355 



I. Minette-felsite : f mile from Windermere Station. 



II. Micaceous diorite : Gill Bank, 1J mile N.N.E. of Staveley. 



III. Micaceous diorite : Stile-end Farm, about 5 miles N. of Staveley. 



IV. Minette-felsite : Kendal Road, '250 yards from third milestone. 

 V. Minette-felsite : Railway, W. of Docker Garth. 



VI. Minette-felsite : Docker Fell ; S. of Haygarth. 

 VII. Minette-felsite : Docker Fell ; S. of Haygarth. 

 VIII. Miuette-felsite : Helm Gill, near Sedbergh. 



West of England. In his paper W on the " Rocks of the Mining 

 Districts of Cornwall " Mr. J. A. PHILLIPS describes a remarkable 

 "Elvan" from Trelissick Creek, north of Carrick Roads, near Falmouth. 

 The width of this elvan, which penetrates a greyish slate, is about 

 thirty feet. Its colour varies from yellow or buff to a dark 

 chocolate brown, in accordance with the less or greater degree to 

 which the iron present has become peroxidized. Its general appearance 

 is that of a rock composed of a large quantity of mica, with a little 

 felspar, enclosing occasional crystalline fragments of quartz. Under the 

 microscope thin sections are seen to consist of a nearly equal mixture 

 of quartz, felspar and brown mica enclosed in a felspathic base. The 

 felspar is monoclinic. A section in the British Museum prepared from 

 a rock from the same locality contains a nearly colourless augite in 

 addition to the constituents mentioned by Mr. PHILLIPS. Apatite and 

 octahedra of magnetite also occur. The rock is a typical augite- 

 minette. Mr. PHILLIPS' analysis is quoted below. 



It is to Mr. COLLINS that we are principally indebted for our 

 knowledge of the mica-traps of Cornwall. In the paper already 

 referred to he describes and records on a map thirty-five distinct 

 outcrops of mica-trap in a band of country lying between Roscreage 

 Beacon, three miles south of the Helford River and Watergate Bay, 

 near New Quay, on the north coast of Cornwall. The individual 

 dykes have, for the most part, a course about N.N.E., but they 

 are often somewhat tortuous and frequently split up into branches, 

 some of which have, for short distances, directions very different from 

 that mentioned. 



These dykes are evidently posterior to the main earth-movements 

 that have affected the rocks. They are in no way related to the 

 pre-granitic greenstones which they in some cases (e.g., Towan Head, 

 near New Quay) very closety resemble. It follows from the researches 

 of Mr. COLLINS that these rocks are similar in composition, 

 mode of occurrence, and geological age to the kersantites of 

 Brittany^ 2 ) and the Hartz/ 3 > to the lamprophyres^ (GUMBEL) of the 



(1) Q.J.G.S., Vol. XXXI. (1875), p. 337. 



(2) M. BAEEOIS. Sur le Kerzanton de la Rade de Brest. An. d. 1. Soc. Geol. du Nord. 

 T. XIV., p. 31. 



(3) K. A. LOSSEN. Uber die Kersantite-Giinge des Mittelharzes. Jahr. d. k. k. preuss. 

 geol. Landesanstalt fur 1885. MAX KOCH. Die Kersantite des Unterharzes. Jahr. d. k. k. 

 preuss geol. Landesanstalt fur 1886. 



(4) C. W. GUMBEL. Die paliiolithisohen Eruptivgesteine des Fiohtelgebirges. Miinohon, 

 1874. 



