en there was a pause. Though the zodiac continued to be swept
by many observers, a period of more than thirty-eight years went by
before the fifth asteroid was found. The cycle of these discoveries
strikingly illustrates the general movement of scientific progress.
First there is a new departure; then a lull, and then a resumption of
exploration and a finding more fertile than ever. It was on the night
of the eighth of December, 1845, that the German astronomer Hencke
discovered the fifth asteroid and named it Astraea. After a year and a
half, namely, on the night of the first of July, 1847, the same
observer discovered the sixth member of the group, and to this was
given the name Hebe. On the thirteenth of August in the same year the
astronomer Hind found the seventh asteroid, and named it Iris. On the
eighteenth of October following he found the eighth, and this was
called Flora. Then on the twenty-fifth of April, 1848, came the
discovery of Metis, by Graham. Nearly a year later the Italian De
Gasparis found the tenth member of the system, that is, Hygeia. De
Gasparis soon discovered the eleventh body, which was called
Parthenope. This was on the eleventh of May, 1850.

Two other asteroids were found in this year; and two in 1851. In the
following year _nine_ were discovered; and so on from year to year
down to the present date. Some years have been fruitful in such finds,
while others have been comparatively barren. In a number of the years,
only a single asteroid has been added to the list; but in others whole
groups have been found. Thus in 1861 twelve were discovered; in 1868,
twelve; in 1875, _seventeen_; in 1890, fourteen. Not a single year
since 1846 has passed without the addition of at least one known
asteroid to the list.

But while the number has thus increased to an aggregate at the close
of 1890 of three hundred and one, many of the tiny wanderers have
escaped. Some have been rediscovered; and it is possible that some
have been twice or even three times found and named. The whole family
perhaps numbers not only hundreds, but thousands; and it can hardly be
doubted that only the more conspicuous members of the group have ever
yet been seen by mortal eye.

A considerable space about the centre of the planetary zone between
Mars and Jupiter is occupied with these multitudinous pigmy worlds
that follow the one the other in endless flight around the sun. It is
a sort of planetary shower; and it can hardly b