112 Baden Powell — Igneous Rocks of Ckarnwood Forest, 



Nomenclature. — The map of the Geological Survey marks granite 

 at Mount Sorrel; syenite at Bradgate, Markfield, and other places. 

 In the margin of the map they are both classed as igneous rocks. 

 But in the Museum of Economic Geology, specimens from all 

 (except Mount Sorrel, from which there is no specimen) are arranged 

 under the name of altered rocks. Mr. Jukes describes them all as 

 syenite. In the Museum there is a specimen described greenstone from 

 Quorndon. This, I presume, is from the quarry in Buddon Wood, 

 which is part of the Mount Sorrel mass. I have found specimens 

 closely resembling greenstone in the Mount Sorrel quarries. In 

 fact, among specimens collected from all these quarries, many are 

 found exactly alike from the most distant localities, while, in the 

 very same rock, varieties so distinct may be found that it might be 

 described by the most different designations. Even in the same 

 specimen, there is often a transition from the most coarse-grained 

 mottled white or pink syenite to the most compact mass resembling 

 greenstone. 



The nomenclature of igneous rocks has confessedly been ill-de- 

 fined. But, perhaps, recent remarks rather lead to a general disre- 

 gard of such distinctions, and to giving more prominence to the idea. 

 so strongly supported by the researches of Mr. Marshall and others 

 (British Association, 1858, and Prof. Phillips' address to Geol. 

 Society, 1859), that they are all simply varieties of a very few 

 primary types under different conditions of fusion. 



Still there is the material question involved, how far any given 

 rock is properly a deposit or sedimentary formation, remaining as 

 such even though much dislocated and disturbed, but which has been 

 altered in its constitution perhaps totally by the action of heat from 

 below, — and how far it is an original fused or hypogene mass carried 

 up, in a fused state, by eruptive action into its existing position 

 among, and breaking through, other rocks. In the phenomena pre- 

 sented by the rocks of Charnwood and its neighbourhood there are, 

 confessedly, many problems of this kind still open for investigation. 



Localities of Igneous Action. — Commencing with the admitted 

 purely eruptive masses of Mount Sorrel,^ including the hills of 

 Buddon Wood, adjoining to Quorndon, and several minor outbursts 

 of the same syenitic or granitic rock, upon and adjacent to Mount 

 Sorrel Common, indicating the general substratum, — we trace a 

 remarkable continuous development of the same rock in a S.W. 

 direction, at the top of Kirksley hill, along its side, at the farm, 

 at its base, and lastly, at Brazil or Basil Wood, in the valley ; 

 within half-a-mile of the village of Swithland, and at about the 

 same distance from the commencement of the slate district to the N. W. 



Brazil, or Basil, Wood. — This locality is one of peculiar interest. 

 The Geological Survey accurately marks three patches at this spot, 

 as igneous. 



^ The syenite of Mount Sorrel has yielded several minerals, amongst which may 

 be mentioned Molybdenite [sulphur et of Molybdena), by no means of common occur- 

 rence in England. Associated with it, in the same quarry, occur copper and iron 

 pyrites, the latter but sparingly distributed. These minerals appear to occupy de- 

 finite planss, or points, in the syenite.— R. E. Geol. Mag., Vol. III., p. 525. 



