Reviews — King and Eoumey on Eozoon Canadense. 235 



view of the case, since it is not difficult to suppose that certain 

 massive non-aluminous amphiboles and pyroxenes may have con- 

 tributed to form the purer serpentines as well as to produce the 

 ophicalcites, etc. Moreover, we may have a partial serpentinization 

 of an olivine dolerite ("greenstone"), such as that of Clicker Tor, 

 which yields very interesting specimens. 



Thus it may be fairly admitted that Ophites are polygenetic, and 

 that to a certain extent even serpentine is so, but we should be dis- 

 posed to draw the line for the present, so as to exclude the granites 

 and felsites, and to limit the process to the more basic class of rocks. 

 As regards the case of ophitic silicates in fissures, though the mag- 

 nesian constituent may be largely derived from the containing rocks 

 yet it might well happen in some cases that the sources are in a 

 great measure foreign ; and this may also be the case where rocks 

 have been very much fissured, as in the serpentinous limestones of 

 Connemara quoted by Harkness (p. 42). Furthermore, there can 

 be no doubt as to the general correctness of the authors' view that 

 some Ophites were sediments, whilst others were igneous rocks 

 originally, but it is probable that where any great development of 

 Ophite obtains, such rocks were originally rich in magnesia. 



The authors have paid considerable attention to the subject of 

 peridote in connexion with Ophites ; but if a statement, made at 

 p. 40, is to be taken as an example of their methods of reasoning, a 

 grave suspicion must attach to much of their work. 



It is well known that Zirkel, Bonney, and others, regard the 

 occurrence of pseudomorphs of serpentine after peridote and the 

 frequent association of the two minerals as evidence that Ophite, or 

 its essential component serpentine, has originated from peridote or 

 from " peridolytes." On this the authors observe that it would be just 

 as reasonable to assume that basalt, because it usually contains a large 

 proportion of peridote, was generated out of masses of this mineral. 

 In other words that, because the hydrous (ferro) magnesian silicate, 

 serpentine, is said to have originated from the anhydrous (ferro) 

 magnesian silicate, peridote, that this same peridote might equally 

 generate a complex mineral-aggregate like basalt, largely made up 

 of augite and triclinic felspars, and rich in alumina, lime, and soda 

 hi addition to the bases of peridote. Such are the results of indulg- 

 ing too freely in methylosis. 



A considerable portion of chapter xi. is devoted to proving that 

 peridote is largely a secondary product. From the position in whicli 

 that mineral has occasionally been found, as in veins of calcite 

 traversing talcose schist, this may sometimes be the case. Its 

 occurrence in the granular limestones (hemithrenes) is also quoted as 

 showing its secondary origin : but if the authors' view be correct, 

 as to the silicates in these limestones being merely the decreted 

 remnants of the original minerals replaced by carbonates, the 

 occurrence of peridote in these rocks can hardly be quoted in proof 

 of its secondary origin. 



Admitting, however, that peridote, like augite and other anhydrous 

 silicates, may sometimes be formed in the wet way, we must regard 



