feet.
Cordier, on the contrary, considers this amount somewhat
overstated and reduces the general average to one degree
Centigrade for every twenty-five metres, or about one degree of
Fahrenheit for every forty-five feet English measure.

_Thirdly._ That the lavas taken from all parts of the world, when
subjected to chemical analysis, indicate that they all proceed
from a common source; and

_Fourthly._ On no other hypothesis can we account for the change
of climate indicated by fossils.

The rate of increase of heat in the Dudzeele shaft was no less
than one degree Fahrenheit for every thirty feet English measure.

At the time of recommencing sinking in the shaft on the 10th of
April, 1849, the perpendicular depth was twenty-three hundred and
seventy feet, the thermometer marking forty-eight degrees
Fahrenheit at the surface; this would give the enormous heat of
one hundred and twenty-seven degrees Fahrenheit at the bottom of
the mine. Of course, without ventilation no human being could
long survive in such an atmosphere, and the first operations of
the commission were directed to remedy this inconvenience.

The report then proceeds to give the details of a very successful
contrivance for forcing air into the shaft at the greatest depths, only
a portion of which do we deem it important to quote, as follows:

The width of the Moer-Vater, or Lieve, at this point, was ten
hundred and eighty yards, and spanned by an old bridge, the stone
piers of which were very near together, having been built by the
emperor Hadrian in the early part of the second century. The rise
of the tide in the North Sea, close at hand, was from fifteen to
eighteen feet, thus producing a current almost as rapid as that
of the Mersey at Liverpool. The commissioners determined to
utilize this force, in preference to the erection of expensive
steam works at the mouth of the mine. A plan was submitted by
Cyrus W. Field, and at once adopted. Turbine wheels were built,
covering the space betwixt each arch, movable, and adapted to the
rise and fall of the tide. Gates were also constructed between
each arch, and a head of water, ranging from ten to fifteen feet
fall, provided for each turn of the tide--both in the ebb and the
flow, so that there should be a continuous motion to the
machinery. Near the mouth of the shaft two large boiler-iron
r