134 Mr. Levy on a neto Mineral Substance [Feb. 



of temperature be supposed to take place by additions of sing le 

 degrees, it is clear that the error must be immense. 



The gentleman is pleased to observe at the close of his paper, 

 that he has shown the failure of my attempt to correct the rules 

 which have been given for making the above calculation, and 

 that the one which I have proposed is not perfectly accurate. 

 How he has proved this, I am at a loss to discover ; but I ima- 

 gine that whether my results are accurate or not, his will form 

 no standard by which to judge of them. 



I am, Sir, yours respectfully, 



Matthew Biggs. 



Article XVII. 



Account of a new Mineral Substance. By M. Levy, Esq. MA. 

 in the University of Paris. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, Jan.20, 1824. 



At the suggestion of Mr. Heuland, I propose to give the name 

 of Bucklandite (in honour of the celebrated Professor of Oxford), 

 to a mineral substance, the crystallographical characters of 

 which I find to differ from any hitherto described. 



I have observed this new mineral upon a specimen belonging 

 to Mr. Turner's collection ; it was placed with the pyroxenes, to 

 which substance it has a great resemblance of form and external 



Fig. l. 



Fig. 



Fig. 3. 



characters. It occurs in small crystals represented by figs. 2 

 and 3 ; their colour is brown, nearly black, and they are opaque. 

 They easily scratch glass, and appear to me to be much harder 

 than pyroxene. I could not find any cleavage parallel to the 

 natural planes of the crystals, nor in any other direction. The 



