16 ROCK-METAMOEPHISM. 



adhering aciculae ; c s the latter separated by vacant interspaces, 

 the separations having contained calcite before the specimen 

 was decalcified * : underneath, the chrysotile has been entirely 

 replaced by calcite, except in one place, as where the fibres re- 

 main attached to the subjacent layer of serpentine. In another 

 part of the same specimen the chrysotile retains its characteristic 

 features and colour ; but some of the layers are brown and 

 porcellaneous, and the fibrous structure is either faint or oblite- 

 rated. The layers, besides having the fibres (b) changed into 

 aciculse in close contact, have them forming solid pillars ; the 

 fibres are also transformed into aciculse, individually separated 

 by calcareous interpolations, and passing completely across a 

 layer or only reaching about halfway appearing, where the 

 interpolated lime is dissolved out, like a fringe hanging from 

 the adjacent surface, and in the same way as they are (c) in the 

 instance just noticed. 



In all the above cases we have clear demonstrations that the 

 typical ' ' nummuline wall " of ' ' Eozoon Canadense " is a pec- 

 tinated form of chrysotile, and consequently a product of purely 

 inorganic agencies. 



To continue, under polarized light serpentine differs impor- 

 tantly from chrysotile. The former in its ordinary state shows no 

 bright colours merely pale yellow, passing, on rotating the 

 analyzer , through light grey, dark or bluish grey, and returning 

 to pale yellow; whereas the latter (beginning with parallel 

 prisms) shows pale green, bright green, purple and blue, dull 

 green, purple and blue (with crossed prisms), crimson, yellow, 

 and green, returning to pale green, each change being variously 

 tinted the whole reminding one of the still more beautiful 

 colouring got by polarizing peridote. Calcite, which is often 

 associated with chrysotile, shows nothing but different shades 

 of grey j and when intermixed with chrysotile its presence 

 vitiates the bright colours of the latter mineral, turning them 

 into pale yellow and dark grey. 



Fig. 2, Plate II., represents a portion of one of three slides 

 received from Canada, specially selected for us, we suspect, by 

 one eminently distinguished for his advocacy of "Eozoon Cana- 

 dense" as proving the organic origin of the structures diagnosed 



* A similar case has been noticed by Prof. Heddle in amianthus from Unst, 

 in which "there is generally more or less fibrous calcite between the filaments 

 of the mineral" (' Mineralogical Magazine/ vol. ii. p. 33, March 1878). 



