BISTRE. A brown pigment, consisting of the finest part of wood-soot, pul verized, and passed through a fine sieve, then mixed with a little gum-water, made into cakes, and baked. It is a fine transparent colour, and has much the same effect in water-painting, where alone it is used, as brown pink in oil. The best is prepared from dry beech wood, by grinding it with water into a smooth paste, then diluting it with more water. After the grosser liquor has subsided, the liquor is poured off; and left to settle for a few days; the fine matter that remains is the bistre.
BIT. The iron which is put into a horse's mouth, and to which the bridle is attached. There are various descriptions of bits, but they may all be ranged under two heads, the snaffle and the curb ; in the snaffle, the bit is formed slightly curved, and frequently jointed in the middle, and the bridle, or rein, is attached to rings in the extremities of the bit. Curb bits are generally formed with a small semicircular bend in the centre of the mouth-piece, and with arms or cheek-pieces formed at the ends of the mouth-piece. To the upper part of the cheek-pieces is hooked a chain passing under the lower jaw of the bone, and to the lower end of the cheek-pieces is attached the rein, by pulling which, the upper ends of the cheek-piece are thrown forward, and the curb chain pressed forcibly against the lowerjaw. Curb bits are very powerful in checking a horse, from the leverage afforded by the cheek-piece, but they tend greatly to injure the mouth, and cause much uneasiness to the animal. Mr. George Di glee, of Westminster, took out a patent, some years back, which, for ordinary riding or driving, is attended with no more injury or irritation to the horse's mouth than the ordinary snaffle, but which, when occasion requires, instantly acts as a very powerful curb. This effect is obtained by means of a sliding piece, with a ring attached to each cheek of the bit, to which ring the rein or bridle is connected in the usual way; and when it is found necessary to exert a considerable force in curbing the horse, the pulling of the rein will draw the slider towards the bottom of the cheek, thus lengthening the lever so consider ably that the horse is arrested by an irresistible power. The annexed, Fig. 1,
represents a side view of the improved bit, applied to a horse's head, and in the ordinary position, when riding or driving; the dotted lines show the position of the parts when the rein is pulled with considerable force. Fig. 2 gives a front view of the improved oit. a is the riding or driving rein attached to the ring b, which instead of being fixed to some particular part of the bit, as in the ordinary bit, is attached to a sliding piece c. A convoluted spring d acts upon this sliding piece, and keeps it and the ring b up to that part of the cheek which is near the mouth-piece, Fig. 2, where the leverage being small, the riding or driving rein will act in the ordinary manner; but when it becomes necessary to exert an extraordinary power upon the horse's mouth, the rein a is forcibly pulled back, by which the cheek of the bit is moved out of its per pendicular position, and the sliding piece e, with the ring, slides downwards towards the lower part of the cheek, as shewn by the dotted lines. To prevent the ring and slider from being drawn too low, a stop is placed on the bit at e for a riding bit, but for a driving bit, the bar at the bottom of the bit, as seen at f, answers the purpose. When the tension of the rein is relaxed, the elastic force of the spring draws up the sliding piece c, with the ring b, and the rein a, to its ordinary place, as represented in Fig 1. The cases i i, which contain the springs, are made to slide up and down in grooves, formed on opposite sides of the cheeks, for the convenience of oiling, exchanging, cleaning, or repairing the springs