of Edinburgh, Session 1881-82. 
829 
Time. 
Grammes Water Distilled. 
From 
To 
16 th. 
17 th. 
18th. 
9 
10 
... 
78*1 
10 
11 
58*8 
70*25 
82*4 
11 
12 
69*5 
69*7 
82*8 
2 
3 
73*2 
65*5 
71*6 
3 
4 
... 
57*9 
64*8 
Taking the average performance on the 16th and 17th, which 
were comparatively cool, we find that 70 grammes, or 0T542 lb. of 
water was distilled per hour, and on the 18th, a comparatively hot 
day, the amount was 81 grammes, or 0T784 lb. per hour. 
Setting aside cloud, the chief perturbing agent is wind. During 
the three days we were fortunate in having considerable varieties of 
weather. On the 16th, with a calm afternoon, the mean rate between 
two and three o’clock was 1*221, and on the 17th, when it w T as 
breezy, it was 1*087, or about 10 per cent. less. The breezes which 
occur on the Nile are cool from the north, and are variable in 
strength. On the three days mentioned the force was never greater 
than from 2 to 3, and what there was was always more or 
less gusty. We have seen that the mean rate between 2 and 
3 p.m. on the 16th was 1*221, and the temperature of the air at 
2 p.m. was 95° F. ; while on the 18th the rate was 1*204, with a 
temperature of 105° at 2 p.m. On the latter day there was a 
fresh breeze in the afternoon, while on the former it was calm. If 
we consider that the lowering of the rate was wholly due to the 
wind, it appears that air of 105° F. in moderate motion cooled as 
much as stagnant air of 95° F. It is, however, impossible to be 
sure that some of the lowering may not be due to alteration in the 
absorptive power of the air. 
The air was always excessively dry. At 2 p.m. the dry and 
wet bulb thermometers registered, on the 16th, 95° and 62*5° ; on 
the 17th, 94° and 66*2° ; and on the 18th, 105° and 68° F. There- 
fore the difference between the wet and dry bulbs ranged between 
4 s 
VOL. XI. 
