484 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of about 3,000 feet along which the air, driven by the fan, was diffused 

 before it entered the ward. The cooling power of the boxes may be 

 assumed to be about oue tenth that of the walls. 



These were the arrangements through the month of May, with the 

 same benefit to the patients. In June, the summer heats were greater 

 and more constant, and the fan more steadily used. The temperature 

 of the air-chamber and the air passing thx'ough it had increased, and 

 that of the water had already risen to 70°, and is usually somewhat 

 higher later in the season ; the quantity of water required was large 

 and expensive ; it was therefore shut off permanently. The same 

 amount of ventilation, however, was continued, and the conditions as 

 to the air-chamber and the admission of the air to the ward were 

 unchanged. During the summer, the ward temperature gradually 

 rose until it differed but little from that of the open air. 



Still the comfort given to our patients and their nurses under both 

 these methods was immediate and decided. To those entering the 

 ward there was a feeling of freshness and freedom of air quite beyond 

 that of the other ward of similar construction, which had only the 

 usual summer ventilation. 



At first the walls of the air-chamber to a degree acted as coolers, 

 but this ceased as they became warmer. 



We may form some estimate of the probable effect of the boxes as 

 coolers in summer, by comparing it with their work as heaters in 

 winter. 



The average boiler temperature in December and January is 200° F. ; 

 that of the return, 145° ; therefore, 55° of heat is lost iu heating 

 120,000 c.f. of air hourly supplied to the wards in winter. 



From these data Professor Trowbridge has kindly made the follow- 

 ing computation : — 



''Mean temperature of water = 172.5° (173°) 



" « " air = ^ (30 + 70) = 50 



Mean excess of water temperature available 173-50 =123 

 Excess per degree rise of air temperature ^^ — 3.07 



" To cool the same amount of air from 80° to 70° (mean temperature 

 75") would require, if Newton's law hold, a mean temperature of 

 75° — 10 X 3.07 = 45° approximately." 



Our boxes, therefore, as then constructed, with a water circulation 

 at 58° F., were inadequate to our purpose as cooling boxes. It is 

 true the boxes could be enlarged. It has been computed that, with a 

 constant flow of cool water at 50° through boxes 5.G times as large 



