1872.] 



DAINTREE GEOLOGY OF QIJEEN-SLAND. 



29< 



diggings," by Mr, Richard Smith, of the School of Mines, Jermyn 

 Street, made with the sanction and assistance of Dr. Percy (to whom 



Fig. 15. — View slioivlng the Intrusive Dylce of Diorite, with the 

 Quartz-vein at the point of intersection with the Devonian Rods, 

 at the Junction of Gilbert and Robertson Rivers. 



I am indebted for the use of laboratory and reagents to complete 

 the other analyses given in this paper), gave : — 



Gold 89-920 



Silver 9-688 



Copper 0-128 



Lead 0-026 



Bismuth none. 



Iron 0-070 



99-832 



In considering the mode in which the gold was introduced into 

 these veins, this constant association of silver is the chief difficulty 

 to contend with. It is evident that the solvent and precipitant must 

 have been able to perform their functions on each simultaneously. 

 All experiments based on the precipitation of gold alone from its 

 solutions afford no clue to the action which has taken place in nature, 

 where the gold, silver, and other alloyed metals are entirely homo- 

 geneous. 



No case has yet been established in our museums where the gold 

 and silver are separated in the same specimen, as is seen in speci- 

 mens of native copper and silver from Lake Superior. 



In several reefing-districts in Queenslandj however, we have con- 



VOL. XXVIII. PAKT I. r 



