their inventions in the
only practicable way, by building an experimental boat and using it.

In spite of this apparent lack of faith on the part of the men who
worked on the submarine problem, it would not be fair to condemn
them as fakirs. Experimental workers, in those times, had to face
many difficulties which were removed in later times. The study of
science and the examination of the forces of nature were not only
not as popular as they became later, but frequently were looked upon
as blasphemous, savouring of sorcery, or as a sign of an unbalanced
mind.

[Illustration: (C) Kadel & Herbert.

_A Gas Attack Photographed from an Airplane._]

England and France supplied most of the men who occupied themselves
with the submarine problem between 1610 and 1760. Of the
Englishmen, the following left records of one kind or another
concerning their labours in this direction. Richard Norwood, in
1632, was granted a patent for a contrivance which was apparently
little more than a diving apparatus. In 1648, Bishop Wilkins
published a book, _Mathematical Magick_, which was full of rather
grotesque projects and which contained one chapter on the
possibility "of framing an ark for submarine navigation." In 1691,
patents were granted on engines connected with submarine navigation
to John Holland--curious forerunner of a name destined to be famous
two hundred years later--and on a submarine boat to Sir Stephen
Evance.

In Prance, two priests, Fathers Mersenne and Fournier, published in
1634 a small book called _Questions Theologiques, Physiques, Morales
et Mathematiques_, which contained a detailed description of a
submarine boat. They suggested that the hull of submarines ought to
be of metal and not of wood, and that their shape ought to be as
nearly fishlike as possible. Nearly three hundred years have hardly
altered these opinions. Ancient French records also tell us that six
years later, in 1640, the King of France had granted a patent to
Jean Barrie, permitting him during the next twelve years to fish at
the bottom of the sea with his boat. Unluckily Barrie's fish stories
have expired with his permit. In 1654, a French engineer, De Son, is
said to have built at Rotterdam a submarine boat. Little is known
concerning this vessel except that it was reported to have been
seventy-two feet long, twelve feet high, and eight feet broad, and
to have been propelled by a paddlewheel instead of oars.

Borelli, about whom very l