048 =I. C. Russell—Subaérial Deposits of North America. 
IJ.—Comparison OF THE ADOBE WITH THE LOESS OF CHINA. 
It is of interest to compare the adobe of the Arid Region wit 
similar accumulations elsewhere, and especially with the loess of 
China, which has been very fully described by F. Von Richthofen.! 
In China there are many basins comparable with those in the 
more arid portion of the United States, which are deeply filled with 
a yellow marly-clay of impalpable fineness termed Loess, which is 
without stratification, breaks most readily in a vertical direction, 
and stands in perpendicular escarpments for many years. It is 
traversed by vertical tubes of small dimensions which bifurcate 
downward; is charged with land-shells, and contains the bones of 
land-mammals. In all of these particulars the loess of China agrees 
with the adobe of the Arid Region. The loess is described as being 
uniformly yellow in colour, and, as we have previously stated, this 
is the characteristic colour of the vast subaérial deposit of the Arid 
Region, except when charged with organic matter. 
In China certain peculiar concretions occur in the loess, figures of 
which are given by Richthofen ;? these, so far as known, are not 
represented in the adobe. 
A portion of the loess of China, termed “lake loess,” has been 
described as being a stratified deposit formed in saline lakes. These 
beds are practically identical with the playa deposits of the Arid 
Region, except that a more marked stratification has been observed 
in them. In each country these deposits are composed of fine, light 
yellow earth, more or less saline, and sometimes carry salts of 
various kinds in sufficient quantities to be of commercial value. 
The loess of China has been shown by Richthofen to have a 
thickness of fully 2000-2500 feet. There is a lack of accurate data 
by which to determine the thickness of the similar deposits in 
America, but observations based on the contours of valleys and on 
the records of the few wells that have been bored, indicate, as 
already stated, that in many instances it is fully as thick as the loess. 
In China the peculiar property of the loess, which admits of its 
standing in vertical escarpments, is utilized by the inhabitants, who 
excavate houses in the faces of the bluffs. In America the same 
property in the adobe admits of the formation of sun-dried bricks, 
which have been used in the construction of thousands of houses, 
and in many instances of entire towns. In each country the deposits 
mentioned form exceedingly rich agricultural lands. 
The loess is described as being porous, so that rain falling on 
it is rapidly absorbed. This property is shared in part by the adobe, 
but is not a characteristic feature of the deposit in general. On the 
alluvial cones and in the higher portions of the adobe-filled basins 
of the Arid Region, the rain-water rapidly disappears by percolation, 
but in other instances, and especially in the playas, the earth is 
extremely impervious. Only a foot or two beneath the playa lakes 
1 China, Berlin, 1877, vol. i. pp. 56-189. See also abstract in Am. Jour. Sci. 8rd 
series, 1877, vol. xiv. pp. 487-491. 
* China, vol. i. p. 58. 
