72 PREPARATION AND MOUNTING 
the operator’s clothes may ensue. The nearly decolorized 
liquid must now be diluted with a considerable quantity of 
water, and the deposit allowed to subside, the supernatant 
liquid poured off, and the process of heating with sulphuric 
acid and addition of chlorate of potash repeated until the 
sulphuric acid occasion no further blackening; then the 
cleaning may be finished in the usual way by washing.” 
I have had many complaints from my friends that with 
all their care they have found nothing fit for mounting in . 
guano. This is readily accounted for by one fact, that not 
one sample in twenty of what is called guano in the market 
has an atom of guano init. Procure real guano, and you 
will get real returns. 
The fossil Infusoria (as they were formerly called) are now 
termed Diatomacez, and are found in various parts of the 
world; such as Bermuda earth, Berg-mehl from Norway, the 
deposit from Mourne Mountain in Ireland, &c. They are 
found in immense quantities, and afford the microscopist 
innumerable objects. The same treatment as that usually 
employed for the Diatomaceze must be followed with these 
deposits ; but as they are sometimes obtained in hard masses, 
disintegration is first necessary. To effect this, they are 
usually boiled for a short time in diluted liquor potassee, 
which will soon cause the mass to fall into a mud-like 
deposit. Water must then be immediately added, in order 
that all further action of the liquor potasse may be stopped, 
otherwise the objects searched for will be dissolved. For this 
reason it is necessary to understand what substance is being 
dealt with, because some deposits are much finer and are 
acted upon more readily than others. 
In mounting these objeets, some are so delicate that they 
are almost invisible when balsam is used with them; they 
are therefore usually mounted diy. Others, however, are 
much coarser, and may be mounted in balsam like the Diato- 
macez mentioned in Chapter IV. 
The common Infusoria cannot be mounted dry with any 
great success, though a few may be placed upon the glass 
