« ΠροηγούμενηΣυνέχεια »
above the transcendentalism of Kant; and that if the intellectual nature and moral attributes of man are ever again to be rendered intelligible, we must approach nearer to the earth, and take a more practical view of what the human being does, and feels, as an actual member of society. What becomes of the poor students during this random play of mental aërostation? Why, they gaze at the philosopher who is up for the time; and the farther he goes into the clouds they like him the better, and pass the the louder praises on his personal courage and the buoyancy of his machine: and when he comes down to let a younger aëronaut have his turn, they immediately forget his exploits, in admiration of the gas and silk which are about to darken the atmosphere, in a new voyage of discovery. It cannot be surprising, therefore, that we should agree with Hobbes, in the quotation given above, that among the things to be amended in universities, the frequency of insignificant speech is one!
We should not, however, do justice to Dr. Brown, did we omit to mention that there are in his lectures more ingenious reasoning, and a greater number of original views, than are to be found in any modern work with which we are acquainted. His various theories, even if they did occur to him for the first time during the period of composition, give proof of a very acute and penetrating mind: exciting, as we peruse them, a feeling of deep regret that he did not live to review his labours with the more cool and impartial eye of riper years, and prepare them for the press, not merely as discourses read to very young men, but with a more direct reference to the actual state of knowledge that obtains in the scientific world. A sketch of his system may be given in the following words. Confining the inquiries of philosophy to an examination of mental phenomena, as mere states of the mind, without attempting to unfold the nature of the thinking and feeling principle itself, he divides our intellectual and sensitive impressions into these classes and orders :
'Of these states or affections of mind, when we consider them in all their variety, there is one physical distinction that cannot fail to strike us. Some of them arise in consequence of the operation o external things-the others, in consequence of mere previous feelings of the mind itself.
"In this difference, then, of their antecedents, we have a ground of primary division. The phenomena may be arranged as of two classes, the external affections of the mind, the internal affections of the mind. The former of these classes admits of very easy subdivision, according to the bodily organs affected. The latter may be divided into two orders, intellectual states of the mind and emotions. These orders which are sufficiently distinct in themselves, exhaust, as it appears to me, the whole phenomena of the class."
This classification is, no doubt, both ingenious and satisfactory; being much more simple than the cumbrous enumeration of Reid, and sufficiently comprehensive to include all the powers and susceptibilities of the human mind. But many of the minor details are objectionable both in principle and language. The mind, for example, is identified throughout with its own operations: thought is represented as being merely the mind in a state of thinking; anger, love, and desire, are the mind in so many different states; and, in fact, the mind is described as consisting of its own ideas and feelings, and therefore incapable of existing but when it thinks and feels. It is a mere bundle or succession of ideas and emotions. We admit, indeed, that an attempt is made to obviate this objection; but it must be obvious to every one, that the language of the defence is inconsistent with the expression, as well as with the general tenour of the doctrines to which it refers.
There is perceptible, too, throughout the whole work, a tendency to find fault with Dr. Reid and his opinions, and to lower that distinguished writer as a philosopher and author. By means of a paltry kind of special pleading, an attempt is made to prove that his controversy with the idealists, Descartes, Locke, Berkeley, and Hume, originated in a mistaken view of their doctrines in regard to perception. No one who has made himself master of the metaphysical tenets which were held by those ingenious philosophers will agree with Dr. Brown; for it must be granted, either that the disciples of the Cartesian school did not understand their own language, and that the world ascribed to them a set of opinions which they never maintained, or that Reid's strictures on their system were just and well founded. But we find, moreover, that Dr. Reid was frequently attacked when Mr. Stewart's reasoning was the object of the lecturer's vituperation. letter to Mr. Erskine he confesses this ruse de guerre in the following terms: "I was very much constrained, as you may believe, by the unpleasantness of differing so essentially from Mr. Stewart, on many of the principal points. But I conceived that it would be more honourable to state at once my own opinions, than to seem to introduce them afterwards in other years; and Dr. Reid's name fortunately served every purpose when I had opinions to oppose, in which Mr. Stewart perhaps coincided. I got off therefore pretty well in that way; though I must confess that it was one of the most unpleasant circumstances attending my situation."
We must not forget to mention, that Dr. Brown composed six or eight volumes of poetry, written generally after the manner of Collins and Akenside; but which, with the exception of one piece, named the "Paradise of Coquettes," have not gained for their author the meed of praise. Mr. Erskine, in one of his letters
to him, very successfully points out the source of his failure, by stating that he "cut blocks with a razor." He was so nice about his words, that he allowed his thoughts to evaporate while searching for an expression. At all events, Dr. Brown's fame will not be supported by his poetical eminence.
