ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



Ill 



(2j Eye-pieces and Objectives. 

 Nelson, E. M. — On a new Eye-piece. 

 [Cf. this Journal, 1887, p. 928.] 



Journ. Quek. Micr. Club, III. (1887) pp. 173-4 (1 fig.). 

 Pelletan, J. — Les Objectifs. (Objectives.) Contd. 



Journ. de Microgr., XI. (1887) pp. 546-9. 



(3) Illuminating- and other Apparatus. 



Zeiss' Iris Diaphragm. — Dr. C. Zeiss has designed an Iris 

 diaphragm in which the aperture is approximately circular for all 

 diameters. 



Fig. 13 shows the apparatus in its natural size with the six crescent- 

 shaped metal plates, which form the aperture. These slide over one 

 another by the handle on the right. The internal mechanism is shown in 

 fig. 14 ; one end of the plates is pivoted on the upper plate of the 

 diaphragm case, and at the free end is a straight prolongation which is 



Fig. 13. 



Fig. 14. 



Fig. 15. 



inserted between the raised pieces placed round the circumference of the 

 second disc shown in fig. 15 ; when this disc is rotated by its handle 

 the six plates turn on their pivots. With a turn of the handle to the 

 left the aperture is reduced, and enlarged with one to the right. 



By means of the screw (fig. 13) the diaphragm may be fixed to the 

 Abbe condenser and substituted for the ordinary diaphragms. It can be 

 worked with the little finger of the left hand, so that the other fingers 

 can move the slide while the right hand is available for focusing. 



We gather that Dr. A. Zimmermann, who describes the apparatus,* is 

 not very familiar with the English and American forms of Beck, Wale, 

 and others. He points out that Iris diaphragms are of advantage in 

 drawing with the camera lucida. 



Edmonds's Automatic Mica Stage. — The purpose of Mr. J. 

 Edmonds's apparatus is to rotate a mounted film of mica between the prisms 

 of the polariscope and beneath the object exhibited in the Microscope, 

 producing by the rotation of the mica alone all the colour effects usually 

 obtained by revolving the polariscope by hand. As pointed out by 



* Zcitsuhr. f. Wiss. Mikr., iv. (1887) pp. 343-5 (3 tigs.). 



