GG 
Journal of the 
secondly, a slightly different process which I have lately adopted, 
and which, in many cases, I find more convenient. 
Asuming, in the first place, that the cleansing of the diatoma- 
ceous material (full directions for which may be found in any book 
on microscopic manipulation) has been satisfactorily accomplished, 
the first thing to be done is to take up with a pipette some of the 
material from the bottom of the vessel where it has been allowed 
to settle, to deposit it on a clean slide, and to evaporate the water 
from it over the lamp. If the diatoms are plentiful, it may be 
sufficient to prepare two or three slides in this manner; when they 
are scarce, I frequently prepare fifteen or twenty. These are to 
be placed on the table, convenient to the left hand. I then take 
several perfectly clean slides (one for each species to be mounted), and 
slip them under the stand of the microscope on the left side to protect 
them from dust, leaving the ends projecting, for the purpose of 
drawing them out when requisite. One of the slides, with the 
material upon it, is then placed upon the stage, and examined till a 
good specimen is found, when a needle, moistened with the tongue, is 
brought under the object-glass (a one-inch) till the point is seen in 
the field of the microscope, when it is brought down on the slide 
and pushed along till it touches the diatom, which will generally 
adhere to it. The needle with the diatom is then raised slightly 
from the slide, and held a little above the stage, while with the 
left hand the slide is removed, and a clean one drawn from beneath 
the stand, and after being strongly breathed upon, placed on the 
stage with the centre in the middle of the field : the microscope is 
then focussed to the slide, and the operator having again brought 
the needle under observation, places it in contact with the slide, 
where the diatom usually remains, being held by the moisture 
from the breath. If the diatom has any foreign particles clinging 
to it, it should be moved about on the slide with the needle, 
when the water will usually separate the objectionable matter, 
which may then be drawn aside ; but if this be unsuccessful in 
cleaning the diatom, it should be rejected, unless it be a rare form. 
The slide is then removed from the stage and slid under the stand, 
till required for the addition of another diatom. If the material 
does not contain more than five or six species, the search for all of 
them may be carried on simultaneously, each specimen as found 
