ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



655 



in the figure, defines a vibration of Fresnel's perpendicular to the plane 

 of circuit. 



This apparatus is found to give fringes. The author describes the 

 conditions under which an image with black centre is obtained, and how 

 it gives place to a clear centre. If the appropriate condition is realized 

 for a yellow-green radiation, the interferences in white light yield pure 

 sensible tints. 



In monochromatic light the fringes are black and with a black 

 centre for the yellow-green ; dark without being rigorously black for red 



Fig. 93. 



and violet. Their centres always correspond exactly to the differences of 

 the series 0, A, 2 A . . . m A. 



The author usually employs white light (Nernst filament). The 

 fringes are then coloured, the central one having a sensible tint : they 

 are separated from one another by intervals almost entirely white. 



Ki'MEE, J. — Optischer Interferenzindikator. 



[The author describes how photography of the Newton's rings, produced by 

 the deformation of a lens exposed to great and rapidly produced pressures, 

 may be made useful in measuring such pressures (e.g. of explosives).] 



Zeit. d. Ver. Deutsch. Ing., liii. (1909) p. 53. 

 See also Zeit. f. Instrumentenk., xxx. (1910) pp. 219-22 (5 figs.). 



Nageotte, J. — Nouveau microtome universel. Appareil a congelation pour les 

 grandes coupes. C.R. Soc. Biol. Paris, lxvii. (1909) pp. 503-5. 



