Experiments and Observations on the Solar Rays. 365 
from the outer surface of the body together with the undecom- 
posed white light. Also, it can readily be conceived that that 
part of the intromitted light, which is complementary to that 
which has been detained by the inner particles of the body, must 
exist within the body in a free state, and then effect its escape 
from the pores, by that self-repellent power of its particles which 
is known to exist, and is the cause of radiation. 
That a part of the colored light which is discharged from any 
colored opaque body, proceeds from the outer surface of the body, 
there can be little doubt. Procure an opaque body whose celor 
is one of the primary colors of the spectrum, a piece of gold for 
instance, possessing a flat surface highly polished. The greater 
part of the light which is reflected from such a surface, is known 
to be reflected regularly. Throw the sun’s rays obliquely upon 
the polished surface of the gold, and receive the reflected light 
upon white paper, which will be tinged of a yellow color. But, 
the yellow color thus given to the paper by the reflected light, 
will be very faint in comparison to the color of the gold itself{—too 
faint to admit the belief that all the yellow light which is dis- 
‘charged from the gold proceeds from its outer surface; but no 
more vivid than can readily be accounted for, by supposing it to 
be complementary to the light which has been detained by the 
outer particles of the gold. 
_ The brilliant colors of certain solid bodies, such as chromate 
of lead, indigo, é&e., cannot, I think, be explained unless we call 
in to the aid of reflection a copious radiation of colored light from 
the internal parts of these bodies. 
To the opinion that part of the light which enters the sub- 
stance of colored opaque bodies exists within them in a free state, 
and then escapes from their pores by radiation, as caloric does 
from heated bodies, it might be objected, that the discharge by 
the bodies im question of all the light which is not permanently 
detained by the specific attraction of their particles, is instanta- 
neous, but that a heated body requires some time to part with all 
its free caloric. But there is no proof that the discharge by the 
bodies in question, of all their free light, is instantaneous. When 
the color of a bodyceases to make an impression upon the organ 
of vision, that is no proof that no more visible rays are discharg- 
ed from the body. The human perceptions are not always un- 
erring guides in tracing the operations of nature. It is well known 
that a body may feel cool to the touch, and yet, at the same time, 
