System cannot be of the age of the Old Red Sandstone. 127 



Advancing further to the eastward, the road is on the culm 

 rocks to a Httle beyond some houses marked " Treworrel " 

 on the Ordnance sheet ; here we observe a thick narrow spur 

 of killas descending from the main body to near St. Juliott, 

 on the north. Here also we see the culm slates dipping be- 

 low it, and the overlying killas to dip in the same angle and 

 direction, north five points east; but we do not here trace 

 them foot by foot, nor is the passage of the one into the other, 

 in consequence, so clearly exposed as in the former instances. 



There are some good sections to the same effect about Al- 

 ternoA and Five Lanes, but the floriferous rocks there belong 

 to another parallel range of hills, and it would involve me in 

 too long details to particularize them at present. I therefore 

 request your readers will accompany me to South Petherwin and 

 Landlake on the south-west and south of Launceston. It is 

 prudent here that 1 fortify myself by observations recorded 

 by two distinguished geologists, in every word of which (ex- 

 cept " overlying") I perfectly concur, "in your Journal for 

 April 1839, page 246, Professor Sedgwick and Mr. Murchison 

 write, " last summer one of us found near South Petherwin, 

 what appeared an unequivocal passage between the fossiliierous 

 slates and the overlying {uiiderlymg) culm series." The 

 " unequivocal passage " is what 1 am most concerned in, as 

 bearing remarkably on the same occurrence, and the clear 

 indisputable sections at Boscastle; for so far as the ridge of 

 South Petherwin and Landlake is concerned, the superiority 

 of either killas or culm rocks might be argued, although the 

 balance of evidence certainly inclines to theYormer. If we take 

 a north and south traverse from Tresmarrow on the south- 

 west of Launceston, in the direction of Petherwin church, we 

 observe the culm slates to be bowed over in a low broad arch 

 of about a mile across, — ascending from the north at Tresmar- 

 row, being flat at " Quarry " on the south of it, and dippino- 

 south 12^ at " Does House" beyond, down to the brook be- 

 low, crossing which we come upon killas, at the foot of the 

 hill, which, being cut into for the road, shows it also to dip 

 easily to the south 10° to 15°. Before we leave this locality, 

 I request your readers will bear in mind, that about half a 

 mile west by north of South Petherwin church, and on the 

 north-east of Bolathan, the Coddon Hill grit is exposed, and 

 ranges distinctly from thence by Congdon, to nearly north of 

 Trevasper. 



Mr. Phillips, in his extremely valuable work on the " Pa- 

 laeozoic Fossils of Devon and Cornwall," has detailed with 

 such remarkable accuracy and fidelity all the structural pha'- 

 noiuena he oiet with, that I have great reason to lament his 



