EEMNANTS OF EXTINCT VOLCANOES. 451 



last year, which was full of suggestions and an admission that 

 no one man can solve the question, as it required the combined 

 efforts of many workers under the direction of a skilful general. 



As a Cornishman I am desirous that the problems of our 

 rock formations should be solved, and am willing to devote all 

 the time I can conveniently spare to the subject, feeling assured 

 that it can never be solved on the carpet, but by theoretical 

 knowledge on the one hand, with practical work in the field, the 

 laboratory, and the use of polarized light on rock sections. 

 This course of action I have followed for many years, and still 

 intend to pursue. 



Black Head. 



The bold headland to the east of Mevagissey Bay, known 

 as the Black Head, is marked on the coloured Ordnance Map 

 as greenstone, or igneous rock, but on visiting it recently I found 

 it to be a member of the Upper Silurian, or old E,ed Sandstone. 

 Immediately overlaying it is a fine clay slate, in which, about 

 nine years ago, I found a fine fossil ( Orthocera») which I presented 

 to this Society and which is preserved in its Museum. Fossils 

 are still to be found in abundance near the Black Head in a fair 

 state of preservation, and it is, I believe, the only place where 

 they have as yet been discovered in this formation in West 

 Cornwall. With these formations of sandstone and clay slate 

 I am fully acquainted, from their extension from the Black Head 

 on the east, to Barkles Shop, St. Agnes, on the west. From its 

 line of strike through the parishes of Ladock, St. Erme, St. 

 Allen and Perranzabuloe, I have obtained during the last twenty 

 years many thousand yards of road metalling : I incidentally 

 mention this to show that 1 have had a lengthened opportunity 

 of becoming familiar with these rocks, and so could not be easUy 

 mistaken as to their character or nature. 



TOLCARN. 



Tolcarn, in the parish of Gorran, situated a little to the north 

 of Caerhayes Castle, is marked on the coloured Ordnance Map 

 as greenstone, I specially visited this place, as I had done the 

 Black Head, on the 22nd November, 1888, to obtain specimens 

 and to refresh my knowledge of the geology of the district. 



