56 
Proceedings of the Royal Society of Edinburgh. [Sess. 
VIII. — The Effect of Weather Changes on Soil Temperatures. By 
Captain T. Bedford Franklin, B.A. (Cantab.). 
(MS. received January 27, 1920. Read March 15, 1920.) 
SUMMARY. 
SECTION PAGE 
I. Introduction . . . . . . . . .56 
II. Sunshine and Shade — 
(a) Movements of Soil Air and Water . . . . .57 
( b ) Diffusion of Water Vapour ...... 59 
(c) A Dry Surface Mulch ....... 60 
III. Rain — 
(a) The Percolation of Water ....... 62 
( b ) Rapid Changes in Underground Temperature after Heavy Rain . 63 
IV. The Relation of the Above to — 
(a) Various Soils — Sand, Loam, Clay ..... 64 
(b) The Seasonal Changes of Conductivity ..... 66 
V. Heat Transfer in the Soil ....... 66 
VI. Wind and Relative Humidity ...... 68 
VII. Frost— 
(a) The Effect of Frost ....... 69 
(b) The Conductivity of Frozen Soil and the Depth frozen for Various 
Surface Temperatures . . . . . . .71 
VIII. Snow .......... 72 
IX. The Coming of Spring ....... 74 
X. Weather Changes of Long Period . . . . . .77 
XI. Conclusions . . . . . . .78 
Section I. — Introduction. 
The temperature of the air depends on so many varying factors that its 
prediction is a matter of considerable difficulty, and can only be made with 
any degree of certainty when the minimum number of these factors is at 
work. Underground temperatures are dependent not only on the same 
factors as affect the air temperature, but, in addition, are much more 
affected by conductivity, rainfall, evaporation, latent heat, etc., and thus 
the changes in temperature beneath the surface of the soil constitute a 
much more complex problem. 
In my previous papers I have discussed the question of underground 
temperature under very special conditions only — namely, during calm, 
clear nights ; but as it is a sound principle to assume that the points of 
even the most simple aspect of a problem cannot be appreciated fully 
until the whole complex problem has been investigated, I now propose 
