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Profs. W. King and T. H. Rowney. [June 19, 



examine the doctrine advocated by S terry Hunt; and contend that 

 it is altogether untenable, both from his own arguments, and a body of 

 unquestionable counter-evidence. Repudiating a doctrine which regards 

 the rocks in question as still being in their original or quasi-original 

 condition, formed at the bottom of a primaeval ocean, through the 

 chemical precipitation of substances which it held in solution, the 

 authors express themselves in accordance with the prevailing opinion 

 that they were originally ordinary argillaceous, arenaceous, and other 

 sediments, which, through being buried at great depths, have under- 

 gone various changes — some ending in their mineralisation and others 

 in their methylosis. S terry Hunt's doctrine is further contested by 

 evidences adduced of regional metamorphism pertaining to various 

 post-Archasan periods, whose crystalline or mineral effects are identical 

 with those which he restricts to pre- Cambrian ages, and which he pre- 

 sumes to have been produced by chemical precipitations from seas 

 of the time. 



The mineralised metamorphics having thus far principally engaged 

 their attention, the authors next touch upon the (F) " Methylosed 

 metamorphics — ophites." Taking, as their standpoint, the carefully 

 worked out conclusion of Blum, Bischof, Rose, and others, that ser- 

 pentine, as a mineral, is in all cases the product of pseudomorphism, 

 it is contended that rocks essentially made up of it, adding other 

 secondary minerals in certain kinds, have necessarily undergone 

 chemical changes. Cases are cited, such as the serpentinite of the 

 Lizard, which they were the first to show, from its containing pseudo- 

 morph crystals after augite, had been originally a porphyrinic dolerite. 

 One of the Cannover Isles, in Lough Corrib, contains a mass of ser- 

 pentine, which is shown to be a methylosed diorite or tremolitic rock. 



The evidences offered by Bischof, Heddle, and other writers, as 

 to the conversion of serpentinous and other siliceous rocks into 

 calcareous masses are adduced by the authors in confirmation of 

 their view respecting (G) " The methylotic origin of hemithrenes, &c." 

 Additional original evidences are brought forward with the same pur- 

 port. A volcanic or doleritic dyke intersects gneiss on Mr. Frederick 

 Twining's estate, adjacent to Cleggan Bay, Connemara ; where, not 

 only is the gneiss converted into hemithrene, consisting of malacolite, 

 peridote, serpentine, calcite, and other minerals, but the dyke itself 

 is charged with calcitic matter. Another case occurs at St. Philippe, 

 Yosges, where gneiss incloses dyke-like masses of hemithrene, as to 

 conclusively prove, in the opinion of the authors, that the latter are 

 chemically changed products of the former, effected by permeating 

 streams of heated water containing a carbonate in solution. The 

 labours of Delesso have shown that the region around abounds with 

 masses of the kind. 



The rocks described having undergone such remarkable changes, 



