442 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



Hooke appears to have first suggested the use of a very large field- 

 lens, as described in his ' Micrographia ' in 1665. 



The system of eye-jiiece shown in the so-called Charles I. Micro- 

 scope was (we believe) devised by Homberg, the well-known member of 

 the Academie des Sciences, and the instrument was first figured in an 

 Italian work (which we have repeatedly cited in this Journal) entitled 

 ' Nvovi inventioni di tvbi ottici/ a communication to the Accademia 

 Fisico-matematica, of Eome, in 1686, by Ciampini, the then editor of the 

 Giornale de' Letterati. [We note in passing that Ciampini's authorship 

 of the work in question is alluded to by Langenmantel in the Miscell. 

 curiosa, 2nd Decade, 7th year, 1689, p. 444, and also in Bonanni's 

 ' Micrographia curiosa' (Rome, 1691, 4to), p. 15.] 



From the similarity to the figure of Homlerg's Microscoi:e, an 

 instrument in the collection of M. A. Nachet has been identified, in 

 which the peculiar construction of eye-piece above noted obtains. The 

 identification of a number of other Microscopes of similar construction 

 follows as a matter of reasonable probability, and we have thought the 

 present a favourable occasion to notice a few of them (from Mr. Crisp's 

 Collection), 



Fig. 62 shows a " Homl erg " Microscope acquired in Groningen, 

 Holland, which difiers from the "Charles I." instrument (1) in being 

 covered with gilt parchment instead of leather, (2) in having a " t-et- 

 nut " or clamping screw-ring to correct the tendency of the body-tube to 

 shake in the thin screw-socket in which the focusing screw acts. 



Fig. 63 shows a similar Microscope, formerly belonging to George III., 

 but with a (probably) modern base-support, in which a mirror was fixed. 

 Fig. 64 shows a "Homberg" Microscope, formerly belonging to 

 Pope Benedict XIV., having a small disc object-stage with a slight 

 range of motion in the opening of the base, with a clamp-screw beneath. 

 This instrument shows that the viewing of opaque objects was princi- 

 pally intended. 



"Due de Chaulnes' " Microscope. — We gave on p. 118 a figure of 

 one of these instruments, which we examined in the Museo di Fisica, 

 Florence, the specialty of which was evidently the verification of micro- 

 metric measurements. 



We here give a figure of a Microscope (fig. 65) we obtained in 

 Naples, which is remarkable (1) for its ornate character, and (2) for its 

 general resemblance to the Due de Chaulnes' Microscope, though the 

 aim of the construction probably differed considerably. 



It bears the inscription, " D. Joannes de Guevave F. 1752," at 

 which date even the best Microscopes were seldom provided with any 

 form of mechanical stage. This instrument, however, has object-carriers, 

 consisting of two short pillars travelling laterally, actuated by screws 

 in grooves right and left of the stage ; the upper ends of the pillars are 

 pierced to allow the slide to be adjusted and clamped. The b. dy-tube 

 pivots laterally, so that, in combination with the stage movements, every 

 portion of the object can be viewed successively. The mirror is also 

 mounted on a short pillar moving forward or backward in a groove 

 actuated by a screw in front. 



In the general construction, stability seems to have been a very 

 secondary consideration, whilst the ornamentation was elaborated with 

 special attention. The body-tube is of tortoise-shell and ivory, and the 

 shaped box base is of inlaid wood. 



