ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 709 



the original suggestion not only of water for immersion lenses but 

 of oil also, the dates being : Oil immersion, Amici, 1841 ; Oberbauser, 

 1845 ; Wenbam, 1870.* Homogeneous immersion : Stephenson, 1878. 



P. 33 : Professor Eiddell should be credited with the original 

 invention of the stereoscopic binocular. 



P. 191 : The expression " angular aperture " (here and at other 

 places in the earlier parts of the book) should be replaced by " aper- 

 ture," as a synonym for which it is in fact used by the author, 

 " angular aperture " (and its equivalent " angle of aperture ") being, 

 as shown by Dr. Carpenter at p. 852, one of the factors of aperture. 



P. 193 : The quotation " minute details are concealed or destroyed 

 till the aperture is sufficiently reduced," should be omitted, as it 

 conflicts with the author's own more correct view, quoted above, that 

 minute details are more perfectly shown by objectives of widest 

 aperture. 



The statements at pp. 193 and 196-7 that there is an inherent 

 incompatibility between good definition and large aperture should be 

 deleted, as it is now known both from theory and experiment that 

 the definition of objectives of the widest apertures (1 • 47 out of a 

 possible 1 • 52) is as perfect as with those of less aperture. The 

 wider the aperture of an objective, the greater the technical skill 

 which is required on the part of the practical optician ; but the notion 

 that as the aperture of an objective is increased its defining power 

 must necessarily, either on theoretical or practical grounds, be im- 

 paired, happily belongs to a closed chapter of microscopy. 



It may be safely said that there is no book in the English or any 

 other language which more completely combines all that the amateur 

 worker with the Microscope requires. 



The Microscope and the Origin of the Anatomy of Plants.f — 

 Dr. W. J. Behrens, in a paper under this title, gives an historical 

 sketch of the researches of the early vegetable histologists, more 

 especially Cesalpini, Malpighi, and Grew. 



The paper also contains a short history of the simple and com- 

 pound Microscope, terminating with the achromatic Microscope, the 

 invention (or rather " construction ") of which is — following Harting 

 — put as early as 1807 by Van Deyl, a Dutchman, afterwards 

 improved by Selligue, Chevalier, and Amici between 1820 and 1830. 

 Van Deyl's objective was made of two biconvex crown-glass lenses, 

 with an intermediate biconcave of flint glass. Such an objective had, 

 of course, a great amount of spherical aberration. 



Huberson's 'Journal de Photographic et de Microscopie.' — 



The first series of this journal (6 vols.) was exclusively devoted to 

 photography, but last year a second series was commenced under the 

 above title, with the intention of including also Microscopy, " at first 

 elementary and restricted to the more ordinary notions, then more 

 advanced, and finally as complete as the competence of the editor and 

 the taste of the readers will allow." The combination of photography 



* See this Journal, ii. (1879) p. 490. 



t 'Gaea,' xvi. (1880) pp. 480-9, 536-43, 675-80. 



