504 G. C. KAROP ON POCKET MAGNIFIERS. 



" mirror loup " is made by Messrs. Watson. This brings me 

 to the instrument which was the primum mobile of this, I fear, 

 discursive note, and which has much the same intention as the 

 one just mentioned, but carried out in rather a simpler and less 

 expensive manner. It is, in fact, a modified Herschelian doublet 

 made up of a lower inequi-convex 6 : 1 lens and an upper plano- 

 convex of smaller size, just sufficiently spaced to admit a thin, 

 polished metal reflector-diaphragm between them. The sizes and 

 focal lengths of the lenses are approximately as follows : 



Inequi-convex : diameter, TS ; focus, 2*1, in inches or parts. 

 Plano-convex: „ "65; ,, 1*75 „ „ 



Focus of combination : „ 1*95 ; 7? » 



But of course, all these can be varied in relative proportion if 

 required. The three elements are mounted separately, just as in an 

 ordinary triple magnifier, so that, although it is calculated to act as 

 a " system," either lens may be used by itself, with or without the 

 speculum. This arrangement should prove very convenient to 

 the naturalist in the examination of small flowers, floral organs, 

 insects, etc., and it will be found to perform very well indeed on 

 such-like objects in the open, for which purposes it was chiefly 

 intended. It is probable that by artificial hght, unless skilfully 

 managed, it will be less satisfactory, the illumination being 

 generally either too much or too little ; but I think this 

 " reflector doublet " is likely to meet with the general approval 

 of the genuine outdoor worker, if it can be made and sold 

 at a reasonable price. 



Journ. Quekett Microscopical Club, Ser, 2, Vol. VIII. , I\o. 53, Noveraher 1903. 



