120 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 21, 



base of the Gorton range, at Upway, and, while the rise is indeed 

 from several spots, a careful observer may remark that many of these 

 spots lie in straight lines, following, as I conceive, the lines of strati- 

 fication. This range too, although inland and apparently connected 

 with contiguous hills and valleys, is nevertheless geologically as iso- 

 lated as the Isle of Portland ; and as we know its longitudinal termi- 

 nations, its inclination of strata dipping towards the Upway Valley 

 in which the river rises, and its high and abrupt escarpment towards 

 the channel, we can have no hesitation in considering (after what has 

 been observed in Portland) that the source of the River Wey is con- 

 nected with the Gorton range exclusively. 



Lastly, as the Gorton range did not receive its present physical 

 features until the Tertiary age, it is evident that the present River 

 Wey has been only called into existence during that comparatively 

 recent ge,ological period. 



2. On the " Quartz Rock " of MacGulloch's Map of Scot- 

 land. By Daniel Sharpe, Esq., F.R.S., V.P.G.S. 



Among the many Formations of Scotland which are still involved 

 in obscurity. Quartz Rock causes the greatest trouble to geologists 

 exploring that country ; and yet the obscurity does not arise from 

 neglect. Dr. MacGuUoch published a paper on the subject in the 

 second volume of our Transactions, devoted a chapter to it in his 

 masterly work on the Western Isles*, described and arranged all its 

 varieties in his ^' Glassification of Rocks," and laid it down as a sepa- 

 rate formation on the geological map of Scotland ; but he left the 

 subject in a state of confusion which it will require much labour to 

 clear up. The difficulty has arisen from relying exclusively on mine- 

 ralogical definitions, and classing all rocks composed of certain mineral 

 constituents as members of one formation, without regard to their 

 origin or geological age. Thus a rock resulting from plutonic action 

 upon stratified sandstone has been confounded with another which is 

 geologically undistinguishable from gneiss, because they both consist 

 of quartz and mica, quartz and felspar, or some other arbitrarily de- 

 fined compound. 



Although by no means in a position to class under their proper 

 heads all the quartz-rocks of the Highlands, I trust that I shall be 

 doing good service if I can determine correctly the geological position 

 of part of them, and, by calling attention to the others, induce ob- 

 servers to examine those districts which I have not been able to visit, 

 with the view to settling the age and origin of the various deposits of 

 this rock. 



Mr. Gunningham is the only author I have met with who has done 

 anything to clear up the confusion in which MacGulloch left this 

 subject. In his excellent " Geognostical Account of Sutherlandf " he 

 describes the quartz-rock of that county as so connected and alter- 



* Vol. ii. p. 215. 



t Journal of the Highland Society, No. 46, Sept. 1839. 



