640 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



to seat 25 or 30 passengers, weighing but three tons, it will not be 

 difficult to imagine how little of its area might have been devoted 

 to the purpose of holding a receiver ; now as to size of other 

 parts of the machine, and barren as the account is in details, it 

 is still sufficient to prove that " no inconveniently large receiver 

 or cylinders " were required or employed to accomplish the results 

 attained; and enough is gleaned from the "Artisan," in treating 

 of Von Rathen's patent, to show not only that he used the air 

 expansively, but, also, that he applied it to the working cylin- 

 ders through the medium of a regulating valve or separate regu- 

 lating cylinders ; for that paper speaks of " a method," without 

 particularly describing it, by which the Baron effected "the regu- 

 lation of the degree of working pressure by an ingenions contri- 

 vance, so as to be uniform, by the operation of a self-regulator, 

 susceptible of being increased or diminished if required." 



I will now turn to the particular views and experiments of Mr. 

 Parsey, as set forth by himself in an article contained in the 

 London Mechanics' Journal.* He says: — 



" Though the possibility is popularly entertained, like the quad- 

 rature of the circle and perpetual motion in science, the practi- 

 cability of compressed air power has been given up by the gene- 

 rality of engineers as unattainable. Steam having gained the 

 ascendancy and command over the working of railroads, a change 

 from a system so well understood for a repudiated practice 

 scarcely comprehended, is not desired by the established and 

 flourishing steam interests, which, as in all former instances, are 

 opposed to the adoption and progress of improvements supposed 

 to affect them. 



" The known power of compressed air has not hitherto been 

 brought into use on account of the difficulty of controlling it at 

 high densities, and of working it with a continuity, as well as a 

 uniformity of pressure on the piston." 



" That fatality," as he calls it, he deems "to be now perfectly 

 overcome " by means of his patent engine. 



His experimental engine weighed 1^ tons ; capacity of receiver 

 39 cubic feet; pistons 2^ inches diameter; 9 inches stroke; driv- 

 ing wheels 4 feet. 



" This engine was filled at the Stratford workshop by a small 

 pump of 2^ inch plunger, 6 inch stroke, to a pressure of 165 lbs. 

 per square inch, when it was placed for the fii'st time on a rail." 



* Praotioal Mechanics' Journal, London, 1852-3, p. 288. 



