unity to profit by it. The usual form is an option to buy the
property after a period which permits a certain amount of development
work by the purchaser before final decision as to purchase.

Aside from young mines such enterprises often arise from the possibility
of lateral extension of the ore-deposit outside the boundaries of
the property of original discovery (Fig. 3), in which cases there
is often no visible ore within the property under consideration
upon which to found opinion. In regions where vertical side lines
obtain, there is always the possibility of a "deep level" in inclined
deposits. Therefore the ground surrounding known deposits has a
certain speculative value, upon which engineers are often called to
pass judgment. Except in such unusual occurrences as South African
bankets, or Lake Superior coppers, prospecting for deep level of
extension is also a highly speculative phase of mining.

The whole basis of opinion in both classes of ventures must be
the few geological weights,--the geology of the property and the
district, the development of surrounding mines, etc. In any event,
there is a very great percentage of risk, and the profit to be gained
by success must be, proportionally to the expenditure involved,
very large. It is no case for calculating amortization and other
refinements. It is one where several hundreds or thousands of per
cent hoped for on the investment is the only justification.

OPINIONS AND VALUATIONS UPON SECOND-HAND DATA.

Some one may come forward and deprecate the bare suggestion of an
engineer's offering an opinion when he cannot have proper first-hand
data. But in these days we have to deal with conditions as well as
theories of professional ethics. The growing ownership of mines
by companies, that is by corporations composed of many individuals,
and with their stocks often dealt in on the public exchanges, has
resulted in holders whose interest is not large enough to warrant
their undertaking the cost of exhaustive examinations. The system
has produced an increasing class of mining speculators and investors
who are finding and supplying the enormous sums required to work
our mines,--sums beyond the reach of the old-class single-handed
mining men. Every year the mining investors of the new order are
coming more and more to the engineer for advice, and they should
be encouraged, because such counsel can be given within limits,
and these limits tend to place the industry up