302 Proceedings of Royal Society of Edinburgh. [sess. 
lost by the earth every year. This is perhaps the most interesting 
of all results dedueible from measurements of earth temperatures. 
There is, however, another direction of enquiry suggested by 
the comparison made in the early part of the present paper, and 
that is to estimate the accumulation of heat at different times of 
year throughout the rocky stratum. When this is done a com- 
parison may then be made between the heat so accumulated and 
the available quantity of energy according to Langley’s estimate. 
Thus we should expect to find that during a particular month of 
the year there was more heat accumulated in the rocky stratum 
than during any other month. This will be due to the excess of 
radiation supplied in the summer months. The relation between 
these two quantities may possibly lead to an approximate measure- 
ment of the emissive power of the earth. 
In the calculations which follow I have used as the fundamental 
data the earth- temperatures during the eight years beginning 
October 1879. These were published by Piazzi Smyth (Trans. 
Roy. Soc. Edin ., vol. xxxv.), and were discussed by him in con- 
nection with sun-spot periodicity. There are four thermometers 
in all, distinguished as bios. 1, 2, 3 and 4, their depths being 
respectively 0*8763, 1*4478, 3*238, 6*35 metres. In the following 
table the mean of the eight monthly means for each thermometer 
is given for every month throughout the yearly period. 
Eight year Means of Earth Temperatures ( Falir .). 
Therm. 1. 
Therm. 2. 
Therm. 3. 
Therm. 4. 
Calculated 
Surface 
Temp. 
October, 
46*445 
48*748 
48*52 
46*863 
45*06 
November, 
43*785 
45*558 
47*655 
47*136 
39*30 
December, 
40*284 
42*611 
46*345 
47*146 
36*32 
January, 
39*859 
41*069 
44*983 
46*908 
36*08 
February, 
39*28 
40*515 
43*983 
46*521 
37*46 
March, . 
39*661 
40*616 
43*414 
46*104 
39*78 
April, 
41*641 
41*628 
43*181 
45*728 
43*30 
May, 
45*108 
44*055 
43*646 
45*450 
48*22 
June, 
49*993 
47*926 
44*863 
45*36 
53*56 
July, 
52*995 
50*78 
46*498 
45*533 
57*00 
August, . 
53*12 
51*588 
47*873 
45*896 
56*46 
September, 
51*48 
51*08 
48*693 
46*443 
51*78 
