ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



709 



Fig. 135. 



third tube, c is a diaphragm and d an annular support upon which, 

 on inverting the instrument, the lens a falls, whilst h is held in the 

 usual way by a wire ring. Why the lens a is left loose is not 

 apparent. The magnifying power obtainable with the 

 instrument is not great. If the tubes containing the 

 lenses are drawn out as far as possible it magnifies nine 

 times, the object being at a distance of 14 cm. The in- 

 strument was presented by Mr. J. Snyder to the " Zeeuwseh 

 Genootschap der Wetenschappen," and from that time 

 its existence was so unknown, even in Holland, that it 

 is not mentioned in such a complete history of the 

 Microscope as that of Harting. It had been long in 

 the possession of the Snyder family, but there are no 

 authentic documents concerning it. Harting came to the 

 conclusion, after examining it, that it was really made by 

 Janssen. 



Messrs. Beck made several facsimiles of the Microscope 

 from the original in the South Kensington Loan Collec- 

 tion. 



"Contribution to the History of the Compound Microscope."* 



— Professor Hesehl, of Vienna, describes nine compound Microscopes 

 found in Austria. The one shown in fig. 136 was made by G. F. 

 Brander, of Augsburg, between the years 1760-90. It is 32 cm. high, 

 has a massive foot a, of brass, with a standard 6, into which fits a pro- 

 longation c, which carries a square brass box /, open at the sides. Into 

 the lower plate of this is screwed the tube g, carrying a bi-convex lens m, 

 acting as a condenser, and into the upper (at i) the objectives, together 

 with the double tube (of brass below and wood and paper above) 

 carrying the Eamsden eye-piece n. In the box are two movable plates 

 h, forming the " stage," and between which the slider containing the 

 objects is placed. The upper plate is pressed down to the lower by a 

 spiral spring I, while the lower plate can be raised or lowered by 

 screwing in or out the tube g. The mirror d is attached to an arm 

 e, so that it can be used excentrically if desired. 



There are seven objectives, two of them with Lieberkuhns. The 

 five without Lieberkuhns can be used as simple magnifiers when the 

 tube is removed and the lower part of the stand only employed. The 

 two former could not, however, be then attached to the instrument, 

 and an arm is accordingly supplied to take them (and also the others), 

 which fits into the top of /, and projects laterally over the slide on 

 the right. The tube with the eye-piece also fits on this arm, so that the 

 instrument can be used as simple or compound in this position also. 

 The mirror can be brought under the object in the altered position of 

 the objectives by means of its arm above referred to. 



A second form, shown in fig. 137, has no maker's name, and 

 its date is doubtful, probably about 1800-10. It is inclosed in a 



* Arch. f. Mikr. Anat., xviii. (1880) pp. 391-402 (1 pi.). 



