THe Microscope. 367 
silvered, and graduated in degrees for the measurement of the 
angles of crystals. This is another luxury, and not a very de- 
sirable one, as it is seldom used by any microscopist unless he is 
‘pursuing the special study of crystallography. Ido not know 
of any stand costing less than one hundred dollars whose stage 
has these graduations. The ambitious beginner need not be dis- 
contented because he is unable to have this rotating, graduated 
accessory, for without it he may do excellent work, and make 
many discoveries so far as he is concerned, whether the scientific 
world previously knew them or not. 
The stage should always be firm and steady under pressure, 
but the pressure should be applied judiciously. All microscope 
stages, even those on the best stands by Mr Bulloch, Mr Zent- 
mayer and others, will respond to the pressure of the thumbs, 
and be sufficiently depressed to carry the ebject out of the focus 
of a medium power objective. The stage that responds the least 
is the best, put perfection in this regard seems beyond our reach. 
Neither is it absolutely essential. The thumbs never press on 
the stage, unless they are delirious. No heavy objects are placed 
there. No sane microscopist would put a cobble stone on his 
stage. The optician may be trusted to give us the best that the 
conditions of the problem will allow, and the amateur purchaser 
need never test the stiffness of the stage by the weight of his 
arms and shoulders transmitted through his thumbs. If he 
does, he will deserve to test the weight of the dealer’s arms and 
shoulders transmitted through a club. 
The stage should be as thin as is consistent with the proper 
stiffness and steadiness. This is needed to allow for certain 
effects of illumination. It sometimes happens that an object 
must be studied by what is called oblique light, that is, the mir- 
ror must beso arranged below and to one side of the object, 
that the reflected light shall impinge upon it obliquely, and oc- 
casionally very great obliquity is needed, which can be obtained 
only when the stage is thin, since a thick stage and a conse- 
quently deep aperture in the centre, would prevent very oblique 
rays from passing through to the object. Many “Students’” 
stands are faulty in this respect, the makers seeming to think 
that since oblique light is only needed in somewhat advanced 
work, the beginner will not care for it. But I believe in offer- 
ing the beginner advantages which he may not at first appreci- 
