Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne (1867).djvu/20

 Southward of the Coquet they extend for some distance along Watling Street. They appear, too, in the bed of the Reed, near to Ramshope, and up the River beyond White Lee, and up the Carter Fell, by the road side, nearly as far as the toll bar. They are a prolongation into Northumberland of the same formation, which runs across Berwickshire, from Siccar Point in a west south-west direction, and which occupies about one-third of Roxburghshire, with rolling hills of moderate elevation. In Northumberland these rocks reach a height of 1700 feet above the sea level, and consist of distinctly stratified Greywacke and Greywacke Slate; but though much jointed, and divided sometimes into flat irregular prisms, they have no slaty cleavage. Crushed and squeezed, highly inclined, and folding over each other, their dip is irregular both as to direction and amount, yet the general strike of the beds is, on the Coquet, from north-west to south-east, and on the Reed from west to east. Composed of felspar and quartz, with a little mica and sometimes chlorite, their disintegration yields a soil retentive of moisture; but as drainage is effected through numerous joints and the highly inclined planes of stratification, the soil above them is comparatively dry. The protusion [sic] amongst them of mighty masses of igneous felspathic rocks, in the border counties, seems to me sufficient to account for their elevated and crushed condition.

Their position in the geologic series is thus far certain—they are much older than the Old Red Sandstone conglomerates, which cover them unconformably in Berwickshire and Roxburghshire; and on the Reed they are in like manner overlaid by Mountain Limestone beds. Fossils have not been detected in them in Northumberland, nor in Roxburghshire; but Mr. Stevenson, of Dunse, has found a Graptolite and tracks of an annelid in Greywacke, on the Dye Water, in the northern part of Berwickshire, in beds, however, which appear to be high in the system. The Northumberland strata may be of the same age as the Longmynd rocks, referred by Sedgwick to the Cambrian, and by Murchison to the Lower Silurian system; and hence, until more definite knowledge is obtained, they may conveniently be designated Cambro-Silurian.