CORRESPONDENCE. 
*295 
my paper in tlie May number of the ‘ News’ (will Mr. Wenham have 
that copied in this Journal, that his readers may know the whole story?). 
I there give the evidence that T. Ross saw Tolies’ work before he put 
immersion fronts to his objectives. Will Mr. Wenham say that 
Andrew Ross ever made immersion objectives intentionally ? Many dry 
objectives will accidentally work immersion ; Mr. Wenham himself 
explains why. That is a different thing from making them so inten- 
tionally. So also many object-glasses may (as Mr. Wenham says of 
A. Ross’s) work “ equally well ” both ways ; but both ways may be 
very poor. 
“ Having shown that the four-combination system is no novelty, I 
must say the same of the doublet or duplex front now claimed by 
Mr. Tolies as the great improvement of his lenses.” I challenge Mr. 
Wenham, or anyone else — I rather like that formula — to produce any 
evidence that Mr. Tolies has ever made any claim whatever about the 
duplex front. Mr. Wenham has committed the mistake of thinking 
that the duplex and the four-system are two different things, whereas 
they are but two terms, either correct, for the same thing, one being 
more euphonious than the other. Of course Mr. Tolies has not done 
the ludicrous thing of claiming a name as an improvement of his 
lenses ! 
But Mr. Wenham adds of the duplex, “ This w T as suggested by 
myself years ago.” Indeed ! Who is “ claiming arrangements be- 
longing to another ” now ? I am authorized to say that the “ duplex 
front ” is unlike anything that Mr. Wenham has published ; has a 
different optical function to perform, and must produce other results. 
So Mr. Wenham must reserve for some future time his “gratifi- 
cation ” for learning that his suggestion is coming into practical use, 
by anything that Mr. Tolies has made. 
So much for Mr. Wenham’s observations on my paper. I have 
pointed out some eight or ten errors in his. I regret the necessity 
of doing so, but it is due to history that they should not pass 
unchallenged, for they would be accepted as true otherwise. 
Charles Stodder. 
Mr. Wenham’s Reflex Illuminator. 
To the Editor of the ‘ Monthly Microscopical Journal .’ 
Boston, Mass., September 23, 1S75. 
Dear Sir, — As the reflex illuminator of Mr. Wenham promises to 
be one of the most valuable and useful of all the recently invented 
adjuncts of the microscope, destined, I believe, to receive more atten- 
tion than it yet has, I wish to ask Mr. Wenham, through this Journal, 
a brief explanation, for the benefit of all microscopists, of his note, 
page 156 of the September number. 
Mr. Wenham writes, “ The total reflexion is the same irrespective 
of any aperture of object-glass, and the field equally dark whether 
