76 Intelligence and Miscellaneous Articles. 



line ; the difference depends on the size, shape, and continuity of 

 the quartz veins, though even the lodes seldom maintain their regu- 

 larity for more than a few score feet. The quartz often occurs in 

 very narrow veins intersecting one another to form what may he 

 called ' stockworks.' It is probably from these minute veins that 

 the alluvial gold is derived. In the Ranb mine numerous 'rich. 

 veinlets occur in a certain zone where the whole slate-rock is charged 

 with iron pyrites, probably auriferous. Many ' stockworks ' are 

 intimately associated with dykes or intrusions of a rock which may 

 be called trachyte-porphyry, and these igneous rocks are decomposed 

 where prominently associated with auriferous quartz. 



3. " The Pambula Gold-deposits." By P. D. Power, Esq., F.G.S. 



The Pambula Gold-field is situated in the parish of Yowaka, 

 County of xiuckland, in the South-eastern corner of New South Wales. 



The lodes are different from ordinary auriferous deposits, inas- 

 much as the material filling the ore-channels does not differ greatly 

 in appearance from the ' country ' rock, and is but slightly miner- 

 alized. The 'country' rock is ' pyrophyllite schist/ associated 

 with ' felspar-porphyry,' sometimes turning into l quartz -porphyry,' 

 the whole being tilted at a high angle. The bedding and cleavage- 

 planes appear to be coincident. The rock forms len tides both micro- 

 scopic and macroscopic. Some of the lodes are accompanied by a 

 quartz ' indicator ' which contains little or no gold in itself, the 

 precious metal being found in the shattered ' country ' rock of its foot- 

 wall. On the footwall-side this shattered zone gradually merges 

 into the ordinary ' country ' rock. The cause of the parallelism of 

 the auriferous lodes, the mountain-ranges, and the seacoast is dis- 

 cussed, and it is pointed out that the gold does not occur in large 

 grains, 



XI. Intelligence and Miscellaneous Articles. 



AN ELECTROLYTIC THEORY OF DIELECTRICS. 

 To the Editors of the Philosophical Magazine and Journal. 



GrEFTLEMEN, 



SINCE writing the paper on dielectrics which you published in 

 your last issue, it has occurred to me that the calculation of q 

 from tenacity and dielectric strength might be made directly, 

 instead of in terms of specific inductive capacity and Young's 

 modulus. Perhaps it may be well to point this out. 



Disruptive discharge occurs when the mechanical force on a 



T 



molecule is equal to - =Td 2 ; and as the force applied electrically is 



equal to q x dY ™*- , it follows that 

 ds 



^~~ds~ 

 From this q for glass = \ xlO -n — a number which is probably 



