For the Scientific American. The trade in human hair has become quite important during these latter years, especially since it has been considered fashionable to replace by false hair, the deficiencies, real or supposed, of nature in this respect. The origin of wigs is lost in antiquity; their use was abandoned during the middle ages, and was not renewed until the return of Saint Louis from the crusades, when he unfortunately became bald and was ordered by his physicians to keep his head constantly covered. Queen Blanche, his kind-hearted wife, inferring from this that it was hair that had kept her husband's head warm, obtained from all the surrounding courtiers a lock of their capillary appendages which she forthwith attached to the king's cap. Ever since, Saint Louis has had the honor of being considered the patron saint of hair-dressers and wig-makers. After this period wigs are not mentioned in history until the reign of King Louis XIV, who, in order to hide the unequal hight of his two shoulders, wore a long wig which covered this defect. No man of quality in France was allowed to wear his own hair, and Binette, the king's wig-maker, became quite a celebrated personage who sold some specimens of his handicraft as high as one thousand dollars. In 1674 the wig-makers as a body were duly incorporated, the members being allowed to carry side weapons, and they held the exclusive monopoly of the trade in human hair, which they retained until the revolutionary period which swept all chartered privileges from the soil of France. Notwithstanding many eminent professors of hygiene give reasons why the wearing of false hair is not healthy, and although it is also a well-known fact that a portion of it has been cut from the bodies of the dead, still the habit of wearing other people's hair has never been discontinued since the time of Louis XIV. Hair, to be really first quality, should be taken from the heads of the living, who have had much exposure to the air and who have never employed curling irons. The hair taken from the dead i3 mostly used in the preparation of watch chains, bracelets, and similar articles. France monopolizes the largest share of the trade in human hair. Paris, Marseilles, Lyons, Caen, Guibray, and Beaucaire, are the cities which do the largest part of this trade, the last three holding annual fairs for this specialty. In Paris alone there are some thirty or forty dealers in hair, j each of whom employs three or four regular cutters. These in their turn have several agents or decoys who visit the country, penetrating every village and hamlet through the land, where they try to induce the poor simple country girls to part with their hair for some trifling articles of barter, such as gaudy muslin handkerchiefs or false j ewelry. Some years back one firm in Paris traded in this way during one season nearly one hundred thousand dollars of merchandise; but the present merchants are compelled to pay in money instead of gewgaws. The peasants having learned the value of their hair,refuse to be swindled. The exports of human hair, from France to the United States jeeently increased so rapidly that the supply proved inadequate to meet the requirements and the price was doubled. Germany, Belgium, Poland, and Eussia, have since joined to furnish us with our supplies. Another reason for the high price paid for hair is the well-ascertained fact, that,as education spreads in France, the country girls refuse to sell their hair; one of the principal motives for which is, that many of the young Frenchmen who have been drafted into the imperial army, on their liberation from service and return home, are averse to marrying the short-cropped and disfigured sweethearts they find on their return from the garrison towns, where the ladies all wear long hair, waterfalls, or chignons. Some years tack the hair-cutting agents managed to obtain a full supply from Normandy and Brittany alone; but they have now to travel over the whole of France, Italy, and Sicily. The total annual crop of the globe is at present about one million of pounds. The northern hair is fine and soft; the southern is best fitted for curling. Two clippings are made annually, one in the spring of the year the other in autumn, the latter being considered of inferior quality. The collected hair is tied into separate coils and thrown loosely into sacks, which are forwarded to the merchants who must purchase or refuse the whole lot, as they are no! allowed the privilege of assorting. As the hair from different portions of the same head varies in length and qualify, it has to be picked and sorted by being put through six or seven successive operations, the first of which is to clear it of nits, or the adherent eggs of lice, which are abundant in the hair of the women of Italy and Brittany. Hair destined for curling or for ringlets is rolled on email wooden rollers about four inches long, covered with paper, tightly bound, boiled, and, lastly, dried in an oven at a moderate heat. The cost of hair nearly quadruples from the time it is cut until it gets into the hands of the retailer. He in his turns attaches a quite arbitrary higher price to the same, in accordance with the presumed fortune of his customers, or the difficulty he is supposed to have experienced in finding a particular tint sui i ed to some special taste, or to the complexion of countenance. His price may vary, for a head of hair, from two dollars to three hundred times that amount. The art of dyeing the hair has reached such perfection in our day, that, excepting very fiery red, fair blondes, and silvery white, which are difficult to imitate, all colors sell for identical prices. Theatrical wigs having to be seen at a distance, are cheap, with the occasional exception of the private property of some particular star actor. It is nearly useless to add that the cast-offcoils, knots, chignons, fronts, curls, and wigs are collected, cleaned, carded, and serve over and over again, spread over paddings of horse hair, or some other material, to adorn the heads of our fashionable belles. Corn Starcli—-How it is Manufactured. Methods for the preparation of this popular article of food vary somewhat with manufacturers, but the following method, patented 1854, by Mr. Polsen of Paisley, Scotland, is perhaps as good as any. By this method the grain is first steeped either in alkaline water, or in water only, Until the grain is thoroughly soaked. It is then reduced to pulp by the use of rollers, or other suitable machinery. It is next passed over a sieve through which the finer portions are forced by revolving brushes while the coarser parts remaining are returned to be reground. The husk or bran is thus separated, and may be used as food for cattle. A stream of water runs constantly down upon the sieve and carries the portion passing through, over an inclined plane or " run." The plane is divided into sections by wooden cleats which are laid across it. These cleats or dams intercept the starch which settles to the bottom, from whfth it is removed at proper intervals?. The greater part of the glutinous and fibrous portions are carried along by the current, and are thus separated from the starch. The starch can be still further purified from the glutinous and fibrous matters by treating it with an alkaline solution which dissolves the gluten, running it through finer sieves, and rewashing it on the inclined plane. Fictitious Gems.—A recent English work on diamonds says that but a small portion ef the gems sold and worn is genuine. The diamond mines o f Golconda have given out, and those of India are rapidly failing. Thus the scarcity of real gems has been met by the ingenuity of counterfeiters. As for these patent imitators, these indefatigable fabricators of gems, it is scarcely probable that the curious branch of industry will ever be relinquished; at least, it is certain that while poor humanity retains its present tendency to strive for that which is beyond its reach, and accept the shadow for the substance, paste diamonds, enameled porcelain opals, and pearls of fish scales will be marketable artieles in the civilized world, as well as among the dusky tribes upon the coral strands of Africa.