Improved Metallurgical Microscope. By Walter Rosenhain. 149 



•comes upon the fine-adjustment is carried centrally, while any 

 slight irregularities of bearing surfaces or motion are not magnified, 

 as in the ordinary construction, by a considerable overhang of the 

 moving parts ; the resulting fine-focusing motion is consequently 

 remarkable for a crisp decisiveness and absence of all wavering 

 which is most refreshing in use, while the favourable conditions of 

 wear under the circumstances described should go far to lengthen 

 the life of the more delicate parts. 



The stage itself combines all the advantages of a simple flat 

 stage, free from all encumbrances upon its surface, with complete 

 mechanical movements and complete rotation about the optic axis. 

 This result is secured by placing the mechanical stage movements 

 below the stage plate itself; the movements themselves consist of 

 two broad dovetailed slides, at right-angles to one another, actuated 

 hy rack-and-pinion movements controlled by milled heads fixed 

 below. Even when an inch of mechanical movement has been used, 

 the stage may still be completely rotated. The author regards a 

 stage capable of such complete rotation and free from all encum- 

 brances upon its surface as almost essential to the better class of 

 metallurgical work ; the interpretation of the microscopic images 

 is often only possible by the use of various forms of oblique 

 illumination, some of which will be mentioned below, and when 

 these are applied it is usually necessary to test the effect of vary- 

 ing orientation of the specimen by rotating the stage ; under such 

 circumstances it leads to much annoyance and loss of time to find 

 that the rotation is blocked, or the light obscured by a projecting 

 fitting on the stage, just at the point which it is most important to 

 observe. Another advantage of the arrangement of movements 

 adopted in the present instrument is to be found in the fact that 

 all the milled heads regulating the focus and the position of the 

 specimen lie within easy reach of one hand ; thus it is quite easy 

 to use one of the mechanical movements of the stage with the 

 thumb and one finger, while keeping the object in focus by moving 

 the fine-adjustment with the little finger of the same hand, par- 

 ticularly as the wrist may rest comfortably on the table if the 

 instrument is not too much inclined. 



In the instrument as at present constructed the rotation of the 

 stage is provided with neither centring screws nor mechanical 

 movement, a firm clamp, acting in any position, being alone pro- 

 vided. The centring screws have been omitted in order to 

 economise space, a centring nose-piece being provided as an 

 integral part of the body-tube, while the author does not consider 

 that mechanical rotation of the stage is essential for metallurgical 

 purposes. 



The Body. — As has already been indicated, the tube of the 

 Microscope is rigidly attached to the limb, all focusing motions 

 •being carried out by means of the stage. A considerable increase of 



