It has been pointed out by several authorities that some of M. de l'Isle's statements in his memoir of 1752 are to be received with caution, especially his elaborate endeavors to impress the Paris Academy with the belief that the discoveries of Bering subsequent to the first voyage were the result of his (de l'Isle's) own carefully considered instructions. In this connection Adelung says:
"De l'Isle, in his Explication de la carte des nouvelles découvertes au Nord [1752], traces out his proposed route quite differently [referring to de l'Isle's previous statements in his report to the St. Petersburg Academy in 1732], somewhat as if it had been outlined in view of accomplished facts."
It behooves us, then, to inquire carefully into the authenticity of the alleged map of de l'Isle of 1731, since if he antedated his opinions as to the route he might also have antedated his map. Fortunately we do not have to depend only on de l'Isle's own statement, either in 1750 before the Academy of Sciences at Paris, or as published in 1738 at St. Petersburg and printed at the printing office of the Royal Academy; for we also have extraneous and convincing evidence, even from sources critically hostile to the French astronomer.
M. de l'Isle, in his Mémoires sur les Nouvelles découvertes au Nord de la mer du Sud, Paris, 1752, says:
"After I had, near twenty years ago, got these first informations of the longitude of Kamschatka by means of Captain Bering's map and journal, I made use of them in constructing the map, representing the eastern extremity of Asia, with the opposite coast of North America, in order to show at once what still remains for discovery between two large parts of the world.
"This map I had the honor of presenting to the Empress Anne and the Senate, in order to animate the Russians to undertake these discoveries, and it took effect, this princess ordering a second voyage to be made according to the plan which I had drawn up for it."
"Two maps," he adds, were presented to the Academy in Paris, "one being a copy of the map which I had drawn at St. Petersburg, 1731, on Captain Bering's first voyage, and had the honor of presenting to the Empress Anne and the Senate, with a manuscript memoir explaining its use and construction." The other map (from which the lithograph before you was lately reproduced) was, according to de l'Isle, only changed by adding the later discoveries of Bering and his lieutenants.
De l'Isle further says of this chart:
"The second manuscript map which I laid before the Academy at Paris was in all respects like the former, only with the advantages of the new discoveries made since 1731."