oct. — mas,. 1859-60.] Rooms in Tropical Climates. 313 



therefore, for healthy and robust life in tropical climates, is air cold 

 and dry, cold to the thermometer, and dry to the hygrometer, or 

 in other words, dense, and containing little else than the necessary 

 oxygen and azote, and this supplied to a room, fresh and fresh in a 

 continued current. 



The. method by which I propose to accomplish this consumma- 

 tion, so devoutly to be desired, is chiefly by taking advantage of 

 the well known property of air to rise in temperature on compression, 

 and to fall on expansion. If air of any temperature, high or low, 

 be compressed with a certain force, the temperature will rise above 

 what it was before, in a degree proportioned to the compression. 

 If the air be immediately to escape from under the pressure, it will 

 recover its original temperature, because the fall in heat, on air ex- 

 panding from a certain pressure, is equal to the rise on its being 

 compressed to the same ; but if, ivhile the air is in its compressed 

 state, it be robbed of its acquired heat of compression, and then be al- 

 lowed to escape ; — it will issue at a temperature as much below the 

 original one, as it rose above it on compression. Thus the air, 

 being at 90°, will rise, if compressed to a certain quantity to 120°; 

 if it be kept in this compressed and confined state until all the 

 extra 30° of heat have been conveyed away by radiation and con- 

 duction, and the air be then allowed to escape, it will be found, on 

 issuing, to be of 60° of temperature. If a cooler be formed by a pipe 

 under water, and air be forced in under a given compression at one 

 end, and be made to pass along to the other, it may thereby, if 

 the cooler is sufficiently extensive, be robbed of all its heat of com- 

 pression, and if the apparatus is so arranged, as it easily may be, 

 that at every stroke of the pump forcing in air at one end of the 

 pipe, an equivalent quantity of the cooled compressed air escape 

 from under a loaded valve at the other ; there will be an intermit- 

 tent stream of cooled air produced thereby of [60° Fahrenheit in 

 an atmosphere of 90° in the numerical case just given, which may 

 be led away in a pipe to the room desired to be cooled. 



So much for the theoretical principle of this operation, of as it 

 were, squeezing the heat out of the air ; but before thinking of it 

 for practical purposes, it is necessary to ascertain what is the ther- 

 motic effect of compression, i. e. how many degrees in temperature 



