change. The small balls of sewing cotton, so cheap and so beautifully wound, are formed by a machine on the same principle, and but a few steps more complicated. The common smoke-jack is an instrument in which the velocity communicated is too great for the purpose required, and it is transmitted through wheels which reduce it to a more moderate rate.

Extending the Time of Action in Forces.—The half-minute which we daily devote to the winding up of our watches is an exertion of labour almost insensible; yet, by the aid of a few wheels its effect is spread over the whole twenty-four hours. Another familiar illustration may be noticed in our domestic furniture: the common jack by which our meat is roasted, is a contrivance to enable the cook in a few minutes to exert a force which the machine retails out during the succeeding hour in turning the loaded spit.

Saving Time in natural Operations.—The process of tanning formerly occupied from six months to two years; this time being apparently required in order to allow the tanning matter to penetrate into the interior of a thick hide. The improved process consists in placing the hides with the solution of tan in close vessels, and then exhausting the air. The consequence of this is to withdraw any air which might be contained in the pores of the hides, and to employ the pressure of the atmosphere to aid capillary attraction in forcing the tan into the interior of the skins. The effect of the additional force thus brought into action can be equal only to one atmosphere, but a further improvement has been made: the vessel containing the hides is, after exhaustion, filled up with a solution of tan; a small additional quantity is then injected with a forcing-pump. By these means any degree of pressure may be given which the containing vessel is capable of supporting, and it has been found that, by employing such a method, the thickest hides may be tanned in six weeks or two months.

Printing from Wooden Blocks.—A block of box-wood is, in this instance, the substance out of which the pattern is formed: the design being sketched upon it, the workman cuts away with sharp tools every part except the lines to be represented in the impression. This is exactly the reverse of the process of engraving on copper, in which every line to be represented is cut away. The ink, instead of filling the cavities cut in the wood, is spread upon the surface which remains, and is thence transferred to the paper.

Making and Manufacturing.—There exists a considerable difference between the terms making and manufacturing. The former refers to the production of a small, the latter to that of a very large number of individuals; and the difference is well illustrated in the evidence given before the Committee of the House of Commons on the Export of Tools and Machinery. On that occasion Mr. Maudslay stated, that he had been applied to by the Navy Board to make iron tanks for ships, and that he was rather unwilling to do so, as he considered it to be out of his line of business; however, he undertook to make one as a trial. The holes for the rivets were punched by hand-punching with presses, and the 1,680 holes which each tank required cost seven shillings. The Navy Board who required a large number, proposed that he should supply forty tanks a week for many months. The magnitude of the order made it worth while to commence manufacturer, and to make tools for the express business. Mr. Maudslay therefore offered, if the Board would give him an order for two thousand tanks, to supply them at the rate of eighty per week. The order was given: he made the tools, by which the expense of punching the rivet-holes of each tank was reduced from seven shillings to ninepence; he supplied ninety-eight tanks a week for six months, and the price charged for each was reduced from seventeen pounds to fifteen.

Brass-plate Coal Merchants.—In the recent examination by the committee of the House of Commons into the state of the Coal Trade, it appears that five-sixths of the London public is supplied by a class of middle-men who are called in the trade "Brass-plate Coal Merchants:" these consist principally of merchants' clerks, gentlemen's servants, and others, who have no wharfs, but merely give their orders to some true coal-merchant, who sends in the coals from his wharf. The brass-plate coal merchant, of course, receives a commission for his agency, which is just so much loss to the consumer.

Raw Materials.—Gold-leaf consists of a portion of the metal beaten out to so great a degree of thinness, as to allow a greenish-blue light to be transmitted through its pores. About 400 square inches of this are sold, in the form of a small book, containing twenty-five leaves of gold for 1s. 6d. In this case, the raw material, or gold, is worth rather less than two-thirds of the manufactured article. In the case of silver leaf, the labour considerably exceeds the value of the material. A book of fifty leaves, covering above 1,000 square inches is sold for 1s. 3d.

The quantity of labour applied to Venetian gold chains is very great, but incomparably less than that which is applied to some of the manufactures of iron. In the case of the smallest Venetian chain the value of the labour is not above thirty times that of the gold. The pendulum spring of a watch, which governs the vibrations of the balance, costs at the retail price twopence, and weighs fifteen one-hundredths of a grain, whilst the retail price of a pound of the best iron, the raw material out of which fifty thousand such springs are made, is exactly the sum of twopence.

In France bar-iron, made as it usually is with charcoal, costs three times the price of the cast-iron out of which it is made; whilst in England, where it is usually made with coke, the cost is only twice the price of cast-iron.

THE NATURALIST.

THE NINE-BANDED ARMADILLO.

THE NINE-BANDED ARMADILLO.

Armadillos are almost exclusively natives of South America, principally of the province of Paraguay. Some inhabit the forests; others are found in the open country. There are several species, all of which are invested with a coat of mail, or a kind of plate armour resembling the covering of the pangolin, or scaly ant-eater, and the shell of the tortoise. This crust or shell covers the upper parts of the animal, and consists of four or five different parts or divisions. The head may be said to have a helmet, and the shoulders a buckler, composed of several transverse series of plates. Transverse bands, varying in the different species from three to twelve, which are movable, cover the body; the crupper has its buckler similar to that on the shoulders, and the tail is protected by numerous rings. The hairs of the body are few, springing from between the plates; the under parts, which are without armour, have rather more hairs. In a living state, the whole armour is capable of yielding considerably to the motions of the body; the pieces or plates being connected by a membrane, like the joints in a tail of a lobster. The under parts present a light grainy skin. The legs are thick and strong, but only long enough to raise the body from the ground; the nails are very powerful, and calculated for digging; and, according to Buffon, the mole is not more expert in burrowing the earth.

Some of the species have nocturnal habits and are very timid, flying to their burrows the moment they hear a noise. Other species quit their retreat equally by day and night, and these are said not to be so rapid in their motions as the others. All the species walk quickly, but they can neither leap, run, nor climb; so that, when