74 PREPARATION AND MOUNTING 
they sink and are cast away with the refuse sand. On this 
account it is preferable to take the trouble of searching 
certain soundings under the microscope, using the camel- 
hair pencil, or some other contrivance before mentioned, to 
extract those objects which are required.* To clean the 
Foraminifera, Professor Williamson advises the transfer of 
the specimens to an evaporating dish containing a weak 
solution of caustic potash. This mnst be boiled for some 
moments, when the organic matter will be entirely dissolved, 
and the calcareous shells left free from impurity. They 
saust now be well washed in water, so that all alkaline 
matter may be entirely removed. 
If the specimens are in mud, we must proceed in a dif- 
ferent way :—Stir up the whole mass in water, and allow 
it to stand until the heavier portion has sunk to the bottom; 
the water may then be poured off and examined to see it 
there are any objects contained in it. This process must be 
repeated until the water come off quite clear, when (if the 
search is for Foraminifera only) the solution of caustic 
potash may be used as before mentioned. However the 
soundings, &c., are cleaned, it is necessary to assort them 
* In searching any earth or sounding in order to take objects there- 
from, no method presents the same facilities as the use of the finest 
camel-hair pencil, to which, after being drawn through the lips, any 
forms will adhere, and yet be readily detached upon the slide. After 
a little practice the smallest objects may be separated. Captain Lang, 
however, stated that he used a single hair or bristle dipped into gum 
and dried, after which a slight breath would restore its adhesive 
power. Withavery fine hair pencil during one winter I mounted 
about 1,400 slides, each one picked out of sea soundings, many of 
which had from six to twelve specimens upon them. The readiness 
with which the objects adhered to the point and were detached when 
required, rendered the process much more pleasant than using a bristle 
with gum. As to the numbers of objects to be taken from any sound- 
ing, even imagination often fails. Plaucus, it is said, collected 6,000 
shells of Foraminifera from an ounce of sand from the shore of the 
Adriatic. Soldani collected from less than an ounce and a half of 
rock from the hills of the Casciana, in Tuscany, 10,454 fossil shells. 
Several of these were so minute that 500 weighed only a grain. And 
D’Orbigny found 3,840,000 specimens in an ounce of sand from the 
shores of the Antilles. 
