File:The microscope and its revelations (1901) (14786859893).jpg

Identifier: microscopeitsrev00carp (find matches)
Title: The microscope and its revelations
Year: 1901 (1900s)
Authors: Carpenter, William Benjamin, 1813-1885 Dallinger, W. H. (William Henry), 1842-1909
Subjects: Microscopy Microscopes Natural history
Publisher: Philadelphia, P. Blackiston's Sons and Co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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nd, theindex finger should rest lightly on the edge of the slip, and thethumb be so placed as to graze the objective as it advances towardsthe slip. The touch of the thumb indicates whether the objectiveis an inch oft or only a quarter of an inch away from the cover ofthe slip. The movement of the coarse adjustment may be rapid upto ^th or ;-th of an inch, but after this there must be a cautious butsteady advance. The body may be racked down until by gentleupward movement the slip is found to touch the front of the objective ;then proceed cautiously by delicately lifting the slip from time totime, by doing which we can proceed in perfect safety until the focusof the object is obtained. In this way focussing becomes easy andrapid, a matter of touch, and not of discontinuous procedure to discover where the front of the lens is—a search requiring a handglass and often, with its cumbrousness, considerable loss of time.The above simple plan with brief practice will enable the operator to
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• M :. - band (1895). THE MECHANICAL STAGE 179 focus an object in the field with a J-r-inch objective in ten ortwelve seconds. If a perfect mechanical stage cannot be obtained, take no middlecourse, have a,form, well-made plain one with a smoothly sliding ledge..The stage should be large, and the ledge should glide with perfectease and without catching when gently pushed from one corner. Forthis purpose the side-guides should be long, and only the ends of thebar should bear on the stage. The aperture should be as in themechanic-id stage, and for the same reason. Mi1. JSTelson suggested a stage of large size, which should have aIT? or If inch aperture bored in it, and then have the interveningbrass between it and the front taken away, so that the stageassumes a horse-shoe form. This is thoroughly efficient, and theprinciple is seen in fig. 134. It is a matter of great interest to English microscopists to notethat their German collaborateurs in Germany and the leadingGerman makers hav

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