[CALLBNDAK & m'leod] OBSERVATIONS OF SOIL TEMPERATURES 



33 



to be very marked seasonal variations of the diffusivity, due to the condi- 

 tion of the soil, and to the amount of percolation. The curve of the 

 variation of the diffusivity at different seasons of the year exhibited in 

 Fig. I., for the period 1896-1897, will be seen to bear a remarkably close 

 resemblance to that obtained last year, and to confirm our previous con- 

 clusions in the most complete manner. The following table gives the 

 dates for which the diffusivity has been calculated. 



Variation of the Thermal Uipfcjsivity at Different Seasons of 



THE Year. 



Period. 



May 9— June 1 . . . 

 June 1-6 



" 6-13 



" 13-20 



" 20— July 1... 



July 1-15 



Aug. 1— Sept. 1... 



Sept. 1-29 



Sept. 29— Oct. 31 

 Oct. 31— Nov. 19. . 

 Nov. 19— Dec. 25. . 



Nov. 27-28 \ 

 18 hours / 



Dec. 2.5— Feb. 1 . . 

 Feb. 1— March 1. . 

 March 1— April 1 . 

 April 1— Mav2. . 



May 2-7 



May 7 12 



No. or Days. 



7 

 10 

 14 

 31 

 28 

 32 

 19 

 36 



a 



38 

 28 

 31 

 31 



Diffusivity. 



00561 

 00461 

 00544 

 00716 

 00514 

 00606 

 00351 

 00504 

 00774 

 00566 

 01488 



323 



00272 

 00156 

 00241 

 00426 

 01050 

 00834 



Rain per Day. 



•115 



•002 



•381 



•000 



•125 



•223 



•173 



•096 



•091 



•126 



•030 



/ "021 per hour 

 I Ratio 0-5()4 



•013 



•017 



•060 



'101 



•044 



•114 



On examining these results, it will be observed that the diftusivity 

 during the month of February, when the ground was so frozen that there 

 was practically no percolation, namely, -00156, is practically identical 

 with the value observed during the last two winters under the same con- 

 ditions. We may, with justice, conclude that this is the value of the 



Sec. III., 1897. 3. 



