[133] As one more conspicuous than any other, it must be stated that, in March 1832, Mr. Bennet Woodcroft patented an “increasing screw-propeller,” which he thus describes: “A spiral worm blade or screw coiled round a shaft (this resembles the invention of Watt) or cylinder of any convenient length and diameter, in such form that the angle of inclination which the worm makes with the axis of the cylinder continually increases, and the pitch or distance between the coils or revolutions of the spiral, continually increases throughout the whole length of the shaft or cylinder upon which the spiral is formed.” (Specifications of “Marine Propulsion,” Part II. p. 112.) [134] The number of claimants to every important invention is remarkable. An impartial student will, however, probably come to the conclusion that the invention of the screw and its application was, like that of the steam-engine itself, the sole property of no one man, as he finds by research that experiments to discover the means of applying the screw as a motive power to ships were at different periods spontaneously and independently made in various places by inquiring minds, who frequently were perfect strangers to each other and to each other’s discoveries or appliances; yet, as time passes on, and the labours of others are forgotten, a nation or a town claims for some one of its countrymen or townsmen who may have experimentalised on an invention which has become of great use to mankind, the sole or the largest share of the credit of the invention, and erects in their midst an enduring monument of his fame. Such would appear to be the case of Frédéric Sauvage, who has just (October, 1874) had a statue erected to his memory in the town of Boulogne-sur-Mer, where he was born on the 20th of September, 1786. On either side of the monument (which is 14 feet high surmounted by a large bronze bust of M. Sauvage) is an inscription setting forth the date of his birth and of the translation of his remains, together with a list of his inventions. On the front are the two words “Frédéric Sauvage,” and a bronze bas-relief showing a vessel with a screw-propeller. Frédéric Sauvage’s life was similar to those of many other inventors, in that he spent his days and fortune in perfecting inventions which brought him no profit. Having lost his own money, he borrowed from others, and, being unable to repay, was thrown into a debtors’ prison, which he afterwards exchanged for a madhouse, where he died on the 19th of July, 1857. [135] “The Screw-Propeller: who Invented it?” by Robert Wilson, published by Thomas Murray and Son, Glasgow, 1860. [136] See “Specifications relating to Marine Propulsion,” Part II. pp. 127 and 128; _London Journal_ (Newton’s), p. 14, conjoined series, p. 34; _Mechanics’ Magazine_, vol. xxvii. p. 130, vol. xxviii. p. 215, vol. xxix. pp. 143 and 283, and vol. xlii. p. 225; _Artizan_, vol. viii. pp. 187 and 209; also Bourne “On the Screw-Propeller,” pp. 30 and 34.