1823.] the same Crystalline Form as Pyroxene. 231 



and a're afterwards white, and which are not fusible, or vv those fusi- 

 bility diminishes in the same proportion as the water *ey intern 

 increases depends upon an infusible mineral, which contains 

 water and in P the fire becomes first black and afterwards white, 

 loan stone and noble serpentine are easily recognised by the e 

 properties, and these with common serpentine occurring in 

 Seat quantity with the sahlite, it is clear that these varieUes of 

 sahhte are nothing but pyroxenes ; that is to say, bisihcates of 

 iTme and magnesut combined with variable mixtures of soap 

 stone or noble serpentine, of which the first is a r.sihcate 

 wfthou? water ; the latter a trisilicate with water. Neither soap 



tone nor serpentine has the least tendency to crystallization, 

 though both are chemical compounds ; they are, therefore 

 no obstacle to the peculiar crystallization of the sahlite, it 

 Slg already known from several' examples, that both soap stone 

 and terpentine possess a peculiar tendency to assume the crys- 

 talline form of other minerals.* 



Reddhh-brown Malacolite from Degaro, in Finland, analysed by 



Prof. Berzelius. 



Silica 50-00 containing oxygen 25- 15 



T • * 20-00 5-62 



Lime *v ")> 1-74 



Magnesia 4-50 ' J* 



Protoxide of iron 18*85 



Protoxide of manga- ^ 



Loss by heating 0*90 



97-25 



(To be continued.) 



Article XIV. 



Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



Jan 23 -The reading of Mr. Macdonald's Observations on 

 ifaZ&i was i-esumed g and concluded. . The P™cipaUubjecU 

 of them were the phenomena of the variation of the needle to 

 a count for which! an hypothesis in some reepecU .new, w as 

 nmnosed bv the author. It would appear, he observed, irom 

 &5 ^Parry's discovery of the north-west magnetic pole, and 



. M. Rosedistincdyfou^f^ 



