The Scientific Proceedings of the Royal Dublin Society Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 Excerpt: ... to the north side of the equatorial tower. The East Wing is the transit room, for which 1 am now preparing a 5-inch transit circle, and which is supplied with a transit shutter of novel construction. See below. The West Wing is intended for physical research and experiments, and will contain a siderostatic telescope, of peculiar construction, which I have the pleasure of exhibiting this evening and various appliances of spectroscopic and general researches. The Dome is of fifteen feet diameter, constructed of wrought iron ribs and purlins, covered with--1st. A network of wire, interlaced. 2nd. A thickness of sailcloth or canvas. 3rd. A layer of felting; and 4th. A second covering of sailcloth or canvas, well painted. The Dome (Fig. 8.) has a cast-iron sole plate, planed truly flat on the lower side, and the wall is capped with a cast-iron wall plate, having ribs cast in it, and accurately planed, and between the wall plate and sole plate roll eight rollers carefully turned to a conical form. This set of wheels or rollers, coupled together by a wrought-iron framework, constitute what is technically called a live ring; and as all the friction is of that character called rolling friction, and not sliding, the tractive force necessary to drive the dome round is extremely small. Lateral rollers are applied to prevent the Dome getting out of centre. One important feature of this system of mounting revolving Domes is, that as there are no bearings or pivots there is nothing to clog or get stiff, and the Dome works as well (if only kept moderately clean) after ten years as when first erected. The Great Domes for Vienna Observatory I mounted on Fig. 8. this principle. Three of these were of 27 feet diameter, and one of 45, i.e., the largest revolving Dome in existe...