266 COMIPAjRJPSiON of the TAjSIMAjNIIAjNI tronatta. 



The Aborigines had already made at least one im- 

 portant invention, based on a certain amount of logical 

 reasoning. Instead of using any pebble or rock in its 

 natural state, they had learned that certain siliceous rocks 

 could be split, and that the flakes, by means of their 

 sharp edges, were more suitable implements than those 

 provided by nature — for instance, sharp-edged pieces 

 of columnar diabas. The latter were, of course, still 

 resorted to, but the bulk of the implements were artifi- 

 cially manufactured by the breakage of suitable siliceous 

 rocks. It is one of the peculiarities of these siliceous 

 rocks that they have a conchoidal fracture, which renders 

 the production of sharp-edged flakes comparatively easy. 

 And it is another peculiarity than when a flake is de- 

 tached from a parent block, that face by which it is de- 

 tached is generally very smooth and level. The flake 

 breaks off in a plane, which may be more or less convex, 

 but it always forms one plane. The shape of the face 

 opposite the flat one is determined either by the original 

 surface of the parent block or by the size and number of 

 flakes previously struck off. 



This peculiarity of fracture is probably the cause of 

 the particular way these flakes were grasped. The thumb 

 invariably rested on the flat side, not in the reverse way, 

 be it well understood. This practice being in use for 

 generations, eventually became an inborn habit. The fore- 

 most thought of the Aborigines when manufacturing an 

 implement was the production of a plane face as rest for 

 the thumb; the shape of the other face was inmiaterial. 

 It may have been made more convenient to fit the hand 

 by striking off smaller flakes, or it may have been left as 

 it originally was, but its shape was of no importance. 



The chief feature of the Tasmanian stone implement 

 is its unsymmetrical shape. Even if — as it has been 

 noticed in some specimens — there is an attempt of a 

 symmetrical outline, the symmetry of the two faces is 

 still existent. It is therefore obvious that the Tasmanian 

 tronatta could not be altered without destroying its essen- 

 tial features. The indical face could be treated by the most 

 delicate or regular chipping; the outline of the tronatta 

 may have been so carefully shaped that it was perfectly 

 symmetrical in two directions; all this did not alter the 

 character of the tronatta, which still retained its essential 



