ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



629 



The sections are laid on the upper surface in the ordinary way. In the 

 case of a very hirge number of sections it may be preferable to dispense 

 with the ground strips ; but even then the capillary action will be found 

 sufficient to answer the purpose. 



A 



ReiflF's Polariser.* — This instrument, which is described as a polariser 

 without change of direction and without axis-displacement of the light- 

 ray, is similar to Grimsehl's " Reflex polarisator," and is distinguished 

 from it only in containing a much larger number of reflexions, but at 

 the same time the light-intensity is strongly diminished. The instru- 

 ment is designed in two models. In one an exchange of directions above 

 and below may take place or may be avoided ; the second model has one 

 reflecting plane more than the first. 



Koristka's Achromatic Oil-immersion Condenser. f — This has a 

 numerical aperture of 1'30 and focal length 5'G mm. It is applied 

 to the Abbe fitting in the usual manner. It is essentially an objective 

 of good central chromatic and spherical correction for homogeneous 

 immersion. This property enables the luminous source to be projected in 

 the plane of the preparation without the formation of coloured rings, 

 and also permits of its use as an objective of weak magnification. 



Cox, Alvin J. — A New Comparator. 



Philipinne Journ. Sci., ii. (1907) pp. 139-42 (3 figs.). 



(4) Photomicrography.' 



Photomicrography in Colour with Autochromatic Plates of A. 

 and L. Lumiere.| — Ch.-A. Fran9ois-Franck appears to have met with 

 very gratifying success. Even preparations requiring polarised light 

 presented no special difficulty. Thus reproductions of crystals in Mont 

 Blanc gneiss were faithfully obtained in all their colours. The time of 

 exposure was not found capable of expression by any simple rule : expe- 

 rience only could determine it. In many cases 12 seconds would give 



* Zeitsclir. Physik. u. Chem. Unterr., xix. (1906) pp. 2S-9 (2 figs.) ; see also 

 Zeitschr. wiss. Mikrosk., xxiii. (1907) p. 497. 



+ Supplement to General Catalogue, N 12, Milan, April 1907. 



X Comptes Rendus, cxliv. (1907) pp. 1310-1 ; see also C.R. Soc. Biol, de Paris, 

 Ixii. (1907) pp. 1099-1102. 



2 T 2 



