EXPERIMENT STATION BULLETINS. 689 



In undertaking an investigation of the subject, therefore, it was re- 

 solved to study it from all standpoints as systematically and thoroughly 

 as possible. The plan finally decided upon consisted (1) of study in «^ 

 individually or in combination most of the chief intrinsic factors affect- 

 ing the soil temperature, under controlled conditions, (2) investigating 

 the influence of these various important factors upon soil temperature 

 under field conditions and (3) ascertaining the relationship between th^i 

 soil temperature and the different meteorological elements or external 

 factors. 



In the report of 1913^ there were embodied the results of the 

 completed laboratory experiments on the intrinsic factors influencin-v 

 soil temperature and one year's data of the field experiments. The field 

 experiments have been continued up to the present time, or for four 

 years, and it is the purpose of this bulletin to present the additional 

 data obtained from these experiments and also the final conclusion that 

 might be deducted from the entire investigation. 



iTechnical Bui. 17. Mich. Expt. Sta. 1913. 



87 



