The problem of aërial navigation seems at present to be agitating as many pseudo-scientific minds as did that of perpetual motion not many years ago, or the philosopher's stone at a more remote period. It possesses perhaps a still stronger attraction in the danger connected with the experiments--the source, we suppose, of the eagerness shown by Professor Wise and his associates to _fly_ to evils that they know not of. Perpetual motion received its quietus from the blasts of ridicule. Air-voyaging has a worse foe to encounter. It may survive the attacks of gayety, but it will succumb, we fancy, to the resistless force of _gravity_. LITERATURE OF THE DAY. Scintillations from the Prose Works of Heinrich Heine. New York: Holt & Williams. The task formerly undertaken by Mr. Charles Godfrey Leland, in adapting to our language the songs of Heine, is now well supplemented with some versions from among his prose works by another Philadelphian translator, Mr. Simon Adler Stern. Heine's prose, delicate in its pellucid brightness as any of his poetry, cannot be held too precious by the interpreter. The latter must have all his wits about him, or he will not find English at once simple enough and distinguished enough to stand for the original. To get at Heine's prose exactly in another language must be almost as hard as to get at his poetry. The principal selection made by Mr. Stern is a long rambling rhapsody called "Florentine Nights," in which the author professes to pour into the ears of a dying mistress the history of some of his former amours and exaltations, the natural jealousy of the listener going for a stimulus in the recital. His first love, however, is an idealization--a Greek statue which he visits by moonlight, as Sordello in Browning's poem does the Shrinking Caryatides Of just-tinged marble, like Eve's lilied flesh.