lessening in the rate of freeing of carbon dioxide is
assumed to have been great, and this codperated with the accel-
erated consumption on the land to hasten the depletion of the
atmosphere.

Besides this, when any appreciable reduction of temperature
followed these codperating agencies, it tended of itself to check
the lime-secreting life of the ocean, and at the same time to give
the oceanic waters greater absorptive power and less dissociative
activity, thus calling into operation a group of secondary agen-
cies which intensified the effects of the primary agencies.

670 T. C. CHAMBERLIN

Now the task assigned this remarkable combination of agen-
cies is not a formidable one. If we take the largest of the cur-
rent estimates of the present atmospheric content of carbon
dioxide, viz. .06 per cent. by weight (comparable to .0o4 per
cent. by volume), the mid-Tertiary atmosphere should have con-
tained .15 per cent. to’.18 per cent. of carbon dioxide, and that
of the glacial period .03 per cent., following Dr. Arrhenius’ esti-
mates. That is to say, for the reduction of the carbon dioxide
of the Tertiary atmosphere from the assigned .15 per cent. or
-18 per cent. to the assigned .03 per cent. of the glacial period,
we have an estimated increase of land area of 47 per cent., and
an increase of elevation of 100 per cent. or 200 per cent., and
perhaps more. To produce the present amelioration we have a
falling off of about one half in each of these items.

Numerical data, which will be given later, indicate that
something like 5,4) of the carbonic acid of the air is now taken
out annually. If the same amount is returned, the constitutional
status is preserved. But if the foregoing agencies that codper-
ated in late Pliocene and early Pleistocene times to disturb the
balance between removal and return were effective to no more
than 10 per cent. of the total rate, it would have been capable of
reducing the assigned mid-Tertiary content of .18 per cent.
carbonic acid to the assigned glacial content of .03 per cent. in
50,000 years. It is not, of course, supposed that the rate would
be constant as the state of enrichment changed, and note of this
will be taken later, but the computation serves to show how
effective a disturbance in’ the relative. rates jot jsupplygiand
removal becomes when such action bears so high a ratio to the
total mass of carbon dioxide in the air. It may also serve to
show that the hypothesis is assigning agencies whose supposable
quantitative competency is abundantly adequate to the results
imputed to them.

ASSIGNED CAUSES OF GLACIAL OSCILLATION

It has been already noted ‘repeatedly that the assigned
causes of glaciation are self-accelerating in certain significant

HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 671

phases. The salient effect of this, reasoning on general prin-
ciples, must be to push results to an extreme from which reac-
tion is inevitable. Let us consider this in detail. It is thought
that there were three dominant agencies concerned in this,
modified by several subsidiary ones.

1. A necessary consequence of the accelerated rate of trans-
mission of carbon dioxide to the sea, combined with a slackened
rate of release in the sea, was an accumulation of oceanic carbon
dioxide. The primary form of this was an increase of the car-
bonates.

2. The cooling of the sea waters which attended the process
reduced the dissociation, and hence the carbonates were more
nearly full bicarbonates than before. There were, therefore, not
only more carbonates, measured by the bases, but they carried more
carbon dioxide in proportion to the bases.

3. With the growth of the snow-fields attendant on the
progress of glaciation, there was an increase of reflection of the
sun’s radiation and a reduction of its absorption. Computation
shows that the albedo is an important factor.

Subsidiary to these there were the following:

4. There was an increase in the absorption of carbonic acid
in the ocean, resulting from the lowering of the temperature.
This, however, was offset by the declining partial pressure of the
carbon dioxide in the air, and, as the two seem to be of the
same order of magnitude, they may be set aside for the present.

5. With increasing cold there was a less rapid decay of
organic matter and a less compiete release of carbon dioxide.
Over against this, however, there was a reduction in the amount
of carbon locked up in living organic matter. It is difficult to
form a trustworthy estimate of either, but it may be provisionally
assumed that they belong to the same order of magnitude and
may be set aside together. At any rate, any residual difference
would not apparently be a notable factor.

6. The majority of chemical authorities state that the solu-
bility of calcium carbonate in water saturated with carbonic acid
increases with a lowering of temperature through ordinary

672 TAC CILAMIBIGRGIN:

ranges. Unfortunately there is not complete unanimity on this
point... But, if ‘this be*true; as, the temperature: fell thevsolvent
action of the carbonic acid of the land waters upon the limestone
was increased. Over against this was a probable reduction of
the action of organic acids. Probably the decomposition of the
silicates went on at a lower rate, but, as it was much less than
one fifth of the whole action, its reduced rate is not very
material here.

As the carbonic acid of the air was diminished, its action on
the land surface declined—though not at a proportional rate —
but long before it could offset the enlargement of the contact
area aided by the sea action, glaciation would be far advanced,
if the previous estimates hold good.

Setting aside, as being measurably balanced, or as being of
minor or uncertain value, all but the first three items, which are
clearly factors of great potency, we find at first a strong disposi-
tion toward the acceleration of the depleting process.

But this, although a pronounced influence in the early stages
of refrigeration, could not continue indefinitely, for the process —
involved the conditions of its own arrest.

The arrest of the depletion and the inauguration of the reaction.—
With the development of glaciation, the agencies that tended to
counteract atmospheric depletion received a powerful ally in the
ice-sheet itself., Dhe spread oisithe ice over they sugiaceppie=
vented further effective weathering of the area so covered and
correspondingly arrested atmospheric depletion. The total area
covered by glaciation at its maximum was probably not far from
8 million square miles, or nearly 15 per cent. of the land surface.

Besides this, the area outside of that actually covered by the
ice-sheets was probably affected by prolonged freezing during
the winter stages, and was perhaps to some extent permanently
frozen beneath the surface, and this arrested solvent and chemi-
cal activity. If the modest figure of 5 per cent. be assigned for
this supplementary effect, 20 per cent. of the functional area
wovld be withdrawn from action. Whether this numerical esti-
mate be correct or not, it may be assumed that if a given amount

HVPOTAHESIS OF CAUSE OF GLACTAL PERIODS 673

of withdrawal, combined with associated agencies, were not
sufficient to arrest the progress of glaciation, the glaciation
would have continued to extend itself until the point of balance
was reached. It is, perhaps, not too much to assume that the
extension of glaciation and its concurrent agencies mark in
themselves the measure of preponderance of the depleting
agencies at the stage when glaciation began. That is to say,
after the depleting agencies had brought the air’s carbonic
content down to the point at which the glacial centers were
inaugurated, these agencies were still preponderant over the
repleting agencies to some such extent as 20 per cent., more or
less.

While it does not seem necessary to our general purposes to
consider the associated agencies of arrest, if these views be cor-
rect, they possess an interest of their own, and may be men-
tioned briefly.

With little doubt the lowering of the temperature lessened
the rate of decomposition of the silicates, though frost action
aided in disaggregating them mechanically and in thus increas-
ing the atmospheric contact. On the other hand, while the
authorities are not altogether agreed, the weight of the latest
opinion supports the view that the limestones would be dissolved
by cold water saturated with carbon dioxide faster than by warm
water, other things being equal. The cold waters would quite
certainly contain more absorbed carbon dioxide than warm
ones. Probably other things were not equal, for the vegetable
action and the organic acids probably lent less and less aid as
the temperature fell. It is not clear what the balance of these
influences combined would be. Whichever way it leaned, it
does not seem to have been of decisive moment.

As previously remarked, the progressive removal of carbon
‘dioxide from the air reduced the amount of its action, but not
proportionately. While this lessened the depleting action it
does not seem to have reached decisive moment, at least not
until a late stage in the process of depletion.

Meanwhile, in the ocean, conditions favoring reaction were

674 Ll. €: CHAMBERLIN

gathering force as the result of the processes in action there.
The ocean was accumulating carbonates and augmenting their
degree of bicarbonation with the increase of cold. Now it is
obvious that if the loading of the ocean with carbonates were
to proceed to the point of saturation, inorganic processes of
precipitation and dissociation would come into play to an
extent that must necessarily balance all further accessions of
material. It does not appear, however, that there is enough,
or even nearly enough, carbon dioxide in the air to bring
about a condition of full saturation of the ocean with bicarbon-
ates, even if it were all to take that form, and were to be con-
veyed completely to the sea. But the movement toward satura-
tion should increase in some degree, probably small, the
efficiency of inorganic agencies tending toward precipitation,
although it could become notably effective only after prolonged
accumulation.

The concentration of carbonates in the ocean was somewhat
aided by the removal of water required to form the great ice-
sheets. Ona rather large estimate of the mass of the ice-sheets,
this extraction might possibly reach 5 per cent. of the volume
of the ocean.

There would probably be a progressive evolution of lme-
secreting life adapted to the cooled waters, and this would
increase the rate of carbonic release and contribute to a reversal
of action.

None of these subsidiary agencies, nor all combined, seem
to have been controlling factors.

It is notable that some of these subsidiary agencies, on
both sides, are final in themselves and quite without retroactive
possibilities. When once their work was done there was no
resilience. It was quite otherwise with the ice mantling and the
ocean loading. Far from being final, these contained in them-
selves the potentialities of reaction and gave vigor to the reac-
tion when it took place.

Agencies that precipitated reaction—When once the reactive
agencies had reversed the relative rates of enrichment and

FIVPOTHESIS OF CAUSE: OF GLACIAL PERIODS. 675

depletion and there began to be an increase of carbon dioxide in
the air, the following influences would codperate to hasten and
intensify the reactive movement.

1. The dissociation of the second equivalent of carbonic
acid associated with the carbonates of the ocean would be
increased, and as the temperature rose from the diffusion of the
freed carbon dioxide into the air this would be still further aug-
mented by its own reactive effects. This is one of those inter-
esting agencies whose effects at once become causes of further
like effects.

2. The increased warmth would call forth more lime-
secreting life in the ocean, and thus also hasten the freeing
of carbon dioxide, and this again would react favorably on
itself.

3. The increase of water from melting ice would some-
what extend the shallow-water zone and favor lime-secreting
life. If the land were depressed by the load of ice, as some sup-
pose, this would increase the sea area and favor lime-secreting
life. With this may be associated the falling of the water level
in the high latitudes (to which it had been drawn by the gravi-
tation of the accumulated ice mass) and a corresponding rise of
the water level in lower latitudes. Since the lower-latitude life
is more abundant than the high-latitude life, and more effective
in extracting lime, the shift would involve a gain in lime-secret-
ing potency.

4. The increased decay of organic matter attendant on the
warmer temperature would develop carbon dioxide; but over
and against this must be set the increased carbon locked up in
the augmented living matter: These, as before, are’set aside, as
perhaps mutually offsetting each other.

5. Lhe ianerease of temperature arising from the preceding
causes would increase the water vapor in the air and thereby add
to the thermal capacity of the atmosphere, and this would react
favorably upon itself and upon the other agencies favored by
high temperature.

Thus the reaction once started would be self-augmenting,

676 LT 6. CHAMBERLIN,

until the fundamental conditions were changed or the reaction
was checked by its own ulterior consequences. The sequences
may be easily followed. The carbonates of the sea, which had
been augmented during the epoch of glaciation were now dimin-
ished and limestone was more actively deposited. The ocean,
previously fattened in carbonates now became lean. Soalso the
carbonates themselves, that before were quite plump bicarbon-
ates, now became degraded to a mixture of normal and acid
carbonates. In short, the ocean holds less free and feebly-com-
bined carbon dioxide and the air holds relatively more. As the
ocean is now estimated to contain from eighteen to twenty-five
equivalents of atmospheric carbonic acid in the free and feebly-
combined states, a moderate fluctuation in its content would
cover the full range of atmospheric variation required to pro-
duce the climates under discussion, according to Arrhenius.
On the supposition that the glacial epoch was produced by a
reduction of the carbonic content of the atmosphere to one half
the present amount. it would only be necessary for the ocean to
release -2 or 3 “per cent. of its releasable carbon dioxide to
restore the atmosphere to the present condition. If the ocean
gave up 4 or 5 per cent. of its releaseable carbon dioxide
the climate would be notably milder and more equable than the
present. Assuming the correctness of Dr. Arrhenius’ conclu-
sions, it would seem from these considerations that there is
nothing forced or violent in the supposition that an effective
interglacial epoch might be brought about by the reactive
agencies indicated.

Recrudescence of glaciation.—\f the land area of the globe as
a whole remained large and high notwithstanding such local
depressions as have been attributed to the weight of the ice and
the effects of low temperature; or, more precisely, if the atmos-
pheric contact area remained large, the conditions for a renewal
of glaciation would again prevail because the renewal of warm
temperature, the enrichment of the atmosphere, and the deple-
tion of the ocean would restore the original action. So soon as
the ice had retreated from the land, the weathering of the

HNPOLHMESTS OL SCAUSE OF (GLACIAL, PERIODS 677

uncovered area would be renewed. This, of course, would begin
so soon as the retreat began, and increase in a corresponding
measure; but it is a slow process, while the reactions of the
ocean are relatively rapid —indeed they should keep close pace
with the rise of temperature which they induce. There should
be no appreciable lag. After the retreat of the ice a new sur-
ficial factor would come into play, the sheet of drift spread over
the:suttace. (In)so far as this consisted, of wndecomposable
matter blanketing decomposable matter, it would interfere with
the progress of decomposition, but in so far as it consisted of
limestones and silicates ground to a flour and exposed to the
atmosphere, it would facilitate chemical action and expedite a
second depletion of the atmosphere and through it a second
term of glaciation. Aside from the effects of this mantle of
drift and such changes of topography as might have occurred,
the conditions for the renewal of glaciation would be, so far as
I see, as effective as they were at the outset. Assuming that
they were equal to the preceding, a second glaciation equal to
the first is to be postulated, and a corresponding reaction at
length, as in the previous case, due to like agencies. Thus a
series of glaciations and deglaciations should follow each other
until the general causes lying back of glaciation had disap-
peared.

In so far as the land, on the whole, settled back toward sea
level or was worn away, or, by any other agency, lost its degree
of effective ‘exposure to ‘the atmospheric action, in so far the
conditions of glaciation would disappear. Pursuing the normal
history which follows a period of great land elevation, it is to be
presumed that there would be a gradual reduction of the land
surface and land elevation, and that hence the conditions pro-
ductive of glaciation would gradually pass away. On such an
assumption it is presumed that the recurrent glacial advances and
retreats would become more and more feeble until the series van-
ished. Nominally, then, the glacial and interglacial epochs
should form a rhythmical series declining from large oscillations
at the maximum to lesser and lesser oscillations as the series

678 LG: CLAM IB TERTETIN,

disappeared. This seems to correspond with the observed oscil-
lation of glaciation in both Europe and America.*

INTERCURRENT AGENCIES

Without question the normal series of glacial oscillations
just postulated would be subject to intercurrent influences which
would be liable to disturb, perhaps quite seriously, its regularity
and symmetry.

1. Any notable movement in the land which affected the sum
total of the atmospheric contact area would disturb the sym-
metry of the series.

2. Any notable change in the original supply of carbonic
acid through volcanic action or other agency would produce
obvious modifications. The deformation of the body of the
earth out of which the conditions of glaciation are assumed to
have sprung would doubtless be favorable to volcanic action, and
if this reached a degree of intensity sufficient to add appreciably
to the carbon dioxide of the atmosphere, it would radically
affect the ongoing of the process. That there was extensive
vulcanism nearly or quite concurrent with glacial action has been
urged by some geologists; indeed, glaciation has even been
attributed to volcanic action.

3. The precession of the equinoxes has been regarded by
many thoughtful students of glaciation as an influential agency.
If affective, it would superpose a rhythm of its own upon the
rhythm postulated by this atmospheric hypothesis. For specific
illustration the extensive series of moraines which marked the
later stages of the Wisconsin epoch of glaciation are referred by
Taylor to precessional influence, while the Wisconsin glaciation
itself would, under the atmospheric hypothesis, be referable to
atmospheric depletion. The most serious question which here
arises is the compatability of the prolonged period implied by
Taylor’s interpretation with the rate of reaction implied by the

«The Classification of European Glacial Deposits, Jour. GEou., Vol. III, No. 3,
pp. 241-269, JAMES GEIKIE; The Classification of American Glacial Deposits, zdzd.,
pp. 270-277, 1. C. CHAMBERLIN; editorial, zdz¢., Vol. IV, No. 7, October-November
1896, pp. 873-876.

WVPOTHESLS OF CAUSE OF GLACIAL PERIODS 679

atmospheric hypothesis.t This will be more evident as we touch
on the time rates.

4. The change in the eccentricity of the earth’s orbit which
Croll has made the foundation of his beautiful hypothesis of
glaciation, if not found competent to produce general glaciation
itself, might still be effective in producing climatic changes of
less degree, and might superpose important modifications upon
the series postulated by the atmospheric hypothesis. It may
be remarked in passing, however, that the computed variations
of eccentricity of distant periods of the past do not rest on so
firm a mathematical basis as is currently supposed.

It is obvious that these and other possible agencies might
work concurrently with the atmospheric influences, or antago-
nistic to them, in either case distorting and masking the normal
rhythmical expression which a purely atmospheric series would
assume.

DO THE TIME RATES FALL WITHIN WORKABLE LIMITS?

The working capabilities of a glacial hypothesis are some-
what severely conditioned by its time factors. It must not only
present a satisfactory correlation between the time of occurrence
of glaciation and that of the assigned cause, but the rhythmical
action of the cause must be consonant with the rhythmical history
of glaciation. That the Pleistocene glaciation followed the
Ozarkian or Sierrian stage of elevation at an appreciable dis-
tance, I hold to be demonstrated by the relations of the glacial
deposits to the eroded topography of that period. On the other
hand, there is no evidence of a prolonged interval, geologically
speaking. The atmospheric hypothesis demands that the accel-
erated erosion due to elevation (or rather to the dissection that
followed elevation) should have continued long enough to
remove about three times the present atmospheric content of car-
bon dioxide before glaciation could begin, following Arrhenius’
computations. This removal could only be accomplished by the
excess of consumption of carbon dioxide over supply and there is

‘See GILBERT’S review in last number of this JOURNAL, p. 621.

680 LT. Cs CHAMBEREMN:

reason to believe that the rate of supply from the interior was
greater than the average on account of crustal disruption and
volcanic action. There seems, therefore, little ground to think
that the glaciation should have followed closer after the
elevation than it seems to have done. It would seem rather
that the hypothesis was~ happy in this time relation at
least.

With most geologists, I doubt not, the chief question will be
whether the postulated agencies could cause the glacial oscilla-
tions, involving the removal and reproduction of the ice, in
large part or in whole, as rapidly as the field evidence requires.
Present measures of glacial rates and times are quite uncertain
but not indefinitely so. Some rude approach to their value may
be attained. Recently expressed opinions regarding the time
since the last ice retired from the site of Niagara River, and
inaugurated the erosion of its gorge, lie between 7000 and
33,000 years, which we may average at 20,000 years. I place
no special confidence in this figure, but it is rudely representa-
tive of the average order of magnitude of expressed opinion.
This represents only a part of the time since the beginning of
the deglaciation that removed the Wisconsin ice-sheet. Accord-
ing to Taylor’s views it would be only a very small part. 1
doubt if any careful geomorphic geologist familiar with all the
phenomena involved would seriously consider an estimate that
made it much morer than one half ‘at the *most4 so mthateant
would apparently not be straining the evidence to take 40,000
years as a rude measure of the time since the beginning of
the retreat from the outermost moraine of the Wisconsin
stage. However, this may probably be cut in half and halved
again without over-straining the possibilities of the hypoth-
esis.

This is the time of retreat. An interglacial epoch involves
not only the time of retreat, but the time of interglacial mildness
and the time of re-advance. The best specific data now avail-
able in America for estimating these elements are undoubtedly
those afforded by the excavations about Toronto which have

HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 681

been so fruitfully cultivated by Hinde, Coleman, and others.'
(1) The time occupied in the ice retreat is there almost without
second. (2) The duration of the mild climate is recorded: in
thirty-five feet of clays and sands. It is also implied in the time
necessary for the migration of the Paw Paw, Osage Orange and
other trees from more southerly regions to this rather northern
locality, and also for the migration of the clams and other mol-
luscs from the Mississippi waters to this rather distant region.
Both of these migrations were probably rather slow processes.
(3) The initiation of the returning cold is recorded in 150 feet
of fine stratified peaty clays and sands. (4) Following this
there was an unknown period occupied in the transition from the
conditions of deposition, during which the preceding series had
been formed, to the conditions of effective erosion which fol-
lowed. To suppose that this transition was due to the removal
of an ice-dam that had lingered in the lower St. Lawrence seems
quite untenable for a long, mild period and a long, cool, but not
glacial, period had intervened. It was probably due to the cut-
ting down of the drainage outlet, or to a surface movement, or
the two combined, and hence probably occupied an appreciable
time. (5) There then followed a period of erosion comparable
to that since the last ice invasion. Succeeding this came the
re-invasion of the ice-sheet.2 These data seem to fairly imply
that the interglacial epoch represented at Toronto was several
times as long as the postglacial epoch.

While nowhere else has so complete a record been found,
many estimates of the differences of erosion of the several till
sheets in the Mississippi valley, where the formations are well
deployed and happily suited to such studies, have been made

™GEORGE JENNINGS HINDE: Glacial and Inter-Glacial Stages of Scarborough
Heights. Can. Jour. 1878, p. 388 ef seg.

A. P. COLEMAN: -Am. Geol., Vol. XIIL, February 1894, pp. 85-95. Ditto. Jour.
GEOL., Vol. III., No. 6, 1895, pp. 622-645.

?Canadian Pleistocene Flora and Fauna: Report of the Committee consisting
of Sir J. W. Dawson (chairman), Professor D. P. Penhallow, Dr. H. M. Ami, Mr. G.
W. Lamplugh and Professor A. P. Coleman (secretary), appointed to further investi-
gate the flora and fauna of the Pleistocene beds in Canada.

682 LT. €. CHAMBERIGDN

by experienced glacialists, and their concurrent judgment is that
the least of the notable interglacial intervals was at least two or
three times as great as the postglacial interval. It would not be
exceeding current judgment, therefore, to assign from 80,000 to
120,000 years as the duration of a typical interglacial epoch.

But in the interest of conservatism let the postglacial interval
be taken at 10,000 years and the interglacial at 20,000 or 30,000
years. Whisseems to) me excessively (‘consenvative: sy ligthe
assigned agencies can affect a reénrichment of the atmosphere
in carbon dioxide to an amount somewhat exceeding the present
content and then again a depletion of one half within 20,000 or
30,000 years, the hypothesis will not be excluded by time
limitations.

We have the following pertinent data based in part on
Reade’s' estimates of the present rate of removal of carbonates:

Total mass of the atmosphere - - - - - 5X 10% tons
Mass of atmospheric CO, (reckoned by weight at .0006) - 3X 10” tons
Total mass of CO, taken annually from the atmosphere - 162X107 tons -
Mass of CO, consumed annually in original carbonation

(reckoned by area at 20 per cent. of the land) — - - 27X107 tons

If reduced one half on account of the slower rate of
decomposition of crystallines it will be 13.5107
tons, in which case the other half is to be added to
the following item, if Reade’s estimates are correct.)
Mass of CO, consumed annually in forming bicarbonates - 135X107 tons
Time required at this rate to consume total atmospheric
CO,, assuming no return” - - - - - - 1852 years
Time required at this rate, without return, to consume
one half atmospheric CO, (the reduction requisite
for glaciation.) - - - - - - - - g26 years
Time required to consume half the ‘free’ and “loose”
CO, of the ocean (estimated at 18 times that of the
atmosphere) without return - - - - - 16,668 years

Time required to consume half the CO, of the atmos-
phere and the ocean combined, without return - - 17,594 years

The last items which involve the reduction of the carbon
dioxide in the ocean as well as in the atmosphere are not really

tLoc cit. on p. 569.

FVPOIM SIS OF CAUSE OF GLACIAL. PERIODS. 2083

pertinent to the discussion, if the foregoing doctrine relative to
the mode of action of the ocean during a glacial period is
correct, for it is there maintained that the ocean does not give
up its carbonic acid with increasing depletion of the atmosphere,
but, on the contrary, increases its content. They have some
interest, however, in connection with it and with other phases of
the atmospheric hypothesis which the reader may possibly wish
to consider. They also have some pertinency to the discussion
of Paleozoic glaciation, to be taken up presently.

We are here concerned especially with the rate at which
atmospheric carbonic acid may be consumed to the amount of
one half the total content. For convenience, no account has
been taken of the return of carbonic acid from the ocean or
through organic action. We reach the rather startling result
that if there were no return, the decomposing and solvent action
on the present contact area would consume one half of the
atmospheric carbon dioxide in less than 1000 years. This
result, based on Reade’s estimate, may be checked by independ-
ent computation on a more familiar basis and by different modes
of computation. For example, by assuming the average rate of
degradation of the land surface to be one foot in 5000 years,
and that the carbonates constitute 15 per cent. of the material
removed, one half of the carbonic acid of the atmosphere would
be consumed in 1248 years, if there were no return; or in 1000
years if the degradation was one foot in 4000 years.

The actual depletion must, of course, depend upon the excess
of this rate of removal over the rate of return. I have already
endeavored to show that there was a very large fluctuation in the
conditions that determined the relative rates of consumption and
return, notably that the land of the Ozarkian time was more
than 20 per cent. greater in area than the present land, and that
its elevation was probably 100 per cent. or 200 per cent. greater
at the maximum stage of protrusion. And this was correlated
with codperating conditions in the ocean. Both of these esti-
mates, however, must be considerably reduced to give a safe
measure of the area which was operative at the time of the

684 Ll. C. CHAMBERETN:

inter-glacial epochs, or at least some of them, for there is abundant
evidence that the land was not then so greatly elevated as in the
Ozarkian or Sierrian period.

Instead, therefore, of combining 20 per cent. increase of land
area with 100 per cent. increase of elevation, and these with the
coéperating 20 per cent. reduction of sea area, the destruction
of sea-shelves, and the restraining effects of lowering tempera-
tures, as we are entitled to in bringing down the rich Tertiary
atmosphere to the lean conditions of the glacial period, let us
content ourselves with some modest fraction of these intensifying
combinations. If we only assume that the agencies of deple-
tion were superior to the agencies of return by the amount
of Tor per cent., (heydepletion requisite to" bring on a glacial
epoch, starting with atmospheric conditions like those of the
present, would be effected in less than 10,000 years. If, there-
fore, we over-generously allow as much time for deglaciation as
for reglaciation, an interglacial epoch might not require the
operation of the postulated agencies for more than 20,000 years,
so far as they themselves are concerned. The development of
the ice-sheet might take more time, but we have little or no
data for estimating this. If 10,000 years additional is allowed
for this the total remains at the modest figure of 30,000 years.

It would not seem to be pushing the data previously given to
extremes to postulate a larger percentage of difference between
depleting and repleting agencies than Io per cent., which would
make the requisite atmospheric depletion possible in a shorter
period. It is probably not extravagant to assume that the differ-
ence might rise to 20 per cent., in which case the requisite
time would be brought down to extremely modest limits. It is
difficult to see how anyone who studiously considers the
phenomena of the Toronto interglacial epoch could assign to it
a duration less than is compatible with these agencies, as here
interpreted. It would seem, therefore, that the hypothesis is
not excluded from the working category by inadaptibility to the
time rates of the phenomena which it seeks to elucidate.

There is not likely to be any serious question respecting the

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 685

timesratess at the other extreme, that is, that the. agencies
necessarily act too rapidly to correspond to the phenomena. Of
course, in the final adjudication of the hypothesis, it will be
necessary to show that its-time rates not only might correspond
to the time rates of the phenomena, but that they did so, but
this is a labor of the future, and is obviously dependent upon a
very notable extension of precise knowledge, which it is the
purpose of the hypothesis to aid in calling forth. It is sufficient
here to show that reasonable postulates, based on a reasonable
estimate of the phenomena, fall within compatible limits.

T. C. CHAMBERLIN.
(To be continued.)

THE NAMING OB ROCKS

Introduction of new names.—tIn the early days of petrography
it was supposed that there existed rock types as definite as ntin-
eral types. Following this hypothesis, a rock found which was
different from any rock before described was immediately given
anew name. This went so far that an altered rock was given a
family name, as in the case of diabase, an altered dolerite. After
some years a scheme of nomenclature was worked out which was
supposed to be approximately complete. For a time subse-
quently, when a rock was discovered having a somewhat different
character from previously known rocks, it was referred with
modifying mineralogical prefixes to some of the so-called types.

A few years ago another period of name-giving was inaugu-
rated. During this period, which continues to the present time,
petrographers have introduced numerous new, independent
names, both for long-known and for newly-discovered varieties
of rocks. Since 1890 more than fifty new names have been
added to the nomenclature of the igneous rocks, a larger number
than young petrographers were obliged to know the meaning of
before 1890. The stage through which petrography is passing
is somewhat similar to that through which at one time paleon-
tology passed. One might almost think that petrographers were
seeking to find varieties of rock slightly different from those
before known in order to give them new names.

Method in giving new names——The method of petrographers
in proposing names, so far as any method is discoverable, is to
give an independent name to each rock which is slightly differ-
ent from any previous rock found, without reference to any defi-
nite plan of nomenclature. The greater number of the names
are not proposed to designate varieties which are subordinate to
previously recognized kinds of rocks, but are names coérdinate
with those before used. In petrography, a binomial nomencla-

ture thus far has not been generally adopted, and therefore it has
686

THE NAMING OF ROCKS 687

not been possible to drop the new name and place the thing refer-
red to under a larger division, as one may drop the specific name
of a new fossil and speak only of the genus to which it belongs.
Furthermore, the new names of petrography are in most cases
unlike most of those in biology or in mineralogy, in that the
things described and given names have no clearly distinguish-
able characteristics by which they may be recognized. Asa
result of this inherent vagueness, it is very difficult indeed, from
the descriptions published, to obtain a clear conception of what
is meant by many of the new petrographical names. Indeed, it
may be doubted whether many professional petrographers, to
say nothing of those who work in other lines of geology, havea
definite conception of the meaning of many of the fifty or more
names which have been proposed since 1890.

Principle underlying naming of rocks.—In giving numerous
new names to rocks, while no principle is announced by the
petrographers, the underlying assumption is the same as that
which prevailed in the early days of petrography; that is, rocks
may be divided into definite types, which are comparable to defi-
nite mineral or animal species. I do not for a moment suppose
that petrographers who have introduced these new names would
state that they believe this principle. I merely assert that many
of the numerous names are justified only if the principle be true.

Responsibility of introducing new names.—The petrographer
who introduces a new name for a rock assumes a responsibility
which ought to be incurred only after the most careful consider-
ation. Probably some of the new names which have been
recently introduced were necessary to the progress of the sci-
ence. That many of them were not, I venture to believe. One
who introduces a new name without the best of reasons for so
doing is hindering the advance of the science of petrography,
as well as occasioning loss of time and great inconvenience to
his fellow workers.

Statement of the problem.—All\ philosophical petrographers now
understand that between all kinds of rocks there are gradations —
from basic to acid, from coarsely granitic to glassy, from rich sodium

688 Ge Te VAIN RETESTED

rocks to rich potassium rocks, from massive lavas to tuffaceous
forms, from the freshest rocks to the most altered, from the old-
est rocks to the newest, from the igneous to the aqueous rocks ;
between all of the various forms of the sedimentary rocks. More-
over, many of the important stages of these gradations have
been noted. Still further, in one region the gradation from one
kind of rock is in one direction, and in another region is in a
different direction. For instance, here a granite grades into a
diorite; there grades into a syenite.

What shall be the criteria for naming rocks ? —These being the
facts, the question arises, what is the most important consider-
ation which shall determine whether or not a certain kind of
rock shall be assigned a name. It appears to me clear that the
most important consideration is the relative abundance of the rocks.
We must have names for the common things. It is well known
that certain of the multifarious kinds of rocks which have
been named are more abundant than others. Probably the
igneous rocks, which can be included under twenty names, com-
prise nine tenths or more of the mass of the igneous rocks.
It follows that a philosophical method of rock nomenclature
involves a knowledge of the relative abundance of the different
kinds of rocks.

However, it is not meant to imply that abundance shall be
the only consideration in the naming of rocks, but merely that it
shall be a fundamental one. While abundance ought to be the
first consideration, this idea must not be pushed to an extreme.
All rocks which must be assigned names will not be found in
equal abundance. Some rocks which do not have specific names
assigned to them may be more abundant than some other rocks
deserving of aname. For instance, olivine-gabbro may be more
abundant than some of the leucite rocks to which names must be
assigned. This but illustrates the well-known principle that
great variations due to secondary factors shall have weight in
proportion to their range, and that therefore they may have an
important modifying influence upon the application of the pri-
mary considerations.

THE NAMING OF ROCKS 689

Influence of rock classification on naming of rocks—The broad
question of rock classification I do not intend here to discuss.
However, it is necessary to mention some of the criteria which
are recognized in the classification"o0f rocks, since these are also
factors in the naming of rocks. By most petrographers, chem-
ical composition, mineral constituents, and rock textures and
structures are controlling considerations; but by different
petrographers these are placed in different orders of importance.
By some petrographers the distinction between plutonic and
volcanic rocks is given weight in classification. In making a
classification of rocks it is necessary to consider to what extent
the altered rocks shall be recognized, and whether such textural
terms as porphyry and obsidian shall be used in naming rock
species. Doubtless’ different petrographers would decide these
points in various ways.

Now the above factors, which are controlling considerations
in the classification of rocks, are of necessity secondary factors
in the naming of rocks. If a new rockibe found, which, in
regard to these secondary factors, is so different from any pre-
viously known rocks that it cannot be grouped with any of them
by the plan given below, it may be entitled to a new family
name, even if not abundant. :

But to return to the matter of abundance. After a system
of classification shall have been worked out by a petrographer,
he must decide what rocks shall have independent names. It is
my contention that at this point abundance shall be recognized
- as having the place of first importance. Names are tools by
which we avoid the circumlocutions of descriptions. Since, as
already shown, there are everywhere gradations between rocks,
not every phase of rock can have an independent name, else the
number of names would be infinite. Since fevery rock phase
cannot be assigned a name, what kinds shall be selected for
such names? Manifestly those which occur most abundantly.
For the common things, the common kinds of rocks, as a matter
of convenience, I repeat, we must have names.

As above noted, it has been supposed that a rock might be

590 CARAVAN Ss

designated as a type which has certain characteristics. _However,
the only method of nomenclature which is logical is that which
takes into account the fact of gradation and stages between all
rock varieties ; that types exist only as descriptions or specimens
selected by man, not by nature; but abundance is determined
by nature. All this 1s recognized in sthe scheme) given aw) sline
definite forms which are selected for names are those which are
abundant. This applies as well to the original forms of rocks
as to their altered varieties. Had the varieties of rocks inter-
mediate between those abundant kinds which have been given
names been the abundant ones, rather than those to which names
have been assigned, these would have been the rocks which
should have been given names, and which in all probability
would have been given names during the first period of the devel-
opment of the science of petrography.

How shall demands for exactness be met?—But the question
now arises as to how the demands of the petrographers for
exactness shall be met without introducing a new independent
name the moment a slightly different variety of rock is discov-
ered, however small its mass. This demand may be met by the
general application of special usages below given. The majority
of the abundant kinds of rocks were early assigned names. To
less abundant kinds of rocks intermediate between the more
abundant kinds, names compounded from the simple names may
be used; for example, granodiorite, trachydolerite, trachy-
andesite." To either the simple or the compound names may be
prefixed mineralogical qualifiers, thus further compounding them ;
for example, quartz-diorite, olivine-gabbro, analcite- basalt,
augite-trachydolerite. With these simple or compound names,
geographical qualifiers may be used. If the rock is so abundant
and definite as to require a specific name, the geographical
qualifier may be compounded with the more general name, as
Hellefors-diabase. If, however, the idea is exactly to designate
the rock occurring at a particular locality, without implying that

‘Italian petrographical sketches, V, by H S. WASHINGTON: JouR. GEOL., Vol.
V, 1897, pp. 365, 366.

THE NAMING OF ROCKS 691

it is so abundant and important as to require a name to enter
rock nomenclature, the geographical name may be used simply
as a qualifier, as, Duluth olivine-gabbro. This usage gives the
most exact discrimination without cumbering nomenclature with
a multitude of independent names. In any of the foregoing
classes of names the prefixes meta, apo, epi, schisto, gneisso,
or other terms may be inserted for the altered rocks.*

Under the plan proposed we shall have coérdinate simple
names of about the value which Rosenbusch has designated as
family for rocks which are the most abundant and important.
We shall have compound names for rocks intermediate between
the more abundant kinds. We shall have names with geological
qualifiers, either compounded: or not, as the case demands, for a
further refinement in discrimination. In any of these three
classes of names mineralogical qualifiers may be introduced as
an additional discrimination. For all of the previous classes we
shall have prefixes, with definite meanings, for the altered equiva-
lents of the diiterent rocks.

The method proposed is practically that of a binomial or tri-
nomial nomenclature. The fundamental names would be based
primarily upon abundance, and secondarily upon other factors.
The secondary names would be introduced under the same prin-
ciples.

Application of plan proposed.— How this plan can be worked
out may be illustrated by some cases from recently described
rocks. (1) Mordmarkite,? by Washington, is placed as equivalent
to mica-hornblende-quartz-syenite. The rock is therefore a syenite.
Assuming that this rock is sufficiently abundant so that it should
have a place in nomenclature, it may be called nordmarko-syenite.
In the same way, akerite3 (augitic quartz-syenite) may be called

«In another place (Metamorphism, Monograph, U.S. Geol. Surv.) I shall discuss
in detail the use of these terms. But in the present paper I do not wish to take up

the subject. Here I wish merely to suggest a method of handling the altered rocks,
rather than to discuss the details of its application.

?The petrographic province of Essex county, by H. 5S. WASHINGTON : JouR.
GEOL., Vol. VI, 1898, p. 799.

3Jour. GEOL., Vol. VI, p. 796.

692 C. R. VAN HISE

akero-syenite, if a new name is really necessary and preferable to
augitic quartz-syenite. (2) The trachydolerites, designated by
Washington as czmuinite, vulsinite, and toscanite,* may be called
cimino-trachydolerite, vulsino-trachydolerite, and toscano - trachydo-
lerite. Under this usage czmino, vulsino, and toscano, take the
same place with reference to the trachydolerites, that hellefors,
aasby, sirna, ottfdlls do to the diabases, as used by Rosenbusch
(see p. —-). Indeed, Washington himself in one place speaks
of pulaskite as pulaskitic syenite.? following the plan proposed this
would be pudlasko-syenite. (3) As an illustration of the use of
mineralogical terms compounded with names already com-
pounded may be given augite-toscano-trachydolerite. If desirable,
the order of the mineralogical and geographical parts of the
name may be reversed. For instance, the leucite-trachytes,
which Cross calls orendite and madupite,3 may be designated orendo-
leucite-trachyte and madupo-leucite-trachyte.

In all of these cases the geologist knows at once the general
character of the rocks referred to.) In the frst casevhe knows
the rocks are syenites; and, furthermore, that certain varieties
of syenites are so abundant and so definite in character as to
require a specific designation. In the second case he knows that
there is a kind of rock intermediate between the trachytes and
dolerites, and, if he knows what trachytes and dolerites are, he
has a very clear conception of this rock without any further
definition. He further knows that there are variations in the
character of the trachydolerites which occur at particular locali-
ties, and which, in the opinion of the author, are so abundant
and distinctive as to require specific designations. In the third
case he further knows at once from the name that certain varie-
ties of the Toscano-trachydolerite contain augite; and infers
that this variety is exceptional. He knows that the leucite-
trachytes have variations which are thought to be of sufficient
importance to require specific designation.

t Jour. GEOL., Vol. V, pp. 350-361.

2 Jour. GEOL., Vol. VI. p. 804.

3 Igneous rocks of the Leucite Hills and Pilot Butte, Wyo., by WHITMAN Cross:
Am. Jour. Sci., Vol. LV, 1897, pp. 138, 139.

THE NAMING OF ROCKS 693

It is also self-evident that the extreme refinement practiced
by Washington and Cross is in no respect lost by using the
nomenclature proposed, rather than assigning independent names
to particular varieties of rocks described. Indeed, the com-
pound names proposed give additional refinement to that attained
by independent names.

In giving the above illustrations I express no opinion as to
whether the various syenites, trachydolerites, and leucite-tra-
chytes are so abundant and important as to be worthy of specific
names. This is a matter for the petrographer to settle. I
merely use these terms as convenient illustrations as to how rock
nomenclature can be handled so as to serve the purposes of the
general geologist and the specialist, without throwing the sub-
ject of petrography into hopeless confusion.

Objection to long names.—The long terms resulting from the
plan, as, for instance, augite-toscano-trachydolerite, may be
objected to on account of their cumbersomeness and complexity.
However, it may be said that these names are simple as com-
pared with many of the names used in organic chemistry, and
furthermore that they are justified on precisely the ground
that the long names in organic chemistry are justified, that ts,
they are intelligible names. This is the fundamental point. The
present method of naming rocks is not intelligible even to pro-
fessional petrographers, and an unintelligible method can no
longer be tolerated. The method proposed is intelligible to
every geologist, whether a specialist in petrography or not, and
gives at once the information desired by the general geologist
and the extreme refinement demanded by the petrographer. The
plan proposed gives all the advantages of generic, specific, and
varietal names. If any petrographer can suggest a method of
naming rocks which will better satisfy the demand of the petrogra-
pher for exactness, and of the geologist for intelligibility, I shall
gladly favor such a plan rather than my own proposal.

Why petrographers have not generally followed plan outlineda.—
The plan suggested is so simple that the question immediately
arises as to why petrographers dealing with igneous rocks have

694 C.. R. VAN HISE

not followed it. Was there not some good reason for the intro-
duction during the past years of many new, independent names ?
The answer is, petrographers had not worked out any plan as to
the naming of rocks, and to assign a new name for each new
variety of rock was the easiest way out of the difficulty, although
it was disastrous so far as their fellow workers were concerned.
Then the honor of giving a new name to rock nomenclature
doubtless had a too important effect. Furthermore, many of
the petrographers still held, in a subconscious way, to the old
notion of rock types, not yet having grasped the idea of general
gradation.

Plan followed in case of sedimentary rocks—That the scheme
proposed is practicable is shown by the sedimentary rocks, where
it has been substantially followed, although as a matter of neces-
sity rather than a conscious system. In the sedimentary rocks,
from the first, gradations were recognized, and hence the tend-
ency to give each variety a new name never got any headway.
To illustrate the application of the scheme to the sedimentary
rocks, we may take the sandstones. There is an almost infinite
variety of sandstones, but it so happens that petrographers have
not been directing their energies to the minute discriminations
of their variations, and we have nota dozen or score of different
names for the different kinds of sandstone. Yet the sandstones
of different localities are discriminated and recognized as dif-
ferent from one another by attaching the names of the localities at
which the rocks occur to the name, and thus discriminating each
rock from all others. For instance, in Wisconsin a peculiar sand-
stone occurring locally is called the Madison sandstone. From
this designation the general geologist at once knows that this
formation has the general characters of the rocks which have
been called sandstone, and he will not go further. But if he is
interested in the Madison district for some reason, scientific,
economic, or otherwise, he may go further and learn the pecul-
larities of the particular sandstone which is found at Madi-
son.

By this method the sedimentary formations are discriminated |

THE NAMING OF ROCKS 695

the world over. However numerous the names for the sedi-
mentary rocks may be in the future, the method still must be
used, for however fine the discriminations resulting from such
names, there will be variations from the meanings assigned to
these names, and thus the local names are necessary.

Ln exceptional cases plan followed with igneous rocks.—The sim-
ple method proposed of designating the slightly different varie-
ties of igneous rocks from one another, without throwing their
nomenclature into hopeless confusion, has already been followed
in several cases.

