rincipal products of
Clark & Sons. Gradually they extended the width of their lenses,
gaining with each increase of diameter a rapidly increasing power of
penetration. At last they produced for the Royal Observatory of
Pulkova a twenty-seven-inch objective, which was, down to the early
eighties, the master work of its kind in the world. It was in the
grinding and polishing of their lenses that the Clarks surpassed all
men. In the production of the glass castings for the lenses, the
French have remained the masters. At the glass foundry of Mantois, of
Paris, the finest and largest discs ever produced in the world are
cast. But after the castings are made they are sent to America, to be
made into those wonderful objectives which constitute the glory of the
apparatus upon which the New Astronomy relies for its achievements.

It was in the year 1887 that the Lick Observatory on Mount Hamilton,
of the Coast Range in Southern California, was completed. The lens of
this instrument is thirty-six inches in diameter. Nor will the reader
without reflection readily realize the enormous stride which was made
in telescopy when the makers advanced from the twenty-seven-inch to
the thirty-six-inch objective. Lenses are to each other in their power
of collecting light and penetrating apace as the squares of their
diameters, and in the extent of space explored as the cubes of their
diameters.

The objective of the Pulkova instrument is to that of the Lick
Observatory as 3 is to 4. The squares are as 9 is to 16, and the cubes
are as 27 is to 64. This signifies that the depth of space penetrated
by the Lick instrument is to that of its predecessor as 16 is to 9,
and that the astronomical sphere resolved by the former is to the
sphere resolved by the latter as 64 is to 27--that is, the Lick
instrument at one bound revealed a universe _more than twice as great_
as all that was known before! The human mind at this one bound found
opportunity to explore and to know a sidereal sphere more than twice
as extensive as had ever been previously penetrated by the gaze of
man.

Nor is this all. The ambition of American astronomers and American
philanthropists has not been content with even the prodigious
achievement of the Lick telescope. In recent years an observatory has
been projected in connection with the University of Chicago, which has
come almost to completion, and which will bear by far the largest
telescopic instrument in the world. The