250 DUDLEY — PASSEN-GER CAR VENTILATION. [Aprils, 



figure. There is some difference of opinion as to whether the 

 amount is not excessive, and it is perhaps fair to say that the point 

 cannot be regarded as satisfactorily settled. It may not be amiss 

 to mention that in conversation with Professor Atwater, of the 

 Wesleyan University, Middletown, Conn., who has made a large 

 number of experiments in the human calorimeter, he stated that the 

 inmates of the calorimeter do not complain of drowsiness or of any 

 unpleasant feeling even though the carbonic acid reaches a very 

 much higher figure than anything that has been mentioned, but do 

 complain of drowsiness and languor with occasional headache if 

 the amount of moisture in the air gets much above the normal. It 

 may not be amiss to mention at this point that, in the system of 

 car ventilation to be described, no attempt has been made to get 

 the large amount of air mentioned, namely, 180,000 cubic feet per 

 car per hour. The experimental work has been limited to an 

 attempt to get 60,000 cubic feet of air per car per hour, or about 

 1,000 cubic feet of fresh air per person per hour. 



Fifth. One more question must be discussed a little in order 

 that what follows may be completely understood, namely, how is it 

 possible to measure the amount of air that goes into and out of a 

 car per hour? It may be said that attempts to do this by means of 

 sizes of apertures and velocity of currents have not succeeded very 

 well, and it will be obvious why this should be so, since there are 

 a very large number of small apertures in a car, both inlets and out- 

 lets, all of which are elements in the problem. No window or door 

 is tight, and even though the velocity of the air going out of the 

 ventilators is measured, the friction against the sides of the venti- 

 lators is such that it is very difficult to get an average figure for ve- 

 locity. Accordingly another method has been employed, as follows : 



A car is loaded with a definite number of inmates, and after a 

 run under ordinary conditions a sample of the air from the car is 

 secured and analyzed for carbonic acid. It may be supposed that 

 the analysis shows twelve cubic feet of carbonic acid per 10,000 cubic 

 feet of air. But four cubic feet are a normal constituent of the air, 

 leaving eight cubic feet coming from the inmates of the car. If 

 there were sixty of these and each one gives off carbonic acid at the 

 rate of 0.60 of a cubic foot per hour, it is obvious thirty-six cubic 

 feet per hour are to be dealt with and the problem becomes, '^ How 

 much fresh air must be mixed with thirty-six cubic feet of carbonic 

 acid from the car inmates, so that the resulting mixture would show 

 on analysis eight cubic feet of carbonic acid from the same source 



