144 Scientific Proceedings, Royal Dublin Society. 
(5). Wind- Velocity. 
11 p.—8 a. | 8 a.-ll a. | 11 a.-2p.| 2p.-d p. | 5p. p. | 8 p.ll p- 
| 
Oct., BO ||| G2 7:3 81 5:6 Be |) 
Nov., Ax | + ge 7:8 75 5:0 4:3 
Dec., Mi |) GHG 6-3 6-3 5°8 5-1 5 
| oa 
Jan., 3:1 5-8 6-7 6-8 3°7 a1 | Ue 
a) 
Feb., 3:4 5:9 56 5:1 3+2 3:0 2 
Mar., 4:5 6:5 70 6°5 4-7 4-1 A 
Mean, 3°7 6-3 6:8 6-7 4-7 40 | 
The mean vapour-tensions at the temperature of the water and 
the temperature of the dew-point, proper to Table 5 (2) and (8), 
are— 
11 p.-8 a. | 8 a.-ll a. | 11 a.—2 p.| 2p.—dp. | dp.-8p. | 8 p.-ll p. | 
| 
Water, = 652 744 *806 804 -760 
Dew 5 
= 6) er 29 296 ° . J [=| 
Point, \ 342 356 339 328 335 339 (8 
If now we substitute in Stefan’s formula values of P, p’, p’’ 
from Table 5 (4), (2), (38), we deduce a practically constant rate. 
of evaporation, at all events between sunrise and midnight, con- 
trary to all experience. Again, assuming that the air-movement 
inside the screen containing the tub is one-third (a liberal estimate) 
of that at 45 feet, we get the following relative numbers by 
Fitzgerald’s formula :— 
TABLE 6. 
| 8 a.-ll a. | 11 a.-2 p. | 2 p.-d p. | 5 p.-8 p. | 8 p.-1l p. | 
| 
Calculated 030 "043 050 042 036 inch. 
Observed ) +0165 + °010 -000 — 004 — +005 inch. 
MANUS 
Calculated ) 50 23 0 10 14 per cent. 
These are large differences, and it may, I think, be reasonably 
claimed that they throw a considerable element of doubt upon the 
physical reality of Fitzgerald’s formula. Nor are the averages 
