500 SUMMARY OF CURRENT RESEARCHES RELATING TO 



" is the new glass which hast just been made in Sweden. The revolution 

 " which this new refractor is destined to make is almost inconceivable, if 

 " it is true, as is positively alleged, that, while the highest power of an 

 " old-fashioned microscopic lens reveals only the one four-hundred- 

 " thousandth part of an incli, this new glass will enable us to distinguish 

 " one two-hundrcd-and-four-million-seven-himdred-thousaudth part of an 

 " inch." * 



" A new kind of glass, which is to revolutionize scientific investiga- 

 " tion, has been invented in Sweden. Ordinary glass is comjwscd of six 

 " ingredients, but this compound contains no less than fourteen, chief 

 " among the new substances employed being phosphorus aud boron. For 

 " microscopic purposes the power claimed for this Swedish glass is almost 

 " incredible. One 400,000th of an inch can be distinguished by tho 

 " strongest lens at present, but the new glass will, it is said, reveal the 

 " 204,700,000th part of an inch. If the Swedish invention at all ap- 

 " proaches what is promised for it, its importance can hardly be exagger- 

 " atcd, but tho very moderate performance of the so-called ' unbreakablo 

 " glass ' invented a few years ago, may warn us to be somewhat sceptical 

 " in regard to new wonders in the way of glass." f 



Curiosities of the Senses. 



[" According to a memoir communicated to the Biological Society of Paris by 

 M. Mathias Duval, and reported in the Steele, it is not advantageous when 

 looking through a telescope with one eye to close the other, but rather the 

 contrary. We have not succeeded in verifying this observation with the 

 Microscope."] 



Scientif. News, I. (1888) p. 372. 

 Cz[apski, S.] — Bemerkungen fiber Prof. Abbe's Abbandlung: Die Vergrosserung 

 einer Linse Oder eines Linsensystems. (Remarks on Prof. Abbe's paper : The 

 magnifying power of a lens or a lens-system.) 



[Criticism of the papers of Prof. Abbe and Prof. Giltay in this Journal, 1884, 



p. 348, and 1885, p. 960. 

 " For practical microscopists to adopt Abbe's definition for ordinary use seems 

 to me not only purposeless, but at no time desirable. On the other hand, for 

 scientific purposes in theoretical discussions relating to the magnifying 

 power of an optical apparatus, the stricter definition of Abbe will be of 

 value ; and even in Giltay's point of view, the number which represents the 

 magnifying power is subjective, aud applies only to an eye which sees an 

 object best at the distance of 25 cm., but is different for another length of 

 vision. The arbitrary character of the measure which Giltay raises as an 

 objection to Abbe cannot be supported as an argument against bis definition, 

 for it is common to all magnitudes expressed in so-called absolute units.] 



Zeitschr.f. InstrumentenL, VIII. (1888) pp. 104-5. 

 D., M. T. — Microscopical Drawings. 



[Device for drawing with the Microscope : — " Take a small portion of the 

 silvering from the back of a mirror, about 1/1G in. in diameter (there must 

 be a thick coating of paint on the back of the amalgam to support it, or it 

 will not break oft}. This small reflector is to be mounted witli cement on 

 the edge of a piece of watch- spriug at the proper angle. The spring is bent 

 round and fixed to a brass tube fitting over the eye-piece, so that the reflector 

 stands about 1/4 in. from the eye-lens aud central with it. On looking into 

 it the object on the stage of the Microscope is seen, and appears to be pro- 

 jected on to the paper spread below. I believe that steel mirrors are used 

 for the same purpose ; but the amalgam has a very good surface, costs 

 nothing, and can be renewed in a very short time. It is better than the 

 ' neutral glass plate.' "] 



Engl. Jlech., XLVII. (1888) p. 170. 



Essex local paper. t Christian World, 1888, April 19. 



