NOTES AND MEMORANDA. 
221 
my attention three or four weeks ago to a novel arrangement of a 
bull's-eye condensing lens, in connection with lamp and mirror. At 
first sight I was pleased with this method of illumination, and have 
given the idea considerable study, resulting in a slight change of 
the arrangement suggested for oblique light work, especially the 
resolution of difficult diatoms, such as Nos. 18, 19, and 20, of Holler's 
(balsam) Probe-Platte. The method will be found very superior, 
easily manipulated, and inexpensive. 
Cement for Glycerine Mounting. — Mr. Kitton, whose authority 
on this subject is admitted, gives the following piece of advice in a 
recent number of ' Science Gossip ' : — White lead in powder, red ditto 
in ditto, litharge in ditto, — equal parts of each. These are ground 
together with a little turpentine until thoroughly incorporated, then 
mix with gold size. The mixture should be sufficiently thin to work 
with the brush ; it is perhaps scarcely necessary to say that the edge 
of cover and slide should be free from moisture before applying the 
cement, and the first coat allowed to dry before putting on a second. 
The last can be applied somewhat thickly, or, as the japanners say, 
floated on. No more of the cement should be made than is required 
for present use, as it soon sets and becomes unworkable. To save 
the trouble of grinding, a stock of the mixture can be kept ready 
ground in a bottle. 
M. Cornil's Experiments on Staining Materials. — In a memoir 
devoted to the subject of amyloid degeneration of the kidney, liver, 
and spleen, which appears in a recent part of the ' Archives de 
Physiologic,' M. Cornil gives the results of his experiments with 
several new colouring matters. Two of these were methyl-aniline 
violets discovered by M. Lauth ; the third was a violet discovered 
by Dr. Hofmann, of Berlin. The preparations can be stained with 
these violets either when fresh or after being hardened in spirit ; and 
the colouring agents have this peculiarity, that certain tissues, as 
cartilage, decomposes them into a violet-red and a blue-violet, each 
of which becomes fixed in different elements of the tissue ; the hyaline 
matrix, for example, assuming a red colour, whilst the nuclei and 
cellules, as well as the cartilaginous capsules, become of a blue-violet 
tint. The normal tissues of the liver, kidney, and spleen, how- 
ever, do not decompose the violets, but, when amyloid degeneration 
is present, the degenerated and semi-transparent parts resembling 
colloid become of a violet-red, whilst the normal elements are tinted 
of a violet-blue, and thus a means equal, if not superior, to that of 
iodine is afforded, by which the changes may be followed. 
A Double Weight for Balsam Mounting is described in the 
' American Journal of Microscopy ' (No. 4), by the Eev. J. L. 
Zabriskie. He says, in mounting microscopic objects in balsam 
by the use of the hot-water bath, and a weight upon the covering glass 
— which process is slow, but sure — one usual difficulty to be overcome 
is the tendency of the cover to gradually slide away from its original 
central position. I do not know if this plan has been adopted before ; 
