224 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



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 I lie makers h;ive evidence of the durability of the adjust- 

 ment, as .-il'ter live 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 

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



A well-made and remarkable little instrument of the class we 

 are ei Hindering 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 line adjustment is Reichert's recent patent, giving extreme 

 delicacy to the movement, and having a movable pointer, /. 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'. In its most complete form it is remarkably 

 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 instruments 

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

 manufacturer who has adopted the sprung slots and screws so Liny 

 used with success by English makers for compensating wear. We 

 should ha\e siigge>1ed slotting the edges of the stage for sliding 

 the object -holder or led^e. but \velearnfrom the maker that this 

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

 Heichert is willing to provide with English pattern sub- stages 

 titled \\jili centring screws of the standard si/e. and condensers a re 

 mounted to suit these. 



Another instrumenl of the same class and general designation, 

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

 in lig. 1 7U. It is identical in build with the C model, but the 

 stage is plain, and it has only a tube lilting fora sub-stage appa- 

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

 delicate and true, the adjustments as reliable, but 1 he price is only 

 one half I hat of t he more com | il icat ed form. 



Amongst the same class of instruments must be placed another 

 l'\ Messrs. Swift and Son. Il is kno\\n asan ' Improved "Wale's" 

 M icroscope.' 



Mr. < ieorge Wale, of America. de\ ised in 1S7!> a plan of great 

 merit fort he stands of microscopes. The limb ' \\ Inch carries the body 

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

 the two lateral Supports (so thai the balance of the microscope is 



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

 on eit her side, into \\ hich lits a circular ridge cast on t he inner side 

 of each support, as shown in lig. ISO. The two supports, each 



