"J. WOOD," The next supposed anticipation of the Kaleidoscope was an instrument proposed by Mr. Bradley in 1717. This in strumr lit consists of two large pieces of silvered looking glass,five inches wide, and four inches high, jointed together with hinges, and opening like a book. These plates being set upon a geometrical drawing, and the eye being placed in front of the mirrors, the lines of the drawing were seen multiplied by repeated reflections. This instrument was described long before by Kircher, and did not receive a single improvement from the hands of Bradley. It has been often made by the opticians, and was principally used for multiplying the human face, when placed between the mirrors ; but no person ever thought of applying it to any purpose of utility, or of using it as an instrument of rational amusement, by the creation of beautiful forms. From the very construction of the instrument, indeed, it is quite inca pable of producing any of the singular effects exhibited by the kaleidoscope. It gives, indeed, a series of reflected images arranged round a centre ; but so does a pair of looking-glasses placed angularly in an apartment, and so do the pieces of mirror glass with which jewellers multiply the wares exhibited at their windows. It might therefore be as gravely maintained that any of these combinations of mirrors was a kaleidoscope, as that Bradley's pair of plates was an anticipation of that instrument. As the similarity between the two has been maintained by ignorant and inte rested individuals, we shall be at some pains to explain to the reader the differences between these two instruments ; and we shall do this, first, upon the supposition that the two instruments are applied to geometric lines upon paper.
The reader will observe, that in this comparison the two instruments are supposed to be applied to geometric lines upon paper, and that this was the only purpose to which Bradley ever thought of applying his mirrors ; yet the kaleidoscope is in every respect a superior instrument, even for that inferior purpose, and gives true symmetrical forms, which the other instrument is incapable of doing.
In the comparison which has now been made, we have degraded the Kaleidoscope, by contrasting its effects with those which Bradley's instrument is capable of producing, for these effects are not worth the looking at. When we attempt to employ Bradley's instrument to produce the effects which have been so much admired in the kaleido scope, namely, to produce beautiful forms from transparent or opaque coloured objects ecilitained in a cell, and at the end of the reflectors, it fails so entirely, that no person has succeeded in the attempt It is, indeed, quite impossible to produce by it the beautiful and symmetrical forins which the kaleidoscope displays. Had this been possible, Dr. Brewster's patent might have been invaded with impunity by every person who chose to manufacture Bradley's in strument ; but this was never tried, and for the best of aft reasons, because nobody would have purchased it.
We trust that no person, who wishes to judge of this subject with candour, will form an opinion without having actually seen and used the instrument proposed by Bradley. Let any person take Bradley's plates, and, having set them at an angle of 30° or 221°, place them upon a cell contain ing fragments of coloured glass, he will infallibly find that he cannot produce a picture of any symmetry or beauty. The disunion of the sectors, the darkness of the last re flections, and the enormous deviation from symmetry, to wards the centre of the figure, will convince him, if he re quired conviction, that the instrument is entirely useless as a kaleidoscope. To those, however, who are not capa ble, either for want of knowledge, or want of time, to make such a comparison, we may present the opinion of three of the most eminent natural philosophers of the present day, viz. the celebrated Mr. Watt, Professor Playfair, and Pro fessor Pictet.