Dr. Wilkins is, however, convinced that, above all, his Ark will be most valuable in the discovery of submarine treasures, “not only in regard of what hath been drowned by Wrecks, but the several precious Things that grow there; as Pearl, Coral Mines; with innumerable other Things of great Value which may be much more easily found out and fetch’d up by the help of this than by any of the usual ways of the Urinators.” For the better fulfilment of this purpose, the author suggests that there should be some lesser cabins tied about the Great Ark at various distances, where several persons as Scouts might be lodged for the taking of observations according as the Admiral should direct them. Dr. Wilkins’ prediction has been realised, and in Mr. Simon Lake’s _Argonaut_ there exists a machine which is bound to play an important part in “the discovery of Submarine Treasure.” In the penultimate paragraph of the chapter on the Submarine Ark Dr. Wilkins waxes enthusiastic over the immense possibilities latent in such a contrivance. “All kinds of Arts and Manufactures may be exercised in this Vessel. The Observations made by it might be written and (if need be) Printed here likewise. Several Colonies may there inhabit, having their Children born, and bred up, without the knowledge of land, who could not chuse but be amazed with Strange Conceits upon the Discovery of this Upper World.” In conclusion the author writes:— “I am not able to judge what other Advantages there may be suggested, or whether Experiment would fully answer these Notional Conjectures. But, however, because the Invention did unto me seem ingenious and new, being not impertinent to the present Enquiry therefore I thought it might be worth the mentioning.” [Sidenote: Mersenne.] “Mersennus,” to whom the learned Bishop refers, was a monk of the order of the “Minims,” who lived from 1588–1648, and was the chief friend and literary agent of Des Cartes. He gave in his writings some attention to submarine navigation. He proposed that the shell of a boat which he projected, but never built, should be of copper or some other metal, and that in shape it should resemble a fish, and in order to avoid its turning round both ends should be pointed.