PROCEEDIKGS OF THE POLYTECHNIC ASSOCIATION, 661 



give double the power attainable without expansion. Hence, 

 theoretically, half the power will be lost. But this is expected 

 to be balanced by the inferior cost and more thorough use of 

 the fuel at the stations. Locomotives vaporize about 8 lbs, of 

 water with 1 lb. of the best coke ; but stationary engines vapo- 

 rize 12 lbs, with 1 lb. of fuel that costs less than two- thirds as 

 much. And when stops are frequent and long, there is a loss of 

 heat from steam but not from air ; and the fireman is not needed 

 for air. 



It has been stated that in compressing air the pumps become 

 red hot, unless cooled by water ; and that in working it, the ex- 

 pansion cools it so fast as to form ice on the cylinders and pipes; 

 and that a considerable percentage of power is thus lost. The 

 committee have no authentic data on this point ; but it is evident 

 that city cars that stop frequently are less liable to freezing than 

 those that run fast and steadily ; and that the low pressure prac- 

 ticable on short stages is less liable to such loss than the high 

 pressure necessary on long stages. 



The Committee, in view of all the evidence they have seen, 

 deem that, for short lines, air may be better than steam. It is 

 perfectly cleanly. It is likely to cost less ; but if it costs more, 

 it may still be advantageous to use it. 



Compared with horse-power, it is likely to be both cheaper and 

 more agreeable. A car propelled by air will make no dust ; but 

 the dirt made by horses is a costly nuisance. To maintain a 

 given standard of cleanliness in a city without horses, like Venice, 

 costs less than one-third as much as in New York for mere wash- 

 ing ; and the wear of clothing is nearly in proportion to the wash- 

 ing ; and if all wheels ran on iron, and by elemental power. New 

 York might be as cleanly as Venice ; and the saving of clothing, 

 furniture and goods would more than pay for all the cost of riding, 

 rails, pavements, and all else required for the streets. 



The cost of horses, compared with steam, is much greater than 

 people suppose, especially at high speed. The English coaches 

 used to cost 36 cents per mile for the horses, to draw 15 passen- 

 gers at eight miles per hour. Locomotives cost 12 cents per 

 mile, and can draw 300 passengers at 40 miles per hour. On the 

 New York Central locomotives cost 20 to 22 cents per mile, burn- 

 ing wood ; on the Baltimore and Ohio, 15 cents per mile with 

 coal; and some of the best engines, with 16-inch cylinders, on a 

 southern road, have worked for 12 cents per mile. The wages, 



