Notes on the Area of Intrusive Rocks at Dargo. 161 



It remains now for me to point out a possible source of 

 the gold contained in the reefs. It might be considered that 

 the gold and silver found in the contact reefs had an origin 

 connected with the plutonic masses, but this explanation 

 would not apply to those reefs and veins which are to be 

 found in the Silurian rocks spoken of by me previously. 



Sonstadt* has proved the existence of gold in sea water, 

 and, according to Wurtz,*f" it is therein at the rate of one 

 dollar in value to every twenty-five tons of water. Such 

 being the case, it seems probable that the waters of the 

 Paleozoic oceans did not contain less gold in solution than 

 those of the present time. The deposition of the enormous 

 thickness of Silurian sediments,! much of which consisted 

 of fine silt and mud containing organic substances, must 

 have necessarily included a certain amount of sea water. 

 This, although as to some of the elements and combinations 

 — as, for instance, gold — a solution of extreme dilution, yet 

 would, in the ao-oreo^ate, contain an enormous amount even 

 of the rarer elements. Hence these sediments must, on this 

 view, have included a large amount of sfold diffused throuo^h 

 them in solution, possibly, as at the present time, in com- 

 bination with iodine. 



The observations and experiments of Daintree, as con- 

 firmed by Wilkinson,^ show that the solution of gold 

 chloride is precipitated in the presence of organic substances. 

 The occurrence of auriferous pyrites deposited upon a piece 

 of wood taken from the drift immediately below the basalt 

 at Ballarat|| and of gold deposited upon coal at Voros- 

 pataklF still further illustrates this reaction, and, as relates 

 to the former instance, it shows that even in recent times- 

 subterranean waters conveyed gold in solution. That they 



* Roth — Chemische Geologic, Vol. I., p. 492. 



t Hunt— Chemical and Geological Essays, p. 237. 



j " Making due allowance for this repetition of the same beds at the' 

 surface, the total vertical thickness of the series can scarcely be estimated 

 at less than 35,000 feet." Intercolonial Exhibition Essr.ys, 1866. " Notes on 

 the Physical Geography, Geology, and Mineralogy of Victoria," by Alfred E. 

 C. Selwyn and George H. F. Ulrich, p. 11. 



§ Mr. Daintree' s discovery consisted in the fact that a speck of gold 

 lying in a solution of chloride of gold increased to several times its original 

 size after a small piece of cork had, by accident, fallen into the solution. 

 This was confirmed by further experiment by Mr. Chas. Wilkinson. Ibid^ 

 p. 24, 



II Ibid, p. 56. The pyrites gave a yield, on assay, at the rate of 

 40 ozs. of gold per ton. 



11 Recorded by K. V. Fritch. Eoth— Chemische Geologic, Vol. I., p. 602.. 



M 



