134 MEMORANDA. 



The Binocular Microscope.— Having, in my desire to keep 

 up with the progress of improvement, procured a microscope 

 constructed on the principle of Mr. Wenham's last invention 

 (Transactions, p. 15), I feel it my duty to declare that I have 

 fully verified every statement made in the paper alluded to 

 with regard to " the new combined binocular and single 

 microscope." I should call it an w^i^er-statement. In short, 

 all I said of the former one (Memoranda, p. 66) will apply 

 to the latter with redoubled force. That was excellent, but 

 this is super -Q-aceWeni ! 



The microscopic world is deeply indebted to Mr. "Wen- 

 ham ; but he very liberally awards me a share in the merit ; 

 for, in a letter to me, he says : — "Whatever I may have done 

 in the invention, great credit is due to you for having started 

 the thing, and brought it into notice ; for, such would have 

 been my own apathy, and that of the makers, that probably 

 the only one ever made would have been that in my own 

 possession. There is not one person out of a thousand that 

 would have had the ' pluck^ to order a thing of this kind 

 that he had never seen !" 



Mr. Wenham's account of his instrument (in the January 

 number) is so complete, that very little remains to be said in 

 the way of explanation ; nevertheless, I should like to add a 

 few words for the benefit of those who may not perfectly un- 

 derstand why the last Binocular Microscope is so decidedly 

 preferable to the former ones. Mr. Wenham has explained 

 the reason to be that, instead of the whole light having to 

 undergo prismatic refraction, as in the former instruments, 

 one half is now simply transmitted in the usual manner; but 

 probably very few, even of experienced microscopists are 

 aware how very nearly the half of an object-glass comes up 

 to a whole one in actual performance, especially in the lower 

 powers. This is beautifully illustrated by an eclipse of the 

 sun; for it has been truly observed, that though a total 

 eclipse is everything, a partial one is nothing. Even when 

 a full half or more of the sun's disc is concealed, no one 

 would suppose, from looking at the prospect around him, 

 that anything was wrong with the sun. This may also be 

 shown in the case of " the combined binocular and single 

 microscope," by the following experiment. 



Get some friend, for \h% first time, to look through the 

 Binocular, haAdng previously placed a small opaque disc be- 

 neath the cap of the left-hand eye-piece, the prism being 

 withdrav.n. He will then see the object, whatever it be, 

 in the usual way ; and will probably say, " Beautiful I" 

 " splendid !" or words to that eflect. Then, while he is 



