Account of a nezo species q^ Mineral named Polybasite. 149 



sulphur taken up by the antimony and arsenic, for the sulphuret 

 of antimony and sulphuret of arsenic, are = 1.90 and ^.40; al- 

 too-ether 4.30. The silver takes up 9.56 of sulphur, in order to 

 form the sulphuret of silver, and the copper 2.53 sulphur to 

 form the sulphuret of copper. The quantity of sulphur is three 

 times greater in the electro-positive metallic sulphurets than in 

 the electro-negative ; the quantity of sulphur in the sulphuret of 

 silver and sulphuret of copper is as 4 : 1. The formula for the 

 compound can therefore be expressed as follows : — 



Cop. 9. 1 ^„,* -1-4 A 9^ 



S6 



ra 



A* 



In this compound, therefore, the sulphuret of antimony and 

 the sulphuret of arsenic are combined with the greatest quantity 

 of base, and hence the name Polybasite, given to this species, 

 from vtXvi and fi»<rii. 



Zhikenite. — Rose refers this mineral species to the prismatic 

 series of CrystaUisalion, and Hartmann, in his interesting popu- 

 lar Lectures on Mineralogy, does the same. Lately, the last 

 mentioned author informs us, that he has fully confirmed this 

 opinion, by finding crystals in the form of rhomboedral prisms, 

 bevelled on the extremities ; the bevelling planes set straight on 

 the acute lateral edges of the prisms ; the crystals grouped as 

 in arragonite. In opposition to this statement, we have that of 

 Mohs, (in Partsch's Catalogue of the Vienna Imperial Cabinet), 

 and of Haidinger (Anfansgrunde der Mineralogie), who 

 maintains that Zinkenite belongs to the Rhomboedral System. 



On the Egg of' the Ornithorynchus. 



IVX. Geoffeoy St Hilaire lately communicated to the 

 Academy of Sciences, a letter containing the figure and 

 description of an Ornithorynchus's egg. At the same time, 

 he made some remarks on the discussions which have arisen 

 among the naturalists of Europe, respecting the classifica- 



