146 Scientific Proceedings, Royal Dublin Society. 
Here again we see that both the tub and the open cup show 
the maximum evaporation between 11 a.m. and 2 pm. The 
Piche atmometer does indeed evaporate, if anything, a little 
faster after 2 p.m. than before; but that is probably due to the 
fact that its small mass is much more readily influenced by the 
temperature of the air and by the wind, and no doubt chiefly by 
the latter, as appears from a comparison between Tables 4 and 9. 
The rapid rate of evaporation between 8 and 11 a.m., as compared 
with the much slower rate between 5 and 8 p.m., in spite of the 
much lower temperature of the earlier hours, is remarkable, and 
receives no manner of explanation from the formule we have 
quoted. 
Still more remarkable is the exactly opposite state of things 
in the iron tubes, where the evaporation goes on increasing after 
sunset for some hours after the temperature of the water has 
begun to fall, and is indeed four times as great from 8 to 
11 p.m., and nearly twice as great from 11 p.m. to 8 a.m. as it 
is from 8tollam. The following are hourly averages :— 
Tasie 10.—(114 days.) 
| 8 a.—d p. 5 p.-8 p. 8 p.-11 p. 11 p.-8 a. 
One-foot Pipe. . 2°3 5°6 3°8 ILE 7/ 3 
Two-foot Pipe, . 1:9 4°6 3:0 1:4 Ss = 
‘so 
Three-foot Pipe, . Toy 3°8 2°4 11 50 
TasLE 11.—(15 days.) 
| 8a.—lia.'11a.—2 p.| 2 p.—d p. | 5 p.—8 p. ; p.-11 p.|11 p.-8 a. 
| One-foot Pipe, .| 1:0 25 49 62 | 4-1 1:8 3 
r=¥) 
| Two-foot Pipe, .| 0:8 1:9 4-1 51 | 3:3 15 ae 
| ; ‘4 
| Three-foot Pipe, . 0:8 2-0 3°6 2) 1:2) alpaca 
It is curious how the relative ratios of the quantities evaporated 
in the three pipes vary. Before noon the water lost in the three- 
foot pipe is as great as, or greater than, that lost in the two-foot 
pipe; but afterwards, for the rest of the day, the loss in the two- 
foot pipe is very nearly the arithmetic mean of the losses in the 
