208 



Fissility and Interlockedness. 



Scklich (Fisher), v, 39, has a special section devoted to " Fissility," or 

 " Fissibility," as lie calls it. 



By the fissibility of wood is meant the property it possesses of being split by a wedge driven into 

 it in the direction of the fibres. Fissibility is clearly a form of hardness. . . . Branch and rootwood, 

 owing to twisted knotty structure, is harder to split than stem wood, and no part of a tree is harder to split 

 than the stump, where the tap and side-roots unite to form the bole. Trees with twisted fibre are specially 

 hard to split, and it is found that those twisting from left to right (against the sun's apparent course) are 

 harder to split than those twisting in the opposite direction. The structure of the medullary rays lias 

 very great influence on the fissibility of a wood, for they are in the plane in which the principal splitting 

 action lies, so that (trees) with large rays are easily split. 



In addition to this factor of structure, lie deals with Elasticity and Flexibility of 

 Fibre, Moisture, &c, Locality and Mode of Growth, all in relation to Fissibility. 



Those timbers which are converted by splitters into rails, shingles, and palings 

 may be fairly enumerated as fissile. As a rule, species producing such timbers grow 

 in sheltered valleys with good soil and drainage, and good cultural conditions generally, 

 so as to encourage straight, rapid growth. The timber-getter, as a rule, knows his 

 species by experience, and he selects individuals by reason of their absence of twist, 

 usually obvious in the bark to the trained eye. A simple guide will be the list of uses to 

 which timbers are put and which presuppose fissility, in my " Notes on the Commercial 

 Timbers of New South Wales " (Third Edition). 



Amongst Eucalypts, the Stringybarks have a fair degree of fissility, to which 

 may be added the Mountain Ashes (E. regnans and E. gigantea), which are more fissile 

 still. But very many species are worked up by splitters for one use and another, 

 Fissility enters somewhat into the classification submitted at p. 142, Part LIII. 



Notice the admirably depicted shearing tests in Plates 60-64 of Julius, 1906 (a). 

 The following also is a measure of fissility : — 



Tests to determine the holding power of dog spikes in sleepers were made with both old and new 

 sleepers, the old sleepers being drawn from the " road " by withdrawing two out of the four sjiikes, thus 

 allowing the sleeper to be removed without disturbing the remaining two spikes. 



These were then " pulled out " by means of the apparatus shown in Plate 26, the " pull " required 

 to " start " the spike being recorded, as also the size and type of spike. New holes were bored in the 

 "' old " sleepers and the spikes redriven, to be again pulled out in order to determine the holding power 

 of the " used " sleepers upon the freshly-driven spikes. Similar tests were also made upon new sleepers. 



All of the spikes were -§ inch square, and, with the exception of several of the oldest sleepers, were 

 of the standard pattern marked B. on Plate 26, and had been driven into holes bored with a jj-incli auger. 

 ("W.A. Timber Tests, 190.6," by G. A. Julius, p. 11.) 



Photographs illustrating fractures, which are a measure of fissility, can be seen, 

 not only in the works of Julius, but also in those of Professor Warren, A. 0. Green, 

 Nangle, and many others. 



