334 Correspondence — P. Lake — H. C. 0. White. 



formed by earth-movements, and had produced a great effect upon 

 the river-system. In the discussion which followed this view was 

 severely criticized by Mr. Strahan, and was characterized by him as 

 highly speculative. 



A few months ago Mr. Strahan read at the Geological Society 

 a paper on the rivers of South Wales ; and in this he makes the 

 suggestion, quite as if it were new, that the north-east to south- 

 west valleys are due to earth-movements, and that the complications 

 of the drainage system have been produced by these movements. 



My paper was rejected by the Council ^ as too speculative : 

 Mr. Strahan's has just been published in the Quarterly Journal. 



To those Fellows who are not familiar with Burlington House, 

 I commend a comparison of these two papers. 



Philip Lake. 



MR. STRAHAN AND SOME ENGLISH RIVERS. 



SiK, — In his suggestive paper " On the Origin of the River System 

 of South Wales, etc.," in the recently published May number of the 

 Quart. Journ. Geol. Soc, Mr. Strahan states (pp. 219-220) that 

 " The [Chalk-] escarpment, in that part of it which extends from 

 Dorset to the borders of Hertfordshire, diverges from the water- 

 parting three times, namely, in the Vales of Wardour and Pewsey 

 and in the valley of the Upper Thames. In all these cases, rivers 

 rising in the low-lying Oolitic region flow eastward against the 

 general run of the country, and make their way through the 

 Chalk-escarpment to the Thames or Frome. The explanation did 

 not escape Ramsay. Their courses were initiated upon an eastward 

 slope of ChaJh, and the distance from their sources to the existing 

 escarpment is a measure of the recession of the escarpment since 

 the initiation." 



With respect to this passage (in which the italics are mine) 

 I should like to point out (1) that the river running eastward 

 through the Vale of Pewsey does not rise " in the low-lying Oolitic 

 region," but in a tract of Chalk and Upper Greensand to the east 

 of and some 200 feet above it. (2) That inasmuch as the rivers 

 traversing the Vales of Wardour and Pewsey follow the axes of 

 minor east-west anticlinal folds, they are to be regarded rather as 

 longitudinal, autogenetic branches of the north-south Salisbury 

 Avon, than as primary, or consequent, eastward streams of the 

 Upper Thames class. Unlike the Upper Thames, the Kennet- 

 Thames, or the Frome, which follow the slopes of constructional 

 troughs, these streams (i.e. the Nadder and Upper Avon) can only 

 have come into existence after prolonged denudation of the folds 

 on which they are situated. It is, therefore, scarcely probable that 

 their present sources were determined by, or, indeed, are in any 



* I owe it to the Geological Magazine that the article subsequently saw the 

 light (May and June, 1900). 



