Dr. H. A. Nicholson — Geology of Ingleton. 213 



ment. Mr. Gregory told me his object was not to search for dia- 

 monds, but for nickel and other minerals usually found associated 

 with them, and that he intended visiting the Namaqua land mines 

 before he returned. His motives and objects, and those of his friend 

 the diamond merchant, Mr. Emmanuel, are now but too apparent. 

 Why all this attempt at mystification, unless he had a purpose to 

 serve ? 



VI. — Notes on the Gkeen Slates and Porphteibs of the Neigh- 

 BOUKHOOD OP Ingleton. 



By Henry Alletne Nicholson, D.Sc, M.B., F.G.S, 



THE occurrence of certain of the Lower Silurian Eocks of the 

 Lake-district beneath the Scar Limestone of Yorkshire, on a 

 line between Ingleton and Settle, has been long known, and has 

 been noticed both by Professor Phillips (Trans. Geol. Soc. 2nd series, 

 vol. iii. p. 1), and by Professor Sedgwick (Quart. Journ. Geol. Soc. 

 vol. viii. p. 35). More recently the rocks in question have been 

 shortly described in a paper by Mr. Hughes, of the Geological Survey 

 (Geol. Mag. Vol. IV. p. 346). Having had the opportunity of visit- 

 ing Ingleton in company with Professor Harkness, and subsequently 

 alone, I have collected the following brief notes of the Silurian strata 

 which are seen in that locality, and which belong to the Green Slates 

 and Porphyries of the Lake-district. 



The section which I propose to describe is the one afforded by the 

 Dale Beck, which runs to the north-west of Ingleborough from 

 Chapel-le-Dale to Ingleton, and is in length between one and a half 

 and two miles. In the course of this stream the Silurian Eocks have 

 been exposed by denudation, and are seen, in a remarkably clear 

 section, to be unconformably overlaid on both sides of the valley by 

 nearly horizontal beds of Scar Limestone. The section appears to 

 be an ascending one down the valley, and the following is the 

 sequence of the beds exhibited. 



I. The highest beds exposed in the valley are a series of ordinary, 

 cleaved, felspathic ashes, or Green Slates, with some intercalated 

 trappean beds, the whole striking N.W. and S.E., and having a 

 nearly vertical cleavage. 



II. These slates are succeeded to the S.W. by a fine-grained, 

 greenish-gray felspathic trap, in parts slightly hornblendic and 

 micaceous. This trap is continued nearly as far as Dale-barn, form- 

 ing opposite this point a series of well-marked glaciated bosses. 

 Here it has intercalated in it a band of slates about 30 feet in thick- 

 ness, and it assumes a slaty texture in parts. Above this slate- 

 band the trap in places becomes highly porphyritic, consisting of a 

 green felspathic base, containing numerous crystals of red felspar, 

 with masses of crystalline quartz, specks of hornblende, and flakes 

 of mica. Its composition, however, is very variable, and it passes 

 directly into fine-grained trap on both sides. Blocks apparently of 

 this porphyritic trap are found nearly a mile and a half down the 

 stream ; but these are much more highly quartzose in composition, 



