264 NATURAL SCIENCE. April. 



of force, and the vicissitudes of gravel making, thoroughly understood. 

 In this tool a half pebble is again employed, and from the flat side the 

 whole of the right edge is worked, being struck at a very low angle 

 and made to correspond with the opposite edge. And here again, as 

 in the preceding, the flakes from the point to the commencement of 

 the butt are in the same plane, or at the same angle ; and with the 

 change of grip to operate upon the butt, the angle becomes correspon- 

 dingly changed. A few flakes removed from the left edge, extending 

 about half of its entire length, complete the bilateral symmetry. In 

 Fig. 4 we have got a step further, or, judging by the specimens before 

 us, several steps. Nature, however, still claims the greater part of the 

 work. The large flake from the base is due to the action of frost, but 

 antedates the work on the edge, so that it is practically worked on one 

 side for seven-eighths of the edge, the blows being delivered in different 

 zones and at diff"erent angles. On the other side Nature claims a 

 greater share, about one-quarter of the surface being occupied 

 by the natural bark, and about another third by frost-bite ; but 

 in this we are introduced to workings on both sides of the edges, 

 which mark a decided advance upon the early workings from 

 one side only. Fig. 5 shows a still further advance ; a great 

 deal of the natural bark is still left, but there are decided attempts 

 towards a thickening of the butt, and a tapering from above 

 and below towards the point. Unfortunately, the ancient artisan 

 found he had got too much material to finish with ease and did 

 not quite understand the angle at which flint breaks; but he had 

 the right idea in his head, and probably was far more successful than 

 in this case before he gave up implement making. In Fig. 6 we have 

 a greater advance ; the bark is still retained for the base, but the 

 latter is well thickened. Most of the blows, however, were delivered 

 from one side, giving rise to a piano-convexity. This is about the 

 quality of skill achieved by the Hill-men. Fig. 7 marks a still further 

 advance, being chipped all over, and is only one of many specimens 

 which are found in the hill group and occasionally in the valleys. 



In selecting from Harrison's collection a half-dozen specimens to 

 illustrate the whole evolution of a type, we are aware of the great 

 gaps that exist between each specimen figured, and of this we are 

 more conscious from the large number of specimens presenting those 

 intermediate characteristics now before us. We cannot expect to 

 prove the evolution, but merely to show the relation of one form to the 

 other. Study of the specimens, however, shows clearly enough that 

 we have here an unbroken sequence of development. In some cases, 

 such as hollow scrapers and bone-splitters, quality of work and 

 condition of material alone separate the Plateau from the Neolithic 

 forms. There are numerous other extensive groups into which the 

 Plateau tools can be divided, in which the archaean character is only 

 surpassed by their constancy of form and recurring numbers. What 

 the uses of some of these tools could have been is as great a mystery 



