. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 1 * The dotted line ii p should be produced to r. and V u produced fo (âthe dotted line/// should be a full line. Let L M (fig. 4) be the elevation of the face of an oblique arch, on a plane at right angles to the axis of the cylinder on which it is formed, n u being the radius. From the point K in the straight line K H, (fig. 5,) draw K F and K G, making the angle HK F equal the angle of obliquity of the arch, and the angle H K G the angle of extrado. Set off'K G =z n u the
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 1 * The dotted line ii p should be produced to r. and V u produced fo (âthe dotted line/// should be a full line. Let L M (fig. 4) be the elevation of the face of an oblique arch, on a plane at right angles to the axis of the cylinder on which it is formed, n u being the radius. From the point K in the straight line K H, (fig. 5,) draw K F and K G, making the angle HK F equal the angle of obliquity of the arch, and the angle H K G the angle of extrado. Set off'K G =z n u the radius, and through G draw G F at right angles to K H, intersecting K H and K F at H and F. Upon the vertica. line M u produced (fig. 4,) set off« r 1= F H, and from u with the distance H G describe the arc R W S. Then to find the angle formed out any ioint n. Join n u and through W where n u intersects the arc R W a, draw p t parallel to L II, and from ji draw ii r parallel to M u, intersecting p t in ;;. Join J) V and the angle p v t is the required angle. For let F H = r' and using the same letters for the angles as before. K H = r' cot 1 K G = r' cot. e, sec. 9. f- fig. 5. h %⢠4. / u := r' cot. e, tan. 9, cos. u V = r'. tv=:r'-\- ()â¢' cot. 9, tan. 9, cos. ) And p I â := !â u=z r', cot. 6, sec. 9, sin '.. j Hence the ratio o(p t to t v is the same as a sin. /C is to (b cos. I) -f- r, and therefore the angle p v I is the same as that obtained bv the formula. Fis. Tlie angles for the remaining joints being foimd in the same man- ner, and the mould of curvature of the spiral line of the intrado applied at V, the curved bevels or templates for all the voussoirs on both sides of the arch are at once obtained as shown in the figure. I am. Sir, vour obedient servant, \V. H. Barlow. £rereton, September 17, 1811. N. B. Will you be so good as to make the following corrections in my last communication. In Fig 1 the letter A is omitted at the intersection of the l
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