73 



Ancient Rivers of Bournemouth. 



By Clement Reid, f.r.s. 

 (Read before the Geological Section, February 23rd, 1915.) 



rpHE history of any place is so intimately connected with 'ts 

 physical geography that the physical geography cannot be 

 ignored. In the case of a town like Bournemouth this is markedly 

 so. Bournemouth owes its importance entirely to its position and 

 scenery. It has no harbour, no manufactures, no mines. We will 

 try, therefore, to show what geological changes led up to the 

 selection of this site, and what strange vicissitudes the site went 

 through before it became the) pleasant place to live in that we now 

 see. 



I do not intend to deal fully with the ancient geological 

 history of Bournemouth, as illustrated in our cliffs; it will suffice to 

 begin with modern geological times. These times, however, 

 counted in thousands of years, are long. As a beginning, we need 

 go no further back than the Miocene, or Middle Tertiary, period, 

 when movements of the earth's crust caused the strata to be 

 thrown into folds, of which the Hampshire Basin is one of the 

 most conspicuous. 



The first result of this folding was the formation of a wide 

 trough, with an uptilt at its western end. The rain-water and 

 rivers were compelled to flow down the slopes thus formed, and 

 so the old valley of the Solent originated. 



The vital importance of the ancient Valley of the Solent in 

 the history of Bournemouth must be realized. Later changes have 

 greatly altered the topographical features, but the sunny south- 

 ward slope of gravel on which Bournemouth is now built owes 

 its origin to the former existence of a big river. We will, there- 

 fore, attempt to trace step by step the history of the Solent River, 

 from the earliest stages to the present time. Nowadays the valley 

 is so altered and cut into that only the geologist sees what an 

 important feature in the landscape it must once have been ; he 

 alone sees how many traces of it still remain. 



The Solent at one time was one of the largest rivers in 

 England. It rose far away in the west, flowed a mile or two 

 south of Bournemouth, and passed through the present Solent to 

 Spithead — where we can see how wide is the valley from hill to hill. 

 Eastward it was prolonged many miles, probably in early times as 

 far as the end of the South Downs at Eastbourne. It had then 

 many tributaries on the south, as well as those still existing on the 

 north. 



Gradually the encroachments of the sea cut off the heads of 

 many of the southern tributaries, opened up the estuary on its 

 south side, and shortened the river, till it was something like what 

 is shown on the map facing this page. 



As far as I can at present make out, the Solent Valley was 

 much in the state depicted towards the close of the Pliocene Period ; 



