26 A NJ'.W FLOIU OF 



Cornus Suecica, and Epilohium alpinum. The basaltic rocks 

 yield a more peculiar and varied Flora. 



The Cheviot porphyry is undoubtedly the oldest igneous rock 

 in our district. It was protruded subsequently to the Cambro- 

 Siluria era, for the Greywacke beds are highly inclined against 

 it ; but prior to the deposition of the Upper Old Red Sandstones, 

 as the conglomerates are partly composed of rolled Cheviot por- 

 phyries. The Cheviots, however, had been further elevated sub- 

 sequently to the Tuedian period, for beds of that age are highly 

 inclined against the porphyry on the Coquet and in Akeld Burn. 



2. On the boundary of Northumberland, near to Carhani, 

 there is another outbreak of igneous rock unconnected with the 

 Cheviots, and of a later age, but of a porphyritic character, having 

 a greenish claystone base resembling wacke, with crystals of red 

 felspar. It crosses the Tweed at Carham, and the railway near 

 to Reddon Burn, and then runs along Heddon ridge a distance of 

 about 3 miles. It protrudes through beds of the Tuedian group ; 

 and near to it is the peculiar Magnesian Limestone with chert 

 nodules. 



AUGITIC EOCKS. 



The Basaltic Whin Sill is the most remarkable rock in the 

 North of England on account of its long and tortuous range, and 

 of its relation to, and effect upon, the strata it traverses, and 

 among which it has been intruded. A sill it has been called, 

 because sometimes seen, like a stratum, intercalated among stra- 

 tified rocks. It is not, however, a true stratum, for its thickness 

 varies very much, from 2 or 3 feet to more than 200 feet, and 

 the parallelism of its upper and under surface is preserved only 

 for a short distance ; so that, though its extension in the line of 

 direction is great, yet its extension in the line of dip is inconsi- 

 derable. 



It is traceable through Northumberland, with breaks here and 

 there, from Kyloe to Glenwhelt ; and the same kind of rock 

 extends southward into Durham, Cumberland, and Yorkshire. 



Let us trace its range, and, as we go along, note any peculia- 

 rities. It first appears in the North at Kyloe Crags, in a fine 



