534 



assumed that when heated solutions containing calcareous matter, or 

 carbonates, penetrate the fissures, the adjoining serpentine will become 

 converted from a silicate into a carbonate ; and hence will be formed 

 isolated or variously connected grains, lumps, and layers of serpentine 

 (" chamber casts") ; while the separations are occupied by intercala- 

 tions of calcite, or dolomite (" intermediate skeleton"). Here and there 

 the surfaces of the grains, &c, will become concurrently platy, floccular, 

 or asbestiform : in the latter state the serpentine is converted into its 

 allomorph, chrysotile, in the form of an investing layer ; which through 

 further changes will become acicular, with the aciculi often removed, 

 and their places occupied by calcite, &c. (" nummuline layer"). The 

 calcareous intercalations between the granules, &c, will retain more or 

 less residual serpentine, which, if remaining chemically unchanged, will 

 become converted into white amorphous masses, parallel lamellae, solid 

 bunches of rounded filaments, cylindrical and broadly flattened rods — 

 simple and branching (" canal system"), characteristic of another allo- 

 morph, metaxite. As serpentine rocks are liable to all, or to only a 

 few of the above changes, depending on the various conditions under 

 which they may have existed, we do not apprehend any material ob- 

 jections to the principle" (there may be to minor points) of our hypothesis 

 from those who have paid attention to the subject ; we, consequently, 

 have the strongest confidence in the conclusion that " the combination of 

 an assemblage'' of " eozoonal features," in the rare instances in which 

 it occurs, is inseparable from ophite — that it is an inevitable and a 

 purely correlative phenomenon. The " eozoonal" rock of Petite Nation 

 certainly stands out prominently as a case in point : but the circum- 

 stance is due to no more than a concurrent development of the various 

 forms assumable by its protean mineral, serpentine, under favourable 

 conditions ; and it is no less paragenetic than is assuredly the case with 

 the " combination" occurring in chondroditic and pargasitic crystalline 

 limestones. 



It ought not to be expected that the phenomenon can be met with 

 except in rocks approaching mineralogically to ophite. There are not 

 many. Of the few that are known, we have shown them to present a 

 " combination" so strictly "eozoonal," and so conclusively demon- 

 strating the paragenesis of their ophitic types, as to leave nothing more 

 of the kind to be desired. 



Dr. Giimbel has made known a very curious fact, which has some 

 relevancy to the subject we are discussing. At Steinhag, in Bavaria, 

 there occurs " JEozoon" associated with the never-failing metamorphic 

 limestones, schists, and gneiss. The limestones ' ' often contain small 

 lenticular masses or nodules, consisting chiefly of scapolite, crystalline 

 and almost compact, measuring fifty by twenty millimeters, and even 

 much more, around which serpentine is arranged in a concentric 

 manner ;'' and "in the parts around these nodules" there were " some- 

 times distinctly observed tubuli, canals, and even indications of a shell- 

 like structure." Dr. Giimbel " could not satisfy" himself, " after nume- 

 rous examinations of fragments of such masses, whether" he " had to 



