Victoria as a Field for Geologists. 21 



longitudinal stri83 now characterising their casings ; whilst 

 the whole is strictly in accordance with the Huttonian 

 hypothesis. The pity is that there are a few facts telling 

 much more against the theory than in its favour, as, for 

 example, close adjacent to the veins themselves — I quote 

 Mr. Selwyn's speech before the Mining Institute, reported in 

 the Mining Journal — are found delicate fossils still un- 

 changed in any way ; a proof, it would appear, that the 

 strata have never been subjected to the intense degree of 

 heat supposed. Then, again, there are branching veins so 

 thin that they never could by any possibility have been filled 

 in as molten material, since such material cooling would have 

 solidified and choked up the passage, as a long thin mould 

 will cool and choke up during a casting. But, lastly, it is 

 urged ty Bischof, that the rocks which the veins traverse 

 are often composed of materials, allumina and lime, which 

 readily form a mixture with the silica, more easily melted 

 than is either silica, lime, or allumina by itself. 



" If," s^js that writer, " we pour molten silver into a 

 mould of lead, part of the lead will be fused and form an 

 amalgam with the silver, so we may expect that, if formed as 

 supposed, by igneous agency, instead of pure quartz veins, 

 there will be found veins composed of quartz in a state of 

 mixture with more or less of the materials of the rock 

 through which they pass." 



Setting on one side the igneous theory, it is most natural 

 to refer the phenomena to the action of water. 



If, however, quartz is difficult to fuse, it is still more 

 difficult to solve. Nevertheless, although this is the case 

 with the pure material, the same, mixed with proper fluxes, 

 is easily reduceable. Together with potass or soda it forms 

 glass, a by no means refractory substance. Whilst, by in- 

 creasing the proportion of alkali, we actually obtain a sub- 

 stance not only readily fusible, but capable of being dissolved 

 and held in solution by either hot or cold water. It is, in 

 fact, the water glass, well known in the laborator}', and 

 lately brought into notice fi'om its supposed quality of harden- 

 ing and preserving otherwise friable sandstone. 



Some few difficulties, too, of the aqueous theory have 

 lately been explained away by a tolerably weU-known 

 process, alluded to by Dr. Percy, in his late course of lectures 

 on Chemical Geology. 



If to an aqueous solution of water glass, which may be 

 perfectly clear, we add, in a certain manner, an acid, the 