A notable instance is the term Andendiorite proposed by
Stelzner* for a particular rock which has the general characters of
a diorite, but which in some respects differs from ordinary diorite,
and occurs in the Andes. A geologist who does not care to go
into the detailed petrography of the region notes at once that in
the Andes is a rock which has the general characters of the dio-
rites, but which in some respects differs from the ordinary kind.
He also at once knows that in the Andes is a rock which is dif-
ferent from the ordinary diorites, but which is allied to them.
If in his investigative work he wishes to know exactly the
meaning of the modifying term, he can do so by reading Stelz-
ner’s paper, or by obtaining specimens and an analysis of the
rock. Inthe case of Andendiorite, the name has been also used
as a new specific name, an dapplied by Iwasaki? to a somewhat
similar rock in Japan. Toa certain degree this shows how the
method may be made to work out in practice in reference to the
igneous rocks. When here and there other rocks are discovered
similar or almost identical with the Andendiorite, and this variety
of rock, asa result of these investigations, is found to be so
abundant and so definite in its characters as to demand a specific
name, the original word Andendiorite may be used for this pur-
pose, or, better, a new specific name may be coined for it, and
the rock be placed in the scheme of rock nomenclature.

Rosenbusch has used the method of geographical qualifiers

* A. STELZNER: Geologie und Palaontologie, von Argentina, p. 213.

? Andendiorite in Japan, by C. IWASAKI: JouR. GEOL., Vol. V. 1897, pp. 821-824.

696 C. R. VAN HISE

in a number o finstances precisely as proposed, for discriminat-
ing rocks. For example, he describes /elleforsdiabas, aasby-
diabas, sarnadiabas, ottfjallsdiabas.* Had some _ petrographers
described these rocks perhaps we would have had four additional,
independent names to remember, the value of which we would
know absolutely nothing of, without any suggestion whatever as
to the family, in Rosenbusch’s sense, to which these new rocks
belong.

The method proposed has unconsciously been followed to
some extent, by the’ United “States |Geolopgical’ Survey that
organization has recognized that a sufficient number of inde-
pendent names could not and should not be coined to designate
every variety of rock. It has practically, if not by definition,
recognized the endless variation and gradation throughout rock
formations, by providing that aqueous and metamorphic formations
alike should be given local names; for example, Chicopee-shale,
Floosac-scehist), Becket-sneiss, eter.) Unis use of local eimamies
has furnished a more accurate method of discrimination than
could be afforded by independent names. Moreover, only rocks
which are present in some quantity have been given formation
names. Thus, by practice at least, the idea of abundance as a
factor in the naming of rocks has been recognized.

Suggestion to petrographers who have introduced new names.—In
this connection it may be suggested that petrographers who have
recently introduced new independent names would perform a
service to geologists who are not petrographers, and to many
other petrographers, by giving in subsequent papers equivalent
names on the basis of the plan above advocated, to the special
rocks to which they have given names. If this be done, the
relative merits of the two plans will be tested. Within a short
time it will be seen whether geologists and petrographers use
the independent names or the more general names compounded
with geographical and mineralogical terms. Where a new inde-
pendent name was really needed, and performs a service in the

* Mikroskopische physiographie, II, Massige Gesteine, H. ROSENBUSCH; S. 219-220.

? Holyoke folio No. 50, Geological Atlas of the United States.

LHE NAMING OFF ROCKS 697

advancement of science, it will be sure to be retained. If it
drops out of use, its proposal was premature.

Summary of advantages of proposal—In conclusion, some of
the advantages of the foregoing plan may be summarized:

1. The plan proposed serves all the purposes of nomencla-
ture, from names of a general character to those giving the
most minute discriminations. It has the advantage of grouping
different varieties of rocks under terms, the general meaning of
which is known to all. In the matter of nice discrimination it
far surpasses the plan of independent new names for new vari-
eties of rocks. It permits at once any difference in the charac-
ter of a rock, however slight, to be discriminated, and it permits
the growth of petrography by the grouping of the allied varieties
together under a new specific name so soon as they shall have
been found so abundant, so peculiar, or so important as to
demand such a name. The professional petrographer will thus
have a much more convenient and elastic nomenclature for
describing rocks than he has at present. He may ignore minor
differences between rocks in one sentence, and in the next sen-
tence deal with the most refined differences between them. Thus
the plan advocated meets both the demands of the geologist and
of the specialist in petrography.

2. The plan proposed puts the available information of
petrography in such shape that some master mind in the future
may reduce the subject to a science. The present scheme of
rock nomenclature makes it impossible for any person to get the
facts clearly before his mind in such a way that they can be
handled. The provisional scheme proposed accomplishes this
end. If it be generally followed by petrographers, it is probable
that within a few years it will be possible to propose a definite
scheme of rock nomenclature, the terms of which correspond
roughly to genus, species, and variety in biology.

3. It is believed, if once rock nomenclature be placed upon
a reasonable basis, that this will be a great step toward the
establishment of a satisfactory scheme of rock classification.

4. Under the plan suggested it will be easy for the student

698 C. R. VAN HISE

to get definite notions of the common kinds of rocks. Having
this knowledge, he knows without explanation the meaning
which is to be attached to a name compounded of two of them.
He knows without a moment’s reflection the meaning of a
mineralogical qualifier prefixed to a noun. He knows that a
geographical qualifier means the particular variety of rock which
occurs in a certain district. Thus it will be possible for a student
to gain a comprehensive knowledge of the chief kinds of rocks
at a very early stage of work, and to supplement his general
knowledge by details as his work advances.

5. A further advantage of the foregoing plan will be that
many of the earliest rock names proposed will be retained,
although some may be abandoned. The reason why so many
of the old names will be retained under the plan proposed is that
many of the abundant rocks were first found; for, as already
noted, while the petrographers supposed they were following the
plan of naming rocks on the basis of types, they were largely
following the plan of naming rocks on the basis of abundance.

6. Still another of the manifest advantages of the plan is that
it throws the emphasis on the proper thing; it calls attention to
the common, not to the exceptional, rocks. Many petrographers,
in discussing the rocks of an area, describe with the utmost
particularity the minute characteristics which are peculiar to the
exceptional rocks of the district or region, and say comparatively
little of the common rocks which compose the great mass of the
rocks of the area. Of course, there is some justification for this,
in that the characters of the common forms are known. But all
papers describing the geology of a region should be so framed
as to give a clear conception of the common kinds of rocks
which are preponderant, and indicate that the exceptional things
described in such detail are only so described because of their
peculiarities. To the reader in some way should be conveyed
the idea of the relative abundance of the rocks. The error of
emphasizing the exceptional and overlooking the common phe-
nomena has been one of the most pernicious mistakes which runs
throughout geological papers and text-books. For instance,

THE NAMING OF ROCKS 699

many pages in a text-book are given to a discussion of earth-
quakes, and only a small fraction of that space is given to the
vastly more significant, slow earth movements which occur with-
out earthquakes or with earthquakes as secondary phenomena.
7. Finally, the foregoing plan has one further advantage. It
emphasizes a great law of nature, the law of gradation-—the prin-
ciple that ultimately there is no such thing as an absolute type.
In this respect, petrography, if it will but use its opportunity,
has an advantage over any other subject. In biology there have
once been gradations between species, between families, between
classes. Many of these gradations have been destroyed in the
course of evolutionary processes. However, in petrography all
of the gradations yet persist, and thus it furnishes the best illus-
tration of the principle of gradation, a fundamental principle of
nature.
C. R. Van HIseE.

Mapison, WIs.,
November 1899.

2 DILRORIEL

A PROPOSED INTERNATIONAL JOURNAL OF PETROLOGY.— The
committee appointed by the Seventh International Congress of
Geologists to consider plans for the establishment of an Inter-
national Journal of Petrology has chosen Professor F’. Becke of
Vienna, well known as the editor of Tschermak’s Mittheilungen,
President of the Committee, and has taken the first steps toward
the organization of such a journal. It has been proposed that
articles appearing in it shall be printed in French, German, or
English at the option of the author.

While primarily intended for the publication of reviews and
abstracts of all petrographical papers wherever published, it is
suggested that it may include also articles which shall appear in it
for the first time. The carrying out of this must depend upon
the financial support the journal receives.

The journal is to be managed by a committee appointed by
the International Congress of Geologists, the committee to select
an editor who shall have two assistants ; the editor and assistants
to receive salaries for their services.

The desirability of having one source, thoroughly up to date,
to which to turn for information concerning all matters pub-
lished on petrology is self-evident to all attempting to keep
abreast with the rapid advance of this science. One has only
to observe what a great impulse to the science of mineralogy
has been given by the establishment of Groth’s Zeitschrift fir
Krystallograplie, to be convinced of the usefulness and con-
venience of such a journal.

The necessity of forecasting as correctly as possible the
financial support obtainable for such a journal has suggested to
the American members of the committee the plan of calling
attention to the enterprise and of inviting all interested in its
success to communicate to either of them such suggestions or
information as may aid in estimating the amount of annual

700

EDITORIAL 701

subscriptions or contributions that may be obtained from this
country.

It is expected that the chief support will come from individual
subscriptions and from university and public libraries, but it may
be possible to obtain assistance, in the first years of the under-

taking at least, from other sources. J. P. IppINGs;
LE... V: -PIRsson;
Members of the Committee for America.

Do Strate Surveys Pay? The question has often heen asked,
and in the coming legislative season probably will be asked many times.
An answer is usually desired which deals with dollars and cents, but,
perhaps, a partial answer may be given by noting the sort of requests
for miscellaneous information which consume a not unimportant por-
tion of the time of survey officers.

For illustration, the requests of a single day in the office of one of
the smaller surveys may be noted. Two came in the morning mail.
The first was from a professor in one of the smaller colleges, asking
for twenty copies of a certain pamphlet to use in the class room. The
second was from a consulting chemist, retained by some eastern cap-
italist to investigate the advisability of establishing an important
manufacturing plant in the state. He wished to know the amount,
quality, and average cost of certain ores which were being mined there,
and the probability of larger quantities being mined. A third request
was made in person, by the engineer in charge of locating an impor-
tant line of railway. He wished a report upon the mineral resources
of all kinds along the proposed line. <A fourth request came in the
afternoon mail. It was from a high-school teacher, who wished for a
certain report to use in teaching. The last request was from a reporter,
sent to secure an interview relative to certain reputed iron deposits
that the local papers of a certain section of the state were making
much of. ‘The city editor of a big daily wished to know whether there
was any iron there. If so, how much. What was its quality, and what
the chances of securing its development if proper publicity were given
the matter. He wanted “facts which could be relied on,” and so he
sent to the survey.

All these requests were attended to in detail, and the tired official
wondered when he was to get time to write, revise, and print the
report on the year’s field work. EE b,

SUMMARIES OF CURRENT NORTH AMERICAN PRE-
CAMBRIAN LITERATURE.’

Davis,? in connection with an account of the Triassic formation of
Connecticut, maps the boundary between the Triassic and crystalline
rocks to the east and west. ‘The prevailing monoclinal faulted struc-
ture in the Triassic involves a similar structure in the crystallines below,
and it is believed that the structure observed in the Triassic is due to
the slipping of large slabs of the crystalline rocks and the overlying
Triassic rocks, in such way that each slab was elevated with reference
to the slab next to the west, or, lowered with reference to the one next
to the east. The explanation of the cause of the faulted structure is
the same as that offered in a previous paper.?

Merrill* gives a general account of the geology of the crystalline
rocks of southeastern New York.

The crystalline rocks lie on the east of the Hudson River, in
New York, Westchester, Putnam, and Dutchess counties, whence they
extend into Connecticut; and on the west of the river, in Orange and
Rockland counties, whence they extend southwesterly into New Jersey.
The lowest member is a coarse hornblende-granite which forms the
central mass of the range of mountains known as the Highlands of the
Hudson, and, in their highest peak, Breakneck Mountain, is exposed
through a vertical height of nearly 1200 feet. Other granites, nearly
free from hornblende, occur in subordinate masses. ‘The granites are
probably igneous and of great age. On their flanks are banded
gneisses, the Fordham Gneiss, consisting chiefly of quartz and ortho-
clase, with biotite and hornblende, and containing numerous beds of
magnetic iron-ore. The gneisses on the south side of the Highlands
extend through Westchester county in a series of folds with south-
westerly trend, and on the northern slope of the Highlands, at several

t Continued from p. 425, Vol. VII, Jour. GEOL.

2The Triassic formation of Connecticut, by Wm. M. Davis: Eighteenth Ann.
Rept. U.S. Geol. Surv., Part II, 1898, pp. 1-192. With geological map.

3The Structure of the Triassic Formation of the Connecticut Valley, by Wm.
Morris Davis: Seventh Ann. Rept. U.S. Geol. Survey, 1888.

4The geology of the crystalline rocks of southeastern New York, by F. J. H.
MERRILL: Report of the New York State Museum, 1896, pp. 21-44.

702

CURRENT PRE-CAMBRIAN LITERATURE 703

places in Dutchess county, are overlain unconformably by quartzites,
which are believed to be of Cambrian age.

Ries* describes the geology of Orange county, New York. Pre-
Cambrian rocks form the Highland region in the eastern part of the
county, the northwestern side of Bellvale Mountain, and a series of
rounded knob-like hills extending from Sugar Loaf village to Newburgh.
They comprise gneiss, at times massive and resembling granite and
limestone. The crystalline rocks are folded and faulted, the folds
plunging frequently to the northeast.

In the south-central part of the county is found an area of white and
blue limestone, which continues south into New Jersey. ‘The white
limestone is found in New Jersey to contain fossils of Cambrian age.
Exposures are found east of the road, 114 miles west-southwest of Pine
Island station, which show the passage of the blue into the white lime-
stone. Other, similar areas of limestone are found to the northeast.

Limestones interbedded with the gneisses are found at Popolopen
Pond, and again at Fort Montgomery.

Wolff and Brooks’ present a final discussion of the age of the
Franklin white limestone, of Sussex County, N. J. The pre-Cambrian
age of the white limestone is believed to be shown by the following facts :

The supposed cases of interbedding of the white limestone and the
Cambrian quartzite are found to be due to faulting, or to peculiar con-
ditions of deposition. On the other hand, while it is difficult to prove
that the white limestone and pre-Cambrian gneiss are actually inter-
bedded, narrow bands of the true gneiss do occur within the white
limestone belt, and seem to be an integral part of the series.

The granite occurring in the area isintrusive in the white limestone,
and the nature of the contacts of the granite and the Cambrian quartz-
ite indicates that the intrusion was prior to the deposition of the Cam-
brian quartzite and blue limestone. While the intrusion of the granite
has caused local metamorphism of the white limestone, it is believed
that the crystallization of the limestone antedated the granitic intru-
sion, and was contemporaneous with the crystallization of the gneisses
in their present form.

* Geology of Orange county, by HEINRICH RIEs: Forty-ninth Ann. Rept. of N. Y.
State Museum, for 1895, Vol. II, 1898, pp. 395-475. With geological map.

2 The age of the Franklin White limestone of Sussex County, N. J., by J. E. WOLFF
and A. H. Brooks: Eighteenth Ann. Rept. U.S. Geol. Surv., Part II, 1898, pp. 425—-
457. With geological map.

704 C.K LEIGH,

The structural relations of the three belts of Cambrian blue lime-
stone with the gneiss and white limestone are such as to indicate uncon-
formity. Along the normal contacts of the blue and white limestone
the quartzite intervenes between the two. The bedding of the blue
limestone and underlying quartzite is everywhere conformable, while
the dip of the foliation of the white limestone and the gneisses is dis-
cordant with this bedding.

Isolated patches of Cambrian quartzite are found within the white
limestone area. In one place a crevice in the white limestone is filled
with the Cambrian quartzite containing undoubted pebbles of the
white limestone.

Comment.—The results above presented bear evidence of close and
careful field study. The pre-Cambrian age of the white limestone is
clearly proven, thus satisfactorily disposing of a much disputed question.

There now remains the question of the origin of the gneisses. In
this connection attention may again be called to the marked similarity
of the limestones and associated. gneisses of the New Jersey area, to the
pre-Cambrian limestones and associated gneisses of the Adirondack and
Original Laurentian districts to the north. In a general way it would
seem that the story worked out for one of the districts may perhaps
apply to the others.

Weidman* describes the pre-Cambrian igneous rocks of the Utley,
Berlin, and Waushara areas, in the Fox River Valley of Wisconsin. They
range from volcanic flows to masses of deep-seated origin, with corre-
sponding textures. The rock of the Utley area is a metarhyolite, at
Berlin a rhyolite-gneiss, and in the Waushara area a granite. Analyses
of the rocks of the three areas show a close similarity in chemical
composition, and it is believed that the rocks represent phases of a
single parent magma. ‘The rocks have been metamorphosed to differ-
ent degrees, and the results of the metamorphism, particularly of the
feldspars, are described in detail.

The crystalline rocks are unconformably overlain by flat-lying Pots-
dam and Ordovician sediments. From their similarity in composition
to the Baraboo volcanics, which are considered to be of Keweenawan
age, it is believed that they belong to the same province, and are there-
fore of Keweenawan age.

*A contribution to the geology of the pre-Cambrian rocks of the Fox River Val-
ley, Wis., by SAMUEL WEIDMAN: Bull. Wis. Geol. & Nat. Hist. Surv., No. III, 1898,
pp: 63.

CURRENT PRE-CAMBRIAN LITERATURE 705

Norton,’ in a description of the artesian wells of Iowa, discusses the
attitude of the Algonkian floor. In the northwestern part of the state
the Algonkian outcrops as the Sioux quartzite. From here it sinks
rapidly to the south and east, and is discovered near the area of its
outcrop only by the steep wells at Sioux City, Hull, and Le Mars. In
the east-central part of Iowa is a slight elevation of the Algonkian
floor, disclosed by the artesian well at Cedar Rapids. In Wisconsin
the Algonkian outcrops as the Baraboo quartzite, a rock similar to the
Sioux quartzite. From this outcrop the Algonkian sinks gently to the
southwest, as it is reached by the drill at Lansing, Iowa. At no other
place in Iowa has the drill gone deep enough to reach the crystalline
rocks.

Comment.—The connection of the crystallines reached by the drill
with the Algonkian outcrops of Iowa and Wisconsin is conjectural, and
perhaps it would be better not to assume that such crystallines are all
Algonkian. However, the observations are of interest as showing the
attitude of the ancient crystalline floor, whether Archean or Algonkian.

Beyer? maps and describes the part of the Sioux quartzite forma-
tion exposed northeast of Sioux Falls in sections 10, 11, 14, 15, 22,
and 23, T. 102 N., R. 48 W., South Dakota. The quartzite dips from
3° to 7° to the southwest. An accurate estimate of the thickness may
not be given, but 1500 feet is a liberal one.

Slate is exposed in the area in isolated outcrops, but never in con-
tact with the quartzite. In composition it corresponds very closely to
the quartz-slate of Irving and Van Hise.’ Intruding the slate are dia-
base dikes, which have followed the bedding.

The relations of the slates and quartzites cannot here be ascer-
tained. However, from the relations of the two outside of the area it
is believed that the slates are the upward continuation of the quartzite,
and that they have been removed in large part.

The age of the Sioux quartzite is believed to be pre-Cretaceous.
Its reference to the Huronian may be supported by the following facts :
The lithological characters of the quartzite are identical with those of

Artesian wells of Iowa, by W. H. Norton: Geol. Survey of Iowa, Vol. VI, 1897
(The Algokian, pp. 139-140).

2 The Sioux quartzite, and certain associated rocks, by S. W. BEYER: lowa Geol.
Survey, Vol. VI, 1897, pp. 69-112.

3 The Penokee iron-bearing series, by R. D. InvinG and C. R. VAN Hise: Tenth
Annual Rept. U. S. Geol. Survey, 1890, p. 370 et seq.

706 C. K. LEITH

the Baraboo quartzite in Wisconsin, which has been referred by Irving
and Van Hisetothe Huronian. The diabase intruding the slate, supposed
to be the upward continuation of the quartzite, is strikingly similar to
intrusives which are peculiar to the Huronian in the Lake Superior region.

Frazer* sketches the geology of an area in the vicinity of Galena,
in the Northern Black Hills of South Dakota. Mica-schists, thought
to be upper members of the Archean, are found striking northeast-
southwest, and dipping at angles from 38° to 85°. ‘They are gen-
erally micaceous and coarse-grained, but vary greatly, sometimes
passing into nacrite- or hydromica-schist, and sometimes, though more
rarely, assuming a heavily bedded character reminding one of gneiss.

Todd? reports on a section across the Black Hills from Rapid City
westward. The alternating slate and quartzite beds of the Algonkian
were found to be folded in a most intricate fashion. A number of the
folds were worked out. In most cases the lamination and stratification
seem to correspond in direction.

Comment.—Vhe last observation differs from one made by Van
Hise, who, as a result of work done in 1890, concluded that the
prominent foliation of the Black Hills is independent ot the bedding,
and as a rule cuts across it.

Griswold? describes the geology of Helena, Montana, and vicinity,

Middle Cambrian, or Flathead, quartzite forms an important part
of the ridge stretching from Helena southeast to Montana City, and
northwest, west, and south around Mount Helena. The sedimentary
rocks underlying most of the area of the city, on the north side of
this Cambrian quartzite, are classed as Algonkian. The Algonkian
rocks vary from clay-slates to micaceous, sandy, or calcareous slates,
which often become quartzites or limestones. The Algonkian slates
seem to conform to the overlying strata in the dip of their beds. As
there are many small folds, it is difficult to determine the thickness ;
5000 feet does not seem too large a total.

Gilbert* maps and describes the geology of the Pueblo quadrangle,

* Notes on the Northern Black Hills of South Dakota, by PERSIFOR FRAZER: Trans.
Am. Inst. Min. Engineers, Vol. XX VII, 1898, pp. 204-228.

? Section along Rapid Greek from Rapid City westward, by J. E. Topp: South
Dakota Geol. Survey, Bull. No. 2, 1898, pp. 27-40.

3 The geology of Helena, Montana, and vicinity, by L. S. GRIswoLD: Journal of
the Association of Engineering Societies, Vol. XX, 1898, pp. 1-18.

‘Geol. Atlas of the U. 5., Pueblo folio, No. 36, by G. K. GILBERT: U. S. Geol.
Survey, Washington, 1897.

CURRENT PRE-CAMBRIAN LITERATURE {07

including part of Pueblo county and the southeast corner of Fre-
mont county, Colorado. Archean rocks occupy two small tractsin the
southwestern part of the quadrangle. The more abundant kinds of
Archean rocks are mica-schist, mica-gneiss, and granite. ‘The schists
and gneisses strike north to northwest, and are nearly vertical. Their
origin is not known. The granite is intrusive in the schists and
gneisses.

The Archean rocks are overlain unconformably by Paleozoic and
Mesozoic sediments.

Lakes’ sketches the geology of the Gunnison gold belt in Gunni-
son county, Col., from the Cebolla River on the west to the head of
Taylor Park and the Sawatch range on the east. The northern part of
area is included in the granitic system of the Sawatch range. The
southern part is occupied by schists and gneisses, underlain by coarse
massive granite. The schists and gneisses are of pre-Cambrian age,
but whether Algonkian or older has not been determined. The con-
tact of the schists and gneisses with the underlying granite is an erup-
tive one, the granite containing fragments of the schist, giving the
impression that the schists had been floated up on an underlying
molten or semi-molten sea of granite. Cutting the schists are occa-
sional dikes of diabase and possibly basalt and andesite, and resting on
the eroded edges of the schists are various later overflows of andesitic
breccia, rhyolite, trachyte, and basalt.

Aguilera? gives a synopsis of the geology of Mexico. The most
ancient, or Azoic, rocks are granites, gneisses, and schists, presenting
many variations. They extend lengthwise along the Pacific coast,
forming a narrow band, interrupted in places, and sending rami-
fications toward the central part of the country, in some places
almost to the eastern coast. ‘They occupy the southern part of the
state of Puebla, a part of the Sierra Madre Mountains in Chiapas,
and extensive portions of Oaxaca and Guerrero; they are found also
in Zacatecas, around Fresnilo; in Guanajuato, in the vicinity of the
capital; in Sinaloa, around the crests of the Sierra Madre ; in Sonora,
in its northwestern and western parts; in lower California, where

t Sketch of a portion of the Gunnison gold belt, including the Vulcan and Mam-
moth Chimney mines, by ARTHUR Lakes: Trans. Am. Inst. Min. Engineers, Vol.
XXVI, 1897, pp. 440-448.

2 Sinopsis de Geologia Mexicana, by Jos—E C. AGUILERA: Bol. del Inst. Geol. de
México, Nums. 4, 5, & 6, 1897, Part II, pp. 189-250. With geol. maps.

708 C. K. LEITH

they constitute the central Cordilleran axis of the peninsula; in Vera
Cruz, in its western region, limited by Puebla, in the canton of Zon-
gclica.

In the southern part of Puebla, and in Guerrero and Oaxaca, where
the greater part of the exposures occur, the sequence is as follows, from
the base up: (a) Porphyritic gneiss, similar to augen-gneiss, at the
base losing its lamination and passing into a kind of granite. (4)
Phyllite-gneiss, resting upon, and grading below into preceding beds.
(c) Very abundant mica-schist, in some places garnetiferous, and in
perfect conformity with the phyllite-gneisses. (d) Phyllites, very
argillaceous in the upper part, and showing gradual diminution in the
proportion of clay toward the base. In accordance with this change
of composition, the structure varies from perfectly schistose to lam-
inated, and finally to stratiform.

After the deposition of the argillaceous phyllites, and before the
termination of the Paleozoic, there have occurred numerous eruptions,
in order of age as follows: Granite-gneiss, granite, granulite, horn-
blende granite, pegmatite, greisen, and diorite.

Comment.— The ancient rocks are mapped as Azoic, and in the text
are described as Archean and Primitive, so that these three terms are
used in the same sense, to cover all rocks below the Paleozoic. ‘The
pre-Paleozoic rocks are both sedimentary and igneous, and not improb-
ably may represent the Algonkian as well as the Basement Complex.

Cokes Erin.

MaopiIson, WIs.

I.-CAAIATAS

Geology of the Yellowstone National Park. Part II]. Descriptive
Geology, Petrography, and Paleontology. By ARNOLD HaGugE,
(cee lip pinesy Welty WV BED. C.D. Warcorn Gal Girny,
T. W. Stanton, and F. H. Know.ton. Washington: Gov-
ernment) Printing Office, 1899. Pp. xvili-=- 893, 121 plates
and 4 figures. Monograph XXXII of the United States
Geological Survey.

This compendious monograph is about equally divided between pet-
rography and paleontology, having about 440 pages of text in each
division, and of the 121 plates 62 are given to fossils, and 59 and the
four figures to petrography and geology. Of the fourteen chapters
Iddings furnished seven* on the petrography, Iddings and Weed
two on the geology, Weed and Hague each one on the geology.
Walcott’s work on the Cambrian fossils and Girty’s on the Devonian and
Carboniferous go into onechapter. Stanton furnishes one on the Meso-
zoic fossils and Knowlton one on paleobotany.

The first chapter, by Iddings and Weed, is on the descriptive geol-
ogy of the Gallatin Mountains, which mountains extend eighteen miles
within the boundary of the park. The diversity of the geological fea-
tures in this area is remarkable. The sedimentary rocks begin with the
Cambrian and range through the Silurian, Devonian, Carboniferous,
and Juratrias into the Laramie division of the Upper Cretaceous. Cut-
ting through the sedimentary series are intrusions of igneous masses in
the form of laccoliths, sheets, and dikes. The sedimentary rocks are
slightly folded and strongly faulted. Extensive erosion has exposed
large areas of the rocks in their structural relations. To still add to
the diversity, the surface has been glaciated.

The second chapter describes the intrusive rocks of the Gallatin
Mountains. These consist mainly of fine-grained, aphanitic masses,
mostly porphyritic and andesitic in character. The Indian Creek lac-
colith is hornblende-mica-andesite-porphyry. The Bighorn Pass sheet

709

710 REVIEWS

consists of kersantite of complex composition; the Gray Mountain
mass and connected sheets consist of andesite and andesite-porphyries.
The Mount Holmes bysmalith, Gallatin River laccolith, and the Bun-
sen Peak mass are composed of dacite-porphyry.

Chapter three deals with Electric Peak and Sepulchre Mountain,
which are described as parts of a Tertiary volcano faulted across the
neck with a vertical throw of more than 5000 feet. The deeper parts
of the volcano consist of sedimentary strata cut by dikes, sheets, and
the stock or conduit of the volcano. The ejected breccia and lava
flows, along with the upper portion of the conduit, make up Sepulchre
Mountain. The andesitic lavas of Sepulchre Mountain change to
diorites and porphyries in Electric Peak. Rocks with the same chemi-
cal composition in one place crystallize into diorites and in another
place form andesites. Both types are illustrated by photomicrographs
and photographs. Maps and section illustrate fully the relations of
the different rocks.

The northern end of the Teton range, which occurs in the southern
part of the park, is described at length in the next chapter. This range
is made up of a nucleus of crystalline schists and gneisses, which are
overlain by flexed and faulted Paleozoic and Mesozoic strata. ‘The
eroded edges of these old sedimentary rocks were covered witb vol-
canic basic breccias and after another period of erosion an extensive
outflow of acidic lava covered the whole area and still conceals the north-
ern extremity of the Teton Mountain.

Mr. Hague, in chapter five, describes the irregular diversified moun-
tainous area known as Huckleberry Mountain and Big Game Ridge. It
lies in the southern part of the park and in the Forest reservation and
consists of a number of northwest-southeast ridges, composed mostly of
Mesozoic rocks. ‘The Cretaceous sandstones are the prevailing rocks,
but small areas of older strata are exposed. ‘The rhyolites of the park
plateau abut against the slopes of the upturned edges. Besides Huckle-
berry Mountain and Big Game Ridge, there are other elevations known
as Wildcat Peak, Bobcat Ridge, Chicken Ridge, and Two Ocean
Plateau. The principal igneous rocks in the area are dacites, sur-
rounded by apparently younger rhyolite. In the gorge of the Snake
River the Madison limestones, Teton sandstones, Ellis limestones, and
shales are exposed. ‘The Snake River hot springs occur near the con-
tact of the rhyolite with the limestones. The travertine deposits
around the springs resemble those around the Mammoth Hot Springs

REVIEWS 711

and the lime is derived from the Madison limestone. The Laramie
strata are exposed near the base of Pinyon Peak, as shown by the char-
acteristic Wolverine flora. The conglomerate of Pinyon Peak is prok-
ably Eocene, as it underlies the basic breccias of the Absaroka range and
overlies unconformably the Laramie sandstones. Outlet Canyon, the
picturesque gorge cut through Chicken Ridge, at one time served as an
outlet into Snake River for the waters of Yellowstone Lake. The Yel-
lowstone Canyon now furnishes an outlet for these waters into the
Atlantic, instead of into the Pacific. Two Ocean Plateau, which rises
10,000 feet above the sea level, forms a part of the Absaroka Range.
It is made up of volcanic breccias and tuffs.

Chapter six describes the southern end of the Snowy range, which
forms the northeast corner of the park. It consists of a broad core of
crystalline rocks, bordered by Paleozoic rocks, which dip away from the
crystalline axis. Detailed sections of the Paleozoic sedimentary rocks
are given, but the igneous rocks are described in other chapters.

Chapter seven is especially interesting to petrologists, as it describes
in detail the structural features and petrographic characteristics of a
dissected volcano in the Crandall Creek basin. It lies on the border of
the park forest reservation and east of the park proper. ‘The great
value to petrology lies in the clear delineation of the inside of a volcano,
and in giving additional field evidence of the gradation of coarsely
crystalline so-called Plutonic rocks into the glassy eruptives. ‘The
coarsely crystalline gabbros and diorites, with smaller bodies of granite,
exposed for a height of 3000 feet, are plainly seen to have been intruded
intoavast accumulation of basaltic tuffand scoriaceous breccia. From this
coarsely crystalline mass as a center, dikes of fine-grained rock pene-
trate the surrounding lavas in all directions, the dike rocks becoming
fine-grained rapidly as they leave the once heated core. They form a
network of branches which connect the outlying aphanitic and character-
istically volcanic rocks with the more crystalline dikes near the core
which finally merge into the granular body of the gabbro and dorite.”
The whole forms one complex network so closely interwoven that the
gabbros of the core are as truly volcanic as the glasses on the surface.
The volcano has built itself upon a ridge of eroded Paleozoic rocks,
and beneath the volcano are remnants of Eocene breccias and lava
flows.

The next chapter treats of the Absaroka range which consists mainly
of volcanic breccias with smaller quantities of massive flows. It contains

712 REVIEWS

an account of their field occurrence and distribution, and a systematic
description of their mineralogical composition and characteristics. The
oldest rocks occur at the north end and consist of acid breccias found
in remnants underlying early basic breccias. The former consist mainly
of hornblende-andesite and hornblende-mica-andesite. The basic
breccias consist of pyroxene-andesite, passing upward into basalt. Upon
these were thrown other acid breccias, similar in composition and
appearance to the earlier ones. These grade upwards into later basic
breccia, consisting of andesites with less basalt than occurs with the earlier
flows. ‘This last basic breccia forms the southern portion of the range
within the park and also the Two Ocean Plateau. Remnants of surface
flows of massive andesite form the summits of Mt. Stevenson, Mt.
Doane, Colter Peak, and several prominent mountains south of Sylvan
Pass.

Chapters nine, ten, and eleven discuss different classes of the vol-
canic rocks. ‘The Absarokite-Shoshonite-Banakite series consists of
certain basaltic and other rocks associated with andesitic breccias
and basalt flows which have considerable orthoclase and a compar-
atively high percentage of potash. ‘They occur as lava flows and dikes
in various localities. They have been classified according to their
chemical and mineral composition.

The rhyolites in the park are almost wholly extrusive lavas of
uniform chemical composition, but differing widely in color, texture,
and megascopic habit. ‘The mode of occurrence, and the microscopic
features of phenocrysts, spherulites, lithophysae, are described in
detail, and beautifully illustrated. The modifications of crystallization,
lamination and the formation of pumice are referred to heterogeneity
of the molten magma, especially with reference to the amount of vapors
contained in it. In some places basalt appears to have been inclosed
and partly fused by the rhyolite.

The recent basalts are distinguished from the early brecciated ones
by being ophitic and non-porphyritic. They overlie the rhyolite in
most cases, but in some places they occur beneath it, and in some
places between the older and younger sheets of rhyolite.

With chapter twelve begins the paleontologic part of the work-
The Director of the survey describes the Cambrian fauna from
which twenty-one species have been obtained. Several of these are new,
and are here described and illustrated for the first time. No fossils of
undoubted Silurian age have been obtained. The Devonian is

REVIEWS 7s

represented in the Three Forks limestone. A varied but wholly Lower
Carboniferous fauna has been obtained from the Madison limestone.

In chapter thirteen Mr. Stanton describes the Mesozoic fossils.
These were obtained from the Gallatin range, near Electric Peak,
Teton range, in the vicinity of Wildcat Peak and Huckleberry Moun-
tain, and from the Cretaceous ridgesin the southern end of the park and
Yellowstone Forest Reserve. There are seventy-eight invertebrates,
one of which is supposed to be of Triassic age, forty-six are Jurassic,
and thirty-two are Cretaceous. ‘The fossils are mainly from the Ellis
division of the Jurassic and the Colorado of the Cretaceous.

The last chapter, by Mr. Knowlton, on the fossil flora, is along one,
covering 233 pages, besides 45 plates of illustrations. The Mesozoic
flora is confined to the Laramie sandstones of the Cretaceous, and is
found on Mt. Everts, near Mammoth Hot Springs, and at the base of
Pinyon Peak, near the head of Wolverine Creek. The Tertiary flora is
quite varied, and full of biological interest. On comparing it with
the present it signifies great climatic changes since the Miocene. It is
found in numerous localities associated with the breccias and silts of
the igneous rocks, where the muds and silts furnished a soil favorable
to plant growth. The Tertiary fossil flora embraces about 150 forms
in thirty-three orders. The interesting fossil forest trees of Specimen
Ridge are illustrated with photographs of the trees in the field and
enlarged microscopic sections showing the cellular structure.

The petrographical and paleontological features of the Yellowstone
National Park are certainly described in great detail, and the mono-
graph will no doubt prove to be a valuable handbook to scientists,

especially to those visiting the region.
Ge a) Ot

Report on the Geology and Natural Resources of the Area included by
the Nipissing and Temiscaming Map Sheets, comprising portions
of the district of Nipissing, Ontario, and of the county of Pontiac,
Quebec. By ALFRED ERNEsT Bartow. Geological Survey
of Canada. Part I, Annual Report. Vol X, 1899, pp. 302.

This report, accompanied by two well-executed maps on a scale of
four miles to the inch, and covering an area 6912 square miles of the
northern Protaxis of the Dominion of Canada, is a valuable addition
to the literature of the pre-Cambrian of North America and isa further

714 REVIEWS

installment of the work which is being systematically carried forward
by the Dominion Geological Survey on these older rocks. The two
maps, constituting what are known as sheets Nos. 131 and 138 of the
Canadian Series, lie in the Upper Ottawa district along the border of
the two Provinces of Quebec and Ontario, and comprise portions of
both. Lake Nipissing and Lakes Temagami, ‘Temiscaming, and Kee-
pawa, as well as many smaller bodies of water, are included in the
area, and afford along their shores especially good opportunities for
the prosecution of geological work.

After presenting a general account of the early explorations in this
region, some of which date back almost to the time of the earliest
settlement of the country by the French, and of previous surveys, the
physical features of the country are described. ‘The area is a great
uneven, or gently undulating, rocky plateau, sloping somewhat to the
east and southeast, having a general elevation of goo to 1200 feet
above sea level, the level being so nearly uniform that hills 50 to 100
feet higher are conspicuous topographical features. This peneplain is
traversed in a north and south direction along one line by a very deep
and narrow rocky gorge, in which lie Lake Temiscaming and the Ottawa
River. The hills, or cliffs, rise to a height of 400 to 600 feet from the
water on either side, while the water of the lake is 4oo feet deep; the
bottom of the gorge being filled with a fine silt. The depression is
thus at least 1000 feet deep and represents a great canyon similar to
those which are found on the margin of the northern Protaxis at so
many other points. Several smaller rivers also occupy similar depres-
sions. “The detailed examination of the region, however, amply
demonstrates that the sculpturing to which the surface owes its present
configuration was practically completed long before the advent of the
glacial epoch, and that the main valleys, especially those of the Ottawa
and Mattawa rivers, were in existence long prior to the deposition of
the Palaeozoic sediments.” With the exception of some comparatively
small areas occupied by Palaeozoic outliers, ranging in age from Black
River to Niagara, the district is underlain by rocks of Laurentian and
Huronian age. The Laurentian, with the exception of a few small
occurrences, is represented exclusively by the fundamental gneiss, a
mass of granitic and dioritic rocks, usually possessing a foliated
structure in which are many streaks, bands, or inclusions of basic
character, allied to diorites or diabases in composition, and represent-
ing either basic segregations from the granitic magma or portions of

REVIEWS 715

basic intrusions caught up init. This fundamental gneiss, it is believed,
probably represents the original crust of the earth which has under-
gone successive fusions and re-cementations before reaching its present
condition. In placing these rocks at the base of the series it is not
intended to assert that they stand for any distinct or prolonged period
of geological time, nor to affirm that these rocks, in their present con-
dition and with the foliation which they now possess, antedate those of
the Huronian system. This, as is shown, is not the case in many, or
even probably in most, instances.

The chemical and mineralogical composition of the gneisses, as
well as the character and origin of their foliation and the genetic rela-
tion of their associated pegmatites, are considered at length, and many
interesting facts brought forward which cannot here be further dis-
cussed.

The Grenville series, so extensively developed further south, is in
this northern area represented only by a few very small and unimportant
occurrences of highly crystalline limestone and a single occurrence of
gneiss. They occur isolated from one another and surrounded by
fundamental gneiss on every side, and are referred to the Grenville
series on account of their identity in petrographical character with the
areas Of this formation immediately to the south.

The district also includes large tracts of country underlain by
pyroclastic and epiclastic rocks, forming a northeasterly extension of
the development of the “typical”? Huronian area on the north shore
of Lake Huron. At one place on Lake Temiscaming, these Huronian
rocks are found resting upon the floor of fundamental gneiss on which
they were originally deposited, and of whose detritus they are made up,
everywhere else the fundamental gneiss has been’ refused or softened
and penetrates the superincumbent Huronian. The total thickness of
the Huronian in the area is about 1800 feet, made up as follows: 1.
Breccia-Conglomerate, 600 feet. 2. Shales and slaty greywackes, 100
feet. 3. Quartzose grit or Arkose, 1100 feet. Associated with these
Huronian sediments are numerous intrusions of gabbro and diabase,
some of which pass over gradually into flesh-red granites, represent-
ing, it is believed, portions of one and the same magma.

No attempt is made in this report to correlate the Grenville series
and the Huronian of the area, as the facts are insufficient to warrant
the attempt. And it may be remarked incidentally in this connection
that a statement, made on page 415 of the current volume of this

716 REVIEWS

JOURNAL, in reviewing some other recent papers on the Canadian pre-
Cambrian, is scarcely correct. ‘The statement is as follows :

“The succession and correlation proposed in the above papers by
Adams and Barlow and by Ells are fundamentally different from the
traditional one which has been held in Canada for many years. The
first departure is in placing the Grenville and Hastings series as
equivalent to the Huronian.”

In the papers in question this correlation was not definitely made,
but it was stated in reference to the Hastings series that ‘both
lithologically and stratigraphically the rocks bear a striking resemblance
to rocks mapped as Huronian in the region to the north and north-
east of Lake Huron, and it seems very likely that the identity of the
two series may eventually be established. The two areas, however,
are rather widely separated geographically, and the greatest care will
have to be exercised in attempting such a correlation.’’*

The further statement made by the reviewer that ‘‘ Ells places with
the Huronian all the sedimentary rocks of Eastern Canada” is also
manifestly inaccurate, seeing that while it might terminate the con-
troversy concerning the upward extension of the Huronian to include
in that system the whole Palaeozoic succession, Ells cercainly did not
advocate this course.

The Palaeozoic outliers in this area and especially that of Niagara
age are of exceptional interest. Geographically this outlying patch of
Niagara is so widely separated from any other locality where rocks of
this age are now known to exist, that it has been a question as to whether
it was formerly connected with the occurrences about Hudson Bay or
with those about Lake Ontario. The strata are highly fossiliferous
and the palaeontological evidence presented seems to prove that the
seas in which the Niagara sediments of the Winnipeg basin and of
Hudson Bay were deposited were practically continuous, while both
were separated from the Temiscaming basin and the region to the
southwest.

The Pleistocene history of the region seems to consist of a period
of glaciation by a great ice-sheet, followed by a profound submergence,
during which time the ocean invaded a large portion of the Ottawa
valley forming a marine gulf rivaling in extent the similar invasions
of the sea in Palaeozoic times. The direction of motion of the ice
varies from S 7° W to S 18° W.

t American Journal of Science, Vol. III, March 1897, p. 177.

REVIEWS . 717

The report also contains much information concerning the fauna,
flora, and timber resources of the district, and has appendices giving
lists of elevations and catalogues of the Palaeozoic fossils.

FRANK D. ADaMs.

The Paleozoic Reticulate Sponges Constituting the Family Dictyo-
spongidae. By JAMES Hay and Joun M. Crarke.

More than a year ago volume one of the Fifteenth Annual Report
of the New York state geologist made its appearance. In the introduc-
tion to this report several papers were announced which were not
included in the volume, one of them being a monograph of the
Dictyospongidae. It is this monograph which has now been published
as volume two of the report above mentioned. It also appears in
another binding as Memoir II of the New York State Museum.
Unfortunately the annual report of the state geologist does not con-
tain the complete monograph, the descriptions and illustrations of Car-
boniferous species being omitted. This monograph has long been in
preparation by Drs. Hall and Clarke, and the printing of it had only
been begun at the time of Dr. Hall’s death.

