264 REVIEWS 



porphyry, and the cinnabar, which is the chief sulphide in the ore, lies 

 in part in chalcedonic silica, and in part in friable marble adjoining such 

 silica. Some pyrite is present with the cinnabar in most of the deposits. 

 Stibnite is present in the district, in association with cinnabar, but was 

 not observed in any of the workable deposits. 



Cinnabar was discovered in this district in 1902, and prospecting 

 has been active since that time. In 191 7 active development on a small 

 scale was in progress. E. S. B. 



Coal in igi8. Part A: Production. ■ By C. E. Lesher. "Mineral 



Resources of the United States, 1918," Part II. Washington: 



U.S. Geological Survey. 118 pp. 1920. 



A noteworthy feature of this report, as contrasted with reports for 



preceding years, is the detailed statistical study, by states and for the 



United States, of the causes of loss of time in the coal-mining industry. 



In a series of instructive diagrams for the United States and for each 



state, the percentage of time lost on account of (a) car shortage, {h) labor 



shortage and strikes, (c) mine disability, id) lack of market are separately 



shown. These statistical studies are timely because they throw light 



upon the causes of the industrial troubles which have vexed the coal 



industry in recent years. E. S. B. 



Some Principles Governing the Production of Oil Wells. By Carl H. 

 Beal and J. O. Lewis. Bureau of Mines, Bull. No. 194, 

 Petroleum Technology 61, 192 1. 



We are constantly reminded that the resources of petroleum in the 

 United States are diminishing at an alarming rate. The fact that more 

 oil was produced in the United States during the month of March, 192 1, 

 than during any previous month suggests that eflforts to curtail pro- 

 duction are futile. One of the best remedies for this situation is to make 

 the most of what we have. In this we have been very successful through 

 the Bureau of Mines. 



Mr. Carl H. Beal and Mr. J. O. Lewis, the authors of this new publica- 

 tion, were among the first to make intensive studies of underground con- 

 ditions in oil fields, so that the maximum production might be obtained 

 from oil wells. The results have been gratifying and have more than 

 paid for the cost of investigations. 



The bulletin is a summary of all the known factors controlling the 

 production of oil, and contains some of the theoretical aspects of oil 

 production. It is of inestimable value to operators and "resident 

 geologists." W. O. G. 



