ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



95 



MICROSCOPY. 

 a. Instruments, Accessories, &c.* 



Goltzsch's Binocular Microscope. t— We give the description of 

 this Microscope, translated from the author's German original, with 

 slight modifications only. 



" This Microscope (Fig. 3), which is simple to the highest 

 imaginable degree, is calculated to obviate a number of theoretical 

 and practical objections 



which may be raised p^g g 



against instruments of 

 the same kind hitherto 

 described. In particular 

 we get rid of — 



(1) All difficulty in 

 combining the images .Tv^^Mf 

 and all strain to the 

 eyes. 



(2) All variation in 

 magnitude and distinct- 

 ness, as also in the ad- 

 justment of the images. 



(3) All difficulty in 

 accommodating the in- 

 strument for different 

 widths between the 

 eyes. 



(4) The influence 

 which the thickness of 

 the glass prisms, ana- 

 logous to the known 

 influence of the thick- 

 ness of the covering 

 glass, might exert on 

 the course of the rays. 



And lastly, instead of the double reflection, which is not avoided 

 in any of the instruments known, there is only a single reflection for 

 each half of the rays.J 



All these advantages are obtained by a slight modification in the 

 manner in which the images are produced. Whilst in the case of the 

 compound Microscope the object must always be a little beyond the 

 focal point, and in the simple Microscope is generally nearer, in 

 the new arrangement it is brought to the focus itself, so that the 

 pencils of rays proceeding from the different points of the object, 



* In this section are also included optical notes, notices of books relating to 

 the Microscope, and miscellaneous microscopical notes. 



t Carl's Repert. f. Exper.-Physik, 1879, pp. 653-6 (1 fig.). Zeitschr. f. 

 Mikr., ii. (1879) p. I6G-9. 



X The author appears not to have seen the Stephenson binocular. 