The dictyospongidae are an extinct family of hexactinellid sponges,
whose nearest living representative is the delicate glass sponge,
Euplectella, commonly known as the “venus flower basket.” They
lived in greatest abundance during later Devonian and early Carbon-
iferous time, though their most ancient representatives occur far back
in the Silurian. Their fossil remains are especially abundant in the
sandstones of the Chemung formation in western New York, several
extensive colonies of them having been discovered as they grew upon
the ancient sea bottom. Notable collections of them have also been
made in the Waverly sandstones in Ohio, and in the Keokuk shale at
Crawfordsville, Ind., and from the last locality only, have specimens
been found in which the spicular skeleton of the sponge has been pre-
served.

The variety of forms assumed by these interesting sponges is won-
derful, and the earlier observers were at a loss to know where to place
them in the zodlogical classification. Before their sponge nature had
been definitely established by Whitfield in 1881, they had been
described as cephalopods and as marine plants. In life these organisms
must have been most beautiful objects, “with their manifold variety of

718 REVIEWS

graceful and striking shapes, they were not the somber bodies we find
them to be in the rocks, but formed the most delicately woven fabrics
of glass, latticed vases, urns and cups of the rarest delicacy and
beauty. ‘They must have been, when denuded of their sarcode, among
the most exquisite structures of the past, as their descendants are of
the present. Nothing, for example, could have surpassed the graceful
filigreed chalice of Botryodictya ramosa, with its slender, tufted pedicel
expanding above with a cup ornamented with pendant pouches.”

In the list of genera and species, twenty-eight genera and one
hundred and twenty eight species of these organisms are recognized,
a great majority of them being here described for the first time.
These descriptions of genera and species, with the introductory
portion of the volume, fill two hundred quarto pages of text, and
they are illustrated by seventy finely executed lithographic plates.

Swe

Geological Report on Isle Royale, Michigan. By ALFRED C. LANE.
Geological Survey of Michigan, Vol. VI, Part I. Lansing,
1898, pp. 1-281. 16 plates, 29 feunes, 13 tables,

The report begins with a historical sketch of the mining opera-
tions from pre-historic times to the present. This is followed by a
description of the method of constructing cross sections of the
country from drill records, and this by an account of the succession of
rocks forming the island, involving a detailed statement of the rocks
traversed by sixteen drill holes. The results are compared with
Irving’s cross sections of Keweenaw Point, and the conclusion reached
that there is represented on the Isle Royale practically the whole of the
copper range as it exists from the Central mine to Portage Lake.
A comparison is made with the Minnesota section with less definite
results.

The portion of the report of more general interest is that which
treats of the grain of rocks, both the theoretical discussion and the
application of the theory to the rocks under investigation. The dis-
cussion opens with the consideration of conditions that affect cooling
of molten magmas. Laws controlling the loss of heat are expressed
mathematically, and diagrams are constructed exhibiting rates of
cooling under various conditions. Deductions regarding the variations

REVIEWS 719

in the grain of rocks corresponding to these conditions are exceed-
ingly important and interesting. Some of the theoretical deductions
are as follows : (1) After the temperature at the center of an intruded
magma has fallen about one fourth of the interval between the initial
temperature and the marginal temperature, the rate of cooling at a
given temperature is the same for all. parts of the sheet. (2) If the
initial temperature (of intrusion) and conditions of cooling are such
that a considerable time elapses before any part of the sheet reaches
the point of solidification, the rate of cooling will be the same at all
points, and, so far as the grain is dependent on it, there will be no
change of grain, but the grain will be uniform from margin to center.
(3) The hotter the dike or sheet initially, the less will be the width of
the marginal zones of gradually finer grain; also, the hotter the
country rock, the less pronounced will be the marginal zone of finer
grain. (4) The time of cooling varies as the square of the thickness
of the dike or sheet, so that a dike 200 feet thick will cool four times
as slowly, other things being equal, as a dike 100 feet thick. (5)
Before the center (of an intruded mass) begins to cool off, the time
required for a given loss of temperature for any point will vary as the
square of its distance from the margin.

In applying the theory to the rocks examined it was found that
some minerals, such as augite and feldspar, conformed fairly with
theoretical requirements. In the case of sheets which have solidified
before the center had appreciably cooled, it was found that ‘the area
of cross sections or surface of the grains varies directly as the slowness
Again, “ the linear dimensions of the augite patches (in

yr}

of cooling.
the ophites, are directly as the distance from the margin.”

With regard to the effect of chemical composition on grain, it is
announced that “ other things being equal, the greater the abundance
of its constituent molecules, the coarser the grain of any mineral.”’

In conclusion, Dr. Lane ventures the prophecy “that it will prove
widely true that superficial (extrusive) basic rocks are characterized by
an increase of grain to near the center, while deep-seated basic rocks
have a broad central zone of nearly uniform grain.” He remarks in
connection with the question of the effect of geological environment
upon rocks that “it must also be remembered that the possession
and loss of gas by diffusion follow the same laws as the possession and
loss of the imponderable ‘caloric,’ while the possession of gas may
greatly lower the temperature of solidification as glass.”

720 REVIEWS

The report closes with chapters on the petrography of the rocks;
on the topography and Quaternary geology; the stratigraphy; and
the chemical problems which are treated briefly. The last chapter is
devoted to diabases, probably Keweenawan, intrusive in the Huronian.
Among various interesting observations made in connection with these
rocks is the conclusion that the micropegmatitic (micographic) inter-
growth of quartz and feldspar found in some of them is undoubtedly
a primary cystallization, and not a result of alteration in the rock.

Wor dee: dls

The Department of Geology and Natural Resources of Indiana.
Twenty-third Annual Report. By GEORGE H. ASHLEY,
Ph.D., Assistant State Geologist.

The report consists of 1741 pages, the first 1573 of which are
devoted to the coals and coal area of the state. The state geologist,
Mr. W. S. Blatchley, is to be congratulated on having secured, for this
work of such importance to the state, the services of so painstaking
and energetic a worker as Dr. Ashley.

The primary idea of the author seems to have been to make the
report of the greatest possible value to those interested in the coal
industry. Nevertheless it discloses much that is new concerning the
structure of the southwestern part of the state, and throws light on the
physical conditions that attended the formation of the Coal Measures
of the eastern interior coal field.

Instead of using the letters of the alphabet to designate the differ-
ent coal beds, as is done by Mr. Cox in the Seventh Annual Report,
or Arabic numerals, as was done in the Illinois and Kentucky reports,
the author has made use of Roman numerals, each of which denotes a
division of the Coal Measures. There are eight of these divisions,
numbered from below upward. In those localities, where a division
includes more than one coal bed, the small letters of the alphabet are
brought into use. For example, the three coals of Division v are
designated v, va, vb. This method seems to present the advantage
of at all times denoting the exact horizon under consideration, and of
locating the beds of small area.

The organization of the volume divides it into four parts. Part I
dealing with the Geology of Coal; Part II, with the General Geology

REVIEWS 721

of the Coal Measures of Indiana; Part III, with the Detailed Geology
of the Indiana Coal Field; and Part IV, with Mines, Mining, and the
Utilization of Coal. In Part III the method of treatment is by coun-
ties.

Probably the best feature of the report is to be found in the excel-
lent illustrations, which consist of 986 figures, g1 plates, and 7 maps.
Especially are the maps and the accompanying sections to be com-
mended.

The latter part of the volume is devoted to reports of the inspector

of. mines and the natural gas supervisor.
A. H. PURDUE.
UNIVERSITY OF ARKANSAS,
Fayetteville, Ark.

United States Geological Survey. Monograph XXXT. Geology
of the Aspen Mining District, Colorado, with Atlas. JOSIAH
EpWARD Spurr. Samuel Franklin Emmons, geologist in
charge.

The monograph is primarily concerned with the economic interests
of the Aspen district. But it also contains much that is of general
scientific interest. Mr. Emmons contributes the introduction, but the
body of the monograph is the work of Mr. Spurr. The volume is
profusely illustrated and the accompanying atlas contains sheets giving
the general geology and topography of the district, besides eight special
sheets giving the detailed geology of limited areas. It also contains
numerous sections constructed on an elaborate scale, which make the
complex faulting intelligible. Both the monograph and its accompany-
ing atlas exemplify the magnificent execution characteristic of the
United States Geological Survey.

Great interest attaches to the author’s study of faults as set forth in
this work. Aspen seems to have furnished a field quite worthy of his
best endeavor. Some of the sheets presented in the atlas seem like
inextricable puzzles; but this special student of faults straightens out
the “crazy-work”’ in an admirable way and makes it all intelligible.
It is of interest to note the fact that movement along some of the fault-
ing plains is taking place at the present time at a rate which requires
recognition in the practical operations of mining.

722 REVIEWS

Under “Chemical Geology” some observations are given which
throw light on the vexed question of dolomization. The origin and

change of ores is also discussed.
We de ee:

Geological Survey of Georgia: WW. S. Yeates, State Geologist.
Bulletin No. 7, A Preliminary Report on the Artestan-Well
System of Georgia. By S. W. McCattiz, Assistant Geolo-
gist. - State Printer, Atlanta, Ga., 1898, pp. 214.

One of the significant signs of growing wisdom in the administra-
tion of state surveys is the increased attention given to common
resources of wide interest as distinguished from rich deposits of imme-
diate value to a fortunate few only. Among these resources of com-
mon interest is the water supply which admits of successful treatment
on a scientific basis, whether in the form of flowing wells or otherwise.
In real importance it transcends many of the more impressive subjects.
The present treaties is an excellent expression of this commendable
policy. ‘The first thirty pages are devoted to a clear exposition of the
essential conditions of successful artesian wells and practical con-
siderations relative to them. This is well illustrated. The rest of the
volume is devoted to the special consideration of the artesian wells of
Georgia, in which much data of general geological interest is inci-
dentally included. J.arge artesian resourses are shown. While full
data are not obtainable, it is clear that notable improvement in public
health has resulted from the use of these wells. die Os iC.

TECENT PUBLICATIONS

—American Institute of Mining Engineers, Transactions of, Vol. XX XVIII,
February 1898 to October 1898, inclusive. Published by the Institute
at the Office of the Secretary, New York City, 1899.

—Ami, HENRY M. Qn Some Cambro-Silurian and Silurian Fossils from
Lake Temiscaming, Lake Nipissing and Mattawa. Extract Ann. Rep.
Geol. Surv. of Canada, Vol. X, Part I, Appendix II, pp. 282-301.
Ottawa, September 1899.

—Bulletin of the American Museum of Natural History, Vol. XI, Part II,
1899. Catalogue of the Types and Figured Specimens in the Paleon-
tological Collection of the Geological Department of the American
Museum of Natural History. R. P. Whittield, assisted by E. O. Hovey.
October 12, 1899.

—Bulletin of the U. S. Geological Survey, No. 162. Bibliography and
Index of North American Geology, Paleontology, Petrology and
Mineralogy, 1898. Weeks. Washington, 1899.

—E Luts, R. W., LL.D. Canadian Geological Nomenclature. Presidential
Address. Transactions of the Royal Society of Canada. Second Series,
1899-1900, Vol, V, Section IV. Ottawa, 1899.

—FARRINGTON, OLIVER C. Notes on European Museums. The American
Naturalist, October 1899, Vol. XX XIII, No. 394. Boston, 1899.

—Fraas, Dr. E. Die Bildung der germanischen Trias, eine petrogene-
tische Studie. Separat-Abdruck aus Jahreshefte des Vereins fiir Vaterl.
Naturkunde in Wiirttemberg.

Proganochelys Quenstedtii Baur (Psammochelys Keuperina Qu.) Ein
neuer Fund der Keuperschildkréte aus dem Stubensandstein. 02d.
Stuttgart, 1899.

—GEIKIE, SIR ARCHIBALD. Address to Geological Section British Associa-

tion for Advancement of Science, Dover, 1899. Time as an Element in
Geological History, etc.

—Geological Survey of Georgia. Bulletin No. 7. A Preliminary Report on
the Artesian-Well System of Georgia. By S. W. McCallie, Assistant
Geologist. Atlanta, Ga., 1899.

723

724 RECENT PUBLICATIONS:

—HALL, PROFESSOR C. W. Description of the Keewatin in Minnesota.
Reprinted from Science, N. S., Vol. X, No. 239, pp. 107-I10. July 28
1899.

Exploration for Gold in the Central States. From the Proceedings of
the Lake Superior Mining Institute, 1898, Vol. V, pp. 49-60.

—Hay, O. P. On Some Changes in the Names, Generic and Specific, of Cer-
tain Fossil Fishes. American Naturalist, Vol. XXXIII, No. 394, Octo-
ber, 1899. Boston, Ginn & Co.

Descriptions of the Two New Species of Tortoises from the Tertiary
of the United States. Proceedings of the U. S. National Museum, Vol.
XXII, No. 1181. Washington, 1899.

—HILu, Ropert T. The Geology and Physical Geography of Jamaica;
Study of a Type of Antillean Development. Based upon Surveys made
for Alexander Agassiz. With an Appendix on Some Cretaceous and
Eocene Corals from Jamaica. By T. Wayland Vaughan. With Forty-
one Plates. Bulletin of the Museum of Comparative Zodlogy of Har-
vard College, Vol. 1V, Cambridge, 1899.

—Indiana Academy of Science, Proceedings of 1898. Indianapolis, 1899.

—KING, FRANKLIN HIRAM. Principles and Conditions of the Movements
of Ground Water. With a Theoretical investigation of the Motion of
Ground Waters, by Charles Sumner Slichter. Extract from Nineteenth
Annual Report of the U. S. Geological Survey, 1897-8, Part II.
Washington, 1899.

—MANSON, MARSDEN. The Evolution of Climates. From the American
Naturalist, Vol. XXIV. August, September and October 1899.

—MERRIAM, HARTC. North American Fauna No. 16. Results of a Bio-
logical Survey of Mount Shasta, California. U.S. Department of Agri-
culture. Division of Biological Survey. Washington, 1899.

—MERRILL, GEORGE P. A Discussion on the Use of the Terms Rock-
Weathering, Serpentinization, and Hydrometamorphism. From the
American Naturalist, Vol. XXIV, October 1899.

—MoseErG, Jon. Cur. Sveriges Alsta Kanda Trilobiter. Aftryck Ur Geol.
Féren. I Stockholm:Férhandl. Bd. 21.°H.4. Stockholm, 1899.

—SARDESON, F. W. The Geological Club of the University of Minnesota.
Reprinted from Science, N.S., Vol. IX, No. 220, pp. 412-413, March 7,
1899.

A New Cystocrinoidean Species from the Ordovician. From the
American Geologist, Vol. XXIV, November 1899.

RECENT PUBLICATIONS 725

—SMITH, WILLIAM. S. TANGIER. Some Aspects of Erosion in Relation to
the Theory of the Peneplain. Bulletin of the Department of Geology
of the University of California, Vol. 2, No. 6, pp. 155-178. Berkeley,
1899.

—TAYLOR, FRANK BURSLEY. The Great Ice Dams of Lakes Maumee,
Whittlesey, and Warren. From the American Geologist, Vol. XXIV,
July 1899.

—UssinG, N. V. Sandstengangei Granit paa Bornholm. K¢@benhavn, 1899.

eet

pers E \
Tees

Wyse Rs

THE

JOURNAL OF GEOLOGY

NOVEMBER— DECEMBER, 1899

SIR WILLIAM DAWSON.

In Sir William Dawson there has passed away the last sur-
vivor of that distinguished group of naturalists which in the
earlier part of this century achieved for science in America such
brilliant results and such widespread recognition—imen whose
range of knowledge was almost encyclopedic, and many of
whom made valuable contributions to science in widely separated
fields. The environment of the man of science has now changed,
and the older type of naturalist seems unfortunately about to
disappear.

Sir John William Dawson was from near Nova Scotia, a
province which has produced more than its share of the Cana-
dians who have risen to eminence in the various walks of life,
having been born at Pictou on October 13, 1820. He died at
Montreal on November 19, 1899, at the age of 79.

His father, James Dawson, was from near Aberdeen, Scot-
land, and came to Nova Scotia to fill a position in a leading
business house in Pictou, and on the termination of his engage-
ment began business there as a shipbuilder on his own account.

While still at school in Pictou, at the age of 12, he developed
a love for natural science, inherited from his father, and made
large collections of fossil plants from the Nova Scotia Coal
Measures, so well exposed about his native place. He speaks of
Vol. VII, No. 8, 727

728 FRANK D. ADAMS

himself at that time as being a “moderately diligent, but not a
specially brilliant pupil.” On leaving school he studied at
Pictou college, and subsequently at the University of Edinburgh.
While at the former seat of learning, at the age of 16, he read
before the local Natural History Society his first paper, having |
the somewhat ambitious title ‘‘On the Structure and History of
the Earth.’’ He returned to Nova Scotia in 1847, and two years
later went to Halifax to give a course of lectures on natural his-
tory subjects in connection with Dalhousie College, and organized
classes for practical work in mineralogy and _ paleontology.
These were attended by students, citizens, and pupils of higher
schools, a foreshadowing of university extension. In 1850, at
the age of 30, having already attracted some attention by the
publication of a number of papers, reports, and lectures, he was
appointed Superintendent of Education for Nova Scotia. From
this time he became known in his native province as an inde-
fatigable promoter of educational progress, and a founder of
educational institutions. His work in connection with this posi-
tion obliged him to travel continually through all parts of the
province, and on these journeys he accumulated that immense
mass of information concerning the geology and mineral
resources of Nova Scotia which are incorporated in his largest
work—that entitled Acadian Geology.

Sir Charles Lyell, in 1841, on his first visit to America, met
Sir William, and was by him conducted to many places of geo-
logical interest in Nova Scotia, and on his subsequent visit in
1852 they together continued their studies in Nova Scotian
geology. In a letter to, Weonard Horner, dated Septembeniz
of this year, Lyell writes:

‘My companion, J. W. Dawson, is continually referring to the
curious botanical points respecting calamites, endogenites, and
other coal plants, on which light is thrown by certain specimens
collected by him at) Pictou.) ble told me thatthe root ol eje
pond lily, Nymphza Odorata, most resembled Stigmaria in the
regularity of its growth, and Dr. Robb showed me a dried speci-
men, a rhizoma, which being of a totally different family, and

SIR WILLIAM DAWSON 729

therefore not strictly like, still suggests the probability of the
Stigmaria having grown in slush in like manner.’’ And in another
part of the same letter, referring to the now celebrated Joggins
section on the coast of Nova Scotia, he says: ‘‘Dawson and
I set to work and measured, foot by foot, many hundred yards of
the cliffs, where forests of erect trees and calamites most
abound. It was hard work, as the wind one day was stormy and
we had to look sharp lest the rocking of living trees, just ready
to fall from the top of the undermined cliff, should cause some
of the old fossil ones to come down upon us by the run. But I
never enjoyed the reading of a marvelous chapter of the big
volume more. We missed a botanical aid-de-camp much when
we came to the tops and bottoms of calamites and all sorts of
strange pranks which some of the compressed trees played.”

About this time the governing body of McGill College at
Montreal was looking about for some one fitted to assume the
principalship of the institution and to reorganize it.

The college, fotnded by Royal Charter in 1821, had made
but slow progress in its earlier years, and was at this time,
through litigation and other causes, almost in a state of collapse.
Sir William, then Mr. Dawson, was pointed out to the Governors
of the College by Sir Edmund Head, then Governor General of
Canada, as a man who, if his services could be secured, was
eminently fitted to undertake the task of reconstructing the uni-
versity. In the meantime, ignorant of all this, he was prose-
cuting a candidature for the chair of Natural History in his alma
mater, the University of Edinburgh, rendered vacant by the
death of Professor Edward Forbes, and in which he was strongly
supported by the leading geologists of the time. By a strange
coincidence, just as he was about to leave Halifax for England in
connection with this candidature, intelligence arrived that the
Edinburgh chair had been filled at an earlier date than his
friends had anticipated, and at the same time a letter was
received offering him the principalship of McGill.

The services of Dr. Dawson were accordingly secured, and in
1855 he assumed the principalship of McGill College, stipulating

730 FRANK D. ADAMS

at the same time that the chair of Natural History should be
assigned to him. In his inaugural discourse he said: “At a
time when literary and scientific pursuits are so widely ramified
everyone who aims to do anything well must have his special
field of activity. Mine has been the study of nature, especially
in those bygone aspects which it is the province of geology to
investigate. My only other special qualification for my present
position depends on the circumstance that the wants of my
native province have induced me to devote much time to inquir-
ies and pursuits relating to popular education. I come to you,
therefore, as a naturalist and an educationalist, trusting that I
may be enabled in these capacities to render myself useful, and
asking for my youth and present inexperience in the affairs of
this institution your kind indulgence, and for the work in which
I shall be engaged your zealous codperation.”

The University as he found it had three faculties and but
sixteen professors, a number of whom gave only a portion of
their time to university work, while the buildings and equipment
were wretched. When it is stated that the University has now
120 professors and instructors of various grades and an equip-
ment which is in all departments fairly good, and, in some of
them, unsurpassed, some idea may be gained of the progress
which the institution made under Sir William Dawson’s care and
guidance.

As a professor of natural science Sir William at this time
delivered courses in chemistry, botany, zodlogy, and geology,
and natural science became a very favorite study among the
students, for he was an excellent lecturer, and his enthusiasm for
these studies was communicated to all who heard him. As
years went on, the instruction in the first three of these subjects
was undertaken by others, and a special chair of Geology and
Paleontology was endowed by his old friend and co-worker,
Sir William Logan, a chair which he held until his final retire-
ment. His teaching work, however, formed but a small part of
his daily labors. In addition to administering the affairs of the
University he was first and foremost in every movement to

Slits WILLIAM’ DAW SOM. Fou

further education in the province, and no educational board was
complete without him. He was the honorary president of the
Natural History Society and never missed a meeting or a field
day, and also identified himself closely with many other socie-
ties in Montreal, and spared neither time nor labor on their
behalf.

Over and above all this he found time to carry out original
work along several lines, achieving most valuable results, as well
as to write many popular works on science, more especially in its
relation to religion. Original investigation he always considered
to be one of the chief duties and pleasures of a man of science.
Most of his work along these lines was done during his summer
vacations; in fact he was led to accept the position of principal
in McGill chiefly by the fact that the vacations gave him leisure
and opportunity for work of this kind.

He was always very progressive in his ideas relative to the
scope and development of university teaching, and was continu-
ally urging the endowment of new chairs and the broadening of
university work, so that all young men wishing to train them-
selves for the higher walks of life might in the university find
their needs supplied. As an instance of this it may be men-
tioned that so far back as 1858 he succeeded in establishing a
school of civil engineering, which, after a severe struggle for five
years, succumbed to some unfriendly legislation, only, however,
to be revived by him in 1871 and developed into the present
faculty of applied science of McGill University, with its numer-
ous departments, its full staff of instructors and excellent equip-
ment. Sir William, furthermore, never ‘hesitated, if funds were
not forthcoming in sufficient amount for these purposes, to sub-
scribe large sums out of his own limited private means, and he
was also the continual helper of needy students desiring to avail
themselves of the University’s teaching.

Sir William received the degree of M.A. from the University
of Edinburgh in 1856, and the degree of LL.D. from the same
University in 1884. His attainments and the value of his con-
tributions to science were widely recognized, and he was elected

732 FRANK D. ADAMS

an honorary or corresponding member of many learned societies
on both sides of the Atlantic. He was madea Fellow of the
Geological Society of London in 1854 and of the Royal Society
in 1862. In 1882 he was invited by Lord Lorne to aid in the
organization of the Royal Society of Canada as its first presi-
dent. He was also President of the Geological Society of
America and of both the American and British Associations
for the Advancement of Science. In1884 he received the honor
of knighthood.

After a long life of continuous labor, Sir William's health, in
1892, became seriously impaired, and it became necessary for him
to lay aside his work for a time and spend a winter in the South.
Failing to recover his strength, however, he resigned his posi-
tion as principal in June 1893, and retired from active work. Dur-
ing the later years of his life his strength gradually ebbed away,
and what little work he could undertake consisted in arrang-
ing his collections and working up some unfinished papers.
Several of these were published in 1894 and 1895, but the years
of quiet labor in his favorite pursuits, to which he looked for-
ward at this time, were cut short by a series of sharp attacks,
culminating in partial paralysis, which forbade further effort.
During the last few years, from time to time, his strength rallied
somewhat and he attempted to resume his work. Only a few
days before his death he penned a short essay on the “‘ Gold of
Ophir.” He passed away on the tgth of last month, very peace-
fully and without pain. We may say, in the words of Dr. Peter-
son, his successor in the principalship of the University, ‘‘ For
such a painless passing out of life no note of sorrow need be
struck. There is no sting in a death like his; the grave is not
his conqueror. Rather has death been swallowed up in victory
—the victory of a full and complete life, marked by earnest
endeavor, untiring industry, continuous devotion and self-sacri-
fice, together with an abiding and ever-present sense of depend-
ence on the will of heaven. His work was done, to quote the
great Puritan’s noble line, ‘As ever in his great Taskmaster’s

» 9)

eye.

STR WILLIAM DAWSON 33

Lady Dawson, with three sons and two daughters, survive
him, of whom the eldest, Dr. George M. Dawson, the present
director of the Geological Survey of Canada, has inherited his
father’s love for geological studies, and has achieved wide dis-
tinction in the world of science.

Sir William’s first original contribution to science was a paper
read before the Wernerian Society of Edinburgh in 1841, on a spe-
cies of field mouse found in Nova Scotia. From that time
onward he was a continuous contributor to scientific journals and
to the publications of various learned societies. His papers
were very numerous and covered a wide range of subjects in the
domain of natural history. No less than 158 titles are recorded
under his name in the Royal Society’s catalogue; and in a bibli-
ography which he prepared for the Royal Society of Canada in
1895, and which included only books and papers of the first
importance, 128 titles are recorded. He contributed over 100
papers to the publications of the Montreal Natural History
Society alone. His complete bibliography, now in course of
preparation, will certainly include several hundred contribu-
tions. The most important work of his earlier years was an
extended study of the geology of the maritime provinces of the
Dominion of Canada. His results are embodied in his Acadian
Geology, already mentioned, a volume of nearly 1000 pages,
accompanied by a colored geological map of Nova Scotia, which
has passed through four editions. In writing to Sir William in
1868, Sir Charles Lyell says of this work: ‘I have been read-
ing it steadily and with increased pleasure and profit. It is so
full of original observation and sound theoretical views that it
must, I think, make its way, and will certainly be highly prized
by the more advanced scientific readers.” It is the most com-
plete account which we have of the geology of Nova Scotia, New
Brunswick, and Prince Edward’s Island, although since it appeared
large portions of these provinces have been mapped in detail by
the Geological Survey of Canada, and Sir William’s conclusions
modified in some particulars. In carrying out this work Sir
William paid especial attention to the paleontology of the

734 FRANK D. ADAMS

Carboniferous system, and to the whole question of the nature
and mode of accumulation ‘of coal. He subsequently studied the
paleontology of the Devonian and Upper Silurian systems of
Canada, discovering many new and important forms of plant life.
In 1884 he began the study of the Cretaceous and Tertiary fos-
sil plants of western Canada, and published the first of a series
of papers on the successive floras from the lower Cretaceous
onwards, which appeared in the Zvansactions of the Royal Society
of Canada. He also contributed a volume entitled Zhe Geologi-
cal History of Plants to Appleton’s International Scientific Series.
In 1863 he published his Azr Breathers of the Coal Pertod, in which
were collected the results of many years’ study in the fossil
batrachians and the land animals of the Coal Measures of Nova
Scotia. The earliest known remains of microsauria were then
discovered by him in the interior of decayed tree stumps in the
Coal Measures of South Joggins. The results of his later studies
in these creatures were embodied ina series of subsequent papers
which appeared from time to time.

On taking up his residence in Montreal his attention was
attracted by the remarkable development of Pleistocene deposits
exposed in the vicinity of the city, and he undertook a detailed
study of them, and especially of the remarkably rich fossil fauna
which they contain. He also studied subsequently the Pleisto-
cene deposits of the lower St. Lawrence, and instituted compari-
sons between them and the present fauna of the Gulf of St.
Lawrence and of the Labrador coast. The results of these studies
appeared in a series of papers as the work progressed, and were
finally embodied in a volume entitled The Canadian Ice Age,
which was issued in 1893 as one of the publications of the Peter
Redpath Museum of McGill University. This is one of the most
important contributions to the paleontology of the Pleistocene
which has hitherto appeared.

Sir William’s name is also associated with the renowned
Eozoon Canadense, discovered by the Geological Survey of
Canada in the Grenville limestones of the Canadian Lauren-
tian, and described by him in 1864 as a gigantic foraminifer.

SIR WILLIAM DAWSON 73>

Concerning this remarkable object there has been a widespread
controversy and a great divergence of opinion. Some of the most
experienced observers in the lower forms of life, such as Carpen-
ter, accepted it as of organic origin, while others considered it
to be inorganic, and while the balance of opinion now possibly
favors the latter view, its resemblance microscopically to certain
organic forms is certainly most remarkable. The literature of
this subject, which includes many papers by Sir William, is quite
voluminous, but the chief facts are summed up in his book,
entitled Zhe Dawn of Life, which appeared in 1875.

Sir William was also a prolific writer of popular works
on various geological topics. Among these may be mentioned
Fossil Men and Their Modern Representatives, The Chain of Life in
Geological Time, Egypt and Syria their Geology and Physical Geogra-
phy in Bible History, Modern Science in Bible Lands, Modern Ideas of
Evolution, Salient Points tn the Science of the Earth, Eden Lost and
Won, and Relics of Primeval Life. As may be inferred from their
titles, many of these books display a strong theological bias. Sir
William was a Presbyterian of the old school and _ strongly
opposed to all theories of the evolution of man from brute ances-
tors, nor would he allow anything more than a very moderate
antiquity for the species. ‘He held that there is no adequate

d

reason for attributing the so-called ‘‘ Neolithic”? man to any time
older than that of the early eastern empires, while he thought
the time for Paleolithic man need not be more than twenty or
thirty centuries in addition, man having thus made an abrupt
appearance in full perfection not more than, say, six or eight
thousand years ago.

These works on the relation of science and religion met a
popular need and were of great comfort to many a pious soul, who
feared that the whole framework of faith was being swept away
by the advancement of science. Their value, however, was not
permanent, and they are not the works by which Sir William
Dawson will be remembered. His reputation is founded on the
great contributions to our permanent stock of knowledge which
he has made and which are embodied in his works on pure

736 FRANK D. ADAMS

science, representing achievements of which any man might
well be proud. —

Sir William had a courteous, or rather a courtly, manner,
based on a genuine consideration for all. He was respected and
beloved by all who knew him, and especially endeared himself
to all who studied under him. The preéminent note of his char-
acter was simplicity and singleness of purpose. His loss will be
felt especially in the institution with which he was long con-
nected, but his name has been perpetuated in connection with
the geological department of his university by the establishment
of a second chair in geology, to be known as the Dawson Chair,
which has just been endowed in his memory by Sir William
Macdonald.

FRANK D. ADAMS.

GRANITE ROCKS OF BUITE, MONT; AND. VICINITY:

In the western mountainous part of Montana there are sev-
eral extensive areas of granitic rocks, which are commonly sur-
rounded by sedimentary beds and in part covered by later
volcanic rocks. The largest of these granite masses forms a
mountainous area having no commanding summits, but consti-
tuting the continental water parting separating the waters of the
Atlantic from those tributary to the Pacific Ocean. This district
is largely drained by the Boulder River, and as the mountains
have no other name, they too are sometimes called by this name,
for which reason it will be used to designate the intrusive mass of
granite itself. Unmistakable evidences of intrusion are common
about its borders, and as the rock cuts and metamorphoses fos-
siliferous Carboniferous rocks and what are believed to be Creta-
ceous rocks as well, and is overlaid by Neocene sediments, its
age is known within these limits.

The Boulder batholith is a body of granitic rock, in part cov-
ered by later lavas, but continuously exposed from the Highland
Mountains (sixteen miles south of Butte) to the vicinity of
Helena, a distance of fifty miles in a north and south direction
and twenty-four miles from east to west. The intrusive nature
of the mass is very strikingly shown at the northern and southern
limits, and also at Elkhorn on the east. At these places the
granitic rocks have produced very marked contact metamorphism,
and cut across the ends of the upturned sedimentary series.
Near its border the granite also includes in its mass fragments of
the other rocks. There is no suggestion of a laccolithic uplift-
ing, for although near Helena, and probably elsewhere, the
granitic rocks extend outward under the sedimentary rocks, and
the latter in certain places form a thin cover over the intrusion,
yet the strata dip toward the intrusion conformable to a great
anticlinal uplift wholly independent of the batholith.

* Published by permission of the Director of the U.S. Geological Survey.

737

738 WALTER HARVEY WEED

The rocks of this batholith present a wide variation in min-
eral and chemical composition, but a study of the field relations
shows they must be regarded not only as facies of the same
magma, but as parts of one mass. The very basic rocks all occur
at the margins, yet there are variations within the main body
itself which are clearly recognizable rock types, yet cannot be
discriminated in mapping. This difficulty has been experienced
by those geologists working in the Sierra Nevada, where, as
stated by Turner,’ a considerable variety of rock-types have been
mapped as granodiorite, ‘‘although, as a rule, gabbro, even when
genetically related to granodiorite proper, has been separated.’
Where detailed mapping upon a large scale map is not possible,
this difficulty of separating parts of a single intrusive body in
which the rock-types grade into one another can only be met by an
arbitrary use of the name of the prevailing rock-type for the entire
mass,as has commonly been done heretofore, or by using a generic
term like granolite* to embrace all coarsely granular rocks.

The prevailing rock of the batholith is a granite whose com-
position is that given under the number 518. It is a normal
hornblende-granite which is very generally sheeted, forming
picturesque crags and bowlder groupings. It disintegrates readily
into platy masses or shells which separate from the bowlders,
and themselves crumble to a coarse sand. Over large tracts
disintegration has reduced the rock to a smoothly rolling sur-
face, on which scattered bowlders rise above the general level.
Perfectly fresh material can, therefore, be obtained only where
the rock has been quarried or exposed by mining operations. It
is a medium to coarse-grained rock, the average size of the grains
being 3-5mm. The grayish quartz and white feldspar grains are
of about equal size. Black mica and dark green hornblende are
present in considerable quantity. Under the microscope it shows
the normal characters of a granite, but contains an unusual
amount of plagioclase.

tH. W. TurNER: Granitic rocks of Sierra Nevada, Jour. GEOoL., Vol. VII,
1899, p. 146. f

2See DURNER > lociicit., ps 141.

GRANITE KOCKS OF BUTTE, MONT., AND VICINITY 739

In the following table the results are given of the analyses so
far made of the rocks of the Boulder batholith:

ANALYSES OF ROCKS FROM THE POST-CRETACEOUS GRANITIC BATHO-
LITH OF THE BOULDER MOUNTAINS, MONTANA

Butte granite Aplites

a 526 525 130 311 623 6 989 98 518 640 g5I
SiO,......... ./49.22/56. 41/61 .64)63 .87/63.88) 64.05/64.34| 64.17/67.12/76.87| 77.05
PLO) recta toiars casi OFO5|| 10-08!) B57 TE) 265) 265 60] .53 G7) AS) 2, Tor Hh2
AU Ola creas See L2 0207. O21 5 OZ/lh. 20 Dh 104) 15.39/15 72 15.2505 O02 a5 2)" 12.074
Hes Oned a 277 le24l 330 na03 2. )1l| 2.2011 502i) 62.70) 1 .62'| G67, .56
Ne Ol ret wecsress 8.80] 3.55] 2.69] 3.08] 2.59] 2.74] 2.94] 2.98] 2.23] none .14
INO teers crete tr FOS|p a sOAy kealris, 207 SEU le 104|| OG) wow. a mone
(CF OR eae ee 10.56) 8.66) 4.90] 4.30] 3.97] 4-30] 4.24] 4.24] 3.43] 0.49 157
IMS Oe a neice OP2O|eae O72 O2e2 222) 2203) e208 217s 2 001i 47.4 NO.09 tr
Ke OMe eremccnou tte. Le fOP2 OU .72|0 4618) A423 qOol 4.04 a. 34\ea 5215.70) 552
INNO’ Saause ode EROO|| Be25|\ 2 04) 276)! 2S" 2.7222, 76) 2.62162.70|) 2.4176 2 or
Hi,O below 110°; 0.27| .14) .28| .19]. .22 P27 25 ALOE OO sOR25 222
Hi Orabove 1107) 1563) 276]-..91) .69] -..66 HOR iy ea7i0 -65} .58) 0.52 .48
BAG) etencueas weed S 203| 09) {os {o7| 200 08} .06 207) es O7]|) eet | none
SOY nese onso cll To@ehe lols) acyl) exeyiy) sAroy) .04] .03 tr FO2 |e enone
BS Ole recites. care sf: On43|— 240 s2T oz) ear SPAT) meatal 216|2 205] 205) none
Nejeee cnet waiaye 4814 08), "07 : eel ere tr ir
SO eeicro 6 ate es SOG Zorvelllseersncas 07 .07 03 Bel toes © none
SO sealers: POA ee emonelie see Hi eee ays MOA 10 iets ee
COR ee Sita. ava oe |LOG) ais LS ASR 235 103]| NONE), Mone!) 2 a) none
diotalsen. 99.77/99 .70,99.70|/99.91\99.72|100.05|99.80|100.18|99.88)99.82|100. 31

H. N. Stokes, Analyst.

526, 525. Contact facies of granite mass, Red Mountains.

130. Diorite, Red Rock Creek, intrusive in batholith.

311, 623, 6, 989. Butte type of granite, Butte district.

98. Head of Clancey Creek, northern part of batholith.

518. Prevailing type of granite of batholith, Boulder.

640,951. Aplites of Butte granite, Butte.

The foilowing table shows the chemical composition of this
rock, only the essential elements being given, the complete analy-
sis being shown in the preceding table. Partial analyses of quartz-
monzonite from the Sierra Nevada‘t and of Brégger’s adamellite?
are given for comparison.

*H. W. TURNER: The granitic rocks of the Sierra Nevada, Jour. GEOL., May
1899, p- 141.

? Die eruptionsfolge der triadischer Eruptivgesteine bei Predazzo, p. 62.

740 WALTER HARVEY WEED
Quartz Monzonite} Granodiorite Adamellite
po Landsberg
t ; i
ae Siem aiNerni Pyramid Peak Vereen
Rosenbusch

Sip ieerccsveeteeeorsieiouss 67.12 66.83 67.45 68.97
INOS Ges eos a0.o586s 15. 15.24 15.51 14.80
(GENO aH aios Sareea 3.43 3.59 3.60 3.82
IMietOVeden caaoou one itey yal 1.63 1.10 1.15
ISON ican Conon oboe 4.52 4.46 3.66 4.53
Nas Ol eee Gig ye canoes 2.76 3.10 3.47 2.40

The close similarity of this rock to the quartz-monzonites of
the Sierra Nevada is apparent from these figures. It is evident
from the analyses that the Boulder granite nearly corresponds to
Brogger’s adamellite.

THE BUTTE GRANITE

The Butte granite (or quartz-monzonite) covers an area of sev-
eral square miles and is the prevailing rock of the Butte district,
and the one in which the world-famous copper and silver veins of
that place occur. It is, therefore, of more than ordinary interest,
and has been carefully investigated in connection with the study
made of the general and economic geology of the district. It is
a rather dark colored, coarsely granular rock which is seldom
seen in conspicuous exposures about the productive mines owing
to a close sheeting with much decomposition near the mineral
veins and ready disintegration in other parts of the district.
Away from the mineralized areas it is well sheeted and forms the
usual bowlder and castellated forms of such rocks. Its darker
tone and greenish feldspars render it easily distinguished from
the bowlder type. Throughout the entire district it is very uni-
form in appearance, as it proves upon analysis to be in composi-
tion, though differing somewhat in the relative proportions of
the constituent minerals. It is also uniform in grain over the
entire district, but hand specimens show in local patches a varia-
tion of textures. Inclusions of a much darker and finer-grained
dioritic rock are often seen weathered in relief on exposed sur-
faces ; they are always small, seldom over a few inches across,
angular and rather scarce, never making an appreciable part of

GRANITE ROCKS OF BUTTE, MONT., AND VICINITY 741

the mass. Owing to disintegration prefectly fresh specimens
can only be obtained from surface quarries or underground work-
ings. The exact relations of this mass to the general area were
not satisfactorily determined, though it appears certain from the
exposures that it is an integral part of the batholith and not a
separate intrusion. At several localities a sharp gradation was
observed, with narrow transition bands between the lighter
colored granite with its white feldspars and the darker Butte
type.

Orthoclase is an abundant and usually a readily recognizable
constituent as its pinkish color is in contrast to the green tones
of the plagioclase, and it has, moreover, a tendency to develop
in relatively large crystals which give the rock a somewhat por-
phyritic look. Plagioclase, black hornblende, black biotite, and
quartz are easily distinguished by the eye. Under the micro-
scope the rock is seen to vary between a rather basic hornblende-
granitite and a quartz-diorite. There is usually a slight amount
of chlorite present, but the biotite and hornblende are as a rule
fresh. Titanite, apatite, iron ore, and zircon are present as
accessories. It will be seen that the rock is only a somewhat
more basic phase of the granite of the region, and that it closely
resembles granodiorite, though in the Butte rock the plagioclase
is more basic, being a sodic labradorite. The four analyses given
in the general table show the rock to be remarkably uniform in
chemical composition over the entire area.

The following table gives partial analyses of the Butte granite
and of the related rocks from other localities :

PARTIAL ANALYSES OF BUTTE GRANITE AND RELATED ROCKS

aenuse) NGpeeen ORS aes Boulder

D1 Oseretes sitar 64.03 65.48 65.25 64.39 67.12
ANIEN @)rvecterietsie 15.58 16.05 16.94 15.90 15.

INS OW las Gnoe 1.96 1.47 1.60 5.63 1.62
He Oa as 2.83 3.02 1.91 222
Ca@ arte 25 x 4.20 4.80 3.85 4.15 3.43
WEROeatownia ae 2eTic 2.12 1.31 1.93 gy jal
KA Omer eae 4.11 6.8 2.43 2°02 SG) Ai52
Nias Olensercse: 2.7.0) ae 7 3.49 By/ 3.49 7.05 2.76

742 WALTER HARVEY WEED

The analysis of the Butte rock is the mean of the four
analyses already given. The granodiorite is the mean of five
analyses given by Turner. The Boise rock is described by
Lindgren.? The Banatite is a mean of the analyses quoted by
Brogger.3 From the analyses it will be seen that the rock closely
resembles a banatite in composition; the lime and sum total of
the alkalis being the same, but in the Butte rock the potash
exceeds the soda in amount. It also resembles the granodior-
ites, but the alkalies present an inverse ratio.

In order to furnish a basis for calculating the mineral com-
position of this rock, fresh rock was crushed, the hornblende and
biotite separated by Dr. H. N. Stokes by the use of Thoulet solu-
tion, and these two minerals from each other by sliding on
paper. The resulting material was examined under the micro-
scope and found to be quite pure.

The biotite is quite black in color to the eye, but dark brown
under the microscope showing very marked pleochroism. This
biotite is characteristic not only of the Butte granite but of the
Boulder granite as well. In many sections examined it appears
the same in color and pleochroism not only for the Butte rock
but for the normal granite of the batholith, and it may be
assumed to be the same for both these rocks. The microscopic
examination of the biotite material showed a little apatite pres-
ent, a very little chlorite, and very little hornblende, but these
impurities form a very minute part of the whole. The amphibole
is also characteristic of both the Butte granite and the normal
granite of the region. It is black or very dark green when seen
with a hand lens, but pleochroic in dark green tints with large
extinction angle when seen under the microscope. The mate-
rial analyzed was very pure.

