Page:Timber and Timber Trees, Native and Foreign.djvu/255

XXVIII.], and also for various fitments in cabins and storerooms; and its special fitness for deck purposes has been already mentioned. Further, the cheap, common, middling quality is in request for props, or shores, required for supporting a vessel while in course of construction, or while in dock undergoing repairs, for which, and similar purposes, its coarse character is not an objection.

Having in former chapters, treating of the hard-wood trees, adopted the British Oak timber as the standard of quality and fitness for all the purposes of naval and civil architecture, so I propose to adopt the Dantzic Fir timber—the most important and generally useful of the Firs and Pines—as the standard of comparison for the soft or white wood class. I have, therefore,gone more fully into the experiments on this timber than it would have been possible for me to do with each of the other descriptions.

The transverse experiments recorded in Table CXXII. were made upon pieces of well-seasoned wood, of good average quality, and in every respect fit to be employed in the best architectural works, their specific gravity ranging from 478 to 673, and averaging 582. Of these specimens the elasticity of one piece was perfect immediately after the weight of 390 lbs. was removed, and in each of the others it was very nearly so, the average of the whole giving only .066 of deflection. All these would probably have recovered their straightness if time had permitted of their being left for only a short period prior to proceeding with the breaking strain.

The strains required to break these specimens varied very much, the minimum being 175 and the maximum 242.5 lbs., the average 219.16 lbs. on the square inch. The deflections at the crisis of breaking varied from 4. 5 to 6.15 inches, and averaged 5.142 inches.