Monthly microscopical journal: transactions of the Royal Microscopical Society, and record of histological research at home and abroad . glass is taken from the focalpoint through which the rays must pass for all degrees. Thoseentering at other angles within the plane of focus will give a falseindication, from diffused light forming no image. If a conical nozzle, having a small aperture in its apex, isplaced over the front of an object-glass, the height of the conebeing equal to the focal length, all such false light will be excluded,and image-forming rays only will enter at angles of any exte
Monthly microscopical journal: transactions of the Royal Microscopical Society, and record of histological research at home and abroad . glass is taken from the focalpoint through which the rays must pass for all degrees. Thoseentering at other angles within the plane of focus will give a falseindication, from diffused light forming no image. If a conical nozzle, having a small aperture in its apex, isplaced over the front of an object-glass, the height of the conebeing equal to the focal length, all such false light will be excluded,and image-forming rays only will enter at angles of any extent. As there would be a difficulty in adapting such cones to everyobject-glass to be measured, an instrument has been contrived tomeet the requirements. The traverse is horizontal during themeasurement; therefore a vertical slit will serve instead of acircular stop. For high powers it is requisite that the metaledges of this slit should be exceedingly thin, and consequently mustbe secured from damage from contact with the object-glass orotherwise. The outer sides are required to be exactly in the focalplane during the The cuts, full size in plan and side views, illustrate the arrange-ment, a a is a plate of brass with a central square openingchamfered away beneath so as to clear 170^; h is a slip of glass Royal Microscopical Society. 199 sKding under two staples c c. At (Z is a spring for forcing theglass against the set-screw e. On the top surface of the glassthere is a strip of platinum foil, 001 thick, cemented on withCanada balsam. Fixed underneath the opposing staple there is asimilar piece of foil. By turning up the set-screw to a stop thestraight edges of the foils are brought in contact, and opened byreversing the screw. This instrument is placed on the stage of a microscope, withthe body horizontal and set on a wooden turn-table about ten inchesin diameter, having its edge divided into degrees. The object-glassto be measured is focussed on the glass surfa
Size: 2026px × 1233px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, bookpubli, booksubjectmicroscopy
