REVIEWS ■ . 631 



The book is of great value to the state for its clear exposition of the 

 elemental factors entering into the artesian conditions of Iowa, for its 

 appeal to the people to pursue intelligent methods in obtaining their 

 water-supply, and for its emphasis on the increasing necessity of secur- 

 ing drinking-water free from organic matter. This creditable volume 

 was planned during the regime of the late state geologist, Samuel Calvin, 

 and completed under his successor, G. F, Kay. The work was carried 

 on by the State Survey in co-operation with the United States Geologi- 

 cal Survey. 



M. M. Leighton 



The Coal Deposits of Missouri. By Henry Hinds. Missouri 

 Geological Survey, Vol. XI, 2d Series, pp. 503; pis. 23; figs. 97; 

 maps 7. 



The present volume which is the result of co-operation between the 

 Missouri Geological Survey and the U.S. Geological Survey, concerns 

 itself with an economic discussion of the coals of Missouri. Quite 

 properly, a mere outline of the stratigraphy is given and the deeper 

 scientific problems are to be presented in a later report. 



The arrangement of the volume is admirable. A short general dis- 

 cussion of the stratigraphy and structure is followed by a chapter on the 

 mode of occurrence of the coals and a description of the different beds 

 and fields. Statistics are presented showing production for various 

 periods. The detailed report by counties arranged alphabetically, is a 

 very desirable feature. Most of the letters of inquiry received by state 

 surveys refer to counties, and it is thought that the grouping of detailed 

 information into county units best meets the needs of the average reader. 



Separate chapters are devoted to the quality and efficiency of the 

 coals. In general, the fixed carbon and heat value decrease gradually 

 across the state from south to north and west, the best coals occurring 

 where the Ozark uplift had its greatest devolatilizing effect. Unfortu- 

 nately, in the chapter on chemical analysis, it is not always clear whether 

 figures given represent values "as received," "air-dried," or "moisture- 

 free." In the tabulated analyses, emphasis is placed on "air-dried" 

 values, whereas most engineers and consumers now compare coals either 

 "as received" or on the " moisture- free " basis. On the latter basis, the 

 coals of the entire state contain an average of 12,363 B.t.u. Tabulated 

 results of tests on steaming, under boiler, for producer gas, on washed 

 coal, and on coking and briquetting are presented in the final chapter. 



