Surron—Study of Evaporation from Water-Surfaces. 145 
for each month very much more exact. The following are daily 
averages for each month for the whole intervals between 
8 a.m. and 11 p.m. :— 
TABLE 7. 
Evaporation 
P p py Wind 
Observed | Computed | O —C 
inch inch inch M. per H. inch inch inch 
Oct, 26-093 637 "236 6°3 "258 "229 + *029 
Nov., "072 “716 “315 6:3 238 "229 + °009 
Dec., 020 812 346 6-0 246 260 — Ola 
Jan., 036 857 408 5:2 214 240 — 026 
Feb., 071 756 “399 4°6 172 179 — 007 
Mar., 099 664 *364 5'8 “169 167 + 002 
Mean, 26-065 736 “3389 57 216 *216 
Using these numbers, Stefan’s formula, as before, gives a 
practically constant result month after month, mainly because 
(P — p”) / (P —p’) is very nearly constant under prevailing summer 
conditions at Kimberley. 
The quantities of evaporation from the tub, the Piche 
atmometer, and the open cup, for the periods dealt with in 
Tables 3 and 4, give pretty much the same sort of result as 
Table 5. 
TasLe 8.—(114 days.) 
| 8 a.-d p. 5 p.—-8 p. | 8 p.-ll p. | 11 p.-8 a. | 
Euiby sn 012 008 006 005 inch per hour. 
Piche, . 4:2 2°4 1°8 1-2 units per hour. 
Open Cup, 18°7 S7/ 57 3°6 grains per hour. 
Taste 9.—(15 days.) 
8a.—lla.|11a.—2 p.| 2p.—d p. | 5 p.-8p. 8 p--ll pou p.—8 a. 
Ain, 9 Gt) Ou 014 012 005 007 -004 | inch per hour. 
Riche, . 3°7 Dell 5-2 2-4 il<i7/ cil units per hour. 
Open Cup,| 14:4 29°6 24:5 9:5 5'8 3°0 grains per hour. 
