Correspondence. 4S 



3. Purple grey grits and slates — Morte Bay, etc. (Upper Devonian 

 ? no fossils). 



4. Marwood sandstones and Filton and Barnstaple group (Upper- 

 most Devonian). 



5. Dark soft Carboniferous shales — Barnstaple and Fremington 

 (Carboniferous slate). 



6. Limestones and Culm Measures (Mountain Limestone, Mill- 

 stone-grit (and Lower Coal?). 



Now tbis succession has been made out by De la Becbe, Sedgwick, 

 Mm-cbison, Pbillips, and otbers ; and I have verified a good deal of 

 it myself. Let us understand eacb other. I am glad to see tbat Pro- 

 fessor Jukes bas lately covered more of the ground ; and I am sure, if 

 be spends more time in botb Nortb and Soutb Devon, be will end 

 by agreeing witb bis geological brethren. Already be perceives the 

 resemblance in what we call the Lower beds (No. 1), and in No. 3, 

 to the Old Eed, as he knows it so well in the South of Ireland. 

 And if he will remember that, in S.W. Ireland, the Upper beds of 

 the Old Eed Sandstone lie unconformably on its mass, just as they 

 do in Scotland (Geikie), and through Wales, right away into Pem- 

 brokeshire, he will see the importance and extent of the duplex 

 formation which he is endeavouring to supplant. If, indeed, he can 

 find us true Carboniferous fossils in the three lower divisions, we may 

 yield the point to him. Hitherto they have only yielded Lower and 

 Middle Devonian species. No. 4, as be well knows, is the repre- 

 sentative of his own " Coomhola grits," which in Ireland lie, at all 

 events, at the base of the Carboniferous slate, and which I have 

 proved to be of the same age as the conglomerate beds (or part of 

 them) of the Upper Old Eed in Pembrokeshire. And I have also 

 shown that No. 5 contains Carboniferous fossils only. If, therefore, 

 the uppermost members of the Old Eed are equal to the uppermost 

 member of the Devonian, why not make room for the lower, which 

 cover the Silurians ? — I am, yours truly, J. W. Salter. 



FLINT COEES FEOM THE INDUS. 

 To the Editor of the Geological Magazine. 



Sir, — Witb reference to my letter in the October number of the 

 Geological Magazine (Vol. III. p. 433), on some Flint Cores 

 found by my Son, Lieut. Edward D'Oyly Twemlow, of the Eoyal 

 Bombay Engineers. Wlien he wrote last, about 20 feet of Water 

 covered the place, but be bas from memory defined the exact spot 

 and depth ia the accompanying sketch. 



d 



t-- ---' 



c c e 



Section on the River Indus, near Sukkur Pass, Upper Scinde. 



The lower limestone rock is not seen in the above section, but crops 

 up about 400 yards away from the river, with an upward inclination. 

 The upper 30 feet (c) is foimd in layers of one and a-balf to two 



