CAR trated by the necessary Cut?, we shall communicate under the re- spective heads of Locking-pole, and Wheel-drag. In London and Westminster, carts are not permitted to carry more than twelve sacks of meal, 750 bricks, one chaldron of coals, &x. on pain of forfeiting one of the horses (stat. 6 Geo. I. c. 6). — By the laws of the city, carmen are forbidden to ride either on their carts or horses : they are to lead ©r drive them on foot through the streets, under the penalty of 10s. (stat. 1 Geo. I. c. 57). By 38 Geo. III. c. CJ3, there is a duty of ll. 4s. a year to be paid on all carts or carriages with less than four wheels, to be drawn by one horse, without any other than a tilted covering, and without any lining, springs, or ornament what- ever, except a paint of a dark colour, with the words, " a taxed cart," and also the owner's name, written upon it ; and the price of such cart shall not exceed 12l. Rolling-carts are very useful machines for carrying manure on low-lands during wet seasons. Ac- cording to an account given by Mr. Richard Mottle; and in- serted in the 14th volume of -the '* Transactions of the Society for the Encouragement of the Arts, Sac." such a cart consists of three circular pieces of strong elm, two feet in diameter, and each eighteen inches long, through which a strong iron axis is passed, so as to protrude a few inches on each end beyond the rollers ; after all, al- lowing an inch between each piece, for the convenience of turning round. On the projecting part of the axis, a fixed frame is placed, for supporting the body of the cart which, according to the nature of C A S' [445 the soil, maybe loaded to any de- gree, and employed simply as a roller, or for carrying manure, &c. on land where, common wheels cannot be admitted. By means of these rolling carts, the surface of the land is to be fre- quently compressed, in order to consolidate the soil more perfectly, so that the earthy particles may embrace the roots of the grasses, and retain their proper moisture ; on which the luxuriancy of such soils in a great measure depends. CARTILAGE, is a smooth, elastic, and insensible animal sub- stance, somewhat approaching to the nature of b< >n Cartilages have a natural elasti- citv, the power of which is so great that, on being forced out of their situation, they spontaneously re- turn to it, as soon as that force is removed. They are principally situated in those parts of the hu- man body, which require a slight and eas) motion, as in the ears, nose, &c. Their elasticity Supplies the place of antagonist muscles, or such as are by Nature designed to counteract each other. Cartilages also invest all the ends of those bones, that are conjoined for per- forming motion"; because, as they are both smoother and softer than bones, which are insensible, rhe attrition occasioned by the motion of the joints is thus more effectu- ally guarded against. — See likewise Charcoal. CASE-HARDENING of Iron, is a superficial conversion of that metal into steel, by a cementation of it with vegetable or animal coals. This operation is usually perform- ed on small pieces of iron, worked, intotoois and instruments, by put- ting them together with the ce- ment, into an iron box, which is closely
