PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 497 



if left so that it can escape, it will soon be equally diffused, if the 

 amount is not large. In deep wells, containing this gas, this law 

 does not hold good 5 it may be, however, that the gas is supplied 

 faster than it can be carried off. 



The only true method of v^entilation is, to continually carry off 

 all the air of a room, and constantly supply it with fresh air. 

 The importance of this subject is being realized by our public 

 officers. Congress lately appropriated more than $100,000 to 

 ventilate the Capitol. 



Mr T. D. Stetson remarked, that to properly ventilate a room 

 is a matter of some difficulty. The air should not come in so as 

 to blow upon a person's head or neck. It is very well to open 

 doors and windows for a robust person, but there are those to 

 whom it would be decidedly injurious. It is difficult to get air 

 into a room without incommoding any one. Where the top of 

 the window is lowered, a comparatively solid body of air comes 

 in, and mingles w^ith the heated air only to a limited extent ; by 

 dividing up this column of air, the mixing would be much accel- 

 erated, while no decided current would be produced. To accom- 

 plish this, he proposed to insert into the upper window sash 

 a number of small tubes connecting with the air outside. 



Dr. J. W. Richards said, the thermometer is now much more 

 relied on than the ear to detect diseases of the lungs. So many 

 persons dying from what is called sun-stroke were never known 

 here as during the past summer, but numbers of persons have 

 died who were not in the sun, and have kept in the shade- Per- 

 sons who have small development of the chest are those who are 

 most likely to die from the excessive heat. A very high medical 

 authority has recently published a work on the impurities of the 

 atmosphere, and he has very clearly shown the amount of con- 

 timiination in a thousand cubic feet of air. There is a much 

 greater amount of air required to ventilate a room occupied by a 

 sick than by a healthy person. 



The Association voted to continue this subject. Adjourned. 



[Am. Inst.] FF 



