294 Edward Merrick — The River Tyne Drainage Area. 



affords a rather more distinct indication of pressure, as does the well- 

 known Cipollino from Eubcea, which, of coui-se, contains more pale- 

 green mica, etc. It is also nearly identical with the white marbles 

 here and there intercalated in the above-named dark mica schists, the 

 isolated masses of marble on both sides of the Tosa about Ornavasso, 

 and those seemingly intercalated in gneiss on the Spliigen Pass, and 

 on the descent from the San Bernardino Pass to the baths of the same 

 name. 1 But all of these afford distinct indications of some amount of 

 crushing. They differ much from the dolomites of the South-Eastern 

 Tyrol and from some rather marble-like limestones in other parts of 

 the Alps, both of Mesozoic age ; even from the remarkable imitation, 

 but imitation only, of Cipollino marble worked near Saillon in the 

 Phone valley not far from Saxon. 



^f The absence of signs of crushing in the best Carrara marble, 

 while it is so marked in the schists, is certainly a difficulty, but we 

 must suppose, and I have little doubt that a fuller study of the 

 sections in the field would show it to be the case, that the statuary 

 marble is obtained from lenticular masses which have been saved from 

 being crushed by the yielding of adjacent bands. I have noticed 

 something of this kind in one or two of the Alpine marbles. 



Thus the evidence obtained in the field and from a study under the 

 microscope of the schists and marbles of Carrara is altogether adverse 

 to the hypothesis of a Mesozoic, or even later Palaeozoic, age. That, 

 as with similar rocks in the Alps, is most probably Archaean. The 

 region is one where the rocks have been much faulted, but in which 

 those indubitably Mesozoic retain their usual aspect and character ; 

 as is their habit, so far as I have seen, in districts such as the Alps, 

 where pressure-metamorphism has produced notable effects. 



II. — On the Formation" of the River Ttne Drainage Area. 

 By Edward Merrick, M.Sc. 



THHE object of this essay is to outline the connexion between earth- 

 ly movements and the formation of the River Tyne drainage area ; 

 the period of its formation is also alluded to, though it is less definable. 

 This object becomes more accessible on dividing the area into the 

 following parts and considering each separately : — 



A. The Main Valley of the Tyne. 



B. The Watersheds South of the Main Valley. 



C. The Watersheds North of the Main Valley. 



D. The Earth movements considered stratigraphically. 



E. The Belationship to other Drainage Areas. 



A. The Main Valley of the Ttne. 



The rocks forming the drainage area of the River Tyne are all 

 Palaeozoic, and except for a small inlier of Silurian deposits at the 



1 After careful examination I formed the opinion that the apparent inter- 

 bedding was illusory, and that they were nipped in by thrust faults. Where, 

 however, the marble was associated with the calc-mica schists it obviously 

 graduated into these. 



