. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. ILLUSTKATOES. 205 on the last one, D, by means of the lever, F. The illuminator itself consists of a portion of a large thick lens, such as that represented by G, as being cut off from H. In order to explain its action the course of three rays of light, ah c, is represented: these rays, on reaching the first surface, are ren- dered slightly convergent; on meeting with the plane surface they are reflected at right ang
. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. ILLUSTKATOES. 205 on the last one, D, by means of the lever, F. The illuminator itself consists of a portion of a large thick lens, such as that represented by G, as being cut off from H. In order to explain its action the course of three rays of light, ah c, is represented: these rays, on reaching the first surface, are ren- dered slightly convergent; on meeting with the plane surface they are reflected at right angles, as indicated by a' V d; and on passing through the convex surface G they are converged into a focus at I. When in use the illuminator is placed imme- diately below the stage, and the light incident on one convex surface is converged on the object by the other, and by turning, the handle, F, various degrees of obliquity may be obtained; it may also be employed as a substitute for the buU's eye condenser to iQuminate opaque objects on the stage: in this case the position of the reflecting surfaces must be the reverse of that indicated in the figure—in other words, the plane surface must be uppermost. Annular Condenser.—In order to take advantage of the reflection from the internal surface of glass Mr. Shadbolt has contrived the instrument represented by fig. 134, which he terms the annular condenser; it consists of an annular prism. Fig. 134. or ring of glass, which, if divided vertically, would be repre^ sented by a in No. 1, fig. 134, the two upper planes being inclined towards each other according to the obliquity of the. 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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