424 Transactions of the Boyal Society of South Africa. 
From this it will be seen that it takes 40 minutes for the gauge at 
33 inches to fall 16 degrees, and only 25 minutes for the gauge at 
15 inches. The nearer gauge, however, continues to fall for fully 
50 minutes, and reaches a lower temperature than the final stationary 
temperature of the farther gauge. The results in this case are fairly 
representative, and will no doubt suffice to give a general idea of what 
goes in. 
It would have been much more interesting if each of the experiments 
noted in this paper could have been continued for another 50 minutes, 
the first 50 in a falling temperature, and the second after the stationary 
temperature was reached. Unfortunately, however, I was only able to 
get the use of the fan for an hour each day, with one or two exceptions ; 
and consequently could not do this desirable thing. I hope, however, 
before long, to commence a series of similar experiments in which the 
water at first shall be cold instead of warm. Meanwhile, here are the 
results in a case in which the water was cooled nearly to its final 
temperature before commencing the experiment : — 
Dry bulb 63-0° 
Dew-point 38*1 
Humidity, per cent 40 
Current velocity, 13 inches from fan per minute 1,004 ft. 
>) >) 31 ,, ,, 725 ,, 
Initial temperature of water 58'8° 
Final temperature of water 15 inches from fan 58'2 
33 „ 58-9 
Loss by evaporation 15 inches from fan 55*2 gr. 
33 „ 42-4 
Nothing in the large Table at the end is very suitable for comparison 
with this. Perhaps the eighth line from the bottom is the best to take. 
The comparative results for the gauges at 15 inches from the fan are : — 
Dry bulb 58-8° 63-0° 
Vapour pressure at temperature of dew-point ... 0*216 inch 0*230 inch 
,, „ final temperature of water... 0*418 ,, 0*436 ,, 
Humidity, per cent 44 40 
Current velocity per minute 872 feet 1,004 feet 
Initial temperature of water 69*2° 58*8° 
Loss by evaporation 53*6 gr. 55*2 gr. 
In each case the vapour-pressure difference is nearly the same, i.e., 
0*202 inch in the one case, and 0*206 in the other, while the relative 
