THE MINERAL DEPTHS
The chapter on "The Origin and Development of Modern Geology," vol.
III., p. 116 _seq._, may be read in connection with the allied subjects
here treated.
In preparing the section on the use of electricity in mining, the
article by Thomas Commerford Martin, entitled _Electricity in Mining_,
in the United States _Census Report_ of 1905, has been freely drawn
upon. The quotations on pp. 262, 266, 268, and 270 are from that source.