Correspondence — Mr. A. J. Juices Browne. 431 



(of which I certainly forwarded several specimens), my full account 

 of their discovery (Memoir, p. 145) and locality has not been given, 

 and my suggestion that they came from the horizon of this same 

 Obolus zone, rather than that of the Magnesian sandstone, has been 

 omitted. 



My statement as to the absence of unconformity in the Salt Eange 

 is indorsed at p. 2 (wherein he differs from the views presented in 

 the Manual), but he seeks to establish breaks in the perfectly con- 

 secutive and stratigraphically united series, both on palaeontological 

 and other grounds ; overlooking the point that the perfectly united 

 fossil-bearing groups distinguished as Carboniferous and Triassic, 

 Jurassic and Cretaceous, in my list (Memoir, pp. 66, 96, and 277) — 

 from one to another of which some genera at least pass upwards — 

 must be considered moi'e definitely related to one another than any 

 of them are to the equally physically united but unfossiliferous 

 groups beneath. 



One of these unfossiliferous groups at a higher stage in my list, 

 No. 8, the red Trias (?),is entirely omitted from Dr. Waagen's transcript 

 of my classification at p. 3 of his paper. Though dealing with other 

 Azoic groups, he seems to have been unable to find a place for this one, 

 leaving it suspended in the anomalous position of Mahomet's coffin. 



As a matter of fact, there is little choice as to which of the Salt 

 Eange groups are most closely associated or most distinctly divided 

 by stratigraphic features ; difference of colour and texture, more or 

 less sudden change, or apparent local transition, being characters 

 observable with varying intensity along most of the boundaries ; 

 still I had little difficulty, except in one or two cases, in identifying 

 each group of the series as on a distinct horizon. 



Should Dr. Waagen's palseontological labours improve the classifi- 

 cation I adopted after consultation with him (as above stated), it will 

 be a welcome result. I regret, however, that his indiscriminate im- 

 putations of error compel me to state the actual share taken by him 

 in what had been done previously. 



A. B. Wynne, 

 Geological Survey of India. 



JUKES' S THEORY OF EIVEE VALLEYS. 



Sir, — Mr. Kinahan's reply to my letter on this subject is so extra- 

 ordinary that I must crave space for a few further remarks. 



In his book on Valleys, Fissures, etc., he devotes several pages to 

 the discussion of Jukes's explanation of the river valleys in South 

 Ireland, and from one of these pages I quoted a statement referring 

 to the limestone of that district ; yet he now " explains " that the 

 extract " refers to the formation of valleys in any country and in 

 any kind of rocks." 



I maintain that the passage cited has no sense unless it refers to 

 the South of Ireland and to Jukes's theory. 



Admitting that Professor Jukes in 1862 did believe that the 

 Carboniferous Limestone was originally deposited over the whole 

 of S.W. Ireland, yet the theory then enunciated by him in no way 



