50 CORRESPONDENCE. 



peachable ability " — no guarantee on which reliance could be placed 

 for thoroughly careful and impartial judgments being given. That 

 these opticians have not, as a rule, cared, to stir up this subject, is far 

 more owing to apprehensions of the danger of attempting to re-argue 

 a verdict once given, than to any sense of weakness in their basis of 

 complaint. What optician dares publicly call attention to such matters 

 when he knows that every word he utters will be viewed with suspicion, 

 while, on the other hand, a few condemnatory remarks from a juryman 

 may do him irreparable injury ? 



The appointment of a jury for the purpose of deciding on the 

 absolutely best histological lens would amount to an attempt to force 

 a general agreement, and would compel opticians either to submit to 

 the verdict or place themselves openly in opposition to the scheme. 



Here then are some of the grounds upon which I should anticipate 

 that medal-awarding, annually or triennially, would produce confusion 

 and discord among us, — would neither attain the end sought, nor in 

 any manner increase the scientific status of the Eoyal Microscopical 

 Society. 



In the pages of the ' M. M. J.' we find expressions of very diverse 

 opinions as to the utility of high angles of aperture ; but this diversity 

 exists principally with reference to lenses of less power than ^. The 

 reconciliation of these opinions is probably only to be attained by 

 microscopists being provided with both high and low angled lenses. 

 But if we look to high-power results — those embodying the highest 

 magnification and finest definition, which exhibit a marked advance on 

 all former results — we find the most conspicuous have been produced 

 with highyangled lenses, — for example : Dr. Woodward's splendid 

 series of photographs of Nobert's lines, diatoms, histological objects, 

 &c. The advocates for low angles have the field open to them — to 

 exhibit any equivalent magnifications that will bear comparison with 

 these photographs ; if they cannot do so, they must stand aside and 

 no longer obstruct the onward march of the construction of high 

 powers. 



Tour obedient servant, 



F.E.M.S. 



Eeply to *' Cbito." 



To the Editor of the ^Monthly Microscopical Journal.' 



224, Regent Street, London, December 4, 1875. 

 Sib, — With reference to the luminous field obtained with certain 

 immersion lenses, whilst with pneumo-lenses the field is dark, when 

 used on a balsam-mounted object illuminated by Wenham's Eeflex 

 Illuminator, it should be noted that " Crito," in his first letter, pro- 

 fessed t(j " perfectly accoiiut for tlie phenomenon " by suggesting a 

 difference in the angular apertures of the leuses used. In reply, I 

 pointed out that the apertures in the sense implied by him do not 

 explain the matter ; but that the true explanation is to be found in 

 the fact demonstrated by Dr. Woodward and Professor Keith, — that 



