Edinburgh Encyclopaedia Volume 12 PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1832 edition. Excerpt: ...which hang near the haunch, will bring it down, the crown C will thereby be raised into its proper position. All will now do, provided that the sum of the small pieces of chain has to the large one, AC'B, the same ratio which the stuff to be filled into the haunches has to the whole weight of the archstones; the depth of which must of course be previously determined. But, ifithis is not the case, it will be easy to calculate how much must be added to, or subtracted from, the small chains, in order to obtain this proportion. This being equally divided among the small chains, will give a roadway very nearly parallel to the former. The curve will eviqzlently be a perfect curve of equilibration, and extreme y near the one wanted. And this whole process is so easy, that it may be gone through in a short time by any intelligent mason. But although this mechanical way of forming an equilibrated arch be founded upon principles sufliciently just, and be perhaps the simplest and best way in which the practical builder could form the original design of such an arch, yet as it affords no general rules that may be applied to the construction of arches, we proceed to consider the same subject in a mathematical point of view. And first, then, in the semicircular polygon, as it is called: F19 4 Wh@1'e Weights are hung on the thread.AC'CC"B, which bring it into the position ACB, we have at each angle three forces in equilibrio. VVherefore, by the principles of statics, they are to one another VOL. IV. PART II. as the sines of the opposite angles; that is, the tension rC is to the tension IC, as sine lCV is to sine 1C/V, but the tension from C to Z is the same as from C' to r Also sine ZC/V is the same as sine 1'C'...