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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 
