392 Professors King and Rowney on 



mens out of apparently a most unpromising rock (serpen- 

 tinite, rarely including any carbacid members), showing its 

 characteristic mineral not only changing as " eozoon " into 

 calcite, but also as a pseudomorph after augite, &c. A de- 

 scription of these cases is in preparation for publication. 



Our view is that the changes referred to have resulted from 

 the action of heated water holding a carbonate in solution. 



But to return to '•'•Eozoon.'''' Dr. Carpenter has kindly 

 offered " to give time and trouble to enable those who wish to 

 make the comparison of actual specimens for themselves." We 

 would strongly urge on them to take advantage of this offer. 

 We may be permitted, however, to supplement it by suggesting 

 their careful perusal of the memoirs that have been published 

 by us descrij)tive of similar specimens*, not forgetting those 

 published by Dr. Carpenter and others on his side. 



Attention may next be called to the following summary of 

 the arguments and evidences contained in the memoirs re- 

 ferred to : — 



1st. The serpentine in ophitic rocks (consisting essentially 

 of serpentine and calcite, with which various other minerals, 

 chiefly silacids and carbacids, are often associated) we have 

 shown to present appearances which can only be explained on 

 the view that it has undergone structural and chemical (me- 

 thylotic) changes : — the former causing it to pass into different 

 subdivided states ; and the latter etching out the resulting 

 solids into a variety of forms — grains and plates with lobu- 

 lated or segmented smfaces (" chamber-casts," see Dr. Car- 

 penter's fig. 1), fibres and aciculae (" nummuline chamber- 

 wall"), simple and branching configurations (" canal-system"). 

 Crystals of malacolite and other silacid minerals (often occurring 

 in ophite and other silo-carbacid rocks) manifest some of these 

 changes in a remarkable degree. 



2nd. The "intermediate skeleton" of ^^ Eozoon'''' (which 

 often appears as the calcitic matrix of the above lobulated 

 grains &c.t) is completely paralleled in various crystalline rocks, 

 notably marble containing grains of coccolite (Aker and Tyi-ee), 

 pargasite (Finland), chondrodite (New Jersey), &c. 



3rd. The " chamber-casts " in the granular (acervuline) 

 variety of ^'■Eozoon " are more or less paralleled by the grains 

 of the silacid minerals in the precited marbles. 



* Quarterly Journal of the Geological Society, vol. xxii. ; ' Proceed- 

 ings of the Royal Irish Academy,' vol. x. ; ibid, new series, vol. i. ; 

 ' Geological Magazine,' January 1873. 



t This part is dissolved out (artificially) in fig. 1. Dr. Carpenter's 

 fig. 2, exhibiting the various eozoonal features, must be taken merely as 

 an illustration, it being a constructed representation. 



