of Galileo, and carried forward the work he had so well begun.
But before passing on to the consideration of their labors, we
must consider work in allied fields of two men who were
contemporaries of Galileo and whose original labors were in some
respects scarcely less important than his own. These men are the
Dutchman Stevinus, who must always be remembered as a co-laborer
with Galileo in the foundation of the science of dynamics, and
the Englishman Gilbert, to whom is due the unqualified praise of
first subjecting the phenomenon of magnetism to a strictly
scientific investigation.

Stevinus was born in the year 1548, and died in 1620. He was a
man of a practical genius, and he attracted the attention of his
non-scientific contemporaries, among other ways, by the
construction of a curious land-craft, which, mounted on wheels,
was to be propelled by sails like a boat. Not only did he write a
book on this curious horseless carriage, but he put his idea into
practical application, producing a vehicle which actually
traversed the distance between Scheveningen and Petton, with no
fewer than twenty-seven passengers, one of them being Prince
Maurice of Orange. This demonstration was made about the year
1600. It does not appear, however, that any important use was
made of the strange vehicle; but the man who invented it put his
mechanical ingenuity to other use with better effect. It was he
who solved the problem of oblique forces, and who discovered the
important hydrostatic principle that the pressure of fluids is
proportionate to their depth, without regard to the shape of the
including vessel.

The study of oblique forces was made by Stevinus with the aid of