se 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
inclined planes. His most demonstrative experiment was a very simple
one, in which a chain of balls of equal weight was hung from a triangle;
the triangle being so constructed as to rest on a horizontal base, the
oblique sides bearing the relation to each other of two to one. Stevinus
found that his chain of balls just balanced when four balls were on the
longer side and two on the shorter and steeper side. The balancing of
force thus brought about constituted a stable equilibrium, Stevinus
being the first to discriminate between such a condition and the
unbalanced condition called unstable equilibrium. By this simple
experiment was laid the foundation of the science of statics. Stevinus
had a full grasp of the principle which his experiment involved, and he
applied it to the solution of oblique forces in all directions. Earlier
investigations of Stevinus were published in 1608. His collected works
were published at Leyden in 1634.

This study of the equilibrium of pressure of