Gudgeons are found to thrive well in ponds, if these be fed by brooks running through them. Under favourable circumstances they have sometimes attained an unusually large size. They feed on aquatic plants, worms, water-insects, and the spawn of fish.
249. _The BLEAK_ (Cyprinus alburnus) _is a small fish of the carp tribe, with somewhat pointed muzzle, and no beards; and the scales thin, shining and slightly attached._
_It seldom exceeds the length of five or six inches._
_These fish inhabit fresh-water rivers, in nearly all the temperate parts of Europe, and are extremely common in many if those of our own country._
There is, in Paris, a great consumption of bleaks on account of their _scales_, which are used in the manufacture of _artificial pearls_. The scales are scraped off into clear water, and beaten to an extremely fine pulp. After this the water is several times changed until they are entirely free from colour. The silvery matter that is left precipitates to the bottom; and the water is carefully poured off from it, by inclining the vessel. This substance, mixed with a little size, is introduced, in small quantity, into thin glass bubbles, by a slender pipe, and moved about until their whole interior surface is covered. The remaining part of the bubble is then generally filled with wax. The inventor of this art was a Frenchman of the name of Jannin, a bead merchant in Paris.
In some countries bleaks are pickled in the manner of anchovies. When of large size they are well flavoured, but they are too bony to be in much request as food, even by the poor. They are considered in greatest perfection in the autumn.
250. _The COMMON STURGEON_ (Acipenser sturio, Fig. 71), _is a large kind of sea-fish with five rows of bony tubercles along the body; the mouth beneath the head, and four fleshy beards betwixt the mouth and the extremity of the muzzle._
_This fish sometimes growes to the length of sixteen feet and upwards._
_It inhabits the European and American seas, and annually ascends the rivers in the early part of the year._
It is to this and to a still larger species of sturgeon called the BELUGA (_Acipenser huso_), which is found in the river Wolga, that we are indebted for much of the well-known substance called _isinglass_. The mode of making isinglass was long kept a secret by the Russians, and has only of late years been made public. This article consists of certain membranous parts of fishes deprived of their viscous quality and properly dried. The sounds, or air bladders, are those of which it is chiefly made. They are taken out, while sweet and fresh, slit open, washed from their slime, divested of a very thin membrane which envelopes them, and then left to stiffen in the air. After this they are formed into rolls, each about the thickness of the finger, and put into the shape in which we see them, by small wooden pegs, and left to dry. The kind called _cake isinglass_ is formed of bits and fragments put into a flat metal pan with very little water, heated just enough to make the parts adhere, and subsequently dried in the air.