We show herewith the method employed by the Baltimore Car Wheel Company in casting chilled wheels to prevent tread defects. The ordinary mode of pouring from the ladle into the hub part of the mould, and then letting the metal overpour down the brackets to the chill, produces cold shot, seams, etc. In the arrangement here shown the hub core, A, has a concave top, B, and the core seat, C, is convex, its center part being lower than the perimeter of the top of the core. Figs. 3, 4, show the core, A, in the side elevation and in plain. Fig. 2 is a core point forming a space to connect the receiving chamber, E, above, with the mould by passageways, D D, formed in the side of the top of the core. The combined area of these passageways being less than that of the conduit, F, from the receiving chamber, the metal is skimmed of impurities, and the latter are retained in the receiving chamber, E. The entering metal flows first to the lower hub part at H H, thence by the sprue-ways, G G, to the lower rim part at J J, being again skimmed at the mouth of the sprue-ways. Thus the rim fills as rapidly as the hub, and the metal is of a uniform and high temperature when it reaches the chill. [Illustration: CASTING OF CAR WHEELS.] In the wheels made by this firm, every alternate rib is connected with the rim, and runs off to nothing near the hub; the intermediate ribs are attached to the hub, and diminish in width toward the rim.--_Jour. Railway App._ * * * * * ELECTRICITY AND PRESTIDIGITATION. The wonderful ease with which electricity adapts itself to the production of mechanical, calorific, and luminious effects at a distance, long ago gave rise to the idea of applying it to certain curious and amusing effects that simple minds willingly style _supernatural_, because of their powerlessness to find a satisfactory explanation of them. [Illustration: FIG. 1.--RAPPING AND TALKING TABLE. ] Who has not seen, of old, Robert Houdin's heavy chest and Robert Houdin's magic drum? These two curious experiments are, as well known, founded upon the properties of electro-magnets. At present we shall make known two other arrangements, which are based upon the same action, and which, presenting old experiments under a new form, rejuvenate them by giving them another interest.