KOETHUMBERLAND AND DUEHAM. 7 



entirely absent; I have seen only a few crushed specimens of a 

 Ehynchonella in a shale bed at Garraitage Bank, This forma- 

 tion occupies a considerable area in the Merse of Berwickshire ; 

 and it is well developed in the Valley of the Tweed from near 

 the mouth of the Whitadder to Makerston, and hence the name 

 Tuedian has been given. It appears in the Vale of Till, and on 

 the flanks of the Cheviots. In Akeld Burn, about 100 feet of 

 characteristic beds are tilted up against the porphyry at an angle 

 of 85°. It is seen also in Biddlestone Burn, in the Coquet below 

 Linn Brig, and on the Eidlees Burn. At Linn Brig, where these 

 beds are in direct junction with the porphyry, they are highly 

 elevated, disturbed, and shattered. A section of them is in 

 Crawley Dene, near to Glanton ; and by a great fault they have 

 been thrown up on Garmitage Bank, 5 miles westward of Aln- 

 wick. Their relation to other formations is best seen on the 

 Berwickshire coast, where they are intercalated conformably be- 

 tween the Upper Old Sandstone and the Mountain Limestone. 



2. The Mountain Limestone occupies above two-fifths of the 

 district ; but it is principally spread over Northumberland north- 

 ward of the Tyne. It comes out beneath the Millstone Grit in 

 the valleys and hill sides of the South Tyne, of the East and 

 West Allen, of the Derwent, of the "Wear, and of the Tees j but, 

 as these portions are cut off by the Stublick Dike from the north- 

 ern beds, and are moreover of a somewhat different type f'^om 

 them, it is necessary to notice each series separately. 



Northward of the Tyne the Mountain Limestone consists prin- 

 cipally of sandstones and shales, with beds of limestone and coal 

 interstratified, and of ironstone nodules and layers among the 

 shales. The general direction of the strata is south-westward, 

 with a rise towards the north-west ; but in their range they are 

 interrupted by many faults, which however have the effect of 

 extending the same beds from the Tweed to the Tyne. They 

 are prolonged in a narrow band along the Berwickshire coast as 

 far as Lammerton Sheal. A line from the mouth of the Aln to 

 the Tyne, a little east of Corbridge, nearly marks their eastern 

 boundary. The area occiipied by them in the North is narrowed 



