nt
President of the Royal Society; and Belgium, Dr. Secchi, since so
famous for his spectroscopic observations on the fixed stars.
These gentlemen, after organizing at Paris, spent almost an
entire year in traveling before a site for the scene of
operations was selected. Finally, on the 10th of April, 1849, the
first ground was broken for actual work at Dudzeele, in the
neighborhood of Bruges, in the Kingdom of Belgium.

The considerations which led to the choice of this locality were
the following: First, it was the most central, regarding the
capitals of the parties to the protocol; secondly, it was easy of
access and connected by rail with Brussels, Paris and St.
Petersburg, and by line of steamers with London, being situated
within a short distance of the mouth of the Hond or west Scheldt;
thirdly, and perhaps as the most important consideration of all,
it was the seat of the deepest shaft in the world, namely, the
old salt mine at Dudzeele, which had been worked from the time of
the Romans down to the commencement of the present century, at
which time it was abandoned, principally on account of the
intense heat at the bottom of the excavation, and which could not
be entirely overcome except by the most costly scientific
appliances.

There was still another reason, which, in the estimation of at
least one member of the commission, Prof. Watson, overrode them
all--the exceptional increase of heat with depth, which was its
main characteristic.

The scientific facts upon which this great work was projected,
may be stated as follows: It is the opinion of the principal
modern geologists, based primarily upon the hypothesis of Kant
(that the solar universe was originally an immense mass of
incandescent vapor gradually cooled and hardened after being
thrown off from the grand central body--afterward elaborated by
La Place into the present nebular hypothesis)--that "the globe
was once in a state of igneous fusion, and that as its heated
mass began to cool, an exterior crust was formed, first very
thin, and afterward gradually increasing until it attained its
present thickness, which has been variously estimated at from ten
to two hundred miles. During the process of gradual
refrigeration, some portions of the crust cooled more rapidly
than others, and the pressure on the interior igneous mass being
u