. The microscope and its revelations. -which the sub-stage is fixed, or an inclined plane actingin a slot in the same way. In fact, any simple device for focussingthe condenser more slowly than the rackwork will do, pushing thecondenser up to, or causing it to recede from, the under surface ofthe slide with sufficient delicacy. But no means should be employed 186 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE tor tins end which will imperil the absolute firmness of the sub-stage,or else more will be lost than can be gained. The need of such ai It-vice fur tin- most delicate and critical microsc
. The microscope and its revelations. -which the sub-stage is fixed, or an inclined plane actingin a slot in the same way. In fact, any simple device for focussingthe condenser more slowly than the rackwork will do, pushing thecondenser up to, or causing it to recede from, the under surface ofthe slide with sufficient delicacy. But no means should be employed 186 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE tor tins end which will imperil the absolute firmness of the sub-stage,or else more will be lost than can be gained. The need of such ai It-vice fur tin- most delicate and critical microscopical work is shownplainly by the fact that during the past few years several ingeniousand practical devices have been used, nearly every principal Eng-lish maker employing a method of his own. The first arrangement\vas made in Powell and Lealands sub-stage and is shown in fig. nature of this device, which was suggested by Mr. Nelson, willIn- readily understood. It does not interfere with the general BAUSCH8LOMB OPTICAL i IG. 14? sta^c with diaphragm in the plane of tlie stage. Topview and cross Motion showing of sta;; and of iris dia-phragm. mechanical arrangements of the sub-stage; it will be seen that the milled ||,.;M| A controls a MTC\\ .spindle terminating in a steel cone B. 1n rotating A. I, turns, and \\itli ,-i very slow motion forces up (or the case may l>e) a pinC. inserted in the plate E of Tlie iimt imi of ( cai-ries with it Hie condenser. At ;md foiming of K :,t the back an inner sliding sagainsl a spring a1 the upper end between bearings F at liieli are fixed upon the usual racked slide |) of the sub- THE SUB-STAGE I87 stage ; the inner sliding plate is the essential addition to the usualracked slide, in the application of the new fine adjustment to thesub-stage. The range of motion is about ^th in.—the difference inradius between the smaller and larger ends of the steel cone. A very simple an
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
