16 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Table IV. — Value of Lag in Hours. 
II 
•44 
•42 
•40 
GO 
CO 
•36 
•34 
•32 
•30 
•28 
•26 
•24 
•22 
•20 
Average value ofl 
lag in hours / 
3i 
H 
H 
3f 
4 
Hr 
H 
Hr 
4f or 5 
5 i 
H 
Hr 
No. of days onj 
which average 1 
values are based J 
2 
6 
5 
9 
5 
1 
4 
7 
5 
1 
i 
3 
IY. Connection between ^ . the Relative Humidity, and the 
Number of Degrees Centigrade ( 0 ) which the Surface can 
FALL BELOW THE TEMPERATURE OF THE 4-in. DEPTH BEFORE THE 
Upward Conduction balances the Radiation. 
Table V gives the value of 0 on clear nights of which the relative 
R 
humidity was known compared with the value of ~ The starred figures 
K 0 
are the average of the values actually obtained by observation, the other 
figures are interpolated values. 
Table V. — Values of e in °C. 
Relative 
Humidity. 
Values of §- 4 . 
R 0 
•30 
•32 
•34 
•36 
•38 
•40 
*42 
•44 
90 per cent. . 
80 „ 
70 
60 „ 
8-0 
8*7 * 
9-5* 
10-2 
75 
8-1 
8*9 
9-6 
7-0 
7- 6* 
8- 3* 
9- 0 
6- 5 
7- 0 
7- 7* 
8- 4 
6-0* 
6- 5 
7T 
7- 8 
5- 5* 
6- 0* 
6*6* 
7-2* 
5- 0* 
5*5* 
6T* 
6- 6* 
4- 6 
5- 0* 
5 5 
6T 
Y. Differences between the Air Minimum over Open-Soil 
and Surface-Soil Minimum on Clear Nights. 
Table YI gives the average and greatest and least observed differences — 
(a) On 10 nights when surface froze. 
(b) On 28 nights when surface did not freeze. 
