248 HOW TO SEE WITH THE MICROSCOPE. 



adjustment for the forearm, while the right hand, being" 

 thus so nicely supported, is enabled to manipulate the 

 mirror with almost mathematical precision. At the 

 first, as might easily be supposed, the sharp edges of the 

 table and drawers will be a source of some little incon- 

 venience. This can be remedied by placing a pair of 

 napkins thereon; but the better way is to endure this 

 slight annoyance for a little time, when the forearm 

 will be found to have adapted itself to the situation. 

 The position thus described we have represented as far 

 as possible in the frontispiece, using such furniture as 

 was at hand in the photographer's gallery 



This pose can be varied at times by bringing the left 

 knee in use so that it may support the left elbow. Thus 

 we get three rests tor the left arm, and sometimes we 

 get the shank of the right foot on to the front round 

 of the chair, spreading the knee open a bit and wedging 

 it under the riofht hand draw. Other little chancres are 



O O 



practicable and need not be detailed here. 



Of all the manipulations connected with the use of 

 the higher powers, the adjustment of the objective (sup- 

 posing, of course, that it is a good one, one that Avill 

 respond to the collar adjustment), is of paramount im 

 portance. For reasons previously stated, two elements 

 are involved, namely, the behavior of the object glass 

 and the education of the eye ; and here the use of the 

 diatommeca3 is imperative. We have insisted oil this 

 for years. These little organisms are the most con- 

 venient, and then, again, any little deviation from the 

 perfect correction of the objective is sure to " stick out " 



