PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 629 



hundred experiments for the^^ purpose of ascertaining the best mode of 

 abstracting the metal. A feasible plan was to blow the cinders into the 

 furnace along with the air-blasts. By this method, he obtained fifty per 

 cent of the iron in them. 



Mr. Bartlett described the process for making steel tubes by means 

 of dies, as practiced in France. An interesting feature is the welding of 

 cold steel; one tube is drawn upon another; so perfect is the welding that 

 there is no way of seeing it, except b}'- using acids. 



Mr. Fleury spoke of the importance of coating the face of the rail, used 

 in railroads, with steel, by changing the molecular arrangement of that 

 part of the iron; this adds vastly ^o its durability. 



Mr. Justice of Philadelphia doubted the practicability of this plan, on 

 account of the great difference in the expansibility of iron and steel. The 

 whole variation in temperature, from the coldest point in winter to the 

 hottest in summer, is not far from 120 degrees Fah. Some iron rails have 

 been said not to last over six months, but these were near stations where 

 the trains were stopped many times a day, causing a very great increase 

 of friction, and the rails were more used in the changes of these points. 

 He stated that a plan for "steeling" rails was now being carried out at 

 Pittsburgh, Pa. 



After selecting as the subject for the next discussion: "The best means 

 of rapid transit through the City of New York," the Association adjourned. 



American Institute Polytechnic Association, ) 

 Ajyril 7, 1864. [ 



Chairman, Prof. S. D. Tillman; Secretary, Mr. B. Garvey. 



Perception of Musical Sounds. 



Dr. Rowell took the floor for the purpose of illustrating by a few experi- 

 ments the statement made at the last meeting with regard to the vibrations 

 which produce musical sounds. It was then stated that the perception of 

 sound, communicated through each ear, varied in the same individual; and, 

 further, that the impression of the pitch was not the same in both ears; the 

 last statement, although made on published authority, he denied, and he 

 wished to demonstrate this point. A vibrating body communicates its vi- 

 brations to another solid, of more extended surface, which materially in- 

 creases the force or volume of sound. For instance, the tuning-fork he set 

 into vibration, communicated vibrations to the air in its immediate neigh- 

 borhood, which could only be heard by placing the fork very near his ear; 

 but when he brought the handle of the vibrating fork in contact with the 

 table before him, the wood also vibrated, and a volume of sound was sent 

 out which could be distincly heard in every part of the room. This illus- 

 trates the principle of the sounding-board, which is applied to all stringed 

 instruments. Every sonorous body has a note of particular pitch which it 

 gives when it is struck, and if the same sound is made by a voice, the vi- 

 brating air will have the power of imparting its rate of motion to that body. 

 Thus the glass vane he ha^d before him was set into vibration by his voice, 



