THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. V. 



No. XIL— DECEMBER, 1908. 



01ElXCrXl<TJ^X^ -A-I^TIOLES. 



I. — The Eole of Solution" in Valley-making. 



By A. J. Jukes -Bkowne, B.A., F.G.S. 



(WITH A PAGE MAP.) 



IT has recently been suggested that many of the dry valleys which 

 are found in limestone districts owe their formation to subterranean 

 solution, and not to surface-erosion ; in other words, that they are the 

 work of subterranean watercourses which, by dissolving the rock 

 substance, have caused subsidence of the surfaces overlying the lines 

 of such watercourses. 



This theory has been put forward as a complete explanation of 

 a whole system of valleys to the entire exclusion of the current view 

 that the chief agent in the excavation of all valleys is the mechanical 

 action of surface water-flow. The new theory assumes that in certain 

 districts there were no surface streams, that their drainage was entirely 

 subterranean, and that the existing valleys have been formed by the 

 gradual subsidence of the surface above the courses of the underground 

 streams. 



It has always been acknowledged that solution plays an important 

 part in the enlargement and deepening of the valleys in limestone 

 districts, but the idea of such solution has been chiefly connected 

 with the chemical action of the surface stream-water, and not with 

 the action of such water as sinks beneath the river bottom. It may 

 perhaps be admitted that we needed a reminder that a dry valley 

 may also be deepened by solution, but I very much doubt if the 

 solution is carried on in the manner imagined by the Rev. E. C. Spicer.^ 

 I think he pushes his theory much too far, and that he credits under- 

 ground waters with much more concentrated power in the way of 

 solution and valley-making than can possibly be attributed to them. 



"We are asked to believe that a definite system of underground 

 streams can be formed, without any surface-system, in such districts 

 as the Great Oolite plateau of Oxfordshire and the Chalk area of the 

 Chiltern Hills. We are told that the valley- system of the Glyme and 



^ See '• Solution Valleys in the GIjTne Area (Oxfordshire)," by the Eev. E. C. 

 Spicer, M.A., F.G.S. : Quart. Journ. Geol. Soc, 1908, vol. Mv, pt. 3, pp. 335-44, 

 pis. xxxviii, sxxix, 



DECADE v. VOL. V. — NO. XII. 34 



