5IO REVIEWS 



his former associates at the passing of a geologist of such brilliancy and 

 promise. The report perpetuates one of Mr. Rogers' contributions to 

 the war needs of his country, namely the investigation of the occurrences 

 of helium-bearing natural gas in the United States with a view to its 

 utilization in dirigibles and military balloons. 



Helium differs from hydrogen, the gas commonly used in balloons, 

 in being non-inflammable; on the other hand it is about twice as heavy as 

 hydrogen though still so much lighter than air that its lifting-power in 

 air is 93 per cent that of hydrogen. Its advantages are so great that 

 its use, both commercial and miHtary, in airships is likely to be limited 

 solely by the supply of helium available and the expense at which it can 

 be produced. 



The main body of this report is devoted to a description of the field 

 occurrence of natural gases containing helium within the limits of the 

 United States, but a brief discussion of possible sources of helium in 

 other countries is included, and the report summarizes also, in very 

 concrete and admirable fashion, the history of helium, its properties, 

 and its relations to the radioactive elements, as well as the methods 

 which have been applied for separating it from the commoner constituents 

 of natural gases. The field work upon which the investigation rests 

 consisted chiefly in collecting samples of gas for analysis and in gathering 

 data regarding depth, geologic position, rock pressure, and volume of 

 the gas sampled. This work involved careful examination of the 

 geological structure in one or two areas, though a number of helium-rich 

 districts had been previously studied by Survey geologists, and data on 

 others were furnished by oil companies. 



As a result of the investigations it is shown that although most of 

 the natural gas produced in the eastern and central parts of the United 

 States contains at least a trace of heUum, gas containing more than | 

 per cent is known to occur only in two areas, one in northern Texas and 

 the other in southern Kansas and northern Oklahoma. The helium-rich 

 gas of the Kansas-Oklahoma area is confined to strata of Middle and 

 Upper Pennsylvanian age, though gas carrying almost f per cent of 

 helium occurs in the Lower Pennsylvanian. The Mississippian and 

 Permian gases in that locality are poor in helium. Conditions in the 

 Texas area are almost identical. In Ohio gas carrying ^ per cent of 

 helium occurs in the Lower Mississippian and in the Clinton of the 

 Silurian. Nearly all samples of Cretaceous gas from various parts of 

 the United States show only traces of helium and most samples of 

 Tertiary gas contain none. 



