REVIEWS 413 



favor of allowing such reserves to remain in the ground pending the 

 next national emergency. But the recovery of potash as a by-product 

 of cement manufacture and from iron-blast-furnace dust is utilization 

 of raw material and of heat energy that otherwise would be wasted and 

 should command the support of all conservationists. Such processes 

 have the added advantage of minimizing the dust nuisance around 

 cement plants, which is a danger to the health of employees and is detri- 

 mental to crops in agricultural districts. It has been estimated that in 

 the United States, if all cement plants were equipped to recover potash 

 salts, potash equivalent to over one-fourth of our normal imports of 

 German potash salts could be recovered. 



The report under review outlines briefly the principles underlying 

 the recovery processes and describes in outline the equipments at all the 

 plants in the United States and Canada where potash recovery has thus 

 far been practiced. At the temperatures of 1,400 to 1,500° C. obtained 

 in cement kilns, the potash-bearing silicates are in part decomposed, 

 potash reuniting usually with the sulphate radical to form potassium 

 sulphate, or to a lesser extent with the chloride radical to form potassium 

 chloride — salts which are soluble and which pass into the stacks with 

 the gases, where they can be recovered by spraying the gases or precipi- 

 tating the dust by the Cottrell electrical process. The quantity of 

 potash salts produced varies from 2 to 7 pounds per barrel of Portland 

 cement. 



Installation of potash-recovery equipment does not involve any 

 changes in the processes of cement manufacture, nor does it affect the 

 grade of the cement produced. 



The report closes with a complete bibliography. 



E. S. B. 



Timiskaming County, Quebec. By M. E. Wilson. Canadian 

 Geological Survey, Memoir 103, Ottawa, 1918. Pp. 197, pis. 

 XVI, figs. 6, map. 



This is a concise, detailed report of the results and conclusions of 

 geological field work carried on for a number of years in Timiskaming 

 County, together with a theoretical discussion of some of the more 

 important problems of the area. 



Timiskaming County has an area of approximately 20,000 square miles 

 and lies on the east side of the boundary line between Ontario and Quebec 

 and east and northeast of Lake Timiskaming. The National Trans- 