The following table shows the result of the analyses made
of these minerals. Dr. Stokes was unable to obtain a higher

+ Woccit.5 ps 150:

? Mining Districts of the Idaho Basin and Boise Ridge, Idaho. Eighteenth Ann.
Rept. Director U.S.G.S. 1898, p. 740.

SWocrcit.; p. 62.

GRANITE ROCKS OF BUTTE, MONT,, AND VICINITY 743

summation in the analyses made of each, and the amount of
material available being exhausted further work could not be
done. For reference the analyses published by Turner of the
biotite and amphibole from the quartz-monzonite of the Sierra
Nevada, are also given.” The close resemblance of the analyses
of both rocks and minerals to those of the Butte material will
be noted.

Biotite Hornblende
Butte granite
Butte a Butte ee
SIO ea erm leeateratcnaee stove aie sars 35-79 25075 45-73 47.49 64.03
pli Oe Ger eanevate nev taker« cto fisecotens 2551 3.16 1.43 1.21 .60
le NOG eas cca Steir ROmIneeEre .10 .03 28 .06 .18
Bree steusa shaper ore slau ey Rndieusts. fe yh) Ly, staves bishus ec svettieits
Ci ce et npoialersensieciccettnn’s .20 Aree St seco UT Sess
AUIE Ole tcrettatvovae it stake tells oreisichacs 13.70 14.70 6.77 7.07 15.58
HO) Mectavcrstertiiacitre evacuate 522 4.65 4.94 4.88 1.96
Hie Oeeraerteys,, votcacnencutiolee aykcs E2972 14.08 10.30 10.69 2.83
IMGT OR verexacsveess a aa he eae .19 +45 54 ay Aig
Bia Ore etic wat hala ce eek weve eace 5g} ene none eats .07
WTO SvareseQetavaretesatevevoasrsteciisrteens none .12 none ae .04
CaO rites ccyar erence werent .05 oe], DZS T,02 4.20
VSO Perret io. dec Soe cay stasayaecaie 125 e377 12532 13.06 2.15
ARGS OW ersreetsheve, eeuciaeaoateharerd a 9.09 9.19 1.22 -49 4.11
AN as) eee prada ceu te eececs readies ays 15 fee “yfyf 75) 2.76
NE UNO) ice Pia kaye wtesigeia acs)vis ohavess tr tr tr aa Pera
Tel OR below DLOg ea scec ee 120 1.03 -49 oe .20
He OsvabovesllOr feos aac 3.64 3.64 220 1.86 auf}
MO talietecscvenete ese cesree Pais 99.59 100.00 98.77 100.03 99.87
TeessmOsforsH Ga Glee eo 27 12
99.22 98.65
Stokes |Hillebrand| Stokes |Hillebrand Stokes

The Butte analyses are incomplete as the amount of material was too small for
further work.

The phosphoric pentoxide (P,O,;) in the analyses of both
minerals and of the rock itself is assumed to be present as apatite
and with an appropriate amount of lime is deducted from the
analyses. The water below 110° C. is assumed to be accidental
and is also deducted. The analyses are then reduced to 100,
and the molecular ratios calculated.

t Some rock forming biotites and amphiboles. A.J. Sci. Vol. VII, 1899, p. 294.

744 WALTER HARVEY WEED

All the soda is calculated as albite. Microscopic examina-
tion shows the plagioclase to bea calcic andesine Ab,, An,, and,
an estimate being made of the proportion of hornblende present,
an equivalent amount of lime is deducted and the remainder
calculated with the albite molecule to form plagioclase.

The result gives the following composition for the rock:

I Il

Quartz - - - - BETO) 20.8

Orthoclase - - - - 19.88 18.

Albite - - - - 22.98 28.

Anorthite - - - - 11.48 TQ

Hornblende - - - 15.26 16.6

Biotite = - - - - a Ano —

Magnetite - - : - 1.18 1.5

Titanite - - - - - .97 1.4

Apatite = = 3 : +33 3
100.00 98.7

This adds up to 1.51 molecular weight against 1.50 for the
bulk analysis of the rock, showing a very close agreement. As
the microscope shows the plagioclase to be andesine of about
the composition of Ab,, An, (or Sodic labradorite), and albite is
not seen in the section, the orthoclase must contain the albite
molecule. In the second column the percentages given are
those calculated by Lindgren* for the granodiorite of Grass
Valley—a rock whose chemical analysis, as already shown, closely
resembles that of the Butte granite.

The rocks in the vicinity of the Frohner mine are identical
in composition with the Butte granite, as shown by the analysis.
The region is about thirty miles north of Butte, and the rock
part of the general granite batholith.

THE BLUEBIRD APLITE

Associated with the Butte granite there is an unusual devel-
opment of aplite. So far as known to the writer it is the most
extensive occurrence of a granite aplite yet discovered. The

* Gold Quartz Veins of Grass Valley, Cal., Seventeenth Ann. Rep. Dir. U. S. Geol.
Surv., p. 42.

GRANITE ROCKS OF BUTTE, MONT., AND VICINITY 745

largest mass is 114% miles by 2,, miles, and is known from mine
workings to be several hundred feet thick, resting on the Butte
granite. Besides this large mass there is another of about one-
third the size and numerous smaller bodies, as outlined by the
author on the geologic map of the Butte district. In the cases
hitherto observed by the writer, and those commonly described,
aplites occur in dikes commonly quite narrow, but often of con-
siderable length; such masses have been supposed to be the fill-
ing of cracks formed in the cooling granite, the aplite magma
coming either from an acid residuum or nucleus of the mass or,
as suggested by Turner, a product squeezed out of the crys-
tallizing granite and gathered in cracks due to its shrinkage. A
study of the Butte aplites shows that, though the dikes of this
material may owe their origin to some such cause, that the irregu-
lar lense-like or meniscoid masses are sometimes local bodies
unconnected with any feeder. The inference derived from a
careful examination of many exposures is that the material is
due to some such process as that suggested by Turner—a sort
of segregation. In the description of the remarkable differen-
tiation zone of Square Butte’ it was shown that the basic outer
part of the intrusion, itself a product of differentiation, holds a
thin band of white syenite due to further separation or differen-
tiation of the feldspathic constituents in the crystallizing mass.

This hypothesis, my belief in which has been strengthened by
further observations of other laccoliths in the same region, seems
to explain the manner of occurrence of the aplites in the Butte
mass. It is believed, upon evidence which cannot be presented
here, that the Butte district is on the downthrown side of a fault
and that its granitic rocks represent the upper part of the batho-
litic intrusion. In this uppermost part of the intrusion partial
differentiation is believed to have taken place, the normal granite,
represented by analysis No. 516, splitting up into the more basic
phase represented by the Butte type and the acidic type, the Blue-
bird aplite. This hypothesis demands that as the Butte granite

* WEED and Prrsson: Highwood Mountains of Montana, Bull. Geol. Soc. Am., p.
406, 1896.

746 WALTER HARVEY WEED

is but slightly more basic than the prevailing form, the pro-
portion of aplite should be small. The field observations show
a quantitative relation which, as far as it can be estimated, con-
firms the view.

This -hypothesis implies a gathering of the iron, magnesian,
and lime molecules out of the general magma and their concen-
tration in the quartz-monzonite, with a separation out of the
aplitic material, richer in alumina, alkalis, and silica which did not
form an inner kernel as it has in laccolithic differentiations, but
local masses in the basic granite. This hypothesis has already
been anticipated by Cross in the discussion of evidence of dif-
ferentiation at Rosita, Colo.?

If the Butte granite is a border or upper contact facies of
the batholith, this separation may have been induced by contact
cooling. Observations of many of the smaller intrusive stocks
of the Montana mountains and of the contacts of the larger
batholiths show that there is more or less of a mixing of basic
and siliceous materials as if they were stirred together while
pasty. The rocks grade into one another and there are no sharp
contacts.

In the large aplite intrusions there is no sahlband alteration.
The grain continues the same in both rocks, but at a certain line
there is a change in the relative proportions of the minerals. In
the smaller bodies and little dikelets the grain of the aplite is
finer, though there is no contact band or evidence of chilling.
In the Butte area this is uncommon. There is, it is true, a sharp
contact between granite and aplite, but there are transition forms
and even masses of granite in the larger aplite bodies which are
clearly not included fragments but integral parts of the mass.
Yet there is commonly a definite separation of the two rocks,
and it is certain that there has been no mixing of the two mate-
rials due to convection or movement before consolidation.

In most of the aplite bodies the grain varies considerably from
place to place; sometimes the rock becomes a micropegmatite,

* Geology of Silver Cliff and Rosita Hills, Colo., Seventeenth Ann. Rep. Dir. U.S.
Geol. Surv., p. 329.

GRANITE ROCKS OF BOTTE, MONT. AND VICINITY F477

rarely a coarse pegmatite. There is sometimes a banding with
alternations of fine and coarse-grained material.

The commonly accepted theory of the origin of aplite is
that it represents the acid remainder in a granite or quartz-
diorite magma after the more basic elements have crystallized.
At a late period, after the main mass of the granitoid rock had
crystallized, the aplite is forced up from below and fills previously
formed cracks, which are perhaps the result of cooling. Viewed
in this light they are genetically related to the more basic
granites with which in the Sierra Nevada they are for the most
part directly associated."

The aphte-——The following calculation of the mineral com-
position of the aplite, column I, is based upon the complete
chemical analyses given in the table. A little biotite is found in
the fresh aplite. This is similar to that of the granite and is
supposed to have the same composition, and all the magnesia is
ascribed to this. This leaves an excess of 0.09 of TiO,, which
is calculated as titanite.

I i!

Quartz - 3 = : 37-70 39-45
Potash feldspar - - = 333.00..." 29.43
Soda feldspar - - - Bro 23°03
Lime feldspar - - 2.45 6.56
Biotite - - - - 0:72 .9O
Magnetite, etc. - - Sy exo 58
Titanite - - - - 0.22 18

100.00 100.00

In column II the mineral compositions of the aplites of the
Granodiorite of the Sierra Nevada, given by Turner, are given
for comparison.

LAMPROPHYRIC CONTACT FACIES

The first two analyses in the large table represent the compo-
sitions of two lamprophyric contact facies of the batholith. The
rocks probably grade into the granite, though the transition is a

TH. W. TURNER: Geology of Sierra Nevada, p. 722.

748 WALTER HARVEY WEED

rapid one. More often such rocks occur as intrusions in the
altered sediments about the border of the batholith. The first
analysis is that of a rock that might be called a diorite, though it
hardly comes under that name. It consists mainly of green horn-
blende, which is stringy and appears to be derived from augite,
and of small zonally built basic plagioclase feldspars and a very
little quartz. It is a nearly black, quite coarsely crystalline rock,
and is an unusual type. It occurs intrusive in phyllites and
schists on the summit of Red Mountain, ten miles south of
Butte.

The second analysis is that of a rock fairly typical of the
batholith contact at many localities. It is a dark gray granular
rock, rather finer grained than the granite into which it can in
some places be traced by insensible gradations. It is a very
basic diorite which approaches a hornblende-gabbro. The horn-
blende is quite stringy and of uralitic appearance, pale green
passing into deeper green and into colorless forms. Brown bio-
tite is rare. Orthoclase is present in small amount and only in
interstices between more idiomorphic plagioclase. The latter
shows an extremely fine zonal structure and varies between
labradorite and albite, and will perhaps in a majority of cases
have an average composition corresponding to andesine. A very
little quartz is also present, together with apatite and iron ore
as accessories.

The rock grades into one consisting mainly of zonally built
basic plagioclase in small idiomorphic crystals, equal in amount
to that of the combined dark colored constituents, brown pleo-
chroic biotiteand hornblende derived from light colored pyroxene,
remnants of which still remain.

For the purpose of determining what changes, if any, are
accomplished in the ordinary weathering of the granite, an analy-
sis of a coherent but quite triable rock has been made. The
material, which is quite typical of that commonly seen in natural
exposures, is rather lighter in color than the perfectly fresh rock
and has a clayey odor when moist. The greenish plagioclase
and pinkish feldspar has been bleached to a dull white or waxy

GRANITE ROCKS OF BUTTE, MONT., AND VICINITY 749

tint. In the still more altered rock, and in the sands formed by
its crumbling down, the white minerals are stained by iron rust.
In the rock analyzed the biotite is partly fresh and unaltered, but
many of the grains are dull and lusterless, and others are altered
to green chlorite; more rarely the cleavages are coated by iron
rust. The hornblende shows the most alteration. Some of the
grains are fresh, but most of them show masses of ocher, and
are penetrated by films of it along cleavages and the grains all
show more or less chlorite as the first stage of alteration. These
changes all indicate simple hydration and oxidation of the rock,
and should accordingly be revealed in the analysis. The fol-
lowing tables show (1) the average composition of the fresh
rock, (II) the composition of the disintegrated material, (III)
the percentage of each constituent lost, (eDN/3) the percentage of
each constituent gained.

Constituents I II II Vie ere oie
error of analysis

SHNCE Sedo or s5|04-03 65.14 +1.01 1.41 3
Titanic oxide...| .60 59 —0.01
Alumina. .!5... 3 15.58 15.63 +0.05 0.32
Herricoxide, 3. ..)| 0.90 2.37 0.51 oT
Ferrous oxide...| 2.83 2513 —0.70 15
Manganese oxide] .1I1 tis Onli 100. 10.
BTM ese atsresiietanens 4.20 3.62 —0.58 14.09 I
Magnesia ...... 2eris 1.85 —0.30 14.23 7)
Botashevncrce ws. 4.11 4.29 +0.13 4.04 2
SOda ttc pra ct oes 2:76 2.63 —0.13 9.51 2
M oisture com-

bined espera. 73 apis +0.02
Moisture below .96

TT Os, otenentsiers PA) 5ey7/ +0.14
Bary tavctsesetena ae .07 .I0 +0.03
SUrOMELA ves eee C4 tr. —0.04
Phosphoric acid.| .18 .16 —0.02

99.86 99.08

The fresh rock contained a little Cl, 0.17 per cent., the dis-
integrated rock none. The fresh rock held 0.06 per cent. S (as
pytite), the altered reck 0.05 per cent. SO .

While the changes in the character of the rock are largely
physical, and its degeneration, due to the rapid expansion and

750 WALTER HARVEY WEED

contraction to which it is here subjected in the extremes of tem-
perature that are so characteristic of the climate, and the chem-
ical changes made possible because of the opportunity for
moisture to penetrate the minute cracks thus formed, yet the
chemical changes themselves, slight as they appear to be, aid this
degeneration by swelling up as the molecules become oxidized
and hydrated.

The analysis shows a remarkably small amount of chemical
alteration. It is evident, also, that the process is not the normal
one of ‘‘weathering,” since silica is not lost. The presence of
sulphides in the rock itself, the proximity of mineral veins, and
the presence of sulphurous fumes in the atmosphere which would,
of course, acidulate the rainfall, probably account for this
abnormal nature of the weathering. Under such circumstances
none of the constituents of the rock are constant, since they are
all capable of passing into solution under such conditions. As,
however, an increase of silica could not take place, this sub-
stance must either decrease in amount, or remain constant, and
the analyses can be best compared by assuming it constant.

WALTER HARVEY WEED.

Nez

AN ATTEMPT TO FRAME A WORKING HYPOTHESIS
ORI Ea CAUSE OR GLACIAL, RERIODS ONAN
ALPVMOSEHERIC- BASIS.

(Continued)
ro:

LOCALIZATION OF GLACIATION.

THE problem of localization is in some sense independent of
the fundamental hypothesis offered in this paper, and the sug-
gestions which follow may be accepted or rejected without
carrying necessarily an approval or disapproval of the main
hypothesis.

The remarkable distribution of the great ice-sheets —The chief
centers of the Pleistocene ice-sheet lay on the north-northeastern
plains of North America, and, on the northwestern quarter of
Europe. On the northwestern Cordilleras there was also a nota-
ble center, though it does not appear to have equaled the others
in rank.‘ The north-northeastern American centers are properly
regarded as chief because the spread of the ice-sheets from them

t This statement is perhaps open to some question. It is quite certain from field
observations that the glaciation of the Cordilleran plateau in the United States and
in British Columbia as far north at least as 51° Lat. was much feebler than that of the
Mississippi basin at corresponding latitudes and much lower present altitudes. It
seems also clear that the ice of the north Cordilleras did not creep out upon the plains.
to an extent at all comparable to the spread of the Scandinavian ice-sheet upon the
plains of Europe. Considered from these points of view, and they seem to be the
important ones, the statement can scarcely be questioned seriously. The evidences
of glaciation on the mountainous border facing the Pacific from 48° northward arts,
however, quite impressive. They find their climax perhaps in the 4000 or 5000 feet fof
glacial! débris which Russell reports in the foothills of the St. Elias range. In v 4ew
of this it may perhaps be insisted that the glaciation of this region was ex bep-
tionally concentrated on the Pacific border, because of the abrupt rise of the sur ‘face
and the height of the mountains, and that the glacial discharge toward the * Pacific
was also exceptionally effective because the high gradient; so that, tak dng this
intensification into account, the sum total of ice formation and ice action in ‘his region
may not have been so much inferior to that of the European area as the /surface dis-
tribution might seem to imply. a

751

752 T. C. CHAMBERLIN

was much more extensive than from the other centers, and
because they were not aided essentially by mountainous points of
origin, for neither the Labradorean nor the Keewatin centers
appear to have been initiated by mountainous elevations. It
was a development of glaciation on plains, or at most on plateaus.
This fact renders the American ice-fields conspicuously chief
among all that developed in Pleistocene times. The glaciation
of Europe was centered upon mountains; and remnants of
glaciation still linger on the mountain heights of most of the
old glacial fields, giving ground for the belief that the local
topographic features were there important factors. The glacia-
tion of northwestern Europe would possibly have been rather
scant if it had received no greater topographic aid than was
afforded in the Keewatin field, but apparently it would not have
been absent.

It has often been remarked that the Pleistocene glaciation
was gathered about the north Atlantic, but it can scarcely be too
much emphasized that the greatest, of the glacial areas, and by
far the most phenomenal, because of its plain topography, lies
on the western, or what we are accustomed to regard as the
windward, side of the Atlantic.

It is further to be noted, that on the western side of America,
the glaciation, though notable, was still seemingly much inferior
to that of the great northeastern plains; and this in spite of its
mountainous character and its adjacency to the great Pacific
Ocean, a topographic and hydrographic conjunction which
expresses itself now in the most vigorous glaciation outside of
the polar circles.

More or less nearly contemporaneous with the growth of the
foregoing great ice-sheets, local glaciation developed on nearly
all the mountain heights of the earth, whether in the northern
or ‘the southern hemisphere, and whether in high or low latitudes.
Thi’s seems to imply an intensification of glacial conditions gen-
erally, but at the same time to indicate that the great ice-sheets
were depyendent on some special agency of localization. In say-
ing that tilcese scattered areas of glaciation were approximately

PiVEROd EH SITS (OF CAUSE VOM GLA CIAL PERIODS —7.53

contemporaneous, no dogmatic assertion is intended relative
to the exact contemporaneity of glaciation or to its alternation
in’ the northern and southern hemispheres, nor respecting the
doctrine of migration of glaciation in longitude. Observational
data are yet insufficient to decide these questions. It is obvious,
however, that the hypothesis under consideration postulates
essential contemporaneity throughout the globe.

The constructive pole of the winds.—As a possible factor in the
localization of glaciation, I venture to offer the suggestion that
the axis of the earth’s rotation and the axis of the atmosphere’s
circulation, constructively interpreted, are not identical. By the
constructive axis of the winds I mean that ideal line about which
the general currents of the atmosphere would be found to
revolve if all minor movements were eliminated or equated and
the aggregate east-west components only were regarded. In
other words, it is suggested that the planetary system of circu-
lation is obliquely adjusted to the planet. This was first sug-
gested to me by a study of the peculiar courses of the arctic
ice-drift. The polar ice-bearing currents are regarded by experi-
enced arctic navigators as concrete expressions of the average
movements of the atmosphere. To be sure, the ice-drift is
affected by the ocean currents, but these are also, in the main,
the, results: of the average direction and force of the winds,
though they do not so immediately and definitely express it as the
ice-drift, because they are also influenced by more remote agencies.

If the axis of the currently postulated ‘circumpolar whirl”’
of the atmosphere coincided with the axis of the earth, and if it
were the poleward incurving spiral of the winds that swept the
surface of the polar sea, the average ice-drift should assume, or
tend to assume, a corresponding incurving spiral. The ice should
crowd in toward the pole and rotate upon itself in a direction
opposite to the hands of a watch. If this were true, the current
which carried Nansen from east to west should have flowed from
west to east.

If the axis of the ‘‘circumpolar whirl” coincided with the
axis of the earth, and it were the outward-running spiral that

754 T. C. CHAMBERLIN

swept the surface of the sea, the ice-fields should rotate in the
opposite direction with a centrifugal tendency which should carry
the ice outwards and press it against the adjacent continents and
give a voluminous discharge down the north Atlantic. An
attempt to drift foward the pole in such a system would be an
absurdity, and Nansen’s feat would be inexplicable.

Observed ice-drift—Neither of these are the phenomena
observed. On the contrary, as now abundantly demonstrated,
particularly by the remarkable drifts of the Jeannette and the
Fram, the average movement near the coast of northern Asia
and Europe is westward and slightly northward. This course
is held until Greenland imposes itself as a barrier. The outer
margin of the ice flow is then forced southward, but immediately
it reaches Cape Farewell it curves closely about the point (at least
during the summer months) and flows northward and westward
to the vicinity of the arctic circle. It here encounters a new
barrier in the islands of the American Arctic Archipelago and
again moves southward.

On the north coast of Greenland, so far as known,. the ice
presses hard upon the land, as though its normal course were
southward. It flows persistently into the channel between Green-
land and Grinnell Land, and gives rise to that strenuous ice-pack
which has again and again been assailed by arctic navigators
with such great daring and such little success. The recent
adverse experiences of the Windward and the Fram are but a
renewed expression of the persistence of this south-southwestward
drift of the ice. currents:

On the north side of the Arctic Archipelago, west of Green-
land, the ice crowds hard against the shore, and has thus far pre-
vented the full penetration of Jones Sound or any of the other
straits between the northern range of islands. The blocking of
Jones Sound appears to be the result of an eastward as well as
southerly crowding of the ice.

Farther to the west Banks Strait and McClintock Chan-
nel together form a continuous and rather broad water way,
beginning in longitude 130° west and stretching southeasterly to

HVPOTHESIS OF CAUSE OF GLACIAL PERIODS ~*~ 755

longitude 95° west. This channel is always tightly jammed with
ice pressed in from the northwest. So persistent and strenuous is
the pressure of this ice-pack that it constitutes an effectual barrier
to the northwest passage, and has thus far mocked all attempt to
force it. This implies a definite and persistent movement from
the northwest to the southeast.

It appears, then, that from far east of Greenland to the west-
ern limits of the northern archipelago there is a definite con-
vergence of the ice currents toward a point located somewhere
north of Hudson Bay, 7. e¢.,a point lying to the north of the
two great centers of Pleistocene glaciation, the Labradorean and
the Keewatin, and on a meridian that runs between them.

It is interesting to note that the point of convergence lies in
the general vicinity of the magnetic pole. and this: obviously
leads to the further suggestion that there may be some genetic
connection between the two as yet undetermined.

Concurrent in import with this is the fact that on the opposite
side of the north pole the coasts of northern Asia and Europe
become partially free of ice each season. This, although doubt-
less partly due to the effects of the fresh water borne in by
the great rivers of those coasts, is probably none the less an
expression of the fact that the polar ice is not crowded down
upon those coasts; for if it were, its great mass would com-
pletely overwhelm the effects of even the great Siberian rivers.
This phenomenon, taken in connection with the direct observa-
tions of the ice-drift made by De Long, Nansen, and others,
leaves little room for doubt that the great polar ice-field drifts
away from the Eurasian coast and crowds toward Hudson Bay.
The meridian of 90° may be taken as rudely representing the
axis of this converging ice-drift. It is interesting to note that
this same meridian bisects the Mississippi valley and crosses the
southern apex of the great American glacial field.

Listribution of arid zone.— Correlated with this remarkable
phenomenon is an equally remarkable distribution of the great
desert tracts of the eastern hemisphere. Commencing on the
Atlantic coast of Africa between 10° and 30° north latitude, the

756 T. C. CHAMBERLIN

arid belt stretches north of east across Africa and Asia until in
Mongolia it lies between 30° and 50° north latitude. That is to
say, in this stretch of 70° or 80° in longitude it has advanced
20° in latitude. If now we select the meridian at 90° east, at
or about which the desert area reaches its northern culmination,
and follow this through the pole to a point 20° beyond on the
meridian of 90° west, we are in the vicinity of the point towards
which the arctic. ice-drift seems. to ‘concentrate. | And ai we
follow the same meridian southward we reach the point in the
Mississippi valley where the ice-sheet had its southernmost exten-
sion. It is to be noted further that this last point coincides
with the region where a large percentage of the cyclones which
descend from the northwest curve about and take northeasterly
courses.

If there were space here to enter into other particulars, addi-
tional coincidences of an apparently significant nature might be
found. The inference drawn is that the axis of the main polar
whirl, if indeed the polar movement can be called a whirl, is not
coincident with the axis of the earth, but hes at some point
southward from it in the vicinity of the meridian of 90° west
longitude and 20° more or less distant from the pole.

Indications of meteorological data.— As just implied, the idea
entertained is not that there is a simple polar whirl whose axis
is located here, but that the rather complex movements of the
polar atmosphere, when combined and correlated, give a theo-
retical or constructive pole in this region. What is meant by
this will appear more specifically from a study of the available
meteorological data. Unfortunately these are yet quite imper-
fect and’ partially uncorrelated, and hence I have given prece-
dence to the natural correlation expressed in the ice-drift. The
International Circumpolar Commission has not yet combined
and discussed its data. It may therefore be most convenient to
have recourse to Buchan’s’ or Hann’s? meterological maps. for

™Challenger Reports. Physics and Chemistry, Vol. 11, Atmospheric Circulation.
Maps 51 and 52. These include the main data gathered by the International Circum-
polar Stations.

? Berghaus Physical Atlas.

TIMPOLHESLS OF CAUSE OF GLACIAL PERIODS Th

the general features of atmospheric pressure and circulation.
An inspection of Buchan’s isobaric maps shows that there are,
north of 45° north latitude, two nearly permanent areas of low
barometer and one of f#zgh barometer. (See accompanying
sketch maps I and 2, based mainly on Buchan’s.) The area of
high barometer is located in Asia on the meridian of 100° east
longitude. It may perhaps be regarded as one of the normal
high areas that theoretically belong to the parallel of 30° north
latitude, but which has been displaced 20° to the northward by the
topographic conditions of the great Eurasian continent. Its two
chief companions under this view lie, the one in the east Atlantic
centering near the Azores, about 30° north latitude and 25° west
longitude, the other in the east Pacific, off the coast of Califor-
nia, in about 35° north latitude and 140° west longitude. But
the Asiatic area of high pressure seems to combine in itself also
the function of a polar center, for no other center, high or low,
lies between it and the pole. Moreover, it is above mid-lati-
tude, and is nearer the parallels of the two permanent areas
of low pressure of the arctic region than to those of its 30° cor-
relatives, for it lies itself in 50° north latitude, while the arctic
“lows” lie in 55° and 60° north latitude respectively.
Furthermore, as shown on Buchan’s map 52, these high-lati-
tude centers are arranged about the pole at nearly equal distances
from each other, the’ Asiatic ‘high’ being: in about 100° east
longitude, the north Atlantic ‘‘low” in about 35° west longitude,
and the north Pacific ‘‘low”’ in about 170° west longitude, z. ¢.,
their successive distances from each other. are.135°, 145°, and
140°. While these centers shift somewhat during the seasons,
they are essentially fixed, the above statements being based on
the isobaric averages for the year. These centers are therefore
to be distinguished from the familiar moving cyclonic centers
and are to be regarded as enduring factors which express the
essentially permanent circulatory features of the circumpolar
atmosphere. The Asiatic ‘‘high” is a permanent anti-cylonic
area characterized by descending outward-flowing currents,
attended by low precipitation and clear air. The north Atlantic

CHAMBERLIN

Die

58

i.

"NVHa@NG wats
‘UYIA SHL
vos 38079 3H41 40
S3NI7 JIYVEOSI

HVPROTHESTS OF CAUSE OF-GLACIAL PERIODS. 7559

G:

KOT

760 LT... Ci CLLA MBER,

and north Pacific ‘‘lows”’ are permanent cyclonic areas with
inflowing ascending currents attended by high precipitation and
prevalent fogs.

Of the two “‘lows”’ that of the north Atlantic is the broader
and more northerly, and appears to be the more influential factor
now, as presumably it was in Pleistocene times. The north
Atlantic ‘low,’ according to both Buchan and Hann, centers
near the apex of Greenland; the north Pacific “low” centers on
the Aleutian islands.

It is not difficult now to understand the peculiar behavior of
the ice-driit “of the’ polar seas, Bhe Asiatic: “hich jwithweies:
outflowing currents pushes the ice off the Asiatic coast, while
the currents inflowing toward the two “lows”’ impel it toward a
point between the two. The Asiatic “high,” however, develops
more to the northeast of its center than to the northwest, and
the North American area of moderately high barometer extends.
a tongue to the northwest between the two ‘‘lows,” so that the
two high areas approach each other north of the north Pacific
“low” and reduce its influence upon the high latitude currents.
These are therefore directed disproportionately toward the north
Atlantic ‘‘low,” and give to it a dominating influence. Buchan’s.
maps of wind-directions for the winter months (when local influ-
ences are reduced to the minimum) show that the prevailing
wind currents flow concentrically about the north Atlantic center
from the Lena on the east to the MacKenzie on the west, a stretch
of 220° longitude.

Correlation of circumpolar currents.—But in considering the
circumpolar circulation as a whole, it is necessary to combine all
the movements about all these centers to find the true dynamic
center or the constructive pole of the winds. While such a com-
bination cannot be accurately made from present data, it is
obvious that it must place this constructive pole somewhere to.
the northward and westward of the north Atlantic “low” and
nearer to it than to either of the other centers.) he jpome
toward which the ice-drift converges satisfies these conditions,
and may be taken as nature’s own practical correlation. Possibly

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 701

the magnetic pole may prove to be another expression of the
same correlation, made indirectly through the agency of electric
and magnetic dynamics springing from atmospheric circulation.

One-stded location of ‘‘ lows.’’—As already noted, the two areas
of permanent low barometric pressure are located on the Ameri-
can side of the globe and have their centers, according to Hann
and Buchan, less than 140° Long. (5 of the total 360°) apart.
They are notably elongated in a general east-westerly direction,
the north Atlantic area being especially extended easterly and
northeasterly, and somewhat curved and reniform. If the iso-
baric line of 29.95 inches, which represents the average pressure
for the globe, be taken as defining the low areas, their borders
are only about 4o° Long. apart on the American side, while
they are 115° Long. apart on the Asiatic side in about the same
latitude. In other words, the distance between the borders of
the low areas on the American side is about one third of the
distance on the Asiatic side. The distance between the borders
of the ‘‘lows” is only about one half their own longitudinal
diameters. The tract between the borders of the “lows” on the
American side being thus relatively narrow, it might naturally be
anticipated that the currents within it would be much influenced
by those of the adjacent depressions, and this seems to be ina
large measure realized, for the winds on the northern American
plains east of the Rocky Mountains flow in the main concentric
to the north Atlantic depression. On Buchan’s map 52, which
has a polar projection, the isobaric line of 30 inches describes.
nearly a circle about a point not far from the center of Green-
land’s ice-field. (See sketch map 2.) In a rude way the pre.
vailing winds within this circle and for some short distance
without it whirl about the Greenland center with inward tend-
ency. The influence of the north Pacific depression does not
appear to be appreciably felt east of the mountains.

Relation of moving cyclones.—Ilt is interesting to note in this
connection that many of the moving cyclones that traverse the
mid-latitudes of our continent seem to take their origin in the
tract between these two permanent cyclonic areas, or in the

762 TEC GHA MELE TRIETEN,

region immediately to the south of it, and that possibly they are
but secondary eddies generated by the action of the great fixed
ones. As before noted, the migrant eddies swing concentrically
about the north Atlantic depression.

Location of present glaciationn—Coming closer home to the
glacial problem, it is important to note that the two great areas
of present arctic glaciation are intimately related to these two
permanent cyclonic areas. The Alaskan and Greenland ice-
fields not only lie within these areas of barometric depression,
but are peculiarly related to them. It is, at first thought,
not a little singular that, while the Alaskan ice-fields lie on the
northeast border of the Pacific ‘‘low,’’ the ice-fields of Greenland
lie in the northwest quarter of the north Atlantic “low;”’ that ts,
the chief glaciations lie defween the centers of the two permanent
cyclonic areas. The apparent anomaly of maximum ice accu-
mulation in the northwest quarter of the Greenland “low” prob-
ably finds its explanation in the following considerations :

1. The maximum precipitation (which is normally found in
the southeast quarter of a “low”’) and the maximum ice accumu-
lation should not theoretically be coincident; for the ice accu-
mulation is not a true measure of the precipitation, but merely a
measure of that fart of precipitation which is frozen when it
falls and survives melting and evaporation. Now in the north
and west quarters a larger percentage of the precipitation is
snow than in the south and east quarters, where the sum total of
precipitation is greater. Moreover, the melting in the north
and west quarters is obviously less than in the opposite quarters.
The annual isotherms for the southeast quarter range from 35°
up to 50° F., while those of the northwest quarter range from
35° down too’ F. The ice-fields of Greenland and the lands
west of it lie in the tract whose annual average is below 32° F.
Iceland, whose precipitation is greater, but whose glaciation is
less, lies between isothermals 35° to 40° F.

2. The configuration of the water area which wraps about
Greenland gives special snow-precipitating efficiency to the
winds that swing about the depression on its north side and

HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 763

cross Greenland from the east and northeast. The nature of
the circulation ts such that Greenland 1s really on the leeward side of
the north Atlantic. This is shown by the following tables of pre-
vailing winds. The first is from the prolonged observations
recorded at Godthaab and Upernivik, by Dr. Rink; the second,
from those taken under the direction of General Greeley at Fort
Conger in the years 1882 and 1883:

PERCENTAGES OF TIME DURING WHICH GREENLAND WINDS BLOW
FROM THE DIRECTIONS NAMED

At Upernivik At Godthaab
Lat. 72° 47’. Long. 55° 35’ Dat, 64° 2x". “Long, 51.43"
Direction Winter Spring | Summer | Autumn Winter Spring | Summer | Autumn
ING ereistia or 25.5 33.9 31.9 28.8 B21 37.4 30.3 25.5
ID eesactetewead 34.3 2251 16.2 36.5 38.4 24.8 8.6 33.6
Shear tresctacel| Lige5 20.3 28.0 18.1 16.1 ey) 32.9 22.9
Was) cess wns 1.8 2:5 6.4 4.4 4.9 5.7 15.1 6.2
Calms). ..2: 22.9 20.2 1725 12.2 7.5 10.4 eel 11.8
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

FREQUENCY AND VELOCITY OF WINDS AT FORT CONGER,
LAT. 80° 44’ N., LONG. 64° 45’ w.

1881-2 1882-3
Direction

Times Miles Times Miles
IND epefet oekestrcnnkerestesetsnaa ees 303% 1522 420 2401
Ni Ete Latent cst avs laces 761 3061 1022 4613
NEP ein, etersea ie ea ta hrscen ovate hays I151% 4843 1369 4061
S aE toners ees aave ree 67814 3605% 862 3650
DORs eesti Oa mah cnet acta ™uleielels 683% 386414 775 4214
Sr Wisi tee sie penten ait at sveaae ails tes 678 2011 goo 3059
AV iWeeneek te etree cng teaver eaa 371 949 343 997
INEM icite, cay teaiofoisetenadare. Cat ns 206 720 387 1142
alma eens, eh cer tan fone capstan Gistenecs 3408 1282 26082 50

The winds of the summer months are much influenced by
local features, especially by the sea, the naked earth and the ice
fields, respectively, while in the cold months a nearly uniform
mantle of snow or ice covers the whole surface in common, and
removes essentially all sources of variation except those of

764 T. C. CHAMBERLIN

relief. Including the data of the summer months, the prepon-
derant direction is shown by the above tables to be easterly.
Omitting them, it becomes northeasterly. But in either case
the dominant winds come from the north Atlantic, and justify
the statement that Greenland is on the leeward side of the high
north Atlantic and the adjacent part of the Arctic Ocean.

In the eastern part of the Arctic Archipelago as far south as
Hudson Straits the winds are very variable, a fact quite con-
sistent with their physiographic surroundings, and with their
location well toward the interior of the north Atlantic depression.*

The paths of the moving cyclones— Besides the general fact
that the prevailing atmospheric currents from the Mackenzie to
the Lena form a great eddy, with maximum conditions of
glaciation on the north and west of its chief center near the apex
of Greenland, it is to be noted that the paths of the moving

”

“lows” are greatly influenced by the permanent depression at .
the center of the eddy. This is graphically shown for the north
Atlantic portion of the region by Hann’s map No. 367 herewith
reproduced (sketch map 3), in which it is shown that nearly all

)

the moving ‘‘lows’’ curve to the northward in courses more or
less rudely spiral or concentric to the permanent ‘low.’ The
larger number of paths run spirally in toward the permanent center,
which suggests the conception that the great fixed cyclone is in
some sense an aggregate of numerous small in-running migrant
cyclones. If data were sufficient to permit the following of
the complete courses of all the migrant cyclones from their origin
to their extinction, a dominant system of great interest would
probably be shown. As already remarked, a considerable num-
ber of these migrant cyclones originate in the American north-
west. These show a notable habit of sweeping southeasterly

‘IT am greatly indebted to the Hon. Willis L. Moore, Chief of the United States
Weather Bureau, and to Professor R. F. Stupart, of the Canadian Meteorological
Service for transcripts of data relative to various high latitude stations not otherwise
at my command.

-? Berghaus’ Physical Atlas.

3The North American continent is the region where cyclones form in large
numbers, and Europe and Asia the region where they dissipate.” F.H. BIGELOW:
Am. Jour. Sci., Vol. VIII, December 1, 1889, p. 443.

HWVPODBHMESLS (OF..CA OSE OF GLACIAL PERIODS 765

Y,

CAMP. NG
fe

Cie

:
Shas ¥ , v
RZ, LS
bes ERT.
X 2
} e RA 4 ANA

766 T. C. CHAMBERLIN

into the Mississippi Valley, where they curve about and follow
the courses shown on Hann’s chart. These courses seem to fall
into two classes, the one running spirally inward toward the center
of the great fixed eddy, the other spirally outward with dispersive
tendencies. A suggestion relative to the possible reason for
this last feature will be given in another connection.

A more general view.—While all generalizations now enter-
tained must be held very tentatively, because of the imperfection
of present data, a general conception of the circulation of the
northern part of the northern hemisphere, which will serve to
bring together and give coherence and unity to the more special
features which have been discussed, may be pardoned.

The whole temperate and polar region is divisible into areas
of high pressure (annual average above 29.95 inches, 760 mm)
in which the dominant currents are downward and outward, and
areas of low pressure (annual average below 29.95 inches, 760
mm) in which the dominant currents are inward and upward.
The mutual disposal of these gives a basis for a general view of
the atmospheric circulation.

The high pressure loop.—tIn tracing the former we may start,
for convenience, on the 30° latitude tract at its Atlantic node
near the Azores, where it les between 30° and 40° north latitude.
Tracing it thence easterly, it inclines notably to the north, and
at the meridian of 100° east, has made a northerly gain of 20°
latitude. Thence onward it continues to gain in latitude, at
first more rapidly and then less rapidly to about the meridian
of 180°, when its course is nearly normal to the meridian, and
its latitude may be roughly taken as 75°. Thence onward its
course is south of east to the Mackenzie basin, and thence more
southerly over the Canadian plains east of the Rocky Mountains
until it again joins the high tract that normally lies near 30°
latitude. It thus makes a great loop swinging around the pole,
and passing near it at its climax in latitude, and enclosing the
great north Atlantic eddy (see sketch map 2). The tract is
accentuated by nodes of an anticyclonic nature. The chief of
these is the great “high? of Asia) (Whis prothudesmtom tite

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 767

southeast, and is constructively connected in that direction with
the 30° belt, which develops a strong anticyclonic node near the
California coast, beyond which it connects with the main tract
which crosses the United States and the Atlantic near its normal
position. Between this connection across the Pacific and the
main loop before traced lies the Aleutian depression.

The high tracts of the northern hemisphere therefore form
(1) a great loop embracing the great north Atlantic depression
and, (2) incidentally, as it were, a minor loop embracing the
north Pacific depression. The great loop is not conceived as a
current, much less a whirl, but as a tract along which the upper
atmosphere habitually descends with outflowing tendencies.
The enclosed area of low pressure is a tract over which the
lower atmosphere habitually ascends with inflowing tendencies.

Now the main loop and the main enclosed eddy he on one
side of the northern hemisphere and embrace the chief area of
Pleistocene glaciation. This main loop and its enclosed eddy
embrace about three fourths of the hemisphere north of 30° N.
Lat. In the area left vacant, so to speak, the secondary Aleutian
eddy is developed and covers the main area of the Cordilleran
Pleistocene glaciation.

There can be no question that this peculiar configuration is
due to physiographic influences, particularly the oblique attitude
and peculiar oceanic circulation of the Atlantic, and the similar
obliquity of the main body of the eastern continent. To realize
the full force of this obliquity one should trace on a globe the
great axis of the eastern continent from Cape Verde on the pro-
truding portion of Africa to Cape East at the extremity of Asia,
an immense spiral, and then, starting from the coast of South
America near the lesser Antilles, trace the axis of the North
Atlantic to the heart of the Polar sea ina similar great spiral,
essentially parallel to the former. With these primary influences
many secondary ones are joined, some acting concordantly to
intensify the obliquity of the circulation, and others acting dis-
cordantly and tending to destroy its symmetry, and modify its
configuration.

708 TNC: CHAM B EIAIEEN:

This discussion of the present circulation, too protracted for
this place, yet too brief for its purpose, has seemed necessary to
make clear the conception entertained respecting the agencies
of localization. It has previously been urged in this paper that
a reduction of the carbonic acid in the atmosphere and the con-
sequent reduction of its heat-absorbing capacity must intensify
the influence of all surface features. In the discussion of exist-
ing glaciation I have endeavored to connect the present great
ice-fields genetically with the two great areas of low pressure,
and to associate them with an oblique disposal of the great circu-
latory features. The chief centers of present glaciation lie on
the borders of the American continent. The chief Pleistocene
glaciations, were concentrically arranged about these centers.
As has been pointed out by other students of Pleistocene glacia-
tion, the yreat northeasterly ice-sheet had its western, southern
and southeastern limits almost coterminous with the predomi-
nant paths of northern migrant cyclones. To complete the
hypothesis of localization it is therefore only necessary to assume
an intensification of the present oblique system of circulation,
with a further shifting of the centers of depression in the direc-
tion of the present displacement, accompanied by a sufficient
depression of temperature. And these are the effects assigned
to a reduction of the atmosphere’s thermal capacity due to loss
of carbonic acid.

Suggestion relative to migrant cyclones—One further feature
deserves notice. If the constructive pole of the winds hes some-
where between the earth’s pole and the American continent, the
frictional action of the earth will affect the two sides of the eddy
in opposite senses. On the western side ( from the American
point of view) the friction will tend to drag the bottom air
toward the cyclonic center and crowd the isobars upon each
other. As the lines of the wind circulation and the earth rota-
tion cross each other obliquely, a predisposition to form gyratory
or cyclonic eddies may be inferred, and this may be one of the
sources of migrant cyclones which may be regarded as small
eddies in the grander cyclonic movements.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 769

On the eastern side of the pole of the winds, the earth move-
ment tends to drag the bottom air away from the center and this
is perhaps one of the reasons why the moving cyclones on that
side show a tendency to dispersal, both in course and in force,
as previously noted.

