PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 481 



out of fifty, whereas it would use up thirty squares out of the sixty-eight 

 gained by expansion. 



Again, one foot of steam, at 100 pounds total pressure by expansion, 

 falls short of four feet by twelve per cent. That is, there is not enough 

 vapor of water in one foot of steam, at 100 pounds total pressure, to 

 make four feet of steam at a pressure of twenty-five pounds. In order to 

 realize the benefits of expansion, according to Mr. Bonnie's theory, the 

 cylinder and all parts of the engine, has to be made three or four times 

 larger, and as all engines require a space between the piston and cylinder 

 head, and also a steam passage at the cylinder head, which are denomi- 

 nated port and clearance, and in the North river steamboat engines that 

 use puppet valves, the average of port and clearance is nearly ten per 

 cent. Now, the larger the cylinder the greater is the amount of steam 

 rendered ineffective in these passages. 



Mr. D. K. Clark, the most accurate experimenter in regard to the use of 

 steam expansively, in his work, Tiie Physiology of the Locomotive, says 

 that when a locomotive allows the steam to follow the piston three-quarters 

 of the stroke, there is ten per cent, of water fed into the boiler unaccounted 

 for by the volume of steam in the cjdinder, as shown by indicator cards, 

 and -when the steam follows the piston only one-quarter of the stroke, there 

 is thirty-five per cent, of feed water unaccounted for. In the expansion 

 experiments at Erie, by order of the United States government, the amount 

 of water unaccounted for by the indicator is forty per cent., when they 

 were cutting off at one-quarter of the stroke. If we take the quantity of 

 water unaccounted for b^^ the indicator, and add it to the foregoing losses, 

 it accounts for the failure to realize the slightest benefits by the use of 

 steam expansively. 



The want of any gain is clearly shown by the report of the Brooklyn 

 pumping engines, used at the water works in that city, the report of 

 which I have in my hands. The engine was made by Woodward & Beach 

 of Hartford, Connecticut. They constructed some years since an engine 

 for the Hartford water works, in which they attempted to cut off at one- 

 eighth of the stroke, using steam at thirty-five pounds boiler pressure, and 

 the}'' were only able to raise forty millions of pounds of water one foot 

 high with 100 pounds of coal. Whereas, in the Brooklyn engine, made by 

 the same firm, by some unfortunate calculation in the construction of the 

 engine, they were obliged to cut ofl^ at six-tenths of the stroke, and using 

 a boiler pressure of only ten pounds, they were enabled to raise sixty 

 million pounds of water one foot high with 100 pounds of coal, doing fifty 

 per cent, more work with the same amount of fuel, by cutting off at six- 

 tenths instead of one-eighth of the stroke, as the Hartford engine does, so 

 that, notwithstanding Mr. Bourne's notorious effects gained by expansion, 

 there is not on record one single fairly tried experiment which shows that 

 there was anything made by the use of steam expansively, or by using 

 any of those contrivances denominated variable, adjustable, automatic, 

 gravitating expansion gear. 



The following is a diagram showing a cylinder divided in its length 

 n twenty, and its diameter into ten equal parts: 



[Am. Ins.] 31 



