polished glass" windows would be noteworthy with a scientific observer.

The "transparent mirror" of my own invention above twenty years ago never appeared to me as of any practical value until some seven years back, and in principle it was most likely very nearly allied to that of Porta's. But to say that Porta's observations, or even my own early invented mirror, had it been published, agree in design with the phantasmagoria of my invention, would only be a display of exceedingly weak discriminatory power in forming a judgment between inventions generally.

My invention is not one for raising a spectral appearance at a distance, or shut up in a chamber, as a mere phantom to be gazed at in its solitary cell. By means of concave mirrors, by magic lanterns, and by the phantasmagoria as early as 1802, these solitary, inaccessible spectres could be set on a stage for public gaze.

But what comparison is there between such spectral effects and spectres that can be made to appear to act, play, fence, fight, fire, and associate and act in concert with any living actor or actors, on the same stage? Why did not Porta think of this 300 years ago? How came I to miss it above twenty-five years back? Why, for the simple reason that such an idea never struck either of us at those earlier periods; and that of the millions of persons who have seen Porta's window spectres no one but myself ever hit upon the idea of associating a substance with a shadow possessing all the external characteristics of

a corporeal being. In this consists the gist of my invention, as I shall presently explain more at large.

Before the publication of my invention in 1858, I had conversations with several eminent theoretical, as well as with some excellent practical, opticans, principally with a view, as I stated, to correct my own estimate of my discovery. Optical science affords but limited scope for introducing a decided novelty, and I was in consequence quite prepared for the scepticism I created. One gentleman, surrounded in his study with exquisitely executed microscopes, varieties of telescopes, and numerous lesser optical instruments, after a patient hearing of the wonders I proposed to execute, recapitulated a brief history of all that had been done to the best of his knowledge. He specially noticed concave mirrors; also some costly but curious contrivances which produced phantoms something analogous, as he then thought, though the figures were rarely of more than three feet high. When I replied that by my arrangement of apparatus I was not limited to six feet in height, and that too without incurring any extraordinary expenditure, he appeared to be at once satisfied that the whole affair was either a great mistake, or a still greater discovery. Such was the result of a conversation I had early in 1858, with Dr. Bachhoffner, at the Colysseum.

Persuaded by my own early knowledge of optical science, together with the results of more recent investigation, and fortified by the opinions obtained through

verbal communications in various quarters, I felt justified in considering the originality of my phantasmagoria pretty well established. But to test it still further I determined on communicating the account of its construction and properties to the British Association, and a small model, as already mentioned, which I placed on the table, was afterward forwarded to Sir David Brewster.

As early as 1834 I had been concerned in the use of the oxyhydrogen and the electric light. I had in my capacity of honorary secretary to scientific institutions given courses of from three to twelve lectures on electricity and on chemistry; and more recently had seen the lime-light used for public lighting purposes. Every scientific man knows that the term "strong light" means a light of some one of the descriptions mentioned; and we are not to suppose that the omission of naming any of these in Sir David Brewster's "Letters on Natural Magic," is any more evidence of his want of a knowledge of such "strong lights," than a like omission in the following chapter proves anything against the author's want of acquaintance with the lime and other lights.

CHAPTER II.

THE ORIGINAL COMMUNICATION MADE TO THE BRITISH

ASSOCIATION, AT THEIR MEETING IN LEEDS, SEPTEMBER

1858, IN A PAPER ON AN APPARATUS FOR EXHIBITING OPTICAL ILLUSIONS, ILLUSTRATING MENA."

SPECTRAL PHENO

AMONG the happy results of modern discoveries we may particularly notice the different use made of whatever appertains to the wonderful, as compared to the employment which the same would have been subject to in superstitious ages. Our natural magic makes no pretension to an occult science, but on the contrary tends to dissipate many vulgar errors, by disabusing the public mind, even on matters long considered supernatural. Concave mirrors, magic lanterns, phantasmagoria, and similar optical instruments, afford ample illustration of the happy tendency of modern investigation over the once degrading employment of superior knowledge only to impose on rather than enlighten the ignorant. In his excellent "Letters on Natural Magic," Sir David Brewster casually observes that :-"The concave mirror is the staple instrument of the magician's cabinet, and must always perform a principal part in all optical combinations." But why he should thus predict that concave mirrors "must always perform a principal part in optical

illusions," is by no means very apparent, and particularly as he directs attention in the same letters to a serious obstacle in their use, remarking that the apparition may be from an illuminated "plaster cast of any object made as white as possible, and placed in an inverted position," adding "the difficulty of placing a living person in an inverted position as an object has, no doubt, prevented the optical conjuror from availing himself of so admirable a resource; but this difficulty (he suggests) may be removed by employing a second concave mirror." Having thus called attention to this best and "staple instrument of the magician's cabinet," notwithstanding the limited use of such concave mirrors, the same writer proceeds to discuss certain deceptions practised with "plane mirrors," requiring the objects to be brightly illuminated and the apartment to be as dark as possible. Of these he says:-"Whatever precautions are taken, and however skillfully plane mirrors are combined, it is not easy to produce with them any very successful illusions." (P. 61, edition 1834.)

I shall now proceed to describe the phantasmagorial* apparatus of my invention for exhibiting optical illusions of a varied character hitherto unknown, except as inventions of romantic fiction, or as the result of some

* The manufacturing philosophical instrument makers having adopted this term in connection with my own name, calling the model apparatus THE DIRCKSIAN PHANTASMAGORIA, I have thought it prudent to reproduce the same designation in my title page.