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ON SOME NEW DIATOMIC STRUCTURE DISCOVERED 

 WITH A NEW ZEISS APOCHROMAT. 



By a. a. C. Eliot Merlin, F.K.M.S. 



{Read March 2Sth, 1911.) 



The late Dr. Goring said in 1829, "Microscopes are now placed 

 completely on a level with telescopes, and, like them, must 

 remain stationary in their construction. " Happily for us," said 

 Mr. Bowerbank, in his address to the Microscopical Society, 

 February 10th, 1847, "this prediction has not been fulfilled. 

 Admii'able as were the combinations alluded to by Dr. Goring, 

 they were very far inferior to those which we now possess, and 

 which we, like the worthy doctor, are, perhaps, inclined to believe 

 are scarcely capable of being surpassed ; but however beautiful 

 the combinations around us, let us hope that the same skill and 

 talent which have wrought these great and valuable improve- 

 ments in the instrument will continue to aid and assist the 

 scientific world by aiming at and achieving a still further degree 

 of perfection." 



The above remarks, taken from Quekett's Treatise on the Cse 

 of the Microscope, published in 1852, remain singularly true and 

 applicable even at the present day, as few, or none, can appreciate 

 better than members of this Club. Thus, in 1899 I obtained 

 a Zeiss g-in. apochromat of measured N.A. 1*42 and I.M.P. 87. 

 I have reason to know that this objective was then probably 

 second to none in existence, and by its aid many new and 

 interesting observations were effected. However, early in 1910 

 it came to my knowledge that a further advance had been made 

 in the construction of these lenses, and I therefore obtained an 

 example of the new combination in June of last year. This 

 objective, exactly similar in aperture and power to the older 

 glass, has been found to afford decidedly superior defining power 

 and contrast on delicate objects when employed with a large, 

 sometimes nearly full, working aperture. The first-fruits were 

 obtained with it while examining an old Moller balsam-mounted 

 type-slide, secondaries being noticed in the capped primary per- 

 forations of Doryphora amphiceros fleitz {Rhap)honeis amiphiceros 



