Physics and Chemistry. 217 
this ratio rests on numerous preliminary experiments and upon 
considerations, the details of which are out of place here. 
water ; the unequal diathermancy of the air in spite of its apparent 
serenity; the partial absorption of reflected heat by the lower 
i e 
ul 
certain inferences of interest to physics and meteorology. 
_ (1.) The highest proportion of reflected heat was 0°68 of the 
incident heat. This maximum was twice observed with a solar 
0°3 is very naturally more frequent for elevation under or about 
16° 35’. he proportion of heat reflected from water when the 
sun is above 30° elevation is inappreciable. 
* ini he proportion between the heat 
reflected and the elevation of the sun has not been satisfactorily 
mg layers of air of variable thicknesses before reaching the appa- 
Tatus, 
(3.) The proportion of reflected heat arriving at distant stations 
does not always increase with the fall of the sun toward the hori- 
zon, For very slight solar elevations this proportion was many 
times less than it was at those more considerable, for the reason 
& thick stratum : e absorption which it s etween 
the of reflection and the station compensates therefore for 
e dence. 
4.) The proportion of heat reflected, almost without exception, 
ted j 
diminishes directly. The combination of these two hig veneronpe 
ences meet at a maximum corresponding to 4 certain elevation © 
the sun, which fact has been verified by many observations. 
