Microscope

“ Within the last half-century the use of the microscope, not only as an instrument of scientific research, a tool in the hands of the investigator of the finer organisation of the world of nature, nor even as an adjunct to the apparatus of the chemist or the manufacturer, but as a means of innocent and instructive recreation, has become so firmly rooted amongst us that it seems hardly necessary to advocate its claims to attention on any of these grounds. ”

“ Having now explained the optical principles of the achromatic compound microscope, it remains only to describe the mechanical arrangements for giving those principles their full effect. The mechanism of a microscope is of much more importance than might be imagined by those who have not studied the subject. In the first place, steadiness, or freedom from vibration, and most particularly freedom from any vibrations which are not equally communicated to the object under examination, and to the lenses by which it is viewed, is a point of the utmost consequence. ”

“ The eye should be moved up and down from the eye-glass of a compound microscope, till you find that situation where the largest field, and most distinct view of the object is obtained; and as the sight differs very much in different persons, and even in the same person, we frequently find each eye to have a different sight from the other, particularly in those called myopes, or short-sighted, every one ought to adjust the microscope to his own eye, and not depend upon the situation in which it was placed by another. ”

“ Opposite to the microscope, and about a foot away from it, is a lamp with the edge of the flame presented to the microscope, the concave mirror of which is so arranged as to receive the rays from the flame and direct them up the tube of the microscope. Upon the stage is placed a piece of ground-glass, and the mirror-arm is now to be moved up or down upon its support until the ground-glass receives the maximum of illumination, which it will do when the lamp-flame is at one conjugate focus of the mirror and the ground-glass at the other. ”

“ In the ordinary compound microscope, it is only possible for one person to see the object to be examined at once; for popular exhibitions of microscopic objects the reflecting microscope has been devised, by means of which the images of the objects to be looked at are thrown upon a screen. ”

“ Even after the improvement of the simple microscope by the use of doublets and triplets, the long course of the rays, and the large angular pencil required in the compound instrument, deterred the most sanguine from anticipating the period when they should be conducted through such a path free both from spherical and chromatic errors. Within twenty years of the present period, philosophers of no less eminence than M. Blot and Dr. Wollaston predicted that the compound would never rival the simple microscope, and that the idea of achromatizing its object-glass was hopeless. ”

“ As the far greater part of the objects which surround us are opake, and very few sufficiently transparent to be examined by the common microscopes, an instrument that could be readily applied to the examination of opake objects, has always been a desideratum. Even in the examination of transparent objects, many of the fine and more curious portions are lost, and drowned as it were in the light which must be transmitted through them; while different parts of the same object appear only as dark lines or spots, because they are so opake, as not to permit any light to pass through them. ”

“ It may be taken as an axiom with microscopists that “neither the penetrating power nor the high-power defining objective is alone sufficient for every kind of work. The larger the details of ultimate structure, the narrower the aperture—and the converse; the minuter the dimensions of elementary structure, the wider must be the aperture of the objective.” Every worker with the microscope must have satisfied himself of the truth of this statement, when engaged in the study of the movements of living organisms, or defining the intimate structure of the minuter diatoms, or of the podura scale. ”

“ In the compound microscope the initial image, formed by the object-glass, is further magnified by another set of lenses, forming the eye-piece, by which the diverging rays of the virtual image are brought together to a focus at the eye-point; and when viewed directly, the eye sees an imaginary image, as in a simple microscope, whilst, when the rays are allowed to fall upon a screen, they form a real image of the object, larger or smaller, as the screen is farther from or nearer to the eye-point. ”

“ Microscopes are either single or double. In the former case, but one lens is used, and through this the object is viewed directly; but, in the latter case, two or more glasses are employed, through one of which a magnified image is thrown upon a reflecting surface, and this is viewed through the other glass, or glasses, as the real object is seen through a single microscope.
21. The solar microscope, on account of its great magnifying powers, is the most wonderful instrument of this kind. The principles of its construction are the same with those of the camera obscura. ”

“ Let us describe a more refined compound microscope than the one we constructed in our darkened room. The optical parts, that is to say the lenses, are the most important parts of every microscope, upon their qualities depend the degree of efficiency of the instrument; the metal portions, known collectively as the stand, contribute to the easier, smoother working of the microscope. ”

“ In neither of those two ways do microscopes contribute to the improvement of sight. For, when we look through a microscope, we neither see more visible points, nor are the collateral points more distinct, than when we look with the naked eye at objects placed at a due distance. A microscope brings us, as it were, into a new world. ”

“ When to all these considerations we add that the manipulation of the microscope, for the purpose of ordinary observation, may be acquired without much difficulty, and that the instrument itself may be procured at a moderate cost, we have said enough to justify the assertion that every educated person ought to possess a microscope, even as he possesses a collection of books. ”

“ Objects through which you can see light are called "transparent," and are the easiest to look at with the microscope, because you can lay them on a glass slide and throw light up through them with your mirror. Thick objects through which light cannot pass are called "opaque," and are more difficult to examine, and can only be seen with low powers and a bright light. ”

“ The lucernal microscope does not in the least fatigue the eye; the object appears like nature itself, giving ease to the sight, and pleasure to the mind: there is also in the use of this instrument, no occasion to shut that eye which is not directed to the object. ”

“ The common solar microscope does not shew the surface of any object, whereas the opake solar microscope not only magnifies the object, but exhibits on a screen an expanded picture of its surface, with all its colours, in a most beautiful manner. ”

