1896.] the Plateau Gravel of Salisbury and elsewhere. 121 



work of a much earlier date than that of the river gravels in 

 which flint implements have long been recognized. It has been 

 proposed to group these " most ancient stone " implements under 

 a new name, palaeotatoliths, or for shortness, palseotoliths. 



The subject falls into two parts, (1) the age and origin of 

 the beds in which the flints in question are found, and (2) the 

 character of the flints themselves. 



The upper chalk is mostly covered with a thick layer of what 

 is known as " Clay- with- Flints." This consists of the insoluble 

 residue left when, by the action of the surface water charged 

 with carbonic and other acids, the carbonate of lime has been 

 removed. But it is generally the lowest part only of this deposit 

 which is obviously derived directly from the chalk. In it the 

 flints are not worn nor broken, or, if they have been broken, the 

 several parts have not been separated, but all the upper part 

 of the Clay -with -Flints consists of broken and apparently 

 weathered flints in a matrix of red clay. This can only be ex- 

 plained on the supposition that there has been a kind of soil- 

 creep going on for ages. Had it been due to the agency of floods 

 the stones and clay would have been sorted and the deposit 

 would have been more or less stratified. The subsidence neces- 

 sarily accompanying such enormous subterranean denudation 

 would initiate and keep up the movement of the superficial mass. 

 A rough measure of the amount of such subterranean denudation 

 may be obtained by an inspection of the nearest sections of upper 

 chalk where it will be seen at a glance what an immense thickness 

 of the chalk with flints would have to be removed to furnish, say, 

 10 feet of the insoluble residuum. Every here and there, 

 especially on its margin, the clay has been all washed out of 

 the " Clay-with-Flints " and carried away, and a universal covering 

 of white-weathered fragments of flint is distributed all over the 

 surface. These flints are also on the move. They creep down 

 the slopes and accumulate on every ledge and terrace. They 

 more obviously travel down the " dry chalk valleys," where also 

 the motion is largely due to subterranean denudation, the water 

 which runs through the porous gravel removing the soft and 

 soluble chalk below it and only appearing at the surface in very 

 wet seasons when there is more water than can pass even through 

 this very open gravel. If there happen to have been any remnants 

 of older superficial deposits left on the hill side, they too start as 

 the underlying chalk gets destroyed, and travel down by all the 

 processes of soil-creep, finally becoming worked into the general 

 superficial mass. 



When these various deposits come within the action of either 

 occasional or perennial streams they are handed on more rapidly 

 and are dropped as ordinary river gravels or silts. 