Possible relation to terrestrial magnetism.— It is scarcely appro-
priate to this paper, if it were in my power, to discuss the rela-
tions of this oblique system of atmospheric circulation to the
oblique system of terrestrial magnetism. Crudely stated, the
notion entertained is that an atmosphere charged with electricity,
circulating obliquely about a rotating earth which is inset with
magnetic and magnetizable matter, might give rise to a mag-
netic system which should express the dynamic resultant of the
atmospheric circulation. A comparison of the magnetic and
atmospheric charts shows so many points of resemblance, some
of which are striking peculiarities, as perhaps to justify this ten-
tative notion until the mystery of the earth’s magnetism be solved.
Connected with terrestrial magnetism are auroral manifestations
whose distribution is notably similar to that of the chief Pleisto-
cene glaciation, as was remarked many years ago when first the
progress of exploration outlined the extent of the glacial depos-
its. It can hardly be presumed that either terrestrial magnetism
or auroral displays have in themselves any causal connection
with glaciation, but if they are dependencies of atmospheric cir-
culation they become eminently serviceable to glacial students
by affording a tangible concrete expression of the dynamic
correlation of the atmospheric circulation, free from the intricate
complexities of the latter; in short, a natural resultant at easy
command. The verity of the notion must, of course, depend
wholly on the outcome of magnetic investigations on their own
lines, which happily are now being vigorously prosecuted.

SUGGESTIONS RELATIVE TO MINOR GLACIAL OSCILLATIONS

It has already been noted that besides the oscillations of
epochal order there were subsidiary ones which left their record
in a series of concentric moraines which corrugate the individual

770 LTC. CHAMBLEE,

sheets of glacial débris. The latest drift sheets show this best.
That designated Wisconsin is accentuated by nearly a score of
peripheral ridges. Ina recent admirable paper by Keilhack* it
is shown that similar lines of halt, and perhaps of minor advance,
mark the corresponding European glacial sheet as ‘deployed on
the plains of north Germany ; indeed, even in some of the greater
details, a striking correspondence is traceable between the two
series, whose general identity in age and kind were long since
noted by Salisbury. These minor oscillatory phenomena seem,
therefore, sufficiently general and sufficiently important to require
an explanation, and this explanation is not necessarily connected
with the fundamental cause of glaciation. The preceding dis-
cussion carries in itself a suggestion which is worthy of note in
passing. If the localization of the great ice-sheets was depend-
ent on the general circulation of the atmosphere, any periodic
shifting of the circulation of moderate magnitude might be com-
petent to cause a shifting of the ice-sheets of corresponding
nature. There are historical facts that give some color to the
notion that such shiftings have taken place within the period of
human records. The oscillations of existing glaciers point in a
similar direction. There is clearly a secular shifting of terres-
trial magnetism, but the nature of its cycle is yet undetermined.
Current opinion gives it a periodicity which would quite well
satisfy the demands of the concentric moraines.

GLACIATION NEAR THE CLOSE OF THE PALEOZOIC ERA

While the occurrence of extensive glaciation in India, Aus-
tralia and South Africa near the close of the Paleozoic era may
be regarded as fully established, a specific discussion of its
origin along the lines of an atmospheric hypothesis presents for-
midable difficulties, because the exact date of the glaciation, its

tDie Stillstandslagen des letzten Inlandeises und die hydrographische Entwick-

elung des pommerschen Kiistengebietes. Separatabdruck aus dem Jahrbuch der
konigl. preuss. geologischen Landesanstalt fiir 1898. Berlin.

Terminal Moraines in North Germany. Am. Jour. Sci., Vol. XXXV, p. 401.
Series 3.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS Wfd

immediate antecedents and the nature of contemporaneous con-
ditions in other parts of the world are not yet satisfactorily
determined. No embarrassment attends a merely general appli-
cation of the atmospheric hypothesis set forth in this paper, and
perhaps it would be wise in the present state of knowledge to be
content with such general application. But the main purpose
of the paper—to develop a working hypothesis, helpful in the
promotion of investigation— would be measurably defeated
thereby, for a general theory merely supposed to be applicable
in some indefinite way, not even specifically thought out, much
less shaped to promote definite inquiry, falls short of working
qualities. Were the Paleozoic glaciation a high-latitude phe-
nomenon which could be referred to the same category as the
Pleistocene glaciation, we might well leave specific discussion
until further data were afforded, for few additional doubts as to
the verity of the hypothesis and probably few new lines of
inquiry would be raised. But the Paleozoic glaciation presents
characters so extraordinary as to render it the supreme problem
of glaciation. In it every hypothesis finds its severest test. No
hypothesis that. does not, in some remote way at least, approach
an elucidation of this supreme case can: have serious claims to
acceptance as a working theory. It is, therefore, imperative to
frankly and fully recognize this crucial problem and deal with
its difficulties as well as existing data permit. <A really satisfac-
tory discussion is quite impossible in the present nature of the
case. The attendant atmospheric and geographic conditions
must be postulated, consciously or unconsciously, but the data
for such postulates are imperfect and their interpretation is at
best not more than probable. It is hoped, however, that fairly
good reasons can be assigned for everything assumed in this
paper.

The essential facts that make the Paleozoic glaciation a
peculiarly strenuous problem are these :

1. It occurred in an early stage of the earth’s history. No
appeal can, therefore, be made to an advanced state of secular
cooling leading on the ‘‘final winter’’ nor to any senile condition

772 T. C. CHAMBERLIN

inherent in an aged earth. If the traditional view that the
primitive atmosphere constituted a vast store that has been grad-
ually drawn upon throughout the ages in the formation of the
coals and carbonates, and was their chief source, the atmosphere
at the close of the Paleozoic era must still have been rich, deep
and dense to a degree far surpassing the present atmospheric
state, for vast deposits of coal and carbonates have since been
made through its agency. One of the most conservative as well
as most competent estimates of the consumption of carbonic acid
since the Paleozoic era places it at 5000 times the present con-
tent. To be conservative, let this be halved and halved again,
and still the content of carbonic acid is 1250 times that of the
present. This atmosphere was so different from that of the
Pleistocene and present period as to render uncertain, if not
inapplicable, all arguments founded upon the phenomena of the
latter. The question of the constitution of the Paleozoic atmos-
phere is, therefore, fundamental, because it affects the substratum
of all arguments based on present or recent experience. Even
with the above excessively reduced estimate, do we reach an
atmospheric environment in which any known agency applicable
to the case can be reasonably postulated as competent to cause
general glaciation? In such an atmosphere, or in any atmos-
phere greatly richer than the present in heat-absorbing and heat-
retaining qualities, are there any sufficient grounds for seriously
supposing that any of the putative causes of Pleistocene glacia-
tion, whether topographic, geographic, latitudinal or astronomical,
could produce such a glaciation as is recorded under the tropics
of the far Orient. It is not a part of the purpose or the method
of this paper to antagonize other hypotheses, but rather to invite
their development into working codperation and competition
with that herewith advanced; but a wholesome interaction of
hypotheses will be best attained by eliminating wholly untena-
ble grounds and by bringing all hypotheses within the limital
conditions of competency. It is, therefore, no transgression of
my purpose to urge the question whether all hypotheses are not
required, for their own conservation, to accept so much of the

AVPRODHMESIS OF CAUSE OF GLACIAL PERIODS. 773

fundamental postulates of the atmospheric hypothesis as are
needful to give an atmosphere compatible with glaciation under
such other conditions as prevailed in India, Australia and South
Africa in the later Paleozoic. .

2. The localization was most extraordinary. The chief areas
lay under the tropics —the Indian, under the Tropic of Cancer
and the Australian and South African, under the Tropic of Cap-
tricorn. The Indian area stretched southward to 17° 20’ N. Lat.
and northward to the vicinity of 35°. The Australian area
stretched north to 20° 30’ S. Lat. and southward (in Tasmania)
to 42°. The extent of the South African area is less well known,
but centers about 30° S. Lat. It appears then that on both
sides of the equator glaciation reached two or three degrees
within the tropics, while in the opposite direction general glacia-
tion has not been traced beyond 42° To the south this signifies
little because of the prevalence of the sea. To the north the
apparent limitation is very singular and doubtless very signifi-
cant. It cannot, however, be positively asserted that glaciation
did not prevail in the higher latitudes, but no decisive evidence
of it has yet been discovered. At the same time it must be
recognized that many evidences of remarkable transportation
and of unusual bowlder accumulation, and indeed of occasional
striation have been reported, and that these have been attributed
to glacial agencies by geologists of high standing. It cannot be
affirmed at present that these phenomena were precisely con-
temporaneous with the glacial deposits of the oriental tropics,
but they were nearly so.

In the southern portion of Brazil there are deposits strikingly
similar to the glacial beds of Africa and Australia, but no stria-
tion or distinctive marks of glaciation have yet been authorita-
tively reported.

The southernmost extent of the lowland Pleistocene glacia-
tion was about 37° N. Lat. The Paleozoic glaciation, therefore,
reached 20° farther.

The altitude of the glaciation.—Respecting the altitude at
which the Paleozoic glaciation took place, it is to be remarked

774 T. C. CHAMBERLIN

that in some cases there cis) Sovintimateman ‘association with
marine deposits as to indicate that the ice reached the sea level
and discharged icebergs. The associated marine fossils do
not seem susceptible of explanation by mechanical admixture
through the action of the ice, because of their condition and
their position in the embracing sediments. Oldham’ reports
that certain bowlder-bearing mudstones ‘‘contain delicate Fen-
estella and bivalve shells, with the valves still united, showing
that they had lived, died, and been tranquilly preserved where
they are now found, and proving, as conclusively as the matrix
in which they are preserved, that they could never have been
exposed to any currents of sufficient force and rapidity to trans-
port the blocks now found lying side by side with them. These
included fragments of rock are of all sizes from a few inches to
several feet in diameter.”

These and other evidences leave little room to doubt that a
part of the glaciation at least affected low horizons. On the
other hand, most of the glacial beds are so related to their own
glaciated floor as to show that they were formed by land ice.
This is confirmed by the nature of the striz, the relations of the
transported blocks to their source, and the association of the
glacial beds with fresh-water deposits. At present some of the
glacial beds are 3000 to 3500 feet above sea level (Tasmania),
but in general they are much lower. How much of this altitude
is due to subsequent changes I do not know. There is, however,
much evidence that the glaciation was not of the alpine type, or
at least not simply of the alpine type. It spread over broad
areas of moderate slope.

In kind of glaciation and in topographic relations the Paleo-
zoic phenomena seem to have been of the same class as the
Pleistocene.

Approximate age.—Professor David and other cautious writers
of recent date do not attempt to locate the horizon of this glacia-
tion nearer than Permo-Carboniferous. It is certain that in the
Salt Range in northwestern India a Productus fauna overlies the

*R. D. OLDHAM: Rec. Geol. Surv. India, XIX, 1886.

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 775

bowlder beds. From this and other paleontological evidence it
would seem that the lowest of the g

dated the disappearance of the Permian faunas from the seas.”

glacial deposits at least ante-

It is unfortunate that the peculiar nature of the formation, and
the not less peculiar nature of the associated flora, make it
impossible at present to fix its exact horizon in terms of the
European and American standards, so that the contemporaneous
conditions in these regions could be determined. However, for
the application of the atmospheric hypothesis the foremost ques-
tion is the relationship of glaciation to the great agencies that
affected the constitution of the atmosphere. These agencies
were (1) the formation of coal, and (2) chemical reaction
between the air and the earth’s surface.

1. Relative to the first, it is certain that the glaciation
closely followed the great coal-depositing period, and indeed
fell in with the latest stages. In Australia there are consider-
able deposits of coal (the Gretna Coal Measures, embracing
twenty to forty feet of coal) deposited ‘between the erratic-
bearing horizon of the lower marine series and the similar
horizon of the upper marine series” (David)? -1f, theretore,
we look to the deposition of coal as the agency of atmospheric
exhaustion, the relationship is nearly ideal.

2. If we look to elevation, and consequent large earth-
contact, the relationship does not appear to be what theory
would demand. It can scarcely be questioned that at the close
of the Paleozoic period there was a very unusual surface move-
ment, affecting great areas of the earth’s surface and increasing
largely the exposure of the land. The period appears to have
been altogether comparable to that at the close of the Tertiary
period. If we were seeking the cause of the glaciation assigned
to the Triassic, or the occasion of the salt and gypsum deposits

«There is some evidence of another glacial horizon at or about the base of the
Triassic (well indicated in White’s excellent synopsis, Am. Geol., May 18809, table,

p- 315). The present discussion will, however, be confined to the lower horizon, that
of the Talchirs and their equivalents.

2 Quarterly Jour. Geol. Soc., Vol. LII, May 1896, p. 300.

776 T. €. CHAMBERLIN

so widely prevalent in the Permian and Triassic formations, this
elevatory movement would stand in the proper relations. But,
if present evidence is to be trusted, it does not stand in the
proper antecedent relations to the Permo-Carboniferous glacia-
tion, at least not as the primary agency. Still, though there is
an absence of evidence of large exposure of the land surface to
atmospheric degradation for a notable period preceding the
Permo-Carboniferous glaciation, there are good grounds for
believing that the great era-closing movement of the Paleozoic
had made notable advance even at this time.

The Gondwana elevation.—The glacial beds under considera-
tion form the basal members of the remarkable Gondwana series,
the chief members of which are land and fresh-water deposits.
These in themselves imply a recently rejuvenated topography,
for an ancient topography has a perfected drainage system and
adjusted gradients. It is the dominant belief of those who have
most studied the region circumjacent to the Indian Ocean, that
the formation of the Gondwana series and the development and
distribution of the remarkable Glossopteris flora, imply exten-
sions and connections of land of a somewhat unusual kind. If
this belief were accepted to the full extent urged by its strongest
advocates, it would in itself involve a very large exposure. I am
not disposed, however, to force the doctrine of a Gondwana
continent beyond the most modest limits, however much it might
contribute to a favorable reception of the hypothesis under dis-
cussion. It appears to me that the distribution of the Glossop-
teris flora may be in some notable part a climatic rather than
a topographic effect; that is to say, the peculiar atmospheric
conditions, of which glaciation was the supreme expression, dis-
tinguished that quarter of the globe from the rest, and may in
themselves have controlled the distribution of the peculiar flora in
question. It may therefore only be necessary to postulate such
an extension of the land as was required to permit the migration
of the flora and its companion fauna.

However this may be, it is very generally agreed that some
notable land extension prevailed as early as the origination and

YMPOTHESTS-OF CAUSE*OF (GLACIAL, PERIODS TG,

distribution of the Glossopteris flora. It will be quite conserva-
tive to assume that this involved a land connection between
India and Australia, and probably New Zealand, the connection
presumably lying along the submerged platform which even to
this day stretches southeasterly from Asia to the islands in
question with slight interruptions. It is not improbable that
between India and South Africa at least a partial bridge was
formed by the elevation of the submerged plateau on which
Madagascar and the Seychelles rest, together with the tract
now accentuated by the Maldive islands.

A connection with South America (where the Glossopteris
flora also appeared — southern Brazil and Argentina) involving
the least radical departure from modern configuration, may have
been made via New Zealand and the Antarctic continent. This,
I believe, also best satisfies the general tenor of paleontological
evidence.

If the geographic changes were confined to such connections
and extensions of land as these, and to such moderate eleva-
tions as the nature of the glacial beds and the associated deposits
seem to imply, and to such changes in the northern hemisphere
as can fairly be assigned to the Permo-Carboniferous period,
there does not seem to be adequate ground for attributing a very
exceptional depletion of the atmosphere to land-contact alone,
or chiefly, though it may have made some notable contribution
in that direction.

Effects of atmospheric depletion by coal deposition—We there-
fore turn to coal-formation as the effective alternative. There
are no reliable estimates of the total carbon in the coal and
carbonaceous deposits of the Carboniferous period, but such
approximations as have been made seem to show that it equals
several times the present atmospheric content, and that its
extraction superadded to the increasing formation of carbonates
resulting from the rising land would have been competent to
reduce to the point of glaciation an atmosphere three or four times
as rich in carbon dioxide as the present ; in other words, such
an atmosphere as the sub-Carboniferous climate seems to imply.

778 T. C. CHAMBERLIN

A question of no small interest is the special kind of effect
which an atmosphere reduced by coal formation would induce
as distinguished from that induced by depletion through earth-
contact. In the latter, as already set forth, bicarbonates were
the chief product, and carbon dioxide, temporarily locked up,
played a very important part. Through the peculiar agency of
the ocean this ‘‘loose”’ carbon dioxide hastened the develop-
ment of glaciation, prepared the conditions for strong reaction
and accelerated the reaction when inaugurated. In the forma-
tion of coal and like products no such effective temporary factor
is produced. The carbon is, to be sure, temporarily held in the
vegetation, but so much as decays goes directly back into the
atmosphere, in the main, and the rest becomes permanently fixed.
Neither part goes into an intermediate state of reserve, subject
to being called forth by change of conditions as in the case of
the second equivalent of the bicarbonates of the ocean. The
action is somewhat analagous to the original carbonation of the
silicates of the crystalline rocks in which the first equivalent of
carbon dioxide when once united remains fixed (barring accidents
to which coal is also liable), but in this case there is also a
second equivalent of carbon dioxide temporarily locked up so
long as a state of solution is maintained. Succinctly stated,
without the unessential qualifications: (1) Depletion by coal
formation is accompanied by no intensifying and reactive factor ;
(2) Depletion by conversion of silicates into carbonates is
accompanied by an intensifying and reactive factor; (3) Deple-
tion by the solution of limestone is wholly temporary in nature
and specially capable of promoting intensification and reaction.

If, therefore, the impoverishment of the atmosphere as the
prerequisite of glaciation in Permo-Carboniferous times was due,
in the main, to the extraction of carbon in the form of coal and
like deposits, there was absent, to that extent, the factor to which
the hastening of glaciation and of reaction is assigned. Before
glaciation could be affected in the measurable absence of this
accelerating agent, it was necessary for the permanent depletion
to go to greater lengths. Moreover the depletion when once

HYPOTHESIS OF CAUSE OF, GLACIAL. PERIODS 779

affected was essentially a non-reactive one. Of course the reac-
tive factor was never really absent, for the formation and solu-
tion of carbonates was always in progress. In this case it is
merely supposed to be the minor rather than the major factor.
It is inferred, therefore, that a higher stage of permanent deple-
tion of the atmosphere was reached before glaciation ensued
through coal formation than would have been the case had the
glaciation been produced by the formation of carbonates. To
this, in a measure at least, is attributed the conditions which
made it possible for the glaciation to affect lower latitudes in
Permo-Carboniferous times than they did in Pleistocene times.
As before noted, the Permo-Carboniferous glaciation extended
20° nearer to the equator than the Pleistocene.

The locahzation of the Permo-Carboniferous glaciation. —It
remains to consider the remarkable localization of this ancient
glaciation. Thegeneral principles involved are assumed to have
been the same as those already applied to tne Pleistocene prob-
lem, but the geographic factors were quite different, and it is
here that the lack of complete data is most keenly felt. In
Pleistocene times, as also at present, certain great geographical
features are thought to have given a pronouncedly oblique
circulation to the air currents of the northern hemisphere. In
the southern hemisphere at present a much greater approach to
symmetrical circulation prevails because great oblique features
are absent. It is postulated that the configuration of Permo-Car-
boniferous lands and oceans was such as to seriously disturb the
symmetry of the atmospheric and oceanic circulation of that
hemisphere, and to give it peculiar form and special intensity.

The geographic features of the Permo-Carboniferous period.—The
assigned changes introduced by the development of Gondwana
land have been mentioned. These are thought to have pro-
longed the Asiatic continent southeasterly to Australia, and
probably to New Zealand, and perhaps to the Antarctic land.
This prolongation, taken with its backward projection across
Asia and Europe, constituted an oblique feature of great exten-
sion. It also interposed a barrier which very notably modified

780 T. C. CHAMBERLIN

the water connections of the Pacific and Indian oceans. The
warm equatorial currents which now flow through the numerous
straits of the East Indies and add warmth to the Indian Ocean
were turned back, andthe heaturetained= in themeaciinc ayant:
the same time the cold currents of the southern Indian and the
adjacent Antarctic oceans were shut out measurably or wholly
from the Pacific, and turned northward into the equatorial
portion of the Indian Ocean. There was thus a concentration of
heat in the one and of cold in the other. If the suggested con-
nection of New Zealand with the Antarctic continent was made,
these cold southern waters would have been effectively shut out
from the Pacific and forced to circulate through the Indian Ocean.
If the other conservative changes suggested to meet the demands
of the Gondwana phenomena were realities, the Indian Ocean
took the form of a great triangle with a very broad base in the
antarctic regions, and a narrowed apex reaching across the
equator to the vicinity of the Indian glaciation.

In the north Atlantic region there is evidence that the great
readjustment which closed the Paleozoic era had made notable
advances at the probable time of the Oriental glaciation The
New Red Sandstone of western Europe is not unlike the Gond-
wana series in general characters, and indicates a like reju-
venated land. Within it also are found arkose, conglomerates
and breccias, often formed of large, far-transported blocks.
‘‘Some of these blocks are three feet in diameter, and show dis-
tinct striation. These Permian drift beds, according to Ramsay,
cannot be distinguished by any essential character from modern
glacial drifts, and he has no doubt that they were ice-borne,
and, consequently, that there was a glacial period during the
accumulation of the Lower Permian deposits of the center of
England.” * There is good ground to believe that previous to
the formation of these deposits the land on the European border
of the Atlantic had risen relatively. There are similar evidences
on the American side. The close relations between the land
faunas and floras on the two continents strongly imply a free

*S1R ARCHIBALD GEIKIE: Text-Book of Geology, p. 753.

WMEOLHTESISVOR CAUSE OF AGEACIAL PERTOOS “78s

land connection. This is most pointedly indicated by the dis-
tribution of the amphibians of the Carboniferous and Permian
periods. The Branchiosauria, Aistopoda, Microsauria, and Laby-
rinthodontia vera were all represented on both continents, and
unless the doctrine of parallel evolution be pushed to a seeming
extreme, the only satisfactory explanation is an ample land con-
nection. The amphibians of today are fatally affected by salt
water, and even their eggs lose their vitality after a short sub-
mergence init. It cannot be positively affirmed that this was
true of the Carboniferous amphibians, but the presumptions
appear to lie in that line. At any rate the occurrence of all
the leading branches on both continents renders it quite improb-
able that a broad ocean intervened. It is therefore assumed
that the Atlantic Ocean was restricted at the north by such con-
nection. To be definite, it is assumed that it essentially termi-
nated south of the Greenland-Iceland-Faroe platform, or possibly
south of the Telegraphic plateau.

There are few data that give specific indications as to the
configuration of the north border of the Pacific at this time, but
the considerations that have just been urged with reference to
the distribution of the fauna and flora are apparently best satis-
fied by supposing an emergence of the very slightly submerged
continental platform of the arctic region generally. This is in
harmony with the history of the preceding Paleozoic periods
during which the Eurasian and North American continents were
essentially a unit and free migration from one to the other was an
oft-repeated, if not predominant, phenomenon. If this be the
true inference the Pacific Ocean was limited at the north to about
60° eat.

In equatorial latitudes it is not improbable that the Atlantic
and Pacific oceans were united between the main bodies of the
North American and South American continents, so that a com-
mingling of waters took place here not unlike that which now
obtains between the Pacific and Indian oceans.

It is not improbable also, judging from the distribution of
Permian marine beds, that inland seas extended along the

782 T. C. CHAMBERLIN

Mediterranean tract into eastern Europe and perhaps to the Cas-
pian-Ural region of Asia; indeed, it is not altogether improbable
that straits or narrow seas may have connected with the apex of
the Indian ocean. At least in the later Permian) times) the
marine faunas of India and of Europe were notably similar,
and in the early Mesozoic they became so nearly identical as
to make a connection along this line extremely probable.

Effect of the supposed geographic changes on atmospheric circu-
lation.—While none of these postulated changes involve great
terrestrial movements, or depart widely from the rather definite
indications of the phenomena concerned, it will be seen upon a
study of the resulting distribution of land and water that they
probably profoundly affected the circulation of the atmosphere.
The limitation of the Atlantic at the north by the European-
American connection rendered it essentially an equatorial and
warm temperate ocean. Its present high-latitude connection,
involving the transportation of vast quantities of ice and cold
water into it from polar regions and the reciprocal loss of heat
borne into the high latitudes by the Gulf Stream, was eliminated.
The atmospheric function of the Atlantic was, therefore, radically
changed. That great oblique factor to which was assigned so
large a function in the localization of Pleistocene glaciation, was
largely absent from the Permo-Carboniferous circulation. To
the similar restriction attributed to the north Pacific a minor
limitation of a like kind may be assigned. Instead, therefore,
of a polar sea exchanging its thermal properties with an equa-
torial sea, as at present, there would be substituted a prevailing
polar land, relieved probably only by the deep basin of the
Arctic sea, whose limited extent and land-locked situation would
render it little more significant in general climatology than the
present Mediterranean.

On the other hand, very notable oblique features appear in
the equatorial and southern regions. The postulated changes of
the Pacific Ocean, by shutting off its connections with the Indian
Ocean, probably brought into effective influence its long north-
westerly and southeasterly trend, now neutralized by its

HNMPOTHE SIS OF. CAUSE OF GLACTAL! PERIODS” 783

westward connections. In other words, the somewhat balanced
distribution of the present Pacific was replaced by an effective
obliquity which could scarcely have failed to powerfully influ-
ence the general circulation of the Paleozoic atmosphere. The
northwest-southeasterly extension of the great Eurasian-Austra-
lian land paralleled this and intensified its effects. In other
words, the Pacific Ocean and the parallel Eurasian-Australian
continent constituted, in Paleozoic times, a couplet of oblique
features that were chiefly effective in the equatorial zone and
the southern hemisphere. They replaced the similar pair now
formed by the north Atlantic and the eastern continent. It is
inferred, therefore, that an obliquity of circulation of a pro-
nounced order prevailed in Permo-Carboniferous times, by virtue
of which the southern hemisphere was brought under the influence
of meteorological agencies analogous to those that in Pleistocene
times affected the northern hemisphere.

Some differences, however, are to be noted. The equatorial
zone was then profoundly affected by the oblique features which
lay directly athwart it. In addition to this there was the pecul-
lar configuration of the Indian Ocean already set forth, namely,
a broad, open mouth extended to the Antarctic polar regions,
with a convergence to a narrow equatorial apex 20° or more
north of the equator. The general course of the circulation in
this may be assumed to have been much as it is today; that is,
a movement in the polar latitudes, at first northerly and easterly,
then curving about to the northward and northwestward as it
approached the equatorial zone, and at length returning to the
southwest along the African coast, thus forming a free circula-
tion between the high latitudes and the low latitudes, with high
latitude influences greatly preponderant. This circulation in
Paleozoic times may be reasonably assumed to have been much
more intense than at the present time, first, because there were
then, by hypothesis, greater intensities of temperature, and
second, because a larger percentage of the Antarctic waters were
forced to flow into the apex of the Indian Ocean by the con-
figuration of the land. This last statement would hold true even

784 T. C. CHAMBERLIN

if New Zealand were not connected with the Antarctic continent
and South America, for the avenue of escape toward the Pacific
would be circumscribed by the minimum elevations which the
Gondwana phenomena seem to require. If the Antarctic-South-
American connection were made, it would form a barrier to cir-
cumpolar circulation, and all the polar ice-drift from South
America to New Zealand would doubtless be forced northeast-
erly into the Indian Ocean. This would certainly lend great
intensity to the circulation of the polar currents through the
Indian Ocean. The temperature of the latter would therefore be
radically affected by the immense quantities of ice and cold
water carried through it by this intensified circulation under the
atmospheric conditions postulated. A like profound influence
upon the overlying atmosphere must necessarily have followed.
The narrow apex of the ocean under the tropics would probably
have afforded little relief from the dominance of these currents.
If this cold area be contrasted with the heated state which
should naturally prevail in the Pacific Ocean, because of its vast
breadth under the equator, its limitations at the north and its
somewhat narrow communication at the south (particularly if it
be shut off from the Antarctic flow past New Zealand) should
give rise to antithetical conditions of temperature and pressure
sufficient to radically influence the general circulation of the
southern hemisphere. It is conceived that this extraordinary
couplet might even introduce a systematic exchange of atmos-
pheres between the northern and the southern hemispheres, con-
sisting essentially of a cold north-seeking current flowing across
the Indian Ocean into the northern hemisphere, correlated with
a warm return current flowing from the northern to the southern
hemisphere across the tropical regions of the Pacific, but this
conception is not regarded as a vital part of the hypothesis.
The configuration of the Atlantic is supposed to have caused
it to play a subordinate part, the northern portion becoming an
auxiliary of the Pacific and the southern portion more or less
largely an auxiliary of the Indian Ocean. If we assume that the
Gondwana extension connected New Zealand with the Antarctic

HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 785

lands and South America, the ocean currents may be pictured as
sweeping eastward from South America along the icy borders of
the Antarctic continent into the great bay south of Australia, out
of which they recurved and flowed northward across the equator
to the Indian peninsula, which they freely bathed, and, returning
along the supposed Gondwana connection, wrapped about South
Africa and then flowed northward toward the equatorial regions,
a portion then curving backwards and descending the coast of
South America to complete the circuit. Such a circulation would
throw perhaps two thirds of the antarctic influence into the
Indian Ocean. On the other hand, seven eighths or more of
the equatorial influence would probably be brought to bear
upon the Atlantic and Pacific oceans. Asa result these oceans,
notwithstanding the impoverished condition of the atmos-
phere, received and retained a large percentage of the sun’s
heat.

Referring to the principles stated earlier in this discussion,
it may be remembered that it was noted that a diathermous
atmosphere permits a larger part of the sun’s heat to reach the
surface of the earth than a thermally opaque atmosphere, and
that the portion which falls upon the ocean for the most part
penetrates it until it is absorbed. A certain part, to be sure, is
reflected, but in the zone of nearly vertical rays this is reduced
to the minimum. As the result of the ocean’s ability to absorb
and retain heat, the diathermacy of the atmosphere is of less
consequence in equatorial oceanic regions than in land tracts and
hence the great equatorial oceans may have remained measurably
warm throughout the glacial period.

It is conceived, therefore, that under these conditions, glaci-
ation may have been produced in exceptionally low latitudes, and
that its distribution was closely associated with the Indian Ocean.
At the same time it is conceived that the lands immediately
adjacent to the Atlantic and Pacific oceans, especially in low
latitudes, were so far affected by the favorable thermal condition
of those great bodies as to enjoy relatively mild temperatures,
at least temperatures sufficiently genial to save them and the

786 T. C, CHAMBERLIN

adjacent lands from the exterminating effects that might natur-
ally be associated with a glaciation in the tropics.

Relative to the more specific location of the Permo-Carbonif-
rous glaciation, it may be noted that a tendency to form “lows”
in India, Australia, and South Africa, not far from the ancient
glaciated areas, is observable even under the present conditions.
It is presumed that much more pronounced eddies were, in
Permo-Carboniferous times, located on the borders of the cold
belt formed by the intensified antarctic circulation and that these
determined the areas of specific glaciation.

Conditions in the northern hemisphere.—In the arctic regions, a
very low temperature may be confidently postulated under the sup-
posed conditions, because of the extent of the land and the absence
of oceanic circulation between the high north and the equatorial
regions. A Siberian climate of an intensified order is therefore
assumed to have prevailed over the high latitudes of the northern
hemisphere. This may doubtless have given rise to limited
accumulations of snow in favored localities, developing into
glaciers, but on account of the general low precipitation and
the dryness of the atmosphere, giving rise to large evaporation,
this may not have becomea pronounced fact. In so far as glacial
deposits originated in the interior of the land they would be
liable to destruction by surface denudation before submergence.
The Permo-Triassic land period was long. Here and there, as
already noted, there are phenomena which find their easiest
explanation in glaciation and ice transportation. It is to be
anticipated that, if this view be correct, further indications of
severe temperature in northern latitudes will be developed in the
course of future studies. It may be remarked that there is now
nearly as much evidence of Permian glaciation in the northern
hemisphere in regions away from mountains as there is of Pleisto-
cene glaciation in the southern hemisphere in like situations.

As remarked at the outset of this part of the paper, a really
satisfactory discussion of the Permo-Carboniferous glaciation is
impossible in the present state of knowledge. JI am by no means
blind to the uncertain factors that inhere, at once, in the time

HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 787

relations, in the geographic features, and in the meteorological
inferences drawn from them. The most that could be hoped
from an attempt to explain so extraordinary phenomena in so
imperfect a condition of the data is to suggest the general direc-
tion in which, perchance, the truth may ultimately be found to
lie. T. C. CHAMBERLIN.

EDILORIAWe

THE ‘‘Commissao Geographica e Geologica”’ of the State of
Sao Paulo, Brazil, has just issued its first topographic sheet —a
preliminary edition of the “folha de S. Paulo.” This is a thirty
minutes sheet on a scale of one to one hundred thousand with
contours twenty-five meters apart covering the region between
Sao Paulo and Santos, and including both of those cities. It
crosses one of the most characteristic and interesting pieces of
topography of all South America—the Serra do Mar. The bit
of coast shown in the vicinity of Santos is also a character-
istic one, while the high plateau of the interior is beautifully
shown between the crest of the serra and the city of Sado
Paulo.

Among other things brought out by this map is the evidence
of a late depression of the coast. The bay of Santos and the
estuaries thereabout are the remnants of a once much larger
island-dotted bay that extended from Guaruja on the present
coast to Cubatdo at the foot of the Serra. The mud buried hills
that protrude from the marshes about Santos are only the
summits of mountains whose bases were carried beneath the
ocean water by this depression.

The map is printed in three colors: the hydrography in blue,
the topography in brown, the remainder in black. In appear-
ance it is up to the highest standards of modern map making,
and reflects great credit upon everyone responsible for its
preparation and publication. That such work has been pro-
vided for by the State of S. Paulo, and that the people have had
the patience to await the slow and tedious processes of triangula-
tion, field work, office work, and all the other preliminaries of a
good map, is the most healthful and encouraging evidence we
have yet seen of the high intelligence and modern progress of

788

EDITORIAL 789

that part of South America. It is pleasant to note that this
important work has been entrusted to our fellow countryman
and colleague, Professor O, A. Derby, and that his chief topog-
rapher, Mr. Horace E. Williams, received his training in this
country.

J. C. BRANNER.

A REFERENCE LIST OF SUMMARIES OF LITERA-
TURE ON NORTH AMERICAN PRE-CAMBRIAN
GEOLOGY, 1892 TO THE CLOSE OF 1808:

In the Archean and Algonkian Correlation Paper, by C. R.
Van Hise (Bulletin 86, U. S. Geol. Survey, 1892), North Ameri-
can pre-Cambrian literature was fully summarized from the time
of the earliest publications to 1892. Since 1892, summaries of
pre-Cambrian literature have been published from time to time
in the JOURNAL OF GEoLoey by C. R. Van Hise, and have lately
been continued in the same periodical by ‘©. kK Leitha ihe
summaries thus far published are supposed to cover the field ot
pre-Cambrian geology for North America from 1892 to the close
of 1898. To facilitate reference to the summaries and original
articles there is given below a list of the articles summarized,
arranged alphabetically according to authors’ names, together
with the volume and page of the JouRNAL in which the summary
appears. At the end there will be found a list of the principal
regions of pre-Cambrian exposure, and under each region the
names of the men whose articles on the pre-Cambrian of that
area have been summarized.

The summaries here listed and those to follow for the years
1899 and 1900 will serve as a basis for a bulletin, to be issued
under the joint authorship of C. R. Van Hise and C. K. Leith,
supplementary to Bulletin 86, U.S. Geol. Survey. It is probable
that there are a number of omissions and errors in the summaries
listed, and it is hoped by sending out this bibliography that a
number of them may be noted and brought to the attention of the

* The summaries have appeared in the JOURNAL OF GEOLOGY as follows:
Vol. I, 1893, pp. 304-314, 532-541.

Vol. II, 1894, pp. 109-118, 444-454.

Vol. III; 1895, pp. 227-236, 709-721.

Vol. IV; 1896, pp. 362-372, 744-750.

Vol. VI, 1898, pp. 527-541, 739-753, 840-854.

Vol. VII, 1899, pp. 190-205, 406-425, 702-708.

790

—

A*\KREPERENCE LIST OF SUMMARIES 791

authors, who would be glad to know also of any errors or omis-
sison in Bulletin 86 itself. Any correspondence with reference to
them should be addressed to C. K. Leith, Madison, Wis.

In order that the purpose and scope of the summaries may
be clear to every one, there is repeated below the prefatory note
published by C. R. Van Hise with the first lot of summaries
appearing in the JOURNAL.

The summary proper and the comments are kept wholly separate,
in this way preventing the confusion which frequently comes from a
mingling of the two. In the summaries the original language of the
author is used as far as practicable, although a single sentence may
be taken from several sentences of the original. Where it is dis-
advantageous to use the original language, other words are used.
This often is necessary because the language which is adapted to com-
plete exposition is often not the best adapted to résumé. No quota-
tion marks are used ; for the ideas contained, whether in the original
language or not, are wholly the ideas of the author, and the whole is in
fact quoted.. It might be thought that better results would be reached
by indicating through quotations what words are taken from the origi-
nal, but this method would necessitate an unpleasant and constant alter-
nation from quoted to non-quoted phrases. As a result of experience
with the two methods, the editor feels certain that he is able more accu-
rately and fully, in a brief space, to represent the ideas of the original
author by the method proposed, than by following the usual method.

The summaries are confined to articles or parts of articles pertain-
ing to pre-Cambrian stratigraphy. Purely economic or petrological
articles are not summarized unless they concern pre-Cambrian strati-
graphy, in which case the substance of the conclusions is given, rather
than a full account of the observations and the manner of reaching
them.

The abstracts have the defects of all summaries, —a certain amount
of inaccuracy, because many modifying and qualifying facts cannot be
given, and because undue emphasis is placed upon the conclusions.

In many cases no comments are made. This does not imply that
the editor agrees with the statements of the summaries. To criticise,
qualify, or refute the statements of the authors in all cases of disagree-
ment, would often result in extending the space taken by the com-
ments beyond that required for the summaries. However, when the

792 C. K. LEITH

points at issue are of general interest or of fundamental importance, it
is advisable to make comments and enter into discussions, even if the
space taken by such comments be greater than that given to the sum-
mary of the original articles. In such comments neither commenda-
tion nor censure will be made, but the aim will be to point out the
conclusions announced which fail of complete establishment and the
generalizations which appear to go beyond what is warranted by the
facts published. ‘The purpose of indicating what appear to the editor
as deficiencies of these kinds is neither to put himself dogmatically in
opposition to the statements of the author reviewed, but to direct
attention to the questions involved, and in cases of doubt to keep them
open for further study in the field and laboratory.

ADAMS, F. D.

Norian oder Ober-Laurentian von Canada. (Neues Jahrb., B. B. VIII,
1893, pp- 419-498.) Summarized Journ. of Geol., vol. 2, p. Ilo.

On the typical Laurentian area of Canada. (Journ. of Geol., vol. 1,
1893, pp- 325-340.) Summarized Journ. of Geol., vol. 2, p. 111.

Preliminary report on the geology of a portion of central Ontario situ-
ated in the counties of Victoria, Peterborough, and Hastings, together
with the results of an examination of certain ore deposits occurring in
the region. (Ann. Rept. Geol. Surv. of Canada, for 1892-3, vol. 6,
part J, pp. 15. 1895.) Summarized Journ. of Geol., vol. 3, p. 229.

A further contribution to our knowledge of the Laurentian (Art. VII).
(Am. Journ. of Sci., 3d ser., vol. 50, 1895, pp. 58-69. With plates I
and II.) Summarized Journ. of Geol., vol. 4, p. 364.

Laurentian area in the northwest corner of the Montreal sheet. Sup-
plementary chapter to Ells’ report on a portion of the Province of
Quebec. Ann. Rept. Geol. Surv. of Canada, for 1894, vol. 7, part J,
pp- 93-112. 1896.) Summarized Journ. of Geol., vol. 6, p. 850.

Report on the geology of a portion of the Laurentian area lying to the
north of the island of Montreal. (Ann. Rept. Geol. Surv. of Canada,
for 1895, vol. 8, part J, pp. 184. 1897. With geol. map.) Summar-
ized Journ. of Geol., vol. 7, p. 411.

and BAaRLow, A. E.

On the origin and relations of the Grenville and Hastings series in the
Canadian Laurentian. (Am. Journ. Sci., 4th ser., vol. 3, 1897, pp.
173-180.) Summarized Journ. of Geol., vol. 7, p. 413.

AGUILERA, JOSE G.

Sinopsis de Geologia Mexicana. (Bol. del Inst. Geol. de Mexico, Nums,
4, 5, and 6, part 2, 1897, pp. 189-250. With geol. map.) Summar-
ized Journ. of Geol., vol. 7, p. 707.

ATREFERENCE LIST OF SUMMARIES 793

BaILey, L. W.

Preliminary report on geological investigations in southwestern Nova
Scotia. (Ann. Rept. Geol. Surv. of Canada, for 1892-3, vol. 6, part Q,
pp. 21. 1895. With geol. map.) Summarized Journ. of Geol., vol.
a5. 302:

Report on the geology of southwest Nova Scotia. (Ann. Rept. Geol.
Surv. of Canada, for 1896, vol. 9, part M, pp. 154. 1898. With geol.
map.) Summarized Journ. of Geol., vol. 7, p. 423.

BARLOw, A. E.

Relations of the Laurentian and Huronian on the north side of Lake
Huron. (Am. Journ. of Sci., 3d ser., vol. 44, 1892, pp. 236-239.)
Summarized Journ. of Geol., vol. 1, p. 308.

Relations of the Laurentian and Huronian rocks north of Lake Huron.
(Bull. Geol. Soc. Am., vol. 4, 1893, pp. 313-332). Summarized
Journ. of Geol;; vol..2,p. 114:

and FERRIER, W. F.

On the relations and structure of certain granites and associated arkoses
on Lake Temiscaming, Canada. (Geol. Mag., vol. 5, 1898, pp. 39-
41.) Summarized Journ. of Geol., vol. 7, p. 419.

see Adams.

See Ells.

Bascom, F.
The ancient volcanic rocks of South Mountain, Pennsylvania. (Bull. U.
S. Geol. Surv., no. 136, 1896, pp. 124. With geol. map.) Summar-
ized Journ. of Geol., vol. 6, p. 530.

BAYLEY, W. S.

Actinolite-magnetite-schists from the Mesabé iron range in northeastern
Minnesota. (Am. Journ. Sci., 3d ser., vol. 46, 1893, pp. 176-180.)
Summarized Journ. of Geol., vol. 2, p. 454.

The eruptive and sedimentary rocks on Pigeon Point, Minnesota, and
their contact phenomena. (Bull. U.S. Geol. Surv., no. 109, 1893, pp.
121. With geol. map.) Summarized Journ. of Geol., vol..4, p. 750.

The basic massive rocks of the Lake Superior region. (Journ. of Geol.,
vol. 1, 1893, pp. 433-456; 587-596!; 688-716; vol. 2, 1894, pp. 814—
825; vol. 3. 1895, pp. I-20.) Summarized Journ. of Geol., vol. 4,
p. 751.

See Van Hise.

BELL, ROBERT.

On the Laurentian and Huronian systems north of Lake Huron. (First
Rept. Bureau of Mines, Ontario, for 1891, pp. 63-94, 1892.) Sum-
marized Journ. of Geol., vol. I, p. 306.

794 Oo Ne, JL RTINE

Report on the Sudbury mining district. (Ann. Rept. Geol. Surv. of
Canada, for 1890-1, vol. 5, part F, pp.95. 1893. With geol. map.)
Summarized Journ. of Geol., vol. 1, p. 539.

