The Valley of the Teign. 291 
watershed which separated them from the eastward course of the 
Upper Teign. It is supposed that the portion of the Teign valley, 
which lies between Dunsford and Clifford Bridge, was formed by 
one of these affluents, and that it was deepened till the separating 
ridge at its head was reduced to a col or pass leading from the one 
valley into the other. A flood or the damming-up of the river by 
a landslip might send down the waters of the Upper Teign, and once 
this was accomplished the capture and diversion of the Upper Teign 
would be permanent. 
The theory of the capture of one river by another has been 
accepted as an explanation of similar difficulties in the case of 
other rivers, and its application to the course of the Teign furnishes 
an intelligible explanation of the facts. The author thinks that 
some other river-courses and geographical features in Devon can be 
explained on the same theory of an easterly incline modified by 
a subsequent southerly tilt. 
March 23rd.—J. E. Marr, Sc.D., F.R.S., President, 
in the Chair. 
The following communication was read :— 
‘On the Moine Gneisses of the East-Central Highlands and their 
Position in the Highland Sequence.’ By George Barrow, Ksq., 
E.G 
The paper is divided into two parts. The first deals with the 
parallel-banded grey gneisses or gneissose flagstones of the Perth- 
shire and Aberdeenshire districts, which, in their field-characters as 
well as in their composition and structure, are identical with the 
Moine gneisses of the North-West Highlands. A description is 
given of these gneisses, as seen in and about the Garry in Perthshire, 
and this is followed by a brief account of the same rocks in the 
ground to the east and north-east, extending to the Forest of Inver- 
cauld, north of Braemar in Aberdeenshire. Special attention is 
drawn to the fact that towards the eastern end of the area large 
masses of highly-quartzose gneiss occur, which are really part of the 
Central-Highland quartzites in what the author conveniently de- 
scribes as a ‘ Moine-phase,’ and should not strictly be included in 
the typical banded grey gneisses at all. 
In the second part, dealing with the mode of ending-off of these 
gneisses to the south-east, it is shown that they cease to be recog- 
nizable as Moine gneisses, owing to the fact that they thin away and 
also become more finely banded, while at the same time they become 
less crystalline or cease to be gneisses. ‘'o prove this, an account 
is given of a series of sections lying along a belt 40 miles in length, 
extending nearly from Blair Atholl to the east of Balmoral, in 
Aberdeenshire. The first and most important of these occurs about 
