No abstract

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.

No abstract

No abstract

In my previous paper to the Society on the same subject I came to the conclusion that the temperature of the surface of open cultivated soil fell rapidly at the beginning of a calm clear night until it was such a number of degrees below the temperature at the 4-in. depth as to make the upward conduction from that depth to the surface balance the radiation. After this stage was reached the surface and 4-in. temperatures fell at the same rate.If, therefore, the temperatures of the surface and 4-in. depth and the conductivity of the layer of soil between the 4-in. depth and the surface were known from readings of electrical resistance thermometers, and the rate of radiation was calculated from the value of the relative humidity, I suggested that it might be possible to forecast the minimum soil temperature for a calm clear night as early as the previous afternoon.