732 STATE BOARD OF AGRICULTURE. 



average during May and June the sand and gravel were about 4 or 5^ F 

 warmer than the peat at the 6-inch depth and only about 2°F warmer 

 than the clay and loam, while as an average during the months of July 

 and Aug-ust the sand and gravel had only about 2 or 3°F higher tempera- 

 ture than peat and about 1 or 2°F greater than the clay and loam. 



The higher average temperature of tlie sand and gravel over that of 

 the clay, loam and peat during the spring and summer months, when their 

 surface was not covered by a thin layer of sand as in the first year, is 

 very noteworthy. It goes to show that those soils which possess a high 

 moisture content are kept somewhat colder, during those months that 

 the temperature rises, than the soils of low water-holding capacity, in 

 spite of the darker color of some of the former. Evidently, these various 

 soils lose different amounts of water through evaporation and conse- 

 quently maintain different degrees of temperature. 



That the factor of evaporation is the casual agent for this variation 

 in temperature between the different classes of soil is shown by the fact 

 that when the surface of these soils is covered by a thin layer of sand 

 so that the evaporation of their water is more or less equalized, this 

 variation disappears, and all the soils have practically equal magnitude 

 of temperature as will be subsequently shown. 



The highest daily average temperature for the year was reached between 

 June 28 and 29 by all soils and at all three depths. The magnitude of 

 temperature on June 28 for the 6, 12 and 18-in. depths respectively was as 

 follows: gravel 87.83°, 81.30°, 78.70°; sand 85.03°, 79.87°, 75.67°; loam 

 85.83°, 79.00°, 73.37°; clay 84.40°, 78.33°, 73.87°; and, peat 80.37°, 

 74.73°, 70.97°F. 



The highest monthly average temperature, however, occurred in July 

 and ranged as follows for the 6, 12 and 18-inch depths, respectively: 

 gravel 78.73°, 75.77°, 74.74°; sand 77.23°, 74.79°, 73.34°; loam 77.89°, 

 75.25°, 72.55°; clay T6.38°, 74.11°, 72.79°; and, peat 75.34°, 73.75°, 

 71.96°F. 



The high temperature continued to prevail until August and then 

 began to diminish. The differences in temperature between the various 

 types of soil also commenced to decrease in August and by the middle 

 of September they had almost entirely disappeared and the various 

 soils then began to have identical degree of temperature. From this 

 period on throughout the months of October and November or until the 

 beginning of the third year in December, they cooled at about the same 

 rate and maintained practically equal magnitude of temperature. 



There were days, of course, when the average temperature of the dif- 

 ferent soils varied appreciably. But this occurred only whenever the 

 air temperature changed very rapidly. On such occasions the peat would 

 have a slightly higher temperature than the other soils if the air tempera- 

 ture went down rapidly, while the mineral soils and especially the sand 

 and gravel would manifest a slightly higher temperature if the air tem- 

 perature rose suddenly and rapidly. But as an average for the month all 

 the soils were equally warm. 



The same rate of cooling and equal magnitude of average temperature 

 of the diverse classes of soil during the fall months occurred in all four 

 years and are indeed remarkably interesting and contrary to the gen- 

 eral popular belief. It has been popularly believed that since the sandy 



