198 ON THE ECONOMICAL USES OF FISHES. 



From the livers of several kinds of dog-fish of the 

 genus Spinax^ a good oil is extracted, although this 

 is not done on the large scale, and in some parts of 

 the country, as the Hebrides and Orkney islands, 

 the fish themselves are eaten when nothing better is 

 in the way. The larger species of shark, which are 

 occasionally taken on our coast, are generally valu- 

 able captures, from the quantity of oil procured from 

 the liver by boiling, and in this way, from a basking 

 shark, twenty-six feet in length, mentioned by Pen - 

 nant as having occurred off Anglesey, 156 gallons of 

 oil were obtained. This leads us to mention various 

 species of ray, better known in this country by the 

 names of skate, thornback, &c., the large wings or 

 fins of which are much esteemed. 



We had occasion to mention, about the beginning 

 of this chapter, that the scales of several species are 

 used in the manufacture of artificial pearls, and for 

 this purpose, in Britain at least, the white-bait, for- 

 merly mentioned, and the bleak, Cyprinus alhurnus, 

 are best adapted. Properly speaking, it is not the 

 scales of these fish, but the silvery pigment which 

 gives them their lustre, that is used in this manu- 

 facture, which, however, is by no means carried to 

 the same extent now that it was a few years ago^ 

 when, as Dr. Lister states, a manufacturer in Paris 

 used, in a single winter, thirty hampers of hleak. 

 The mode of procedure is as follows : The scales are 

 well washed, and then allowed to soak in water, 

 when, after a time, the colouring matter is found at 

 the bottom of the vessel. This pigment is then dis- 



