J 52 FRAGMENT OP SILICIFIED WOOD 



it "would almost infallibly be picked up as such if found lying in a 

 forest ; and it was at once recognised as such both by its original dis- 

 coverer and the various skilled backwoodsmen and lumberers to whom 

 we have shown it. 



In the third place, some of the appearances presented by the frag- 

 ment, which at -first sight appeared to us to militate against its being 

 an artificial chip, turn out, upon closer examination, to constitute 

 additional proofs that this is its real nature. Thus, the upper surface 

 of the fragment, though directed, as a whole, almost at right angles 

 to the fibres of the wood, is not plane, but is curved, with the con- 

 cavity of the curve directed upwards. This appearance would seem 

 difficult to reconcile with the hypothesis that the surface had been 

 produced by one or more blows with a sharp instrument. In point 

 of fact, however, this is an appearance which is quite commonly pro- 

 duced in chips, owing to the axe being blunt or not held with a very 

 firm grasp. When this is the case, the edge of the axe is exceedingly 

 apt to turn, and thus a curved instead of a plane surface is produced. 

 Again, the lower surface forms a plane directed obliquely to the fibres 

 of the wood, and interrupted by numerous ledges or steps correspond- 

 ing with and parallel to the successive concentric layers. These 

 layers we were at first disposed to consider as due to changes taking 

 place after the fragment had actually been produced ; for in the ordinary 

 way a freshly-cut chip does not exhibit similar ledges crossing the 

 cut surfaces. An examination of several hundred recent chips, in 

 all stages of desiccation, showed uk, however, that no inequalities of 

 surface at all comparable to this are produced by contraction or expan- 

 sion of the fibres of the wood on drying. The only similar appear- 

 ance produced by changes taking place after the chip has been cut is 

 what is sometimes seen in old pine-chips where minute parallel ridges ' 

 are sometimes formed by a kind of weathering, owing to the inside 

 of each annual layer of growth being slightly softer than the out- 

 side. We found, however, that a surface precisely similar to that 

 seen in the specimen, with precisely similar ledges and inequalities, is 

 produced when the chip is cut ivith a blunt axe — owing to the fact that 

 the successive concentric layers of the wood differ in hardness, and 

 the axe makes a succession of slips in cutting through them. Similar, 

 thoiigh not such pi'onounced, inequalities are occasionally produced 

 when the chip has been cut by a succession of blows. This action is 

 further assisted by the wedge-like form of the axe-head, which both 

 promotes the slipping of the edge of the axe, and necessarily exercises. 



