64 PREPARATION AND MOUNTING 
consequently the first step should be to experiment on. 
various kinds. 
In gathering diatoms much labour is saved by judgment 
and care; hence it is desirable to get acquainted with them 
in their growing condition, so that when recognised upon 
the sand or other spots, they may be carefully removed by 
the aid of the spoon or small tin scoop before described. 
When growing upon alge or other plants, the plants and 
diatoms together may be carried home, in which case they 
must be simply drained and not washed or pressed, in order 
that the diatoms be not lost. As it is always desirable to 
examine the gathering on the ground, a “ Gairdner’s hand 
microscope” with powers from 80 to 200 diameters will be 
found very useful. The best gatherings are those which 
represent one species abundantly. ‘Those which are mixed 
may be rejected, unless they are seen to contain something 
valuable or important, as the object should be not so much 
to supply microscopical curiosities as to collect material which 
is available for the study of nature. 
The gathering when carried home should always be care- 
fully examined before anything is done with it; not only on 
account of the additional information thus acquired, but 
also because it often happens that a specimen should be 
mounted in fluid (see Chapter V.) in the condition in which 
it is gathered, as well as cleaned and mounted in balsam 
(Chapter IV.) and dry. 
Where the gathering is taken from sand, the whole may 
be shaken up in water as a preliminary operation, when 
much of the sand will be separated by its own weight. The 
lime test, however, should be applied; viz.—a small portion 
of hydrochloric acid, and if there be effervescence, it must be 
dissolved out by this means. From Algz and other weeds 
diatoms may be detached by agitating the whole together 
in a weak solution of nitrie acid—about one of pure acid to 
twenty or thirty of water, as it must be sufficiently weak to 
free the diatoms without destroying the matter to which 
they adhere. The diatoms may then be separated by 
