ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 867 



sensitiveness of these plates is much greater than usual, so that the 

 time of exposure will be diminished instead of lengthened, and by 

 using plates variously stained suitable contrasts might be obtained 

 with differently stained srjecimens. 



Mr. R. Hitchcock also refers * to the so-called ortho-chromatic or 

 iso-chromatic sensitive plates now sold which " may be found useful 

 in photo-micrography, but it is well to consider that they differ from 

 other plates mainly in their greater sensitiveness to the less re- 

 frangible rays, while they are scarcely less sensitive to the blue which 

 still preponderates. For this reason, in order to obtain strictly 

 uniform results for all colours, coloured screens must be used, par- 

 ticularly when working with sunlight. The great advantage of such 

 plates rests in the fact that they are sensitive to the red and loss 

 refrangible rays which do not at all, or only slightly, affect the ordi- 

 nary plates." 



Abbe, E., and Schott, O. — Glasschmelzerei fur optische und andere wissen- 

 schaftliche Zwecke — Productions- und Preis-Verzsichniss. (Glassworks for 

 optical and other scientific purposes — Catalogue.) [Supra, p. 856.] 



20 pp. and 1 pi. (8vo, Jena, 1886). 



Alferow, S. — Nouvel Appareil, servant a compter exactement les globules 



sanguins. (New apparatus for exact counting of blood-corpuscles.) 



[The enumeration method is more important than the moist chamber. 



Instead of counting by means of squares on the slide or in the ocular, a 



record of the blood-corpuscles is made on the ground glass plate of a photo- 



micrographic camera, which is fixed in the tube as far as possible from 



the objective. Fine adjustment is made with the stage. Instead of the 



preparation itself, a representation of it is thus used for the enumeration.] 



Arch. Physiol. Norm, et Pathol., III. (1884) pp. 269-86 (3 figs.). 



Andkieu, L. — Sur un Chromatometre, destine a mesurer la couleur des liquides. 



(On a Ohromatometer for measuring the colour of liquids.) [Post.'] 



Comptes Rendus, GUI. (1886) pp. 281-4 (1 fig.). 

 B a r s c h, E. — Illuminating Apparatus for the Microscope. 

 [Description of the Various forms.] 



Bull. Rochester Acad. Sci., 1886, pp. 1-8. 



Berger, C. L. — Hilfsapparate fur die Bediirfnisse der Werkstatt. III. Apparat 



zur genauen Bestimmung der Brennweite von Objectivglasern. (Apparatus 



for the exact determination of the focal length of objectives [of the telescopes 



of geodetic and astronomical instruments]). 



[Contains a description of a Microscope used for fixing spiders' threads, post.'] 

 Zeitschr. f. Instrumentenk., VI. (1886) pp. 272-6 (3 figs.). 

 Czapski, S. — Die Mikrometerbewegung an den neueren Zeiss'schen Stativen. 

 (The fine-adjustment to the newer Zeiss stands.) [Post.] 



Zeitschr. f. Wiss. Mikr., III. (1886) pp. 207-9 (1 fig.). 



Denaeyer, A. — Procede phototypique industriel applicable a la reproduction 



des photomicrographies. (Phototype process applicable to the reproduction of 



photo-micrographs.) [Post.] Pull. Soc. Belg. Micr., XII. (1886) pp. 92-6. 



English v. Foreign Microscopes. 



[Inquiry by " Briton " (1) why English Microscope-makers should be unable 

 to compete with the foreign makers ? or (2) if they are able, why our 

 schools of science should be so flooded with foreign instruments ? Replies 

 by S. Bottone that it arises from the " disparity in the prices of labour 

 and food here and on the Continent " — by " Another Briton," suggesting 



Amer. Mon. Micr. Journ., vii. (1886) pp. 155-6. 



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