Answers to Queries. oy 
321.—Cleaning Diatoms.—The sediment must be poured into 
an evaporating dish, with sufficient pure Sulphuric Acid to cover 
it, and the vessel gradually and carefully heated. To avoid any 
chance of explosion, so soon as the white fumes of the acid 
appear, Bichromate of Potash should be added in small portions, 
and when the green colour formed by its reaction on the organic 
matter begins to assume a yellowish tint, a few drops of Hydro- 
chloric Acid must be added. ‘The liquid should now be set aside 
to cool, when the deposit must be finally washed as has been 
already described. ‘There is another process which is substantially 
the same as the one already described, but with this exception ; 
Sulphuric Acid is substituted for Nitric Acid, and crystals of 
Nitrate of Potash for those of Bichromate. This has, I think, 
some advantages over the first-mentioned process, and, as I 
invariably follow it, I have the greatest confidence in recommending 
it. When a recent gathering is nearly pure, all that is required is 
to burn them on a platinum plate over a glass flame, the organic 
matter being quickly carbonised, while the beautiful siliceous 
shields alone remain unaffected. AW. G: 
319.—Sections of Teeth and Bone.—Sections of teeth often 
show very well when mounted in liquid balsam, thinned with 
benzole. With done sections it is different ; the canaliculi disappear, 
and the lacunz look like ghosts when thus treated. There can 
be no better way of mounting bone sections than that given by 
Carpenter (“the Microscope,” etc.), and, in almost the same words, 
by Hogg. He (Carpenter) says :—‘“‘ A quantity of balsam, propor- 
tioned to the size of the specimen, is to be spread upon a glass 
slip, and to be rendered stiffer by boiling (baking in a moderate 
heat ?) until it becomes nearly solid when cold; the same is to be 
done with the thin glass cover; next, the specimen being placed 
on the balsamed surface of the slide, and being overlaid by the 
balsamed cover, such a degree of warmth is to be applied as will 
suffice to liquify the balsam without causing it to flow freely, and 
the glass cover is then to be quickly pressed down, and the slide 
to be rapidly cooled so as to give as little time as possible 
for the penetration of the liquified balsam into the lacunar 
system.” Carpenter adds that the same method may be employed 
in mounting sections of teeth, and so, no doubt, it may, 
and with advantage; but with dove, unless the balsam can be 
kept out of the lacunz and canaliculi, they are better polished 
and mounted dry. It is mere misery to see one’s carefully-rubbed- 
down specimens being spoiled by the balsam creeping in. I have 
mounted scores of bone sections in Carpenter’s way, and never 
