479 



Mr. J. J. Vezey .,. Arranged Butterfly Scales, etc. 



Mr. J. E. Webb ... Actinosphjerium, Arachnoidiscus, etc. 



Mr. C. West ... ... Dissections of Vespa and Djtiscus. 



Six tables of Microscopes with objects were exhibited by Messrs. 

 Baker, Beck, Johnson and Sons, Steward, Swift and Son, and 

 Watson and Son. 



Attendance : Members, 140 ; Visitors, 390 ; Total, 530. 



New Books. 



We have received from Messrs. Williams and Norgate a copy of 

 the German translation of Dr. E. Giltay's *' Hoofdzaken uit de 

 leer van het zien door den microscoop," an elementary work on the 

 fundamental laws of microscopic vision exemplified by seven 

 objects. After a short introduction on the instrument itself, 

 taking as types Zeiss's No. 14 and No. 4a, which he supposes to 

 liave come into the hands of an absolute novice, Dr. Giltay proceeds 

 to an examination of the seven objects chosen, beginning with 

 simple lines drawn in ink on the surfaces of an ordinary slide and 

 cover glass, which are successively viewed by a low and moderately 

 high power. He explains the alteration in the image produced by 

 focussing, the depth of the focal plane diminishing with the power, 

 the inversion of the picture, and so forth. The next object consists 

 of pieces of glass thread painted with two tints of Indian yellow 

 and examined immersed in cedar oil; by means of these is 

 shown how the shallowness of the focal plane bears on the ques- 

 tion of microscopical perception and what is implied by the term 

 optical section. Starch and then air-bubbles are next considered, 

 and the latter, with the interpretation of the phenomena they 

 exhibit under the microscope, forms, perhaps, one of the most im- 

 portant sections of this little book for the ordinary observer. Milk 

 and collenchyma are the fifth and sixth objects, and the seventh 

 and last is Abbe's diffraction plate. From the purely optical point 

 of view this deserves, and should obtain, the close study of all 

 intending microscopists who wish to understand the relations ol 

 aperture to power and the laws bearing on the resolution of minute 

 structures, as primarily enunciated by Abbe. The theory of 

 immersion objectives is included in this section. For such as read 



