PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 591 



possible that several hundred atmospheres of pi'essure may facilitate some 

 of the chemical changes involved in the transformation of water and car- 

 bonic acid into the organic compounds met with in animals and plants of 

 low organizations, found at great depths in the ocean, and thus, to a certain 

 extent, compensate for diminished light. 



Bessemer Steel. 



It is said that two ships in foreign waters, besides one in England, ai'e 

 being built of steel made by the Bessemer process. 



Health of New York.' 



The Chairman read a statement presented by Mr. J. Bull, giving the ratio 

 of death in this city, derived from the census of 1860, and the City Inspec- 

 tor's Report for 1861. It appeared that the number of deaths during the 

 year for every hundred of the population, was 1.33 in the Fifteenth Ward, 

 and 7.24 in the Nineteenth Ward; the general average for all the wards 

 being 2.84 per hundred. In relative mortality the wards stand in the follow 

 ing order: 15th, 22d, 18th, 13th, 9th, 16th, 8th, Uth, 20th, 10th, Ith, Itth, 

 3d, 2d, 14th, 12th, 1st, 21st, 4th, 5th, 6th, 19th. 



Inquiry was made why in the Nineteenth Ward the deaths are double 

 those of any other. 



jyir. N. C. Ely replied that vei*y many of the hospitals of the city were 

 located in that ward, as well as asylums for children. It was well known 

 that speaking comparatively, mortality among children in this city was 

 unusually large. An interesting discussion followed upon the causes 

 affecting the sanitary condition of the city, in which Messrs. Bartlett, 

 Overton, Gavitt, and Stevens, participated. 



Electrotypes. 



Electrotype copies of the bronze gates of the cathedral at Pisa, were 

 being made for the South Kensington Museum, England. Mr. Stetson 

 inquired how this process was conducted in this case. Mr. Gavitt replied, 

 that the moulds were doubtless made of gutta percha, or similar plastic 

 material, which could be applied when the object to be copied was in a 

 vertical position. 



Surface Condensers. 



The Chairman having announced the subject selected for the regular dis- 

 cussion, alluded to the recent death of Mr. Samuel Hall, of England, the 

 inventur of the surface condenser, which was first substituted for the Watt, 

 or jet condenser, on steamships, to obviate the necessity of using salt water 

 in the boilers. The first ship which came to our shores having a surface 

 condenser was the Sirius. The device of Mr. Hall was defective, it could 

 not be kept tight. The objections to surface condensers had been obviated 

 by American inventions, and this method of obtaining a vacuum was now 

 being adopted very generally for ocean steamers. Several engineers and 

 inventors are present to take part in this discussion. As Mr. SewelPs dia- 

 grams are already arranged before us, he is entitled to the floor. 



Mr. Wm. Sewell remarked that he supposed the object of the condenser, 



