132 
Geology and Physical Geography: 
CHAPTER XIV. 
Suggestions for further development of Gold Mining — quartz 
and alluvial . General principles . Auriferous zones , or 
belts, described according to geographical position from 
rcest to east . Metals other than Gold . 
In indicating the directions in which mining exploration in 
search of auriferous gravels and quartz reefs appears most likely 
to prove successful, two circumstances, already pointed out, have 
to be kept iu view, as forming a basis on which to arrive at a 
reliable conjecture as to the probable auriferous character of any 
particular locality. 
The first is the known occurrence of auriferous quartz reefs 
whether in Silurian rocks, or in dykes traversing the same — in 
belts or strips of varying width, but of undefined longitudinal 
extent. The second is the strong indication afforded by the 
presence of any considerable quantity of gold iu alluviums, as to 
the close proximity of auriferous quartz reefs ; and conversely, 
the likelihood, or indeed certainty, of finding alluvial gold in 
detrital deposits, derived from and in the vicinity of rocks con- 
taining auriferous quartz-veins. 
The principal belts containing auriferous quartz reefs are now 
tolerably well known so far as the country consists of exposed 
Silurian rocks, and, in some places, the quartz reefs are being 
worked on their extensions beneath alluvial deposits and volcanic 
layers. Between these belts occur tracts of country which, though 
consisting of Silurian rocks traversed by quartz reefs, have, in 
spite of careful prospecting, failed to yield gold in remunerative 
quantity, though, no doubt, there may be in such apparently uon- 
auriferous tracts minor belts or lines of auriferous quartz reef 
which have hitherto escaped observation. The lateral limits of 
the proved portions of the auriferous zones are, however, sufficiently 
well defined, and their lines of strike sufficiently well marked to 
furnish data for guidance in prospecting on the northward or 
southward longitudinal extension of such zones. That these 
zones do not maintain their auriferous character throughout their 
entire lengths is evident ; but it would appear that ou their Hues 
of strike the quartz reefs within their limits are auriferous for* 
various lengths, increasing in richness in one locality and dimin- 
ishing in another. In fact, as a single line of quartz reef is 
generally found to contain gold in successive shoots, separated by 
barren intervals, so do the belts comprising each a number of 
quartz reefs exhibit the same phenomenon. So long as the country 
