178 Some further Observations on Earth Temperatures. 
below that of the earth at 1 ft. During the six days (Jan. 25th- 
30th, 1895), the mean temperature of the air averaged 12°18° 
daily helow that of the 1 ft. thermometer, a difference of nearly 
4:1° greater than that in 1894. During the same periods the 
1 ft. thermometer fell, in 1894, from 41°6° to 35:8°, a fall of 
5°8° or 0°94° daily ; and, in 1895, from 87° to 34:9°, a fall of 
2°1° or 0°35° daily. The fall of the 1 ft. thermometer as com- 
pared with the difference between it and the mean daily tem- 
perature was, in 1894, 1° fall to 8-6° difference, and, in 1895, 
1° fall to 34-8° difference; a ratio not one quarter as great as that 
of the previous year. 
During the same periods the mean daily difference between the 
temperature of the air and that indicated by the thermometer at 
4 ft. depth was 12°3° in 1894, and 17-2°in 1895. Allowing three 
days for the retardation of movement of the 4 ft. thermometer, it 
fell, between Feb. 20th and 26th, 1894, from 48:2° to 41°8°, a 
fall of 1:4°, or 0:23° daily. Between Jan. 28th and Feb. 38rd, 
1895, it fell from 41°2° to 40:1°, a fall of 1-1°, or 0:18° daily. The 
ratio of the fall of the 4 ft. thermometer to the difference be- 
tween it and the mean temperature of the air was 1° to 52°8° in 
1894, and 1° to 95°5° in 1895. Thus the protective effect of the 
snow against cooling of the ground is, as we might expect, less 
manifest at a depth of 4 ft. than at that of only 1 ft. 
In order to render the comparison with 1894 stricter, I have 
taken above only the first six days of the present frost; but if we 
take the whole period from Jan. 25th to the present date for 
comparison with the six days (Feb. 17th to 22nd, 1894) the 
figures come out still stronger. During the period of twenty-five 
days (Jan. 25th to Feb. 18th) the mean temperature of the air 
fell below that of the 1 ft. thermometer, on an average 10°65° 
daily. During that period the 1 ft. thermometer fell from 37°6° 
to 32°6°, a fall of 4:4°, being at the rate of 0°17° daily, or 1° for 
62°6 day degrees of difference, against 0°94° daily, or 1° to 86° 
of day difference during the frost of 1894. Allowing, as before, 
three days for the retardation of the 4 ft. thermometer, it was, 
from Jan. 28th to Feb. 18th, on an average 16-6° above the 
mean temperature of the air. During that period it fell from 
412°, on Jan. 28th, to 88°3° on Feb. 19th, a fall of 2°9°, being 
at the rate of 0:14° daily, or 1° to 120-8° of day difference, against 
0:28° daily, or 1° to 52°8° of difference in 1894. 
In these remarks, what I have called the ‘‘ mean daily tem- 
perature” is the mean between the highest and lowest readings 
of a Six’s registering thermometer during the previous twenty- 
four hours, taken at 9 a.m, daily, and referred to the previous 
day. It is probably somewhat higher than the true mean, since 
at this time of year the night is longer than the day. 
After reading the earth thermometers, care was of course 
