47 



Table XVII : Actual vs. Apparent Humidity in Incubators. 



In this table the wet- and dry-bulb results are the averages of from 

 three to five readings, the "absolute" results of from seven to ten readings. 

 Perhaps the dry machine should be noticed first. The actual humidity was 

 only 21.3 per cent., an average of ten readings taken on five different days. 

 Of these ten only one was greater than 22 per cent., and only two less than 

 19 per cent. In fact one of the outstanding features of this test was the 

 uniform humidity of this dry machine; come back to it when I would, its 

 humidity was always the same within very narrow limits of variability. 

 Another noteworthy fact with regard fo this machine is that the vapor 

 pressure in it was practically the same as in the room, .433 inches for 

 the former and .444 inches for the latter. The room pressure was the 

 average of five readings taken on the same five days as the incubator 

 readings. Since these pressures were nearly equal, there would be little 

 transference of vapor either way. But all determinations were made 

 during the day. At night with a drop in temperature the room vapor 

 pressure would fall, under which conditions vapor would pass from the 

 incubator to the room. The apparent humidity by the wet and dry bulb 

 method was much higher than the actual as 34.4 to 21.3, i.e., the appa- 

 rent is astray 13. 1 on 21.3, an error of 61.5 per cent. This great discrep- 



