830 SUMMARY OF CUERENT RESEARCHES RELATING TO 



" Prof. Abbe sbows, however, tliat ' oblique vision in the Microscope is 

 entirely different from tbat in ordinary vision, inasmucb as tbere is no 

 persj)ective, so that we have no longer the dissimilarity which is the basis 

 of the ordinary stereoscopic effect, but an essentially different mode of 

 dissimilarity between the two pictures.' In the Microscope there is no 

 perspective foreshortening. There is no difference in the outline of an 

 object viewed under the Microscope by an axial or by an oblique pencil. 

 There is simply a lateral displacement of the image — an entirely different 

 phenomenon to that which occurs in non-microscopic vision. Thus, whilst 

 the mode of formation of dissimilar pictures in the binocular Microscope is 

 different from the jDroduction of ordinary stereoscopic pictures, the brain 

 mechanism by which they are so fused as to give rise to sensations of 

 solidity, depth, and perspective, is the same." 



Hanks, H. — Errors likely to occur in Microscopical Observations. 



[(Abstract only). " The hemispherical bosses upon certain diatoms are persistently 

 seen by some as cup-shaped depressions or concavities."] 



Rep'irt of Proceedings of San Francisco Micr. Sac, July 13th, 1887. 

 Magnifying-power of Objectives, Measurement of. 



[Further letters by F. E. Brokenshire and F. J. Greorge.] 



U7igl. Mech, XLV. (1887) pp. 540, 561-2. 

 Marshall, W. P. — On the measurement of the magnifying power of Microscope 

 Objectives; with exhibition of 1/25 in. water-immersion objective of Powell and 

 Lealand. 



[Camera lucida method.] Midi. Natural, X. (1887) pp. 226-8. 



Pol I, A. — I recenti progressi nella Teoria del Microscopio. (Kecent progress in the 

 theory of the Microscope.) 



25 pp. 8vo, Firenze, 1887. (Sep. repr. from Bivista Scientifico-Indusiriale.') 

 KoTSTON-PiGOTT, G. W. — Microscopical Advancos. XXII., XXIII. 

 [Diffraction ancient and modern — Insects' scales.] 



Ungl. Mech., XLV. (1887) pp. 547-8; XLVI. (1887) pp. 1-2 (3 figs.). 



(6) Miscellaneous. 



Royal Microscopical Society of the Sandwich Islands. — In 1878* we 

 referred to the establishment of this Society by King Kalakua, a Society 

 which we gather has now ceased to exist. This would appear to be the 

 case from a report of a recent meeting of the San Francisco Microscopical 

 Society, where Prof. F. L. Clarke, of Honolulu, is stated to have " given an 

 interesting account of microscopical matters in the Hawaiian Islands," and 

 in the course of which he " narrated the career of the Microscopical Society 

 which once existed there." The king is now desirous to perfect arrangements 

 for the systematic exploration and study of the natural history of the 

 islands, and in pursuance of this plan the San Francisco Society is to be 

 plentifully supplied with collections of objects suitable for microscopical 

 investigation, and it has been " selected as an agent for the distribution of 

 such material to societies with similar aims in other parts of the world." 



Curiosities of Microscopical Literature. — A recent paper f on " Mount- 

 ing Media, so far as they relate to diatoms," may certainly be ranked 

 amongst the curiosities of microscopical literature, and we are at a loss to 

 understand how it came to be printed. We quote below in full that part 

 of the paper which is headed " Fluids " and it will be seen that the author 

 begins by the statement that he " cannot too emphatically condemn " certain 

 media, such as biniodide of mercury and iodide of potassium, " simply from 

 " the fact that the diatoms will not remain on the cover-glass, but must 

 " necessarily fall to the bottom of the cell." This, to begin with, was a most 

 astounding statement to make after all that has been said on the subject, 



* See this .Journal, 1878, p. 152. 



t Journ. Qiiek. Mier. Club, iii. (1887) pp. 108-14. 



