TuLKj on Cleaning and Preparing Diatoms. 
5 
mounted in the same manner^ of course omitting such of 
the detailed operations as are evidently unnecessary. 
Diatoms are readily collected from the mud when the 
latter has only a few inches or no water at all over it^ pro- 
vided only it is in a moist state ; and the plan I adopts and 
which was suggested to me by my friend Mr. Currie_, of 
Addlestone^ is gently and lightly to detach the diatomaceous 
stratum lying upon the surface of the mud by the aid of a small^ 
thin^ old_, silver salt-spoon, having its bowl-edge in the same 
plane as its shank ; thus, the lighter and smaller the spoon is 
the more valuable it will be found to be. If carefully per- 
formed, by this operation a small portion of the diatomaceous 
stratum, in some cases entirely, in others almost entirely, 
free from siliceous particles, will be lifted, and may be trans- 
ferred into the collecting bottle. It is as well to have in the 
bottle some water, into which the spoon can be immersed, 
when the forms will readily diffuse themselves in the fluid. 
Or if the mud from which the collecting is to be made has 
no water over it, but yet is moist, another method of gather- 
ing the forms may be adopted, namely, to roll over the 
diatomaceous stratum a rather large camel-hair brush, 
when the frustules will become entangled in the hairs of the 
brush, and may be separated from them by immersion in the 
water in the collecting bottle. Having by either of these 
means obtained a sufficient quantity of the material, and 
suppose it to consist of forms not quite clean, the next 
operation is to strain it through a piece of thin silk gauze, 
by which means any large pieces of vegetable matter are got 
rid of. It should then be placed in a small, unglazed saucer, 
with about \" of water above it, and exposed for a few 
hours to the influence of the sunlight, which in many 
instances will cause the diatoms, which may be known by 
their brown colour, to rise to the surface of the impurities ; 
and they may then be separated by means of a camel-hair brush 
rolled over them in the manner already described. Also in 
this case the diatoms may frequently be obtained absolutely 
pure, and requiring no further preparation than boiling in 
nitric acid and washing in clean water. However, it may be 
found that they have not risen to the surface of the impurities, 
or if they have, they cannot be collected by the brush free from 
silica, in either of which cases the whole of the gathering 
in the saucer maybe transferred into a large, wide-mouthed 
bottle, six inches high and two and a quarter inches diameter 
inside, a few drops of nitric acid added to kill the forms, and 
the bottle two thirds filled with clean, it need not be distilled, 
water, and the whole well shaken. The mass is then allowed 
