ZOOLOGY AND BOTANYj MICROSCOPY, ETC. 465 



the superiority of the long lever fine-adjustment over any other. (2) 

 No Microscope is worthy to be called a scientific instrument unless it 

 has a centering sub^tage. (3) Choice and Aperture of Objectives, supra, 

 p. 447. (4) Eye-pieces, (5) Daylight, artificial light, and incandescence 

 lamp, suprcL, p. 447. (6) Condensers (Powell's the most effective for 

 powers beyond 1/4). (7) Paraboloids, Lieberkuhns (post), Vertical 

 Illuminator, and Micrometers. (8) Polarization. (9) Diffraction and 

 the difficulties of interpretation with objects requiring high magnifi- 

 cation.] 



EngL Mech., XXXIX. (1884) p. 48. 

 NoE, L. H. — Homogeneous immersion. 



[" It seems to me that to make a lens which shall work through different 

 thicknesses of cover-glass equally well and without adjustment, the 

 immersion medium should correspond with the cover-glass, so that the 

 combined thickness of glass and immersion fluid would always be the 

 same (although the thickness of each varied) for an object in contact with 

 the under side of the cover."] 



Amer. Mm. Micr. Jonrn., V. (1884) p. 79. 

 "Not an Optician." — Theory of the Achromatic Object-glass, 

 [Comments on 0. V.'s articles.] 



Eng. Mech., XXXIX. (1884) p. 210. 

 " Oedebic Vital," — The Dialyte and Plate Glass. 



Engl. Mech., XXXIX. (1884) p. 215. 

 Orth, J. — Cursus der normalen Histologie zur Einfiihrung in den Gebrauch des 

 Mikroskopes sowie in das practische Studium der Gewerbelehre. (Course of 

 normal Histology as an introduction to the use of the Microscope as well as to 

 the practical study of Histology.) 3rd ed., xii. and 340 pp., 108 figs. 8vo, 

 Berlin, 1884. 

 Peaucellier. — Note sur la de'formation des images refractees et sur I'aplanatisme 

 d'un systeme de lentilles. (Note on the distortion of refracted images and on 

 the aplanatism of a system of lenses.) 



■Mem. Soc. Sci. Bordeaux, V. (1883) pp. 327-34 (1 pi.). 

 Peragallo, H. — Histoire sommaire du Microscope compose' et de ses recents 

 perfectionnements, (Compendious history of the compound Microscope and 

 its recent improvements.) 8vo, Toulouse, 1883, 

 Plehn, P, — Apparat zur Priifung der Brennweite des Auges oder anderer 

 optischer Syateme. (Apparatus for testing the focal length of the eye or 

 other optical systems.) 



Title only of German Patent, CI. 42, No. 1894, Feb. 1884. 

 " Pbismatiqtje." — Plate Glass for Optical Purposes, 



Engl. Mech., XXXIX. (1884) pp. 191-2, 281. 



Pkoctoe, E. a, — Review of Poulsen and Trelease's ' Botanical Micro-chemistry,' 



in which the invention of the achromatic microscope-objective is attributed to 



J. J. Lister in 1829 ! Knowledge, V. (1884) p, 231, 



PuscHER & Wiederhold, — Cementing Brass on Glass. 



[Puscher recommends a resin soap for this purpose, made by boiling 1 part 

 of caustic soda, 3 parts of colophonium (resin) in 5 parts of water antl 

 kneading into it half the quantity of plaster of Paris. This cement is 

 useful for fastening the brass tops on glass lamps, as it is very strong, ia 

 not acted upon by petroleum, bears heat very well, and hardens in one- 

 half or three-quarters of an hour. By substituting zinc white, white 

 lead, or air-slaked lime for plaster of Paris, it hardens more slowly. 

 Water only attacks the surface of this cement. Wiederhold recom- 

 mends, for the same purpose, a fusible metal composed of 4 parts of 

 lead, 2 parts tin, and 2J parts bismuth, which melts at 212° Fahr. 

 The melted metal is poured into the capsule, the glass pressed into 

 it and then allowed to cool slowly in a warm place.] 



Polyt. Notizblatt. See Engl. Mech., XXXIX, (1884) p. 119. 

 Beichert, C. — Anleitung zum Gebrauche des Mikroskops. (Introduction to the 

 use of the Microscope.) 14 pp. (2 figs.), 8vo, Wieu, I883t 

 Ser. 2.— Vol, IV. 2 I 



