100 PREPARATION AND MOUNTING 



Africa and America. They are usually mounted in balsam, 

 but are equally beautiful mounted dry, and used with the 

 lieberkuhn. They require as much care in cleaning as the 

 Diatomacese, but the process is a different one. Sometimes 

 this is effected by simply washing until they are freed from 

 all extraneous matter ; but this is seldom as effectual as it 

 should be. In the Microscopic Journal Mr. Furlong gives 

 the following method of treatment as the best he knows : 



Procure 



A large glass vessel with 3 or 4 quarts of water. 

 New tin saucepan holding 1 pint. 

 2 thin precipitating glasses holding 10 oz. each. 

 Take 3 oz. of dry Barbadoes earth (lumps are best), and 

 break into rather small fragments. Put 3 or 4 oz. of com- 

 mon washing soda into the tin and half fill it with water. 

 Boil strongly, and having thrown in the earth, boil it for 

 half an hour. Pour nine-tenths of this into the large glass 

 vessel, and gently crush the remaining lumps with a soft 

 bristle brush. Add soda and water as before, and boil again ; 

 then pour off the liquid into the large vessel, and repeat 

 until nothing of value remains. Stir the large vessel with 

 an ivory spatula, let it stand for three minutes, and pour 

 gently off nine-tenths of the contents, when the shells will be 

 left, partially freed only, like sand. 



2ND PROCESS. Put common washing soda and water into 

 the tin as before, and having placed the shells therein, boil 

 for an hour. Transfer to the large vessel as before, and 

 after allowing it to stand for one minute, pour off. Each 

 washing brings off a kind of " flock," which seems to be 

 skins. 



3RD PROCESS. Put the shells in a precipitating glass and 

 drain off the water until not more than ^ oz. remains. Add 

 half a teaspoonful of bicarbonate of soda, dissolve, and then 

 pour in gently 1 oz. of strong sulphuric acid. This liberates 

 the "flock," &c., and leaves the shells beautifully trans- 

 parent. Wash well now with water to get rid of all salts 

 and other soluble matter. 



