82 Essay on the Transiiion Rocks of the Caiaraqui. 



It is on the exposed surfaces of this rock, particularly on the low 

 shores of the lake on the south side of Kingston, that we find those 

 beautiful masses imbedded, which have excited so much enquiry and 

 which were alluded to in a former number of this Journal. 



They are composed of a mixture of barytes, strontian, crystallized 

 carbonate of lime, iron pyrites and zinc ; sometimes the first two in- 

 gredients alone are present; sometimes the mineral is apparently a 

 component part of the rock, at others it is evidently a mere ball or 

 mass enveloped by it and easily detached. Occasionally the car- 

 bonate of lime is slightly yellow or flesh colored, but the crystals, 

 always large and without distinct form, are generally in curved layers 

 and magnesian, Masses as large as a man's head have recently been 

 discovered, and these, when broken, present some beautiful speci- 

 mens, the blades or fibres shining with the lustre of new satin. 



This substance was supposed, for a long time, to be tremolite, and 

 certainly it bore the outward look of that species named after Lake 

 Baikal, but its obvious specific gravity should have caused doubt ; it 

 was first described in the opening volume of the Transactions of the 

 Quebec Society of Natural History, and from the specimen 1 used 

 in analysing it, I had every reason to believe that it was a sulphate 

 of barytes. Since that time a very attentive mineralogist, Mr. Bad- 

 deley, has given an account of it in this Journal, and pronounced it 

 to be strontian. The question is however decided ; both were right 

 and both were wrong, and a conjecture hazard^ed in the interim has 

 been verified by Professor Thomson, to whom the mineral wa^ sent 

 by the Secretary of the Montreal Natural History Society, It is 

 stated by that eminent mineralogist to be a new substance, and he 

 proposes to call it baryto-sulphate of strontian."^ I am not, however, 

 yet convinced but that many specimens of this substance contain pure 

 sulphate of barytes only, in some of their portions, whilst others con- 

 sist also of pure sulphate of strontian, although I am perfectly ready 

 to admit that the masses generally are those of the new substance 

 thus named. f 



(To, be continued.) 



* According to the Proiessor's analysis, it contains elevea atoms of strontian and 

 five of baryta. 



t In a communication to Dr. Holmes, I had previously suggested that it might be 

 a harytic sulphate of strontian, as I lelt convinced that Mr. Baddeley's opinion' as 

 to the strontian was correct. Witli respectful deference to the Professor, I think 

 Xinsstonitc would not be a bad name for it. 



