ult of vigorous development is to increase the ore in
sight,--the visible life of the mine. When such visible life has
been so lengthened that the period in which the "saving of fixed
charges" will equal the amount involved in expansion of equipment,
then from the standpoint of this limitation only is the added
installation justified. The equipment if expanded on this practice
will grow upon the heels of rapid development until the maximum
production from the mine is reached, and a kind of equilibrium
establishes itself.

Conversely, this argument leads to the conclusion that, regardless
of other considerations, an equipment, and therefore output, should
not be expanded beyond the redemption by way of "saving from fixed
charges" of the visible or certain life of the mine. In those mines,
such as at the Witwatersrand, where there is a fairly sound assurance
of definite life, it is possible to calculate at once the size of
plant which by saving of "fixed charges" will be eventually the
most economical, but even here the other limitations step in to
vitiate such policy of management,--chiefly the limitation through
security of investment.

LIFE OF THE MINE.--If carried to its logical extreme, the above
program means a most rapid exhaustion of the mine. The maximum output
will depend eventually upon the rapidity with which development
work may be extended. As levels and other subsidiary development
openings can be prepared in inclined deposits much more quickly
than the shaft can be sunk, the critical point is the shaft-sinking.
As a shaft may by exertion be deepened at least 400 feet a year on
a going mine, the provision of an equipment to eat up the ore-body
at this rate of sinking means very early exhaustion indeed. In
fact, had such a theory of production been put into practice by
our forefathers, the mining profession might find difficulty in
obtaining employment to-day. Such rapid exhaustion would mean a
depletion of the mineral resources of the state at a pace which
would be alarming.

MECHANICAL INEFFICIENCY OF PATCHWORK PLANT.--Mine equipments on
speculative mines (the vast majority) are often enough patchwork,
for they usually grow from small beginnings; but any scheme of
expansion based upon the above doctrine would need to be modified
to the extent that additions could be in units large in ratio to
previous installations, or their patchwork character would be still
further accentuated. It would be impossibl