Pre-Paleozoic decay of crystalline rocks north of Lake Huron. (Bull.
Geol. Soc. Am., vol. 5, 1894, pp. 357-366.) Summarized Journ. of
Geols; vola3;p.228-

Report on the geology of the French River sheet, Ontario. (Ann. Rept.
of the Geol. Surv. of Canada, for 1896, vol. 9, part I, pp. 29.
1898. With geol. map.) Summarized Journ. of Geol., vol. 7,
p. 416.

BERKEY, CaP:

Geology of the St. Croix dalles. (Am. Geol., vol. 20, 1897, pp. 348-
383, and vol. 21, 1898, pp. 139-155, 270-294.) Summarized Journ.
of Geol., vol. 7, p. 191.

BEYER, S. W.
The spotted slates associated with the Sioux quartzite. (Johns Hopkins
Univ. Circulars, no. 121, 1895, p. 10.) Summarized Journ. of Geol.,
vol. 4, p. 750.
The Sioux quartzite and certain associated rocks. (Iowa Geol. Surv.,
vol. 6, 1896, pp. 69-112.) Summarized Journ. of Geol., vol. 7, p. 705.

BLUE, A.

The new Ontario. (Fifth Rept. Bureau of Mines, Ontario, for
1895, pp. 193-196. 1896.) Summarized Journ. of Geol., vol. 6,
p. 751.

Bonney, T. G.

The mode of occurrence of Eozoon Canadense at Cote St. Pierre. (Geol.
Mag., vol. 2, 1895, pp. 292-299.) Summarized Journ. of Geol., vol.
4, p. 363.

Boss, C. M.

Some dike features of the Gogebic iron range. (Trans. Am. Inst. Min.
Engineers, vol. 27, 1898, pp. 556-563.) Summarized Journ. of Geol.,
vol. 7, p. 190.

Brooks, A. H.

Preliminary petrographic notes on some metamorphic rocks from eastern
Alabama. (Bull. Geol. Surv. of Alabama, no. 5, 1896, pp. 177-197.)
Summarized Journ. of Geol., vol. 6, p. 539.

See) Wolf) |e.

BUELL, aM:
Geology of the Waterloo quartzite area. (Trans. Wis. Acad. Sci., vol. 9,
1893, pp. 255-274.) Summarized Journ. of Geol., vol. 2, p. 116.

A REFERENCE LIST OF SUMMARIES 795

BurRWASH, E. M.

Geology of the Nipissing-Algoma line. (Sixth Rept. Bureau of Mines,
Ontario, for 1896, pp. 167-184. 1897.) Summarized Journ. of Geol.,
vol. 7, p. 419.

CLARK, Wm. B.

The physical features of Maryland. (Maryland Geol. Surv., preliminary
publication of vol. 1, 1897, part 3, pp. 95. With geol. map.) Sum-
marized Journ. of Geol., vol. 6, p. 534.

Outline of present knowledge of the physical features of Maryland,
embracing an account of the physiography, geology, and mineral
resources. (Maryland Geol. Surv., vol. 1, 1897, part 3, pp. 139-228 ;
Historical sketch, part 2, ibid., pp. 43-138. With geol. map.) Sum-
marized Journ. of Geol., vol. 6, p. 535.

See Williams.

CLEMENTS, J. M.

The volcanics of the Michigamme district of Michigan (preliminary).
(Journ. of Geol., vol. 3, 1895, pp. 801-822.) Summarized Journ. of
Geol., vol. 4, p. 748.

Notes on the microscopical character of certain rocks from northeast
Alabama. (Bull. Geol. Surv. Alabama, no. 5, 1896, pp. 133-176.)
Summarized Journ. of Geol., vol. 6, p. 540.

COLEMAN, A. P.

Gold in Ontario: its associated rocks and minerals. (Fourth Rept.
Bureau of Mines, Ontario, for 1894, pp. 35-100. 1895. Accom-
panied by two geol. maps of parts of the Rainy River district.) Sum-
marized Journ. of Geol., vol. 4, p. 744.

A second report on the gold fields of western Ontario. (Fifth Rept.
Bureau of Mines, Ontario, for 1895, pp. 47-106. 1896.) Summarized
Journ. of Geol., vol. 6, p. 750.

A third report on the West Ontario gold region. (Sixth Rept. Bureau
of Mines, Ontario, for 1897, pp. 71-124. 1898.) Summarized Journ.
of ‘Geol., Vol7,-). 2011.

Clastic Huronian rocks of western Ontario. (Seventh Rept. Bureau of
Mines, Ontario, for 1898, vol. 7, pp. 151-160. 1898.) Summarized
Journ.-of Geol:, vol. 7; p. 201.

Notes on the petrology of Ontario. (Seventh Rept. Bureau of Mines,
Ontario, for 1898, pp. 145-150. 1898.) Summarized Journ. of Geol.,
VOl77;, Pp; 20l.

GOLEIE.G: LE:

The geology of Conanicut Island, Rhode Island. (Trans. Wis. Acad.
Sci., vol. 10, 1895, pp. 199-230. With pl. IV.) Summarized Journ.
of Geol., vol. 4, p. 369.

796 GlKG BEIT:

Cross, WHITMAN.

On a series of peculiar schists near Salida, Colorado. (Proc. Col. Sci.
Soc., Jan., 1893, pp. I-10.) Summarized Journ. of Geol., vol. 1, p. 532.

Intrusive sandstone dikes in granite. (Bull. Geol. Soc. Am., vol. 5, 1894,
pp. 225-230.) Summarized Journ. of Geol., vol. 3, p. 227.

Pikes Peak folio.’ (Geol. Atlas of Wis 3foliomo. 7,\U. 1S: Geola Suny,
1894.) Summarized Journ. of Geol., vol. 4, p. 371.

General geology of the Cripple Creek district, Colorado. (Sixteenth
Ann. Rept. U. S. Geol. Surv., for 1894-5, part 2, pp. 13-I09. 1895.)
Summarized Journ. of Geol., vol. 6, p. 848.

See Emmons.

CULVER, G. E.
Notes on the geology of Itasca county, Minnesota. (Twenty-second
Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for 1893, part 8, pp.
97-114. 1894.) Summarized Journ. of Geol., vol. 3, p. 712.

CUSHING, H. P.

Geology of Clinton county, New York (preliminary). (Thirteenth Ann.
Rept. State Geol. of N. Y., for 1893, vol. 1, pp. 475-489. Published
also in Forty-seventh Ann. Rept. N. Y. State Museum, 1894.) Sum-
marized Journ. of Geol., vol. 6, p. 527.

On the existence of pre-Cambrian and post-Ordovician trap dikes in the
Adirondacks. (Trans. N. Y. Acad. Sci., vol. 15, 1896, pp. 248-252.)
Summarized Journ. of Geol., vol. 6, p. 528.

Report on the geology of Clinton county. (Fifteenth Ann. Rept. State
Geol. of N. Y., for 1895, vol. 1, pp. 503-573. 1898. Published also
in Forty- een Ann. Rept. N. Y. State Museum, 1895.) Summarized
Journ. of Geol., vol. 7, p. 407.

Report on the boundary between Potsdam and pre-Cambrian rocks north
of the Adirondacks. (Sixteenth Ann. Rept. State Geol. of N. Y., for
1896, pp. 1-27. 1898. With sketch map. Published also in Fiftieth
Ann. Rept. N. Y. State Museum, 1896.) Summarized Journ. of Geol.,
VOls (7; pe dOoe

Syenite-porphyry dikes in the northern Adirondacks. (Bull. Geol. Soc.
Am., vol. 9, 1898, pp. 239-256.) Summarized Journ. of Geol., vol. 7,
pp. 407.

DALE, T.N.
On the structure of the ridge between the Taconic and Green Mountain
ranges in Vermont. (Fourteenth Ann. Rept. U. S. Geol. Surv., for

1892-3, part 2, pp. 525-549. 1894.) Summarized Journ. of Geol.,
vol. 4, p. 368.

A REFERENCE LIST OF SOMMARIES 797

DALY, R. A.

Studies on the so-called porphyritic gneiss of New Hampshire. (Journ.
of Geol., vol. 5, 1897, pp. 684-722, 776-794.) Summarized Journ. of
Geol., vol. 6, p. 527.

DarTON, N. H.

Fossils in the “Archaean”’ rocks of central Piedmont, Virginia. (Am.
Journ. Sci., 3d ser., vol. 44, 1892, pp. 50-52.) Summarized Journ. of
Geol., vol..1, p..305.

Fredericksburg folio. (Geol. Atlas of U. S., folio No. 13, U. S. Geol.
Surv., 1894.) Summarized Journ. of Geol., vol. 6, p. 535.

A preliminary description of the faulted region of Herkimer, Fulton,
Montgomery, and Saratoga counties, N. Y. (Fourteenth Ann. Rept.
State Geol. of N. Y., for 1894, pp. 31-56. 1896. Published also in
the Forty-eighth Ann. Rept. N. Y. State Museum, vol. 2, 1895.) Sum-
marized Journ. of Geol., vol. 6, p. 529.

Artesian well prospects in the Atlantic coastal plain region. (Bull. U.
S. Geol. Surv., No. 138, 1896, pp. 18-19.) Summarized Journ. of
Geol., vol. 6, p. 540.

Davis, W. M.

The Triassic formation of Connecticut. (Eighteenth Ann. Rept. U.S.
Geol. Surv., for 1896-7, part 2, pp. I-Ig2. 1898. With geol. map.)
Summarized Journ of Geol., vol. 7, p. 702.

Dawson, G. M.

The physical geography and geology of Canada. (Handbook of Canada,
issued by the Publishing Committee of the Local Executive of the
British Assoc., Toronto, 1897.) Summarized Journ. of Geol., vol. 7,
D424.

Presidential address to the geological section of the British Association
for the Advancement of Science. (Proc. Brit. Assoc. Adv. Sci., for
1897, Section C, pp. 13.) Summarized Journ. of Geol., vol. 7, p. 424.

DAWSON, SIR W.

Note on Cryptozoon and other ancient fossils. (Canadian Record of Sci.,

vol. 7, pp. 203-219.) Summarized Journ. of Geol., vol. 7, p. 424.
DOWLING, D. B.

Report on the country in the vicinity of Red Lake, and part of the basin
of the Berens River, district of Keewatin. (Ann. Rept. Geol. Surv. of
Canada, for 1894, vol. 7, part F, pp. 54. 1896. With geol. map.)
Summarized Journ. of Geol., vol. 6, p. 751.

See Tyrrell.

ELDRIDGE, G. H.

Anthracite-Crested Butte folio. (Geol. Atlas of U.S., folio no. 9, U.S.

Geol. Surv., 1894.) Summarized Journ. of Geol., vol. 4, p. 371.

798 Cs IG) ILI BIIOE

A geological reconnaisance in northwest Wyoming. (Bull. U.S. Geol.
Surv., no. 11g. 1894, pp. 17. With geol. map.) Summarized Journ.
of Geol., vol. 4, p. 371.

A geological reconnaisance across Idaho. (Sixteenth Ann. Rept. U. S.
Geol. Surv., for 1894-5, part 2, pp. 217-276. 1895.) Summarized
Journ. of Geol., vol. 6, p. 847.

See Emmons.

ELFTMAN, A. H.

Preliminary report of field work during 1893 in northeastern Minnesota.
(Twenty-second Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for
1893, part 12, pp. 141-180. 1894.) Summarized Journ. of Geol.,
VOLS p71 3

Notes upon the bedded and banded structures of the gabbro and upon
an area of troctolyte. (Twenty-third Ann. Rept. Geol. and Nat. Hist.
Surv. of Minn., for 1894, part 12, pp. 224-230. 1895.) Summarized
Journ, Of Geol, ‘voli4,p..7 51.

BLES oR. Ww.

The Laurentian of the Ottawa district. (Bull. Geol. Soc. of Am., vol. 4,
1893, pp. 349-360.) Summarized Journ. of Geol., vol. 2, p. 109.

Mica deposits in the Laurentian of the Ottawa district. (Bull. Geol.
Soc. of Am., vol. 5, 1894, pp. 481-488.) Summarized Journ. of Geol.,
VOli 35 ps2s2:

Report on a portion of the Province of Quebec, comprised in the south-
west sheet of the ‘“ Eastern Townships” map (Montreal sheet). (Ann.
Rept. Geol. Surv. of Canada for 1894, vol. 7, part J, pp. 1-92. 1896).
Summarized Journ. of Geol., vol. 6, p. 849.

Notes on the Archean of eastern Canada.. (Proc. and Trans. Royal
Soc. of Canada, 2d ser., vol. 3, 1897, sec. 4, pp. 117-124.) Summarized
Journ. of Geol., vol. 7, p. 414.

—— and BARLow, A. E.

The physical features and geology of the route of the proposed Ottawa
canal between the St. Lawrence river and Lake Huron. (Proc. and
Trans. Royal Soc. of Canada, 2d ser. vol. 1, 1895, sec. 4, pp. 163—I90.
With sketch map.) Summarized Journ. of Geol., vol. 6, p. 852.

EMERSON, B. K.

Hawiey sheet. (Geol. Atlas of U. S., preliminary publication of the
Hawley sheet, U. S. Geol. Surv., 1894.) Summarized Journ. of Geol.,
voli 45 p. 307:

Geology of Old Hampshire county in Massachusetts. (Abstract in Bull.
Geol. Soc. Am., vol. 7, 1896, pp. 5-7.) Summarized Journ. of Geol.,
vol. 4, p. 368.

A REFERENCE LIST OF SUMMARIES 799

Emmons, S. F., Cross, W., and ELDRIDGE, (Gy, Bl,
Geology of the Denver basin in Colorado. (Mon. U. S. Geol. Surv. no.
27, 1896, pp. 556. With geol. map.) Summarized Journ. of Geol.,
vol. 6, p. 848.
FERRIER, W. T. See Barlow.
MINEAY J. Ry oce smyth, A. L.
FRAZER, P.

Notes on the northern Black Hills of South Dakota. (Am. Inst. Min.
Engineers, vol. 27, 1898, pp. 204-228.) Summarized Journ. of Geol.,
VOl: 7,,p- 700.
GiBson, T. W.
The hinterland of Ontario. (Fourth Rept. Bureau of Mines, Ontario,
for 1894, sec. 3, part on pp. 124-125. 1895.) Summarized Journ.
of Geol., vol. 4; p. 744.
GILBERT, G. K.
Pueblo folio. (Geol. Atlas of U.5., folio, no. 36, U. S. Geol., Surv;
1897.) Summarized Journ. of Geol., vol. 7, p. 706.

GRANT, U.S.

The stratigraphic position of the Ogishke conglomerate of northeastern
Minnesota. (Am. Geol., vol. 10, 1892, pp. 4-10.) Summarized Journ.
of Geol., vol. I, p. 309.

Field observations on certain granitic areas in northeastern Minnesota.
(Twentieth Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for 1891,
pp. 35-I10. 1892.) Summarized Journ. of Geol., vol. 2, p. 448.

The geology of Kekequabik lake in northeastern Minnesota, with special
reference to an augite soda granite. (A thesis accepted for the degree
of Ph.D. in The Johns Hopkins University, 1893. Published in
twenty-first Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for 1892,
pp. 5-58. 1893. With geol. map and plates). Summarized Journ.
of Geol., vol. 7, p. 107.

Preliminary report of field work during 1893 in northeastern Minnesota.
(Twenty-second Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for
1893, part 4, pp. 67-78. 1894.) Summarized Journ. of Geol., vol. 3,
P7100.

Note on the Keweenawan rocks of Grand Portage Island, north coast of
Lake Superior. (Am. Geol., vol. 13, 1894, pp. 437-438). Summarized
Journ. of Geol., vol. 3, p. 715.

Sketch of the geology of the eastern end of the Mesabi iron range in
Minnesota. (Engineers’ Year Book, Univ. of Minn., 1898, pp. 49-62.
With sketch map.) Summarized Journ. of Geol., vol. 7, p. 198.

See Winchell, H. V.

800 CK ELE TREE

GRESLEY, W. S.

Organic markings in Lake Superior iron ores. (Science, new ser.,
vol., 3, 1896, pp. 622-623.) Summarized Journ. of Geol., vol. 6,
p. 748.

GRIMSLEY, G. P.

The granites of Cecil county, innortheastern Maryland. (Journ. of Cin-
cinnati Soc. Nat. Hist., April and July, 1894, pp. 50.) Summarized
Journ. of Geol., vol. 3, p. 236.

GRISWOLD les:

The geology of Helena, Montana, and vicinity. Journ. of the Assoc. of
Engineering Societies, vol. 20, 1898, pp. 1-18.) Summarized Journ.
of Geol, vol. 7, p.. 706.

HAGugE, A.

The age of the igneous rocks of the Yellowstone National Park. (Am.
Journ. Sci., 4th ser., vol. 1, 1896, pp. 445-457.) Summarized Journ.
of Geol., voi. 6, p. 847.

—— with WEED, W.H., and IDDINGs, J. P.

Yellowstone National Park folio. (Geol. Atlas of U.S., folio no. 30, U.

S. Geol. Surv., 1896.) Summarized Journ. of Geol., vol. 6, p. 846.
HALL, C. W. and SARDESON, F. W.

Paleozoic formations of southeastern Minnesota. (Bull. Geol. Soc. Am.,

vol. 3, 1892, pp. 331-368.) Summarized Journ. of Geol. vol. 1, p. 308.
HAWES, G. W.

Notes on the microscopic characters of the Alabama crystalline or
metamorphic rocks. (Bull. Geol. Surv. of Alabama, no. 5, 1896, pp.
131-132.) Summarized Journ. of Geol., vol. 6, p. 540.

HAWORTH, E.

The crystalline rocks of Missouri. (Missouri Geol. Surv., vol. 8, 1895,
pp. 84-222. With geol. map.) Summarized Journ. of Geol., vol. 4.
P- 379.

Report on the Iron Mountain sheet—the Archean rocks. (Missouri
Geol. Surv., vol. 9, 1896, pp. 15-27. With sheet no. 3.) Summarized
Journ. of Geol!,'vol. 6,’ ps (841.

See Keyes.

Haves, C. W.

Cleveland folio. (Geol. Atlas of U.S., folio no. 20, U.S. Geol. Surv.,

1895.) Summarized Journ. of Geol., vol. 6, p. 537.
Isbomty IRS Ih.

Notes on a reconnaissance of the Ouachita mountain system in Indian
Lernitory: (Am: Journ Sei: 3d ser., vol. 42, 1891, pp. 11-124.)
Summarized Journ. of Geol., vol. 4, p. 370.

A REFERENCE LIST OF SUMMARIES Sol

Hirrencock, ©. iH:

The geology of New Hampshire. (Journ. of Geol., vol. 4, 1896, pp. 44-

62.) Summarized Journ. of Geol., vol. 6, p. 527.
HOLLICK, A. See-Kemp.
FLOVE Vay td ne.

Geological notes on the Isles of Shoals. (Abstract.) (Proc. Am. Assoc.
Adv. Sci., for 44th meeting, 1895, pp. 136-137.) Summarized Journ.
of Geol: vol. 6, p. 527. .

HUBBARD, L. L.

Two new geological cross-sections of Keweenaw Point. (Proc. Lake
Superior Min. Inst., vol. 2, 1894, pp. 79-96.) Summarized Journ. of
Geol, vol, .p.7 52.

The relation of the vein at the Central Mine, Keweenaw Point, to the
Kearsarge conglomerate. (Proc. Lake Superior Min. Inst., vol. 3,
1895, pp. 74-83.) Summarized Journ. of Geol., vol. 6, p. 749.

Munsr N:P.

The geology of that portion of the Menominee range east of the Menom-
inee river. (Proc. Lake Superior Min. Inst., 1893, pp. 19-29.) Sum-
marized Journ. of Geol., vol. 2, p. 452.

IDDINGS, J. P., WEED, W. H., and HAGUE, A.

Livingston folio. (Geol. Atlas of U.S., folio no. 1, U.S. Geol. Surv.,
1894.) Summarized Journ. of Geol., vol. 4, p. 370.

See Hague.

KEITH, A.

The geology of the Catoctin belt. (Fourteenth Ann. Rept. U.S. Geol.
Surv., for 1892-3, part 2, pp. 285-395, 1894; and Geol. Atlas of U.S.,
Harper’s Ferry folio, no. 10, 1894.) Summarized Journ. of Geol., vol.
4, p. 369.

Knoxville and Loudon folios. (Geol. Atlas of U. S., folios nos. 16 and
25, U.S. Geol. Surv., 1895 and 1896.) Summarized Journ. of Geol.,
vol. 6, p. 536.

KEmpP, J. F.

The ore deposits at Franklin Furnace and Ogdensburg. (Trans. N. Y.
Acad. Sci., vol. 13, 1893, pp. 76-98.) Summarized Journ. of Geol.,
vol..6, p. 530.

Geology of Essex county (preliminary). (Thirteenth Ann. Rept. of
State Geol. of N. Y., for 1893, vol. 1, pp. 433-472. Published also in
47th Ann. Rept. N. Y. State Museum, 1894. See The Geology of
Moriah and Westport townships, Essex county. (Bull. N. Y. State
Museum, vol. 3, 1895, pp. 325-351. With geol. map.) See Illustra-
tions of the dynamic metamorphism of anorthosites and related

802 Coke, IGEITCE,

rocks on the Adirondacks. (Abstract in Bull. Geol. Soc. Am., vol. 7,
1896, pp. 488-490.) Summarized Journ. of Geol., vol. 6, p. 528.

Gabbros on the western shore of Lake Champlain. (Bull. Geol. Soc. Am.,
vol. 5, 1894, pp. 213-224.) Summarized Journ. of Geol., vol. 3, p. 234.

The geological section of the East River, at Seventieth street, New York.
(Trans. N. Y. Acad. Sci., vol. 14, 1895, pp. 273-276.) Summarized
Journ. of Geol., vol. 6, p. 520.

Crystalline limestones, ophicalcites, and associated schists of the eastern
Adirondacks. (Bull. Geol. Soc. Am., vol. 6, 1895, pp. 241-262.)
Summarized Journ. of Geol., vol. 4, p. 366.

The titaniferous iron ores of the Adirondacks. (Abstract in Bull. Geol.
Soc. Am., vol. 7,1896, p. 15.) Summarized Journ. of Geol., vol. 4, p. 367.

The geology of the magnetites near Port Henry, New York. (Trans.
Am. Inst. Min. Engineers, vol. 27, 1898, pp. 146-203.) Summarized
Journ. of 'Geol-; voli 6;1p.7520.

Preliminary report on the geology of Essex county. (Fifteenth Ann.
Rept. of the State Geol. of N. Y., for 1895. 1898. Published also in
Forty-ninth Ann. Rept. N. Y. State Museum, 1895. With geol. map.)
Summarized Journ. of Geol., vol. 7, p. 409.

Geology of the Lake Placid region. (Bull. N. Y. State Museum, vol. 5,
no. 21, 1898, pp. 51-64. With geol. map.) Summarized Journ. of
Geol., vol. 7, p. 409.

KEMP, J. F., and HOLELick,.A:

Granite at Mounts Adam and Eve, Warwick, Orange county, New York,
and its contact phenomena. (Annals N. Y. Acad. Sci., vol. 7, 1892-4,
pp. 638-654.) Summarized Journ. of Geol., vol. 3, p. 235.

and MARSTERS, F. V.

The trap dikes of the Lake Champlain region. (Bull. U.S. Geol. Surv.,
no. 107, 1893, pp. 62. With geol. map.) Summarized Journ. of Geol.,
vol. 4, pp. 367.

NEVES Gk

Some Maryland granites and their origin. (Bull. Geol. Soc. Am., vol. 4,
1893, pp. 299-304.) Summarized Journ. of Geol., vol. 2, p. 117.

Characteristics of the Ozark Mountains. (Missouri Geol. Surv., vol. 8,
1895, pp. 317-352.) Summarized Journ. of Geol., vol. 6, p. 841.

Opinions concerning the age of the Sioux quartzite. (Proc. lowa Acad.
Sci. for 1894, vol. 2, pp. 218-222. 1895.) Summarized Journ. of
Geol., vol. 6, p. 840.

Origin and relations of central Maryland granites, with an introduction on
the general relations of the granitic rocks in the middle Atlantic Piedmont
Plateau by G.H. Williams. (Fifteenth Ann. Rept. U.S. Geol. Surv. for
1893-4, pp. 685-740. 1895.) Summarized Journ. of Geol., vol. 6, p. 535.

A REFERENCE LIST OF SUMMARIES 803

Geographic relations of the granites and porphyries in the eastern part
of the Ozarks. (Bull. Geol. Soc. .Am., vol. 7, 1896, .pp: 363-375.)
Summarized Journ. of Geol., vol. 6, p. 842.

Geological occurrence of clays, in connection with a report on the clay
deposits of Missouri, by Wheeler. (Missouri Geol. Surv., vol. 9, 1896,
pp. 36-37.) Summarized Journ. of Geol., vol. 6, p. 843.

KEYES, C. R. and HAworTH, E.

Report on the Mine Le Mot sheet—General geology (Keyes); Archean
geology (Haworth). (Rept. Missouri Geol. Surv., vol. 9, 1896, pp.
14-44. With sheet no. 4.) Summarized Journ. of Geol., vol. 6,
p- 842.

KIMBALL, J. P.
The magnetite belt at Cranberry, North Carolina. (Am. Geol., vol. 20,
1897, pp. 299-312.) Summarized Journ. of Geol., vol. 6, p. 536.

KING, F. P.
Corundum deposits of Georgia; Chapter IV, Geology of the crystalline
belt. (Bull. Geol. Surv. of Ga., no. 2, 1894, pp. 58-72.) Summarized
Journ. of Geol., vol. 6, p. 538.

LAKES, ARTHUR.
Sketch of a portion of the Gunnison gold belt, including the Vulcan and
Mammoth Chimney mines. (Trans. Am. Inst. Min. Engineers,
vol. 26, 1897, pp. 440-448.) Summarized Journ. of Geol., vol. 7,
pa707.

LANE, A. C.
On microscopic characters of rocks and minerals of Michigan. (Rept.
State Board Geol. Surv. of Mich., for 1891-2, pp. 176-183. 1893.)
Summarized Journ. of Geol., vol. 1, p. 539.

LAwson, A. C.

Sketch of the coastal topography of the north side of Lake Superior,
with special reference to the abandoned strands of Lake Warren.
(Twentieth Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., for 1891, pp.
181-289. 1892.) Summarized Journ. of Geol., vol. 2, p. 444.

The Norian rocks-of Canada. (Science, old ser., vol. 21, 1893, pp.
281-282.) Summarized Journ. of Geol., vol. 2, p. 114.

On anorthosites of the Minnesota coast of Lake Superior. (Bull. Geol.
and Nat. Hist. Surv. of Minn., no. 8, 1893, pp. I-23.) Summarized
Journ. of Geol., vol. I, p. 310.

On the laccolitic sills of the northwest coast of Lake Superior. (Bull.
Geol. and Nat. Hist. Surv. of Minn., no. 8, 1893, pp. 24-48.) Sum-
marized Journ. of Geol., vol. 1, p. 313.

804 (Ge KG IAB T a!

Multiple diabase dyke. (Am. Geol., vol. 13, 1894, pp. 293-296.) Sum-
marized Journ. of Geol., vol. 3, p. 715.

The geology of Carmelo Bay. (Bull. Dept. of Geol., Univ. of Cal., vol. 1,
1893-6, pp. 1-59.) Summarized Journ. of Geol., vol. 2, p. 118.

Malignite, a family of basic plutonic rocks rich in alkalies and lime.
(Bull. Dept. of Geol., Univ. of Cal., vol. 1, 1893-6, pp. 337-362.) Sum-
marized Journ. of Geol., vol. 6, p. 750.

IEE SIE Ven jeube.

On Laurentian and Huronian formations. (In Summary Rept. Geol.
Surv. of Pa., vol. 1, 1892, pp. 53-164.) Summarized Journ. of Geol.,
vol. 1, pp. 305-6.

Low, A. P.

Report on the geology and economic minerals of the southern portion of
Portneuf, Quebec, and Montmorency counties, province of Quebec.
(Ann. Rept. Geol. Surv. of Canada for 1890-1, vol. 5, part L, pp. Boe
1892.) Summarized Journ. of Geol., vol. 3, p. 230.

Report on explorations in the Labrador peninsula, along the East Main,
Koksoak, Hamilton, Manicuagan, and portions of other rivers, in 1892,
1893, 1894, and 1895. (Ann. Rept. Geol. Surv. of Canada, for 1895,
vol. 8, part L, pp. 387. 1897. With geol. map.) Summarized Journ.
of Geol:, voly7, p. 420.

Report on a traverse of the northern part of the Labrador peninsula,
from Richmond Gulf to Ungava Bay. (Ann. Rept. Geol. Surv. of
Canada, for 1896, vol. 9, part L, pp. 1-43. 1898. With geol. map.)
Summarized Journ. of Geol., vol. 7, p. 422.

MARSTERS, F.V.- See Kemp.

MATTHEW, W. D.

The intrusive rocks near St. John, New Brunswick. (Trans. N. Y. Acad.
Sci., vol. 13, 1894, pp. 185-203.) Summarized Journ. of Geol., vol. 3,
D232:

The effusive and dyke rocks near St. John, New Brunswick. (Trans.
N. Y. Acad. Sci., vol. 14, 1895, pp. 187-217.) Summarized Journ. of
Geol., vol. 4, p. 362.

McConngELL, R. G.

Report on a portion of the district of Athabasca, comprising the country
between Peace river and Athabasca river, north of Lesser Slave Lake.
(Ann. Rept. Geol. Surv. of Canada, for 1890-1, vol. 5, part D, pp.
5-62. 1893.) Summarized Journ. of Geol., vol. 3, p. 228.

Report on an exploration of the Finlay and Omenica rivers. (Ann.
Rept. Geol. Surv. of Canada, for 1894, vol. 7, part C, pp. 40. 1896.)
Summarized Journ. of Geol., vol. 6, p. 843.

A REFERENCE LIST OF SUMMARIES 805

f

MirRRTE ES be fe kL: f

Geol. map of New York, published with report on Mineral Resources of
New York State. (Bull. N. Y. State Museum, vol. 3, no. 15, 1895,
pp. 365-595.) Summarized Journ. of Geol., vol. 6, p. 530.

The geology of the crystalline rocks of southeastern New York. (Rept.
N. Y. State Museum, 1896, pp. 21-44.) Summarized Journ. of Geol.,
VOl.-7; ps 702:

Geological map of New York, published with report on Road Materials.
(Bull. N. Y. State Museum, vol. 4, no. 17, 1897, pp. 90-134.) Sum-
marized Journ. of Geol., vol. 6, p. 530.

MERRILL, G. P.

Disintegration of the granitic rocks of the District of Columbia. (Bull.
Geol. Soc. Am., vol. 6, 1895, pp. 321-332.) Summarized Journ. of
Geol., vol. 4, p. 370.

MILLER, W. G.

Economic geology of eastern Ontario—corundum and other minerals.
(Seventh Rept. of Bureau of Mines, Ontario, for 1898, vol. 7, pp. 207—
238. 1898.) Summarized Journ. of Geol., vol. 7, p. 411.

MinreaTES 3 sine

Stratigraphy and succession of the rocks of the Sierra Nevada of Cali-
fornia. (Bull. Geol. Soc. Am., vol. 3, 1892, pp. 413-444.) Sum-
marized Journ. 6f Geol., vol. 1, p. 305.

NASON, F. L.

On iron ores of Missouri. (Rept. Missouri Geol. Surv., vol. 2, 1892, pp.
16-69.) Summarized Journ. of Geol., vol. I, p. 306.

On some of the iron-bearing rocks of the Adirondack Mountains. (Am.
Geol., vol. 12, 1893, pp. 25-31.) Summarized Journ. of Geol., vol. 2,
p. 113.

The chemical composition of some of the white limestones of Sussex
county, New Jersey. (Am. Geol., vol. 13, 1894, pp. 154-164.) Sum-
marized Journ. of Geol., vol. 3,,p. 235.

Summary of facts proving the Cambrian age of the white limestones of
Sussex county, New Jersey. (Am. Geol., vol. 14, 1894, pp. 161-168.)
Summarized Journ. of Geol., vol. 3, p. 235.

NEWETT, G. A.

The Marquette iron range of Michigan. (Proc. Lake Superior Min.
Inst., vol. 3, 1895, pp. 87-108. With geol. map.) Summarized Journ.
of Geol:, vol. 6,p. 745.

Norton, W. H. ;
Artesian wells of Iowa. (Geol. Surv. of Iowa, vol. 6, 1897, The Algon-
kian, pp. 139-140.) Summarized Journ. of Geol., vol. 7, p. 705.

806 CLG TMT:

OSANN, A.

Beitrage zur Geologie und Petrographie der Apache (Davis) Mountains,
Westtexas. (Min. und Pet. Mitt., Bd. 15, Heft 5, 1896, pp. 394-486.)
Summarized Journ. of Geol., vol. 6, p. 849.

PARKS, W. A.

Geology of base and meridian lines in the Rainy river district. (Seventh
Rept. Bureau of Mines, Ontario, for 1898, vol. 7, pp. 161-183. 1898.
With geol. map.) Summarized Journ. of Geol., vol. 7, p. 205.

PEALE, A. C.

The Paleozoic section in the vicinity of Three Forks, Montana. (Bull.
U.S. Geol. Surv., no. 110, 1803, pp.156:), Summarized journyeot
Geol vol, pei22i7,.

Three Forks folio. (Geol. Atlas of U.S., folio no. 24, U. S. Geol. Surv.,
1896.) Summarized Journ. of Geol., vol. 6, p. 844.

Prirsson, L. V.
See Weed.

RIES, H.

The geology of Orange county, N. Y. (Fifteenth Ann. Rept. State Geol.
of N. Y., for 1895, pp. 395-475. With geol. map. Published also
in Forty-ninth Ann. Rept. N. ¥Y. State Museum, 1895.) Summarized
Journ. of Geol., vol. 7, p. 703.

RUSSEL. ils G:

A geological reconnoissance in central Washington. (Bull. U.S. Geol.
Surv., no. 108, 1893, pp. 20. With geol. map.) Summarized Journ. of
Geol., vol. 4, p. 370.

SAPPER, C.

Grundziige der physikalischen Geographie von Guatemala. (J. Perthes’
Geog. Anst., Erganzungsheft, Nr. 113, 1894, pp. 59. With geol.
maps.) Summarized Journ. of Geol., vol. 4. p. 372.

Geology of Chiapas, Tabasco, and the peninsula of Yucatan. (Journ. of
Geol., vol. 4, 1896, pp. 938-947.) Summarized Journ. of Geol., vol. 6,
p- 849.

SARDESON, F. W.

See Hall.

SEARS,) J. H.

Report on the geology of Essex county, Massachusetts, to accompany
map. (Bull. Essex Inst., vol. 26, 1894, pp. 118-139.) Summarized
Journ-of Geol. vol:4;.p..367

SMITH, E. A.

A general account of the character, distribution, and structure of the

crystalline rocks of Alabama, and of the mode of occurrence of the

A REFERENCE LIST OF SUMMARIES 807

gold ores. (Bull. Geol. Surv. of Alabama, no. 5, 1896, pp. 108-130.)
Summarized Journ. of Geol., vol. 6, p. 5309.

Smi1tTH, W. H. C.

Report on the geology of Hunters Island and adjacent country. (Ann.
Rept. Geol. Surv. of Canada, for 1890-1, vol. 5, part G, pp. 5-76.
1892.) Summarized Journ. of Geol., vol. 3, p. 709.

The Archean rocks west of Lake Superior. (Bull. Geol. Soc. Am., vol. 4,
1893, pp. 333-348.) Summarized Journ. of Geol., vol. 2, p. 115.

. SMYTH, C. H., Jr.

A geological reconnoissance in the vicinity of Gouverneur. (Trans. N.
Y. Acad. Sci., vol. 12, 1893, pp. 97-108.) Summarized Journ. of Geol.
VOls Teps5 32:

Petrography of the gneisses of the town of Gouverneur, New York.
(Trans. N. Y. Acad. Sci., vol. 12, 1893, pp. 203-217.) Summarized
Journ of Geol., vol. 2; p. 117.

A group of diabase dikes among the Thousand Islands, St. Lawrence
river, (Trans..N. Y. Acad. Sci., vol. 13, 1893-4, pp. 209-214.)
Summarized Journ. of Geol., vol. 6, p. 854.

Gabbros in the southwestern Adirondack region. (Am. Journ. Sci., 3d
ser., vol. 48, 1894, pp. 54-80.) Summarized Journ. of Geol., vol. 3, p. 234.

Crystalline limestones and associated rocks of the northwestern Adiron-
dacks. (Bull. Geol. Soc. Am., vol. 6, 1895, pp. 263-284.) Summarized
Journ. of Geol.,;vol. 4, p. 365.

Report on the crystalline rocks of St. Lawrence county. (Fifteenth Ann.
Rept. State Geol. of N. Y., for 1895, vol. 1, pp. 481-487. 1898. Pub-
lished also in 4oth Ann. Rept. N. Y. State Museum, re Sum-
marized Journ. of Geol., vol. 7, p. 406.

SmyTH, H. L.

A contact between the Lower Huronian and the underlying granite in
the Republic Trough, near Republic, Michigan. (Journ. of Geol., vol.
1, 1893, pp. 268-274.) Summarized Journ. of Geol., vol. 2, p. 446.

Relations of the Lower Menominee and Lower Marquette series of Mich-
igan (preliminary). (Am. Journ. Sci., 3d ser., vol. 47, 1894, pp. 216-
223.) Summarized Journ. of Geol., vol. 4, p. 748.

The quartzite tongue at Republic, Michigan. (Journ. of Geol., vol. 2,
1894, pp. 680-691.) Summarized Journ. of Geol., vol. 4, p. 747.

and -FINLAY, JR:

The geological structure of the western part of the Vermilion range,
Minnesota. (Trans. Am. Inst. Min. Engineers, vol. 25, 1895, pp. 595—
645.) Summarized Journ. of Geol., vol. 4, p. 746.

See Van Hise.

808 G51, SEIT ICTEL

SPURR, J. E.

The iron-bearing rocks of the Mesabi range in Minnesota. (Bull. Geol.
& Nat. Hist. Surv. Minn., no. 10, 1894, pp. 268. With geol. maps.)
Summarized Journ. of Geol., vol. 3, p. 716.

The stratigraphic position of the Thompson slates. (Am. Journ. Sci., 3d
ser., vol. 48, 1894, pp. 159-165.) Summarized Journ. of Geol., vol. 3,
ps2:

LODD, las:

A preliminary report on the geology of South Dakota. (Bull. South
Dak. Geol. Surv., no. 1, 1895, pp. 172. Withgeol. map.) Summarized
Journ. of Geol., vol. 6, p. 840.

Section along Rapid Creek from Rapid City westward. (Bull. South

Dak. Geol. Surv., no. 2, 1898, pp. 27-40.) Summarized Journ. of
Geol. vols 37,2700.

PYRRELE |EeB:

Report on the Doobaunt, Kazan, and Ferguson rivers, and on the north-
west coast of Hudson Bay. (Ann. Rept. Geol. Surv. of Canada, for
1896, vol. 9, part F, pp. 218. 1898. With geol.map.) Summarized
Journ of Geol. vols 7..p.14205 5

and DowLING, D. B.

Report on the country between Athabasca Lake and the Churchill river
in Canada. (Ann. Rept. Geol. Surv. of Canada, for 1895, vol. 8, part
D, pp. 120. 1897. With geol.map.). Summarized Journ. of Geol.,
vol. 7, p. 419. ,

NANG EDT SIE Gene

An historical sketch of the Lake Superior region to Cambrian time.

(Journ. of Geol., vol. 1, 1893, pp. 113-128. With geol. map.) Sum-
marized Journ. of Geol., vol. 2, p. 445.

Some dynamic phenomena shown by the Baraboo quartzite ranges of cen-
tral Wisconsin. (Journ. of Geol., vol. 1, 1893, pp. 347-355.) Sum-
marized Journ. of Geol., vol. 2, p. 117.

The Huronian volcanics south of Lake Superior. (Abstract in Bull.
Geol. Soc. Am., vol. 4, 1893, pp. 435-436.) Summarized Journ. of
Geol.) volsi2)..p. 454"

Character of the folds in the Marquette iron district. (Abstract in Proc.
Am. Assoc. Adv. Sci., for 42d meeting, 1893, p. 171.) Summarized
Journ. of Geol., vol. 4, p. 748.

The succession in the Marquette iron district of Michigan. (Abstract
in Bull. Geol. Soc. Am., vol. 5, 1894, pp. 5-6.) Summarized Journ.
of Geol., vol. 2, p. 453.)

A central Wisconsin baselevel. (Science, new ser., vol. 4, 1896, pp. 57—
59.) Summarized Journ. of Geol. vol. 6, p. 749.

A northern Michigan baselevel. (Science, new ser., vol. 4, 1896, pp.
217-220.) Summarized Journ. of Geol., vol. 6, p. 749.

A REFERENCE LIST OF SUMMARIES 809

VAN HIsE, C. R., with BAYLEY and SMYTH.
The Marquette iron-bearing series of Michigan. (Mon. U.S. Geol. Surv.,
no. 28, 1896, pp. 608. With geol. atlas of 39 plates.) Summarized
Journ. of Geol., vol. 6, p. 739.

WADSWORTH, M. E.

On subdivisions of the Azoic or Archean in northern Michigan. (Am.
Journ. of Sci., 3d ser., vol. 45, 1893, pp. 72-73.) Summarized Journ. of
Geol:, vol. 1, p: 533.

On geology of the iron, gold, and copper districts of Michigan. (Rept.
State Board Geol. Surv. of Mich., for 1891-2, pp. 75-174. 1893.)
Summarized Journ. of Geol., vol. 1, p. 534.

The origin and mode of occurrence of the Lake Superior copper deposits.
(Trans. Am. Inst. Min. Engineers, vol. 27, 1898, pp. 669-696.) Sum-
marized Journ. of Geol., vol. 7, p. Igo.

WALCOLT GC. 1),

Algonkian rocks of the Grand Canyon of the Colorado. (Journ. of Geol.,
vol. 3, 1895, pp. 312-330. Published also in Fourteenth Ann. Rept.
U.S. Geol. Surv., for 1892-3, part 2, pp. 487-524. 1895.) Summarized
journ:ot Geoli vol; 4, p..372:

WALKER, DE.

Geological and petrographieal studies of the Sudbury nickel district of
Canada. (Quart. Journ. Geol. Soc., vol. 53, 1897, pp. 40-66.. With
geol. map.) Summarized Journ. of Geol., vol. 7, p. 416.

WEED, W. H.,-and Prrsson, L. V.

Geology of the Castle Mountain mining district, Montana. (Bull. U.S.
Geol. Surv., no. 139, 1896, pp. 165. With geol. map.) Summarized
Journ. of Geol., vol. 6, p. 845.

The geology of the Little Rocky mountains. (Journ. of Geol., vol. 4,
1896, pp. 399-428.) Summarized Journ. of Geol., vol. 6, p. 846.

See Hague.

WEIDMAN, S.

On the quartz keratophyre and associated rocks of the north range of the
Baraboo Bluffs. (Bull. Univ. of Wis., sci. ser., vol. 1, 1895, pp. 35-56.)
Summarized Journ. of Geol., vol. 4, p. 750.

A contribution to the geology of the pre-Cambrian rocks of the Fox River
Valley, Wis. (Bull. Wis. Geol. and Nat. Hist. Surv., no. 3, 1898, pp.
63.) Summarized Journ. of Geol., vol. 7, p. 704.

WESTGATE, L. G.

The age of the crystalline limestones of Warren county, New Jersey. (Am.
Geol., vol. 14, 1894, pp. 369-379.) Summarized Journ. of Geol., vol. 3,
Ds 230.

