design to a greater degree than it does the other
engineering specialists. The question of capital and profit dogs
his every footstep, for all mines are ephemeral; the life of any
given mine is short. Metal mines have indeed the shortest lives of
any. While some exceptional ones may produce through one generation,
under the stress of modern methods a much larger proportion extend
only over a decade or two. But of more pertinent force is the fact
that as the certain life of a metal mine can be positively known in
most cases but a short period beyond the actual time required to
exhaust the ore in sight, not even a decade of life to the enterprise
is available for the estimates of the mining engineer. Mining works
are of no value when the mine is exhausted; the capital invested
must be recovered in very short periods, and therefore all mining
works must be of the most temporary character that will answer.
The mining engineer cannot erect a works that will last as long as
possible; it is to last as long as the mine only, and, in laying
it out, forefront in his mind must be the question, Can its cost
be redeemed in the period of use of which I am certain it will
find employment? If not, will some cheaper device, which gives
less efficiency, do? The harbor engineer, the railway engineer,
the mechanical engineer, build as solidly as they can, for the
demand for the work will exist till after their materials are worn
out, however soundly they construct.

Our engineer cousins can, in a greater degree by study and
investigation, marshal in advance the factors with which they have
to deal. The mining engineer's works, on the other hand, depend at
all times on many elements which, from the nature of things, must
remain unknown. No mine is laid bare to study and resolve in advance.
We have to deal with conditions buried in the earth. Especially in
metal mines we cannot know, when our works are initiated, what
the size, mineralization, or surroundings of the ore-bodies will
be. We must plunge into them and learn,--and repent. Not only is
the useful life of our mining works indeterminate, but the very
character of them is uncertain in advance. All our works must be in
a way doubly tentative, for they are subject to constant alterations
as they proceed.

Not only does this apply to our initial plans, but to our daily
amendment of them as we proceed into the unknown. Mining engineering
is, therefore, never ended with the initial det