( 259 ) 
COEKESPONDENCE* 
On a New Form of Object-g-lass. 
To the President of the London Microscopical Society. 
Rue Mazaeine, Paris. 
Sir, — We have the honour (Mr. Thuet, ingenieur-opticien, of 
Paris, 19, Eue Mazarine, and I, microscopist, of 113, Chaussee du 
Maine) to offer you two new mechanical appliances for objectives 
corrected for immersion. These appliances have suggested them- 
selves to us from our desire to facilitate the cleaning of the optical 
arrangement. Even using the immersion front with glycerine, it is 
seldom that moisture does not pass the front lens into the correcting 
lenses, and thus the frequent cleaning of the objective. We submit 
our systems to the Society, and we will conform to the decision that 
may be passed upon this new idea. 
* Several letters are " crushed out " of this number, but will appear in onr next. 
