178 



THE GEOLOGIST. 



ing to the ocean, together with the greater part of Western Port Bay 

 itself, must have been literally cut out by the continual influx and eflux of 

 the tidal wave. Some of the difficulty may be avoided by supposing a soft 

 strata undermined by the huge breakers of the Pacific, as previously 

 alluded to, but even then the time necessary for accomplishing the re- 

 quired result almost surpasses belief. Shingle in every stage of formation 

 from fine sand to angular boulders, huge landslips whose fall must as- 

 suredly have been of comparatively recent date, and rocky masses so under- 

 mined as to render their speedy crumbling into a mass of detritus a matter 

 of certainty, — all point to the same conclusion, that the disintegration of the 

 indurate material has been solely the result of aqueous agencies long con- 

 tinued. Still, both theory and fact alike declare the immensity of the 

 period required to bring about the changes witnessed. The colonist re- 

 members the shingly beach as ever shingle ; the mass of talus seems to have 

 undergone no visible change ; and the rocks, whose bases are undermined, 

 and whose stability thus seemingly destroyed, appeared just as near their 

 dissolution when some adventurous circumnavigator left his vessel in the 

 offing, and landed hereabout for the first time some century ago. 



PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



SCHOOL OF MIXES.— DK. PEECy's LECTT1EES ON CHEMICAL GEOLOGY. 



Lectube III., December 17, 1863. — At our last meeting attention was 

 especially directed to the subject of alumina, a base consisting of a metal 

 termed " aluminium " and of oxygen. It exists extensively diffused through 

 nature, and is the essential constituent of all clays, or, at all events, is an 

 essential constituent of all clays. It exists in nature beautifully crystal- 

 lized, and is then known as corundum. When coloured blue it is termed 

 sapphire, when red, ruby. Sometimes this corundum occurs opaque from 

 the presence of impurities, and then we have it in the form of common 

 emery. In the laboratory of the chemist, dried alumina is known simply 

 as a white amorphous powder, excessively insoluble and infusible. Having 

 described the physical and chemical properties of alumina, we proceeded 

 then to examine certain methods by which it can be obtained in a crystal- 

 line form. We will now pass on to consider further this part of our subject. 



In the first place, the lecturer claimed attention to a singular and beauti- 

 ful mineral " staurolite," which has been prepared artificially. A word by 

 way of caution. It does not follow that the methods by which we can pre- 

 pare mineral matters crystallized in the laboratory, should be precisely 

 those which nature herself has adopted on a great scale, though in many 

 eases there is no doubt that the processes employed are really identical 

 with those which nature herself has employed. Then, again, there is an- 

 other very important point to bear in mind. The same mineral substance 

 may be produced by methods entirely distinct. The well-known and beau- 

 tiful mineral termed "felspar" can be produced both by the agency of 

 liquids at a tolerably high temperature, and also directly by igneous fusion. 

 Specimens of magnificently crystallized felspar have been taken from fur- 

 naces, where there is no doubt about the mode of its production. And 

 now for this mineral, staurolite, which is a silicate of alumina. We are in- 

 debted to Deville for a singular experiment regarding the formation of this 



