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.
ORDER VI.—CHONDROPTERIGIOUS FISH.
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.
Although by far the greatest quantity of isinglass is obtained from the beluga, as being the largest and most abundant fish in the rivers of Muscovy, yet it has been ascertained that this substance may be made from the air-bladders of every species of fresh water fish. The principal consumption of isinglass is by brewers and others, for the fining of fermented liquors: this it appears to do merely by the mechanical effect of its organization, which forms a kind of strainer, or fine net-work, and carries the gross impurities before it, as it subsides. It is sometimes employed in medicine; and also in cookery, for making jellies, and other purposes.
Caviar is a kind of food made generally from the roes of the sturgeon. For this purpose they are washed, when fresh, by rubbing them, with the hands, in a sieve, to free them from the fibres by which the several eggs are connected together. They are then washed in white wine or vinegar, and spread out to dry. After some further processes, they are either formed into cakes, each about an inch in thickness and three or four inches in diameter, or they are packed in small kegs for use.
The flesh of the sturgeon is firm, white, and of excellent flavour; and, by some persons, has been compared to veal. It is considered best when roasted; though it is commonly sold in a pickled state, and, in this state, is chiefly imported from the rivers of the Baltic and North America. All sturgeons that are caught near London are taken to the Lord Mayor, and are by him presented to the King. In Italy the back bones of these fish are cut into pieces, salted and smoked for food. The Russians frequently convert the skins of sturgeons into a kind of leather, which they use for the covering of carriages.