. The microscope and its revelations. of those who work with high 304 ACCESSORY APPARATUS power>. for we know of no similar instrument that yields so large a• solid cone- of illumination. The construction is an unusual one,the corrections for both spherical and chromatic aberrations beingeffected bv means f a cemented triple back lens, as is shown in theillustration of tin-optical system in fig. 244. The only flint glassused in it is the middle of the triple back. The total numericalaperture is I.!.!, the aplanatie aperture being in excess of magnifying power is ] inch, and the clea
. The microscope and its revelations. of those who work with high 304 ACCESSORY APPARATUS power>. for we know of no similar instrument that yields so large a• solid cone- of illumination. The construction is an unusual one,the corrections for both spherical and chromatic aberrations beingeffected bv means f a cemented triple back lens, as is shown in theillustration of tin-optical system in fig. 244. The only flint glassused in it is the middle of the triple back. The total numericalaperture is I.!.!, the aplanatie aperture being in excess of magnifying power is ] inch, and the clear aperture at the backof the lens is ,^ths inch, and it works through a slip of ()7.\t hick. With the front lens removed it is an efficient dry condenser formedium powers, magnifying Sths inch, with a total of 56, the aplanatic aperture beingover -5. It is mountedlike their Parachro-matic condenser shownin fig. 245, which is alsoa very useful instru-ment, with a total N. I/O, a power of 5-thsinch. It is shown here. principally PIG. 245.—Watsons parachromatic condenser. mounting, for thewhich is identical with that usedwith fig. 244. The collar into which the optical part fits carries an iris diaphragm; onthe diametrical edge of this is engraved a scale showing the atwhich the condenser is working when the iris diaphragm is in. agiven position. We have used this condenser with much pleasureand profit, and can commend it as a truly valuable instrument andyet remarkably low in price. A condenser satisfying modern necessities has also recently been made by Messrs. R. and , which we illustrate in in its complete optical combination consistsof four systems of lenses, thefront of which is a hemisphere,with three combinations the whole is constructed onthe principle of an oil-immersionobjectiv to 1-4, and the aplanaticcone is about , the\\orking distance being fully •()(>.We can speak highly of thi
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
