=N.B.=—The groove A to C was concealed from the audience by handsome curtains, which were repeated at the same angle on the other side, from M to D. K.—Place where the objects to be reflected in the looking-glass were placed, but quite concealed from the audience with a door, closed when the exhibition was going on. ] [Illustration] A C D E are the outside of the room, 12 feet square, engraved glass running from H A to A D. The wing E G is placed square; this is an immense advantage, as it renders unnecessary any counterpart at C N, and as, of course, it cannot be seen, the light from the foot-lights on E G is not seen by reflection at C N. When the wing E G was at the same angle as H A, this was always a weak point in the illusion, as when the glass crossed, the reflection of E G, unless very dimly illuminated, always shewed. Now it does not matter when E G is placed as in drawing. The frontage to the audience, instead of being from A F, is now extended to E—_i.e._ 12 feet—consequently the return sides F E and C B can be removed. This plan, of course, precludes the use of “trick” chairs, baskets, &c. &c.; but it has a good many other advantages in its favour, for with a “sociable” in the middle of the room made in two exact halves, these halves trick or cover one another when the glass is pushed across, and of course this movement is not seen by the audience; then any person or persons can be made to appear gradually, sitting or standing, at L or M, _right in the middle of the wide open room_. Mr. Walker tried this effect at the Polytechnic Institution, and it was capital—the ensemble is more imposing. This plan of shewing the illusion is the plan for the stage, as the necessity for darkening the stage in front is nearly wholly avoided. The back of the side-wing I K can be painted black, so that its reflection shall not be seen. In lieu of the gas-jets, as now arranged, there is a gas-lamp; this is placed on a pedestal or small table. The shadow of the “sociable” to a great extent covers or hides the path along which the glass travels. Mr. Walker says: “I thought out this way for Mr. Irving’s necessities, but I did not hear anything from him; and it has come in well for Mr. Burnand’s sketch, which has been produced.” In this sketch, a gentleman afflicted with dyspepsia through eating “curried prawns” (the name of the piece), calling on some friends, where he has promised to help them in some amateur theatricals, looks at the different costumes of Mephistopheles, Faust and Marguerite, and throws them carelessly on the seat at M, walks down the steps (which we shall double in width) the glass now crosses, and, whilst in a fit of melancholy, he wonders if Mephistopheles will appear. Sure enough, he does. Mephistopheles then comes down in front, and with incantations makes, successively or together; Faust and Marguerite appear; they then disappear in the same manner.