TELESCOPES

Telescopes are of relatively recent origin; the ancients were forced to make their observations without them, which makes some of their conclusions all the more remarkable. There is considerable evidence that the builders of the Great Pyramid employed the “Grand Gallery” for astronomical observations (see “The Great Pyramid of Egypt,” in the present series), and other devices were employed. But no telescopes of any great power of magnification existed before the last century, while our present marvelous instruments of precision are the evolution of the present century.

Telescopes are of two kinds: refracting and reflecting. Any small telescope exemplifies the former; the incoming light-rays are focussed by a series of lenses, and directly observed by the eye. In the employment of reflecting telescopes, however, another principle is employed: the incoming light-rays are caught and reflected by means of a curved mirror, and focussed on a lens, which in turn is inserted in an elaborate eye-piece, in which the light-rays are magnified and measured. Some of the modern instruments have a forty or more inch aperture, and are capable of enormous powers of magnification.