34 



Humidity in Incubators. 



When Mr. Graham invited us to assist in his investigations, the 

 object was to study the humidity in incubators, for we did not then think 

 of being- able to determine the humidity in the hen's nest. The method 

 we laid down for ourselves was: (i) To determine the humidity in incu- 

 bators as ordinarily run ; (2) to run incubators at various humidities, note 

 the results, and thus determine whether humidity affects the hatch, and 

 if so to learn the most desirable amount of moisture for the production of 

 large hatches of strong chicks. For this work it was necessary to have a 

 wet and dry bulb so mounted that they could be set in the incubators. 

 Fig. 2 shows the form used. 



At the outset it was thought wise also to rig up each incubator with 

 a small motor fan which could be run to fan the wet bulb in order to 

 arrive at the proper humidity in case the incubator air should be so stag- 

 nant as to give a false reading without fanning. Fig. 3 shows the hygro- 

 meter (wet and dry bulb) together with fan and battery to run it. 



Fi<* 3— Small motor fan which was set inside the incubator 

 to fan the wet- and dry-bulb hygrometer. 



Testing this apparatus in the room, we learned that at middle humid- 

 ities fanning makes practically no difference in the readings, but at high 

 or low humidities it makes a great deal. In the incubators fanning always 

 made a great difference, giving much lower readings than without fanning, 

 showing incidentally that the circulation of the incubators is not equal in 

 effect to free diffusion in the room. The use of the fan in the incubator 

 had one defect, however : it disturbed the normal conditions whenever a 

 reading was taken, stirring up the warm and cold layers and almost in- 

 variably raising the temperature near the eggs for the moment and thus 

 giving a humidity somewhat too low. Table No. IX. contains a record of 

 the hatches run during the season of 1906. 



