20 Victoria as a Field for Geologists. 



■ Here again are respective sections of Steiglitz, Sand- 

 hurst, and Ballarat. The purple tints also represent 

 the Silurian rocks. The blue branching lines, crossing the 

 strata, are the same quartz veins as viev^ed in section. A 

 little attention will lead one to conclude that these veins are 

 simply fissures, subsequently filled up, and, as I imagine, that 

 the filling up has taken place from below, and not from 

 above. The Huttonian school, of which Mr. Eosales appears 

 to be a disciple, refer the filling up to masses of heated and 

 molten quartz, just as, on a small scale, flaid metal runs into 

 the interstices of a mould, or, on a larger one, trap dykes are 

 formed in the fissures of modern volcanoes. 



Mr. Da^dson, i^eferiing to the origin of gold-bearing veins, 

 supposes that the quartz and tlie gold were together forced 

 up from beneath, whilst both were in a liquid state, by some 

 powerfully eruptive force. So long as the quartz continued 

 to flow upwards it might reasonably be expected to hold the 

 contained gold in a state of suspension, but when the force 

 below, and with it the upward motion, ceased, the heavier 

 substance, that is, the gold, would naturally sink downwards 

 by virtue of its superior gra.vity. Some portion of the 

 mixture would be forced completely outside the fissure, and 

 the gold contained therein, the quartz being subsequently 

 disintegrated, would give rise to the rich gutters and nuggets 

 peculiar to what are known as the deeper leads. The top 

 portion of the vein would cool rapidly by contact with the 

 atmosphere, and the fluid thickening, must necessarily en- 

 tangle much of the gold, thus preventing its sinking down- 

 wards, just as rapidly as cooling wax retains in suspension 

 shots which othei'wise would sink speedily to the bottom. 

 This portion of the vein being in time broken up, would 

 foiTH gold diift No. 2, generally of gTeat riclmess, but inferior 

 in productiveness to the one below. Then in time the 

 lower, and, consequently, the poorer part of the vein, would 

 be worn down, gi^ang rise to the upper diift, still poorer, 

 but apparently more productive of larger nuggets than any 

 portions of the reef now remaining in situ. 



This is a somewhat ingenious theory. It accounts for 

 the presence of the gold, and for the supposititious phenomenon 

 that the same becomes less plentiful as we descend. It ex- 

 plains, too, the schlicken or scratched sides found on many 

 reefs, for if the reefs were thus once heated, they must 

 necessarily contract greatly after their formation, and so 

 contracting, would grate against tlie adjacent rock ; hence the 



