PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 639 



The Baron Von Rathen is spoken of by the London Scientific 

 Journals as " a veteran supporter of the doctrine of the utility 

 of compressed air as a source of power." He is not only the in- 

 ventor of an air carriage, and his improvements refer to the 

 compression of air and the expansion and regulation of it when 

 used as a propelling power; but, also, of a new description of 

 hydraulic pump for compressing and cooling air. The " London 

 Artizan," after a full examination of his invention and specifica- 

 tions, remarks, " that precautions have been taken therein for 

 the avoidance of the loss of power in compressing and expand- 

 ing air, which has hitherto excluded compressed air from being 

 usefully employed as a propelling power — a power," it adds, "of- 

 fering such great advantages as regards safety and comfort." 



The London Mining Journal is referred to by the Scientific 

 American, (Scientific American, vol. iv. No. 11, Dec. 2, 1848, p. 

 82,) as authority for saying that a third trial had been made for 

 testing the capabilities of the Baron's compressed air locomo- 

 tive on the common highway, for working the air expansively, 

 and which operated well, although one or two leaks subtracted 

 somewhat from the real power. As it was, however, the carriage 

 weighing three tons and carrying from 25 to 30 passengers, 

 started in good style and kept pace with former experiments as 

 to time and distance ; the motion was regular, and the machinery- 

 stood well, the only casualty being the leakings. That the pa- 

 tentee considers he has now completely solved the problem of 

 the practicability of employing compressed air in locomotion, 

 and regulating it as to distance, speed, load, nature of road, &c., 

 on which, in the greater or less perfection in the construction of 

 the machinery, its success, of course, depends. That he is pre- 

 pared to show, to mathematical demonstration, that he can em- 

 body sufficient power in his model air carriage to convey 4^ tons, 

 including carriage, ten miles in one hour on common roads, or a 

 train of 45 tons in the same time, the same distance, on a rail- 

 road ; and that if carried out on a large scale on the latter, he 

 contends that the system would effect a saving of 75 per cent, 

 over the steam locomotive. 



It is to be regretted that the mere result only of this experi- 

 ment is given, without many of the important details as to dimen- 

 sions of carriage, receiver, engine and cylinder. I have not been 

 able to obtain the Journal referred to by the Scientific American. 

 But, with a carriage designed to traverse common highways, and 



