PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 379 



ice or cooling surface, and, as it is graclnally warmed in its descent, 

 it expands, and the dew-point is lowered ; so that the dew-point 

 would be as far below the temperature within the house, as if 

 there had been no cooling. 



Mr. Dibben. — Five degrees reduction of temperature would 

 be all that would be required to make a very sensible difference. 

 I think it would be better to change the air moderately and 

 give us more of it. Mr. I), proceeded to describe the eastern 

 method of hanging up mats, &c., to cool the air by evaporation, 

 and an apparatus of his own, producing the same effect with the 

 use of porous earthen ware. 



Mr. Johnson described a method of refrigeration, by placing in 

 the window a box filled with ice, and pierced with pipes to admit 

 the air from the outside, so that all the admitted air must pass 

 through the pipes. 



Mr. Seely remarked that the plan cited by Mr. Koch was a 

 very pretty experiment to show a class in chemistry ; but prac- 

 tically it Avould be useless, on account, in part, of the fact that 

 the heat must be removed at each operation. 



Mr. Churchill considered the question of moist air very 

 important. He had found that a draft is seldom injurious at a high 

 temperature unless it is damp, but that a person subject to neu- 

 ralgia, for instance, would find a damp draft of air verypainful. 



Mr. Rowell stated that the temperature of the earth fifty feet 

 below the surface is but fifty or fifty-four degrees, and proposed 

 that the Croton water should be carried down that distance by 

 a bend in the pipe, to cool it. 



Mr. Fisher. — It would soon warm the earth so as to be ineffi- 

 cient. 



Mr. Rowell. — Not if it come to a stratum of water. That 

 would keep it cool. 



The same subject was continued. Adjourned. 



American Institute, Polytechnic Association, ? 



May 30, 1861. ] 

 Professor Cyaus Mason in the chair. 



BREAD machinery. 



Mr. Fisher called attention to a new plan for making bread 

 which had been lately introduced in a bakery on the Third 

 avenue. Water mixed with flour is impregnated with carbonic 



