AT its sitting of July 17, 1881, the Royal Venetian Institute of Sciences proposed as the subject of a prize an examination of recent hypotheses regarding the causes of luminous, thermal, electrical, and magnetic phenomena. The volume now before us is one of seven competing treatises produced by the end of March 1883. As to the vastness of its scope, and the extent of erudition displayed in it, we can fully ratify the sentence of the examiners officially deputed to pronounce upon its merits. It is an “attack all along the line,” and one conducted with no despicable array of mustered forces. The author has read and pondered much on the subjects he treats of; he is a mathematician, and is hence alive no less to the value of mathematical evidence, than to the worth-lessness of a mere hollow show of mathematical formulæ; while the hypotheses he criticises have usually been tried by the severe test of a serious endeavour to realise their consequences. Many of his objections we at once admit to be valid; indeed, no universal explanation of physical phenomena has yet been proposed of which the structure was not riddled with visible absurdities. The late Prof. Challis devoted his considerable abilities and his best energies to the elaboration of a hydrodynamical theory of the universe, in which physical effects of all kinds were referred to forms of pressure of a continuous elastic medium. But the suggestion that an indefinite ascending series of such media might, after all, be necessary to produce the required results, cannot be looked upon otherwise than as a confession of failure. Father Secchi's heroic effort, in his “Unità delle Forze Fisiche,” to see right down to the very bottom of things, was scarcely more successful. The reasonings upon which it was founded (as our author, among others, rightly points out) were vitiated at the root by a misapplication of Poinsot's theorems on the resilience of rotating bodies; and the cosmical machinery put together with such ingenuity, and set going with such heedful solicitude, came at once to a deadlock. Nor do we anticipate any better results from the scheme which Prof. Zanon himself promises to expound in a forthcoming work. The glimpses of his views afforded in essays already before the public are not encouraging. There is absolutely nothing gained in devolving the responsibility of our ignorance upon phrases, and taking their obscurity for illumination. If we can find no adequate explanation of the activities manifested in the wonderful “frame of things,” of which we are at once spectators and participators, let us, in the name of candour and common-sense, acknowledge our impotence; but let us not imagine that we in any sense repair or qualify it by talking of inherent qualities, “virtues,” propagated “influences,” “molecular tensions,” and the like. This would be to fall back into the rut out of which Moliere did something to help us with Argan's famous diploma-examination:— Le Ipotesi Fisiche. Analizzate da Giannantonio Zanon. (Venezia: Lorenzo Tondelli, 1885.)