ACKNOWLEDGMENTS 



The authors wish to acknowledge with sincere thanks 

 the assistance rendered by P. A. Wilcox, poultry farm 

 foreman, in management of experimental pens and main- 

 tenance of laying records ; by Professor G. M. Foulkrod, 

 who aided in the engineering phases ; by Dr. C. L. Martin 

 in making autopsies of birds; and by Dr. D. H. Chapman 

 of the Geology Department, who furnished the clima- 

 tological data. 



