In Prance, two priests, Fathers Mersenne and Fournier, published in 1634 a small book called _Questions Théologiques, Physiques, Morales et Mathématiques_, 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 Barrié, permitting him during the next twelve years to fish at the bottom of the sea with his boat. Unluckily Barrié'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 little seems to be known, is credited with having invented in 1680 a submarine boat, whose descent and ascent were regulated by a series of leather bottles placed in the hull of the boat with their mouths open to the surrounding water. The English magazine, _Graphic_, published a picture which is considered the oldest known illustration of any submarine boat. This picture matches in all details the description of Borelli's boat, but it is credited to a man called Symons.
Twenty-seven years later, in 1774, another Englishman, J. Day, built a small submarine boat, and after fairly extensive experiments, descended in his boat in Plymouth harbour. This descent is of special interest because we have a more detailed record of it than of any previous submarine exploit, and because Day is the first submarine inventor who lost his life in the attempt to prove the feasibility of his invention. The _Annual Register_ of 1774 gives a narration in detail of Day's experiments and death and inasmuch as this is the first ungarbled report of a submarine descent, it may be quoted at length.
_Authentic account of a late unfortunate transaction, with respect to a diving machine at Plymouth._