1 86 PREHISTORIC EUROPE. 



The " carry " of the stones in till is another indication of the 

 direction of ice-flow ; and the evidence thus supplied confirms 

 that afforded by all the phenomena of glaciation touched upon 

 in the preceding paragraphs. The stones are scattered about 

 promiscuously in the clay, but they nevertheless show a method 

 in the mode of their occurrence, the meaning of which is ob- 

 vious. We do not in the till of one place meet with an assem- 

 blage of blocks and boulders which may have come from any 

 and every part of the country. On the contrary, the contents 

 of the accumulation bear a strict relation to the geology of the 

 neighbourhood in which that deposit occurs. Thus, in a district 

 composed of Carboniferous strata, most of the stones in the 

 boulder-clay consist of fragments of sandstone, limestone, black 

 shale, coal, and other rocks pertaining to the surrounding neigh- 

 bourhood. And not only so, but the clay itself acquires a dark 

 dingy gray or blue colour, just such a hue as those various 

 members of the Carboniferous formation would assume were 

 they all pounded up and mixed in a mortar. Hence, as we 

 traverse the country we become aware that the colour, the tex- 

 ture, and the stony contents of the till vary as we pass over 

 different geological formations. If, for example, we set our- 

 selves down, say at the head of the Tweed, in the heart of the 

 Silurian Uplands, we find the till of that district crammed with 

 fragments of Silurian rocks alone, and we note that the colour 

 is generally a pale brown. Till of this character continues far 

 down the valley, until, by and by, after we have passed certain 

 of the lateral streams that enter the Tweed from the north, 

 we encounter occasional boulders of sandstone and porphyrite 

 which have come down the valleys of the Lyne and the Eddie- 

 stone waters. But Silurian fragments continue to form the 

 great bulk of the stones all the way down to where, a little 

 beyond Galashiels, we enter upon the Old Eed Sandstone area. 

 Very soon after passing the boundary-line between the two 

 formations, we notice that boulders of red sandstone make their 

 appearance, at first sparingly, and then in rapidly increasing 

 numbers. The clay at the same time gradually loses its grayish 



