g as necessary to give the amount
of water desired. Nobody wants less than ten or twelve inches for
mining: a "sluice-head" is about eighteen inches; a "hydraulic-head" is
from forty to two hundred inches. The water, however, is not measured
accurately. Of course the amount which runs through the orifice will
depend to a considerable extent upon the "head," which is usually
greater in the morning than at night. At sunrise there may be fifteen
inches head, and at sunset only three. The water collects during the
night, and is exhausted during the day. The price of water is in no
place less than ten cents an inch per day; in some places it is forty
cents; the average is about twenty cents.

Many of these ditches are extensive enterprises, and have cost hundreds
of thousands of dollars. When they cross ravines and valleys, large
flumes--wonders of carpentry--must be built. Some of these are two
hundred feet high and a mile long, and so large that a horse and waggon
can be driven through them. In all, save length and durability, they
are as wonderful as the great Roman aqueducts, whose tall ruins still
stand in the Campagna, near the Eternal City. In some cases iron tubes
have been used, and although they are very expensive, yet they may pay
for themselves, by preventing evaporation, leaking and soaking, which
take away much of the water from flumes and ditches.

_Prospecting._--"Prospecting" is the search for gold. The instruments
used by the prospector for placer-mines are usually the pan, pick and
shovel. He should be familiar with the general laws of the distribution
of gold, and then try the dirt in the most favorable places. If there
is any gold in a district, he can scarcely fail to find specks of it by
washing dirt from the bed-rock in the ravines, and in bars. The
existence of gold in a district having been established, close
observation will suggest to the prospector where he may reasonably
expect to find the best diggings. It is usually found that placer-gold
is collected in those places where, if he had been familiar with the
ancient topography of the country, he should have had reason to suppose
that it would be.

_Quartz Mining._--Quartz mining differs much from placer mining. For
the former, more capital, more experience, more complicated machinery
and richer material are required than for the latter. The placer miner
throws the dirt into the water, which then does the work; whereas the
pulverizing of rock