ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



039 



MICROSCOPY. 



A. Instruments, Accessories, &c* 



(1) Stands. 



Engel's Cross-stage with Automatic Adjustment. f — This appara- 

 tus (fig. 18 ( J), made by E. Leitz, is intended to facilitate the examination 

 of sections and other objects arranged on the stage in rows and to lessen 

 the attention which the observer usually has to bestow in order to 

 insure that he does not pass by mistake from one row to another. The 

 designer substitutes mechanical movement for ocular control. *For this 

 purpose he applies to an ordinary cross-stage a spindle screw connected 

 with a toothed wheel of 50 teeth ; the wheel having a lever and ratchet 



Fig. 139. 



of two teeth by means of which a backward and forward movement can 

 be imparted to the stage. The toothed wheel can be moved through as 

 many teeth as desired. Thus when a horizontal row has been examined 

 by rotation of the spindle screw, the lever movement will automatically 

 bring another row under observation. 



Improvements in the Ultra-violet Microscope.} — W. T. Swingle 

 and L. T. Briggs give a short historical sketch of ultra-microscopy with 

 especial reference to Kohler's important introduction of quartz lenses 

 and cadmium spark. As the ultra-violet light of the cadmium spark is 

 absolutely invisible to the eye, Kohler devised a " seeker " consisting of 

 a quartz lens and a fluorescent screen placed over the eye-piece. This 



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

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



+ Zeitschr. wiss. Mikrosk., xxv. (1908) pp. 60-2 (1 fig.). 



t Science, xxvi. (1907) pp. 180-3 (2 figs.. 



