412 . REVIEWS 



Early in 191 5 Dr. J. C. McLennan, head of the department of 

 physics in Ontario University, was requested by the Board of Invention 

 and Research, London, England, to investigate the helium content in 

 various natural gas supplies within the British Empire. As a result of 

 these investigations it has been shown that the largest source of supply 

 of helium at present known within the empire is located in Canada. 

 Commercial methods of separating helium from the other components 

 of natural gas were developed as a result of the preliminary investiga- 

 tions, and considerable progress was made toward the development of 

 methods for the production of helium on a commercial scale, as a result 

 of which it was shown that helium could be produced at a cost of some- 

 what less than $0.25 per cubic foot at normal pressures and temperatures. 



As a result of a large number of analyses, which are given in this 

 report, it was found that the richest natural gases in Canada contained 

 about 0.33 per cent of helium — a percentage believed to be sufficient 

 for profitable commercial extraction, but considerably lower than the 

 percentages which characterize the gases from a number of wells in 

 Kansas, where the helium content ranges from 1.5 to 2 per cent. Analy- 

 ses are given of natural gases from Ontario, Alberta, and British 

 Columbia. 



As a supplemental investigation, a study was made of the radio- 

 activity of a number of these gases. It was found that when the gases 

 escape from the well they usually contain the emanations of radium 

 and thorium. The thorium emanations are very short-lived, but the 

 decadence in the radium emanations is much slower. Measurements of 

 the radioactivity of a number of gases were made, the method used 

 involving the deduction of the amount of radium emanation from 

 measurements of the increase in electrical conductivity which the 

 presence of radium emanations imparts to the gas. 



E. S. B 



Potash Recovery at Cement Plants. By Alfred W. G. Wilson. 



Canada Department of Mines, Mines Branch, Bulletin 29, 



1909. Pp. 34, pis. 10. 



Considerable interest was awakened during the war by the cessation 



of potash imports from Germany in all possible substitute sources in the 



United States and Canada. The report under review is the outcome of 



investigations started then by the Canadian War Trade Board. 



The wisdom of peace-time development of our slender resources of 

 potash-bearing brines may be challenged. Much might be said in 



