492 GEOLOGICAL REVOLUTIONS. 



but in the midst of or at the top of the gravel, which could not 

 be the case if water-streams had urged them, for then they would 

 have been on the bottom. 



Illustrations of both processes occur near Oxford. At Yarnton, 

 where below some 12 feet of ordinary local, mostly oolitic, gravel, 

 lay a separate bed, about 18 inches thick, of large rolled stones 

 of the ' northern drift ; J and on this bed were found most of the 

 numerous teeth and tusks of elephants which occurred there. 



On the other hand, at Long Wittenham, a block of * sarsen' 

 stone, 4 feet 6 inches long, was found in the upper part of the 

 ordinary flood gravel ; a good example of ice-transported stone. 



Thus we are conducted again to the contemplation of a time 

 when this region was subject to greater extremes of cold than now, 

 with more abundant rain and snow a pluvial period after the 

 last retreat of the great waters ; and it is permissible to believe 

 that the local climate has been gradually improving and acquiring 

 more of its insular mildness and comparative dryness from that 

 day to this, when fears, not founded on accurate registration, how- 

 ever, are occasionally expressed that the annual rainfall in our 

 country is sensibly and injuriously diminishing. 



