224 THE HISTOEY AND DEVELOPMENT OF THE MICEOSCOPE 



micrometer screw only to the friction of the adjustment and, of 

 course, it is to be noted that the screw is not an extremely fine 

 one ; and the makers have evidence of the durability of the adjust- 

 ment, as after five years of use they have had no single instance of 

 its breakdown. The coarse adjustment is by diagonal rack and 

 pinion ; the draw-tube is graduated. It is beautifully made, and is 

 by no means an expensive instrument. We illustrate it in fig. 178. 



A well-made and remarkable little instrument of the class \\c 

 are considering is manufactured by Reichert, of Vienna, known as the 

 Austrian stand. It is illustrated in fig. 178A. It is the most 

 modified of all the microscopes we know based on the Continental 

 model ; it certainly approximates in several points to the English 

 type. It has a specially extended and steady horseshoe foot, and is 

 the only strict Continental form with the axis so high up. The re- 

 sult is that the body is balanced when in a horizontal position. The 

 coarse adjustment is by spiral rack and pinion with milled heads. 

 The fine adjustment is Reichert' s recent patent, giving extreme 

 delicacy to the movement, and having a movable pointer, i, for 

 reading divisions on the micrometer screw. It is provided with a 

 double rack draw-tube shown at B, it carries the Abbe condenser in a 

 sub-stage that focusses by a screw at the side, and centres by the 

 screw-heads, a, a!. In its most complete form it is remark; illy 

 low-priced, and certainly will meet a demand, especially as the 

 English method of compensation for wear and tear is adopted. 

 This, indeed, is the case with all but the lowest-priced instriim<>nt.s 

 of this maker, and we believe him to be the only Continental 

 manufacturer who has adopted the sprung slots and screws so long 

 used with success by English makers for compensating wear. We 

 should have suggested slotting the edges of the stage for sliding 

 the object-holder or ledge, but we learn from the maker that this 

 is to be done in all future instruments; all but the smallest stands 

 Reichert is willing to provide with English pattern sub-stages 

 fitted with centring screws of the standard size, and condensers \\\ < 

 mounted to suit these. 



Another instrument of the same class and general designation, 

 made by Messrs. Watson and Sons, and distinguished as ' G,' is shown 

 in fig. 179. It is identical in build with the C model, but the 

 stage is plain, and it has only a tube fitting for a sub-stage appa- 

 ratus; the workmanship is of the same order, the movements as 

 delicate and true, the adjustments as reliable, but the price is only 

 one-half that of the more complicated form. 



Amongst the same class of instruments must be placed another 

 by Messrs. Swift and Son. It is known as an ' Improved " Wale's " 

 Microscope.' 



Mr. George Wale, of America, devised in 1879 a plan of great 

 merit for the stands of microscopes. The ' limb ' which carries the body 

 and the stage, instead of being swung by pivots as ordinarily on 

 the two lateral supports (so that the balance of the microscope is 

 greatly altered when it is much inclined), has a circular groove cut 

 on either side, into which fits a circular ridge cast on the inner side 

 of each support, as shown in fig. 180. The two supports, each 



