547 



straight, bent, or twisted — nodulose, or irregularly excavated. These 

 configurations exactly answer to certain of the so-called " stolons."* 



It may be contended, by those from whom we differ on the question 

 discussed in these pages, that the specimen belongs to an" eozoonal" 

 rock. But, apart from its fatal agreement with other specimens of the 

 kind in possessing the never-failing crystalline or metamorphic charac- 

 ter — how, on such a view, are we to set aside the clear evidences of the 

 " chamber casts" and the " stolons" having been originally crystals ? 



Besides, not only have these parts had a crystalline origin, but it is 

 equally plain that the same conclusion must embrace the " canal 

 system ;" for it is impossible to detect any line of demarcation between 

 the " stolons" and the latter. Dissolving action has, in the first place, 

 converted the crystals of malacolite into the " stolons :" next the crys- 

 tals were divided by cleavage, and eroded to such an extent that, in the 

 state of the " canal system," they became reduced to mere skeletons.f 

 Eespecting the beaded character of the branching forms, we are strongly 

 inclined to believe that it has resulted from the cleavage which trans- 

 versely cuts the prisms : obviously the erosion would be deepest where 

 it was present. 



In no instance have we detected any traces of the " nummuline 

 layer" on the grains — a deficiency we attribute to their component mi- 

 neral, coccolite, not assuming the fine asbestiform structure which so 

 eminently distinguishes serpentine in its change into chrysotile. There 

 is often, however, a thin whitish granular coat investing the grains, 

 sometimes so compact as to remain after they have been accidentally 

 detached from the matrix. 



Another specimen, which is from Amity, New York, consists of a 

 similar calcareous matrix, holding spinel, chondrodite, serpentine, a 

 micaceous mineral, and malacolite. One of the crystals of spinel is a 

 compound octahedron, about two inches in its axial diameters, having 

 part of its faces built up of minute triangular facets, and others, of 

 small implanted octahedrons ; both lying parallel to the faces of the 

 large crystal. Numerous linear chinks, and irregularly formed cavities, 

 separate the component triangular facets and octahedrons ; and they are 

 filled up with micro = crystalline calcite, similar to that of the matrix, 

 enclosing malacolite. Decalcification brings out beautifully the last- 

 named mineral, which assumes with wonderful exactness all the charac- 

 ters and modifications of the " stolons" and " canal system," as displayed 

 in the Aker specimen ; so that the description we have given of them 

 would have to be repeated if we described those under consideration : 



* See Carpenter, "Quarterly Journal of Geological Society," vol. xxi., PI. VIII., 

 fig. 3, PI. IX., fig. 3 ; Jones, " Popular Science Review," vol. iv., PI. XV., fig. 5. 



f It may be bypothetically suggested that, in the final stage, the crystals have been 

 totally dissolved. Malacolite consists, in round numbers, of silica 55 - , lime 28", mag- 

 nesia 17* Assuming carbonic acid to have acted as the solvent, this substance might 

 completely replace the silicic acid, and in this way change the basic constituent of the 

 mineral ; making calcite (or dolomite) a pseudomorph after malacolite. 



