the
University and an enthusiastic observer of the heavens,--not a
descriptive observer like Herschel, but a measuring observer like Sir
George Airy or Tycho Brahe. He was, in fact, a worthy follower of Tycho,
and the main work of his life is the development and devising of new and
more accurate astronomical instruments. Many of the large and accurate
instruments with which a modern observatory is furnished are the
invention of this Dane. One of the finest observatories in the world is
the Russian one at Pulkowa, and a list of the instruments there reads
like an extended catalogue of Roemer's inventions.

He not only _invented_ the instruments, he had them made, being allowed
money for the purpose; and he used them vigorously, so that at his death
he left great piles of manuscript stored in the national observatory.

Unfortunately this observatory was in the heart of the city, and was
thus exposed to a danger from which such places ought to be as far as
possible exempt.

Some eighteen years after Roemer's death a great conflagration broke out
in Copenhagen, and ruined large portions of the city. The successor to
Roemer, Horrebow by name, fled from his house, with such valuables as he
possessed, to the observatory, and there went on with his work. But
before long the wind shifted, and to his horror he saw the flames
coming his way. He packed up his own and his predecessor's manuscript
observations in two cases, and prepared to escape with them, but the
neighbours had resorted to the observatory as a place of safety, and so
choked up the staircase with their property that he was barely able to
escape himself, let alone the luggage, and everything was lost.

[Illustration: FIG. 77.--Diagram of equatorially mounted telescope; CE
is the polar axis parallel to the axis of the earth; AB the declination
axis. The diurnal motion is compensated by motion about the polar axis
only, the other being clamped.]

Of all the observations, only three days' work remains, and these were
carefully discussed by Dr. Galle, of Berlin, in 1845, and their
nutriment extracted. These ancient observations are of great use for
purposes of comparison with the present state of the heavens, and throw
light upon possible changes that are going on. Of course nowadays such a
series of observations would be printed and distributed in many
libraries, and so made practically indestructible.

Sad as the disaster was to the posthumous fame of the great