:U2 THE A3IERICAN MONTHLY |Nov 



pond life, etc., ordinary -i-phite leuses of the ra[)id sym- 

 metrical type or the modeni auastigmats caii be advan- 

 tageously used, and by employing the 35mm. or 2()niin. 

 Zeiss Planar lenses an infinite amount of low or even 

 medium-power work can be done, for I have found that 

 the ordinary spiral rack and pinion attached to the camera 

 is sufficiently delicate for focussing with these powers. 



When, however, medium or high-power work is under- 

 taken, and especially when it is thought desirable to em- 

 ploy apochromatic objectives in conjunction witli com- 

 pensating or projection eyepieces, a special form of ac- 

 cessory apparatus is essential. Messrs. Watson and Sons 

 have constructed this from my designs at a most season- 

 able cost, and, like all the productions of that firm, the 

 workmanship is throughout excellent. It consists chiefly 

 of a body tube of Continental length, supported upon a 

 metal base, with spiral rack-and-pinion coarse adjust- 

 ment, and a delicate side-lever fine adjustment, with its 

 milled head conveniently placed upon the right side of 

 the instrument. Its optical axis is only 2^ in. high. 



When this apparatus is in use, the stage is pushed up 

 to a convenient distance from the objective employed, and 

 clamped. The object is tlien focussed in the usual way, 

 the camera front racked up so that its light-tight cap is 

 inserted within another larger cap upon the body tube, 

 which may or may not carry an eyepiece, and the expo- 

 sure made. 



It will be seen that the limb and body tube of the mi- 

 croscope is not attached to the stage, so that the former 

 can be removed and dispensed with when only low-power 

 work is undertaken. With this small and compact appa- 

 ratus it is possible to photograph any object varying in 

 size from, say, the wing of a large dragon-fly to a bacte- 

 rium or bacillus. 



By keeping the axis of the optical system low — only 2| in. 

 from the base — the size of the rest of the apparatus is nee- 



