Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/398

 point out as in itself constituting a sufficient distinction between the transported and untransported alluvia; the last of which, independently of its rounded and heterogeneous fragments, alternates with deposits of sand and gravel, and even of clay, but seldom or never exhibits the same irregular admixture of fine clay which is found in the former. The lines at the lower part of the glen are formed in the transported alluvium.

If we consider the first case alone, that of the untransported alluvium, we are led to enquire into the length of time required for its accumulation before the lines were formed in it. We see from the small changes these have undergone, that scarcely any wearing of the hills, and consequently no material deposition of rubbish has taken place since their formation, wide as that interval is. Yet the depth of this deposit being so great, while its accumulation is thus tedious, we are unavoidably carried back to an incalculable period of time previous to the existence of the lines, during which it must have been accumulating.

Let us now remark, that as no disturbances of the sharp alluvium, at least to a degree capable of producing the rounding of these fragments has taken place, it is plain that the waters which acted on this alluvium so as to produce the lines, had not been subject to violent motion. If there was no violent motion in the upper part of the glen, there could be none in the lower, since there is a continuity between these two parts. Yet these portions of the lines which are found in the lower part of the glen are formed in a rounded and transported alluvium of pebbles, sand, and gravel. This alluvium therefore was not thus rounded by the action of the water which produced the lines, since if it acted at all, it must have acted in a similar manner throughout the whole valley. We must consequently suppose that a rounded alluvium had been by previous