28 PRACTICAL MICROSCOPY. 



examine an object as he would if it were held in the hand, 

 and viewed by the naked eye that is, to turn it about in 

 every possible way towards a ray of light proceeding in a 

 fixed direction and so, without once losing sight either 

 of the light or the object, to observe its appearance when 

 illuminated by light of every degree of obliquity. 



This is the fundamental idea underlying its construction, 

 and in this consists the great difference between it and the 

 old forms of stand (although it has all the uses of the latter), 

 where the object remaining fixed, the only way in which its 

 illumination can be varied is by moving the illuminating 

 ray which, in the amount of the results it affords, and the 

 amount of time it consumes, is stated by the inventors to 

 be in every way inferior to the new one. 



An inspection of the engraving (Fig. 16) will show how 

 this idea is worked out. On the top of a strong pillar, to 

 which it is attached by a massive cradle-joint allowing of 

 inclination in a vertical plane, is fixed the arm carrying the 

 body, which latter is provided with rack adjustment, and a 

 new and improved fine adjustment, rendering unnecessary 

 the usual often unsatisfactory loose nose-piece. The stage 

 is so fixed with regard to the arm that the object when 

 lying upon it is in a line with the centre of the cradle-joint, 

 so that upon inclining the body the object moves with it, 

 and is presented at every possible vertical angle to a ray 

 proceeding to it from a given direction. The stage is of a 

 new and improved construction, being exceedingly thin 

 in fact the thinnest mechanical stage yet devised and is 

 capable of giving a complete rotation of the object. 



Beneath the stage swings the substage arm, concentric 

 with the object, and carrying the usual screw centering and 

 rack adjusting substage. 



Behind the substage arm is a strong bar, provided with a 

 dovetailed groove, into which the mirror bar slides. This 



