QCT.- — ma.k. 1859-60.] Rooms in Tropical Climates. 325 



I know not, but conclude that they can only be reckoned by hun- 

 dreds ; while the cost of the passage home of three or four indivi- 

 duals only, would be abundantly sufficient for the making of the 

 first experimental machine. 



Here, however, I must leave the matter, having neither the time 

 nor the means to prosecute it farther, and will merely conclude 

 with the notice of a few suggestions which arise from the forego- 

 ing facts, and which may be enumerated as the following corolla- 

 ries : — ■ 



Cor. 1. On a mode of producing heat by mechanical force, and 

 which may be possibly useful in many cold countries where wind 

 and water power may be abundant. Frictional heat has been em- 

 ployed in some of the American mills, by making two plates 

 of iron rub against each other under water: but this is by 

 no means so profitable an application of power as by the com- 

 pression of air, and by having a coil of copper tube in the room, 

 and compressing the air only -^-th of its bulk, a heat of 360° Fah. 

 above the external temperature would be obtained. 



This manner of producing heat was illustrated by Sir J. Hers- 

 chell, in a note to his " Treatise on Natural Philosophy," rather, 

 certainly, as a theoretic principle, than in a practical way ; but as 

 I was led by it to the method of cooling air, I am bound to ac- 

 knowledge my obligations. The first person whom I am acquaint- 

 ed with, as having proposed the method for any industrial pur- 

 pose, is the Rev. Dr. Adamson, the Principal of the South African 

 College in Cape Town ; but I am not aware of his having entered 

 upon any inquiry into the thermotic effect of compression, and 

 the size consequent of the windmill which he would have to em- 

 ploy to heat a house of certain size. 



When however, the heat is wished to be applied at once to the 

 air which is breathed and fills the room, another plan may be 

 profitably employed. 



Let there be a coil of pipe as before, in a vessel of water out- 

 side the house, and let the pump be used for the purpose of ex- 

 tracting the air out of this pipe, at the opposite end of which there 

 is to be a very small hole, at which the air may enter, but not so 

 quickly, or in such quantity as it is extracted at the other. The 

 consequence of this will evidently be a rarefaction or expansion of 



