efully measured; and the direction of the lost
lode is taken to be that which shows the least resistance in
proportion to the distance traversed. The work of carrying out such an
investigation must of necessity be somewhat elaborate, because it may
be necessary to connect in turn each shaft, as a centre, with every
one of the others as subsidiaries. But the guidance afforded even of a
negative character, resulting in the avoidance of useless cutting and
blasting through heavy country, will prove invaluable.

Many matters will require attention, in following out such a line of
practical investigation, which are to some extent foreign to the usual
work of the mining engineer. For example, the conditions which
determine the "short-circuiting" of an earth-current require to be
carefully noted, because it would be fallacious to reason that because
the line of least resistance lay in a certain direction, therefore an
almost continuous lode would be found. Moreover, the electrical method
must only be relied upon as a guide when carefully checked by other
considerations. Other kinds of moist formations, both metalliferous
and non-metalliferous, may influence the lines of least electrical
resistance, besides those containing the particular metal which is
being sought for.

The water difficulty has enforced the abandonment of very many
valuable mines in which the positions of the lodes are still well
known. Sunken riches lying beneath the sea in old Spanish galleons
have excited the cupidity and the ingenuity of speculators and
engineers; but the total amount of wealth thus hidden away from view
is a mere insignificant fraction of the value of the rich
metalliferous lodes which lie below the water level in flooded mines.

The point in depth at which the accumulation of the water renders
further following of the lode impracticable may vary in different
countries. In China, throughout whole provinces, there is hardly a
mine to be found in which the efforts of the miners have not been
absolutely paralyzed directly the water-level was reached. But in
Western lands, as well as in South Africa and Australia, the immense
capacity of the pumps employed for keeping down the water has enabled
comparatively wet ground to be worked to a very considerable depth.

The limit, nevertheless, has been reached in many rich mining
districts. Pumps of the most approved type, and driven by the largest
and most economical steam-engines, have done t