408 SKY. MINERALS. 



serious investigation to mineralogists, when their science 

 shall have made further progress. 



The mealy variety occurs under different aspects, by 

 which its nature is in some measure illustrated. This 

 condition has, I believe, been generally attributed to the 

 loss of its water of crystallization, the result of decompo- 

 sition. It is obvious however that this is not the cause, 

 since the specimens of this variety are found in the centre 

 of solid nodules of the glassy or compact kinds, where 

 neither air nor water can have access, and where they are 

 accompanied by crystals of absolute transparency : they 

 are also found intermixed with and investing solid nodules 

 of the toughest varieties, deeply imbedded in large masses 

 of rock where the elements are effectually excluded from 

 them. There are three principal forms of this variety. 

 In the first it is disposed in a radiated or rather in a 

 ramose manner, in fine fibres possessing the peculiar 

 lustre and softness of the finest white pulverulent tulc. 

 In a second case it forms distinct globular concretions 

 of extreme minuteness, not to be discovered without the 

 aid of the lens ; and in a third instance, which I observed 

 near Loch Eynort, a mass of globules of solid radiated 

 nadelstein, very much resembling some of the oolites, is 

 intermixed throughout with farinaceous scales of the same 

 substance having the greasy aspect and lustre already 

 described. 



In speaking of this latter variety I have ranked it with 

 nadelstein : it appears to have been formerly placed with 

 the mesotypes, partly because it is found associated 

 with them, and partly because of the theoretical views 

 which have been held respecting its origin. It will be 

 for mineralogists of more authority to consider whether 

 it does not deserve a separate place as a species: the 

 question is not of a nature to be determined by geometri- 

 cal analysis, as far at least as the varieties already found 

 extend ; and the delicacy and uncertainty of unassisted 

 chemical analysis in questions of this nature, are far too 



