175 



On a Small Portable Binocular Microscope and a Live Box. 



By 0. Rousselet. 



(Read October 28th, 1887.) 



I have been asked to bring before you a small microscope which 

 has been made to my order. 



I have long felt the want of a portable binocular for the purpose 

 of showing objects effectively when away from home, here at our 

 meetings for instance, without having to carry the very heavy weight 

 of the large instruments. The portable monocular microscope 

 did not, as a rule, allow me to exhibit objects to my satisfaction, 

 as a certain class of them are seen to so much greater advantage 

 with the binocular. 



Several forms of portable binocular have been made by various 

 makers, but they are mostly very elaborate, and consequently very 

 expensive. My aim has been to have it as simple as possible 

 without sacrificing any of its essential qualities ; the result is here 

 before you, and I may state that it certainly gives me every satis- 

 faction. There is necessarily a great deal about it that is old, and 

 I will therefore confine my remarks to a few of its principal points. 



The foot is the well-known sliding tripod ; the total length of 

 the tubes is eight inches, which is as short as they could be made 

 without causing a strain to the eyes ; the diameter of the tubes 

 is only a little over one inch, but the tubes carrying the eye-pieces 

 are wider at the top, and receive the B eye-pieces of my large 

 microscope ; this is of importance, because with small eyepieces 

 the field of view is greatly reduced, and the result is not so satis- 

 factory. The stage is simple, and has a broad but very thin sliding- 

 stage, which moves very smoothly. The condenser, also, belong- 

 ing to my large microscope fits in an adapter, which is screwed on 

 to the stage below, and it is focussed by a spiral motion, which 

 brings it up just above the stage if required. 



There is no tail-piece, the mirror being carried by a double- 

 jointed arm fixed at one corner of the stage, which allows it to be 

 brought above the stage for the illumination of opaque objects ; for 



