4 
WARD’S NATURAL SCIENCE BUXLETIK. 
ARE WE DRYING UP? 
Borne years ago Prof. J. D. Wliitney, of Har- 
vard College, contributed an article under this title 
to the American Naturalist, and recently he has 
written a book upon geological climate, in which 
the same ideas are set forth more at length. It 
is his belief that we are drying up ; that from age 
to age the climate of the earth is becoming less 
and less moist, and that the tendency in that 
direction is now so decided as to be perceptible 
in changes recorded by human history. The 
evidence he brings forward in support of his the- 
ory is of considerable variety, but may be classi- 
fied as historic and pre-historic. The historic, 
again, is partly political and partly natural. 
The political evidence is found in the deca- 
dence of empires. Persia was once the center 
of power and civilization, but its glory has 
passed away, and the land is no longer the gar- 
den that oriental historians pictured. So of 
Arabia, Egypt, Greece and Italy. The use of 
this argument was in a certain sense necessary, 
because no universal theory can be complete 
unless it explains the fall of the Roman 
Empire; but in the present case it unfortu- 
nately reacts upon itself. If a universal 
diminution of moisture degraded Egyptian 
civilization and power, how was it that the 
Persian at the same time arose? If aridity de- 
stroyed the Persian Empire, how was the Arabian 
able to succeed it? And, in general, if the decay 
of an empire or civilization, in a region where 
agriculture and habitation are difficult, is to be 
ascribed to a change of climate, should not the 
original growth of that empire or civilization be 
ascribed to a climatic change of opposite char- 
acter? 
The natural evidence is more to the point. 
Four thousand years ago, according to Chinese 
history, Lake Lob was an extensive inland sea, 
whereas now it is a salt lake of limited extent. 
Then as now, it was entirely disconnected with 
the ocean; and lakes of that character must re- 
spond very perfectly to climatic changes, and 
especially to changes in rainfall. With copious 
rain they rise and spread; with meager rain they 
shrink. It sometimes happens, indeed, that a 
river is diverted from its course, so as to become 
tributary to some different body of water, or 
that its water is spread out upon the land by 
man, to subserve purposes of irrigation, and that 
in this way an inland lake is deprived of a por- 
tion of its supply; but no one has suggested any 
such explanation for the shrinkage of Lake Lob, 
and the presumption is in favor of Professor 
Whitney’s conclusion that the rainfall in central 
Asia was greater four thousand years ago than 
it is now. In the same region are two other 
saline lakes, the Caspian and the Aral, whose 
waters have no connection with the ocean, and 
whose histories can be traced back, with more or 
less confidence, for two thousand years. In that 
period each appears to have expanded and 
shrunk several times, but on the whole their 
areas have diminished. Humboldt, too, reported 
that the lake of Valencia, in South America, 
had been gradually diminishing for the fifty 
years preceding his visit. 
Of the same import are some recent changes 
in the magnitude of glaciers. In the Alps, the 
Caucasus and the Pyrenees, all the principal gla- 
ciers are now becoming shorter, their lower ex- 
tremities gradually receding up the valleys; and 
this change, according to Whitney, has been in 
progress in some localities for fifty years, and in 
others for twenty-five. We have no direct means 
of comparing the precipitation in those regions 
during the last fifty years with that of the pre- 
ceding fifty, but it is safe to say that if it has been 
less, the diminution should tend to cause such a 
shrinking of the glaciers as has been observed. 
The geological evidence is of the same nature. 
At a late epoch the great basin in which the 
Caspian and Aral are situated seems to have 
been occupied by a large body of water, possibly 
connected with the Arctic Ocean. It is believed, 
too, that there have been lakes in Saliara; and it 
is recorded by Agassiz that ancient shore-marks 
surround Lake Titicaca at an altitude of three or 
four hundred feet above its surface. In our own 
country the desert region of the Great Basin was 
occupied by a system of large and small lakes — 
the largest of which rivaled Lake Huron in size. 
