Mining is "being carried on at steadily increasing
depths, and as mines go deeper, ventilation presents
problems of increasing complexity and importance. The
working of mineral deposits at moderate depths has led to
the sinking of numerous shafts, each serving for the
winning of the minerals from a small area, B\zt with
greater depths, the heavy cost of sinking and fitting
shafts has made larger mineral concessions a hecessity;
and with modem progress in the construction of roadways
supported by circular steel girders and brick or cement
linings, it is becoming evident that in the future still
more extensive concessions ?/ill be worked from a single
pair of shafts. Money which in the past has been spent
in sinking new shafts and erecting extensive surface works
will be found to be more economically expended in making
larger roadways with permanent linings, which will not
only serve for the winning of the minerals from an area
much more extensive, but will also lead to increased
safety and economy, especially by reducing the accident
rate and the cost of haulage below their present day values.The Science of Mine Ventilation is faced with
the problem of ventilating these extended areas in an
effective manner, and of securing, if possible, that there
shall not be set an effective limit to the size of the
area of economical exploitation by a failure to supply an
adequate volume of air. This problem divides itself
into a mining problem which has to do with the provision
and maintenance of suitable shafts and airways, and an
engineering problem which has to do with the provision
of suitable ventilating appliances for the production of
the necessary currents of air.The solution of the mining problem is found in
the provision of large airways in parallel arrangement
with each other, well secured by strong linings, as
smooth as possible to prevent excessive friction and as
tight as possible to prevent serious leakage of air from
the intake to the return. The power required to circulate
the necessary volume of air will depend upon how well this
mining problem has been solved. Large roadways not only
increase the facilities for safe and efficient transport,
but also reduce very considerably the bill for power
required to produce adequate ventilation.For the solution of the engineering problem,
the volume of air required and the pressure necessary
to circulate that volume must "be known* As the
efficiency obtained from the ventilator will depend
largely on the accuracy of this estimate, the
determination of the P-Q relation for the mine becomes
a matter of import. The task, however, is one which
presents considerable difficulty
