ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1065 



is a tube of length corresponding to the focus of the condenser, and 

 to this is screwed a frame consisting of a stage for the objects, and a 

 fitting with Society screw to take the ordinary objectives. There is a 

 rack and pinion for focusing. The image from the objective is 

 received by a right-angled prism and is thrown through an amplifying 

 lens on a sheet of paper placed below to receive it. As has been 

 before pointed out, a microscoj^ic object can thus be more easily and 

 correctly traced or drawn, than by any other method. The instru- 

 ment can be used as an ordinary magic lantern by removing the 

 Microscope attachment and substituting an achromatic front lens. 



Leckenby's Microscope Pencil-case.* — Mr. A. B. Leckenby has 

 devised a combination of a pencil-case and a Microscope for the use of 

 school children in the study of botany. " It consists of a thin tube 

 of brass to hold the pencils, at the end of which is a lens mounted in 

 such a way that when drawn out of the tube it is a simple Microscope 

 well adapted for studying seeds and parts of plants, insects, &c. In 

 addition to the Microscope pencil-case Mr. Leckenby has prepared 

 sets of fifty slides of seeds neatly mounted on stifi" paper to accompany 

 it. The case and sets of seeds will be a source of pleasure and 

 instruction to children, and also to persons more advanced in life, for 

 this little Microscope can reveal a world of beauty." 



Adjusting the Eye-pieces of Binoculars to eyes of unequal focal 

 length.f — Colonel Malcolm thus describes an arrangement for 

 binocular field-glasses which might we think be well applied to the 

 Microscope, having regard to the number of observers whose eyes 

 di£Fer in focal length. 



" One tube is left untouched ; the eye-piece of the other is so 

 arranged that it can be moved through a small range in and out, 

 with reference to the eye-piece of the untouched tube, by turning 

 round a milled ring. An index arrangement is provided. 



The unaltered tube is used with one eye and brought to the most 

 perfect focus possible in the ordinary way ; then the other tube is 

 used with the other eye, aud by means of the adjustment its definition 

 is made as perfect as may be, the ordinary adjustment not being 

 interfered with. The two eyes are then used together ; and the 

 process of adjustment had better be gone over again, as certainly the 

 two eyes do help each other. 



The final position of the index mark is noted ; and that holds 

 good for all ranges, as far as I have tried. 



Having noted this, you may lend your glasses to your friend, who 

 may alter them to his sight, and yet have them in perfect order for 

 yourself by bringing the index to your own mark." 



Abbe Condenser. — This condenser, the use of which is extending 

 very largely both (ju the Continent and in America, is made in a 

 great variety of forms, nearly all concurring, however, in a very con- 

 Hidcrablo curtailment of the original dimensions which rendered it 



♦ Arner. Mou. Micr. Jouni., vi. (1885) p. 200. 

 t Proc. riiyrt. Soc. Loud., vii. (1885) pp. 80-1. 



