MFX'HANICS AND USEFUL ARTS. 71 



taken away. From this point the boilers were fired afresh, and 

 fed with weighed fuel ; the man-holes, hitherto kept closed, were 

 now opened to let the steam escape ; and the firing was so well 

 regulated, by means of dampers, that the velocity of the escaping 

 steam was the same in each boiler. The temperature of the gases 

 from the fire was measured, at a point G feet from the rear end of 

 each boiler, and found to vary from 644^ to 734° F. 



" After consuming on each grate 3, 150 pounds of coal of the same 

 quality, the cinders of which were burned over and over again, 

 the fires were put out, and the man-holes closed. On the follow- 

 ing day the remaining water of the boilers, showing a tempera- 

 ture of 95°, was let on through the emptying tube, situated at the 

 lowest part of the boiler, and measured by means of a hydrometer 

 adapted to the tube. The iron boiler showed 387 cubic feet, and 

 the steel boiler 331 cubic feet of the remaining feed water. There- 

 fore the water evaporated in the iron boiler was 712 — 387 = 325 

 cubic feet, or 20,065 pounds; and that evaporated in the steel 

 boiler was 712 — 331 = 381 cubic feet, or 23,523 pounds. Hence 

 the evaporating capacity was proved to be 17.20 percent, in favor 

 of the steel boiler. One pound of coal evaporated in the iron 

 boiler 6,350 pounds of water, and the steel boiler 7,467 pounds 

 of water at 212° F. At the next trial the whole operation was 

 performed in the same manner, only the velocity of the escaping 

 steam was less. It resulted in showing 19.62 per cent, in favor 

 of the steel boiler. One pound of coal evaporated in the iron 

 boiler 5,809 pounds, and in the steel boiler 7,008 pounds of water. 



*' These two experiments wore verified in the following man- 

 ner: To an equal quantity of feed water in each boiler an equal 

 volume of a strong solution of salt was added. After stirring 

 the water for some time, by means of long poles, and boiling it 

 with closed man-holes, samples were taken out for future analysis. 

 In completing this experiment, in which equal quantities of fuel 

 and water w^ere used, further samples were taken out. The anal- 

 3'si5 of the samples b}' Dr. List, of Ilagan, showed that in the 

 iron boiler 1 quart of water contained 'oefore evaporation 4,629 

 grammes of chloride of sodium, and after, 5,985 ; in the steel 

 boiler 1 quart contained 4,371 grammes before, and 7,385 grammes 

 of salt after evaporation ; the iron boiler lost 33.76 quarts, and 

 the steel boiler 40.81 quarts of water, showing 20.85 per cent, in 

 favor of the latter. The average percentage of these three ex- 

 periments is 19.24 per cent, in favor of the steel boiler, which it 

 will be noted had a shell 83 per cent, thinner than that of the 

 w^rought-iron boiler." 



o 



bailey's steam engine. 



The essential requisites in a steam engine are now lightness, 

 strength, compactness, and simplicity, so that it will occupy little 

 space, be easily transported, and be readily put up and operated by 

 engineers of ordinary capacity; the working parts should be few 

 and durable, and protected from dust and dirt. In Bailey's engine 



