and Geology of Lake Ontario. 87 



Country ; the primitive marble of Crow Lake and the Ottawa 

 is plentiful on the north main of Ontario : the ophicalcic rocks, 

 and tabular spar in large masses of Gananoque and the river 

 just mentioned, are occasionally met with. Where the blocks 

 of glassy tremolite occurring near Bellville come from, I know 

 not. The tabular spar I found at this place, and a few miles 

 east of Grimsby near the head of the lake. The ophicalcic 

 boulder several tons in weight is on the beach in front of the 

 town of York, a few yards from a minutely blended mass, 

 weighing about two tons, of petalite, glassy actinolite, tremo- 

 lite, quartz, calcspar, and a little copper-pyrites. 



The first two of these substances only require remark. They 

 have been described by Dr. Troost* in the following words: 

 The petalite " occurs in crystalline masses of a grayish white 

 colour, with a tinge of green. It has a confused lamellar tex- 

 ture : the laminae offer in some directions a radiated texture, 

 not unlike some varieties of tremolite, approaching even to 

 fibrous, as observed in the asbestiform actinolite; the fibres 

 are diverging; the laminae are sometimes scaly and undulated. 

 The cleavage approaches to a rhomboidal prism of 130°, which 

 has again a diagonal cleavage. It breaks with difficulty, offer- 

 ing a rough lamellar and fibrous fracture ; the fragments are 

 angular with a glistening lustre, and in the direction of the 

 laminjE somewhat pearly, more or less brilliant. It is strongly 

 translucent on the edges, and strikes fire freely with steel ; 

 nearly of the same hardness with feldspar. Its specific gravity 

 is 2'593. It melts with difficulty into an opaque white porous 

 enamel ; with borax, it gives a transparent glass. I fused a 

 small quantity of the mineral with potash, dissolved the pro- 

 duct in muriatic acid, and then evaporated it to dryness, and 

 digested the mass in alcohol, by which it was partly dissolved 

 and formed a solution which burned with a red flame, of a 

 more dense colour than that of strontian. The quantity which 

 I subjected to analysis was too small to enable me to ascertain 

 the quantity of the lithia, and the proportion of the other in- 



fredients. The actinolite which covers the petalite is very 

 andsome : it seems to be a vein in which the crystals of ac- 

 tinolite of a fine green colour are cemented together by la- 

 mellar carbonate of lime. The crystals are nearly transparent, 

 almost cylindrical, with the exception of a few which belong 

 to the bis-unitaire, and the tri-unitaire of Haiiy ; the same 

 form as those which are found at Franklin, New Jersey." 

 [To be continued.] ' 



• Journal Acad, of Sciences, Pliiladelphin, vol. iii. p. 2.15. 



XII. On 



