08 ALBERT JOHANNSEN 
stage, interference figures may be obtained with low power objec- 
tives. This extends the usefulness of the Fedorow stage since it 
increases the rapidity with which determinations may be made in 
certain cases. 
To permit the rapid examination of a slide the writer attaches 
a bit of soft modeling-wax to one side of the stage and in it places 
the glass thread at such an angle that the lens globule is in the 
center of the field and rests against the cover-glass of the mineral 
section. The latter may now be shifted around the stage as much 
as is desired, bringing, successively, the different mineral constitu- 
ents under the lens, which remains undisturbed in the center of the 
field. Another method is to attach the rod of the lens to the rim 
of a cork ring, allowing it to project toward the center, and so tilted 
that it rests on the same plane as the bottom of the ring. This 
method better protects the delicate glass rod but is not quite so 
convenient, since both rock section and cork must be moved when 
it is desired to place different minerals in the center of the field. 
