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. 1844 Excerpt: ...of reference: --To construct an oval, the width A B being given. Bisect A B by the line c D, cutting A B in E. From E, with the radius E A, draw a cirole cutting c D in P. From A raid B draw lines through F, and produce them indefinitely. From A and B, with radius A B, draw arcs cutting the last two lines in a and H. From r, with radius v a, describe the arc a H, to meet the aros A a and B H, which will complete the oval. Now in Fig. 597 it will be observed that only the width is given, whilst the depth at D is found by the radius of the arc drawn from p. In Fig. 596, however, the height of the drain, as well as the width, is given. In this drain the span is 3 feet and the height 4 feet 6 e inches. The upper arch is a semicircle of 18 inches radius, and the lower curve is the third portion of a oirole of 10 j inches radius, the centre of which is of conrse set off on the centre line at the distance of the radius from the bottom. These two curves are united by arcs struck with a radius of 4 feet 10) inches, the centre being on the springing line produced. The upper arch in this example is formed of two 44-inch rings, with occasional whole bricks laid as headers, or bricks of a wedge-like form purposely moulded. The sides of the drain are worked as rough arches in whole and half brick, the half brick being of course half in appearance only, the whole brick lying in the direction of the drain. The lower arch is formed of bricks purposely monlded to the form, by which means the closest possible joint is obtained in that part of the drain through which the sewage is passing, and which should therefore be rendered absolutely impervious tc water. In relation to bricks purposely moulded as superseding rubbed bricks, we extract the following passage from Mr. Gilbert ..