I feel some compunction in obliterating what to my fellow-travellers are absurd prejudices; to me they are valuable records, like the disregarded fragments of some antediluvian creature, by which at the opposite sides of the globe the parts of a common stratum may be identified. This same prejudice guarded against Phœnician and Carthaginian the mineral wealth of Mauritania, while they were ravaging that of Spain. In the settlement of Mauritania made by Augustus, which was followed by four centuries of repose and prosperity, no traces of its mineral wealth appear, whilst the Roman world was supplied periodically with wheat from its fields. An ancient law forbade the working of gold and silver mines within the confines of Italy. There was reason in this. The facilities we have devised for centrating wealth have rendered of easy accomplishment things which men, had they been wise, would have surrounded with every obstruction. Until the funding system commenced, wars of aggression could be carried on only by a government which possessed a store of gold.[299] It was not, therefore, merely the depopulation of a district which was associated with the working of mines, but the loss of liberty; for the conqueror abroad became inevitably the tyrant at home. For the purposes of commerce Africa required no gold. Throughout that region there is to be found a process for adjusting exchange, at once the most simple and the most perfect; such as the plainest man would have first hit upon, such as the profoundest mathematician would have at last devised. It is a “standard of value.” I mean not that perversion to which we give the name, but an ideal standard in which all objects are alike rated, be they money, be they merchandise. In my anxiety to entertain my geological companions, I was nearly involving the community in war. I had given directions for sheep to be bought for the party for supper. They came to me presently to say that the sheep were ready, but that the people would take no money. I then sent a Jew servant of Mr. Seraya, to one of the other douars to buy them. Soon after there was a great commotion. Seeing him return with the sheep, and suspecting the intention, several of our tribe had run for their muskets, and sallied forth to drive the other people back who presumed to sell food to their guests.