58 ANNUAL OF SCIENTIFIC DISCOVERY. 



prepare for congealing. It has been ascertained that pumps of a cubic 

 foot capacity, worked at a temperature of 90 F., and fifteen revolu- 

 tions a minute, are adequate to making a ton of ice per day. 



COOLING THE ATMOSPHERE OF ROOMS IN WARM CLIMATES. 



PROF. PIAZZI SMYTH detailed to the British Association, at Edin- 

 burgh, a method proposed by him for cooling the atmosphere of rooms 

 in tropical climates. It is an application of the well-known property 

 of air to increase in temperature on compression, and diminish on 

 expansion. A compression of one fourth of an atmosphere is found 

 to be sufficient. The following arrangement of the machinery has 

 been adopted, for a one-horse power, which may be expected to 

 furnish a room with about eighty cubic feet of air per minute, cooled 

 15 to 20 below the atmosphere outside. A double-acting air-pump, 

 nine inches in diameter, and eighteen-inch stroke, making sixty double 

 strokes per minute, with a jacket of cold water round the cylinder, to 

 mitigate the heat of friction, forces the air into the lower end of a coil 

 of copper tubes, contained in a tub of water, three feet in diameter 

 and five feet high, where the cooling is effected. At the upper end 

 of the tube is a safety-valve, permitting an escape of the confined air, 

 when it exceeds seven pounds on the square inch, into a larger tube, 

 which at once conducts the now cooled air into the desired apartments. 

 The power used to work the pump may be steam, water, or animals. 

 The tendency to unpleasant moisture in the cooled air may be cor- 

 rected by making the tube, which conveys the cooled air into the 

 room, pass through a still colder vessel of water, so that the moisture 

 will be condensed on the inner surface of the metal. This vessel of 

 water may be kept cool by salts or other means. Thus we compress 

 air into a closed vessel, which is a good conductor of heat, when the 

 air rises at first to a degree proportionate to the compression, say 50 

 F. above what it was before. If we began with air at 100, it would 

 now have risen to 150, and would by degrees give off the extra heat 

 to the water surrounding, and, if the air is then allowed to escape, it 

 will fall again to 50 below 100' J , or to 50 F. If it were allowed to 

 escape immediately, obviously nothing would be gained, but by carry- 

 ing off the extra 50 by conduction and radiation, while the air is in a 

 compressed state, we evidently reduce the temperature as stated. 

 This method is considered particularly applicable to hospitals in In- 

 dia and other tropical climates. Civil Engineer and Architect' 's Jour- 

 nal, Sept. 



MODE OF CONVEYING THE COCHITUATE WATER BENEATH A 



NAVIGABLE STREAM. 



IN conveying the Cochituate water from Boston to East Boston, it 

 became necessary that the pipes should be carried beneath the naviga- 

 ble waters of Chelsea Creek, which is about 1,000 feet wide and 21 

 feet deep, in the channel, at low water. The mode devised for effect- 

 ing this by the engineer, Mr. W. S. Whitwell, is very ingenious. 



