526 



Returning, for a moment, to the answer already given in a previous 

 section,* as it is equally applicable to the present case; we shall simply 

 reply to the " metamorphic" portion of Dr. Carpenter's argument, 

 by offering an example, selected from a number of the same 

 kind, to be seen in one of the cracks (c x., in Fig. 4), previously 

 noticed ; and which is represented in Fig. 5 (PI. XLII.) as seen by 

 a power magnifying 210 diameters. The two walls of this crack 

 (C), which intersects a layer of " chamber casts united into a 

 continuous horizontal lamella, are" crowded with both compact (c) 

 and separated aciculi (d) ; the latter cylindrical, parallel, and as much 

 "true casts of pseudopodial tubuli" as any that are known to form 

 the " nummuline layer." So we may safely defy every attempt to 

 make the argument, based on this example, present any other than 

 the " inorganic" side. Again, how does Dr. Dawson treat the 

 example described and figured in our Paper? The occurrence of 

 " veins of fibrous serpentine or chrysotile," occurring in Canadian 

 ophite, is mentioned ; but evidently the cases " which were well known'' 

 to Dr. Dawson are not the same ; since, " under a high power, they 

 resolve themselves into prismatic crystals in immediate contact with 

 each other ;"f whereas the one we brought forward, when similarly 

 magnified, is seen, and it was stated so, to contain aciculi, not only 

 in close contact, but separated !% 



We have represented in Figure 6 (PI. XLII.) another example, occur- 

 ring in Connemara ophite, interesting as throwing further light on the 

 changes characteristic of serpentine. It consists of a vein (a) intersecting 

 a considerable mass of this mineral. As in numerous other cases, the 

 serpentine here and there changes in colour, graduating from translucent 

 dark green to a pure opaque white ; while in many places it is colourless 

 and transparent. Near one end (upper part of the figure) the vein 

 strikes through a cluster of granules (" chamber casts") of green 

 serpentine, above which it can be traced for a short distance (though 

 too high to be represented), gradually thinning out. In the opposite or 

 downward direction, it intersects a mass of compact serpentine, and 

 terminates in a large cavity (A). In passing through the serpentine, 

 the vein, with a few exceptions, is transversely asbestiform, the fibres 

 being, as in chrysotile, unresolvable or indefinite, in consequence of their 

 complete juxtaposition : in some places the divisional lines are sepa- 

 rated ; and here and there they are extremely faint : in one part, for 

 a short distance, the vein is scarcely differentiated from the intersected 

 serpentine. Adjacent to the granules the vein becomes acicular ; the 

 aciculi being in general closely (c) juxtaposed, and in a few places dis- 

 tinctly separated (a, h). A few of the neighbouring granules have their 

 surface hispid with independent aciculi (d), undistinguishable from those 

 belonging to the vein. On entering the cavity, the vein, here asbesti- 



* See ante, p. 516. 



f "Quarterly Journal of Geological Society," vol. xxii., p. 226, foot note. 

 X " Quarterly Journal of Geological Society," vol. xxiii., p. 262. 



