78 Proceedings of the Royal Society of Edinburgh. [SesS. 
in warming up the underground layers in a very short time ; on April 2, 
1919, the 4-inch depth temperature, which for some weeks had been near 
freezing-point, rose in the period of 26 hours to 5’0° C., and, thanks 
to a succession of overcast nights, mounted steadily to 9’4° C. on April 8, 
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Table XIY. — Values op — - during Long-Period Temperature Changes. 
•K 0 
Date. 
Period 
Minimum 
to 
Maximum. 
Value 
of 
Bo’ 
Position of Cyclonic 
Depression. 
Weather. 
Rain 
during 
Period. 
1919. 
April 2 
26 hours 
•55 
Scandinavia 
Overcast, S.W. wind. 
nil. 
„ 17 
33 „ 
•42 
Iceland .... 
55 
1 mm. 
Sept. 29 
54 „ 
•57 
N. Scotland 
55 
2 mm. 
Oct. 16 
31 „ 
•50 
Scandinavia and Iceland . 
55 
nil. 
Nov. 22 
34 „ 
•68 
Iceland .... 
5 5 
Dec. 19 
26 „ 
•52 
Scandinavia and Iceland . 
„ 
55 
1920. 
Jan. 15 
28 „ 
•58 
Iceland .... 
55 
55 
thus providing a much-needed growing period during that time. Two 
clear nights on April 8 and 9 reduced the 4-inch depth temperature to 
4‘2° C., but a second long-period spell of cyclonic weather on April 17 
brought it up to 9’6° C. again, and so prevented any decided check to the 
growth of vegetation. 
Section XI. — Conclusions. 
r. 
1. The values of ~ have a wide range of variation, from T9 in very 
K 0 
dry soil to *85 during heavy rain ; the most common value is about *40. 
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The monthly mean values showed a decided connection between ~ and 
K 0 
the frequency of rainfall ; in fact, percolation of rain seems to be the 
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dominating factor in deciding the value of -ph 
K 0 
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This is also borne out by the different values of ^ in various soils 
K 0 
according to their behaviour with regard to water : in sand the values 
change with mercurial rapidity, due to the easy percolation of rain and 
subsequent rapid drying, while in clay they change but sluggishly, since 
clay takes up and parts with water with difficulty. 
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2. In view of the fact that the values of and therefore the values 
R'o 
