[Illustration: Fig. 124.--Primitive Corn-mill.] In the 'Voyage du Mississippi à l'Océan,' by M. Molhausen, we read:-- "The principal food of the Indians consisted of roasted cakes of maize and wheat, the grains of which had been pulverised _between two stones_."[21] In Livingstone's Expedition to the Zambesi (Central Africa), it is stated that "the corn-mills of the Mangajas, Makalolos, Landines and other tribes are composed of a block of granite or syenite, sometimes even of mica-schist, 15 to 18 inches square by 5 or 6 inches thick, and a piece of quartz, or some other rock of equal hardness about the size of a half-brick; one of the sides of this substitute for a millstone is convex, so as to fit into a hollow of a trough-like shape made in the large block, which remains motionless. When the woman wants to grind any corn, she kneels down, and, taking in both hands the convex stone, she rubs it up and down in the hollow of the lower stone with a motion similar to that of a baker pressing down his dough and rolling it in front of him. Whilst rubbing it to and fro, the housewife leans all her weight on the smaller stone, and every now and then places a little more corn in the trough. The latter is made sloping, so that the meal as soon as it is made falls down into a cloth fixed to catch it." [Illustration: Fig. 125.--The Art of Bread-making in the Stone Age.] Such, therefore, was the earliest corn-mill. We shall soon see it reappear in another form; two mill-stones placed one over the other, one being set in motion above the other by means of a wooden handle. This is the corn-mill of the bronze epoch. This type maintained its place down to historic times, as it constituted the earliest kind of mill employed by the Roman agriculturist. In order to represent the existence of agriculture during the polished-stone epoch, we have annexed a delineation of a woman grinding corn into meal in the primitive mill (fig. 125). In the same figure may be noticed the way of preparing the meal coming from the mill for making a rough kind of cake. The children are heating in the fire some flat circular stones. When these stones are sufficiently heated, they rapidly withdraw them from the fire, using for the purpose two damp sticks; they then place on the stones a little of the meal mixed with water. The heat of the stones sufficed to bake the meal and form a sort of cake or biscuit. We may here state, in order to show that we are not dealing with a mere hypothesis, that it is just in this way that, in the poor districts of Tuscany, the _polenta_ is prepared even in the present day. The dough made of chestnut-meal, moistened with water, is cooked between flat stones that are placed one over the other in small piles as portrayed in the annexed plate.