354 The American Geologist. May, iwu 
through the Coal Measures there are certain definite stratigraphic hori- 
zons along which bituminous matter was deposited abundantly, making 
a certain sel of conditions prevalent over a considerable area. The dis- 
tribution of the coal was, however, dependent entirely upon the local 
conditions, which determined whether at any point a single thick seam. 
several thin seams, bituminous shales or even non-bituminous matter, 
should be deposited. This throws considerable lighl on the real condi- 
tions existing at the time of the local formation, and lias also a very 
direct value to the prospector as guiding him in his search. 
In connection with the report is a geological map of the state, which 
shows noteworthy 'advance over that published the previous year. 
There is more detail in tracing formation boundaries: the eastern bor- 
der of the Coal Measures is more sharply defined; and the < 'retaceous is 
made to extend over a considerable stretch of new territory in the 
southwest. 
A short chapter is given on the origin of coal. The various theories 
advanced are summarized, and the knowledge up to date is given. A 
chapter on the composition of Iowa coals contains notes on their physi- 
cal properties and the results of nearly 150 chemical analyses. The 
question of waste in coal mining is briefly touched, and the various 
methods of utilizing tine coal are discussed. The extent and growth of 
the industry in Iowa is shown by various tables and maps so arranged 
as to bring to the eye at once a considerable mass of information: and 
the rapid growth of the industry, as stated by these tables, makes a 
good showing for the state. H. F. B. 
Revolution in tin Topography of the Pacific Coast ttinc< thi Auriferous 
Gravel period. By .1. S. Dialer. Journal of Geology, vol. it. pp. '.'>'l-7>\. 
Jan. -Feb., 1894. During the Pliocene and Pleistocene periods, accord- 
ing tothe studies of Mr. Diller, Prof. Le Conte, Mr. W. Lindgren, and 
others, the region of the Sierra Nevada, which previously had been re- 
duced by erosion to a low altitude, approaching a baselevel, has under- 
gone ver> great, but gradual orogenic changes, with extensive outpouring 
of lavas. The northern end of the Sierra has been raised "at least 1,000 
feet, and possibly as much as 7,000 feet. - ' while a fault of more t ban 3,000 
feet has been developed along t he eastern face of this highest and grand- 
est mountain ranee m the United Slates. The approximately base- 
levelled old plain now forms the long western slope, which, descending 
gently to the Sacramento and San Joaquin valley, has become deeply 
furrowed with canons b\ the rejuvenated streams. The auriferous 
river gravels, varying from 50 to 500 feet in thickness, were mostly de- 
posited during the initial part of this revolution; and the source of their 
material was the thick deposits of residuary. detritus which had accu- 
mulated upon the surface of the laud during the baselevel period, 
Elementary Meteorology. By William Morris Davis. Professor of 
Physical Geography in Harvard ( !ollege. 8vo, pp. xii. •!•">■">. with six plates 
(charts of the world, showing isotherms and isobars), and 106 figures in 
the text. Boston: Ginn & Co.. 1894. This very thorough, well arranged 
