Book Description
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. 1828 Excerpt: ...not be so pleasant to the eye, but, if well executed, it could not be disagreeable. If the ends were made to form spirals, as in Jig. 3, and a wall erected above the arch, as this wall could only be made to coincide in three points at most with the face of the arch, no regular form of work could be introduced so as to connect the wall to the ring-stones. To form the developement of the intrados of the oblique arch, with spiral or winding joints, and thence to find the plan of the developement or intrados. Let AC, Plate XVII, be the inner diameter of the face of the ringstones; upon AC describe the semi-circular arc ABC, and find its developement upon the straight line AD. Draw the straight lines AG and DI perpendicular to AD. In AG take any point M, and draw ML, making the angle AML equal to the angle of the bevel of the bridge, meeting CH in the point L. Draw La perpendicular to AG', meeting AG in a. Prolong ha to meet DI in Q, and draw ON parallel to LM, so that the distance between LM and ON may comprise the breadth of the bridge. Let ON meet CH in O, and AG in N; then will LMNO be the plan of the bridge. Find the developement MPQSRN upon the straight line AG, the curve MPQ being the developement of the arc insisting on ML, and NRS the developement of the curve line upon NO. Draw MQ, and divide MQ into as many equal parts as there are intended to be arch-stones, which we shall here suppose to be fifteen; hence there will be a ring-stone in the middle, and the number of ringstones will be equal on each side of the middle one; let P be the middle point of the line MQ, and let a, b, c, &c. be the points of division on one side of P, and a',b',c, &c. the points of division on the other side. Through the middle point P draw the straight line WX. Throu...
