338 Dr. How on the Mineralogy of Nova Scotia. 



2* 71. In the following analysis, although the finely powdered 

 mineral was fused with about four times its weight of the mixed 

 alkaline carbonates, the alumina was not perfectly separated from 

 the silica, but the quantity retained was not large enough to be 

 material. The presence of potash and soda was proved by fusion 

 with chloride and carbonate of barium, and subsequent testing 

 with bichloride of platinum in alcohol. The iron is given as 

 protoxide, because it was found that after fusion an exceedingly 

 small amount of peroxide was present, which might have been 

 formed in the process. The results obtained were — 



Silica (retaining a very little Al 2 O 3 ) 60*53 



Alumina . . . . 23-01 



Protoxide of iron 5*30 



Potash and trace of soda .... 4*39 



Magnesia 1*42 



Water 5-35 



10000 



which have a general accordance with those found in the analyses 

 of clay-slate given by Dana (Mineralogy, 4th edit. p. 510), one 

 of which is as follows, the specimen examined being a bluish- 

 black clay- slate from Rothwaltersdorf : — 



Silica 61-72 



Alumina 19*55 



Protoxide of iron . . . 8 "54 



Lime 0*55 



Potash 4-81 



Magnesia 1*08 



Water 3*74 



99-99 

 They do not tally with those given as calculated from the for- 

 mula assigned to agalmatolite by Nicol (Mineralogy, p. 227), 

 viz. — 



Silica 55-00 



Alumina 33*00 



Potash 7*60 



Water 4*40 



100*00 

 with whicfy mineral, however, the Merigomish pencil-stone 

 agrees in its softness, texture, and colour. It is decidedly differ- 

 ent from the "pencil-slate" of Von Cotta (Rocks Classified, 

 p. 264), which he describes as separated or separable into pen- 

 cils. Very characteristic specimens of this were found some 

 years ago by Dr. Dawson and myself in lower carboniferous 

 rocks at Horton Bluff, at the mouth of the Avon, N.S., in a 



