282 Professors King and Rowney's 



extreme to the other, in this the most demonstrative example 

 we have yet met with, is without a break or interruption of 

 any kind. 



We have no doubt that Dr. Carpenter has often seen ex- 

 amples resembling the above ; but, considering that they are 

 called by him " pseudomorphs," considerable doubts may be 

 entertained of his being " perfectly acquainted with " them. 

 Be this as it may, he " freely admits their resemblance to cer- 

 tain forms of the acicular layer left after decalcification of the 

 nummuline layer." To us the resemblance is too close — of too 

 graduating a character to be dismissed in this manner. Dr. 

 Carpenter will have, therefore, still to repeat—" Professors 

 King and Rowney persist in likening them, notwithstanding 

 my repeated assertions that the two things are altogether dif- 

 ferent"*. 



So, proofs of the complete passage of the " true nummuline 

 wall " into chrysotile or fibrous serpentine, and exhibited in a 

 highly metamorphosed rock with a complex mineral composi- 

 tion, are to be set aside by mere assertions, based on nothing- 

 more than simulations, and made, too, by one who rightly 

 confesses that he is "not a mineralogist." 



It is quite unnecessary to bring forward any other cases 

 than those elsewhere made known f to show that the " num- 

 muline wall, in its typical condition, occurs in cracks or fissures 

 of the serpentine." It so happens that one of the cases re- 

 ferred to is seen in the section which has yielded the demon- 

 strations that have been described and figured. 



We have all along maintained that the " nummuline wall " 

 is an integral portion of the grains and other aggregations of 

 serpentine which it invests : hence, when a " constructed " 

 figure was continually being republished, and which, by repre- 

 senting the " wall " with two continuous bounding lines, made 

 it appear as a part independent of the skeleton, like the 

 chamber-roof of a Calcarina, we deemed ourselves called upon 

 to make known the objection we have to such representation. 



Specimens are abundant which show the surfaces of the 

 grains gradually changing into the " nummuline wall," and 

 consequently proving the latter to be, not an independent part, 

 but an acicular variety of the serpentine. The specimens last 

 under consideration are evidences in point ; and we give, under 

 fig. 5, a representation of another specimen to sustain more 



* The italicization is ours. 



t See Quarterly Journal Geol. Society, vol. xxii. pi. xiv. fig. 4, p. 196: 

 Proc. Royal Irish Acad. vol. x. pi. xliii. figs. 5, 6. 



