oct. — ma.r. 1859-60.] Rooms in Tropical Climates. 321 



be desired in the colonies, where good mechanical workmen are 

 generally scarce. 



The size for a one-horse power engine, or its near equivalent, 

 two bullocks, and working at \ of an atmosphere pressure, so as 

 to give about 90 cubic feet of air per minute, and cooled at least 

 20°, making fall allowance for losses from various sources, would 

 be 1 foot in diameter, and 1*5 in length, or in the stroke ot the 

 piston, the number of strokes being about 30 or 35 double ones per 

 minute. This gives a speed to the piston of only 90 or 100 feet 

 per minute, but it is much better to have a large pump moving 

 slowly for this purpose, than a small one moving quickly, as in 

 this case so much needless heat would be produced by the friction 

 of the pistons. The slow motion of the bullocks can likewise, in 

 the former case, be so much the more easily converted into the ne- 

 cessary speed for working the pumps, and would be done on the 

 supposition of the diameter of the bullock path being 30 feet ; 

 and it should nol be less, to allow the animals to have a fair and 

 straight pull, and their rate of walking two miles an hour, by two 

 sets of wheels and pinions, the first from the large cog wheel on 

 the bullock shaft producing an increase of 5 or 6 times, and the 

 second about 3. A good engineer should be employed for the pump, 

 and metallic piston and valves be adopted ; and the whole should be 

 fitted in to a frame in this country, with connecting rod and crank axle 

 applied, so that it might be easily adapted to any existing Mills in 

 India ; and that no injury should haply accrue to the piston or the 

 interior of the barrel by clumsy workmen inserting too long or too 

 short a connecting rod. 



The next part of the apparatus is the cooler, which may be made 

 in various forms, as a copper pipe, one or two inches in diameter ; 

 very thin, in order to conduct heat more readily, and about 100 feet 

 long, with a spring valve at the end farthest from the pump, and ca- 

 pable of being loaded with any particular pressure per square inch 

 which it may be desirable to work at. The pipe may be conveniently 

 coiled up and placed in a barrel full of water, entering at the top, 

 and leaving it at the bottom ; so that the air, gradually cooled as it 

 goes along the pipe, may meet the coldest water at the bottom of 

 the worm, and thus be more completely refrigerated. A small 

 supply of fresh cool water from the river or spring or tank, or 



