Norman Taylor — The Cadgccjong Diamond Field. 409 



greenstone (diorite), which, originally acted as a barrier to the old 

 river, and diverted its course, in an elliptical curve, round " the 

 flat." Subsequently to the formation or deposition of the drift, a 

 lava stream flowed down the river valley, completely filling its bed, 

 and covering the drift ; a new river had then to cut its way, during 

 which process the denudation must have been very great, as nearly 

 all the basaltic lava, and the underlying drift, had been swept away, 

 and partially re-deposited, forming the next older drift. This drift 

 is at a much lower level than the older drift, but still above the 

 present river. The total length of the leads round the flat is 

 about four miles. The older lead is only in situ under the basalt 

 outliers ; and, between and outside these, the lead is newer. The 

 drift only underlies the basalt on the eastern side of the basalt hills 

 on the west side of the flat, and on the western side of those on 

 the eastern side of the flat. 



The drift underlying these outliers was only worked for gold on 

 the bottom, and the diamond vein may still remain overhead, as 

 diamonds were found in the tailings, and also in the " spoil heaps " 

 . at the mouths of the shafts. On the west side of the flat, the 

 newer drift is divided, at a depth of about 43 feet, by a high slate bar, 

 the depth on the west side of which is 58 feet, and on the east from 

 66 to 75 feet ; further south it is 40 feet on the bar, from 28 to 34 

 feet on the west side, and from 70 to 80 feet on the east side. This 

 bar consists of white and grey arenaceous shales, and white mud- 

 stones, and runs in the usual strike. The newer drifts are 

 characterized by a flesh-coloured or reddish quartz gravel, which 

 appears to be derived from the Carboniferous conglomerates ; and 

 also by " floating reef," consisting of grey, brown or yellow, coarse 

 and fine siliceous and felspathic grits, in flat oval-shaped boulders, 

 occasionally containing Upper Silurian fossils, olive shales, and 

 fine, flaky, soft white sand rock. The " deep lead " seems to be 

 peculiar to the " flat," and is a series of rather sharp undulations, 

 with occasional flat and sometimes pot-holed spaces. The lead has 

 been very imperfectly traced, for the miners have sunk their shafts 

 in straight lines from one basalt hill to the next, in a way it would 

 be extremely unlikely a river would flow. The bottom of the older 

 lead is from 30 to 40 feet above the present river-bed level ; and, at 

 a short distance from the river at both ends, the lead has been com- 

 pletely washed away by the river in cutting down to its present 

 level. The contents of these "leads," as would naturally be ex- 

 pected, are very different ; the older being destitute of local rocks, 

 whilst the newer contains remains of the latter, and of the basalt 

 which caps the older. The basalt is very dense, hard, and black in 

 its upper part, and sometimes incloses grains of olivine ; below, it is 

 mostly decomposed, and of a light slate colour, with veins of a 

 white aluminous silicate. It decomposes very rapidly in concretions 

 when exposed to the air. The upper part affords numerous good 

 examples of columnar structure, occurring in long vertical hexagonal 

 prisms from a foot to eighteen inches in diameter. In the joints 

 between the columns, and other horizontal joints, a peculiar green 



