THE FORMATION OF QUARTZ REEFS.

Tuapeka Times, Volume XVIII, Issue 1174, 26 August 1885, Page 4

THE FORMATION OF QUARTZ REEFS.

By Dr J. E. Taylor, F.G.S., F.L.S., &c, in the "Australasian." The Silurian rocks underlying the city of Melbourne tell a wonderful story to the geologist. Like the rest of the strata of thia well-marked formation all the world over (except, perhaps, in Sweden and Baltic Russia, where they are horizontal or nearly so), the rocks have undergone great mechanical and mineralogical changes. Once the soft layers were composed of fine mud, and were horizontal ; but they have since been laterally , squeezed into the curved and crumpled, and foliated appearance they are now seen presenting whenever a section of them is visible. They have been cracked through again and again since they were upheaved from the old sea-floor where they were deposited and converted into, dry land. From dry land they have been crumpled up into hills and perhaps mountains. Possibly they have been buried beneath thousands of feet of overlying sedimentary rocks, all of which have been peeled off by denudation. The Silurian rocks bear all the evidences of repeated terrestrial changes. The quartz veins which intersect them, and which elsewhere are the source (if not the origin) of gold, could only have been formed under some of the above-mentioned conditions, for quartz veins are due to hydrothermal action —to the action, that is to say, of superheated steam, charged with silica, after the manner with which such highly heated water rises in the Geysers of Iceland and elsewhere, and brings up silica along with it, If these cracked, and " faulted," and jointed Silurian rocka of Australia were ' buried beneath overlying strata (as I believe many of them have been), they would be brought within the influence of the earth's interior heat ; and silica in the shape of quartz would be deposited in them until every crack and fissure was filled up, and then ,the rocks would be intersected by these ribs or "reefs" of quartz rock

" I'm down' upon you !" as the incipient'moustache remarked-to the boy's i upper lip. .Mr "re, 1