Surron—Study of Evaporation from Water-Surfaces. 159 
Taste 15.—One-foot Pipe. (1.) 5to 8 p.m. 
5 < Median 5 > Median 
{ Relative 
Humidity. 
No. T W E || No. T | W | E 
Spesene | 8) ye 72:8 5-2 Q2er.|| 8 | 81-5 2:8 26gr. 
35-392 | 10 | 67-9 | 36 18 il) woe | ery 22 
40-44% | 8 | 61-4 2°6 14 9 | 76-2 2:9 18 
45-49% 14 | 63:3 2-9 13 1 |) eal 3-6 17 
50-542 | 6 | 643 | 38 12 | eee | Be 15 
Total, | 46 | 65:9 3°5 16 48 | 77-0 2°9 20 
2.) 8 toll p.m. 
35-39 % 4 | 68-1 5-4 Vier.|| 5 | 751 4:2 | 22 
40-442 8 | 619 5:2 12 8 | 76:4 as aly 
Apron) 8 *| | 55:5 3-1 11 g | 74:9 4:6 17 
50-54 % | g | 55-2 2:2 9 8 | 66:9 3°4 11 
55-64 | 15 | 60:3 3-2 9 15 | 71:0 2°6 11 
Total, | 44 59:4 a 10 44 72:4 3°5 14 
Tables 14 and 15 give substantially the same result as Tables 
12 and 13, the only difference being in degree rather than in kind. 
The temperatures of the water in the pipe for the hours considered 
are higher than those of the open cup, and therefore the differences 
of vapour-tension are greater, while the quantities of evaporation 
are less. As with the open cup, when é is less than the median 
the minimum temperature of the water comes with a lower relative 
humidity than when 6 is greater. It is worth while noticing such 
points as these, because they illustrate the complexity of the pro- 
cesses in which evaporation is wrapped up, and the difficulty of 
separating the important agencies from the uninfluential. 
In Table 16 we have the following quantities of evaporation 
corresponding to assigned differences of vapour-tension between 
the temperature of the water and that of the dew-point. 
