The microscope and its revelations . de to revolve. A very convenient mode of elfectingthis, is to mount the selenite plate in a revolving collar,which fits into the upper end (a) of the tube (Fig. 41, b)that receives the polarizing prism. In order to obtain thegreatest variety of coloration with different objects, films ofselenite of different thicknesses should be employed; andthis may be accomplished by substituting one for anotherin the revolving collar. A stiU greater variety may beobtained by mounting thi-ee films, which separately give threedifferent colours, in a frame resembling that
The microscope and its revelations . de to revolve. A very convenient mode of elfectingthis, is to mount the selenite plate in a revolving collar,which fits into the upper end (a) of the tube (Fig. 41, b)that receives the polarizing prism. In order to obtain thegreatest variety of coloration with different objects, films ofselenite of different thicknesses should be employed; andthis may be accomplished by substituting one for anotherin the revolving collar. A stiU greater variety may beobtained by mounting thi-ee films, which separately give threedifferent colours, in a frame resembling that in which hand-magnifiers are usually mounted, so that they may be usedsingly or in double or triple combinations; as many asthirteen different tints may thus be obtained; but the advan-tage of revolution is sacrificed.—When the construction ofthe microscope does not readily admit of the connection ofthe selenite plate with the polarizing prism, it is convenientto make use of a plate of brass (Fig. 13) somewhat larger than Fig. Selenite Object-carrier. the glass sKdes in which objects are ordinarily mounted, witha ledge near one edge for the slide to rest-against, and a largecucular aperture into which a glass is fitted, having a film ofselenite cemented to it; this selenite stage or object-carrierbeing laid upon the stage of the microscope, and the slidecontaining the object being placed upon it, the effect of theselenite is obtained, as in the previous arrangement; and byan ingenious modification contrived by Dr. Leeson, the ringinto which the selenite plate is fitted being made movable,one plate may be substituted for another, whilst rotation maybe given to the ring by means of a tangent-screw fitted iatothe brass-plate. Such a selemte stage answers every pui- 138 ACCESSORY APPARATUS. pose that can be required; but as there is no provision forusing two or three plates in combination, it is necessary tohave a distinct selenite-plate for every modification of coloursthat
Size: 2576px × 970px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
