644 



SUMMAKY OF CURRENT RESEARCHES RELATING TO 



Fig. 163. 



Giuseppe Campani of Eome, who flourished in the latter half of the 17th 

 century, when he was regarded as one of the most skilful makers of tele- 

 scopes in Europe, outrivalling Eustaehio Divini of Bologna, and in 

 technical perfection of optical work not unworthy to rank with Huyghens. 

 His Microscopes have now become so rare that we need hardly plead any 

 other justification for figuring one of them (fig. 163) 

 which we met with during a recent visit to Italy, and 

 which is the first (to our knowledge) that has been 

 figured.* 



The body-tubes are of wood, and are provided 

 with a double focusing arrangement, one (the lower) 

 for regulating the distance between the object-lens and 

 the object by screwing into the metal ring-socket 

 supported on the tripod, the other for varying the 

 distance of the eye-lens from the object-lens by a 

 screw-motion of the upper tube within the lower one. 

 The base consists of two plates, the upper one being 

 attached to the tripod and the lower one being held 

 to the former by the lateral pressure of a bent spring 

 on either side travelling on rollers, the object-slide 

 being placed between the plates, which are perforated 

 in the centre so that the object may be viewed by 

 transmitted light. 



The object-lens is bi-convex, of somewhat yellow 

 glass, and about 1/2 in. focus, and is held in a wood 

 cell by a perforated cap, which serves as a diaphragm. 

 The eye-lens is bi-convex, of about 1 in. focus. There 

 is no field-lens, and hence we think the date of the 

 construction may with some probability be assigned 

 as prior to that of Hooke's compound Microscope 

 (vide his ' Micrographia,' 1665), in which the appli- 

 cation of a field lens was claimed as a novelty. In 

 confirmation of this point we may note also that in 

 1667 Hon. Fabri, in his ' Synopsis optica ' (4to, 

 Lugduni), Prop. 46, described a compound Microscope by Divini, in which 

 two pairs of plano-convex lenses were used for the eye-lens and field-lens 

 respectively, so that the application of a field-lens to the eye-piece of a 

 Microscope was known in Italy at that date. Divini's Microscope was also 

 fully described in the ' Giornale de Letterati,' i. (1668) pp. 52-4, which 

 description was partly translated in Phil. Trans., iii. (1668) p. 842, and 

 must have become widely known. 



James's Dissecting Microscope.f — Dr. F. L. James uses a cigar-box 

 from which the top and front side have been removed, an old hand-mirror, 

 and a plate-glass cover (fig. 164). In use, this stands on a board which 

 carries an upright rod, provided with a ball-and-socket joint. On this rod 

 slides an arm made of wire, twisted so as to hold a watchmaker's eye-glass. 

 When not in use the ball-and-socket joint permits this rod to be turned 

 down out of the way. The object to be dissected or slide to be arranged is 

 placed on the plate-glass cover. The light is thrown upward by the mirror 

 and through the cover-plate, so as to render visible the minutest detail of 



* Society of Arts Cantor Lectures on the Microscope, by J. Mayall, junr. Creprint in 

 collected form) 1886, p. 10 (1 fi^.)- 



t Pioc. Amer. Soc. Micr. 9th Ann. Meeting, 1886, pp. 145-6 (1 fig.). 



