198 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 10, 



Plate XIV., which shows the layer flocculent here and fibrous there : 

 in the latter state the constituent aciculi are generally parallel, and 

 in one place divergent*. Such examples clearly form independent 

 and decisive testimony in favour of the conclusion we have come 

 to with respect to the corresponding structural modifications pre- 

 sented by the granules of serpentine in Grenville Ophite — that they 

 are allomorphic conditions of one and the same substancef. 



With respect to the cases of isolated rods, and other modifications of the 

 asbestiform layer, Dr. Carpenter has incidently mentioned that this part "is 

 often thrown off by the disengagement of gas in the process of decalcification"}. 

 Instances of the kind have occurred to us in the specimen presenting the double 

 layer : loose fibres are seen hanging on the free side of the outer one ; and the 

 innermost is for a considerable extent separated from the surface of the granule. 

 We have also seen portions of the flocculent coat lying loose in the decalcified 

 passages, and others raised above the plane of the section. At one time we 

 were disposed to believe that decalcification, likewise internal movements which 

 the rock has evidently undergone, as well as mechanical action consequent on 

 breaking, grinding down, and otherwise preparing specimens for examination, 

 had mainly contributed to produce the cases under notice ; but we are now more 

 inclined to consider them for the most part to be the result of other agencies. 



It has been made clear that Serpentine is transformed into both the asbesti- 

 form. layer and the flocculent coat, and that the former of these epigenes is 

 converted into the latter. Was the process elaborated solely during some 

 remote " primordial " period ? Had the Grenville Ophite precisely the same 

 structure it now possesses previously to the deposition of the rocks transgressive 

 to it§? Has it remained chemically and structurally unaltered during the 

 immensity of time which has intervened between the Potsdam (Cambrian) 

 period and the present epoch ? We are certainly strongly indisposed to answer 

 in the affirmative to these questions. For why may not pseudomorphic, allo- 

 morphic, and other metamorphosing actions, induced by heat, pressure, elec- 

 tricity, gaseous and hydrous permeations, have been going on throughout all 

 such time, more or less changing the Serpentine into flocculent matter, trans- 

 ferring the latter from the granules, and replacing it by their imbedding calcite, 

 or inter mixuig it with the latter body, or variously substituting the chemical 

 constituents of the Serpentine by their isomorphous compounds? These re- 

 marks express our hypothesis as to the changes which have been and are being 

 effected in the essential minerals of "Eozoonal" Ophite, and we believe that it 



* So many instances have occurred to us, showing the changes mentioned in 

 the text, that we could readily fill a Plate with them. We could have shown 

 much finer examples of the asbestiform layer ; but the one selected for illustra- 

 tion has been given because it shows, what is rare, the parallel and divergent 

 aciculi associated on one granule. 



t Professor Tennant has kindly presented us with a beautiful " moss agate " 

 of transparent chalcedony, enclosing a number of vermicular bodies, variously 

 knotted, which appear to be composed of yellowish ferruginous matter ; in 

 some cases they are completely invested with a dense crop of subparallel acicular 

 crystals, seemingly of the same substance, which penetrate the chalcedony, and 

 form a well-defined coat remarkably uniform in thickness (see fig. 16, Plate XV.). 

 This case is a proof that certain substances shoot out from the surface of the 

 body they form, as crystals, and, as such, penetrate a dissimilar surrounding 

 medium, in a fluid, gelatinous, earthy, or otherwise yielding condition. A similar 

 origin might with some reason be advanced to account for the aciculi on the 

 granules of Serpentine ; but we regard the conclusion already adopted as too 

 clearly established to be induced to entertain any other. 



j Intellectual Observer, vol. vii. p. 292. 



§ We allude to the Potsdam sandstone, beds of which occur, both in Canada 

 and in the northern parts of the State of New York, unconformably overlying 

 highly contorted Laurentian rocks, and composed in many places of pebbles of 

 the latter in their metamorphosed condition (see Geology of Canada, p. 96). 



