1878. ] Microscopy. . 839 
Prof. William Lighton, of Ottumwa, Iowa, described a “ New . 
Arrangement for Dark-field Illumination,” in which an effect 
comparable to that of a spot-lens was produced by placing above 
the eye-piece a diaphragm with an aperture of y inch, decentered 
so as to cut off the central cone of light ordinarily used by the 
eye. This effect is produced most perfectly with an achromatic 
eye-piece. He also described “An Analyzing Eye-piece,” con- 
taining a bundle of reflecting plates arranged at a polarizing angle. 
r. R. H. Ward gave an account of recent improvements in 
s Biscoe’s Section Cutter.” The principles of construction of this 
machine, which is said to have been founded on some German 
inventions, were fully explained.in the NATURALIST for Jan., 1874. 
As now made by Mr. chrauer, of New aeit it has a central 
cylinder and plunger like other section cutters. In this way the 
object to be cut is arranged with great facility, while the thick- 
ness of the sections 5 regulated with ease and precision by the 
screws that ‘support the carriage. his arrangement has a 
capacity for easy ja good work that is almost incredible to per- 
sons accustomed to use other contrivances. 
A communication on “Seiler’s Section Cutter,”. by Wm. H. 
Walmsley, was read by title in the absence of its author. 
A paper on “ Epithelium” was read by Dr. W. H. Atkinson, 
rk. 
After referring the eon 4 publishing proceedings to the 
executive committee, and pass an appropriate vote of thanks 
or favors received at Te aapnlis. the Society adjourned until 
the Buffalo meetin 
New Forms oF iouctun The cement which is essential to 
these processes, and which I regard as the most important work- 
ing material of the microscopist, is shellac varnish prepared in 
the following simple manner: The white purified gum shellac is 
dissolved in alcohol and filtered through cotton one or more 
times until it is quite clear and transparent. As the filtering is to 
most persons a somewhat difficult operation, they had better per- 
haps let the druggist make this preparation for them. With this 
cement I build up a cell as deep and perhaps as quickly as one 
can be made with a curtain ring, painted up as it usually is. As 
much as one or two drops can be put ona slide with a brush, 
using the turn-table, and then slowly worked up into a narrow 
‘ring with the point of a small knife-blade held on the turning | 
Slide. When this has dried a day or two, another layer can be 
great economy both of time and abor. These rings being í trans- 
_ parent are admirably adapted for opaque mountings, with which 
_ it is desired to use the Lieberkihn. 
