. The microscope and its revelations. ry suitable. the microscope in a horizontal position, and with a powerfulillumination, project the image of the stage micrometer on to a screendistant five feet, measured from the front lens of the object i\ e. If nophoto-micrographic camera is at hand, it will be necessary to performthe experiment in a darkened room, shading the illuminating the magnifying power thus obtained by (); the quotient willgive the initial power of the lens at ten inches to a very near approxi-mation. The reason why the result is not perfectly accurate is
. The microscope and its revelations. ry suitable. the microscope in a horizontal position, and with a powerfulillumination, project the image of the stage micrometer on to a screendistant five feet, measured from the front lens of the object i\ e. If nophoto-micrographic camera is at hand, it will be necessary to performthe experiment in a darkened room, shading the illuminating the magnifying power thus obtained by (); the quotient willgive the initial power of the lens at ten inches to a very near approxi-mation. The reason why the result is not perfectly accurate is that theten inches must be measured from the posterior principal focus ofthe lens, and that is a point which is not given. But in the case ofa power such as a ^, it is, in practice, found to be very near the frontlens of the objective. So by taking a long distance, such as five feet. 1 English Mechanic, vol. HM>. Article on measurements of magnifyingpower of microscope objectives, by E. M. Nekon. U 290 ACCESSORY APPARATUS. the error introduced by M small displacement of the posterior prin-cipal torn- de> lint materially amount to much. There is a further error introduced by the approximation of theobjective to the stage micrometer in order to focus the conjugate atMich a distance, but this i> small. We can see, therefore, that thiserror tend> to .-lightly increa>e the initial magnifying power. The initial power of the J beingfound, and its combined magnifyingpower, with a given eye-piece, beingknown, the combined power dividedli\ the initial power gives the multi-plying power of the eye-piece. Caremust be of course taken to notice thetube-length when the combined poweris measured. The initial power of anyother lens may be found by dividingthe combined power of that lens withthe eye-piece, whose multiplying powerhas been determined, by the multiplyingpower of that Nose-pieces.—The term nose-piece primarily means that part of a microscope int
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