1020 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. IGI. 



MICROSCOPY. 



o. Instruments, Accessories, &c.* 



(1) Stands. 



Ahrens' New Erecting Microscope.* — In this instrument (fig. IGl) 

 the erection of the image is obtained by two right-angled prisms 



crossed in the way used in some 

 of the binocular field-glasses. 

 Tlie form of the prisms will be 

 gathered from the woodcut, 

 which shows the boxes in which 

 they are i^laced. The ft)llowing 

 is Mr. C. D. Ahrens' description 

 of the instrument. 



" The advantages of this over 

 the one I made some years ago 

 are that the rays arc parallel 

 with the stage, and better defini- 

 tion of the object is given. The 

 prisms are not so troublesome 

 to make, and by making them 

 of quartz more light is obtained. 

 The surfaces are also more per- 

 fect, and they are less liable to 

 sweat or get injured. If pro- 

 perly cut they only show one 

 image. As the rays travel 

 across the prisms to the extent 

 of about 3 in., only a short 

 body is required. I believe 

 such an erecting Microscope 

 is the only way to see the 

 objects in their right form, as I 

 have found that lenses when 

 used for inverting mike some 

 objects appear as in a pseudo- 

 scope with prisms." 



Klein's Excursion Micro- 

 scope.! — Dr. L. Klein writes 

 that botanists and zoologists 

 who are accustomed to make 

 excursions to collect microscopical specimens only too often feel the 

 want at the collecting place of a useful Microscope which would enable 

 them to determine approximately what they have collected, and to 

 recognize whether a locality ofters them any advantage or not. By 

 practice a rough separation of the larger specimens can be made with 

 the naked eye, but of the smaller ones many a rare specimen is over- 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; (.3) Illu- 

 minating and other Apparatus; (4) Fliotomicrography ; {ty} Microscopical Optics 

 and Manipulation ; (6) Miscellaneous. 



t Zeitschr. f. Wiss. Mikr., v. (1888) pp. 19G-9 (.S figs.) 



