PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 659 



falls below the upper passage, a bubble of air enters and an equal 

 quantity of ink enters the bowl through the lower passage, keep- 

 ing the bowl always supplied at a uniform hight. 



COMPRESSED AIR FOR RAILROADS. 



Mr. Fisher, from the committee on Carson's plan of propelling 

 cars by compressed air, made the following report thereon : 



The committee to whom was referred Mr. Carson's plan of 

 a street rail car to be propelled by compressed air, have exam- 

 ined the plan so far as it is developed, and have examined re- 

 ports of experiments that have preceded Mr. Carson's plans, and 

 respectfully report as follows : 



In 1799, a patent was granted in England to Mr. Medhurst, for 

 propelling machinery by compressed air. In 1819, Mr. Murdoch, 

 of Soho, and Mr. David Cordon, made calculations and experi- 

 ments with a view to propel carriages by compressed air ; but 

 were discouraged by the- difficulties of compression, which was 

 then not well understood. In 1828, Mr. Lemuel Wright, an 

 American resident in England, patented a plan, and built an air 

 carriage; and a Mr. Morin, in 1829, patented a plan for an air 

 carriage. Mr, Alexander Gordon, in his Treatise on Elemental 

 Locomotion, in 1834, gives his opinion that there was then no 

 plan of air propulsion that could safely be engaged in as a specu- 

 lation. Since that time there have been trials in France on rail- 

 ways and common roads ; but although they have been favorably 

 noticed in newspapers, no permanent results have followed them. 



The most successful trials of which there are authentic ac- 

 counts, are those of Arthur Parsey and the Baron Von Rathen, 

 in England, about 12 years ago. Parsey worked on a railway, 

 and attained a speed of 20 miles per hour with a small and im- 

 perfect engine, under a pressure of 160 lbs., 200 lbs. being the 

 limits prescribed to him, which is too low for practice. Von 

 Rathen worked with 800 lbs, in his receiver on a common road, 

 and arrived at the conclusion that he could run five miles on a 

 turnpike, or forty miles on a railway, with one charge. Parsey 

 thought that twenty miles was the useful limit for a charge. 



So far as appears, both these estimates are mere opinions, and 

 not based on the high rate of speed demanded on railways, which 

 increases the resistance to nearly double that of the speed at- 

 tained by Parsey. 



A first class express train consumes five tons of water in a 