Mr. Welsh concludes the "Life" with a highly wrought character of its subject, as a man, a poet, and a philosopher; but like many other unskilful eulogists he defeats his own end by saying too much, as also by inadvertently drawing aside the veil, and showing the original instead of the picture. For instance, after extolling Dr. Brown as the most amiable, and candid, and selfdenied, of human beings, he adds, as one of the shades to the brightness of his excellencies, a tendency to give too little credit to the motives of those who differed from him in sentiment"— one of the worst tendencies, it must be confessed, that can darken any character, whether literary or political. Again, after praising his philosophical style and talents in terms of the most unbounded admiration, he acknowledges "that Dr. Brown often shows a preference of what is subtle to what is useful, and is sometimes more ingenious than solid." He even applies to him the remark which Buonaparte made on La Place:-"Il cherchoit des subtilités partout; et portait enfin l'esprit des infiniment petits dans l'administration." "His style," he continues, "is too abstract, and his illustrations are not always introduced in the manner that might give them most effect. Many quaintnesses, both of thought and expression, are to be found in his writings. His sentences are often long, sometimes involved," &c. &c. Of these observations we have only to say, that if the author believed them well founded, he ought to have drawn his pen through the twenty pages of hyperbolical panegyric which immediately precede them. Let those, however, who wish to have a favourable specimen of Dr. Brown's talents and manner as a metaphysician, read with attention the "Inquiry into the Relation of Cause and Effect,"
ART. XIII.-I. Prof. Schumacker's Astronomische Abhandlungen, Altona, 1823. A Memoir on Refractive and Dispersive Powers, by M. Frauenhofer.
2. Transactions of the Royal Society of Edinburgh, Vol. IX. On a Monochromatic Lamp, &c., by Dr. Brewster.-On the Absorption of Light by coloured Media, by J. F. W. Herschel, Esq.
3. Some Account of the late M. Guinand and his Improvements in the Manufacture of Glass, 8vo. London, 1825.
M. FRAUENHOFER has been long known on the continent as a very distinguished practical optician. He has succeeded beyond any artist in this country in producing flint glass for optical purposes, of the most complete transparency, and freedom from flaws and defects. This superiority in his glass has enabled him to prosecute some very important researches, an account of which is contained in the memoir named at the head of this article, as inserted in French, in the well known journal of Prof. Schumacker.
His primary object was to determine with great exactness, for the formation of achromatic object glasses, the dispersive powers of different species of glass. He first tried the effect of correcting the colour by opposing prisms, viewed through a telescope, which is in fact the same method as that originally proposed by Dr. Brewster. But it became an object of attention to examine the dispersion of each coloured ray separately. To do this is a problem which has always been attended with the essential difficulty, of not being able to fix upon rays in the spectrum which are strictly homogeneous, and which can at all times be identified with certainty. In order to get over this difficulty M. Frauenhofer tried, without success, different coloured media and flames: to trials of this kind we shall have occasion to allude in the sequel, as leading to some important discoveries. Our artist, however, next adopted a plan which he considered successful; this was to place six lamps in a row behind a small aperture, close before which was a prism. The separate spectra of each lamp were thus thrown, so that the prism under trial, which was placed at nearly seven hundred feet distance, received only the red rays (for example) from one lamp, and the blue from another, &c., by which means the colours appeared in the form of distinct spaces, separated entirely from each other. We cannot help feeling some difficulty as to the application of this method, but perhaps the description itself is not the clearest that might be given. We do not feel sure that the rays were strictly homogeneous; however, they were capable of exact identification from this further contrivance: a narrow aperture was made in the screen above the six lamps, through which the light of another lamp passed and was received on the second prism; in viewing this, a bright line was seen at the limits of the red and yellow spaces; this was exactly defined, and by means of its invariable position, in comparison with the coloured spaces below, the observer could always be assured that the same identical ray fell on his prism. A number of measurements were thus made with great exactness, from which the great differences in the
ratios of refraction for the same ray in different media, are clearly ascertained.
But the most important point was the appearance of the bright line above mentioned; this M. Frauenhofer next proceeded to study; he found it exhibited alike by the light from all flames, &c. when received through a narrow aperture. He next tried the light of the sun; this was received into a dark room through a narrow crevice, at the distance of twenty-four feet, by a prism of excellent flint glass: in looking at the spectrum thus formed through a small telescope, he observed not only the bright line before spoken of, but an infinity of lines, some dark and some bright, crossing every part of the spectrum at right angles to the direction of its elongation, and not forming the boundaries of the different coloured spaces, but existing in the middle of them, and in fact distributed in some places more plentifully than in others along the whole length, in some parts more conspicuous, and in others more faint. Of all these lines the observer has given an accurate delineation; he counted upon the whole 574 of them; if the aperture be so wide as to subtend an angle of more than 15" at the eye, the lines disappear. Some of the fainter ones also are not seen, unless the eye be shaded from the glare of the brighter parts. With English flint glass, M. Frauenhofer could only see the brightest lines; but with every sort of glass of his own manufacture, and with prisms formed of liquids, they were all distinctly seen. He then proceeded by an extended series of measurements, with a repeating circle, to determine the angles of deviation which these lines formed when viewed through different media. These lines in fact supply the great desideratum in researches of this nature, and enabled him to determine the deviations belonging to points in the spectrum strictly definite, with any degree of accuracy.
From observing the great number of lines crossing the spectrum, we might be led to suppose that the inflexion of light at the edges of the aperture had some connection with the phenomenon; in order to examine this point, M. Frauenhofer varied the experiment in the following manner: He received the rays through a small circular hole nearly 15" in diameter; the spectrum thus formed had almost no breadth, but in order to widen it, M. Frauenhofer made the rays pass through a semi-cylinder of glass, by this means the length and order of colours remained unaltered, but the breadth being magnified, he saw as before all the lines. By means of the same contrivance he detected similar lines in the light of the planet Venus, without employing any aperture; the brightest lines only were visible, but they coincided in position with the corresponding ones in the solar spectrum. The light of some of the principal