diameter, and the feebleness of its light, seemed to preclude the hope
that, if it were attended by satellites of the same dimensions in
proportion to its own magnitude as those of the satellites of Jupiter
and Saturn in proportion to _their_ magnitude, they could be descried by
any human observer. The patient, persevering, reverent temper of
Herschel took no account, however, of any discouraging or unpropitious
circumstances. What he did was to substitute for telescopes of the
ordinary construction the new and gigantic forty-foot tube already
described; and, thus, with unremitting vigilance and intense zeal, he
arrived at the discovery (between January 4, 1787, and February 28,
1794) of the _six_ satellites of Uranus; in other words, he revealed to
man the completeness of a new system,--a system which will always be
identified with his name.

* * * * *

Those singular meteors, the comets, which flash through heaven with long
trails of light, and of old astonished the nations as if they were
harbingers of some overwhelming calamity, were also the frequent
subjects of our astronomer's investigations. He brought some of his fine
and powerful instruments to bear on a comet discovered by Mr. Pigott in
1807, and closely and carefully investigated its physical constitution.

The nucleus, or head, was circular and well determined, and evidently
shone by its own light. Very small stars seemed to grow pale, "to hide
their diminished heads," when seen through its _coma_ or tail. It is
true, however, that this faintness may have been only apparent, and due
to the circumstance of the stars being projected on a luminous
background. Such was Herschel's explanation. A gaseous medium, capable
of absorbing sufficient solar radiance to efface the light of some