ZOOLOGY AND BOTANY, MICROSCOPY, EH . 



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Jentsch's Ultra-condenser.* — This apparatus has been designed by 

 F. Jentsch for investigations concerned with molecular movement in 

 gases. It permits the passage of rays from all azimuths of the plane 

 perpendicular to the Microscope-axis, and, in addition to these, many 



Pigs. 5, 6. 



other rays above and below this plane find their way to one and 

 the same point. This peculiarity distinguishes the apparatus from 

 Zsigmondy's ultramicroscope, which only admits a beam of rays from 



* Verh. Deutsch. Phya. Gesell., xii. pp. 992-4 (3 figs.). 

 Feb. 15th, 1911 



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