“ The first is that if the light upon the paper be stronger than that in the apparent field of the microscope, the image will not be well seen, or if the paper be too feebly lighted, it will be difficult to keep the point of the pencil in view. The light from the microscope is thrown into the eye, and the view of the image upon the paper is the effect of a mental act, the eye looking out in the direction from which the rays appear to come. ”

“ THE USE OF THE MICROSCOPE IN MANUFACTURES In how many branches of commerce, we wonder, does the microscope play its part. It is used in several departments of engineering for examining steels and many other metals not only for defects but to see how they are made up. ”

“ In many species the markings are so extremely minute that they can only be made out with the highest powers of the microscope and the most careful illumination, so that they serve as test objects whereby the performance of a microscope can be judged by a practical man. ”

“ There are three features of this ingenious apparatus which cannot fail to commend themselves equally to the casual worker and the serious microscopist. All objects are seen erect, just as the eye sees them. This is brought about because, as in the case of the super-microscope, we really observe a magnified, inverted image of our object, formed at the spot where the object would be placed were we using an ordinary microscope. ”

“ Microscope, being the Army pattern as well as the student’s, is well adapted for clinical work. A firm tripod stand supports two dark bronze uprights, with rack and pinion coarse adjustment, e, and fine adjustment, d, the stage, i, is wide and suitable for clinical work, and large enough for dissecting upon. The whole instrument is well made; the coarse adjustment is so good that the one-eighth inch can be focussed with ease, and without using the fine adjustment. ”

“ The obliquity which a prism gives to the visual rays when the microscope is used in the erect position, as for dissecting, is an advantage, as it brings the image to the eye at an angle very nearly corresponding to that of the inclined position in which the microscope is ordinarily used. ”

“ A microscope is of some assistance, but nothing like sufficient: no microscope, however powerful, can show us an atom, still less can it show us how an atom is composed and how far apart its ultimate particles are: we know this otherwise and indirectly. ”

“ Apart from any other consideration, the super microscope marks a big advance from the fact that it possesses great “depth of focus.” It is possible, for example, with this remarkable instrument to examine a moss as it grows, with a high magnification and see not a portion of a leaf or a fragment of the stalk, as with the ordinary microscope, but the whole upstanding plant, in stereoscopic relief. It shows us objects exactly as we should see them were we endowed with super eyes, enormously enlarged, [242] in relief and erect. ”

“ By the term simple microscope is meant one in which the object is viewed directly through a lens or combination of lenses, just as we have supposed an arrow or an insect to be viewed through a glass held in the hand. ”

“ No man will ever see all that the microscope can show him, each day some fresh wonder is looked upon for the first time.
As a hobby, microscopy can hardly be excelled. It is a sensible hobby and, after the initial outlay, need cost us but a few pence each year. We hear someone say that he prefers an outdoor hobby, but surely the microscope, if used intelligently, will take [308] us out of doors. The search for specimens is one of the attractions of microscopy. As an instrument for the serious worker the microscope compares favourably with any other invention of mankind. ”

“ The microscope is to remain as before: the upper part f g r s of the opake stage must be removed, and the stage for transparent objects, represented at Fig. 4, put in its place; the end, Fig. 9 and 10, to be next the lamp.
Place the rough glass in its groove at the end A B, and the objects in the slider-holder at the front of the stage; then transmit [75] as strong a light as you are able on the object, which you will easily do, by raising or lowering the lamp. ”

“ In testing for poisons the microscope is invaluable. Frequently only the most minute traces of the poison occur in the system and the modern microscopist who makes a study of poisons and their [250] detection can solve mysteries which would have baffled all the scientists in the world in days gone by.
Our chemical studies with the microscope may well begin with various common crystals; they are usually easy to prepare; the process of crystallization is always interesting to watch, and as objects for the microscope it would be difficult to find anything more beautiful than these home-made gems. ”

“ A microscope objective being made in essentially the same Way as a simple microscope, and the front focus of the compound system being situated before the front focus of the objective, the magnification due to the simple system makes the free object distance greater than that obtained with a simple microscope of equal magnification. ”

“ The form of instrument upon which the optician has expended a greater amount of skill than perhaps on any other is the Bacteriological Microscope, as may be inferred from the larger space I have devoted to this important adjunct, since by original research, there can be no doubt a still greater future is in store for science in this special department of microscopy. ”

“ Thus, soon after the invention of the microscope, the field it presented to observation was cultivated by men of the first rank in science, who enriched almost every branch of natural history by the discoveries they made with this instrument: there is indeed scarce any object so inconsiderable, that has not something to invite the curious eye to examine it ”

“ Beck’s Star Microscope is in every sense a students’ or class-room instrument. It is firm and well made, with joint for inclination, large square stage, sliding coarse adjustment and fine adjustment by micrometer screw, draw-tube, iris diaphragm, double mirror on swinging crank arm, A or B eye-piece, a one-inch and quarter-inch objective, the magnifying power of which ranges from 38·5 to 183. ”

“ If the slide is held between the finger and thumb of one hand and moved from side to side, while the other hand is working the fine adjustment, there can be no danger of injuring either the objective or the specimen. Before putting the microscope away, take a fine camel-hair brush dipped in ether, alcohol, or methylated spirit, and carefully remove the oil from the objective and the glass cover of the object; a soft chamois leather or cambric pocket handkerchief will dry it off, or a piece of fine white blotting paper answers equally well. ”