SIR. DAVID BREWSTER ON NATURAL 1.1.4,Gie. Tuts copious little volume
is fully entitled to the epithets of, cu- rious and interesting, so often unduly lavished upon. worM that have but slender pretensions of the kind. Natural Magic is a description and explanation of the prodigies of the material world. However surprising and astonishing many of the phenomena of .Natural Magic, they are all produced by an arrangement of natural causes, in the skilful hands of the optician, the mechanist, or the chemist. Dr. BREWSTER has classed these phenomena, enumerated the most remarkable instances, and en- tered into an explanatory discussion of the theory of their construc- tion. He has gone through the subject with that ease and mastery which nothing can give but long familiarity with kindred topics, a clear head, and a habit of elucidation. The book is a perfect trea- sure to youth : it will not merely feed the curiosity with surprises, but so conduct the intelligence into an examination of their prin- ciple, as to act in the place of mental discipline. The information communicated at the same time respecting nature and her secrets is abundant. In conducting the education of youth, we are not friendly to a multiplicity of books ; but of those we did select, Natural Magic should be one, and that among the choicest. It will form the very gate of science: all will study (not read it) with pleasure, and they of a mechanical genius will assuredly turn it to account : this book is one that may become the source and parent of a young man's reflections through life, and perhaps decide his fortunes in it.
The Letters are thirteen in number. The first contains a general view of the subject, and refers to the occult sciences of the an- cients, and the means employed by the ancient magicians to esta- blish their authority. The second letter takes up the optical branch of the subject, and gees through the delusions dependent on the construction and condition of the organ. The third enters Upon spectral illusions, and contains many very curious particu- lars, and some ingenious general views of the subject. In the fourth, a very interesting letter, "Science used as an in- strument of imposture" is discussed. Here we have the decep- tions with plane and concave mirrors—necromancy—phantasma- goric exhibitions—KIRCHER'S mysterious writing on the wall, &c. The fifth letter embraces optical illusions of a miscellaneous cha- racter, such as the method of reading inscriptions on coins in the dark. In this letter, too, the curious subject of the apparent mo- tion of the eyes in a portrait is discussed; and the remarkable observation of WOLLASTON, that the same eyes look different ways with different features, is experimentally shown by sketching a piece of paper, on which is drawn another set of features stitched in, so as to lay over the lower part of the face and fit to the upper part.
The sixth letter describes such natural phenomena as are marked with the marvellous—aerial spectres seen in Cumberland —Fate Morgana, and the appearance of Dover as seen from Rams- gate thmitgit the hill on which it stands, by Professor VINCE. We are sorry not to find in this chapter a mention cf the extraor- dinary phenomenon which characterizes the Isle of France, where there is an individual who from the top of an observatory foretels the approach of ships to the island several days before their arrival, by detecting sone phenomenon in the sky. This is assuredly mar- vellous enough. St. PIERRE mentions the fact, and we have heard of it from other quarters. The art is confined, we believe, to one family, the members of which succeed each other in the post.
The seventh, eighth, and ninth letters, relating to illusions de- pendent on the ear and the power of sound,—such as ventrilo- quism, echoes, music, and the theory of vibrations,—are in the very highest degree interesting. Here is contained the description of VAUCANSON'S automaton flute-player, the invisible girl, KEMPE- LEN'S talking machine, and many other we may say wonderful mechanical contrivances.
Letter tenth introduces us to feats of strength. This is (and indeed all the letters are) illustrated by very clever wood-cuts. One feat dependent not on strength, but upon some strange sym- pathy and connexion in human nature, Dr. BREWSTER does not explain; and for our parts, we are completely puzzled by it. It strikes us, amidst a host of wonders, to be the most marvellous of all— One of the most remarkable and inexplicable experiments relative to the strength of the human frame, which you have yourself (Sir Walter Scott] seen and admired, is that in which a heavy man is raised with the greatest facility, when he is lifted up the instant that his own lungs and those of the persons who raise him are inflated with air. This experiment was, I believe, first shown in England a few years ago by Major H., who saw it performed in a large party at Venice under the direction of an officer of the American Navy. As Major H. performed it more than once in my presence, I shall describe as nearly as possible the method which he prescribed. The heaviest person in the party lies down upon two chairs, his legs being supported by the one and his back by the other. Four persons, one at each leg and one at each shoulder, then try to raise him ; and they find his dead weight to be very i great, from the difficulty they experience in supporting him. When he is replaced n the chair' each of the four persons takes hold of the body as before, and the person to he lifted gives two signals by clapping his hands. At the first signal, he himself and the four lifters begin to draw a long and full breath ; and when the inhalation is completed, or the lungs filled, the second signal is given, for raising the person from the chair. To his own surprise and that of his bearers, he rises with the greatest facility, as if he were no 'heavier than a feather. On several occasions I have observed, that when one of the bearers performs his part ill, by making the inhalation out of time, the part of the body which he tries to raise is left as it were behind. As you have repeatetlly seen this experiment, and have performed the part both of the load and of the bearer, you can testify how remarkable the effects appear to all parties, and how complete is the conviction, either that the load has been lightened, or the bearer strengthened, by the prescribed process.
At Venice, the experiment was performed in a much more imposing manner. The heaviest man in the party was raised and sustained upon the points of the fore-fingers of six persons. Major H. declared that the experiment would not succeed if the person lifted were placed upon a board, and the strength of the individuals applied to the board. Be conceived it necessary that the bearers should communicate directly with the body to be raised. I have not had an
opportunity of making any experiments relative to these curious facts; but whether the general effect is an illusion, or the result of known or of niw prin- ciples, the subject merits a careful investigation.
The eleventh letter describes the most remarkable automata, both ancient and modern. The philosopher begins with DrEns.nie and ends with BABBAGE. Every article in this division is strik- ingly curious; and not the least so is the automaton chess-player, the secret of which has never been disclosed, though it may be said to have been discovered. Besides which, there is VAUCAN- sorr's automaton duck, which both ate and digested its food.
The automaton of Degennes probably suggested to M. Vaucanson the idea of constructing his celebrated duck, which excited so much interest throughout Europe, and which was perhaps the most wonderful piece of mechanism that was ever made. Vaucanson's duck exactly resembled the living animal in size and appearance. It executed accurately all its movements and gestures • it ate and drank with avidity, performed all the quick motions of the head and throat which are peculiar to the living animal, and like it, it muddled the water which it drank with its bill. It produced also the sound of quacking in the most natural manner. In the anatomical structure of the duck, the artist exhibited the highest skill. Every bone in the real duck had its representative in the auto- maton, and its wings were anatomically exact. Every cavity, apophysis, and curvature was imitated, and each bone executed its proper movements. When corn was thrown down before it, the duck stretched out its neck to pick it up; it swallowed it, digested it, and discharged it in a digested condition. The process of digestion was effected by chemical solution, and not by trituration, and the food digested in the stomach was conveyed away by tubes to the place Of its discharge.
Sir DAVID observes, that this and several other automata sink into insignificance when compared with the automaton chess- player. We cannot agree with him, if it be true, as he believes, that the really remarkable part of the automaton Turk's duties were performed by a man placed in his interior. Letters twelfth and thirteenth describe the wonders of chemis- try, and are of course not the least wonderful of the whole. 0116 of the most novel and curious branches of them is "the vapour ca- vities in minerals," in which Sir DAVID BREWSTER details some remarkable discoveries of his own.
We hardly need repeat our recommendation of the work.
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