1904.J DUDLEY — PASSENGER CAR VENTILATION. 253 



ventilators produce suction as has already been described, and these 

 two acting together lead to change of air in the car. The control 

 of the system, that is the means by which the amount of air passing 

 through the car is diminished, is in the ventilators. Each venti- 

 lator is provided with a register, and when these registers are 

 closed the total amount of air passing through the car is diminished 

 a little over one-half. It will be observed that by partly closing all 

 the ventilators, or closing a part of them, any intermediate figure 

 between these two can be obtained. It is found essential to have a 

 portion of the passageway in the ventilators over the lamps contin- 

 uously open, in order to carry off the products of combustion. The 

 register at no time closes this portion of the ventilators over the 

 lamps. 



The experimental work having led up to the construction finally 

 decided on, it remained to actually put the system to test and see 

 exactly what was being obtained. The first experiment was to see 

 whether when the car was standing still, and heat was in the car, 

 the movement of the air would be in the desired direction, namely, 

 into the car through the hood, and out through the ventilators on 

 the upper deck. With some systems of car ventilation where the 

 movement of the air is almost wholly a function of the movement 

 of the train, when the train stops the air movement is in the 

 opposite direction, owing to the relation between the heating 

 system and the ventilating system. In the system which we are 

 dealing with this does not take place, for obvious reasons, namely, 

 as has already been stated, the exits are higher than the in-takes. 



The second test concerned the air from the closet. Some anxiety 

 was felt as to whether the ventilating system would take air from 

 the closet into the car. As a precautionary measure a small 

 '' Globe " ventilator was put in the roof of the closet, and also the 

 proportions of parts of the system were designed in such a way that 

 when the car was in service, there would be a plenum in the car 

 produced by the hood rather than a vacuum produced by the 

 suction of the ''Globe" ventilators. As a matter of fact, the 

 construction finally adopted gave very close to a balance between 

 these two features. However, many experiments show without 

 question that when the car is in motion, and the ventilating system 

 in full operation, the air movement is toward the closet, instead of 

 from it. 



A third test of the system was to determine the actual amount of 

 air passing through the car. In order to decide this question, a car 



