Eurbank.] 



198 • [April 19, 



In a hasty examination of a specimen from Bolton, I at first 

 thought it contained no serpentine, but more careful observations 

 proved that the rock was filled with serpentine grains, so completely 

 bleached by exposure that they were not easily distinguished by the 

 eye. 



The question in regard to the particular manner in which these 

 limestones, with the associated minerals, were deposited, and the 

 cavities filled, is one of greac interest and importance in connection 

 with this subject. I do not, however, propose to enter into any ex- 

 tended discussion on this point. On this and other questions con- 

 nected with this investigation, I hope to hear from Prof. Perry of the 

 Museum of Comparative Zoology, who has made extensive observa- 

 tions on the crystalline limestones elsewhere, and who visited the 

 Chelmsford quarries with me last September. I remember distinctly 

 that on entering the first excavation at one of the quarries, he at 

 once pronounced the deposit " a true mineral vein." He had pre- 

 viously expressed a similar opinion derived from my description of 

 these quarries. It had not occurred to me to give them precisely 

 this designation, though I had, as indicated in this paper, become 

 convinced by my own previous studies that the limestones are not 

 true stratified rocks, but are deposits which have filled cavities 

 formed by the folding and faulting of the strata of gneiss. 



Some facts have been stated in this communication for which I 

 offer no theories in explanation. I do not claim a sufficient knowl- 

 edge of the structure of the foraminifera to found any argument upon 

 the microscopic appearances that I have observed, nor do I mean 

 now to enter into a discussion of the general question as to the true 

 character of the Eozoon Canadense, as described by Carpenter and 

 Dawson. I am unable, however, to reconcile the facts here stated, 

 with the theory that the forms in these rocks, which have been identi- 

 fied as belonging to the structure of Eozoon, are of organic origin. 



On the other hand, it appears to me not unreasonable to infer that 

 the so-called " tubuli" that are so abundant in these rocks are semi- 

 crystalline forms that Jiane been deposited with the serpentine and other 

 minerals on the walls of the cavities, by infiltration of waters charged 

 with mineral matters. 



Mr. Burbank was followed by Mr. W. H. Niles, who en- 

 dorsed the views which he presented. 



