Professor Huggins, we read:

"That the nucleus of a comet can not be in itself a dark and solid
body, such as the planets are, is proved by its great transparency;
but this does not preclude the possibility of its consisting of
_innumerable solid particles_ separated from one another, which, when
illuminated by the sun, give, by the reflection of the solar light,
the impression of a homogeneous mass. It has, therefore, been
concluded that comets are either composed of a substance which, like
gas in a state of extreme rarefaction, is perfectly transparent, or
of _small solid particles_ individually separated by intervening
spaces through which the light of a star can pass without
obstruction, and which, held together by mutual attraction, as well
as by gravitation toward a denser central conglomeration, moves
through space _like a cloud of dust_. In any case the connection
lately noticed by Schiaparelli, between comets and meteoric

[1. "The Heavens," p. 239.

2. Note to Guillemin's "Heavens," p. 261.]

{p. 69}

showers, seems to necessitate the supposition that in many comets a
similar aggregation of particles seems to exist."[1]

I can not better sum up the latest results of research than by giving
Dr. Schellen's words in the work just cited:

"By collating these various phenomena, the conviction can scarcely be