Of the actuality of these facts there can be 
little question, and it will readily be admitted 
that each of them is indicative of a change of 
climate. If they were the only facts pertinent 
to the subject, they would certainly leave the 
presumption in favor of his theory; but they are 
not, and in my judgment there are opposing 
facts of equal weight. 
In the first place, the recent diminution of 
rainfall to which Whitney calls attention has not 
been universal. While the glaciers of the Alps 
have been shrinking, those of Iceland and New 
Zealand have been growing, and in the same 
period all, or nearly all, the lakes of our Great 
Basin have increased in volume. Great Salt Lake 
is eight or ten feet deeper than it was thirty-five 
years ago, and Pyramid Lake is twenty-five feet 
deeper. Lake Valencia, too, which had been 
falling for fifty years previous to Humboldt’s 
visit, was reported by the next scientific traveler 
to be again rising. 
It is a peculiarity of the geological evidence, 
that a sort of natural selection ranges nearly all 
the observations on one side. Maxima of moist- 
ure make a conspicuous record; minima, as a 
rule, do not. Whatever the oscillations through 
which an iidand lake may pass, the only traces 
evident to the casual observer are water-lines 
above the present water level, and it is only by 
careful search and by indirect methods that it is 
possible to demonstrate periods when the supply 
of moisture was less than at present. In the case 
of the lakes of the Great Basin, however, some- 
tiling of this sort has been accomplished. It is 
definitely known that the history of Lake Bonne- 
ville, the largest of the Quaternary lakes of that 
region, was not a continuous shrinkage from a 
maximum volume to a minimum, but was made 
up of oscillations to and fro. Before it was 
formed, the region was fully as dry as it is now, 
and it so continued for a period that was long in 
comparison with the age of the lake. After the 
lake had been formed, and had reached nearly 
its maximum size, its waters dried away, and 
were again restored; and in this interregnum 
there is good reason to believe that the local cli- 
mate was even more arid than to-day. Lake 
Lahontan, which belonged to the same series, 
had a similar history, being flooded twice and 
reduced to dryness in the interval; and in this 
case the second flooding was followed by a 
period of excessive dryness, when Pyramid, 
Winnemucca, Carson, Walker, and the other 
modern lakes of the basin had no existence. The 
facts from which these histories have been de- 
duced, are too voluminous to be given here, but 
may be found in the reports of the United States 
Geological Survey. 
It thus appears that the only region in which 
an attempt has been made to investigate the phe- 
nomena with thoroughness, does not sustain 
Prof. Whitney’s hypothesis of a universal and 
continuous degradation of climate through loss 
of moisture. And really, so far as the hypoth- 
esis is concerned, it matters little what evidence 
is derived from other arid basins, for a universal 
theory is overthrown by a single irreconcilable 
fact. If it should be found that Lake Titicaca 
was originally a large body of water, and 
gradually dried away, without ever return- 
ing to its old high-water marks, then it would 
be proper to conclude that the cause of the 
change was local, for a universal cause would 
have affected the lakes of Utah and Nevada in 
the same manner. And if it should be found 
that Lake Titicaca was originally small, 
and twice expanded so as to reach the high 
water marks Agassiz described, then, the cause 
of the changes being common to North and 
South America, there would be a strong pre- 
sumption that it was world-wide: but it would 
be impossible to regard it as continuous or sim- 
ple. In neither case could the theory of a uni- 
versal and continuous desiccation be maintained. 
The fact that at the present day the lakes and 
glaciers of some regions grow, while those of 
other regions shrink, favors the view that the 
causes of variations in the moisture element of 
climate are local; and if they are local, it is far- 
more likely that they will be discovered by the 
patient comparison of facts, than by bold specu- 
lation. G. K. Gilbert. 
GEOLOGY. 
