Telescope.
Telescopes were first constructed in the Netherlands about 1608.
In 1853
Alvan Clark, of
Cambridgeport, Mass., a comparatively unknown portraitpainter, after having experimented from 1846 in grinding lenses, succeeded in turning out a glass superior to any made elsewhere in the world.
He and his sons went on making large and larger instruments, till they ground the 36-inch telescope for the
Lick Observatory, in
California, and the son, Alvan G., made the 40-inch
Yerkes telescope for the observatory of the
University of Chicago, erected at
Williams Bay, Wis. The movable part of the latter, which turns on the polar axis, weighs about 12 tons, and the clock weighs 1 1/2 tons.
The refracting telescopes of the
Naval Observatory, at
Washington, 33 feet long, and at the
Leander McCormick Observatory, University of Virginia, both made by
Alvan Clark & Sons, have a 26-inch aperture.
The largest reflecting telescope in the
United States is at Harvard University, 28-inch mirror.
Other notable telescopes are at Princeton University (
Clark, 23-inch);
Rochester, N. Y. (
Clark, 16-inch);
Madison, Wis. (
Clark, 15.5-inch);
Dudley, at
Albany, N. Y. (
Fitz, 13-inch); University of
Michigan (
Fitz, 12.5-inch); and Middletown University (
Clark, 12-inch).
