O'Reilly — Notes on some Assays for Gold, etc. 451 



obtained the following results for the gold present in certain soils 



and ashes: — 



Vegetable Mould (terreaux), ... 0, 0000138 



Heather Soil (Terre de Bruyere) y . . 0, 0000195 



Beachwood Ashes, 0,0000195 



Vineshoot Ashes (sarments), ... 0, 0000325 



Garden Soil, 0, 0000390 



Manured Vegetable Soil, . . . 0,0001520 



As a distinct proof of this general dispersion may be cited the 

 fact of the existence of gold in sea- water, as ascertained by Sontag, 

 and estimated at 0, gr. 05 p. ton (Proceed. R. S. Lon., 1872) — a 

 much smaller quantity, no doubt, than the silver or copper present 

 in the ocean, but sufficiently distinct to be determinable chemically — 

 its presence being naturally accounted for by the salts carried in 

 solution by rivers — these receiving the products of the decomposi- 

 tion of strata containing gold in some one or other mineralized state. 

 It is further presumed that the gold is held in solution by the sea- 

 water in virtue of the chlorides, iodides, and bromides present. 



Taking it, therefore, as ascertained that gold is very generally 

 dispersed in rocks, and more particularly in the older rock forma- 

 tions, that dispersion may be either uniform or varied, so that 

 certain rocks and localities should show much more gold than 

 others. 



Thus, quartz has always been considered as the mother rock of 

 gold, and, as a consequence, the formations in which quartz veins 

 occur most markedly have generally been recognized as the richest 

 in that metal, with the result that the Cambrian and Silurian for- 

 mations have long been reputed the richest in gold-bearing reefs, 

 and the countries wherein these formations show themselves have 

 become the fields of exploration for that metal. 



The extraordinary development of gold mining, since the 

 Californian discovery of 1848, in every quarter of the world, and 

 the number of facts observed and recorded in connection with the 

 associations of gold, and as regards the encasing rocks and accom- 

 panying minerals, have considerably modified the views held in 

 this respect. Thus A. Gr. Lock, in " Gold : Its Occurrence and 

 Extraction," 1882 (p. v. Introduction), says: — "Recent geo- 

 logical explorations have shown that gold is abundantly present 

 in formations which it was authoritatively stated could never 



