16 Wenham^ on a Binocular and Sincjle Microscope, 



lopmentj we hover at length in pleasing uncertainty at the 

 confines where the plant may be supposed to end and animal 

 life commence. The waistcoat- pocket may conceal our 

 menagerie^ and any locality furnish objects. For example, 

 at this season of the year, draw from the nearest hedge-side 

 ditch a rotten leaf. " Drop it again," the unknowing Avould 

 say in disgust, it is decomposing, and covered with a loath- 

 some-looking slime ; but remove a portion of this, and place 

 it under the microscope, and marvellous is the living host 

 displayed to view, consisting oi Diatomacea , Desmidia, Oscil- 

 latoria, Amceba, Rotifers, &c., all assembled together in 

 one dense crowd, perfect in beauty and cleanliness. An hour 

 may pass away unheeded, in the interest caused by observing 

 the movements of these creatures ; but greatly is that interest 

 enhanced by the aid of binocular vision ; they appear then 

 not as mere moving discs, but in all the reality due to life and 

 substance. 



The chief inconvenience of all the binocular microscopes 

 hitherto made, besides distorted or imperfect definition, has 

 been the necessity of a separate double body ; and the con- 

 stant trouble of shifting this for the single tube very much 

 limits their utility. There is also the difiiculty of cleaning 

 the prisms, and a liability to their derangement. In the in- 

 strument I have now to describe these objections do not 

 exist; for the effect, as a single microscope, is not in the 

 slightest degree impeded or interfered with, and by a touch 

 of the finger it is instantly converted into a binocular, or 

 back again. The annexed diagram A\dll explain the principle 

 of action ; a is the body of an ordinary microscope, moved 

 perpendicularly relative to the stage, with fine motion, &c., 

 precisely as it is commonly made. On the right-hand side, 

 in the neck at b, is cut a square hole, through which a prism, 

 c, having two reflecting surfaces, is made to slide, as close 

 behind the object-glass as possible. This prism is held by 

 the ends only in the sides of a small drawer, so that all the 

 four polished surfaces are accessible, and should slide in so 

 far that its edge may just reach the central Hue of the ob- 

 jective, and be draAvn back against a stop, so as to clear the 

 aperture of the same altogether, in which case the tube a acts 

 without impediment as a single microscope. When the 

 prism is thrust in more or less, it collects a portion of the 

 rays and reflects them to the opposite side of the tube, at 



D, where an opening is to be made large enough to admit 

 them all, under extreme conditions. Parallel with the direc- 

 tion of these rays is " grafted on " the supplementary tube 



E, with eye-pieces, &c.. and in size corresponding with the 



