Royal Society. 473 



common temperatures and at the proper degree of concentration 

 this substance shows two luminous bands, one of which is very 

 intense and embraces the whole of the red and yellow, and part of 

 the green ; the other, comparatively weak, is situated in the violet. 

 On applying heat, this violet band gradually diminishes in in- 

 tensity, and two new bands of absorption, of which previously 

 no trace was visible, appear in the red. They increase very 

 rapidly in breadth, especially the less refrangible of the two, as 

 the temperature rises; so that, when the boiling-point is ap- 

 proached, they have completely obliterated the entire bright 

 band in which they appeared, with the exception of a very nar- 

 row weak stripe in the extreme red. 



In order to explain these phenomena, one might be disposed 

 to assume that the elevation of temperature occasioned chemical 

 changes to take place in the liquids — that, for instance, a few atoms 

 of water were fixed or given off — were it not that, so far as the 

 observations have yet gone, a sudden alteration of absorbing- 

 power never occurs, but the changes take place in a perfectly 

 gradual manner. 



On the other hand, these phenomena are quite analogous 

 to those observed by Brewster* and others in relation to the ab- 

 sorbing-powers of certain gases, in which, as the temperature 

 rises, the absorption-bands increase in number and width. 



LXV. Proceedings of Learned Societies, 



ROYAL SOCIETY. 

 [Continued from p. 398.] 

 Feb. 23, 1865. — John P. Gassiot, Esq., Vice-President, in the Chair. 

 rjlHE following communications were read: — 

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

 Professor N. Story Maskelyne, M.A., Keeper of the Mineral Depart- 

 ment, British Museum. 



On a small fragment of Killas from Cornwall, a 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 con- 

 tain 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 



* Phil. Mag. S. 3. vol. viii. p. 386. 

 Phil Mag. S. 4. Vol. 29. No. 198. June 1865. 2 1 



