76f> SUMMAKY OF CURRENT RESEARCHES RELATING TO 



of which this is a modification, the papers are reversed, so that the light 

 travels through the sensitized paper from the back, and is then reflected 

 back from the diagram to the prepared surface. This latter method is 

 only of use when the diagram shows sharp contrasts, but on the other 

 hand it is of use in cases where Wunderer's method is inapplicable, 

 namely, when the diagram paper is very opaque, and when it bears print 

 or other marks upon the reverse side. 



Photography with Ultra-violet Light.* — V. Franz makes use of 

 this method for the study of histological details in the ova of fishes. 

 He considers that by this means it is possible to analyse structures 

 which are beyond the limits of investigation by ordinary microscopic 

 methods. The particular investigation quoted in this contribution 

 shows that the chromophile granules in the plasma of these cells really 

 form part of a network. 



Kohler, A. — Aufnahmen von Diatomeen mit ultravioletten Licht. 



Jahrb. f. Photogr. u. BeprodtM., 1909. 



Re i cher, K. — Mikrokinematographische Aufnahmen bei Dunkelfeldbeleuchtung 

 am Makrokinematographie. Berliner klin. Wochenschr., xlvii. (1910) pp. 4S4-6. 



(5) Microscopical Optics and Manipulation. 



Additional Refractive Indices of Quartz, Vitreous Silica, Calcite 

 and Fluorite.f — At the suggestion of T. Martin Lowry, J. W. Gifford 

 has increased his previous lists J of refractive indices for twenty-six wave- 

 lengths by determining those of seven additional ones. These seven rays 

 are of more recent importance, and several of them, especially those in 

 the spectrum of mercury, promise from their extreme brilliance to be of 

 more than usual value. The method of measurement employed and the 

 instruments used were the same as in the previous experiments. The 

 author gives a table of his numerical results, the wave-lengths examined 

 being 6708 Li, 6438 Cd, 5461 Hg, 5086 Cd, 4800 Cd, 4359 Hg, and 

 4046 Hg. 



Measurements of the Absolute Indices of Refraction in Strained 

 Glass. §■ — L. N. G. Filon has continued his researches on the above sub- 

 ject, and has applied the method which he first described some three 

 years ago.|| The method involves measurement of the deviation of a 

 ray of light passing through a slab of glass under flexure. If a slab or 

 beam of glass of rectangular cross-section be bent in a vertical plane 

 under a bending moment M, and if a plane-wave be transmitted 

 through the glass in a direction perpendicular to the plane of flexure, the 

 light is broken up into two components, one polarized horizontally 

 (i.e. perpendicular to the cross-section and along the line of stress), and 

 the other vertically. The variation in the index of refraction of the 



* Zeitschr. wiss. Mikrosk. xxvii. (1910) pp. 41-3. 

 t Proc. Roy. Soc, A. lxxxiv. (1910) p. 193. 

 % Op. cit., Feb. 13, 1902, and March 3, 1904. 

 § Op. cit., lxxxiii. (1910) pp. 572-9 (4 figs.). 

 || Op. cit., lxxix. pp. 440-2. 



