David Brewster

“ Such were the last days of Sir Isaac Newton, and such the last laurels which were shed over his grave. A century of discoveries has since his day been added to science; but brilliant as these discoveries are, they have not obliterated the minutest of his labours, and have served only to brighten the halo which encircles his name. The achievements of genius, like the source from which they spring, are indestructible. Acts of legislation and deeds of war may confer a high celebrity, but the reputation which they bring is only local and transient ”

“ It may nevertheless be, that he is the unconscious 293victim of an invincible love of paradox; and indeed Sir David Brewster unceremoniously characterises the Essayist’s conjectures concerning the fixed stars as “insulting to Astronomy,” and “ascribable only to some morbid condition of the mental powers, which feeds upon paradox, and delights in doing violence to sentiments deeply cherished, and to opinions universally believed;” [18] that having once conceived what he regards as a happy idea on a great question, he dwells upon it with such an eager fondness as warps his judgment ”

“ If, in place of disavowing the laws of Nature, and surrendering in his own person the intellectual dignity of his species, he had boldly asserted the truth of his opinions, and confided his character to posterity, and his cause to an all-ruling Providence, he would have strung up the hair-suspended sabre, and disarmed for ever the hostility which threatened to overwhelm him. The philosopher, however, was supported only by philosophy ”

“ December 28, 1550.
[24] “Le fait est,” says the Abbé Moigno, “que le stéréoscope par réflexion était presque complètement oublié, lorsque Sir David Brewster construisit son stéréoscope par refraction que nous allons décrire.”—Cosmos, vol. i. p. ”

“ No injudicious guardian controlled his ruling passion, and no ungenial studies or professional toils interrupted the continuity of his pursuits. His discoveries were, therefore, the fruit of persevering and unbroken study; and he himself declared, that whatever service he had done to the public was not owing to any extraordinary sagacity, but solely to industry and patient thought.
Initiated early into the abstractions of geometry, he was deeply imbued with her cautious spirit; and if his acquisitions were not made with the rapidity of intuition, they were at least firmly secured ”

“ In addition to the various works of Brewster already noticed, the following may be mentioned:—Notes and Introduction to Carlyle’s translation of Legendre’s Elements of Geometry (1824) ; Treatise on Optics (1831) ; Letters on Natural Magic, addressed to Sir Walter Scott (1831) ; The Martyrs of Science, or the Lives of Galileo, Tycho Brahe, and Kepler (1841) ; More Worlds than One (1854) .
See The Home Life of Sir David Brewster, by his daughter Mrs Gordon. ”

“ Darwin written a work on the change of species, as determined by observation and experiment, without any other object but that of advancing natural science, he would have obtained a high place among philosophical naturalists. But after reading his work in which the name of the Creator is never distinctly mentioned, we can hardly believe that scientific truth was the only object the author had in view. Researches, conducted under the influence of other motives, are not likely to stand the test of a rigorous scrutiny; and some of Mr. ”

“ What business is it of yours how I spend my time? I am answerable to Tom Curtis, not to you. Here is your friend, Mr. Bolling, sneaking behind you on the same errand; and I suppose you both think you are gentlemen," he sneered.
"Oh, come, Brewster," interrupted Jack Bolling apologetically, "I suppose Harry and I were overdoing things a bit to come over here after you. But there is no use getting so all-fired angry. If you are not up to mischief, why do you care if we do happen to come up with you?"
"Because I care to keep my own business to myself," answered David. ”

“ If the eye is placed so obliquely to the looking-glass, that the hand no longer interferes with its image, it will still be seen, that parts of the hand which are not directly visible, are visible in its reflected image, and therefore that a symmetrical picture cannot be created by the union of two parts apparently dissimilar. If the eye of the observer is placed near his hand, so that he can see distinctly both the hand and its image, the angular magnitude of his hand is much greater than that of its image; and therefore, when the two are united, they cannot form a symmetrical object. ”

“ If the pictures are refracted too little, or if they are refracted too much, so as not to be united, their tendency to unite is so great, that they are soon brought together by the increased or diminished convergency of the optic axes, and the stereoscopic effect is produced. Whenever two pictures are seen, no relief is visible; when only one picture is distinctly seen, the relief must be complete.
In the preceding diagram we have not shewn the refraction at the second surface of the lenses, nor the parallelism of the rays when they enter the eye,—facts well known in elementary optics. ”

“ In former times, the minute and accurate delineation of nature was a task almost impossible, requiring an amount of toil which could hardly be repaid even when slightly performed; but science has now furnished art with the most perfect means of arresting, in their most delicate forms, every object, however minute, that can enter into the composition of a picture. These means are the arts of photography and stereoscopic re-combination, when rightly directed, and it is the object of the present chapter to shew how the artist may best avail himself of their valuable and indispensable aid. ”

“ In illustrating the views of Galen on the dissimilarity of the three pictures which are requisite in binocular vision, he employs a much more distinct diagram than that which is given by the Greek physician. “Let a,” he says, “be the pupil of the right eye, b that of the left, and dc the body to be seen. When we look at the object with both eyes we see dc, while with the left eye we see ef, and with the right eye gh. But if it is seen with one eye, it will be seen otherwise, for when the left eye b is shut, the body cd, on the left side, will be seen in hg ”

“ In transmitting this letter to Leibnitz, the Abbé Conti informed him that he himself had read with great attention, and without the least prejudice, the Commercium Epistolicum, and the little piece70 that contains the extract; that he had also seen at the Royal Society the original papers of the Commercium Epistolicum, and some other original pieces relating to it. “From all this,” says he, “I infer, that, if all the digressions are cut off, the only point is, whether Sir Isaac Newton had the method of fluxions or infinitesimals before you, or whether you had it before him. ”

