. The microscope and its revelations. THE SUB-STAGE 189 has 40 threads to the inch, and works through an immovable fitting,the thread is discontinued at C, and from C to D a screw having 50threads to the inch is cut, working through a fitting E. If nowthe milled head F be rotated 40 times, the screw A C will havetravelled one inch. So will the screw C D as it is cut on the samestern, but it would take 50 revolutions of screw C D to travel oneinch through the fitting E, hence the fitting E must have beencarried up bodily the remaining 10 revolutions—that is to say, ith. PIG. 153.—Bakers fine ad
. The microscope and its revelations. THE SUB-STAGE 189 has 40 threads to the inch, and works through an immovable fitting,the thread is discontinued at C, and from C to D a screw having 50threads to the inch is cut, working through a fitting E. If nowthe milled head F be rotated 40 times, the screw A C will havetravelled one inch. So will the screw C D as it is cut on the samestern, but it would take 50 revolutions of screw C D to travel oneinch through the fitting E, hence the fitting E must have beencarried up bodily the remaining 10 revolutions—that is to say, ith. PIG. 153.—Bakers fine adjustment to sub-stage (1888). of an inch— therefore one revohition raises the fitting E -g-J-jjth of aninch. The fitting E is attached to the sub-stage G through a slot cut inthe cover of the adjustment; the cover is also grooved on either sideto receive that part of the sub-stage H which insures the truevertical movement so essential with this screw. It is almost a matter of compulsion to refer here to a com-paratively recent arrangement known as a stringing sub-stage, whichis, as its name implies, a sub-stage so arranged as to be capable of 190 THE HISTORY AND DEVELOPMENT OF THE MICEOSCOPE being moved Intertill;/ out of the :is in an arc which has the object onthe stage for its centre. The sole purpose of this is to secure oblique illumination, whichpractically, at the time the swinging sub-stage was devised, meantobtaining a more oblique pencil than the condensers then providedcould command : and since this also meant sending into the object p
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
