Feb. 15, 1883] 
NATURE 
359 
succession of ages that have since elapsed, erosion has 
been continuously in progress, and the result is the 
scenery of the Cafion region. Capt. Dutton gives what 
appear to be good reasons for believing that the larger 
rivers flow along the same channels which they took at 
the beginning, but that the minor tributaries, where any 
exist (and they are conspicuously absent in some wide 
districts), are comparatively recent in origin, and have 
been determined by modern surface conditions. The 
excavation of the Grand Canon of the Colorado has thus 
been going on ever since the -Eocene period. During 
that enormous interval the climate of the region appears 
to have passed through successive oscillations. There is 
no more skilful feature of the volume before us than the 
way in which the scattered facts that bear on this question 
are marshalled to their places and made to tell their story. 
Ancient river-beds, which for ages have been dry and are 
partly filled up with debris, open on the edge of the great 
chasm. They doubtless discharged their waters into the 
main river at a time when rains were abundant and 
watercourses numerous. But their fountains have long 
since been dried up, and their fading channels are almost 
gone. But all the while the Colorado and its larger feeders, 
drawing their supplies from far well-watered uplands, have 
continued their task of erosion until they have sunk their 
channels in some places more than a mile below the level 
of the plateau across which they flow. 
The process of the excavation of the Grand Cajon is 
treated at length, and much new information is given as 
to its varying conditions. The details of the erosion are 
described with great clearness. The two final chapters, 
wherein these subjects are discussed, contain much that 
is suggestive, and deserve careful perusal by all who take 
interest in questions of denudation. They are condensed 
pieces of reasoning which cannot be intelligibly sum- 
marised here, and which indeed one is hardly pre- 
pared to find in an official report. Like his colleague, 
Mr. G. K. Gilbert, Capt. Dutton properly lays great 
stress upon the influence of an arid climate as 
one of the chief factors in cafion excavation. He 
points out how the absence of vegetation exposes the 
surface of bare rock to the action of rain. But it may be 
doubted if the scanty rains of the region can do more 
than remove material already disintegrated. We have 
to account for the continuous lowering of the level of the 
’ plateaux,and the removal of sovast a depth of stratified rock 
from their surface. Capt. Dutton himself admits that most 
of the rain which falls upon the country is absorbed by 
the rocks, and gushes out in copious springs at the base 
of the cafion-walls, thereby notably increasing the volume 
of the river. But there is everywhere a perceptible disin- 
tegration of the rock at the surface. This decay cannot 
be attributed to frost, which in so dry a climate can have 
but small effect. It seems to be due in large measure to 
the superficial strain induced by a great daily range of 
temperature, And it is no doubt aided by the action of 
wind, which removes the loosened particles, and exposes 
a new surface to the same kind of disintegration. 
In conclusion, reference must be made to the truly 
magnificent series of illustrations by which this mono- 
graph is accompanied. The maps of the atlas give the 
reader a clear mental picture of the general topography 
and geological structure of the region. But it is by the 
pictorial illustrations that he will be chiefly fascinated. 
These are scattered profusely through the text, and form 
an important feature in the atlas. Mr. Holmes, whose 
reputation for the accurate and artistic rendering of geo- 
logical details is so well established, has here far sur- 
passed all his previous efforts, and has produced the most 
impressive and instructive geological pictures that have 
ever been made. His large coloured views of the Grand 
Canon are in themselves a series of lessons in geology 
far more interesting and efiective than can be supplied in 
words. The United States may be heartily congratu- 
lated on this first of the monographs of their Geological 
Survey. Let us hope that Congress will continue in the 
same liberal spirit the annual appropriations that have 
enabled the Director of the Survey and his associates to 
produce such splendid results. ARCH. GEIKIE 
CENTRAL ASIA 
Travels and Adventures East of the Caspian during the 
Years 1879-81, including Five Months’ Residence among 
the Tekkés of Merv. By Edmond O’Donovan. Two 
Vols. (London: Smith Elder, 1882.) 
Wanderings tn Baluchistan. By Major-General Sir C. 
M. MacGregor, K.C.B. (London: Allen and Co., 
1882.) 
R. O7DONOVAN’S venturesome excursion to the 
Mery Oasis stands out conspicuously as perhaps 
the most romantic episode in the recent annals of Central 
Asiatic travel. Yet in proceeding eastwards his original 
goal was not the Mervli Turkomans, but their western 
kindred, the Akhal Tekkés of the Daman-i-Koh. Sent 
out as the Special Correspondent of the DazZy News with 
the Russian expedition against those nomads in 1879, he 
was at first well received, and spent some profitable time 
during the progress of military operations on the Caspian 
seaboard. But after the death of General Lazareff, 
having been suddenly banished from Chikislar, his 
ramblings lay henceforth mainly within the North Persian 
frontier. Here he again went over the ground, with 
which we have been made tolerably familiar by V. Baker, 
Macgregor, Stewart, and other recent explorers. Never- 
theless even of this region Mr. O’Donovan has much to 
tell us, which is both new and interesting. There is a 
freshness and a fulness of detail in his account of Meshed, 
Tehran, Kuchan, Resht, Siabrtd, as well as of the 
people and scenery of Khorasdn and Mazandaran, which 
lend a peculiar charm to the first of these brilliantly 
written volumes. 
But the chief interest of the work naturally centres in 
the section devoted to the Merv Oasis and its Tekke 
Turkoman inhabitants, with whom the traveller passed a 
forced residence for over five months during the year 
1881. How he eluded his Persian escort, crossed the 
border above Sarakhs, traversed the Tejend river valley, 
plunged boldly into the heart of the desert, safely reached 
the Murghab Oasis, allayed the suspicions of the Tekkés, 
who took him for a Russian spy, gradually gained their 
confidence, became in fact a “Tekke of the Tekkés” 
and head of a Turkoman triumvirate, finally, by a rare 
combination of tact, patience, and courage, again escaping 
from his too importunate frien’s, all reads far more like 
a wild piece of fiction than so much sober history. 
