| Hemlock | 2,110 | 2,750 | 1,054,000 | | Pine, lodgepole | 2,290 | 2,530 | 1,219,000 | | longleaf | 3,420 | 4,280 | 1,890,000 | | red | 2,470 | 3,080 | 1,646,000 | | sugar | 2,340 | 2,600 | 1,029,000 | | western yellow | 2,100 | 2,420 | 1,271,000 | | white | 2,370 | 2,720 | 1,318,000 | | Redwood | 3,420 | 3,820 | 1,175,000 | | Spruce, Engelmann | 1,880 | 2,170 | 1,021,000 | | Tamarack | 3,010 | 3,480 | 1,596,000 | |-------------------------------------------------------| The second case, where the fibres bend with more or less regular curves instead of buckling, is characteristic of any green or wet wood, and in dry woods where the fibres are thick-walled. In woods in which the fibre walls show all gradations of thickness--in other words, where the transition from the thin-walled cells of the early wood to the thick-walled cells of the late wood is gradual--the two kinds of failure, namely, buckling and bending, grade into each other. In woods with very decided contrast between early and late wood the two forms are usually distinct. Except in the case of complete failure the cavity of the deformed cells remains open, and in hardwoods this is true not only of the wood fibres but also of the tube-like vessels. In many cases longitudinal splits occur which isolate bundles of elements by greater or less intervals. The splitting occurs by a tearing of the fibres or rays and not by the separation of the rays from the adjacent elements. [Illustration: FIG. 8.--Failures of short columns of green spruce.] [Illustration: FIG. 9.--Failures of short columns of dry chestnut.] Moisture in wood decreases the stiffness of the fibre walls and enlarges the region of failure. The curve which the fibre walls make in the region of failure is more gradual and also more irregular than in dry wood, and the fibres are more likely to be separated. In examining the lines of rupture in compression parallel to the grain it appears that there does not exist any specific type, that is, one that is characteristic of all woods. Test blocks taken from different parts of the same log may show very decided differences in the manner of failure, while blocks that are much alike in the size, number, and distribution of the elements of unequal resistance may behave very similarly. The direction of rupture is, according to Jaccard, not influenced by the distribution of the medullary rays.[7] These are curved with the bundles of fibres to which they are attached. In any case the failure starts at the weakest points and follows the lines of least resistance. The plane of failure, as visible on radial surfaces, is horizontal, and on the tangential surface it is diagonal.