The whole, as well as certain mechanical inventions, were managed with dexterity and address. The lightning, being produced by the camera, was tame, and had not the brisk transient appearance of the lightning at the theatres, which is produced by rosin, or lycopodium powder, thrown through a light, which in Mr. P's utter darkness might easily have been concealed in a kind of dark lantern. A plate of thin sheet iron, such as German stoves are made of, is an excellent instrument for producing the noise of thunder. It may be three or four feet long, and the usual width. When this plate is held between the finger and thumb by one corner, and suffered to hang at liberty, if the hand be then moved or shaken horizontally, so as to agitate the corner at right angles to the surface, a great variety of sounds will be produced; from the low rumbling swell of distant thunder, to the succession of loud explosive bursts of thunder from elevated clouds. This simple instrument is very manageable, so that the operator soon feels his power of producing whatever character of sound he may desire; and notwithstanding this description may seem extravagant, whoever tries it for the first time will be surprised at the resemblance. If the plate be too small, the sound will be short, acute, and metallic. We may remark also, that the magic lantern, by new contrived sliders and machinery, may be applied to important uses, by employing it with such figures as will explain the general principles of optics, astronomy, botany, &c. The experiment mentioned by Ferguson, with a concave mirror, reflecting into the air the appearance of fire, &c. into a focal point, (founded on a general principle of concave reflectors,) is productive of many agreeable deceptions, and which exhibited with art and an air of mystery, has been very successfully employed. The phantasmascope of Walker is similar to the phantasmagoria. It is an optical machine, which presents a door that opens itself. The apparatus is so contrived, that, on opening the door, a phantom makes its appearance, having all the colours of a picture, which approaches the spectator. Various figures may be accurately represented. We will not enlarge on this subject, although many other instances of tricks, performed by means of fire, &c. might be noticed. We will merely remark: 1. For the performance of these exhibitions, the ancient, as well as the modern jugglers, of _all_ descriptions, employed, and were acquainted with sundry mixtures, and compositions, by the use of which, they deceived the people; and some pretended to possess supernatural agencies. Of these compositions, with many of which we are unacquainted, we have enumerated some, and their effects. That of producing a callosity of the skin, &c. by means of acids, is an example.