266 The Commercial Products of the Sea. 



The perfectly white solution of the scales of the bleak 

 {Leuciscus alburnus), a fish indigenous to the rivers of France, 

 is now used largely for the manufacture of artificial pearls. 

 The solution or guanine is a mucus which lubricates the 

 scales of the fish. It coagulates by heat to a thick, white 

 deposit, and is obtained by carefully scraping the fish over 

 a shallow tub containing fresh water. Care is taken not to 

 scale the black or dorsal part, as these scales are yellow, 

 while the white scales only possess value. The material is 

 received on a horsehair sieve. The first water, mixed with 

 a little blood, is thrown away. The scales are then washed 

 and pressed, when the mucus or essence {guanine) sinks to 

 the bottom of the tub and appears as a very brilliant blue- 

 white oily mass. It takes 40,000 fish to furnish two pounds 

 of the material. The fishermen seal it in tin boxes with 

 ammonia, and in this condition send it to Paris. If a drop 

 of the essence be taken up by a straw and let fall upon 

 water, it floats, giving forth the most brilliant colours. Glass 

 bulbs, in the shape of pearls, lined with this substance, 

 imitate the real gems with remarkable closeness. 



