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Microscopical Society of Victoria. 
On Mounting Diatoms in Symmetrical Groups. 
By W. M. Bale. 
[Head 26th August, 1880.] 
As the subject of mounting diatoms in symmetrical groups has 
been recently before the Society, a few further remarks in reference 
thereto may be acceptable to any members who may intend trying 
their hands at this particular branch of microscopy. Perhaps no 
objects (with the exception of microscopic writing and engraving) 
cause so much surprise to the beginner as those slides in which a 
spot so small that its exact shape can scarcely be distinguished 
with the naked eye, is found to consist of a number of minute 
diatoms arranged in a design of perfect symmetry. Yet there is 
no special diliiculty in the process, and all that is requisite is a 
firm hand, a good stock of patience, and a little practice, without 
which no great amount of success is likely to be attained in anv 
branch of microscopic art. 
In the first part of my paper read in November, 1879, I have 
described in detail the mode of arranging the diatoms on the slide, 
and if the valves are very small and flat, and are to be mounted 
dry, it will be sufficient to follow the directions there given, after¬ 
wards surrounding them with a thin cell and applying a cover \ 
but large or uneven diatoms mounted thus are liable to leave the 
slide at the least jar, and must therefore be attached with some 
cement; while any diatoms which are to be mounted in balsam 
must be fixed to the slide or cover with a cement not soluble in 
the turpentine contained therein. In these cases, a minute drop 
of clear gum may be deposited near the centre of a clean slide, 
and thinned with a drop or two of water, the whole being spread 
backwards and forwards over the slide with the blade of a knife 
till none appears to be left in the centre where the objects are to 
be placed. The diatoms are then arranged on the slide in the 
usual manner after breathing on it, and when dry they will adhere 
to its surface, after which they may be covered in the ordinary 
way. With dry mounts especial care must be taken that the 
merest invisible film of gum remains on the slide, the appearance 
of the diatoms being spoiled if they are saturated with gum or any 
similar material. 
For transferring the valves from one slide to another the best 
implements are mounted bristles, of which two should be at hand, 
a 2 
