Evaporation in a Current of Air. 
419 
In the first few trials the gauges were placed opposite the lower edge 
of the fan, the wind velocity being measured opposite the centre of the 
fan. The following are two typical results : — 
Dry bulb 82-0° 73-6° 
Dew-point 33-4 34-8 
Humidity, per cent 17 24 
Current velocity 14 inches from fan in feet per min. ... 953 976 
30 „ „ ... 750 734 
46 „ „ ... 451 584 
Final temperature of water 16 inches from fan 72-0° 67*0° 
32 „ 71-8 661 
48 „ 71-9 66-1 
Loss by evaporation 16 inches from fan 56*8 gr. 46'4 gr. 
32 „ 76-0 56-8 
48 „ 69-6 54-4 
Since the loss is greater at a distance of 32 — and even at 48 inches — 
than it is at 16 inches, it is quite clear that the effective strength of the 
air current cannot be as great at the lesser distance as it is at the greater 
ones. This was proved by the following observations : — 
Dry bulb 81*0° 
Dew-point 40-5 
Humidity, per cent 24 
Final temperature of water in still air 79-5 
,, 12 inches from fan 73*0 
24 „ 730 
36 „ 72-5 
48 „ 73-0 
Loss by evaporation in still air 12-8 gr. 
,, 12 inches from fan 48*8 
24 „ 56-8 
36 „ 59-2 
48 „ 57-6 
In this instance the water-level was opposite the lower edge of the fan, 
as before. When the anemometer was level with the water its indications 
were — 
10 inches from fan 132 feet per minute 
22 „ 380 
34 522 ,, 
46 „ 424 
