282 ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 
Trees without foliage. 180° in azimuth from Sun’s. 
Albedo of trees 1 
— == —, 1 Obs. 
Albedo of Jupiter 7 
1860, March 28th. Screen of white drawing-paper, painted with “ Flake white." 
Albedo of white paper __ 1 
Albedo of Jupiter —— 1.7? LN 
Screen of black cloth without gloss. 
Albedo of black cloth ` 1- 1 Obe. 
Albedo of white paper 11” 
By an — So made, ys 11th,) I found for the latter a consider- 
ably less value, viz. : — 
Albedo of black cloth o 
= — 3 2 Obs. 
Albedo of white paper 17 SC 
The albedo of dark, weather-worn rocks, dry earth, sand, or gravel, I have found to 
be from 1 to 4 of that of the white paper, or about 4! of that of Jupiter. Referring 
to the numbers given in (51), we are led to the inference that, while the general sur- 
face of the Earth is very much darker than Jupiter, its reflective power nearly resem- 
bles that of the Moon, agreeing with the comparison made by Herschel, before cited. 
According to Lambert, the albedo of the whitest known substance* is 0.423, differ- 
ing but very little from that of the whitest paper, 4 — 0.410. 
Olberst has suggested that fresh-fallen snow may be yet more brilliant; but, from 
actual comparison, I incline to think that the little difference between them is rather 
in favor of the paper. A very pure surface without gloss may be obtained by grinding 
two pieces of chalk upon each other, and afterwards coating them with * Flake" or 
* Chinese" white; still the difference between it and thick white paper, similarly 
coated, is but trifling. 
If we suppose the albedo of the paper used in the foregoing experiments to be 
— 0.4, that of Jupiter will be 0.68, or larger by one half than the reflective power of 
the purest white surface that we can produce artificially. 
Further confirmation of these results is much to be desired, especially when we 
bear in mind the unavoidable errors to which the observations are exposed, and the 
* Kremnitz white, a fine white-lead. t Monatliche Correspondenz, Vol. VIII. 
* 
