144 THE BISTOBY AND DEVELOPMENT OF THE MICROSCOPE 



The body-tube, A B C, with its arm, F (in which it screwed at/), 

 ;m<l stem attachment with the fine adjustment were clearly modified 

 from :i design which Cuft' originated. The large ivory head, I, 

 actuated a pinion and rack for raising or depressing the body-attach- 

 ment on the stem, but as there was only one slide the rackwork 

 could noi l>r used unless the fine adjustment was first put out of action 

 by urn-lamping it. The stage and mirror were adjustable on the stem. 

 The large ratchet-wheel controlled by the pinion-handle, 8, gave the 

 required inclination to the stem. 



Xos. I and '2 were ivory and glass 'sliders' for objects, to be 

 applied in the spring-stage No. 3 fitting at T ; the ' hollow at K [No. 

 :!] is to receive the glass tube No. 10.' No. 4 was a diaphragm called 

 a cone, from its conical shape; this was invented by Baker in 1743, 

 and was used in all microscopes up to about 1820, when the wheel of 

 diaphragms was re-invented by Mons. Le Baillif of Paris fitting in 

 the lower end of No. 3, 'to exclude some part of the light which 

 is reflected from the mirror Q.' The forceps. No. 5, could be placed 

 in one of the small holes near the extremities of the stage, or in the 

 socket, R, at the end of the chain of balls No. 6.' No. 6 was an arm 

 composed of a series of ball-and-socket joints, similar to the system 

 employed by Musschenbroek, by Joblot, and by Lyonet, and was in- 

 tended to be applied at W, when the stage was removed. No. 7 was 

 a box of ivory in which discs of talc and brass rings were packed ; 

 No. 8, a hand-magnifier ; No. 9, a sliding arm lens-carrier fitting on 

 Z, when the instrument was required to be used as a simple micro- 

 scope ; No 11, a rod of wire with spiral at the end for picking up 

 soft objects from bottles &c. ; and No. 12, an ivory disc, black on 

 one side and white on the other, fitting at T, to carry opaque 

 objects. 



To use the instrument as a simple microscope the body -tube. 

 A B C, was removed from the ring. K ; the lens-carrier, No. 9, was 

 placed on Z, and a lens with reflector, E, screwed in the ring, c ; 

 the ball-and-socket arm. No. Ci. was applied at AV. by the part X. 

 ami the object held h\ either of the forceps could be turned and 

 viewed as desired. l-'or dissect ions ,Vc. the stage could be screwed 

 on at F, and a glass plate applied at T. 



One of the best examples of this de.sign has a nose-piece with a 

 slide carrying three objectives one of the first arrangements of 

 'triple nose-piece,' or, indeed, of changing nose-piece for objectives 

 (as distinguished from simple lens-carriers) that have been met with. 



A microscope devised l>\ hellebarre was made the subject of a 

 special report to the 'Academic des Sciences' in June 1777, but 

 there is nothing in it deserving special consideration in comparison 

 \\ith contemporary or even anterior forms as bearing upon the evo- 

 lution r.fihe microscope ; us we now know it. In fact, up to the time 

 len achromatism exerted so powerful an influence upon the form 

 jonstruction ofthe instrument, there is no microscope that calls 

 ier consideration save one by an English maker named 

 called .lones Most Approved Compound Microscope 

 'and although, in principle, it does not differ from 

 strument, tig. Ill, H ye1 presented differences of detail. 



