ARTS IN THE STONE AGE. 



35i 



to the conditions under which the implement-hearing drifts are found; 

 for if the term petrological is to be understood as meaning rocks found 

 in situ in the river-basins, and thus native to the soil, then it is not 

 the fact that the constituents of the gravels in question belong to 

 those basins ; for we know that they are often largely made up in 

 one instance cited by Mr. Evans, to the extent of 50 per cent. of the 

 quartzose stones known as Lickey pebbles, and rounded fragments of 

 jasper, quartz, and other foreign rocks. Such rocks certainly do not 

 belong petrologically, in the proper sense of that term, to the river- 

 basins in which they occur, but to strata of a far earlier date. As Dr. 

 Buckland has shown, the quartzite pebbles are derived from the New 

 Red sandstone beds in Warwickshire and Leicestershire, and were at 

 some remote period forced over the escarpment of the Oolite into the 

 south and east of England. Whether they were brought in before or 

 after the present river-valleys were formed is not very clear, nor per- 

 haps very material. It is incontestable that they were transported 

 from a great distance, and possibly by the same forces that brought 

 the flint-gravels ; and it is equally certain, in several instances, that 

 their transport cannot be attributed to rivers now in action, because 

 those rivers flow, as at Brandon, toward the quarter from which the 

 stones were brought. 



Nor, if it were certain that the intrusion of these rocks dated back 

 to the Glacial epoch, as is usually supposed, or to some other very dis- 

 tant period, and had thus become denizens, if not natives of the soil, 

 could the inference which is drawn from the absence of extraneous 

 rocks be regarded as satisfactory. 



The occurrence of alternate elevations and depressions of the land 

 above or below the sea-level, during the post-glacial times, has been 

 suggested by several English writers ; and, if we suppose a dis- 

 trict comprising the south of England and the north of France, cor- 

 responding, or nearly so, with that in which no bowlder-clay is found, 

 to be sufficiently depressed, and then invaded by a deluge, the argu- 

 ment drawn from petrological conditions will cease to apply ; for, no 

 rocks are found in the drift-gravels, but such as belong to the supposed 

 deluge-basin. A delude of short duration would not necessarily in- 

 troduce any foreign rocks into the submerged area, but would sweep 

 into hollows and valleys those that came in its way ; and, even should 

 the submergence be of long continuance, as in some provinces of Hol- 

 land, it would leave no more traces than those exhibited in our drift- 

 gravels. That such a partial deluge was both possible and probable 

 is evident, when it is considered that a depression of 600 feet would 

 perfectly well effect it ; and, as we have evidence that the land has 

 risen in several places 30 feet and more within the historical period, it 

 is not difficult to believe that, in the infinitely longer time that proba- 

 bly intervened after the Glacial epoch, the same process of elevation 

 may have been going on for many ages. 



