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Limestone toMUstoueGrit.Lias audOolite. Whilst theformer there- 

 fore must owe its formation to pre-existing beds of chalk, whence 

 the flints have been washed out, the latter is derived from the 

 rocks over which the ancient river Avon and its tributaries flowed. 

 What then is the inference to be derived from this fact ? Why, 

 that the same stream which cut its way through the old beds 

 bringing along .vith it specimens of the rocks over which it once 

 flowed to be found now not many feet above its present level, 

 did not deposit the gravels which in so many places rest at so 

 much higher a level on our downs. If, however, these gravels 

 were not deposited by the ancient Avon-which though much 

 increased in volume and flomng with far greater velocity m those 

 days yet maintained the same main line of drainage as now-how 

 were they deposited] We have a certain guide in fixmg the 

 date of the river bed gravels in the MammaHan remams 

 and shells of freshwater or terrestrial origin winch are 

 found in the intercalated beds of mari ; but I have been 

 entu-ely unsuccessful in finding a trace of an organism to fix the 

 date of these higher gravels. Neither are there .any foreign 

 pebbles in them which would enable one to correlate them ^ath 

 the Northern drift, which occurs further North and Eastwards 

 on the opposite side of Severn valley, so as to assign then- 

 deposition to the agency of the gi-eat ice age. Nothing of the 

 sort; neither are there any ice-scratched pebbles, the gravels 

 consist entirely of flint and small grams of quartz, which would 

 indicate that they came from the great Chalk range existmg to 

 the South. That they were transported by water in some form 

 is evident, for nothing but water would have moved them into 

 their present position, and distributed them between two hori- 

 zontal beds of OoUte in the way they are seen to be in this quarry. 

 I must confess at present I do not see my way to a clear solution 

 of the difficulty, but am inclined to attribute their presence to a 

 period when a portion of our table lands, after ha^nng been sub- 

 merged by the sea and denuded of the Chalk with flints and 



