196 PHOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 10, 



pletely adhere to one another by their sides : besides, the latter im- 

 perceptibly pass into the state of an indefinitely fibrous layer. The 

 examples, and they are numerous, to which reference is made, clearly 

 show that these modifications belong to one form of crystallization, 

 and cannot be the result of " nummuline tubulation." But in order 

 to place our conclusion beyond the shadow of a doubt, we shall add 

 another demonstrative evidence to the number already adduced. 



We have repeatedly seen fissures in the serpentine — true cracks 

 striking right across a number of " chamber-casts " and the inter- 

 vening calcareous skeleton — filled with calcite and fiocculent matter, 

 separated and intermixed. The conditions of these examples incon- 

 testably prove that the latter substance is a modification of the 

 serpentine, and the former an infiltration. One of our specimens 

 from Lisoughter, which is decalcified, shows the phenomenon most 

 instructively ; a portion of the fiocculent matter still remains, and 

 the calcite has disappeared. But this is not all : considerable portions 

 of the walls of the fissure are crowded vdth as fine examples of 

 isolated perpendicular parallel aciculi and rods (the latter consisting 

 of asbestiform fibre) as those composing the so-called " proper wall " 

 of the adjacent " chamber-casts " * ! It is unnecessary to add another 

 sentence by way of evidence or argument in opposition to the view 

 which ascribes the asbestiform layer to pseudopodial tubulation f. 



Evidences strongly in favour of the conclusion that the " chamber- 

 casts " and " proper wall " were never otherwise than composed of 

 one and the same mineral substance, have occurred to us in Ophite 

 from Donegal and from the State of Delaware ; the granules of 

 serpentine, in the former of a dark-green colour, and in the latter 

 quite yellow, may be observed passing imperceptibly and completely 

 into the asbestiform condition. We also find exactly the same change 

 in Ophite (from Snarum in Norway) wholly devoid of anything like 

 organic structure : a specimen now before us shows here and there 

 its essential mineral, serpentine, becoming changed into films struc- 

 turallj'' indistinguishable from the asbestiform covering of " eozoonal " 

 sarcode -chambers, even often presenting its identical intermitted and 

 incipient crystallization. More cogent evidence could not be adduced 

 to prove that the " proper wall " is no other than an allomorphic 

 phenomenon. 



A strictly identical case, however, and one which may be regarded 

 as conclusively proving the original mineral nature of the " proper 

 wall," has occurred to us in another mineral. Chondrodite, a spe- 



* See Plate XIV. fig. 4, magnified 110 diameters. In this particular example 

 the aciculi on one of the walls of the fissure are exceedingly minute, being with 

 difficulty detected except under a power of 210 ; similar aciculi are interspersed 

 amongst the larger kind on the opposite wall. The large aciculi at one part of 

 the wall are closely crowded together : from this condition they graduate into 

 a compact layer indefinitely fibrous. 



t M. Delesse mentions a fact which equally shows the fallacy of the view 

 taken by Rhizopodists as to the origin of the asbestiform layer. The Ophite of 

 Xettes, in the Vosges, contains nodules (les rognons) possessing the mineralogical 

 characters of granite, surrounded by an envelope composed of radiately fibrous 

 chrysotile (see Ann. des Mines, 4^ ser. tome xviii. p. 335). 



