L. MECHANICS AND ENGINEERING. 471 



long, suitable for heating boilers, etc., and the experiments, 

 as far as they go, indicate a heating power in the cinders 

 (from which the larger pieces of slag have simply been sepa- 

 rated by hand) equal to that of half their weight of coal. A 

 convenient method of separating the slag seems to be the 

 great desideratum. Washing the cinders requires too much 

 room for drying, and even then they will retain considerable 

 moisture. A current of air, as employed in winnowing grain, 

 has been suggested. 14 C, CCIX., 236. 



PURIFICATION OF HARD WATER FOR STEAM-BOILERS, ETC. 



After a full discussion of the various methods for purifying 

 hard water for feeding boilers and manufacturing purposes, 

 Stingl concludes that the only trustworthy method is that 

 of precipitating the impurities by the proper quantity of a 

 suitable chemical agent or agents, and removing the precip- 

 itates in an approved way. The defects in the previous ap- 

 plications of this method have been so far removed by Be- 

 ranger, in his patented process, that it is used with success in 

 a number of establishments. Omitting the detailed working 

 description of the complete but simple apparatus employed, 

 the main features seem to be the precipitation of the foreign 

 matters by lime-water, or lime-water and chloride of barium 

 (the requisite quantity of these substances to be accurately 

 ascertained by volumetric analysis of the water), using for 

 the purpose standard lime-water instead of soap solution, as 

 in previous processes. During the progress of the purifica- 

 tion, the least excess or deficiency of lime-water can be de- 

 tected by accurate and easy tests, and can be remedied, thus 

 keeping the operation completely under control. The water is 

 finally passed through a very simple, efficient, and cheap filter 

 of shavings and refuse coke, which not only delivers it clear, 

 but remains effective for several months. 14 (7, CCIX., 175. 



FUEL BURNING WITHOUT SMOKE (PYROLITIl). 



A fuel burning without smoke, needing no attention after 

 lighting, and said to be especially adapted to heating railway 

 cars, has been patented in England. It consists of a mixture 

 of pulverized charcoal or coal with some material affording 

 oxygen when heated, as nitrate or chlorate of potash, etc. 

 Some cementing substance, such as gum, starch, or water- 



