112 OPTICAL EXHIBITION. placed between the focus and the surface of the mirror. The image then appears behind the mirror, upright, curved, and very much magnified. But if we place the object, as we have done just now, so distant that the focus of the mirror shall be between the object and the glass, then the image will be formed in the air before the mirror.* I recollect, many years since, going to see an exhibition in London, which consisted of many curious deceptions, produced by a concave mirror. It was so contrived, that the spectators did not see the mirror, or the real object reflected in it; both these were behind the partition of an inner room, where the object was strongly illuminated by a lamp. The outer apartment was darkened, and one person at a time was requested to look into a glass placed in the partition. An image then appeared in the air, between the eye and the glass: the figure of a man in a long, loose gown, who seemed to extend his hand and offer you a nosegay; it looked so * Ibid, v. p. 119 and 121. OPTICAL EXHIBITION. 113 natural, that the spectator attempted to grasp it, to the great amusement of the bystanders, who could see nothing; as you know was the case with yourselves just now, when one of you was trying to grasp her own inverted image. In the exhibition I am describing, the image was not inverted; the whole appearance was like reality. The phantom withdrew the nosegay, and again extending his hand, presented a bird. That too was withdrawn, and he offered the ivory handle of a dagger; but when the spectator extended his hand to receive it, the phantom suddenly turned the dagger, and made such a natural thrust with the point of it, that every person of the party, who saw it in succession, started back, though a few minutes before they had been laughing at their companions for grasping and starting at nothing. I cannot exactly tell you how this deception was managed, for the audience, as you may suppose, were uninitiated persons, to whom none of these mysteries were revealed; but I am inclined to think that the phantom was the reflected image of an 114 OPTICAL EXHIBITION. automaton, whose motions were secretly regu lated by the exhibitor himself. Another part of this optical entertainment, was a view of Scarborough, a sea-port town in Yorkshire, frequented as a bathing-place. It stands in the recess of a beautiful bay, on the shore of the German Ocean. The town rising from the water's edge in the form of an amphitheatre; the ruins of the ancient castle, crowning the top of a lofty promontory; and the wide expanse of ocean, were the striking features of this magic picture. Like the phantom, it was visible only to those who looked through a glass or lens, which was fixed in the wall of the apartment, and appeared to be a small window hung round with drapery. While you were looking at the town, and admiring its picturesque situation, the scene, which resembled a real view rather than a painting, became gradually darkened; heavy clouds overspread the serene, blue sky; and the gloom increased to a deep obscurity, through which no outline could be distinctly traced. Suddenly the darkness CORNELIUS AGRIPPA. 115 was dispelled by the most beautiful imitation of lightning I ever saw; momentary flashes, showing the cliffs and buildings of the town, just as they might have done in reality. The clouds soon passed away, and the prospect again appeared to be illuminated by the cheerful light of the sun. There is no doubt that such a deception may be produced by a magnifying lens, and the skilful management of a lamp placed behind a picture, painted as a transparency. It was probably by a similar contrivance, that Cornelius Agrippa exhibited the "ladye of his heart" to Lord Surrey; and as we have in this Lecture been pretty much confined to a literal account of the effects produced by reflection and refraction, I think we may now be permitted to admire the imagery, which the operation of these powers has suggested to the imagination of a poet. 'Twas All-Soul's eve, and Surrey's heart beat high; He heard the midnight bell with anxious start, When wise Cornelius promised, by his art, 116 CORNELIUS AGRIPPA To show to him the ladye of his heart: Yet so the sage had hight to play his part, That he should see her form, in life and limb, And mark if still she loved, and still she thought of him. Dark was the vaulted room of gramarye, To which the wizard led the gallant knight; Save that before a mirror, huge and high, A hallowed taper shed a glimmering light On mystic implements of magic might, On cross, and character, and talisman, And almagist, and altar, nothing bright; For fitful was the lustre, pale and wan As watch-light by the bed of some departing man. But soon within that mirror, huge and high, To form a lordly and a lofty room, Part lighted by a lamp, with silver beam, Placed by a couch of Agra's silken loom, And part by moonshine pale, and part was hid in gloom. Fair all the pageant-but how passing fair The slender form which lay on couch of Ind! O'er her white bosom strayed her hazel hair; And pensive read, from tablet eburnine, Some strain that seemed her inmost soul to find: Slow rolled the clouds upon the lovely form, |