STRUCTURES OF OPHITES AND RELATED ROCKS. 9 



Reserving a fuller description for the next Chapter, we shall here 

 give a brief notice of the different stages. 



First. In the incipient stage chrysotile, very unlike what it is 

 as usually represented, consists of a layer of colloidal serpentine 

 penetrated vertically by separated thread-like lines *. 



Second. The lines are increased to an indefinite extent, dividing 

 the layer so as to destroy its ordinary serpentine character, and 

 making it to consist of a dense mass of fibres f : this constitutes 

 typical chrysotile. 



Third. The fibres have become definitely acicular, and are in 

 close contact I . 



Fourth. The fibres or rather aciculse (as they must now be 

 called) are more or less separated by interspaces filled in with 

 calcite. 



These four modifications are represented by the divisions 

 lettered , 6, c, d in fig. 1, Plate IX. Other modifications 

 occasionally occur, as the complete fusion of the fibres into a 

 solid mass, which may retain traces of the original fibrosity, or 

 have lost them altogether. 



It may now be mentioned that the acicular modifications cor- 

 respond to one of the essential structures, the (' ' tubulated ") 

 <( nummuline wall/' of what was once generally believed to be 

 a gigantic fossil foraminifer, \\z."Eozoon Canadense" 



Ophites frequently consist of interlamellations of serpentine 

 and calcite (or the latter may be miemite) , with little or no chry- 

 sotile. Attention will be drawn to cases of the kind hereafter. 



Serpentine frequently exhibits a cracked structure, which, 

 though we hold gives rise to some important features, cannot 

 be considered a physical character proper to it. The cracks, 

 varying much in width, are in general exceedingly irregular : 

 often they are confusedly reticular, curving, and radial, and in 



* See Quart. Journ. Geol. Soc. vol. xxii. pi. xiv. fig. 2 o j Proc. Eoy. Irish 

 Acad. vol. x. pi. xli. fig. 2 a ; also this work, Plate IX. tig. la. 



t See Plate IX. fig. 1 6. 



J See Quart. Journ. Geol. Soc. vol. xxii. pi. xiv. fig. 1 (closed aciculse) ; 

 Proc. Eoy. Irish Acad. vol. x. pi. xli. fig. 1 c ; Ann. & Mag. Nat. Hist. ser. 4, 

 vol. xiv. pi. xix. fig. 4 a ; also this work, Plate IX. fig. 1 c. 



See Quart. Journ. Geol. Soc. vol. xxii. pi. xiv. figs. 1 & 4 (separated 

 aciculse) ; Proc. Roy. Irish Acad. vol. x. pi. xli. fig. 2<?j Ann. & Mag, Nat. 

 Hist. ser. 4, vol. xiv. pi. xix. fig. 4 6 j also this work, Plate IX. fig. Id. It is 

 necessary to mention that tKe last figure cited in these notes diagramma- 

 tically represents the changes of chrysotile, 



