172 



THE AMERICAN MONTHLY [September, 



1590, and it is believed to have been 

 one of their instruments that he 

 brought with him to England. It 

 was an imposing affair ; a copper 

 tube six feet long containing the len- 

 ses ; and was mounted upon three 

 brass dolphins, which rested upon a 

 base of ebony. * * * In 1856, 

 Dr. Robert Hooke, of London, pub- 

 lished his famous work entitled ' Mi- 

 crographia Illustrata,' in which he 

 describes and illustrates an immense 

 number of objects, as seen through 

 the imperfect instruments of his day ; 

 and he describes a method of con- 

 structing lenses of great magnifying 

 power in the form of tiny globules of 

 glass. He also seems to have been 

 the first to avail himself of the prin- 

 ciple of immersion. * * * But 

 the honor of being the first really 

 scientific microscopist should no 

 doubt be accorded to Antony Van 

 Lewenhoek, whose numerous highly 

 important discoveries were all made 

 with the most primitive instruments, 

 constructed by himself, consisting 

 (not of spheres or globules), but for 

 the first time of a double convex 

 lens, provided with arrangements 

 for holding the object and regulating 

 its distance from the lens. * * * 

 His labors in the field of human 

 histology were also very great and 

 fruitful, including as they did, inves- 

 tigations into the minute structure of 

 the nerves, the discovery of the 

 capillaries and the like, and when we 

 consider the difficulties under which 

 he labored, we may well be amazed 

 at the extent and general accuracy 

 of his discoveries. * * * j)j- 

 Robert Hooke, however, was the 

 first to use a compound microscope 

 consisting of a simple objective, a 

 simple eye-lens and an intermediate 

 lens, which latter, however, was in- 

 serted only to enlarge the field of 

 vision, not to increase its power. An 

 Italian, Eustachio Divino, construct- 

 ed an instrument whose tube was 

 * as large as a man's leg,' and with 

 an eye-piece 'as broad as a man's 

 hand,' consisting of two plano-con- 



vex lenses, somewhat after the man- 

 ner of Ramsden's positive eye-piece, 

 used sometimes at the present day 

 for micrometric work. This micro- 

 scope could be drawn out to four 

 lengths, giving magnifying powers of 

 41, 90, III and 143 diameters res- 

 pectively. A few years later a com- 

 patriot of his, Fillippo Bonani, first 

 made use of rack and pinion for 

 purposes of adjustment, and of a 

 substage condenser for improving 

 the illumination. During the follow- 

 ing century improvements were con- 

 stantly made in the construction and 

 mounting of the simple micro- 

 scopes ; the most important, perhaps, 

 being that of Nathaniel Lieberkuhn, 

 of Berlin, who placed his object-lens 

 in the centre of a highly polished 

 concave speculum, by means of which 

 a strongly concentrated illumination 

 is reflected upon the upper side of 

 the object. This method of illumina- 

 tion, as adapted to the modern com- 

 pound microscopes, is still used with 

 apparent satisfaction by some micro- 

 scopists of the British school. Sir 

 Isaac Newton, was the first to 

 propose a reflecting microscope ; 

 but little seems to have come either 

 of his, or of any of the numerous 



subsequent designs of this character. 

 *********** 



" Lieberkuhn also constructed the 

 first solar microscope for projection 

 of magnified objects upon large 

 screens ; and the same was equipped 

 with the movable mirror, to admit of 

 its protracted use by a Mr. Cuff, of 

 London, where Lieberkuhn first ex- 

 hibited his invention. But the high 

 hopes engendered by it were never 

 realized, partly, no doubt, on account 

 of its dependence upon direct sun- 

 light — always an uncertain factor 

 especially in England — but more 

 particularly because it can only dis- 

 play the shadow of things, instead of 

 the objects themselves. It still sur- 

 vives, however, in a modified and 

 improved form, as the oxy-hydro and 

 electric light projection microscopes 

 which, though valueless, for the pur- 



