18 
Proceedings of the Royal Society of Edinburgh. [Sess. 
a total period of 14 hours, — then the value of /3 corresponding to any 
R 
value of ^ may he found as follows : — 
a = = '36 (say). 
R, 
R, 
The lag is 4 hours for this value of from Table IV. The total period 
is 14 hours. 
/? = 
14 -4_5 
14 “ 7 
.-. a/3 = T of *36 
= •26. 
.-. 1 — a/3 = 74 
R 
and so on for other values of the lag and ~ . 
xl 0 
Table VII gives the average values of 1 a/3 for various values of 
Table VII.— Values of 1 - «0. 
Values of . 
K 0 
•44 
•42 
•40 
•38 
•36 
•34 
•32 
•30 
•28 
•26 
•24 
Average value of 1 - a# . 
•66 
•68 
•70 
•72 
•74 
1 
•76 
00 
j>- 
•80 
•82 
•84 
•85 
We now have everything necessary to compute the value of R 0 from 
the forecast equation. 
For example, if 
M 0 = 18° C. 
M 4 =12° C. 
R =a= ' 40 ’ 
K 0 
relative humidity = 80 per cent. 
Then, from Table V, 
0 = 6-0°, 
1— a/3 = -70. 
p _ M 0 - M 4 + 0 
* 1 — a/3 
18-12 + 6 
•70 
.12 
= 171° C. 
and from Table VII, 
