EUBIDGE — SOUTH-AEEIOAN EOCKS. 



53 



It is well known that prelmite is a common mineral in some parts 

 of this colony. It occurs in the dioritic or syenitic dykes of the 

 Dicynodon strata, and is evidently a product of the re-arrangement of 

 the minerals of these dykes during their decomposition. The prehn- 

 ite is found in laminss between the decomposing masses of the dykes 

 and on their faces as digitate concretions. IJnlike M. Daubree's 

 zeolites it has not required heat for its formation, but, like them, it 

 is forming at this hour by aqueous action. I have almost as little 

 doubt that dykes and other masses of granite are forming in the same 

 way from the re-arrangements of the constituent minerals of the 

 gneiss. I find it easier to feel the truth of this on the spot than to 

 convey it to others ; still I will endeavour to give some reason for 

 my faith. One mass of gneiss, near Henkrees, in which a vein of 

 granite, terminated by an expansion about a foot square, proceeded 

 along the gneiss. It was quite evident that there was no intrusion, 

 no connection with any mass below. Spindle-shaped masses of 

 granite placed between beds of felspathic, micaceous, and other rocks, 

 were numerous and could often be entirely removed by a hammer, 

 showing they had no connexion with any subterranean mass. 

 Spherical lumps of granite or syenite were frequently quite isolated 

 in the schists of the mines. I have stated before that beds of quartz- 

 ite appeared to be intercalated by a filtration from above ; some of 

 these could be traced down till they became mixed with mica and 

 then with felspar, and not very much deeper assumed the character 

 of the gneiss of the country. Other masses, which seemed to be in- 

 termediate between these, toward the spindle-shaped granite lumps 

 above, were composed principally of quartz, with a few grains of mica 

 and felspar, and occasionally garnets : these were surrounded by mica- 

 schist in hent-up strata ; yet the whole mass, perhaps twenty pounds 

 or less in weight, could be removed. These circumstances seemed 

 to me to prove clearly that if felspathic rocks of any kind are the 

 products of metamorphic action, then are granite, syenite, etc., trace- 

 able to a like origin ; that if, as I think, I have clear evidence, in the 

 Maitland Mines and other places of this neighbourhood, palaeozoic 

 rocks are convertible into micaceous, chloritic, and felspathic schists, 

 without evidence of eruptive agencies, then are the so-called igneous 

 rocks equally so. I think it will scarcely be disputed by any who 

 admit the re- arrangement of felspathic rocks I have contended for, 

 that causes by which such re-arrangement was made, may have 

 effected the original conversion of sedimentary into crystalline rocks. 

 We have in this province a rock which has been pronounced decidedly 

 igneous by the highest European authorities ; it is the claystone- 

 porphyry of Bain. Yet its position among the other rocks is, in 

 many respects, just that of the quartzite ; and, like the latter rock, 

 its individual beds and its minor masses are conformable with the 

 stratified rocks, while in ranges many miles in length, it crosses the 

 strike of the strata, generally at an angle of about 30°. This fact 

 was first demonstrated to me by Mr. Pinchin, a gentleman who has 

 made many interesting observations on the geology of this country. 



