102 THE MICROSCOPICAL NEWS. 
special work, and can not work in other fields, either from his 
nature or his surroundings, let him push up a round higher, if he 
can, to what his heart and mind cling to. No one need close his 
eye to some other’s truth. If such a union of work be undertaken 
by this society, in ten years it will have more effective systematic 
works than all the world of microscopists beside them. Vast 
volumes telling everything that can be known or needed now by 
so many studying in private. They are a necessity in laboratories. 
These volumes ought to be written from a great number of stand- 
points. ‘They must be written to economise the labour of teachers 
and students. It is now well established that the advancement of 
such a science as microscopy must be pushed forward by experi- 
ment in the progress of the world. And this society knows the 
same is true of each individual who seeks entrance at these 
beautiful gates of this infinite, varied, and sublime panorama of 
microscopic truth. To give the student the best results he ought 
to have these exhaustive guide-books in his delightsome journey. 
For every thing on this planet must pass in the microscopist’s field 
of view. 
THE ABBE ILLUMINATOR. 
R. J. GRUNOW, of New York, gives the following instructions 
for using this illuminator as constructed by him :— 
The apparatus consists of a lens-system of very wide angular 
aperture, two revolving diaphragm-plates, in conjunction with the 
plane and concave mirrors on the stand proper. The upper plane 
side of the lens-system should be almost even with the upper 
surface of the stage, so that it almost comes in contact with the 
slide. For observation by central light the diaphragm with central 
openings is used, viz., a narrower or wider diaphragm, according 
to the focal distance of the objective in use, the nature of the 
object-slide, and the intensity of the source of light. Generally, 
the narrowest diaphragm is to be recommended, as it gives suffi- 
cient light. Used without a diaphragm the condenser invariably 
gives an unsatisfactory illumination. 
By moving the diaphragm openings to the right or left, partly 
out of the optical axis, oblique illumination is obtained. 
For dark field illumination the star-shaped diaphragms are used 
instead of the aperture for central illumination, and always used in 
the central position. At the same time it is, however, preferable 
to reduce the aperture of all the high-power objectives, say from 
