原创 Abercrombie Outlet403

Abercrombie Outlet403

It may appear presuming in us to question the pro* priety of this practice. There are situations in which H is unavoidable, as in the roofs of churches, which can be allowed to rest on some pillars. In other situations* where partition walls intervene at a distance not too great for a stout purlin, no principal rafters are neoes* sary, pnd the whole may be roofed with short rafters of Very slender scantling. But in a great uniform roof} which has no intermediate supports* it requires at least tome reasons for preferring this method of carcase roofing to the simpler method of making all the rafters alike* The method of carcase-roofing requites the selection of the greatest logs of timber, which are seldom of equal strength and soundness with thinner rafters. In these the outside planks can be Abercrombie and Fitch Outlet taken off, and the best part alone worked up. It also exposes to all the defects of workmanship in* the mortising of purlins, and the weak?ening of the rafters by this very mortising; and it brings an additional load of purlins and short rafters. A roof thus constructed may surely be compared with a floor of similar construction. Here there is not a shadow of do^bt, that if the girders were sawed into planks, and these planks laid as joists sufficiently near for carrying the flooring boards, they will have the same strength as before, except so much as is taken out of the timber by the saw. This will not amount to one-tenth part of the timber in the binding, bridging* and ceiling joists, which are an additional load; and all the mortises and other joinings are so. many diminutions Abercrombie and Fitch of the strength of the girders; and as no part of a carpenter's work requires more skill.and accuracy of execution, we are exposed to many chances of imperfection* But, not Abercrombie to rest on these considerations, however reasonable they may appear, we shall relate an experiment made by one on whose judg?ment and exactness we can depend*Two models of floors were made 18 inches square of the finest uniform deal, which had been long seasoned. The one consisted of simple joists, and the other was framed with girders, binding, bridging, and ceiling joists. The plain joists of the one contained the same quantity of timber with the girders alone of the Abercrombie Outlet other, and both were made by a most accurate workman. They were placed in wooden trunks 18 inches square within, and rested on a strong projection on the inside. Small shot was gradually poured in upon the floors, so as to spread uniformly over them. The plain joisted floor broke down with 487 pounds, and the carcase floor with 327. Tbe VOL. I. 2 O