“ Although it is possible for a clever artist to take two portraits, the one as seen by his right, and the other as seen by his left eye, yet, owing to the impossibility of fixing the sitter, it would be a very difficult task. A bust or statue would be more easily taken by fixing two apertures 21⁄2 inches distant, as the two points of sight, but even in this case the result would be imperfect. The photographic camera is the only means by which living persons and statues can be represented by means of two plane pictures to be combined by the stereoscope ”

“ There is no fact in the history of science more singular than that Newton should have believed that all bodies produced spectra of equal length, or separated the red and violet rays to equal distances when the refraction of the mean rays was the same. This opinion, unsupported by experiments, and not even sanctioned by any theoretical views, seems to have been impressed upon his mind with all the force of an axiom.16 Even the shortness of the spectrum observed by Lucas did not rouse him to further inquiry ”

“ In this state a very perfect pattern will be created by the instrument, and the blue, green, and yellow colour will predominate according as a greater or a lesser portion of these colours happens to be opposite to the angular aperture. By shifting the position of the Kaleidoscope, any one of the colours may be made to predominate at pleasure; and the artist has it thus in his power, not only to produce any kind of outline that he chooses, but regulate the masses of colour by which it is to be filled up ”

“ Such being the nature of single portraits, we may form some notion of the effect produced by combining dissimilar ones in the stereoscope, so as to represent the original in relief. The single pictures themselves, including binocular and multocular representations of the individual, must, when combined, exhibit a very imperfect portrait in relief,—so imperfect, indeed, that the artist is obliged to take his two pictures from points of sight different from the correct points, in order to produce the least disagreeable result. ”

“ In the propositions respecting the multiplication of the sectors, the eye of the observer is never once mentioned; and the proposition is true, if the eye has an infinite number of positions; whereas, in the Kaleidoscope, the eye can only have one position. In the other proposition (Prop. xvii.) respecting the progress of the rays, the eye and the object are actually stated to be placed between the reflectors ”

“ The sitter may sometimes contribute his share to the hideousness of his portrait by involuntary nervous motion, but it is upon the artist or his art that the blame must be laid. [Pg 136]
If the single portrait of an individual is a misrepresentation of his form and expression, the combination of two such pictures into a solid must be more hideous still, not merely because the error in form and expression is retained or doubled, but because the source of error in the single portrait is incompatible with the application of the stereoscopic principle in giving relief to the plane pictures. ”

“ A very disagreeable effect is produced by bringing the darkest sectors, or those formed by the greatest number of reflexions, to the upper part of the circular field, and though the variety of patterns will be very great, yet the instrument is limited to the same series of fragments, and cannot be applied to the numerous objects which are perpetually presenting themselves to our notice. These evils can be removed only by adopting the construction shown in Fig. 22, in which the reflectors reach the [Pg 64] very end of the tube. ”

“ In a room where the paper-hangings have a small pattern, a short-sighted person might very readily turn his eyes on the wall when their axes converged to some point between him and the wall, which would unite one pair of the similar images, and in this case he would see the wall nearer him than the real wall, and moving with the motion of his head. In like manner a long-sighted person, with his optical axes converged to a point beyond the wall, might see an image of the wall more distant, and moving with the motion of his head ”

“ The ambition of fame is a youthful passion, which is softened, if not subdued, by age. Success diminishes its ardour, and early pre-eminence often extinguishes it. Before the middle period of life Newton was invested with all the insignia of immortality; but endowed with a native humility of mind, and animated with those hopes which teach us to form an humble estimate of human greatness, he was satisfied with the laurels which he had won, and he sought only to perfect and complete his labours. His mind was principally bent on the improvement of the Principia ”

“ When the inclination of the mirrors is not an aliquot part of 360°, the images formed by the last reflexions do not join like every other pair of images, and therefore the picture which is created must be imperfect. It has already been shown at the end of Chap. I. that when the angle of the mirrors becomes greater than an even or less than an [Pg 25] odd aliquot part of a circle, each of the two incomplete sectors which form the last sector becomes greater or less than half a sector. ”

“ The extension of the instrument to distant objects is not the only advantage which is derived from the use of the lens. As the position for giving perfect symmetry is rather within the extremities of the [Pg 87] reflectors than without them; and as it is impossible to place movable objects within the reflectors, we are compelled to admit a small error, arising principally from the thickness of the objects, and from the thickness of the plate of glass which is necessarily interposed between the objects and the reflectors. The compound Kaleidoscope, however, is entirely free from this defect. ”

“ The various phenomena of inflection, which had105 so long resisted every effort to generalize them, having thus received so beautiful and satisfactory an explanation from the undulatory doctrine, they must of course be regarded as affording to that doctrine the most powerful support, while the Newtonian hypothesis of the materiality of light is proportionally thrown into the shade. It is impossible, indeed, even for national partiality to consider the views of Newton as furnishing any explanation of the facts discovered by Fresnel ”

“ Anxious as we should have been to have awarded to Scotland the honour of having first adopted the Newtonian philosophy, yet a regard for historical truth compels us to take a different view of the subject. It is well known that Sir Isaac Newton delivered lectures on his own philosophy from the Lucasian chair before the publication of the Principia; and in the very page of Whiston’s life quoted by Professor Playfair, he informs us that he had heard him read such lectures in the public schools,164 though at that time he did not at all understand them. ”