When in a certain community one particular kind of commodity is of general use and generally available, this comes to form the unit in terms of which all values are expressed. The nature of this barter-unit will depend upon the nature of the climate and geographical position, and likewise upon the stage of culture to which the people have attained. In the hunting stage, all the property of each individual consists in his weapons and implements of war and the chase, and the skins of wild beasts which form his clothing, and sometimes the cover of his hut or wigwam. At a later stage, when he has succeeded in taming the ox, the sheep, or the goat, or the horse, he is the owner of property in domestic animals, whose flesh and milk sustain him and his family, and whose skins and wool provide his clothing. By this time too he has found out that it is better to make the captive whom he has taken in war into a hewer of wood and drawer of water than merely to obtain some transient pleasure from eating him after putting him to death by torture, or by wearing his skull or scalp as personal decorations. This is now the pastoral or nomad stage. Next comes the more settled form of life, when the cultivation of land and the production of the various kinds of cereals renders a permanent dwelling-place more or less necessary. Property now consists not merely in slaves and domestic animals, but likewise in houses of improved construction, and large stores of grain. Man now possesses certain of the metals, gold and copper being the first to be known. How does he appraise these metals when he exchanges them with his neighbour? We shall find that he estimates them in terms of cattle, and that he at first barters them all by measures based on the parts of the human body, a method which continues to be employed for copper and iron long after the art of weighing has been invented; next he estimates his gold by certain natural units of capacity such as a goosequill, and finally fixes the amount of gold which is equivalent to a cow, by setting it in a rude balance against a certain number of natural seeds of plants. Such is the process which history tells us has taken place in the temperate regions of Asia and Europe, Africa and America. Just as it is impossible to learn the history of the growth of the earth’s crust by confining our observations to one locality, and as the geologist only succeeds in gaining a true insight into the relations between the various strata by a study of the phenomena of many regions, so we shall only be able to comprehend properly the various stages in the growth of metallic currency and the origin of weight-standards by observing the facts revealed to us in various countries. Whilst in some places we shall meet with but one or two steps, in others we shall find traces of many, though often, broken strata. Like advance, however, seems impossible under the extremes of heat and cold. Hence in the latter