28 The Rev. D. Williams on the Cornish Killas. 



■South Petherwin. 



. Killas. 



Brook. 



Clymcnicn Limestones. 



Does House*. 



The ascent is gradual and easy, without the least break or in- 

 terval, and from the circumstance of the culm slate and killas 

 cuttings being old, wayworn and dusty, and so symmetrically 

 packed and disposed, I had pre- 

 viously concluded that the for- 

 mer were continued down to the 

 brook, as they are a little north 

 of Landlake by Bad Ash, about 

 half a mile to the eastward ;. on 

 accosting them however with the 

 hammer foot by foot, their fresh- 

 ly fractured faces quickly un- 

 deceived me, and left me in no 

 doubt that the order of superpo- 

 sition was evidenced here with 

 as much simplicity, truth and 

 precision, as it was at Boscastle, 

 while it explained in the most 

 satisfactory manner the imper- 

 fect and doubtful section at 

 Landlake near at hand, which 

 had been noticed by Mr. Phil- 

 lips in his Palaaozoic Fossils, pp. 

 195 and 196, and by myself in 

 your Journal, No. 129, page 128. 

 Immediately adjoining " Does 

 House" on the west, is a place 

 marked " Tregaller" on the 

 Ordnance Map ; in a bye lane 

 near this, and immediately un- 

 der the letter g, I fell in with a 

 quarry of the Coddon Hill grit 

 which had been excavated for 

 the roads: its beds or layers in 

 the centre of the quarry have 

 been compressed into the form 

 of two pointed Gothic arches ad- 

 justed side by side, from which 

 they depart by an easy inclina- 

 tion to the south on the south 

 side, and by a low dip to the 

 nort{i on the north side. The 

 quarry is on the summit of the 

 ridge and apparently in its axis. 



,..-_ Killas. 



— Black Culm Slates. 



. . Tregaller. 



Coddon Hill Grit. 



Does House is about a furlong east of the line of section. 



