14 ROYAL SOCIETY OF CANADA 
THERMAL DIFFUSIVITY. 
The value of the thermal diffusivity has been computed for suitable 
intervals of time covering the entire period now reported on. The results 
are tabulated below, and are also represented graphically on the accom- 
panying plate. These results show that the value of k/c is, for the lower 
strata, in general less than the average, but that for a short time in the 
spring or early summer, the contrary is true. The latter condition pro- 
bably corresponds to a stage in which the moisture of the melting snow 
has penetrated to the lower depths, and the upper layers are relatively 
dryer. 
When the ground is protected by snow and there is no percolation, 
the value of k/c is seen as in former years to be a minimum and very 
constant, the average value corresponding to ‘0015, which, as stated in 
former communications, may be taken as the value of diffusivity due to 
pure thermal conduction for the sandy soil in question in a dry condition. 
All values above this being due more or less to influence from percolation, 
The normal value for the full depth, under average conditions of soil, 
during the summer months, may be put at ‘0075. 
VALUES OF THERMAL DIFFUSIVITY OF THE SOIL FROM MAY 157TH, 1897, 
TO May 2np, 1900. 









Dirustvine 
No... SSS rain 
Period Depth of Soil. 
of days - per day 
20” to 60”|60” to 100”|20” to 100” 
1897 
Mraiyil5) Gone time tae ae eer ere eter 20 ‘0059 ‘0067 ‘0063 7-132 
SUBS ATS LOMME EN AIS ARR CAE NME 15 ‘0119 “0059 "0087 ‘055 
June UG) qroy PiU Ie Sec RENE PRET 12 “0051 0052 "0056 "198 
JU TALALONO EEE ES eestacociaetate tee 14 0059 "0053 ‘0056 ‘218 
JUIYALONÉO SIP eee tate cic CARE TONNES | ‘0038 *0059 "086 
Dal Loue TG ee TEA RO iy 20087, || RES “052 
September 21 to October 7......... 16 “0054 | "0017 ‘0052 ‘019 
October 1102010 Rene id 16 ‘0049 | ‘0031 0042 026 
October 23 to November8 ......... 16 “0088 | *0033 | ‘0037 | 100 
November Stoner cic 15 ‘0010 | +002) | *0037 ‘035 
November 23 to December 9 ........ 16 ‘0112 | “0038 “0061 069 
1898 
January 3 to February 11.......:.-. 39 - 0009 | -0010 | ‘0010 016 
February 18 to March 19 ..... tre 29 “0064 | “0014 0026 038 


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