186 Prof. J. Brocklesby on the Influence of Color on Dew. 
Colors arranged according to the amount of dew gained : 
lst Ex. - 2d Ex. 3d Ex. 4th Ex. | Sth Ex. ; Average. 
grs. 
Blue, White. Blue. Blue. Blue, Green.| Blue, ; ‘Blue, 17:2 
Yellow, Green, 2 |Green, Yellow, 2 |Yellow, White./Yellow, White. § White, 16-6 
Black, Black, White. § |Red, Green, } hite. Yellow. /Yellow, 16:2 
Red. Black. Gr . 
Black. 
Red. 
® 
2 
2o 
Oo 
5 
SSS Eee eran 
It is seen in the experiments just detailed, that among the differ- 
ent colors the blue and red alone follow an invariable order; the 
former always occupying the highest and the latter the lowest 
rank ; and that this is true not ithstanding the cards were changed 
after the third trial : a fact-which shows that this law follows the 
pigment and not the card. But does the law attach to the color 
or the coloring matter. The'latter appears to be the case. In Prof. 
Bache’s essay on the influence of color upon radiation, a list is 
given of twenty-five substanées, arranged in the order of their ra- 
diating powers. Prussian blue ranksthe second, indigo the eight- 
eenth, and vermilion the fifteenth.» Prussian blue therefore, ra- 
diating more than vermilion, should contract more dew as accords 
with the fact. But it is evident that this effect is produced by 
the material of the pigment and not by the color, inasmuch as 
indigo has a less radiating power than vermilion, and consequent- 
ly it would give but comparatively little dew. A fact which is 
shown in Table A, where the blue ranks very low in the scale of 
colors. 
The results developed in these investigations afford no support 
to the assertions of Dr. Stark, that dark colors are more favorable 
than light to the deposition of dew; but, to their full extent, 
lead to the inference that color has no coritrolling power in this 
icular. 
_ It is with much satisfaction that I have perceived the results of 
my humble researches, to accord with those, which Prof. Bache 
deduced from -his elaborate investigations; wherever a compati- 
son could be : s with him I find, that color is not a 
determining quality in the radiation of non-luminous heat, that 
vermilion possesses a low radiating power, and that while Prus- 
sian blue possesses this property in a very high degree, indigo 
ranks amid the lowest on the scale. In Prof. Bache’s experi- 
ments the rate of cooling was the test of the radiating power, in 
those just detailed, the amount ef dew is the criterion, Now, 
without asserting that the non-influence of color upon radiation 
is fully established, it is certainly a circumstance worthy of con- 
sideration, that two independent modes of analysis have led to 
the same conclusions. ’ 
a 
