ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 697 



Nelson, E. M.— Central v. Oblique Light. [Supra, p. 692.1 



Engl. Mech., XLIII. (1886) p. 300. 



„ The resolution of Diatoms whose striae are of unequal fineness. 



[Posf] Ibid., p. 328 (1 fig.), p. 396. 



„ The interpretation of the Six Spectra of Pleurosigma angulatum. 



[Supra, p. 694.] Ibid., pp. 337-8 (5 figs.), p. 396. 



Objectives, New. 



[" The new 1/8 in. objectives of Zeiss, made of the new glass, will be in the 

 market very soon — indeed, they are expecting daily to receive a supply. 

 Hereafter Mr. Zeiss will not make any more of the celebrated 1/18 in. 

 objectives, but will provide another lens to take its place.''] 



Amer. Hon. Micr. Journ., VII. (1S86) p. 118. 

 Pellbtan, J. — La Theorie du Microscope et l'Optique simplifiee. (The theory 

 of the Microscope and simplified optics.) 

 [Characteristic introduction to a series of articles intended to be published 

 on simplified optics.] 



Joum. de Microgr., X. (1886) pp. 279-85. 



Piersoi's (G. A.) Photograph of Bacillus tuberculosis. 



[x 1090 — "shown as clear and distinct as when viewed with the Micro- 

 scope.") 



Amer. Mon. Micr. Journ., VII. (1886) pp. 99. 

 Queen's (J. W. & Co.) Acme No. 4. Microscope. [Post.'] 



Micr. Bull. (Queen's), III. (1886) p. 17 (1 pi. and 1 fig.). 

 Resolving 152,000 lines to the inch. 



[Correspondent thinks that " with a little patience it could be accomplished, 

 for I have already resolved 140,000 with the same objective and illu- 

 mination ! "] 



Micr. Bull. (Queen's) III. (1886) p. 14. 

 Royston-Pigott, G. W. — Microscopical Advances. XI., XII. 

 [Diatomic beading and images. Diatomic colours.] 



Engl. Mech., XLIII." (1886) pp. 313-4 (7 figs.), pp. 383-4 (2 figs.). 

 [Royston-Pigott, G. W.] — Delicate Fine Focussing Adjustment. 



[Supra, p. 686.] Engl. Mech., XLIII. (18S6) p. 340 (2 figs.). 



S., H. G. F. — A Concentric Microscope. 



[Modifications in Cox's Microscope with concentric movements * would give 

 it the essential features of the best known English and American Micro- 

 scopes. (1) The tail-piece (preferably one only) should have a clamp 

 above the stage to fix it parallel to the optic axis ; (2) the mirror-bar 

 should be removable, and arranged to clamp on one of the feet of the 

 base; (3) the stage should have mechanical movements like "Watson's 

 or Ross's best diatom stage " ; and (4) a " combination condenser " like 

 Swift's or Pillischer's should be applied. "The concentric or radial 

 construction . . . gives such extreme stability at every angle of inclina- 

 tion that ... it seems destined to supersede the ' Jackson ' model, as 

 that superseded the ' Ross ' with the majority of makers."] 



Engl. Mech., XLIII. (1886) p. 352 (2 figs.), p. 375. 



Thiesen, M. — Ueber die Ablesung von Normalbarometern und uberhaupt von 



grb'sseren Flussigkeitsoberflachen. (On the reading of normal barometers 



and large fluid surfaces.) 



[The difficulty of exact readings where the surface of the mercury is large 



has led to various contrivances based on the principle that the distance 



between an object and its image seen in a plane reflecting surface is 



bisected by the surface. Marek substituted for Pernet's fixed index the 



image of a horizontal thread thrown by a lens into the centre of the tube ; 



but the results obtained are not satisfactory. Dr. Thiesen uses the scale 



at the back of the tube as the object ; the reading for the surface of the 



mercury is then found by a simple micrometric measurement of the dis- 



* Cf. this Journal, iv. (18S4) pp. 279-81. 



