429 



when raised to a given degree above the temperature of the water. These 

 results indicated that the air was generally above 90% of saturation, so 

 that the calculations on that basis were approximately correct. 



Coiiiprcsscd-Air Supply. Air was supplied at a pressure of 60-80 

 pounds through pipes from a large piston compressor at the University 

 power-house, about 200 yards from the Vivarium. It appeared to be 

 satisfactory air, although doubtless a better supply should be sought for 

 verv refined work. It contained nothing which could be injurious, except 



Jprou fiumid/fier 



Pig. 33. Showing an assembled spray humidifler ( N. H. S.). Air comes 

 Into contact with finely divided water at a low temperature in the spray cham- 

 ber and passes to the separator where any droplets of water are removed by 

 baffles. 



a rather large amount of carbon dioxide in some samples. There was a 

 slight odor from the oil used in the pump, which was decomposed under 

 pressure. This odor was not present when the best grade of oil was used, 

 and particularly in the summer time when a large amount of air was 

 drawn. For nearly all of the work the pressure was reduced to 3-5 

 pounds, the reduction being accomplished by a Mason pressure-reducing 

 valve. This valve has an advantage over others which have come to our 

 attention, as it gives practically constant pressure regardless of fluctua- 

 tions in the initial pressure and in the rate of flow through the valve. 



