692 STATE BOARD OF AGRICULTURE. 



all the soils began to have approximately equal degrees of temperature 

 with peat being slightly warmer. 



The temperature of the five different types of soil, namely, gravel, sand, 

 humus loam, clay and peat, whose many intrinsic factors were investi- 

 gated in the laboratory as already discussed, was measured daily through- 

 out a whole year under field conditions, at three different depths. The 

 data yielded by this investigation showed that when all these dill'erent 

 types of soil were covered with a thin layer of sand their average tem- 

 perature was practically the same throughout the year except in the 

 early spring when they were undergoing thawing. At this period their 

 average temperature was markedly different, especially between that of 

 the mineral types and peat, due to their different rate of thawing. After 

 they were all completely thawed, however, their average temperature 

 reached about the same degree and remained practically the same until 

 the next thawing period. Unlike in tlie spring, in the fall they all cooled 

 at about the same rate. The only other time that their average tem- 

 perature varied appreciably besides in the spring was Avhenever there 

 occurred rapid changes in the air temperature, but they would soon 

 reestablish their equilibrium. The amplitude of temperature of course, 

 was very different in them. It was greatest in sand and gravel, followed 

 in order by clay, loam, and peat, respectively. 



The results of the last investigation, therefore, indicated that the 

 average temperature of the diverse classes of soil does not vary as much 

 as is popularly believed or as one would think, in view of the great 

 variation of the intrinsic factors in them. 



ADDITIONAL EXPEKIMENTAL DATA ON THE TEMPERATURE 



OF DIFFERENT TYPES OF SOIL AT DIFFERENT 



DEPTHS AND UNDER DIFFERENT SURFACE 



CONDITIONS FOR 1913, 1914, AND 1915.= 



PLAN OP THE EXPERIMENT. 



As described in the first report this investigation was prepared by mak- 

 ing a long trench a little over three feet wide on a smooth and slightly 

 rolling piece of ground, covering the bottom with a thin layer of a sandy 

 soil so as to be uniform throughout, then placing into this trench, about 

 one foot apart, wooden boxes 3x3x3 feet without bottom or top, and then 

 filling these boxes with five different types of soil, namely, gravel, sand, 

 clay, humus loam, and peat. After they were flooded with water several 

 times and a certain length of period was allowed to elapse in order that 

 they might settle, a study of their temperature was commenced. Their 

 temperature was measured at three different depths, G, 12, and 18, or 

 2, 4, and G inches, three times a day, usually at about 7 A. M. 12 M. and 

 G P. M. every day throughout the year except Sundays, by means of 

 electric resistance thermometers. These instruments consisted of resist- 



*The author wishes to express his deepest gratitude and Indebtedness to Mr. M. Wolkoff, a gradu- 

 ate student, for his most loyal and excellent intelligent support In the conduct ol the following experi- 

 ments and in the preparation of the many laborious tables. 



