644 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



" 3d. A reduction of three-fourths of the present expense for 

 repairs, as air engines will not be exposed to the destructive 

 effects of intense heat and steam. 



" 4th. A vast saving from increased durability in the ratio of 

 fifty to one ; as air reservoirs will last one hundred years or mOre, 

 and the fair wear and tear will only be on the frames, wheels, 

 Bprings, &c. 



" 5th. A saving of one-third on fuel, by using coal at compres- 

 sing stations, instead of coke in locomotives. 



" 6th. A total saving of water, as air engines carry none. 



" 7th. At present, cleaning and washing out of steam locomo- 

 tives is a heavy expense, which may be reduced three-fourths, as 

 air engines will only want outside cleaning, which can princi- 

 pally be performed by the driver and his mate. 



" 8th. As the nature and extent of repairs will be very differ- 

 ent, and so much less than steamers, workshop expenses may be 

 reduced on a ratio with the economy of the above items, so that 

 it must be evident the savings on prime cost, repairs and work- 

 ing expenses of the steam locomotive account may be reduced 

 one-half." 



To which may be added, 9th and last, what Mr. Parsey seems 

 to have overlooked, an immense saving in construction account, 

 growing out of the excessive weight of steam locomotives with 

 their tenders and material, together varying from twenty to forty 

 tons. To provide a bearing surface capable of enduring and 

 withstanding the crushing, grinding and splintering force, against 

 the constant hammer and abrasion of such a superincumbent 

 weight rolling over it, must, of necessity, very greatly increase 

 the cost of constructing roads. 



In the absence of all necessity for attention to the fires in gen- 

 erating steam power, under all the fluctuations of wind and wea- 

 ther, the working of an engine with compressed air is wonder- 

 fully simplified ; and, as the temperatures of excessive heat, with 

 all the difficulties of ascertaining and calculating them and their 

 effects, are removed, and nothing but natural temperatures hav- 

 ing to be dealt with, the advantages of compressed air power 

 need not to be dwelt upon. 



" The strength of air reservoirs, making them securely air-tight 

 at high densities, and the pressures they are capable of sustain- 

 ing for the want of practical experience, are very little under- 

 stood 5 one hundred pounds per square inch is thought consider- 



