It is thus that the figures of pantaloon and clown become visible, and their apparent relative movements are occasioned. For instance; each time that the impression of the figure of the pantaloon is renewed, he is seen in the same place and in the same attitude; therefore he appears to be stationary, though the successive pictures that compose his figure to the eye are in rapid rotary motion. The figure of the clown, however, is seen in a different position each time that he comes into view, therefore he appears to be in motion relatively to pantaloon, though stationary as regards his absolute position on the disc. The same effect would be produced if the disc, during its rotation, were seen by successive electric sparks. The electric spark is so momentary in its duration, that the most rapidly moving objects appear stationary; therefore each spark would show a seemingly stationary disc, on which the figure of the clown would appear in different relative positions; and the illusion would be as perfect as when the rays of light are interrupted at intervals. The electric spark is so instantaneous that a cannon ball might be seen in its rapid flight, if illuminated by a flash of lightning, and would seem to be stationary. Professor Faraday mentioned, in one of his lectures, the extraordinary appearance which a man, who was jumping over a stile, presented when seen by lightning on a dark night. The man seemed to be resting horizontally in the air, with one hand touching the stile. The duration of the impression of an object on the retina is capable of illustration by means of the Magic Disc in a great variety of designs, each one of which may represent many movements. The turning of the wheels of machinery, the tossing of balls, the dancing figures of men and women may thus be shown, the designs for which afford ample scope for exercising the pencil of an ingenious artist. THE DIORAMA. Those who are old enough to remember the Regent's Park before there were any houses northward of the New Road, may recollect that among the first buildings erected, on what is now called Park Square, was a strange-looking, partly semi-circular erection, provided with ample lighting space, which attracted great attention during its progress, and was the cause of much speculation as to its probable purpose. That building was intended for the exhibition of the Diorama. M. Daguerre, the inventor of the Daguerreotype, had, in conjunction with M. Bouton, a short time previously opened a similar exhibition in Paris, where the beauty of the paintings, aided by the extraordinary effects of newly contrived dispositions of the light, had excited a great sensation. The Diorama was opened in London on the 6th of October, 1823, and for a long time it was equally popular in this metropolis.