156 
CORRESPONDENCE. 
with any of them in the failing that he deprecates in others,* and so 
the cavil, embittered by feelings of rival interest, spreads to all who 
use object-glasses. 
My attention has been called to a letter from Mr. Stodder, appear- 
ing in the ‘ Cincinnati Medical News ’ for July last, wherein he 
attempts to claim pre-eminence for Mr. Tolies, and asserts that all 
recent improvements have been taken from him. I cannot reply in 
any of the American journals, particularly as the letter in question is 
such a manifest puff of Mr. Tolies’ object-glasses, from one professedly 
his agent, that I am surprised at its insertion as a scientific article. Not 
to lose the chance that now offers, in the present small-angle con- 
troversy, Mr. Tolies is there boldly put forward as the maker of the 
best object-glasses in the world. It is imputed that Messrs. Powell 
and Lealand have based their recent improvements on the fact of 
having seen Mr. Tolies’ four-combination ^th (belonging to Mr. Crisp). 
As these gentlemen make it a rule never to answer insinuations against 
themselves, I venture to state that I have examined their new glass, 
as well as the notorious ^th, and am in a position to say that they 
have not copied, and further, that they also consider this much- 
vaunted object-glass not a subject for imitation. 
The four-system combination is claimed by Mr. Tolies as his in- 
vention, but it is no novelty. Andrew Eoss made a great number of 
them about twenty years ago. Mr. Tolies’ agent (Mr. Stodder) refers 
to me with his characteristic rancour as claiming arrangements belong- 
ing to others. That in which one single front works both wet and 
dry is not “ copied from America,” neither do I claim it, as many of 
the four-combination lenses just referred to by the late Andrew Eoss 
having a single front, work equally well both wet and dry. The 
effect partly depends upon the perfection of the correction, and 
whether there is sufficient range in the adjustment to enable the 
lenses to occupy a closer position than usual. 
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. This was tried 
and suggested by myself years ago : I then formed a high opinion of 
the arrangement, and consequently described and figured it in my 
essay “ On the Construction of Object-glasses,” page 172 of the 
first vol. of this Journal (March, 1869), which makers of object- 
glasses may have noticed. I am gratified to find that my idea of its 
merits is confirmed by practice, and that it will find a place amongst 
improvements in the history of the object-glass. 
The real question at issue at present, viz. the superior value of 
small apertures versus large ones on a certain class of objects, appears 
* I shall not revive the controversy of the theory of dry and immersion 
apertures ; but in referring to my “ Keflex Illuminator ” Mr. Mayall has simply 
mistaken the action as described by me. All rays are made to fall at such an 
angle on the top surface of the slide (not the cover), that they are totally reflected, 
and the only light that can pass through is at the contact points of the object, 
vhich adhere to that surface. The total reflexion is the same irrespective of any 
aperture of object-glass, and the field equally dark whether this is used with 
water between the front lens or not. 
