. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. particularly useful for objedts to be examined bythe aid of the lieberkuhn, as it forms its ownblack stop. Its late talented inventor was very expertin the employment of this kind of illumination. Thedefe(5ts of the lieberkuhn are that its light is nearly THE PARABOLIC LIEBERKUHN. 99 vertical, and therefore, like the tropical mid-daysun, casts little or no shadow; this, however, may beremedied, to some extent, by turning the mirroraside and us
. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. particularly useful for objedts to be examined bythe aid of the lieberkuhn, as it forms its ownblack stop. Its late talented inventor was very expertin the employment of this kind of illumination. Thedefe(5ts of the lieberkuhn are that its light is nearly THE PARABOLIC LIEBERKUHN. 99 vertical, and therefore, like the tropical mid-daysun, casts little or no shadow; this, however, may beremedied, to some extent, by turning the mirroraside and using the light from only one-halfof the speculum (Fig. 22, B); it also requires the objecStand its mounting to be small enough to allow thefree passage of the light around it from the defecfts caused the lieberkuhn to fall somewhatinto disuse; the introdudtion of the binocular micros-cope, however, caused it again to be employed, as it Fig, was found very suitable for the peculiar class ofopaque objedts which are so well displayed in reliefby its stereoscopic power. It has, however, againbeen nearly superseded by an improved form, whichhas all its advantages, besides some peculiar to improved instrument, which is known as theparabolic lieherkuhn (Fig. 24), is another of thenumerous contrivances of the late Richard Beck,and was described by him in the Microscopical H 2 loo MICROSCOPICAL MANIPULATION. Quarterly Journal for 1865 (vol. xiii., p. 116). It con-sists of a portion of a silvered paraboloid, which isattached by a ring to the setting of the objedt-glass,so that it has some range of adjustment like theordinary lieberkuhn; but instead of the light beingdiredled upon it from below through the hole in thestage, it is supplied from one side, which allows thisform of lieberkuhn to be used with objedts mountedin the ordinary way. It is necessary when lamplight is used that the rays should be rendered parallelb
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmicroscopy, bookyear1
