Gold Mining Notes. 45 
miners sunk a few feet deeper, rich rock would have been 
met. The character of the rock or " wall " inclosing 
these lodes has much to do with the productiveness of 
the latter, and if their walls be, as it is termed, " uncon- 
genial," little or no gold is to be found. In some places, 
as in the Clogan Gold Mine in Merionethshire, the lodes 
are only productive when the walls are formed of igneous 
rocks and not so when they are of slate, &c. 
Quartz mining is carried on by breaking up the quartz 
reef by blasting and manual labour. The gold is 
extracted by crushing the rock into a fine mud or 
" pulp '•' by means of water and mercury under a power- 
ful stamping mill. The Reports do not contain a 
description of a Stamping Mill, but except that the 
process is or was conducted in California by means of 
hides or blankets over which the resulting mud or pulp 
flows, the machine does not materially differ from 
those in use in Australia. One of the best constructed 
was exhibited at work by Queensland in the Colonial 
and Indian Exhibition. An ancient writer, AGRICOLA, 
in his work De Re Metallica, published in 1621, gives 
figures of a stamping mill in all essentials the same as that 
now in use, and he also describes sluices, rockers, and 
pans similar to those of the present day. 
The mills now used are capable of crushing 40 to 70 tons 
a week. The quartz broken into small fragments by 
hand is fed into a hopper. The stampers are of solid 
wrought iron weighing from 600 to 800 lbs., and are raised 
and lowered about 9 inches some 80 times a minute. In the 
Australian machines these stampers work in a cast iron 
box of considerable depth to prevent splashing, and the 
muddy liquid flows through steel wire strainers 40 meshes 
