220 Notices respecting Neio Boohs. 



minds as to what is meant by the word serpentine. For this there 

 is, no doubt, excuse in the fact that few names have been used more 

 vaguely : the unfortunate accident that the same name has been 

 applied to a mineral and a rock (an accident which the authors 

 themselves attempt to remedy in the case of dolomite, and should 

 in very consistency have done in this also) has tended much to cause 

 this confusion. It has been augmented by the general neglect of 

 petrology by English geologists ; we had almost written the con- 

 tempt, all but expressed for it, by not a few of the more eminent 

 among them. It has been further augmented by the fact that rocks 

 which chemically, mineralogically, and sometimes petrologically, 

 widely differ from true serpentines, to the unaided eye resemble the 

 latter ; so that a rock which is only serpentinous may often, at 

 first sight, be mistaken for a serpentine, — this being a rock consist- 

 ing chemically of about 39 per cent, of silica, 36 per cent, of mag- 

 nesia, with probably about 12 per cent, of water, and 7 per cent, of 

 iron oxides, and rather variable quantities (usually not exceeding, and, 

 except in the case of the first, almost always less than 2 per cent.) 

 of alumina, lime, nickel, &c. — a rock, in short, which, chemically, 

 lithologically, and petrologically may be represented by the serpen- 

 tine of the Lizard. There being then such a type in not a few regions, 

 a nomenclature which neglects it, and a classification like the above, 

 appear to us as objectionable and as fatal to all progress in petro- 

 logy as it would be to put a basalt with a clay slate, because 

 examples might be found containing about the same proportion of 

 alumina : indeed we are much perplexed at not finding the former 

 rock inserted in the above classification, seeing that it certainly 

 contains a considerable percentage of magnesia. 



An instance of the confusion which the above hazy definition of 

 ophites has caused in the minds of the authors themselves (or pos- 

 sibly a proof of their inability to view a question judicially) may 

 be found in their introduction (p. xliv), where they state they are 

 unable to understand how a writer can " believe in the organic 

 nature of Eozoon " and yet assert " that he has never seen a ser- 

 pentine which was not intrusive." To this they append the remark, 

 it " is a puzzle to us, as it must be to Eozoonists, considering that 

 their doctrine is based on the sedimentary or aqueous deposition of 

 eozoonal serpentines. But is not eozoonism full of inconsistencies ? " 

 Any careful reader will see at a glance that the guarded statement 

 in the last clause is not equivalent to saying " there is no serpen- 

 tine which is not intrusive." The context also of the letter quoted, 

 and every paper which we can remember published by the author 

 cited, always uses the term serpentine in the strict sense mentioned 

 above. Further, there is no more inconsistency in believing that 

 serpentine (mineral) may occur sometimes in a rock of igneous, 

 sometimes of "aqueous" origin (assuming that the mineral in the 

 eozoonal " ophicalcites " is serpentine) than hi stating that quartz- 

 crystals are found both in trachytes and in the interior of organisms 

 in Cretaceous deposits. Indeed, if we remember aright, the above 

 author has been at some pains to show that, even in the true ser- 



