118 AXXITEESAEY ADDRESS 



idea as to the distribution of the drift or gravels of the neighbour- 

 hood ; for we have here two different kinds, if not more, of this 

 series of drifted rocks. "We have what is known as the Glacial 

 Drift, and we have along our valleys the Eiver Drift ; the Glacial 

 Drift being probably due to the last submergence of the countiy 

 below the sea, and the River Drift to the excavation of the valleys 

 by the rivers themselves or by rivers running in much the same 

 course. All those members of the Society who have paid any 

 attention to geology are perfectly aware that at the time the 

 glacial drift was deposited, there is every probability that the 

 climate was much colder than it is at present, and that those clays 

 in which we find small fragments of chalk, and foreign pebbles, 

 were either brought by icebergs or formed by the action of a large 

 coating of ice on the surface of the country. It is an open question, 

 whether to a certain extent the valleys in the Chalk have not been 

 excavated by large local glaciers ; whether we have had here at 

 some time or other a thick coating of ice, which, working towards 

 the sea, ploughed out a portion of our valleys ; but. whether this 

 is the case or not, we have evidence, in the gravels, of rocks having 

 been brought here from a very considerable distance. I think it 

 would be worth the attention of any of us to form a collection of 

 the different pebbles found in the Watford gravels, with the vie\\^ 

 of ascertaining the general proportion of each, and then of tracing 

 the countries fi-om which they came ; for many of the stones must 

 have been brought, probably by the action of floating icebergs, 

 fifty, a hundred, and in some eases some hundreds of miles. 



In the valley gravels you find some of the remains of the older 

 gravels mixed with the flints washed out of the chalk by the rivers. 

 It is therefore rather difficult to distinguish between those gravels 

 which are of marine origin and those of fresh- water origin. But 

 still, if you flnd in the gravels the remains of the animals which 

 must have lived on land, the probability is that those gravels were 

 deposited by the action of streams running through the land, and 

 not by the sea. In some cases the remains of the large mammotli — 

 the large hairy elephant — have been found in these valleys. On one 

 occasion the tooth of an elephant was found at Bricket Wood ; and 

 in the vaUcy of the Gude, at Two Waters, an elephant's tooth was 

 dug up in the gravel, in the excavation for the Canal. In the* 

 valley of the Gade I have myself found one or two instruments 

 of flint, which bear testimony to the fact of man living in this 

 country at tlie same time as the animals of what is known as the 

 Quatemaiy fauna. 



