Prof. J. Brocklesby on the Influence of Color on Dew. 183 
Notwithstanding every precaution to obtain uniformity in all es- 
sential particulars, the four exposed surfaces contracted unequa 
sonia of dew ; the difference between the extreme averages 
ing 1s. —23°5 gts. =2 grains in four experiments. The 
oe tb of the extremes in the first, second, and last four ex- 
| periments, as given in table A, is as follows : 
“9 grs. 
First four, ¥ . : ‘ 47-5 —43-25=4-25 
= 
i>*) 
of 
= 
ERs 
f From this it is byicun, that the differences in the amount of 
- deposited moisture, developed in the first course of experiments, 
(4 were not fully due to the influence of color. Latent causes also 
: conspired to produce these discrepancies, and the extent of their 
influence is eliminated by the second series of experiments. If 
re this is suas by the difference between the extreme averages, 
i and this subtracted from the corresponding differences in 
| table A, A teen oti are represented by the following weights, 
bn grs.; residual phenomena, which iMnar be 
bate, eit Se Z the influence of color, or considered as ae 
ts of experiment, to which all human investi- 
met are subiée 
In table B, it. vill be observed, by comparing R,S, T, and U, 
with each other i in the several experiments, that ‘the anount of 
moisture deposited follows no rule, each surface in its turn ranging 
from the highest to the lowest point of the scale. Such fluctua- 
ting results must be the effects of predominating inconstant cau- 
ses. ‘The same fact is discovered, as before stated, in the first 
series of experiments, upon comparing together the red, kame 
! and blaek. Here if color has any ‘effect, it is entirely di 
by the prevalence of more potent fluctuating influences. “Phe 
invariable superiority however, maintained by the yellow and 
white over the black, indicates the existence of one or more fix 
Operating causes, not visiting one s surface to-night, and another the 
next ; but attached totheir own particular surface. 
The only assignable, eonstant’ causes, exclusive of eoloriig 
matter, are-the differences in the density of the threads composing 
the surfaces, (to which allusion has been made,) and color. * But 
the first cause existed in the second series of experiments, and 
was unable to presefve any regularity in the variations. More- 
over, between the black and white even this difference in*the 
density of the thread searcely’ existed, inasmuch as the equal 
surfaces of the black and white weighed very heatly the same, 
before any shreds were swperadded. Under this view of the 
subject therefore, color alone would appear to have operated in 
producing the constant differences observed in the amount of de- 
posited moisture as recorded in the first table, had the investiga- 
tion been confined to the first course of experiment. But the 
