522 .PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



neck. Make a cylinder of wood that will just fit the inside of the 

 neck. Fold some filter paper down and around this cylinder so that 

 it will just fit tightly into the neck of the bottle, to the bottom of 

 which it is forced, and the cylinder of wood withdrawn, leaving the 

 filter in its place. Now moisten the filter carefully with a few drops 

 of bisulphide of carbon, and a piece of stick phosphorus from a 

 quarter to three-eighths of an inch long should be placed in the filter, 

 and the bottle corked. The vapour of the bisulphide instantly acts 

 on the phosphorus, and in about half an hour it will be in a fluid 

 state remaining in the filter. By releasing the cork and taking 

 hold of the filter tube with a pair of pliers and slowly drawing it 

 upwards a partial vacuum is formed beneath it, and the pressure of 

 the air on the surface of the fluid phosphorus forces it through the 

 filter, leaving the now brilliant fluid in the bottle. 



With care, rapidity, and firmness withdraw the filter and plunge 

 instantly into a vessel of water close at hand. 



In mounting we assume that the best course as advised above 

 has been adopted, and that the diatoms to be mounted are either- 

 arranged or diffused upon the cover-glass. 



Make a ring upon the slip of glue and honey cement used 

 warm and allowed to cool. It is now a stiff jelly. Lay the cover 

 in its place, with the diatoms downwards, touching the ring at one 

 side, but raised by a fine wire on the side next the operator. A 

 pipette may also be used made of glass tubing an eighth of an inch in 

 external diameter, drawn to a fine point at one end, and somewhat 

 enlarged at the other, and to which an indiarubber cap or nipple is 

 fastened airtight. This pipette must be passed through the centre 

 of a cork fitting the bottle of phosphorus solution, and the fine end 

 should plunge into the fluid and nearly touch the bottom of the bottle. 

 By squeezing the rubber cap before the insertion of the pipette and 

 releasing it after the point is well down, a small quantity of phos- 

 phorus rises in the pipette. It is withdrawn and inserted rapidly 

 beneath the tilted end of the cover ; the slightest pressure on the 

 cap ejects enough phosphorus to fill the space between the cover 

 and the slide ; gently and firmly press it down and ring it with warm 

 glue and honey. 



In half an hour points of superfluous phosphorus may have 

 exuded. With a pair of tweezers wet a piece of blotting-paper with 

 bisulphide and absorb these away, plunging the paper at once into 

 water. The slides should now be put aside for a day or two, then 

 they may receive two or three ring-coatings of gold-size, and finally 

 be finished with sealing-wax or shellac varnish. 



It often is quite impossible to predicate beforehand what preserva- 

 tive medium will answer best for a particular kind of preparation..; 

 and it is consequently desirable, where there is no lack of material, 

 to mount similar objects in two or three different ways, marking on 

 each slide the method employed, and comparing the specimens from 

 time to time, so as to judge the condition of each. 



Importance of Cleanliness. The success of the result of any of 

 the foregoing operations is greatly detracted from if, in consequence 

 of the adhesion of foreign substances to the glasses whereon the 



