. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. OPAQUE OBJECTS. 197 the lens, D E; these rays, as also those shown by fig. Ill, will be brought into a focus, F, when the lens is placed as there represented; but if the flat side occupy the same position, then, according to fig. 112, it will be in the worst possible condition, as its spherical aberration will be the greatest. Fig. 125 represents this arrangement, the same letters being used as in the preceding figur
. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. OPAQUE OBJECTS. 197 the lens, D E; these rays, as also those shown by fig. Ill, will be brought into a focus, F, when the lens is placed as there represented; but if the flat side occupy the same position, then, according to fig. 112, it will be in the worst possible condition, as its spherical aberration will be the greatest. Fig. 125 represents this arrangement, the same letters being used as in the preceding figure. Here it will be seen that the. Fig. 125. rays nearest the margin of the lens, D E, will be'brought to a focus upon the object, a, but those nearer the centre will pass on to F, so that a will be only illuminated to about one- half the extent of a in the preceding figure. When, however, it is required to procure either parallel or diverging rays, so as to illuminate a large surface, such as the mirror or side reflector, the lens must then be placed very near the lamp with its flat side towards the light, as shown in fig. 126, and, according to the distance of the one from the other, so will the rays either be convergent, divergent, or even parallel. Should it be required to illuminate a large portion of an object for dissection, or for other purposes, then we may have recourse to the following plan: the large condenser must be placed near to the lamp, so that diverging rays given off from it may be so converged as to fill the entire circle of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Quekett, John, 1815-1861. London, H. Bailliere; [etc. , etc. ]
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