. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. lly with highpowers, if the hands were kept apart, and which un-steadiness prevents any accurate view of the objedtbeing obtained. Single lenses, when their diameterexceeds that of the pupil, possess the property ofbringing light to the eye and rendering the objedtclearer than it would be without such may be proved by looking at print or othersuitable objedl in a bad light, and noticing howmuch the magnifier aids by its light-c
. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. lly with highpowers, if the hands were kept apart, and which un-steadiness prevents any accurate view of the objedtbeing obtained. Single lenses, when their diameterexceeds that of the pupil, possess the property ofbringing light to the eye and rendering the objedtclearer than it would be without such may be proved by looking at print or othersuitable objedl in a bad light, and noticing howmuch the magnifier aids by its light-colledtingpower. Single lenses are mounted on stands of variouskinds, and then they become what are called singleor simple microscopes. The older observers had noother instruments. These may consist of manylenses, while the compound microscope may be madewith as few as two ; but then they adt upon theprinciple that no image is formed, but the obje(5t isrendered visible at a shorter distance than it couldbe without optical aid. Single microscopes are stillin use for dissecftion and other purposes where only 12 MICROSCOPICAL MANIPULATION, Fig. B. THE COMPOUND MICROSCOPE. 13 a low power is required. And various contrivanceshave been adopted by which both eyes may be usedand much fatigue saved in protradted operations. The compound microscope differs from the simpleinstrument just mentioned in an image being formedand again magnified by being viewed with anotherlens or eye-piece (Fig. 7, A). From what has been said before respedting theformation of images, it is evident if a lens of shortfocus is used and an objedt placed before it, the imagewill be formed at a great distance behind it and bemuch enlarged; if instead of viewing this imagedire(5tly, as in the camera obscura, it is viewed witha suitable lens, l, m, another enlargement takes an instrument might be constru(5ted with onlytwo lenses, as in the diagram Fig. 7, A, but a microscopeso made would of course be a
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