ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 513 



Fedorow, E. v. — Einigc neue Hilsapparate fiir das polarisationsmikroskop. 



Ann. de Ge'ol. et Mineral de Ihissie, iv. (1901) p. 142, 

 and Zeits.f. Kristallogr., xxxvii. (1903) p. 413, 



Glkichen, A. — Die Vergrdsserung des Mikroskops unter Berucksichtigung der 

 Refraktion und Akkommodation des Auges. Mechaniker, xii. (19D4) p. 135. 



Grattabola, G. — Figure d'interferenza ottenute usando lastre spulite come 

 analizzatore. Atti d. Soc. Tosc. d. Set. Nat., xiv. (1905) pp. 104-71. 



Gkeil. — Beleuchtungsapparate mit Nernstschem Gluhlicht. 



Anat. Anz. Krgdnzunrjsheft z., xxv. (Jena, 1904) p 178. 



Kalahne, A.— TJber das Woodsche Liohtfilter fiir ultraviolette Strahlen. 



Phys. Zeits., v. (1904) p. 415. 

 Pfluger, A. — Die Quecksilberlampe als ultraviolette Lichtquelle. 



Phys. Zeits., v. (1904) p. 414. 

 Regaud, Cl. — Lampe electrique pour la Microscopic 



Comptes Rend. Assoc, des Anatomes, Toulouse, 1904 ; 

 Billiogr. Anatorn. Supple'm. p. 203. 



(4) Photomicrography. 



Photomicrography with Ultra-violet Light.* — The equipment for 

 this class of work has been described by A. Kohler and M. von Kohr, 

 and is now obtainable from Carl Zeiss.f The results which, by the 

 application of ultra-violet light to microscopical technique, are likely to 

 be attained, are mainly — 



1. That the resolving power of the objective is increased in the same 

 proportion as the wave-length of the applied light is reduced. The 

 apparatus presently described doubles the value of an objective of equal 

 numerical aperture with daylight. 



2. That numerous colourless organic objects exhibit considerable 

 differences in their transparency, although in white light they show no 

 colouring ; they behave, in regard to ultra-violet light, exactly as if they 

 were objects diversely coloured. 



3. That on living and defunct organic objects, ultra-violet light 

 exerts, to some extent, marked physiological effects. 



Photography is practically essential to the attainment of the first two 

 objects ; but the results of the latter can be observed by white or coloured 

 light and with ordinary achromats or apochromats. For the ultra- 

 violet rays the specially manufactured objectives used are termed mono- 

 chromats. They have been designed by M. von Rohr, and are corrected 

 for wave-length 275 fx/x (0*000275 mm.). The N.A. of the strongest 

 system is 1*25, while the resolving power, on account of the small wave- 

 length of the light used, becomes equivalent to a N.A. of '1 ' "> with day- 

 light. A table of this relative resolving power is supplied in O. Zeiss 1 

 catalogue. The lenses of the monochromats are manufactured out of 

 molten quartz. Both the strongest systems are immersion Lenses, while 

 the immersion-fluid is a mixture of suitable refractive index, and is 

 composed of chemically pure glycerin and distilled water. The cover- 

 slip is also of molten quartz, and the object slides are formed from thin 



* Zeitschr. f. Instrumentenk., xxiv. (1904) pp. 341-9 (0 figs.). 

 t Special Catalogue, MikrophotogiaphiscUe Einrichtung fiir ultraviukttes 

 Licht (wave-length 0-275 n). 



August 16th, 1905 2 m 



