PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 685 



sulphide of carbon. It thus states its advantages : " The transformation 

 of the India-rubber is done in a few minutes, and the product possesses 

 beside the known qualities of vulcanized rubber, a lighter color whereby it 

 is more apt for a reception of colors than the common vulcanized rubber, 

 which must first receive a lighter shade by adding white substances, such 

 as the oxide of zinc and the like." . 



The Chairman directed attention again to statements regarding the 

 improvement of iron and steel. Our vast melting operations having given 

 tlie subject additional interest. 



Mr. Dibben remarked that this Association was the first to draw public 

 attention to the fact that our common iron was greatly improved in 

 quality by the admixture of a small quantity of Frauklinite which contains 

 manganese. The demand for the New Jersey Franklinite has greatly 

 increased, and orders for it have been received from Europe. Eight out 

 of ten of all the chilled car- wheels used in this country are made by this 

 process. 



Mr. Wiard stated that he had melted 1,200 lbs. of Springfield iron with 

 100 lbs. of Franklinite iron and found that the tensile strength was 36,000 

 lbs. 



The use of Compressed air as a Motor. 



The discussion was opened by Mr. Root, who alluded to the manner in 

 which air had been compressed by heat and used in the Caloric engine, and 

 to several cases when it had been compressed by force and thus used for 

 transmitting power. He adverted to the fact that air, like all gases emits 

 heat on compression, and absorbs it on expansion. The manner in which 

 the vapor of water and air unite and separate in the sky had suggested to 

 him the use of an engine, which he then described by the aid of a diagram 

 on the blackboard. 



Messrs. Dibbeu and Bartlett explained its impracticability. 



The Chairman remarked that within the last ten years more novel motors 

 have been tried in this country than any other. No one should now enter 

 this field without having first carefully studied the elements of caloric 

 engines, Mt. Storms' Cloud Engine, Drake's Ignition Gas Engine, Blanch- 

 ard's Steam and Gas Engines, and Hughes's Bi-Sulphide of Carbon Engine. 

 It would, however, be interesting to examine air as a secondary motor ; 

 and in this connection, the plan of Richardson, of Boston, for carrying let- 

 ters and small packages through tubes by pneumatic power, which is now 

 said to be in successful operation in London. 



Thereupon Mr. Garvey, the Secretary, read from the London Mechanics' 

 Magazine a full description of that method, and added that he had been 

 upon the atmospheric railways formerly in use to a very limited extent in 

 Ireland and England. The reason for their entire failure was the difficulty 

 experienced in keeping the apparatus air-tight, and the increased cost of 

 carrying passengers. The locomotive has taken the place of the pneumatic 

 engine on these roads. He also alluded to a successful use of air as a 

 medium of power in the tunnel now being constructed under the Alps. 

 The prime mover was the waterfall on the mountain side, and the air com- 

 pressed was liberated in such manner as to ventilate the tunnel at the same 

 time it performed the duty of drilling. 



