532 



carbonate of lime. The distinctive peculiarity of this case, however, is 

 that the latter substance, which is structurally satin-spar, retains the 

 fibrous character of the chrysotile. 



Finally, pseudomorphism, in crystallized examples, leaves intact the 

 form of the crystals. It will be well to bear this point in mind, as 

 cases may exist in which the " definite shapes " retain their forms, and 

 yet consist of a substance different from what is common to the " canal 

 system." It will be time enough, however, to discuss such possible 

 cases when they are known to us ; but, so far, we see no reason why 

 the " definite shapes " may not occasionally become more or less carbo- 

 nated (as siliceous minerals often are), or be composed of a soluble 

 silicate, without losing their form ; and consequently in a condition to 

 yield as readily even to dilute acid as their matrix ("intermediate 

 skeleton"), especially if it consist of dolomite.* We, therefore, think 

 that the Madoc case, and others of the kind, presumed to "close the 

 discussion" against us, have been immaturely considered, and do not 

 at all justify the conclusion they have given rise to. 



Dr. Carpenter has asserted that we "do not attempt to offer any 

 feasible explanation of the fundamental fact of the regular alternation of 

 lamella? of calcareous and siliceous minerals."! We have not avoided 

 this point ; nor do we conceal our inability to explain it satisfactorily. 

 But, if Dr. Carpenter wishes to construe oar inability into evidence in 

 his favour, he is assuredly mistaken ; for a similar " alternation" is not 

 uncommon as a purely inorganic phenomenon. We have already 

 pointed out the interlamination of calcareous and siliceous minerals in 

 pargasitic and other rocks;}: and we now adduce a similar case, men- 

 tioned by Dr. Giimbel, occurring in the gneiss of Wunsiedel, in the 

 Fichtelgebirge, where "specimens" of this rock "exhibit sheets of 

 hornblende of from five to fifteen millimeters, separated by limestone 

 layers of from fifteen to twenty millimeters in thickness. "§ Such 

 examples strongly confirm us in our belief that the " fundamental fact," 

 however it may have been produced, is no more than a peculiar mineral 

 arrangement — most probably a superinduced phenomenon. || 



Dr. Carpenter declares, that he is " prepared to maintain the organic 

 origin of Eozoon on the broad basis of cumulative evidence afforded by 

 the combination, in every single mass, of an assemblage of features which 

 can only be separately paralleled elsewhere ; and in the repetition of this 



* A small piece of elseolite, and another of "intermediate skeleton," composed of dolo- 

 mite (which, it must be remembered, is difficultly soluble compared with calcite), were 

 placed in weak acid, such as we usually employ in "eozoonal" decalcifications : both 

 were dissolved. 



f " Proceedings of the Koyal Society," vol. xv., p. 506. 



% "Quarterly Journal of Geological Society," vol. xxii., p. 210. 



§ " Canadian Naturalist," December, 1866, p. 95. 



|| Alternating layers of brown limestone and dolomite, perpendicular to the beds 

 containing them, are common in a Permian rock near Sunderland, in Durham : they 

 might be taken for laminae of deposition (see " Quarterly Journal of Geological Society," 

 vol. xxii., p. 212. 



