Sutron—ZInfluence of Water- Vapour upon Nocturnal Radiation. 38 
during 1896 and 1897, the mean differences—(1) between the 
minimum radiation temperatures at heights of 3 inches and 
0 inches; and (2) between the minimum radiation tempera- 
tures at heights of 38 feet and 19 feet, compared with the 
absolute and relative humidities at 2 a.m. In both cases the 
thermometer nearest the ground reads the lower :— 
Dew-Point Relative 
at 
m3—Mo- M3g—M19- | Humidity at m3—Mo. M3g—119- 
2 a.m. a.m. 
| 
fo} fo} ° fo} 
Under 25° 5-1 2°8 Under 40 °/, 5:7 1°5 
25°-29°-9 53 2°6 40°/,-49 ,, 5°6 1°8 
30°-34°°9 5°3 2-2 50,, -59 ,, 51 1°8 
35°-39°°9 5:2 Qe 60 ,, -69 ,, 5:1 2-1 
40°-44°-9 4-5 11) U0 5, =O) 56 4-7 2-0 
45°-49°-9 4°8 1:3 80 ,, & over. 3°9 1°5 
59°-54°-9 4-2 0:9 
55 and over. 4°3 1-0 
An explanation of these last results is not likely to be simple, 
nor indeed does it strictly belong to the subject-matter of this 
paper. 
Probably radiation, convection, and conduction have each 
an equally important share in producing them; but beyond 
mentioning this, I venture no further comment. 