The geology of the northern part of Jenny Jump Mountain, Warren
county. (Ann. Rept. Geol. Surv.of N. J., for 1895, pp. 21-61. 1896.)
Summarized Journ. of Geol., vol. 6, p. 531.

81I0o Cn IK, IEIBIOIE

WHITE, T.G.

The geology of Essex and Willsboro’ townships, Essex county, New York.
(Trans. N. Y. Acad. Sci., vol. 13, 1894, pp. 214-233.) Summarized
Journ. of Geol., vol. 6, p. 528.

\WWasiiariniijo, (Es IL, ;

The occurrence of Algonkian rocks in Vermont and the evidence for their
subdivision. (Journ. of Geol., vol. 2, 1894, pp. 396-429.) Sum-
marized Journ. of Geol., vol. 3, p. 233.

General structure of the main axis of the Green Mountains. (Am. Journ.
Sci., 3d ser., vol. 47, 1894, pp. 347-354.) Summarized Journ. of Geol.,
VO 3s sh232'

WILLIAMS, G. H.

Notes on the microscopical character of rocks from the Sudbury mining
district, Canada. (Ann. Rept. Geol. Surv. of Canada, for 1890-1, vol.
5, part F, App. I, pp. 55-82. 1893.) Summarized Journ. of Geol., vol.
I, p. 541.

General relations of the granitic rocks in the middle Atlantic Piedmont
plateau. (Introduction to origin and relation of central Maryland
granites, byC. R. Keyes, Fifteenth Ann. Rept. U. 5S. Geol. Surv., for
1893-4, pp. 659-684. 1895.) Summarized Journ. of Geol., vol. 6, p. 533.

and CLARK, W. B.

Geology and physical features of Maryland. (Extract from World’s Fair

Book on Maryland; Baltimore, 1893, pp. 1-67. With geol. map.) Sum-
marized Journ. of Geol., vol. 6, p. 532.

WILLMOTT, A. B.

The Michipicoton mining division. (Seventh Rept. Bureau of Mines,
Ontario, for 1898, vol. 7, pp. 184-206. 1898.) Summarized Journ. of
Geol., vol. 7, p. 415.

WINCHELL, A.

The Koochiching granite. (Am. Geol., vol. 20, 1897, pp. 293-299.) Sum-
marized Journ. of Geol., vol. 7, p. 200.

WINCHELL, H. V.

On the Mesabi iron range. (Twentieth Ann. Rept. Geol. and Nat. Hist.
Surv. Minn., for 1891, pp. 11-180. 1892. See also Proc. Am. Inst. Min.
Engineers, vol. 21, 1893, pp. 644-685 and 951-961.) Summarized
Journ. of Geol., vol. 2, p. 449.

The iron ranges of Minnesota. (Proc. Lake Superior Min. Inst., vol. 3,
1895, pp. 11-32.) Summarized Journ. of Geol., vol. 6, p. 750.

and GRANT, U. S.

Preliminary report on the Rainy Lake gold region. (Twenty-third Ann.
Rept. Geol. and Nat. Hist. Surv. Minn., for 1894, part 2, pp. 36-105.
1895.) Summarized Journ. of Geol., vol. 4, p. 745.

A REFERENCE LIST OF SOMMARIES SII

WINCHELL, N. Hi.

The crystalline rocks. (Twentieth Ann. Rept. Geol. and Nat. Hist. Surv.
Minn., for 1891, pp. 1-28. 1892.) Summarized Journ. of Geol., vol. 2,
p. 446.

On the Norian of the northwest. (Prefatory note to Bull. Geol. and Nat.
Hist. Surv. Minn., no. 8, 1893, pp. iii-xxii.) Summarized Journ. of
Geolsavoliai,, p..300.

The origin of the Archean greenstones. (Twenty-third Ann. Rept. Geol.
and Nat. Hist. Surv. Minn., for 1894, part 2, pp. 4-35. 1895.) Sum-
marized Journ. of Geol., vol. 4, p. 753.

Crucial points in the geology of the Lake Superior region. (Am. Geol.,
vol. 15, 1895, pp. 153-162, 229-234, 295-304, 356-363; and vol. 16,
1895, pp. 12-20, 75-86, 150-162, 269-274, 331-337.) Summarized
Journ. of Geol., vol. 4, p. 754.

Some new features in the geology of northeastern Minnesota. (Am.
Geol., vol. 20, 1897, pp. 41-51.) Summarized Journ. of Geol., vol. 7,
p- 194.

The origin of the Archean igneous rocks. (Abstract in Proc. Am. Assoc.
Adv. Sci., vol. 47, 1898, pp. 303-304. Published also in Am. Geol.,
vol. 22, 1898, pp. 299-310.) Summarized Journ. of Geol., vol. 7,
p-. 194.

The oldest known rock. (Abstract in Proc. Am. Assoc. Adv. Sci., vol.
47, 1898, pp. 302-303.) Summarized Journ. of Geol., vol. 7, p. 193.
The significance of the fragmental eruptive débris at Taylor’s Falls,
Minnesota. (Am. Geol., vol. 22, 1898, pp. 72-78.) Summarized Journ.

of Geol. vol: 7; p. 192:

Some resemblances between the Archean of Minnesota and of Finland.
(Am. Geol., vol. 21, 1898, pp. 222-229.) Summarized Journ. of Geol.,
Vl, ps1 05:

WINSLow, A.
The geology and mineral products of Missouri. (From “ Missouri at the
World’s Fair.” Official publication of the World’s Fair Commission
of Missouri.) Summarized Journ. of Geol., vol. 2, p. 117.

WOLFF, J. E.

Geological structure in the vicinity of Hibernia, New Jersey. (Ann.
Rept. Geol. Surv. of N. J., for 1893, pp. 359-369. 1895.) Summarized
Journ. of Geol., vol. 4, p. 369.

Report on Archean geology: the eruptive rocks of Sussex county, New
Jersey, with reference to their economic value. (Ann. Rept. Geol.
Surv. of N. J., for 1896, pp. 91-94. 1897. With map.) Summarized
Journ. of Geol., vol. 6, p. 531.

812 CGE ETT

WotFr, J. E. and Brooks, A. H.
The age of the Franklin white limestone of Sussex county, New Jersey.
(Eighteenth Ann. Rept. U.S. Geol. Surv., for 1896-7, part 2, pp. 425-
457. 1898. With geol. map.) Summarized Journ. of Geol., vol. 7,

p- 703.

WRITERS CLASSIFIEDIBY REGIONS:

THE ORIGINAL LAURENTIAN AND HURONIAN AREAS (Eastern Ontario and
Western Quebec).

Adams, Barlow, Bell, Burwash, Dawson, G. M., Ells, Ferrier, Low,
Walker, Williams, G. H., Willmott.

THE LAKE SUPERIOR REGION.
Bayley, Berkey, Blue, Boss, Clements, Coleman, Culver, Elftman,
Finlay, Grant, Gresley, Hubbard, Lane, Lawson, Newett, Parks,
Smith, W. H.C., Smyth, H. L., Spurr, Van Hise, Wadsworth, Win-
chell, N. H., Winchell, H. V., Winchell, A.

THE GREAT NORTHERN AREA OF CANADA.
Dawson, G. M., Dowling, Gibson, Low, McConnell, Tyrrell.

EASTERN CANADA AND NEWFOUNDLAND.
Bailey, Bonney, Dawson, G. M., Ells, Low, Matthew, Miller.

CANADA, GENERAL.
Dawson, G. M., Dawson, Sir Wm., Gibson.
THE NEw ENGLAND STATES.
Collie, Dale, Daly, Davis, Emerson, Hitchcock, Hovey, Sears, Whittle.
THE MIDDLE ATLANTIC STATES.
Bascom, Clark, Cushing, Darton, Grimsley, Hollick, Kemp, Keyes,
Lesley, Marsters, Merrill, F. J. H., Merrill, G. P., Nason, Ries, Smyth,
C. H., Westgate, White, Williams, G. H., Wolff.
THE SOUTHERN ATLANTIC STATES.
Clements, Darton, Hawes, Hayes, Keith, Kimball, King, Smith, E. A.
ISOLATED AREAS IN THE MISSISSIPPI VALLEY.
Beyer, Buell, Frazer, Hall, Haworth, Hill, Keyes, Nason, Norton,
Osann, Sardeson, Todd, Weidman, Winslow.
THE CORDILLERAS.
Aguilera, Cross, Dawson, G. M., Eldridge, Emmons, Gilbert, Gris-
wold, Hague, Iddings, Lakes, Lawson, Mills, Peale, Pirsson, Russell,
Sapper, Walcott, Weed.
MEXICO AND CENTRAL AMERICA.
Aguilera, Sapper.
C. K.. Lert.

MADISON, WIS.

REVIEWS

The Upper Silurian fauna of the Rio Trombetas, State of Parad, Brazil.
By Joun M. CrarKke. Archivos do Museu Nacional do Rio de
Janetro, 1897-1899, Vol. X, 1-48. Rio de Janeiro, 1899.

Devonian mollusca of the State of Pard, Brazil. By Joun M.
CLARKE, 7dem 49-174.

These two papers are published in both English and Portuguese and
are accompanied by eight beautifully drawn quarto plates, done by
lithographers accustomed to work of this kind, illustrating all the
species described. |

The collections described are those made in 1876, in the Amazon
valley, by the extinct ‘““Commissio Geologica” or Imperial Geological
Survey of Brazil. When the survey was suspended in 1877 the col-
lections were turned over to the National Museum at Rio de Janeiro,
and through the efforts of Professor O. A. Derby, previously a member
of the survey and later director of the geological section of the National
Museum, these unique collections were placed in the hands of Dr. John
M. Clarke, one of our best American paleontologists. Dr. Clarke had
already described and figured the trilobites of the Ereré and Maecurti
sandstone, his paper appearing in Vol. IX of these same archives.
The papers here mentioned make his second important contribution to
our knowledge of the paleontology of the Amazon valley, and the most
valuable since the publication of Dr. C. A. White’s great work upon
the Cretaceous fossils of Brazil.

At the end of the second paper he gives a list of the Devonian
species of the Lower Amazon region, and finds the Ereré fauna to be
“a miniature of the Hamilton”’ of New York (p. 158). The Curua
fauna he considers a member or modification of the Maecurti group.
The rocks from which these fossils come are exceedingly rich, one
locality, Ereré, furnishing forty-eight species, and, another, Maecurut,
seventy-eight species.

In his summary concerning the Silurian fossils Dr. Clarke says that
“the lower and upper Silurian elements of this little fauna are pretty
equally commingled, and the inference is quite natural that in this

813

814 REVIEWS

region the break in the record represented by the conventional plane
of separation between the upper and lower divisions of the series is
here obliterated. . . . . The little fauna is the oldest yet-described
from Brazil.”

That last remark reminds me that some three years ago I published
in this journal (Vol. IV, p. 975) a notice of an article by Dr. F. Katzer
upon “ The oldest fossiliferous beds of the Amazon region.” In that
article Dr. Katzer claims to have found graptolites in rocks said to
have come from the Rio Maecurti region. Since the appearance of
that note my attention has been directed to the fact that the article in
question contained neither names, descriptions, nor figures of such
graptolites, and that the origin of the fossils he mentioned was not
really known—omissions that I should have observed without assistance.

It is a matter of painful interest to observe the great gaps of time
between the collecting of the fossils by the Geological Commission,
the date of Dr. Clarke’s papers, and the date on the title page of this
belated volume of excellent work.

We are accustomed in this country to hear more or less complaint
about delay in the publication of government reports. But in this
instance we may see if we will how much worse such matters might be.
These collections were made in 1876, were placed in Dr. Clarke’s
hands in 18(?), the paper on the Silurian fossils was finished by him
in 1891, that upon the Devonian in 1892, and the publication appears
toward the end of 1899 —twenty-three years after the field-work !

The inconvenience of this sort of thing is perhaps not as serious
in Brazil where comparatively little is doing in science as it might be
here or in Europe, but, like all other wrongs, sooner or later the country
must pay for them. J. C. BRANNER.

The Cretaceous of the Black Fills as Indicated by the Fossil Plants.
By Lester F. Warp, with the Collaboration of Walter P.
Jenney, William M. Fontaine, and F. H. Knowlton. Extract
from the Nineteenth Annual Report of the U. S. Geol. Sur-
vey, Part II. Washington, D. C., 1899.

The results recorded in this extract are the outgrowth of a series
of investigations beginning with the discovery of cycads in the Black
Hills in 1893. From a study of these fossils and of their stratigraph-
ical position, Professor Ward reached the conclusion that a part of the

REVIEWS 815

so-called Dakota formation of the Black Hills belongs to the Lower
Cretaceous series. This conclusion, together with the observations
which led up to it, he published in the JouRNAL oF GEOLOGy in the fol-
lowing year. Since that time the work of investigation has been
greatly extended through the efforts of Professor Ward and_ his
co-laborers, with the result that his former conclusion is now fully
substantiated.

New fossil localities were found, and many new species were col-
lected. Of the cycads, one hundred and twenty-six trunks and frag-
ments were examined. These were collected from two general although
widely separated areas. The collection contains twenty-one species,
all of which are new to science. Fossil forests are mentioned as occur-
ring at the same horizon.

Professor Jenney makes a report on the Hay Creek region, in which
he finds: a marine Jura characterized by an abundant invertebrate
fauna; a later Jura resting unconformably upon the former, and char-
acterized by saurian bones and fossil wood ; above this the Lower Creta-
ceous, which he subdivides as follows: (1) the Hay Creek formation ;
(2) the Barrett shales ; (3) the Oak Creek beds. ‘The series is charac-
terized by an abundant flora which contains no cycads.

The flora of the region is described by Professor Fontaine, who
finds a number of species common to the Potomac formation, and a
few common to the Kootenai. This suggests a closer relation with the
eastern flora, but Mr. Ward thinks that this may not be the actual con-
dition, as the Kootenai flora has not been as thoroughly investigated
as the Potomac.

A few outcrops of the ‘‘Atlantasaurus beds ”’ are reported as occur-
ring on the eastern flank of the Black Hills. These consist of clays rep-
resenting a thickness of about fifty feet and containing bones of
saurians. The beds are thought to have been laid down in the depres-
sions of the eroded surface of the marine Jura. W. N. Locan.

The Geology and Physical Geography of Jamaica: Study of a Type of
Antillean Development. By Rosert T. Hix. Bulletin of
the Museum of Comparative Zodlogy at Harvard College,
Vol XX X1V5 1800. .pp.256,.41 plates.

The general scope of this volume, which is an important addition
to the work which the author has heretofore done on Antillean geology,

816 REVIEWS

is indicated by the title of the several parts of the volume. ‘These are
as follows: Part I, Geography and Physiography; Part II, The
Geologic Structure and Sequence; Part III, Paleontology of the
Jamaican Sequence; Part IV, Relations of the Jamaican Formations
to those of Adjacent Regions; Part VI, Changes of Physiography in
Tropical America bearing upon the History of the West Indian Islands;
Part VII, Appendices (1) Additional Note on the Geology of Porto Rico
and Santiago de Cuba, and (2) Some Cretaceous and Eocene Corals
of Jamaica (by T. Wayland Vaughan).

Geography.— Geographically the island is described as follows:
There is a central mountain axis in the eastern third of the island, the
highest point of which is between 7000 and 8000 feet above sea level.
About this mountain axis, with its chief extension to the west, is a
plateau ranging from 1000 or 1200 feet, to 3000 feet. The plateau is
really a gentle arch, and its greatest elevation is in the central part of
the island. The plateau terminates abruptly by steep slopes known as
the “‘back coast border.” The margins of the back coast border are
irregular, the result of valley excavation. The plateau is chiefly of
limestone, and its interior topography is largely the result of solution
and interior drainage. The plateau contains many remarkable basins
developed in this way. Some of them have no outlets, while others
have recently been tapped by valleys working in from the margins of
the plateau. The margins of the plateau are extensively terraced. On
the east side of Montego Bay there are at least six terraces, and while
the number elsewhere is fewer, some of them are at levels considerably
above those shown at Montego Bay, so that the total number is more
than six. ‘The terraces are much interrupted by erosion, the oldest being
least distinct, and most discontinuous. The highest occurs at elevations
of 1800 or 2000 feet, an altitude quite above the top of the back coast
border in some parts of the island. The second highest terrace occurs
at an elevation of about 1500 feet, the next at 1000 feet, and others at
650, 300, and 200 feet respectively. The upper terraces appear to have
been carved out of the limestone during the period of emergence which
followed the deposition of the limestone. Those below 700 feet appear
to have been carved in a later period of elevation, following a period
of submergence, after the higher terraces were made. The terraces
“have all been cut out of the land by gradational processes (base level-
ing and marine erosion) and represent pausation stages in two long
periods of elevation” (p. 33).

REVIEWS 817

If the back coast border of the plateau were continued seaward, the
borders of the island would lie much beyond the present shore line,
and from this and other phenomena it is inferred that the former exten-
sion of the island was considerably greater than the present. There
are terraces on the submerged slopes of the island similar to those
above the water, which are in harmony with this view.

Bordering the plateau below the back coast border there is a coastal
plain which is nearly continuous. In some places it is narrow, and in
others it reaches far back into the island. The coastal plain is made
up of three sorts of formations, elevated reefs, sea margin débris, and
land alluvium. The coastal plain is more or less terraced by old wave-
cut terraces, which have since been submerged and are now veneered
with later deposits. The highest is about 150 feet above sea level.
Filevated=: reets: occur, at three. levels, (60,;. 25, and 15 feet or less;
respectively, above sea level.

The streams of the island belong to two types: (1) the autogenous
type, with the peculiarities which go with changes of level; and (2) the
interior streams which drain into limestone sinks. In addition to these
two types, there is a combination type which results from the
capture of the interior drainage by streams which flow seaward.

A topographic map with 250-foot contours and a geologic map
accompany the volume, and help to make the geography and geology
clear.

Geology.— The central mountain axis of the island is made up of
rocks known as the Blue Mountain series. This series is made up
chiefly of ‘‘loose or slightly indurated beds of gravel, clay, bowlders,
and tuffs, with exceptional beds or bosses of hard indurated limestones
and yellow clay. The rocks are usually of dark color . . . . in strong
contrast to the glaringly light colors which characterize the succeeding
formations of the oceanic and coastal series. ‘The material, with the
exception of occasional limestone beds and a few outcrops of clay
marls, can be traced to igneous rocks; it was first volcanic ejecta and
subsequently and successively underwent various degrees of attrition
and sedimentation 72.0. . (pita).

This Blue Mountain series constitutes the surface formation of all
parts of the island which rise above 3000 feet. From exposures at
lower levels where erosion has removed the overlying strata, it is known
that the same series has extensive development beneath the younger
formations, and from the known exposures the series is believed to

818 REVIEWS

underlie most of the island. The beds of the Blue Mountain series
are much deformed. Since a continuous exposure of the total series
is nowhere found, exact measures of thickness have not been
obtained, but it is stated that the thickness probably exceeds 5000
feet:

The Blue Mountain series is made up of Upper Cretaceous and
Lower Eocene beds. ‘There seems at this point to be a little confusion
in the classification, since the Richmond formation, which appears to
be the upper part of the Blue Mountain series, is classed as Eocene at
some points (geological map), but as Upper Cretaceous at others (p.
143). The Blue Mountain series is exposed in the central and western
parts of the island at levels which are below the mountains of the east.
In these localities, erosion has removed the overlying beds.

The Blue Mountain series is overlaid by the Cambridge formation,
a formation not extensively exposed. Where it appears, it skirts the
older series. It is made up of clays, marls, and yellow limestones,
and occupies a transitional position between the older series, the
material of which was derived from land formations, and the next
succeeding formation, the material of which is limestone, and therefore
of oceanic origin. The Cambridge formation is classified as late
Eocene.

The Cambridge formation is followed in stratigraphic order by an
extensive formation of White Limestone, the principal formation of the
plateau. It has by far the widest surface development of any forma-
tion on the island. It covers the whole of the island between the top
of the plateau (3000 feet) and the coastal plain, and underlies some
portions of the latter. In the western part of the island it completely
covers (or once did) the Blue Mountain series. The beds of limestone
are often considerably disturbed. The formation is assigned a deep
water origin, since it contains neither reef corals nor littoral shells.
Its fossils are mainly microscopic, and it is referred to the earlier part
of the Oligocene period.

The formations of the island younger than the White Limestone
belong to the coastal series, and were made after great changes had
affected the island. ‘These coastal formations are made up of four
sorts of rock: (1) marine beds, (2) alluvium, (3) elevated coral reefs,
and (4) littoral deposits.

The oldest of these formations is known as the Bowden formation,
the age of which seems to be in some doubt. It is regarded as either

REVIEWS 819

late Oligocene or Miocene. ‘The formation was deposited after a sub-
sidence which followed the uplift and extensive erosion of the White
Limestone. The break between it and the White Limestone is, there-
fore, a great one, and on general grounds it would seem more in
accord with modern classification to make the break between these two
formations the division between the Oligocene and Miocene than to
place it in the Oligocene. The Bowden formation has a thickness of
something like 250 feet. Its outcrop consists of a fringe around the
older plateau region, and it is, in turn, bordered by still later and
lower-lying formations. ‘The Bowden formation is made up of various
sorts of sedimentary rock.

The next succeeding formations are classed as Pliocene. They are
composed of marl and limestone of marine origin (Manchioneal), and
of slight thickness, and of gravels from the uplands. The gravels are
in part estuarine, in part subaérial, and in part littoral. ‘The Pliocene
formations have relatively slight surface development, though consider-
able areas in the vicinity of Kingston are covered by them.

Among the Pleistocene formations are beds of reef rock, ten to
forty feet in thickness. They range in elevation from sea level up to
seventy feet. ‘They lie on eroded land surfaces, and their relations
are significant of the movements to which the land had been subject
before their formation. Other Pleistocene formations consist of chalky
marls at low levels near the coast. Here belongs especially the Fal-
mouth formation which rarely occurs higher than fifteen feet above the
sea. ‘The Falmouth formation is nothing more than a series of uncon-
solidated sea muds, probably synchronous with the younger elevated
coral reefs. Among the latest formations are the alluvial deposits in
valleys about the shores. In Montego Bay there are low islands which
owe their origin primarily to mangroves.

There are some igneous rocks on the island. The oldest are the
bowlders of andesite in the Blue Mountain series. The source of this
igneous matter is unknown. There are mid-Tertiary igneous rocks in
the form of dikes, laccoliths, etc., composed of hornblende-diorite, and
granite-porphyry. These intrusive rocks affect the Blue Mountain
series, and extend upward into the White Limestone above, but
are found only in the eastern third of the island. In a single locality
on the north coast near the east end of the island there is eruptive
amygdaloidal basalt. There is everywhere more or less metamorphism
in association with the igneous rocks.

820 REVIEWS

The topography and stratigraphy of the island suggest the follow-
ing sequence of events :

1. The first event in the history of the island so far as now known
is the igneous activity which furnished the material for the Blue
Mountain series. This was probably in Cretaceous time. The oldest
formation of the island is composed of the débris of this activity. The
amount of the débris was great, indicating that the volcanic activity
was extensive.

2. The degradation of the volcanic débris and the re-deposition of
the material in the form of sedimentary formations (the Blue Mountain
series) was the second great event in the history of the island. The
formation is such as to show (a) that there was rapid erosion and
deposition ; (4) that the land from which the sediments came was
high ; and (c) that the deposition was accomplished in shallow water.

3. The next event was the elevation, and, perhaps, the folding, of
the beds of the Blue Mountain series. The folding probably followed
the deposition of the Richmond (Eocene) formation; that is, was mid-
Eocene. On this point, however, the author is not altogether satisfied,
and indicates that the folding may possibly have occurred later.

4. The next event was the sinking of the island, probably late in
the Eocene period, followed by the deposition on the submerged surface
of the great White Limestone formation. The subsidence is estimated
to have been at least 1200 fathoms. This great subsidence submerged
all but the higher parts of the Blue Mountain series, leaving at most
only the parts which are now more than 3000 feet high out of water.
The subsidence may have been even greater, submerging the whole
island. The evidence of this great subsidence is found in the Mont-
pelier chalk (the lower part of the White Limestone), the composition
of which indicates, according to Mr. Hill, a depth of 1200 to 2300
fathoms. Further evidence of the great subsidence is found in the
stratigraphically equivalent radiolarian earths in eastern Cuba—earths
which call for depths of 3000 to 4ooo fathoms. Mr. Hill thinks it
would not be unfair to assume 10,000 feet as the mean subsidence of
Jamaica (p. 165). The argument of Mr. Hill for so great a sinking
does not seem altogether conclusive. If the whole of the island were
submerged, and this would not seem to call for so great a subsidence
(though still a great one) there is no apparent reason why formations
due to pelagic life should not be made in shallow water, even though
too deep for corals and other shore-life. A few hundred feet of water

REVIEWS 821

would destroy these shallow water forms, and since there would be no
source for terrigenous material, the shells of pelagic life should have
been the chief source of sediment. The problem is the same as that
presented by the Niobrara chalk of the United States. It shows
absence of terrigenous sediment rather than great depth of water.

5. The next event in the history of Jamaica was the re-elevation of
the island in the Oligocene period. The amount of elevation is esti-
mated at 13,000 feet. If the preceding subsidence were less than stated
above, the call for so great a rise would disappear. After this re-eleva-
tion, the island is believed to have had a much larger area than now.
The uplift was accompanied by a gentle folding of the rock, the
folding having an east-west axis, and therefore making an angle with
the axes of the older mountains, the trend of. which is northwest and
southeast. With the general arching of this time there were many
minor folds. It is believed to have been in connection with this ele-
vation that the igneous intrusions of mid-Tertiary time were effected,
and the higher terraces on the margins of the plateau developed.

6. The next event was another subsidence, contracting the island to
the back coast border. The depression is placed at about 3000 feet. It
was at this time (as well as during the preceding interval of emergence)
that the back coast border of the plateau was developed. During this
minor submergence the Bowden formation (Miocene), reaching up to
levels of 300 feet, was deposited.

7. This subsidence was followed by an elevation. The Blue
Mountain ridges and the plateau were elevated some 500 feet. ‘The
borders must have been elevated much more, for the southern coast is
believed to have been extended out to about the present 500-fathom
line. This movement of elevation was less orogenic in its character
than any of the preceding, and was followed by a period of erosion.
During the pre-Bowden epoch of erosion the streams did not get their
heads far back into the plateau, but developed great amphitheaters
near the edge of the back coast border, while great basins were being
developed in the interior. During the post-Bowden interval of erosion,
the coast streams worked back, and drained out many of these interior
basins. It was during this elevation that the middle terraces, of the
back coast border—those at elevations of 200 to 700 feet—were
developed.

8. The next event was probably a late Pliocene subsidence of not
more than 700 feet. This submerged the border of the island to the

822 REVIEWS

base of the back coast border, covering the present low borders with
littoral and estuarine formations.

g. The next and last event was an epeirogenic movement of upward
phase, amounting to about 800 feet, which raised the submerged bor-
ders into the present coastal plain. This upward movement may have
been interrupted by a minor subsidence, in early Pleistocene times.

There were, therefore, according to this interpretation four distinct
periods of subsidence after the deposition of the Blue Mountian series.
(a) The subsidence which preceded the deposition of the Montpelier
(Oligocene) formation ; (4) the subsidence which preceded the deposi-
tion of the Bowden (Miocene) formation; (c) the subsidence which
prepared the way for the Manchioneal (Pliocene) formation, and (d) the
subsidence which resulted in the deposition of the Pleistocene marine
formations within the present land area. These four subsidences alter-
nated with corresponding elevations: the first in the mid-Oligocene
period, elevating the White Limestone; the second in the late Miocene,
lifting the Bowden formation; the third in the early Pleistocene,
bringing up the Pliocene formation ; and the latest, exposing the marine
Pleistocene. This series of uplifts and depressions constituted a dimin-
ishing series, being in this respect in consonance with other Antillean
and with mid-American phenomena. The post-Richmond (early
Eocene), the post-Moneague (mid-Oligocene, White Limestone), and
post-Bowden (Miocene) uplifts were orogenic, diminishing, however,
in their orogenicity.

In that part of the volume which deals with the relations of the
Jamaican formations to those of adjacent regions, the author announces
the general conclusion that the Jamaican sequence is very like that of
the other islands of the Great Antilles.

In his summary of the history of the Antillean region the follow-
ing generalizations are given:

1. The geology and configuration present no evidence whatsoever
whereby past land connections can be established between these islands and
the North and South American lands in Post-Jurassic time, especially in the
Tertiary, Pleistocene, or recent epochs.

2. The configuration and condition of these islands in pre-Jurassic time
cannot even be surmised.

3. There are some hypothetical and biologic reasons for believing that
the outer rim of the American Mediterranean constituted a partial or com-
plete bridge between the continents in Jurassic time, and that the Panama
bridge did not then exist.

REVIEWS 823

4. The first definite evidence of Antillean lands is found in the eruptive
rocks of late Cretaceous time, when it is probable that there were marine
volcanoes.

5. The land débris constituting the Eocene strata throughout the islands
testifies the pre-existence of extensive Cretaceous land areas.

6. There was a profound regional subsidence in late Eocene and early
Oligocene time, which submerged all but the highest tips of the Antilles, and
which extended to the margins of the surrounding continents.

7. In late Oligocene or Miocene time there was a tremendous oroganic
movement which resulted in uplift, whereby many of the islands were con-
nected with each other, and possibly an insular southern portion of Florida,
but not establishing land connection with the North and South American
continents.

8. In Miocene or early Pliocene time the islands were severed by sub-
mergence into their present outlines and membership, which they have since
retained with only secondary modification.

g. In Pliocene and Pleistocene time there have been intermittent periods
of elevation without serious deformation, but not sufficient to establish land
connections or to restore the islands to the heights and areas of mid-Tertiary
time. The Pleistocene movements, while epeirogenic, were sufficiently dif-
ferential to show that they were not uniform in all parts of the area, showing
great differences in amplitude within the West Indian area, and were not
harmonious with those of the North American coastal plain.

10. The irregularities of the submerged configuration of the West Indian
region are orogenic, and not due to submerged continental drainage systems.

11. The elevated coral reefs of the West Indies were formed on rising
lands.

In appendices Mr. Hill gives an additional note on the Geology
of Porto Rico and Santiago de Cuba, and Mr. T. Wayland Vaughan
describes some Cretaceous and Eocene corals from Jamaica. The note
on the geology of Porto Rico and Santiago de Cuba, based on a
recent geological reconnoissance, is as follows:

1. An older plexus of water-sorted hornblendic volcanic material— tuffs
and conglomerates with interbedded Cretaceous Rudistean limestone similar
to that of Jamaica, composing the central mountains.

2. An Eocene system of impure lignitic sands and clays like the Rich-
mond beds, occurring on the western side of the island near San Sebastian.

3. Fossiliferous marl beds overlapping the above, which at this writing
have not been determined.

4. Miocene coral limestone, unlike anything hitherto recorded from the
Great Antilles, but of the type occurring in Antigua. These constitute the
hilly country north and northwest of Lares.

824 REVIEWS

5. White limestones of probable Pliocene age, composing the hills of the
south coast.

6. Elevated reefs, but feebly represented.

7. Alluvial plains of Pleistocene age. The terrace phenomena are less
developed upon this island than in any of the other Great Antilles, although
the Pleistocene base leveling is well developed in stream valley phenomena.
Dikes of syenitic-like porphyry, probably diorites, were also noted cutting
the older hornblendic rocks.

Evidence was obtained indicating that the great mountain movement
culminated before the Miocene, and that there has been at least one thousand
feet of vertical uplift since that epoch.

The recent work in Cuba consists of a section across the Sierra
Maestra from the coast to the Rio Cauto. In making the section, Mr.
Hill was convinced ‘‘that the crystalline rocks of that region are Cre-
taceous and post-Eocene Tertiary, and not Paleozoic, as asserted by

”?
.

Frazer. .
IR. ID; Ss

Le Stillstandslagen des letzten Inlandeises und die hydrographische
Entwickelung des pommerschen Kiistengebtetes. By Dr. K.
KEILHACK. Separatabdruck aus dem Jahrbuch der konigl.
preuss. geologischen Landesanstalt ftir 1898. Berlin. Pp.
gO-152, 14 plates.

The immediate object of this paper is to set forth the relations
between the edge of the ice and the drainage of north Germany dur-
ing the last glacial epoch. The general slope of south Germany is north-
ward, and the general slope of the ice which lay over north Germany
was southward. Along the meeting of these opposing slopes, water
courses were developed while the ice was in existence. Locally these
marginal water courses were lakes, but often there was a river current
along them. Many of the peculiarities of topography and drainage
date from the time of ice occupancy.

Incidentally, several points of general interest are developed. Dr.
Keilhack recognizes three distinct glacial epochs. During the last he
recognizes five more or less distinct stages of the ice, one standing for
the maximum advance of this epoch, and the others recessional stages.
Each of these stages had its marginal water course.

During its maximum stage the limit of the ice in this epoch was just
north of the Malapane and Oder rivers, as far west as the northward

° REVIEWS 825

bend of the latter, southeast of Glogau. From this point west the
edge of the ice was south of the Oder, having a general west-
northwest course to Magdeburg. West of Magdeburg the position of
the edge of the ice has not been determined. It was perhaps along the
Aller River, and perhaps farther north along the divide between this
river and the Elbe. During this stage of the ice marginal drainage
was westward along the valley of the Malapane to the junction of that
stream with the Oder at Oppeln, thence down the Oder to Breslau and
beyond. Here the drainage left the present course of the Oder
(which beyond this point was buried by the ice) and flowed west-
northwest to the valley of the schwarze Elster, thence along that
valley to the Elbe, and down the Elbe to its junction with the
Saale.

The halting places of the ice during its retreat are recognized by
three principal criteria. First, the exd@mordne, which are bowlder walls
(as that term is used by the Germans); second, the great ridge-belts of
markedly undulatory topography regarded as terminal moraines in the
United States; and third, the sand and gravel plains outside the ridges
just referred to. All these criteria are found in connection with the
edge of the ice at its various stages, but in better development in some
cases than in others.

The edge of the ice during the first recognized halt in its retreat
lay afew miles farther north, running in the same general direction.
Roughly, it extended from Pleschen to Potsdam, and thence to a
point near Lauenburg just north of the Elbe. West of Lauenburg the
border has not been traced. The margin of the ice during this halt
was more or less lobate. The marginal drainage was along the Bartsch-
Baruth Valley to the Elbe north of Magdeburg. Farther west the
course of the drainage is uncertain.

The second halt of the ice, marking the third position of a more or
less stationary edge, lies still farther north, along the divide between
the Warthe and the Netze from longitude 36° E. to Frankfurt on the
Oder. Here the edge of the ice crossed the present course of the
Oder, and extended westward and northwestward to Schwerin and
beyond. During this stage the marginal drainage was westward along
the course of the Warthe to the longitude of Posen, thence westward
to the Oder and down the latter nearly to Frankfurt, thence westward
by way of the Spree to Berlin, and thence west-northwest to the Elbe,
and thence to the North Sea.

826 REVIEWS

The third halt in the ice front shows that the recession was very
unequal in different regions. In the eastern part of Germany the edge
of the ice at this stage was far north of its position during the preced-
ing stage, while in west Germany the differences in position were
slight. Generally speaking, the border of the ice between the Weichse]l
and the Oder, lay along the divide between the Netze on the south,
and the drainage which flows directly to the Baltic on the north. It
crossed the Oder near Oderberg ; thence it ran in a general northwest
direction to Litbeck. From Ltibeck it extended north-northwest
through Jutland. During this halt the edge of the ice had two or
possibly three great lobes. The greatest of these lay between Danzig.
on the east and Liibeck on the west. East of Danzig there was another
lobe extending well southward, the eastern limit of which is not
mapped. West of Liibeck the Jutland ice may be regarded as con-
stituting a third lobe. Beside these great lobes, there were many
minor crenations of the edge. This stationary position of the ice is the
best known of all, partly because it has been more studied, and partly
because it is far more distinct. All the criteria of the stationary edge
find here their best development. The morainic (as that term is used
in America) belt of this stage is the Baltic Hohenriicken. It is this
belt which the reviewer traced out in a rough way in 1887, and char-
acterized as the great terminal moraine of north Germany.’ Dr. Keil-
hack says that this moraine is bordered throughout 650 of the 700
kilometers of its length in Germany by sand plains. The morainic
topography of this belt is much more strongly developed than that of
the other halting places, as also the Hxdmordne. To Dr. Keilhack’s
conclusion that the ice along the fourteenth part of this 700 kilometers
where sand plants are absent, disappeared chiefly by evaporation
instead of by melting, we can hardly subscribe.

During this stage of the ice the marginal drainage was along the
Thorn-Eberswalde Valley which connects with the Elbe southeast of
Wittenberge. Along this course the water was partly fluviatile and
partly lacustrine.

The fourth and last chief halting place recognized is near the
Baltic. In receding to this position from the last the ice retreated
most over the lowest ground, and least over the highest. A new mar-
ginal drainage line was formed not far from the coast, and roughly

Terminal Moraines in North Germany, Am. Jour. Sci., Vol. XXXV, Series 3,
pp. 401.

REVIEWS 827

parallel to it from Danzig to Stettin, and thence vza the Trebel to the
Baltic near Ribnitz. Some parts of this marginal water course were
fluviatile and some lacustrine, the largest lake being about Stettin.
These lakes are described in detail. For the largest three distinct
levels are made out, the highest of which is 25 meters above sea level.
These stages are connected with the retreat of the ice, and the open-
ing of new outlets. The development of the present Baltic drainage
is described in great detail. Many of the north-south valley now
draining to the Baltic are thought to have been originally subglacial
valleys draining south to the marginal valley last mentioned before
the ice melted away. The drainage through them was then reversed.

Between the fourth halting place of the ice and the Baltic Sea
Keilhack makes out and maps eleven substages in the recession of the
ice, each changing in some recognizable way, the drainage of the pre-
ceding stage. These subordinate stages, like the larger ones, show
that the ice did not retreat at the same rate all along its front. So
detailed a piece of work concerning drainage along the margin of the
ice has not before been published.

One of the interesting facts brought out in this paper is the simi-
larity of the phenomena of the last glacial epoch in Germany with
those of the corresponding epoch in the United States. In the Wis-
consin epoch the edge of the ice made several halts in its recession
from its position of maximum advance. In each of these positions
morainic belts were developed, and as in Germany the strongest of
these belts was not at the position of maximum advance, but in a more
northerly position. As in Germany, each morainic belt is bordered by
sand plains. As in Germany, the recession of the edge was unequal,
and here as there, the lobations of one stage did not correspond with
those of another. The analogies might be carried much further, but
not to the drainage from the ice, since similar topographic relations
did not exist in the United States.

Reb:

Shore Line Topography. By ¥F. P. Guiiiver.. Proc. Am. Acad.
of Arts and Sciences, Jan. 1899. pp. 151-258.

In this essay Mr. Gulliver presents the mature results of a very
serious piece of work. The topography of shore lines is considered
under zzztzal forms and seguential forms. Under initial forms are

828 REVIEWS

included those which shore action has not modified since the region
concerned was uplifted or depressed (relative to the surface of the sea).
Under sequential forms are included those features which are devel-
oped subsequent to the diastrophic change, by the forces at work
along the shore. The larger part of the essay is naturally devoted to
sequential forms.

The reading of this essay makes several things evident. In the
first place, Mr. Gulliver has exhausted the literature on the subject
with which he deals; and, in the second place, he has made diligent
use of maps. In the use of this material he has gathered a large body
of facts which he has attempted to interpret and classify. Not only
this, but he has attempted to interpret and classify them zx ¢erms of
development, so as to put the topography of shore lines on an equal
footing with the topography of land surfaces, as an.index of geo-
graphic evolution. So far aS we are vaware, this is the first-time
this task has been essayed, and the author is to be congratulated on
the successful outcome of his study. Geography and geology are the
gainers, and the future student of coast lines will hardly fail to consult
this essay.

In the author’s own words, the thesis of the essay is the following:
“The forms of any coastal belt may be grouped in the appropriate
stages of a cycle. These forms will be consistently related to the
associated land area on the one hand, and to the sea bottom on the
other. When considered together, the forms of a coastal belt indicate
the relative time since the last considerable uplift or depression, as
well as the ratio existing between the several activities, in their
dynamic effect upon the forms of the coast and the shore.” The
whole essay is the expansion of this idea.

In consonance with this mode of treatment of the subject, the
author has made use of many of the life terms, such as infancy, youth,
adolescence, maturity, etc., which are now in use in connection with
the history of rivers. Some of these terms have a new meaning when
applied to coast lines, and their adoption will be at the cost of some
mental effort. At the outset it will be necessary to stop to think what
the terms mean in connection with coast lines, as distinct from what
they mean when applied to land surfaces in general. This, however,
is no serious objection to their use. On the first reading of the essay,
it must be confessed that the use of biological terms sometimes seems
a little forced. Such objections as may be entered to their use will be

REVIEWS 829

charged to old-fogyism by those who like to see the old terms used in
the new way, and to conservatism by others. The reviewer is pre-
pared to go a good ways in the application of biological terms to geo-
graphic evolution, where the terms fit, but when a large and quickly
built delta is called a “precocious infant” (p. 224), it seems to be
going a trifle far. Such criticism is, however, on the surface of things ;
it touches nothing fundamental. Some new terms are introduced to
designate forms which have been nameless, and some of them are so
good and so much needed that they should be adopted at once. An
example is ‘‘wave-base”’ (p. 176) to denote the plane to which waves
may degrade the bottom in shallow water. It is the correlative of
base level. Some other terms, however, do not at first seem so neces-
sary or so happily chosen. To this class belongs ‘winged beheadland”’
to denote a sea cliff with a spit on either side (p. 213).

There are not a few minor points in the essay which might be
criticised, but it seems almost ungracious to mention them in the
presence of so many larger matters which deserve hearty commenda-
tion. Glacial erosion seems not to have due recognition among the
agencies which shape shore lines. It is true that the author expressly
disclaims his intention of discussing this point, and it is true that
glacial modification of coasts are accidental, in the sense of not being
a part of the normal cycle which is the theme under discussion, but it
might have been well to recognize more fully the effects of glaciation
in connection with some of the coasts referred to, even though the
subject of glacial modification of coast lines is not discussed. The
writers on Lake Agassiz are gently criticised for describing the shore
lines of that lake as if they ‘‘were formed once for all and would
forever remain as constructed” (p. 187), but the truth is, these shore
lines are still sensibly as constructed, and no one has essayed to write
up the history of the changes which these shores will yet undergo. It
will be readily seen that when such minor points are the things which
suggest themselves for criticism the essay as a whole is strong.

Not only is the essay a serious piece of work, as suggested at the
outset, but, by means of the numerous references, both cartographic
and textual, the author has placed the material on which he based his
conclusions at the command of future students. From this material
students may draw their own conclusions, and, judging from the tone
of the essay, no one would be more ready to entertain alternative
conclusions than Mr. Gulliver himself. Rebs.

INDEX TO 1OLUNie WV LT.

