from the simple tool or implement, such as the club or knife, which enables man to strike or cut more effectively than with hands or teeth, to the machine which, when supplied with force, only needs to be set and directed by man to do his work. Man often himself provides the power which the machine distributes more conveniently, as when the potter turns the wheel with his own foot, using his hands to mould the whirling clay. The highest class of machines are those which are driven by the stored-up forces of nature, like the saw-mill where the running stream does the hard labour, and the sawyer has only to provide the timber and direct the cutting.

As to how simple mechanical powers were first learnt, it is of no use to guess in what rude and early age men found that stones or blocks too weighty to lift by hand could be prized up and moved along with a stout stick, or rolled on two or three round poles, or got up a long gentle slope more easily than up a short steep rise. Thus such discoveries as those of the lever, roller, and inclined plane, are quite out of historical reach. The ancient Egyptians used wedges to split off their huge blocks of stone, and ore wonders that, knowing the pulley as they did, it never appears in the rigging of their ships (see Fig. 71). A draw-well with a pulley is to be seen in the Assyrian sculptures, where also a huge winged bull is being heaved along with levers, and dragged on a sledge with rollers laid underneath.

The wheel-carriage, which is among the most important machines ever contrived by man, must have been invented in ages before history. To see what constructive skill the leading nations had already attained to in times we reckon as of high antiquity, it is worth while to examine closely the Egyptian war-chariots, with their neatly-fitted and firmlytired spoke-wheels turning on their axles secured by linch

pins, while the body, pole, and double harness show equal technical skill. In looking for some hint as to how wheel. carriages came to be invented, it is of little use to judge from such high skilled work as was turned out by these Egyptian chariot builders, or by the Roman carpentarii or carriage-builders from whom our carpenters inherit their name. But as often happens, rude contrivances may be found which look as though they belonged to the early stages of the invention. The plaustrum or farm-cart of the ancient world in its rudest form had for wheels two

FIG. 61.-Ancient bullock-waggon, from the Antonine Column.

solid wooden drums near a foot thick, and made from a tree-trunk cut across, which drums or wheels did not turn on the axle but were fixed to it; the axle was kept in place by wooden stops, or passed through rings at the bottom of the cart, and went round together with its pair of wheels, as children's toy carts are made. It is curious to notice how, under changed conditions, the builders of railwaycarriages have returned to this early construction. In the ancient cart, Fig. 61, the squared end of the axle shows that it must turn with the wheels. In such countries as

Portugal the old classic bullock-cart on this principle is still to be seen, and it has been reasonably guessed that such carts tell the story how wheel-carriages came to be invented. Rollers were early used, on which a block of stone or other heavy weight was trundled. Suppose such a roller made of a smoothed tree-trunk to be improved by cutting the middle part smaller, so that it became an axle and pair of broad wheels in one piece, then by making this axle work underneath the rudest framework, the simplest imaginable wheelcarriage is made. If the first notion of a cart were thus suggested, the wheels might afterwards be made separately and pinned on to the square axle, and provided with tires. Then, for light wheels and smooth ground, the wheels would at last be made to turn on fixed axles. This is only conjecture, but at any rate it puts clearly before our minds what the nature of a carriage is.

The rudest tribes

Another ancient machine is the mill. of savages had a simple and effective means ready to hand for powdering charcoal and ochre to paint themselves with, or for the more useful work of bruising wild seeds gathered for food. The whole apparatus consists of a roundish stone held in the hand, and a larger hollowed stone for a bed. It is curious to notice how closely our pestle and mortar still keeps to this primitive type. Now any one using the pestle and mortar may notice that it works in two ways, the stuff being either pounded by striking, or ground by rubbing against the side of the mortar. When people took to agriculture, and grain became a chief part of their food, and mealing it the women's heavy work, forms of mealingstones came into use suited not for pounding but for grinding only, and doing this more perfectly. An example may be seen in Fig. 62, a rude ancient corn-crusher dug up in Anglesey, the stone muller or roller having its sides hollowed

for the hands of the grinder, who worked it back and forward on the bed-stone. The perfection of such a corncrusher may be seen in the "metate" with its neatly shaped bed and rolling-pin of lava, with which the Mexican women crush the maize for their corn-cakes or tortillas. But it is by one stone revolving upon the other that grain is best ground, and here we have the principle of the mill. The quern or hand-mill of the ancient world in its simple form consisted of two circular flat mill stones, the upper being turned by a handle, while the grain was poured in through the hole in the centre, and came out as meal all round the edge. This early hand-mill has lasted on into the modern

FIG. 62.-Corn-crusher, Anglesey (after W. O. Stanley.

world, and Fig. 63 shows "two women grinding at the mill," as they might be seen in the Hebrides in the last century; the long stick, which hangs from a branch above, has its end in a hole in the upper stone, and a cloth is spread on the ground to catch the meal. The quern is still used in north Scotland and the islands. If the reader will notice the construction of a modern flour-mill, it will be seen that the neatly faced and grooved millstones are now of great weight, and the upper one balanced on the pivot which gives it rapid rotation from below by means of water or steam-power, but notwithstanding these mechanical improvements, the essential principle of the primitive hand-mill is still there.

Another group of revolving tools and machines begins with the drill. The simplest mode of twirling the boringstick between the hands is to be seen in fire-making (Fig. 72). In this clumsy way rude tribes know how to bore holes through hard stone by patiently twirling a reed or stick with sharp sand and water. This primitive tool was improved both for making fire and boring holes, by winding

FIG. 63.-Hebrides women grinding with the quern or hand-mill (after Pennant).

round the stick a thong or cord, which by being pulled backward and forward worked the drill, as the ancient shipwrights boring their timbers are described in the Odyssey (ix. 384). The ingenious plan of using a bow with its string to drive the drill, so that one man can manage it, was already known in the old Egyptian workshops, but the still more perfect Archimedean drill is modern. The turning-lathe