In the diary of Lewis Frederick, Prince of Wurtemberg, under date Tuesday, May 1, 1610, occurs the passage, “His Excellency went to Elham Park to see the perpetual motion; the inventor’s name was Cornelius Trebel, a native of Alkmaar, a very fair and handsome man, and of very gentle manners, altogether different from such-like characters; we also saw there Virginals, which played of themselves.” Undoubtedly Drebbel was ahead of his time, but one cannot credit him with all the wonders he is reported to have achieved. Some of his biographers state that he invented a telescope, a microscope, and a thermometer; an incubator for hatching fowls; an instrument for showing pictures of portraits of people not present at the time, and a method of producing at will the most extreme cold. Drebbel was evidently highly thought of at the Courts of James I., Rudolph II., and Ferdinand II., but this was perhaps due more to his being “a very fair and handsome man of very gentle manners,” than to his scientific attainments. One of his biographers refers to him thus: “Cornelius van Drebbel, ein Charlatan,” and others have dubbed him alchemist, empiric, magician, and professor of the Black Art. Mr. Rye’s estimate is perhaps the truer:— “But however extravagant and improbable some of the following descriptions may appear, yet, allowing as we ought to do for the crude state of physical science and the credulity of the times in which he lived, as well as the then prevailing tendency to clothe scientific investigation and experiment with an air of mystery, Cornelius Drebbel is entitled, we think, to hold a respectable position among the ingenious inventors and mechanicians of the early part of the seventeenth century.” [Sidenote: Bishop Wilkins on Submarine Navigation.] Drebbel’s boat attracted the attention of the Right Reverend John Wilkins, whose mathematical and philosophical works were published in London in the year 1708. John Wilkins was a remarkable man, considerably in advance of his day in scientific speculation. As few people nowadays read his books a brief extract from his “Mathematical Magick: or the Wonders that may be perform’d by Mechanical Geometry” may be read with interest and amusement. The book is divided into two parts, the first entitled “Archimedes, or Mechanical Powers,” the second, “Doedalus, or Mechanical Motions.” Chapter V. of Part 2 deals with “the possibility of framing an Ark for Submarine Navigation: the Difficulties and Consequences of such a Contrivance.”