Adams, F. D. Report on the Geology and Natural Resources of the Area
included by the Nipissing and Temiscaming Map Sheets, comprising
Portions of the District of Nipissing, Ontario, and of the County of
Pontiac, Quebec. A. E. Barlow. (Review) - - - - -
Sir William Dawson - . - - - . : - -
Analcite Rock from Lake Superior, A New. A. P. Coleman - - - -
American Cements, Uriah Cummings. Review by H. F. Bain = - -
American Homotaxial Equivalents of the Original Permian. C.R. Keyes — -
American Museum of Natural History, Bulletin of the, Vol. X. Review by W.
ACs Ilys. - - - - - - - - - - -
Application of Photography to the Determination of Earth Movements. Edi-
tories PCa: . - - - - - - - - -
Arrhenius, Svante. The Influence of the Carbonic Acid of the Air upon the
Temperature of the Ground. Review by C. F. Tolman - - -
Artesian Well System of Georgia, Geological Survey of Georgia, Preliminary
Report on the, S. W. McCallie. Review by T. C.C. - - -
Ashley, George H., Department of Geology and Natural Resources of Indiana,
XXIII Annual Report. Review by A. H. Purdue” - - - -
Aspen District, Colorado, Geology of the, J. E. Spurr and S. F. Emmons.
Review by W. T. Lee - - - - - - - - -
Atmospheric Basis, An Attempt to Frame a Working Hypothesis of the Cause

of Glacial Periods on an. T.C. Chamberlin - - - 545, 667,

Atmosphere, The Carbon Dioxide of, and its Relation to the Carbon Dioxide
of the Ocean. C. F. Tolman, Jr. - - = 2 : cs e

Bain, H. F.— Editorials: Missouri Geological Survey - - - - -

Do State Surveys Pay ? - - - . - . . - -

Reviews: American Cements. Uriah Cummings - - - - -

Tron Making in Alabama, 1899. W. B. Phillips - - - - -

Special Report on Gypsum and Ls Cement Plasters. G. P. Grims-

ley and E.H.S. Bailey - - - - - - -

Bailey, E.H.5S. Special Report on ee and Gypsum Cement Piece
G. P. Grimsley and. Review by H. F. Bain - - -

Barlow, A. E. Report on the Natural Resources of the ee included by the

Nipissing and Temiscaming Map Sheets, comprising Portions of the

District of Nipissing, Ontario, and of the County of Pontiac, Quebec,

Review by F. D. Adams - - - - - - - - 5

Beach Cusps. Mark S.W. Jefferson — - - - - - - - -

720

751

701

213

713
237

832 INDEX TO VOLUME VII

PAGE
Black Hills, The Cretaceous of, as Indicated by the Fossil Plants, Lester F.
Ward, Walter P. Jenney, William M. Fontaine F. H. Knowlton.
/ Review by W.N. Logan - - - - - - - Sid
Blake, William P. The Pliocene of Skull of California and the Flint Imple-
ments of Table Mountain - . - - - - - = Ogi
Branner, J. C.— Editorial : Commissaéo Geographica e Geologica, Brazil Sy KeXe)
Reviews: Devonian Mollusca of the State of Parad, Brazil. John M.
Clarke - - - - - - - - - - - Ss eye
The Upper Silurian Fauna of the Rio Trombetas, State of Para, Brazil
John M. Clarke - - - - - - - - - - 813
Brazil, Commissdo Geographica e Geologica. Editorial by J. C. Branner a Ghsie)
Brazil, Devonian Mollusca of the State of Para, John M. Clarke. _ Review by
J. Co Branner. = - - - - - - - - - - 813
Brazil, The Upper Silurian Funa of the Rio Trombetas, State of Para, John M.
Clarke, Review by J.C. Branner - - - - - - - 813
Buckley, E.R. Maryland Geological Survey, II, G. P. Merrill and E. P.
Mathews. Review - - - - - - - - - - 207
Butte, Montana, and Vicinity, Granite Rocks of. Walter Harvey Weed -
California and the Flint Implements of Table Mountain, The Pliocene Skull
of. William P. Blake’ - - - - - - - - 1) Oi
Carbon Dioxide of the Ocean and its Relation to the Carbon Dioxide of the
Atmosphere, The. C. F. Tolman, Jr. - - - - - - 585
Carbonic Acid in the Air, Influence of the, upon the Temperature of the
Ground, Svante Arrhenius. Review by C. F. Tolman - - O23
Carboniferous Rocks of Nebraska with those of Kansas, Correlation of. C.S.
Prosser - - - - - - - - ui Bal
Case, E. C. The Development and el Relations of the Vertebrates - 163
Cement Plasters, Gypsum, Special Report on Gypsum and. G. P. Grimsley
and E. H.S. Bailey. Review by H. F. Bain - - - - - 625
Central Connecticut, A Granite-Gneiss in. Lewis G. Westgate - - - 638
Chamberlin, T. C. An Attempt to Frame a Working Hypothesis of the Cause
of Glacial Periods on an Atmospheric Basis - - - 545, 667, 751
Editorials: ‘Constitution of Gaseous Celestial Bodies.” - - - - 92
Doctrine of Crustal Quiescence and Readjustment - - - 295
Application of Photography to the Determination of Earth Movements 295
Reform in Scientific Nomenclature - - - - - - - 509
Reviews: Geological Survey of Georgia, Preliminary Report on the
Artesian Well System of Georgia. S.W.McCallie — - - - S22
Kansas Academy of Science, Vol. XVI - - - - - - 516
Clarke, John M. Devonian Mollusca of the State of Para, Brazil. Review by
J.C. Branner - - - - - - - - = Og)
The Upper Silurian of the Rio Trombetas, State of Para, Brazil.
Review by J. C. Branner - - - - - - - Br (8310123
—James Hall. The Paleozoic Sponges Constituting the Familiy Dictyo-
spongidae. Review by S. W. - - - - - - - i) | Fit)

INDEX OVCLUNE VAT

Coleman, A. P. Corundiferous Nepheline-Syenite from Eastern Ontario. -
A new Analcite Rock from Lake Superior. - - - : - -
Colorado Formation, A Discussion and Correlation of Certain Subdivisions of
the. W.N. Logan - - - - - - - . - -
Commissao Geographica e Geologica, Brazil. Editorial by J. C. Branner -
“Constitution of Gaseous Celestial Bodies.” T.C.C. (Editorial) - - -
Connecticut, A Granite-Gneiss in Central. Lewis G. Westgate - - -
Creek Beds, The Sweetland. J. A. Udden~ - - - - - - -
Cretaceous of the Black Hills, as Indicated by the Fossil Plants, The. Lester
F. Ward, Walter P. Jenney, William M. Fontaine, F. H. Knowlton.

Review by W. N. Logan - - - - - .
Cummings, Uriah. American Cements. Review - Hive. Bains = - -
Curtis, G. C., and J. B. Woodworth, Nantucket. A Morainal Island - -
Cusps, Beach. Mark S. W. Jefferson - = = = = = 3 -

Davis, W. M. Physical Geography. Review by R.D.S. - - - -
Dawson, Sir William. Frank D. Adams - - -.
Devonian Deposit, A Peculiar, in Northeastern Illinois. Stuart Weller - -
Devonian, Dipterus in the American Middle. J. A. Udden - - - -
Devonian Formation at Milwaukee, Wisconsin, The Fauna of the. Charles E.
Monroe and Edgar E. Teller - . - - - - - -
Devonian Mollusca of the State of Para, Brazil. John M. Clarke. Review by
J.C. Branner - - - - - - - - - - -
Devonian of Northeastern Illinois, Descriptions of New Species of Diplodus
Teeth from the. C. R. Eastman - - - - - - -
Diamond Field of the Great Lakes, The. W.H. Hobbs - - - -
Dictyospongide, The Paleozoic Reticulate Sponges constituting the Family.
James Hall and John M. Clarke. Review by S. W. - - - -
Diplodus Teeth from the Devonian of Northeastern Illinois, Descriptions of
New Species of. C.R. Eastman - - - - - - :
Dipterus in the American Middle Devonian. J. A.Udden~ - - - -
Discussion and Correlation of Certain Subdivisions of the Colorado Formation,
A. W.N. Logan - - - - - - - - - -
Distribution Loess Fossils, The. B. Shimek - - - - - - -
Drainage, Ultimate, the Effect of Sea Barriers Upon. J. F. Newsom - -
Driftless Region of Wisconsin, Studies in the. G H. Squier - - = -
Doctrine of Crustal Quiescence and Readjustment. T.C. C. (Editorial) -
Do State Surveys Pay? H. F. B. - - - - - - - -

Eastman, C. R. Descriptions of New Species of au er Teeth from
Devonian of Northeastern Illinois - - - -

EDITORIALS :
A Proposed International Journal of Petrology. J. P. Iddings and
L. V. Pirsson - - - - - - - - - -
Application of raga) to the Determination of Earth Movements.
aes C. - - - - - - - - - -

Commissao Geographica e Geologica, Brazil. J. C. Branner - -

272

489
375

717

489
494

83
22)
445

79
295
7O1

489

700

295
788

334 INDEX TO VOLUME VII

Constitution of Gaseous Celestial Bodies. T.C.C. - - - -
Doctrine of Crustal Quiescence and Readjustment. T. C. C. - -
Geological Society of America. J. P. I. - - - - - -
International Geological Congress. J. P. I. - - - - - -
Marsh, Othniel Charles. H.S. W. - - - - - - -
Missouri Geological Survey. H.F. B.- - - - - - -
Model of the Earth by Thomas Jones. T.C.C. - - F - -
Reform in Scientific Nomenclature. T.C.C. - - - - -

The Duplication of Geologic Formation Names. F.B.Weeks - -
Volcanic Plugs. Israel C. Russell - - - - - - -
NolcanicePlugsima)eek-lininn - - - - - - - -
Elements, Season, and Time, in Sand-Plain Formation. Myron L. Fuller -
Emmons, S. F., J. E. Spurr and. Geology of the Aspen District, Colorado.
Review by W. T. Lee - - - - = - - - -

Essex County, Mass., The Petrographical Province of. Henry S. Washington

53, 105, 284,

Fauna of the Devonian Formation at Milwaukee, Wis., The. Charles E.
Monroe and Edgar E. Teller - - - - - - = -

Finch, J. W. Geological Survey of Iowa, Vol. IX. Review - - - -
Flint Implements of Table Mountain, The Pliocene Skull of California and
the. Wm. P. Blake - - - - - - = -
Fontaine, William M., Lester F. Ward, Walter P. Venice F. H. Knowlton.
The Cretaceous of the Black Hills as Indicated by the Fossil Plants.

Review by W. N. Logan - - - - - - -

Fossil Medusz. C.D. Walcott. Review by Stuart Weller - = - =
Fossii Plants, The Cretaceous of the Black Hills as Indicated by the. Lester F.
Ward, Walter P. Jenney, William M. Fontaine, F. H. Knowlton.

Review by W. N. Logan - - - = - = = = >

Fuller, Myron L. Season and Time Elements in Sand-Plain Formation - =
Geike, James. Earth Sculpture. Review by R.D.S. - =) = - -
Geography, Physical, Geology and, of Jamaica. R.S. Hill. Review by R. D.S.
Geology, A Reference List of Summaries of Literature on North American
Pre-Cambrian, 1892-8. C. K. Leith - - - - - -
Geology of the Aspen District, Colorado. J. E. Spurr and S. F. Emmons.
Review by W. T. Lee - - - - - - - 2 =

Geology and Physical Geography of Jamaica. R.S. Hill. Review by R.D.S.
Geology and Natural Resources of Indiana, Department of, XXIII Annual
Report. George H. Ashley. Review by A. H. Purdue - - -
Geology, the Ozarkian and Its Significance in Theoretical. Joseph Le Conte -
Geologic Formation of Names, the Duplication of. F.B. Weeks. (Editorial)
Geological Report on the Isle Royale, Michigan. Alfred G. Lane. Review by
eles 1 - - - - - - - - -
Geological Society of America. J. P. I. (Editorial) - - - = -
Geological Survey of Iowa, Vol. IX. Review by J. W. Finch - 2 = :

PAGE
92
295
94
188

401
619
404
509
297

96

97
452

721
462
272
517

631

814
99

814
452

S11
815

799

721

720
525
297

718
94
517

INDEX TO VOLUME VII

Geological Survey of Georgia, Preliminary Report on the Artesian Well System
of Georgia. S.W. McCallie.. Review by T.C.C.. - - - -

Georgia, Geological Survey of, Preliminary Report on the Artesian Well
System of Georgia. S.W. McCallie. Review by T.C. C. - -

Gilbert, G. K. The Great Ice-Dams of Lakes Maumee, Whittlesey, and
Warren. Frank B. Taylor. (A Review) - - - - -

Girty, G. H., Arnold Hague, J. P. Iddings, W. H. Weed, C. D. Walcott, T. W.
Stanton, and F. H. Knowlton. Geology of the Yellowstone National

Park. Review by Lf. ©. HH. ‘= - - - . - - -

Glacial Periods on an Atmospheric Basis, An Attempt to Frame a Working
Hypothesis of the Cause of. T.C. Chamberlin - - - -
Glaciers, IV, The Variations of. Harry Fielding Reid - - - - Ss
Goode, John Paul. The Piracy of the Yellowstone - - - - -
Review: Physical Geography cf New Jersey. R. D. Salisbury - -
Granite Rocks of Butte, Mont., and Vicinity. Walter Harvey Weed - -
Granite-Gneiss in Central Connecticut, A. Lewis G. Westgate - - -
Granitic Rocks of the Sierra Nevada. H.W. Turner - - - - -
Great Lakes, the Diamond Field of the. W.H. Hobbs - - -
Greenland, North, Some Notes onthe Lakes and Valleys of the Upper Nawetar
Peninsula. Thomas L. Watson - - - - - =
Grimsley, G. P. Special Report on Gypsum and Gypsum Cement Plasters.
E. H.S. Bailey and. Review by H. F. Bain - - - - -
Gulliver, F. P. Shore Line Topography. Review by R. D. S. - -
Gypsum, Special Report on, and Gypsum Cement Plasters, G. P. Soa and
E.H.S. Bailey. Review by H. F. Bain - - - -

Hague, Arnold, J. P. Iddings, W. H. Weed, C. D. Walcott, G. H. Girty, T. W.
Stanton, and F. H. Knowlton. Geology of the Yellowstone National
Park. Review by T.C. HH. - - - - -
Hall, James. Report of the New York State Geolocict, (ROey Review, Stuart
Weller” - - - - - - - - - - - -
Hall, James, and John M. Clarke. The Paleozoic Reticulate Sponges consti-
tuting the Family Dictyospongidae. Review by S. W. - - -
Hill, R.S. Geology and Physical Geography of Jamaica. Review by R. D. 5S.
Hobbs, W. H. The Diamond Field of the Great Lakes - - - -
Hopkins, T. C. Geology of the Yellowstone National Park. Arnold Hague,
J. P. Iddings, W. H. Weed, C. D. Walcott, G. H. Girty, T. W. Stan-
ton, and F. H. Knowlton. (Review) - - - - -

Iddings, J. P., and Arnold Hague, W. H. Weed, C. D. Walcott, G. H. Girty,
T. W. Stanton, and F. H. Knowlton. Geology of the Yellowstone
National Park. Review by T.C. H. - = - - - -

Editorial: Geological Society of America - - - - - -
International Congress, Geological, of 1900 - - - - -
Volcanic Plugs - - - - . - - - - - -
and L. V. Pirsson. A Proposed International Journal of Petrology — -

835
PAGE
722
722

621

709

545
217
2601
314
737
638
141
375

655

625
827

625

709
209

717
815
uS

709

709
94
188
97
700

836 INDEX TO VOLUME VII

Review: Geological Report on the Isle Royale, Michigan. Alfred C.
Lane - - - - - = = = : - - -

Igneous Magma, Experimental Investigation of the Formation of Minerals in
an, Morozewicz. Review by J. A. Jagger, Jr. - - - - -

Illinois, Northeastern, Descriptions of New Species of Diplodus Teeth from
the Devonian of. C. R. Eastman - - - - - - -

Illinois, Northeastern, A Peculiar Devonian Deposit in. Stuart Weller - -
Indiana, Department of Geology and Natural Resources of, XXIII Annual
Report, George H. Ashley. Review by A. H. Purdue - - -
Inlandeises, Die Stillstandslagen des Letzen, etc., K. Keilhack. Review by
IR IDG S)o) = - = - : - - - - -
International Geological Consrenee of 1900. J. P. I. (Editorial) - - -
International Journal of Petrology, A ear Editorial by J. P. Iddings
and L. V. Pirsson- - = - - - - - - -

Iron Making in Alabama, 1898, W. B. Phillips. Review by H. F. Bain - -
Isle Royale, Michigan, Geological Report on, Alfred G. Lane. Review by
Jeb - - - - - - - - - -

Jaggar, J. A., Jr. Experimental Investigation of the Formation of Minerals in
an Igneous Magma, Morozewicz. (Review) - - - - -

Jamaica, Geology and Physical Geography of, R. S. Hill. Review 8) R. D.S.

Jefferson, Mark S. W. Beach Cusps- - - - -

Jefferson, Walter, D. A Certain Type of Lake Formation in the Canadian
Rocky Mountains — - - - - - - - - -

Jenney, Walter P., Lester F. Ward, William M. Fontaine, and F. H. Knowlton.
The Greene of the Black Hills as Indicated by the Fossil Plants.
Review by W. N. Logan - - - - - - - - -

Jones, Thomas. Model of the Earth. Editorial by T. C.C. - - - -

Kansas Academy of Science, Vol. XVI. Review by T. C. C. - - -
Kansas, Correlation of Carboniferous Rocks of Nebraska with those of. C. S.
EhOSSCiine= - - - - - - - - - - -
Keilhack, K. Die Stillstandslagen des Letzen Inlandeises, etc. Review by
1S IDES S - - - - - - - - - - -
Keyes, C. R. American Homotaxial Equivalents of the Original Permian -
Knight, W. C. The Nebraska Permian - - - - - - -
Knowlton. F. H., Arnold Hague, J. P. Iddings, W. H. Weed, C. D. Walcott,
G. H. Girty, T. W. Stanton and. Geology of the Yellowstone
National Park. Review by T. C. H. : - = - = =
Knowlton, Lester F. Ward, Walter P. Jenney, William M. Fontaine. The Cre-
taceous of the Black Hills as Indicated by the Fossil Plants. Review
by W. N. Logan - - - - - - - - - =
Kiimmel, H. B. The Newark Rocks of New Jersey and New York - -

Lakes and Valleys of the Upper Nugsuak Peninsula, North Greenland, Some
Notes on. Thomas L. Watson - - - - - - =

PAGE
718
300

489
483

720

824
188

700
213

718

300

237

247

814
404

516
342
824

321
357

709

814
23

655

INDEX. TO VOLUME Vil

Lake Formation in the Canadian Rocky Mountains, A Certain Type of.
Walter D. Jefferson - = = = = = = = = =

Lake Superior, A New Analcite Rock from. A. P. Coleman - - -
Lane, Alfred C. Geological Report on the Isle Royale, Michigan. Review
lovaalalea dl - . - - - - - - -

Le Conte, Joseph. The Ozarkian and its Significance in Theoretical ees
Lee, W. T.—Reviews: Bulletin of the American Museum of Natural History,
Vol.X - - - - - - - - - - - -
Geology of the Aspen District, Colorado. J. E. Spurr and S. F. Emmons
University Geological Survey of Kansas, IV. S. W. Williston - .

Leith, C. K. A Reference List of Summaries of Literature on North American
Pre-Cambrian Geology, 1892-1898 - - - - - - -

Summaries of Current North American Pre-Cambrian Literature 190, 406,

Leverett, Frank. The Lower Rapids of the Mississippi River. — - - -
Loess Fossils, The Distribution of. B. Shimek - - - - - =
Logan, W. N. A Discussion and Correlation of Certain Subdivisions of the
Colorado Formation - - - - - . - - -

Review: The Cretaceous of the Black Hills as Indicated by the Fossil
Plants, Lester F. Ward, Walter P. Jenney, William M. Fontaine, and

F. H. Knowlton - : - - - - - - -

Lower Rapids of the Mississippi River, The. Frank Leverett - - -

Marsh, Othniel Charles, H. S. W.. Editorial - - - - - -
Maryland Geological Survey, II. G. P. Merrill and E. P. Mathews. Review
by E.R. Buckley - - - - - - - - - -
Mathews, E. P., and G. P. Merrill. Maryland Geological Survey. II. Review
by E. R. Buckley - - - - - : -
McCallie, S. W. Geological Survey of Georgia, Belair Bao on the
Artesian System of Georgia. Review by T.C.C. - - - -
Merrill, G. P., and E. P. Matthews. Maryland Geological Survey. II.
Review by E. R. Buckley - - - - - - - - -
Michigan Geological Report on the Isle Royale, Alfred C. Lane. Review by
JP esIe™ = : - - - - - - - - - .
Mississippi River, The Lower Kapids of. Frank Leverett — - - - -
Missouri Geological Survey. B. F. B. (Editorial) - - - : - .
Model of the Earth, by Thomas Jones; Editorial by T. C. C. - - -
Montana, Butte, Granite Rocks of. Walter Harvey Weed - - - =
Morainal Island, A, Nantucket. G. C. Curtis and J. B. Woodworth - -
Monroe, Charles E.and Edgar E. Teller. The Fauna of the Devonian Forma-
tion at Milwaukee, Wisconsin - - - - - - -

Naming of Rocks, The. C. R. Van Hise - - = - - - -
Nantucket, A Morainal Island. G. C. Curtis and J. B. Woodworth - -
Nebraska with those of Kansas, Correlation of Carboniferous Rocks of. C.S.

Prosser - - - - - - - - - - - -
Nebraska Permian, The. W. C. Knight - - - - - - -

PAGE

722

686

357

838 INDEX TO VOLUME VII

Nepheline-Syenite from Eastern Ontario, Corundiferous. A. P. Coleman -
Newark Rocks of New Jersey and New York, The. H. B. Kiimmel - 2
New York State Geologist, Report of the, 1895. James Hall. Review, Stuart
Weller’ - - - - - - - - - - - e
New York, The Newark Rocks of New Jersey and. H. B. Kiimmel = =
New Jersey and New York, The Newark Rocks of. H. B. Kiimmel - -
Newsom, J. F. The Effect of Sea Barriers upon Ultimate Drainage - -
Nipissing and Temiscaming Map Sheets, Report on the Geology and Natural
Resources of the Area included by the, comprising portions of the dis-
trict of Nipissing, Ontario, and of the county of Pontiac, Quebec.
A. E. Barlow. Review, F. D. Adams = = 2 = z =
Nugsuak Peninsula, North Greenland, Some Notes on the Lakes and Valleys
of the Upper. Thomas L. Watson - - - - - = :
Ocean and its relation to the Carbon Dioxide of the Atmosphere, The Carbon
Dioxide of the. C.F. Tolman, Jr. - - - = : o S
Ontario, Corundiferous Nepheline-Syenite from Eastern - - - - -
Ore Deposits in the Sierra Nevada, Replacement. H.W. Turner - - -
Ozarkian, The, and its Significance in Theoretical Geology. Joseph Le Conte
Paleontology, A Century of Progress in. Stuart Weller - - - -
Para, Devonian Mullusca of the State of, Brazil. John M. Clarke. Review by
J.C. Branner - . 2 = = 2 2 é 5 ‘ x
Permian, American Homotaxial Equivalents of the Original. C.R. Keyes -
Permian, The Nebraska. W. C. Knight - - - - - = :
Phillips, W. B. Iron Making in Alabama, 1898. Review by H. F. Bain -
Physical Geography of New Jersey. R. D. Salisbury. Review by J. P. Goode
Piracy of the Yellowstone, The. John Paul Goode = = = = 2
Pirsson, L. V., J. P. Iddings and. A Proposed International Journal of Petrol-
ogy - - © - - - : - - - - -
Pliocene Skull, The, of California and the Flint Implements of Table Mountain.
Wm. P. Blake - - - - - - - - - = <
Pre-Cambrian Geology, A Reference List of Summaries of Literature on North
American, 1892-1898. C. K. Leith - - - = > : =
Pre-Cambrian Literature, Summaries of Current North American. C. K.
Leith - - - - - - - - - - 190, 406,
Prosser, C. S. Correlation of Carboniferous Rocks of Nebraska with those of
Kansas” - - - - - - - - - - = :
Province of Essex County, Mass., The Petrographical. Henry S. Wash-
ington - - - - - - - - - 53, 105, 284,
Purdue, A. H. Department of Geology and Natural Resources of Indiana,
XXIII Annual Report, George H. Ashley - - - - -
Recent Books on Physiography: Rivers of North America, I. C. Russell;
Earth Sculpture, James Geike; Physical Geography, W. M. Davis.
Review by R. D. 5S. - - - - - - - - -

713
655
585
437
389
525
496

813
321

357
213

314
261
700
631
790
702
342
463

720

SII

INDEX TO VOLUME VII

Reference List of Summaries of Literature on North American Pre-Cambrian
Geology, 1892-1898. C.K. Leith - - : = és :
Reform in Scientific Nomenclature. Editorial by T.C.C. — - - - -

Reid, Harry Fielding. The variations of Glaciers . - - : Bs tae

Report on the Geology and Natural Resources of the Area included by the
Nipissing and Temiscaming Map Sheets, comprising Portions of the
District of Nipissing, Ontario, and of the County of Pontiac, Quebec.
A. E. Barlow. (F.D. Adams) - - = = = 3 e

Reticulate sponges constituting the Family Dictyospongidae, The Paleozoic.
James Hall and John M. Clarke. Review by S. W. - - -

REVIEWS: Bulletin of the American Museum of Natural History. X. (W. T.
Lee) - - - - - - - - - - - -

Department of Geology and Natural Resources of Indiana, XXIII
Annual Report. George H. Ashley. (A. H. Purdue.) - - -
Devonian Mollusca of the State of Para, Brazil. John M. Clarke. (J.C.
Branner) - - - - - - - - - = =
Die Stillstandslagen des Letzen Inlandeises, etc. K. Keilhack. (R. D.S.)
Experimental Investigation of the Formation of Minerals in an Igneous
Magma. Morozewics. (J. A. Jaggar, Jr.) - = : 2 =
Fossil Meduse. G. D. Walcott. (Stuart Weller) - - :
Geology and Physical Geography of Jamaica. R.S. Hill. (R.D.S.) -
Geology of the Yellowstone National Park. Arnold Hague, J. P. Iddings,
W. H. Weed, C. D. Walcott, G. H. ree T. W. Stanton, and F.C.
Knowlton!) (2..C. H.) — - - - - - - - :
Geological Report on the Isle Royale, Michigan. Alfred C. Lane.
(J2P. 1.) - - - - - - - - - - - -
Geological Survey of Georgia, Preliminary Report on the Artesian Well
System of Georgia. S.W. McCallie. (T.C.C.)_ - - - >
Geological Survey of Iowa, Vol. IX. J. W. Finch = = - é
Ice-dams, The Great, of Lakes Maumee, Whittlesey, and Warren, Frank
Berbaylores(G. 1..G,); ~ - - - - - - - - -
Iron Making in Alabama, 1898. W. B. Phillips. (H.F. Bain) - -
Kansas Academy of Science, Vol. XVI. (T.C.C.) - - - -
Maryland Geological Survey. IJ. G. P. Merrill and E. P. Mathews.
(E. R. Buckley) - - - - - - - - - -
Physical Geography of New Jersey. R. D. Salisbury. (J. P. Goode) -
Recent Books on Physiography : Rivers of North America, I. C. Russell ;
Earth Sculpture, James Geike; Physical Geography, W. M. Davis.
(Ree S:) - - : = - - - - - - -
Report of the New York State Geologist, 1895, James Hall. at
Weller) - - - - - = ~ - - - -
The Cretaceous of the Black Hills as indicated by the Fossil Plants, Les-
ter F. Ward, Walter P. Jenney, William M. Fontaine, F. H. Knowlton.
(W. N. Logan) - - - - - - - - - -
The Paleozoic Reticulate Sponges constituting the family Dictyo-
spongidae. John M. Clarke and James Hall. (S. WW.) - - -

PAGE

717

840 INDEX TO VOLUME VII.

The Upper Silurian Fauna of the Rio Trombetas, State of Para, Brazil,

John M. Clarke. (J.C. Branner) - - - = - - :
University Geological Survey of Kansas. IV. 5. W. Williston. (W. T.

Lee) - - = - - - - - - - - -

West Virginia Geological Survey, Vol. I. I. C. White. (Stuart Weller)

Rio Trombetas, The Upper Silurian Fauna of the, State of Para, Brazil. John
M. Clarke. Review by J. C. Branner - - : = 5 -

Rivers of North America. Russell, Israel C. Review by R. D.S. - -
Rocky Mountains, A Certain Type of Lake Formation in the Canadian. Wal-
ter D. Jefferson - - - - = = - - = =

Rocks, The Naming of. C.R. Van Hise. - : - - - - -
Russell, I. C., Rivers of North America. Review by R. D.S. - - -
Volcanic Plugs. (Editorial) - - - - - E = =

Sand-Plain Formation, Season and Time Elements in. Myron L. Fuller -

Salisbury, R. D. Physical Geography of New Jersey. Review by J. P. Goode

Reviews: Die Stillstandslagen des Letzen Inlandeises, etc. K. Keilhack

Recent Books on Physiography: Rivers of North America; Earth Sculp-

ture. James Geike; Physical Geography. W.M. Davis - - -

Shore Line Topography. fF. P. Gulliver - - - - - -

Geology and Physical Geography of Jamaica. R.S. Hill - - -

Sea Barriers, The Effect of, upon Ultimate Drainage. J. ¥. Newsom — - -

Season and Time Elements in Sand-Plain Formation. Myron L. Fuller 2

Shimek, B. The Distribution of Loess Fossils - - - - - -

Shore Line Topography. F. P. Gulliver. Review by R. D.S. - - -

Sierra Nevada, Granitic Rocks of the. H.W. Turner - - - - -

Sierre Nevada, Replacement Ore Deposits in the. H.W. Turner - - -

Silurian Fauna of the Rio Trombetas, The Upper, State of Para, Brazil. John

M. Clarke. Review by J. C. Branner - - - - - -

Sir William Dawson. Frank D. Adams - - - - - - -

Spurr, J. E. and S. F. Emmons. Geology of the Aspen District, Colorado.

Review by W. T. Lee - - - - - - - -

State Surveys, Do they Pay? Editorial H. F. B. - - - - -

Stanton, T. W., Arnold Hague, J. P. Iddings, W. H. Weed, C. D. Walcott, G.

H. Girty, F. H. Knowlton. Geology of the Yellowstone National

Park. Review by T. C. H. - - - - - - - -

Stillstandslagen, Die, des Letzen Inlandeises, etc. K. Keilhack. Review by

Ry DAS - - - - - - - - - - -
STUDIES FOR STUDENTS:

A Century of Progress in Paleontology. Stuart Weller - - -

The Development and Geological Relations of the Vertebrates. E. C.

Case - - - - - - - = = = : -

Studies in the Driftless Region of Wisconsin. G.H.Squier - - - -

Squier, G. H. Studies in the Driftless Region of Wisconsin - - -

Summaries of Current North American Pre-Cambrian Literature. C. K. Leith

PAGE
813

100
426

813
S11

247
686

511
96

452
314
824

SII
827
815
445
452
122
827
141
389

813
727

721
701

709
824
496
163

79
79

190, 406, 702

INDEX. TO VOLUME VIT

: PAGE
Summaries of Literature on North American Pre-Cambrian Geology, A Refer-
ence List of, 1892-1898. C.K. Leith - - - - = - 790
Sweetland Creek Beds, The. J. A. Udden~ - - - - - - - 65
Table Mountain, The Pliocene Skull of California and the Flint Implements of.
W.P. Blake’ - - - - - - - - - - zi (oyeiat
Taylor, Frank B. The Great Ice-Dams of Lakes Maumee, Whittlesey, and
Warren. Review by G. K. G. ae - - - - - - 621
Temiscaming Map Sheets, Report on the Geology and Natural Resources of
the Area included by the Nipissing and, comprising Portions of the
District of Nipissing, and of the County of Pontiac, Quebec. A. E.
Barlow. Review by F. D. Adams_ - - - - - - ie Muy ke
Theoretical Geology, The Ozarkian and its Significance in. Joseph Le Conte 525
Tolman, C. F., Jr. The Carbon Dioxide of the Ocean and its Relation to the
Carbon Dioxide of the Atmosphere - - - - - - - 585
The Influence of the Carbonic Acid of the Air upon the Temperature of
the Ground. Svante Arrhenius. (Review) - - - - - 623
Topography, Shore Line. F. P. Gulliver. Review by R. D. S. - - - 827
Turner, H. W. Granitic Rocks of the Sierra Nevada - - . - 2a RTA
Replacement Ore Deposits in the Sierra Nevada - - - - - 389
Udden, J. A. The Sweetland Creek Beds - - - - - - - 65
Dipterus in the American Middle Devonian - - . - - 494
Ultimate Drainage, The Effect of Sea Barriers upon. J. F. Newsom - - 445
Valleys of the Upper Nugsuak Peninsula, North Greenland, Some Notes on the
Lakes and. Thomas L. Watson - - - - - - - 655
Van Hise, C. R. The Naming of Rocks - . - . - - - 686
Variations of Glaciers. IV., The. Harry Fielding Reid - - - =e 27
Vertebrates, The Development and Geological Relations of the. E.C. Case 163
Volcanic Plugs. Israel C. Russell. Editorial - Sears - - - 96
Volcanic Plugs. J. P. I. Editorial . - - : - - - - 97
Walcott, C. D., Arnold Hague, J. P. Iddings, W. H. Weed, G. H. Girty, T. W.
Stanton, and F. H. Knowlton. Geology of the Yellowstone National
Park. Review by T. C. H. - - - - - - - - 709
Fossil Meduse. Review by Stuart Weller - - - - - - 99
Ward Lester F., Walter P. Jenney, William M. Fontaine, and F. H. Knowlton.
The Cretaceous of the Black Hills as Indicated by the Fossil Plants.
Review by W. N. Logan - - - - - - - - - 814
Washington, Henry S. The Petrographical Province of Essex County, Mass.
10 = a Ws ee a Soe as 53, 105, 284, 463
Watson, Thomas L. Some Notes on the Lakes and Valleys of the Upper Nug-
suak Peninsula, North Greenland - - - - - - - 655
Weed, Walter Harvey. Granite Rocks of Butte, Mont., and Vicinity - -
Arnold Hague, J. P. Iddings, C. D. Walcott, G. H. Girty, T. W. Stanton,
and F. H. Knowlton. Geology of the Yellowstone National Park.
Review by 1. C. Hi... - - - - - - - - = 709

842 INDEX TO VOLUME VII

Weeks, F. B. The Duplication of Geologic Formation Names. (Editorial) -
Weller, Stuart. A Century of Progress in Paleontology - - - -
A Peculiar Devonian Deposit in Northeastern Illinois - - - -
Reviews: Fossil Medusz. C. D. Walcott - - 2 : 2 E
Report of the New York State Geologist, 1895. James Hall - =
The Paleozoic Reticulate Sponges constituting the Family Dictyospongi-
dae. James Hall and John M. Clarke © z = 2 5 =
West Virginia Geological Survey, Vol. I. I. C. White - - -
West Virginia Geological Survey, Vol. I. I. C. White. Review by Stuart
7) NWeallee: oe - - - - - - - - - - -
Westgate, Lewis G. A Granite-Gneiss in Central Connecticut - x -
White, I. C. West Virginia Geological Survey, Vol. I. Review by Stuart
Weller - - - - - - - - - - - -
Williams, H.S. Marsh, Othniel Charles. Editorial - - - = :
Williston, S. W. University Geological Survey of Kansas. IV. Review by
Wedvwleec - - - - - - - - - - -
Woodworth, J. B. Nantucket, A Morainal Island. G. C. Curtis and - =
Working Hypothesis of the Cause of Glacial Periods on an Atmospheric Basis,
An Attempt to Frame a. T.C. Chamberlin - - - 545, 667,
Yellowstone National Park, Geology of, Arnold Hague, J. P. Iddings, W. H.
Weed, G. D. Walcott, G. H. Girty, T. W. Stanton, and F. H. Knowl-
tome alin Cag kle - - - - - - - - - -
Yellowstone, The Piracy of the. John Paul Goode - - - - -

PAGE
297
496
483

99
209

717
426

426
638

426
401

100
326

751

709
261

44
ae

aia

VEAL yea

hota eb eet

Pik wey uals
Fe hays

ay BAA Has
ee

ya Srna

eam *

tate

ate Subaa
eh

} Ee) ee) ose eG &
sayy *
HPA thot Ak A

uit Bi cpakNn awe
ot ian

Sine

a.
Wey ANieha
NAO MER Wt}

Vieohi a!

Rtas at
we en te a

HK

Re)
adineatcioent
fat NA HAlareg yon
bay ine ree ui ”

A ea! we
A ew y
MV Geb chentyyh
ied main
19 HAR Otek gy
aa eta ML NYE »
A Ra

tad
eh
fe,
AG s tat Athen
V 6S Ati gs 401)
Pt int
ny ern
ce n
PASH IR he alnny Veh net

ME ey oth a ink ”
OP HEH een ine Si ae tet
TT Se Me ew LET |
NG Aee arom Sale
A tn ha i

Ay meaning

Me medaottti a At Oat

‘ neal ae
nota: Vin ee naety vend cui iy
MIAH oe hss eal rene Ma Alera uti eine
Ys eit pri i vet
sales yea neu
Werle af

Aen a 89h) hd

th ee
‘i

aia
neh ay Ashe * inns

he ae
salina pest Mane i) Hisyhunest fe ae it

te

i) Hela owe ay ‘if Aaa iy

arty el way
aa Ny

Manat
Sun Rhy a
DAA EMA
uN 43 Uy 49 sas i!
mht

mn Nt
pyaty Mehedsd Vy nt
Ae USL Sa
aie a Workin my

TOW 0

Het

in,

i vt) NS has i

yak if phe f
aheal 4
‘ On

(Tie)

as A

ha {
aS Latent

Reguhy
RE Net
bitte is :
se a
7 ea

Mouse eau
eae egy

‘ A a AY

"aren
Na Me WIaO tt
hye WY ah wh nt

Wy

*
Cee ns
SIVAN SN
Any at
Stati at
muta tay

Aye
3 Ma age y
Deh aD
VIVAL
Aq Albi sie
ah

HAH Chay
Heal

Ley)
mh

Al}
} SANE H SL 4) ai ly ai
tes crn ae ay cabin At sty
Laure

AN 4 ah tide Spam gh

an hh i se bis tate

1m he p oer

halt. 1 6 sh ld A aiiie
4 Cneets re

we sa

AY 4): i ‘ 4 WA
i ie Amiel ayy , (ieee
MAAN CRD) i iN i h

ete Ue
Nay THe 4 My i y
Na veer fl Wit Re Wy t

me
he iy
i Ahan 4 a enti
ay Sa ny. " fh h
Wed) © Geen fay ehi
wine Why)

Cy £ iy

nN ay ware’

Dt eae aetna
DS ta a TE

rece a sh Nes
Ne why yn CHE,
mn eh NAN
4\ *e a}
My iy EN ,
Ai ava Wawa
ta a ids elt Vata tah uyact
hie ve iy ath Ny} hs Haas Awon
Ait eRe winaicn ny A pin tart f
Ue ey wih, ry oie oy Wie
AB em) Ar aie ea ih) Puy
gy Set Aa
erent
sua itt Dh Als
cnt ary
Naty Wt
wa

mu

Vi}
ny by

ent
Dent WACm A Rane
‘KY AASB ATAH aL yA

ALM EN As beg fi
bMS eer Uh Ne WEE Ante 49 Wh hhh y
Samy hed at #) Hahei ae

DUPER BAS Ay tet ah Hae et
AMM q

Wi

4
A re nen
at at SD

rs a
Png

vail
Piel a
a

Fewest 4s Al p45 ay sitar
wey Bets ye statis

Neb ito
A a at hey he tt
“

Ava iy

Ni iy TOK W YAN AC ALE YS eu

MUNA edd ie Ay My mes Wea hh LIS MSN ONY
VR doe i

MN Ubek

iW SRS m8, Reb te by

s RM el eh ly oe

DW AMM ON Dt ait

NN RAE ASC
1 Uae Hy We Ohi

ere Nee
cea

Whe
ie
Wachee

it

~ SMITHS ONIAN IN

|. i | i ii

(ry
RAN yl

Shae ht
Heh een AR KN}
ek ny

Vi

3 908

i MET Wy 9932 _

‘
iy » i yhehat
ORapis wu Alt Pye

wat
ty Tenth ta 0 "
yi a6 Oe a cae
SO Ma AAU Dok ‘
Va deal wan CO MV ASP LPAI
HV DG hy

WM ER ALANA PAE
AW ER A fae ae

WN
PNAC Hy

Wee hy
SO A, "
bi OW AR f

INA Ay ay

NAA ta ied

UES 6 Ab 0
Chi ew art WA ey i
Pe ah A AR a

OAL WY

ot Maley
torn Licey
bet Me Av Y

i Wtbeg ry

b Ava

i slop

EN ma un Wa

uh
A EN

iy ‘
nS iM tung A

Nig
i al (eh

i

hi Wey MUTA ety

San te He Raut) \
SNH wan

AAA
etait i) Mit ¥

it) Y

y ty ‘: ayy Se

Mall * aN
ry
Write in SH Aa

Deis #4 Oy 1 aa ely ) iy

saan’ ‘OUP fyb “1 Sat vt ai

ate Vy Oh 1

Ht Heaps
ie ay a
atk

1th iN HAVA
ONIN i
et 1) 88 Ah

ahi i

Yeivy

ae
WO (oh Mi

Me
iff

aun’

AUS)

Waa iat uy 4

¢
div wel

4)

i oy
Jihoaythy
‘ ri! at iat
(wand 4)
ity AVN) HUN Ae

AeaLHeNS heat
Sakti iy

AKA ANAL aL Hs it
AUF ia
i HbR aN 8
ety

Ri het
STC Ter hs oy Vi WS

Hn ey \ ih
ihe yey) ity Tha \ a
a 1 ‘\ Waid eA Wy 4 At
PUN eA Bae *

Ki
4

Soa
+o * i ‘i Ue Le Ai ‘a My
MAL AN I ASA

, iy
fie

et

uN
Sue wi
Wy

\ i Rr
A isis ai rei

Miy AW ALAN WA
eisin eV iy ae
» Noe

Rey BAW

LAL eee AL iH) Honey
\

i)
Seb jy

4) 4 % wh

ha

oy

) ei
ARLE
1

Ae

Matty
4) ni Ny a i

nit " (i
iy" eas

Wy 1

iN AN ALEC

WY: Ha 4) (
\\

Nena aS
PANO)
beh wALK ID

ita eAte May
aie Hh Ny 4 yy Wir th ‘

HERA

Cot
Ae Ca

Hay
a

1
Poirot Y
Ay titi

cee aut

LIAM Te
ay yaoi us
SOUR
Ch

Aan
Haye ye yo
4 " \

Ue Ney

SAM AEE

LP Ae Ah)
The HAT Wa i!

oe
Wi Wish

V4,
Pie aiiny

i

aa

Titik
iy

Bly,
Ah
u

WT OA he
Walehietieby Ay
EN,
AM VA TF
} SSAA NO AXE
PO MAREE RD WAAR RAM teh SA tuted
ny Ny a Ne 4s DUAN.
On hi Thetis 8 Ww AN:
y Ww NALA eRe Als
UNL,
Hone (4b

san! Aas

iy
i! Ki nye 4
HU isa gy

Ma Gd

NAAN MAIS TSE Aaa Tale} WAH tie
An A 4 hy A Dh lp “4 Ny

WA AL,
ALONG 6
A AM HEA

is

Sa OAT My ted Hoth
ANIL ds lee oy
Wi 0 Wi
iy Wy \ " relly at
UN iN

At HY Way
Qos

UI AKU
t ba Ma »
LOW AQ A
WAV Ae WN WAL EAL ie AAD

Wud

ei becshstaey i
% Ha aK 4

WA i hoe Lae

Aten } i hata bah WlaG

oie: WAveud ‘ \ ' if sa a ti be
, WBA BRAY

NA

a yi i Re

\ i

i ONT WH tA

hy aut eye
Mis RL
HA TALS

ht

Oy AAO Ge teehee

4 PAU RDU ARON DT

Wid bok Hadieh & Wah
Wish shid BHM ensue tei tay

PG ALB ty PS ee When ay

ea)
‘ Hendy wi
WT OUM TL thy

RCM Can SET a Ns
De oy Whe (deals

DALAL sitesi
4 NAA ND

Wed day a

Aaah

4
WAP
wi tay i

in h
vie VATE i crea iT