1884.] 
The Extraction of Gold. 
419 
containing 225 apertures to the square inch. It is then 
giound up with mercury, and washed over a series of amal- 
gamated copper plates and flannel filters, by which the gold 
is supposed to be arrested. In reality ^ry much of it as 
we have seen, escapes. The powder of the^ock is far too 
coarse , many minute particles of gold— locked up so to 
spea , in the centre of these particles— escape the action of 
lt °g eth er. Much of the gold, too, amalgamated 
01 not, floats away on the surface of the water, and is lost 
tho?M Pr ° bably l * he first auth ority on the subject* 
ough he did not see his way to doing away with the use 
of gold from quart2 stone > caIls a 
tinn Urt f h ?£ by grlndln £ U P wit h the wet mass no small por- 
? f tbe mercury ls> rendered “sick,” as the technical 
teim is. In this state it is incapable of readily combining 
with metallic gold or silver, and floats away on the surface 
of the water in a fine film. This sickening or killing of the 
mercury is very much promoted if a little oil or grease from 
machinery finds its way into the amalgamation-pan. If 
anyone wishes to see what sick mercury is, he need only 
grind a little of this metal up in a mortar with water and 
fine sand or earth. If he continues this process long enough 
he will find that the metal loses its tendency to run together 
great° difffcu^ty^ )S, ^ ^ be colleaed together with 
The water also facilitates the aftion of sulphurets of anti- 
mony , &c., upon the quicksilver. Sometimes, indeed, where 
these ingredients are abundant, the whole, as the miners 
teim it, gets into “ a mess,” from which neither the gold 
terms 56 eXtradbed nor the mef cury recovered on paying 
In consequence of the deficient yield of many of the 
kinds of quartz rock, and the practical impossibility of 
woiking others at all, some of the mines in Queensland have 
been abandoned, and others are carried on at a profit far 
below what they ought to yield. At the same time the 
tailings or residues of ore which have been ground and 
submitted to the amalgamation process have accumulated 
to the extent of many thousands of tons. These tailing* 
still contain a very fair proportion of gold, as is proved bv 
the assay, but they cannot on the ordinary principle be re. 
worked at a profit. ^ 
In consequence of this annoying state of affairs Mr W 
Pritchard Morgan, a North Queensland mine-owner, ‘and 
Mr. J. Needham Longden, an Australian mining-engineer 
