Intelligence and Miscellaneous Articles. 435 



evidence whieh exists in the in-situ elvans for the development of 

 the most varied of these forms from a common magma. 



Special opportunities for the study of two of the elvanite dykes in 

 the neighbourhood of Tavistock have lately presented themselves. 

 The Shillamill elvan exhibits a centre composed of quartzose felspar- 

 porphyry graduating laterally through numerous varieties into 

 " claystone porphyry ;" whilst the Grenofen elvan retains the same 

 structure in breadth, but changes in length from a rock containing 

 so little felsitic matter that it is essentially a fine-grained porphyritic 

 granite to one with a compact semivitreous ground-mass, in which 

 felspars, quartz, and mica are porphyritically developed. 



As evidence afforded of the existence of distinctly volcanic rocks, 

 mention is made of a deposit of water-borne and water- worn detritus, 

 indicating a Dartmoor origin for a large portion of its constituents, 

 along with rolled flints and pebbles of Carboniferous, Liassic, and 

 Cretaceous limestone, with which were associated typical andesites 

 and specimens of volcanic grit such as arise from the denudation of 

 volcanic cones. This occurs on the limestone at Cattedown near 

 Plymouth, and bears testimony to a very ancient denudation. 



2. "The Basals of Eugeniacrinidse." By F. A. Bather, Esq., 

 B.A., F.G.S. 



3. " On some Polyzoa from the Inferior Oolite of Shipton Gorge, 

 Dorset." By E. A. Walford, Esq., F.G.S. 



LI. Intelligence and Miscellaneous Articles. 



THE SENSITIVE FLAME AS A MEANS OF EESEAECH. 

 BY W. LECONTE STEVENS *. 



\ LITTLE over thirty years ago the discovery was published in 

 -^ this Journal f that under certain conditions a naked flame of 

 illuminating-gas may become sensitive to sonorous vibrations. Nine 

 years elapsed before any development grew out of this acquisition 

 to science. La 1867 Mr. "W. F. BarrettJ, who was at that time 

 an assistant in the laboratory of the Eoyal Listitution, published 

 his independent discovery of the sensitiveness of flame ; and the 

 use of the manometric flame, in the hands of Eudolph Koenig, 

 was subsequently developed with great skill for the analysis of 

 compound tones. The use of Professor Barrett's flame has become 

 widely known, especially through the familiar volume of lectures 

 on Sound by Professor Tyndall. Govi in Italy, Barry in England, 

 and Geyer in America independently discovered the method of secur- 

 ing a sensitive flame, with no pressure higher than that of the ordin- 

 ary street mains, by causing air to mingle with the gas after it issues 

 from the nozzle, and allowing the mixture to burn after passing 

 through \\ire gauze. "While this flame may be made exquisitely 



* From an advance proof communicated by the Author, 

 t " On the influence of Musical Sounds upon the Flame of a Jet of Coal- 

 gas." By J. LeOonte. Phil. Mag. March 1858, p. 235. 

 X Phil. Mag. vol. xxxiii. pp. 216, 277 (1867). 



