gleaming in the light of dimly-shaded lamps. The room requires to be as dark as possible, and the lamps are used merely for illuminating the interior of the telescope and the face of the clock. As your eye gets accustomed to the gloom, you probably find the observer stretched on his back upon a couch, which is movable, so as to bring his eye close to the telescope. He is situated between two huge stone pillars that serve as supports for the transit-circle, which is the grand instrument of the regular observatory. You may form a pretty fair conception of the instrument, if 3^ou suppose a pair of carriage-wheels, with their connecting-axle laid across the tops of the pillars, the axle resting upon two metal supports on which it turns. The telescope is then to be conceived as fixed across the middle of the axle, so that it is hung precisely like a cannon on its carriage. It can only move on its axis, up and down; it can turn neither to the right nor the left. On examining the rim of the wheel, you will find an inlaid narrow band of gold all round, and on this are engraved very minute lines, with intervals of two seconds. When the telescope is elevated to a particular star, the circle, of course, turns round, being fixed to the axis; and the observer, when he has placed the star exactly on a spider's line in the centre of the field of view, leaves the eye-glass of the telescope, and views, with a powerful compound microscope, the divided limb. He marks what particular division comes
