REVIEWS 



Proceedings of the Coal Mining Institute of America. Thirty- third 

 Annual Meeting, Pittsburgh, Pennsylvania, December, 1919. 

 Pp. 158. 



In an article on the "Future Development of Fuels," Henry Koeis- 

 inger, fuel engineer. United States Bureau of Mines, discusses those 

 modes of coal consumption that utilize most fully the energy latent in 

 the fuel, namely by-product production of coke, the use of powdered 

 coal, and the use of so-called "colloidal fuel," a mixture of powdered 

 coal and fuel oil. Electrification of railroads and better combustion of 

 coal in the commoner methods of utilization come in for discussion. 



Pages 34 to 43 are devoted to an excellently illustrated article by 

 Reinhardt Thiessen of the United States Bureau of Mines, on the " Con- 

 stitution of Coal through a Microscope." 



Pages 89 to 10 1 are devoted to a paper by H. C. Ray, professor of 

 ore dressing at the University of Pittsburgh, on "Modern Practices in 

 the Washing of Coal," illustrated with nine text figures. 



E. S. B. 



Report on Some Sources of Helium in the British Empire. By 

 J. C. McLennan and Associates. Canada Department of 

 Mines, Mines Branch, Bulletin 31, 1920. Pp. 72. 

 Shortly after the commencement of the war, it became evident that, 

 if helium were available in sufficient quantities to replace hydrogen in 

 naval or military airships, the losses in life and equipment arising from 

 the use of hydrogen would be enormously lessened. Helium, as is 

 known, is most suitable as a filling for airship envelopes, in that it is 

 non-inflammable and non-explosive, and, if desired, the engines may be 

 placed within the envelope. By its use it is also possible to secure 

 additional buoyancy by heating the gas (electrically or otherwise), and 

 this fact might possibly lead to considerable modifications in the tech- 

 nique of airship maneuvers and navigation. The loss of gas from diffu- 

 sion through the envelope is also less with helium than with hydrogen, 

 but, on the other hand, the lifting power of helium is about 10 per cent 

 less than that of hydrogen. 



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