A correspondent, who is evidently fully master of details, which he has given at length, informs me that “The Moon Hoax” first appeared in the New York _Sun_, of which R. A. Locke was editor. It so much resembled a story then recently published by Edgar A. Poe, in a Southern paper, “Adventures of Hans Pfaall,” that some New York journals published the two side by side. Mr. Locke, when he left the New York _Sun_, started another paper, and discovered the manuscript of Mungo Park; but this did not deceive. The _Sun_, however, continued its career, and had a great success in an account of a balloon voyage from England to America, in seventy-five hours, by Mr. Monck Mason, Mr. Harrison Ainsworth, and others. I have no doubt that M. Nicollet was the author of “The Moon Hoax,” written in a way which marks the practised observatory astronomer beyond all doubt, and by evidence seen in the most minute details. Nicollet had an eye to Europe. I suppose that he took Poe’s story and made it a basis for his own. Mr. Locke, it would seem, when he attempted a fabrication for himself, did not succeed. In his remark that “there seems to have been a French edition, the original,” Augustus De Morgan was undoubtedly misled, for every authority consultable agrees that the French pamphlets were merely translations of the story originally printed in the _Sun_; and De Morgan had learned this when he wrote his second note on the subject. The M. Arago whom De Morgan believes Nicollet sought to entrap was Dominique François Arago, the celebrated astronomer. In 1830, as a reward for his many accomplishments, he was made perpetual secretary of the Paris Academy of Sciences, and in the following year--the year of Nicollet’s fall from grace--he was elected to the Chamber of Deputies. As to the intimation that Arago was really misled by the moon story, it is unlikely. W. N. Griggs, a contemporary of Locke, insists in a memoir of that journalist that the narrative was read by Arago to the members of the Academy, and was received with mingled denunciation and laughter. But hoaxing Arago in a matter of astronomy would have been a difficult feat. Surely the discrepancies pointed out by Poe would have been noticed immediately. It is, however, easy to understand De Morgan’s belief that Nicollet was the author of the moon story. Much of the narrative, particularly parts which have here been omitted, is made up of technicalities which could have come only from the pen of a man versed in the intricacies of astronomical science. They were not put into the story to interest _Sun_ readers, for they are far over the layman’s head, but for the purpose of adding verisimilitude to a yarn which, stripped of the technical trimmings, would have been pretty bald.