Under this heading we invite attention in the 
first place to our extensive series of ROCKS — 
IGNEOUS, METAMORPHIC, and SEDIMEN- 
TARY — in which all the noted foreign localities, 
from the giant’s Causeway to the Islands of New 
Zealand, are represented, as well as other collect- 
ing-grounds nearer home. These are in speci- 
mens of a uniform size, with fresh surfaces and 
well marked characters. For those who are not 
specialists, and whom this wealth of material 
would puzzle to select from, we have carefully 
prepared several general COLLECTIONS OF 
TYPICAL ROCKS to facilitate the teaching of 
this subject. Briefly these collections are: 
The UNION SCHOOL COLLECTION of 50 
specimens, price $20. 
The ACADEMY COLLECTION of 100 speci- 
mens, price $45. 
The COLLEGE COLLECTION of 275 speci- 
mens (many of large size), price $200. 
These collections are arranged according to 
mineral composition. We have also two in 
stratigraphical order : 
A GENERAL STRATIGRAPHICAL COL- 
LECTION of 100 specimens, including Chart of 
Geological Time, price $50. 
ROCKS OF THE NEW YORK SYSTEM, 
110 specimens, with diagrams giving thickness 
of the different strata on the bottom of each block 
and with chart of Geological time, $80. 
The respective prices affixed include all labels 
and mountings , and 'printed catalogues. (For fur- 
ther details see our General Catalogue of Geology, 
price 20 cents.) 
Besides these trimmed rocks for collections we 
have a varied assortment of material illustrating 
special points in PHENOMENAL GEOLOGY 
(faults, veins, etc.) and as adjuncts in teaching 
GEOLOGICAL MODELS in wood, showing 
graphically the effects of erosion, faults, out- 
crops, etc. Also, RELIEF MAPS of interesting 
regions (Vesuvius, Etna, Mont Blanc, Colorado 
Canon and others), and GEOLOGICAL CHARTS 
and LANDSCAPES, for information concerning 
which consult our Catalogue of Geology and Lith- 
ology. 
M. Meuuier has been studying the meteorite 
which fell May 10, 1879, at Estherville, Emmet 
County, Iowa, and finds that it contains logron- 
ite, olivine, bronzite, peckhamite, pyrrhotine, 
schriebersite, magnetite and nickel. 
Since the issue of the last Bulletin we have 
received, from Galena, Ills., a choice lot of crys- 
tallized Galenas , Nail-head Calcites, associated 
with Marcasite, Stalacitic Marcasites, etc. 
PRICES OF PRECIOUS MINERALS. 
Price per Avoirdupois pound. 
Vanadium . 
Rubidiu m. 
Zireonium. 
Lithium . . . 
Glucinum . 
Calcium . . . 
Strontium.. 
Terbium 
Yttrium... 
Erbium 
Cerium 
Didymium 
Indium 
Ruthenium 
Rhodium . . . 
Niobium 
Barium 
Palladium.. 
Osmium 
Iridium 
Uranium ... 
Titanium. _ . 
Chromium . 
$10,000 
9,070 
7.200 
7,000 
5.400 
4,500 
4.200 
4,080 
4,080 
3.400 
3.400 
3.200 
3,200 
2.400 
2,300 
2,300 
1,800 
1.400 
1,303 
1,090 
900 
680 
565 
Gold 
Molybdiuin 
Thallium... 
Platinum .. 
Manganese . 
Tung-stun . . 
Magnesium 
Potassium . 
Aluminum. 
Silver 
Cobalt 
Sodium 
Nickel 
Cadmium .. 
Bismuth 
Mercury ... 
Arsenic 
Tin 
Copper 
Antimony.. 
Zinc 
Lead 
Iron 
$ 335.06 
. 225.00 
. 225.00 
. 150.00 
. 130.00 
. 115.00 
. 64.00 
. 64.00 
. 32.00 
. 20.00 
. 16.00 
. 8.00 
5.30 
. 4.00 
. 2.50 
95 
50 
25 
25 
15 
11 
08 
02 
