438 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



American Institute Polytechnic Association, ? 

 December 15, 1864. \ 

 Prof. S. D. Tillman, presiding ; B. Garvey, secretary. 

 The Chairman read the following- interesting- items relating to science 

 and art : , - 



Production of Ice. 



A description of Mr. A. C. Kirke's machine for producing cold by the 

 expansion of air, was read before the Chemical Section of the British Asso- 

 ciation for the Advancement of Science, The method employed is to alter- 

 nately compress and expand air in receivers ; that holding the expanded 

 air being surrounded by the liquid to be cooled ; the other containing com- 

 pressed air being surrounded with flowing water for the purpose of keep- 

 ing it cool. The same air is used over and over again, a wire gauze respi- 

 rator or regenerator being employed to ec|ualize the temperature in its 

 passage downward and backward between the two cylinders. The machines 

 move day and night without intermission, and with the power from one 

 ton of coal one ton of ice is made. It is superior to the ether machine in 

 which there is an unavoidable loss from the escape of ether. 



This item reminded Mr. Bartlett that a friend of his in Washington had 

 used compressed air for cooling water, but not understanding the difference 

 between the intensity and the quantity of heat, he failed in operating on a 

 large scale. He found how easy it was to cool the mercury in his thermo- 

 meter, but how more difficult to cool a large quantity of water. 



Mr. T. D. Stetson said there was a fine machine in this city for freezing 

 water, but it was found not to be economical. 



No Nitrogen in Steel. 



At the November meeting of the London Chemical Society it was stated 

 that Messrs. Stuart and Baker have repeated 'the investigations of Premj^ 

 using however the well known brands of English steel, also the Spiegelisen 

 largely used in making steel Tliey found no nitrogen in these varieties 

 of steel, but they suggest the possible existence of the nitride of titanium, 

 which might under special circumstances account for the appearance of 

 nitrogen. 



Protection of Iron Plates. 



M. Bequerel announced some time since before the French Academy of 

 Sciences, that iron-plated vessels could be preserved from oxidation by 

 fixing bands of zinc on the plates at given intervals. At a later meeting 

 of the academy he stated tliat the protection was not so complete in soft 

 water owing to the fact that the electric current generated at the line of 

 contact between these metals diminished in intensity more rapidly in pure 

 water. The remedy is to use a proportionably larger number of zinc 

 bands. Bequerel found that 9,381 cannon balls, twelve centimeters diame- 

 ter under soft water, require for protection two square meters of zinc 

 surface. 



Dye for Feathers. 



Beautiful shades of red, violet and blue, are obtained with aniline colors 

 which adhere to feathers with as much brilliancy as to wool and silk. The 



