ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 637 



Zeiss's Ila. Microscope. — Dr. C. Zeiss's new stand lla. (fig. 96), 

 resembles his No. II. in general form and dimensions, but differs from 

 it in having the fine-adjustment described in this Journal, 1887, p, 150. 

 The upper part is not made to rotate about the optic axis as in No. IL, 

 but there is instead a disc of vulcanite which rotates on the stage ; this 

 is centered by means of two screws working against springs, one of 

 which is shown in the figure immediately below the right-hand clip. 

 The play of the centeriug screws is said to be sufficient to answer the 

 purpose of a mechanical stage with high powers. The stage is large 

 enough for cultivation plates. The Microscope inclines and can be 

 clamped in any position. 



The Abbe illuminator is provided with an Iris-diaphragm. The 

 optical system (1-40 N.A.) is fixed in a brass holder which fits 

 into a corresponding sliding socket, so that it may be withdrawn 

 without difficulty from below, and replaced by a cylinder diaphragm 

 or any other appliance similarly fitted (photographic condenser, illu- 

 minator for monochromatic light, ifticrospectral - objective, spectral- 

 polarizer, &c.). 



The height of the stage above the base of the stand is reduced as far 

 as possible fQr two reasons : (1) in order that the hands of the observer 

 while manipulating the object may rest easily upon the stage, which is 

 not the case with the stands of larger dimensions ; (2) because a low 

 stand is more convenient for most observers, and makes the instrument 

 more portable. 



Babuchin's Microscope. — This stand (fig. 97), is made by Dr. Zeiss, 

 after the design of the Moscow histologist Prof. A. Babuchin. 



The Abbe illuminator has almost the form adopted by M. Nachet ; 

 the optical system, fixed in a holder, can be inserted from above into the 

 carrier, which can be screwed downwards and swung out to the left. 

 By these means the lenses are most easily interchanged with those of 

 different aperture, or with a cylinder diaphragm, or polarizer. Below 

 the condenser is a slot made to rotate about the optic axis in which the 

 iris-diaphragm with rack and pinion is inserted; for oblique illumina- 

 tion it can be adjusted excentrically. The illuminator is moved in the 

 optic axis, not, as is generally the case, by rack and pinion, but by 

 a screw fitted to the left under side of the stage, which gives a slower 

 and more exact motion. When the screw has been turned until the 

 illuminator has reached the lowest point, a further turn swings it out to 

 the left. 



A specially large mirror is fixed to a sliding carrier by which it may 

 be raised or lowered, or, when the condenser is swung to one side, fixed 

 in any oblique position. The stage, which is not made to rotate or 

 move, is large enough for cultivation plates. 



The upper part of the stand is attached by a hinge-joint to a short 

 pillar, which slides in a tube on the base, so that it can be drawn out 

 and clamped. This renders it possible to lower the stage as much as is 

 required for convenient manipulation or portability, or to increase the 

 height of the stage and stand if this is required for application to a 

 photographic camera, or to admit a larger substage, &c. The height of 

 the stand can be varied between 200 and 230 mm., and that of the stage 

 from 105 to 135 mm. It has the adapter for changing objectives which 

 was described in this Journal, 1887, p. 646, and the fine-adjustment 

 described p. 150. 



