86 Prof. Maskelyne On New Cornish Minerals [Feb. 23, 



These solutions react powerfully acid, and readily decompose carbonates. 

 The analysis of this acid gave numbers closely corresponding with the 

 formula fC 2 H 5 



CH 3 

 H 

 O 



OH 



We have prepared silver ethomethoxalate by treating the free acid dis- 

 solved in water with carbonate of silver. This salt crystallizes in splendid 

 mammillated masses half an inch in diameter, which are tolerably soluble 

 in water. It gave numbers, on analysis, in accordance with the formula 



rC 2 H 8 

 CH 3 

 OH 



February 23, 1865. 



JOHN P. GASSIOT, Esq., Vice-President, in the Chair. 

 The following communications were read : 



I. "On New Cornish Minerals of the Brochantite Group." By 

 Professor N. STORY MASKELYNE, M.A., Keeper of the Mineral 

 Department, British Museum. Communicated by A. M. STORY 

 MASKELYNE, M.A. Eeceived February 13, 1865. 



(Abstract.) 



On a small fragment of Killas from Cornwall, I discovered, several 

 months ago, a new mineral in the form of minute but well-formed crystals. 

 The specimen had come from Mr. Tailing, of Lostwithiel, a mineral- 

 dealer, to whose activity and intelligence I am indebted for the materials 

 that form the subject of this paper. After a little while he found the 

 locality of the mineral, and sent me other and finer specimens ; but these 

 specimens proved to contain other new minerals besides the one already 

 mentioned. Two of these minerals are described in this paper, and a third 

 will form the subject of a further communication. 



I. Langite. 



The first of these minerals which I proceed to describe is one to which 

 I have given the name of Langite, in honour of my friend Dr. Viktor von 

 Lang, now of Gratz, and lately my colleague in the British Museum. It 

 occurs in minute crystals, or as a crystalline crust on the Killas, of a fine 

 blue with a greenish hue in certain lights. The crystals are prismatic. 

 The forms observed are (1 0), (0 1), (1 1 0), and (2 1) & (0 1 0), the 



