Humidity in Relation to Incubation. 

 By Wm. H. Day, Lecturer in Physics. 



In the preceding- portion of this Bulletin Mr. W. R. Graham has 

 outlined many practical experiments that have been carried on by the 

 Poultry department during the seasons of 1906 and 1907. For those who 

 wish to follow this station further in its endeavors to discover the scientific 

 laws that influence incubation, the following pages are written. We are 

 conscious of the fact that our readers may include all classes of persons 

 from the practical poultryman to the advanced scientist. To the former 

 we would say at the outset : It is primarily in your interests that we in- 

 vestigate these problems and publish our results, hence we feel bound ii\ 

 so far as possible to make even the scientific side of our work intelligible 

 to you ; and hence we shall endeavor throughout to present scientific 

 methods and truths in popular form and language. 



Some time ago a series of circumstances, which need not be related 

 here, led the department of Physics to enter upon a study of the evapora- 

 tion of water from soil and from plants, and this broadened out into a 

 study of evaporation in general. This in turn involved a study of the 

 moisture of the atmosphere. Now the Latin word for "moist" is humidus, 

 hence instead of "moisture of the atmosphere" we may say "humidity." 

 Since we were interested in the subject, Mr. Graham asked us to co-operate 

 with him in a study of the humidity in incubators ; for opinion as to the 

 desirability of moisture during incubation was sharply divided, some hold- 

 ing strongly that it was detrimental, that the chicks were often "drowned 

 in the shell," others holding just as firmly the contrary view that moisture 

 was highly beneficial. Before entering in detail into our investigations on 

 the subject it may be well for the sake of our practical readers to give a 

 brief review of the methods by which a knowledge of humidity is gained, 

 believing that such a review will lead to a better understanding of the 

 subject, "Humidity in Relation to Incubation." 



Determining the Amount of Moisture in the Air. 



Years ago little was known of the amount of moisture in the air. 

 But as science advanced and the influence of the humidity of the air upon 

 all life was realized, a fuller knowledge of the subject became desirable. 

 It was known that certain acids and salts had a great affinity for water, 

 and so the idea was suggested that if air were drawn through these sub- 

 stances it would be deprived of the water contained in it, the substances 

 gaining in weight by the amount of water absorbed. Investigation proved 

 that two or three drying tubes, in series, were sufficient to absorb all the 

 moisture from air being drawn through. Figure No. 1 shows the appa- 

 ratus evolved for the purpose. 



[291 



