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 must be boiled for some 

 moments, when the organic matter will be entirely dissolved, 

 and the calcareous shells left free from impurity. They 

 oust 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 if 

 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. With a very 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. 



