36 THE HISTORY OF MEDIEVAL EUROPE precisely because their procedure in any trade was largely by rule of thumb and represented a' separate discovery, hit upon perhaps by chance, instead of by a rational use of applied science. Many workmen mixed religious ritual or magical ceremony and incantations with their material ingredients and actual manual and mechanical operations without realizing that the article thus made was entirely the result of the latter factors and not at all of the former. If a doubt sometimes entered their minds, they probably thought it safer to continue making the thing in the way it had always been made. Some places were noted for the manufacture of some one article, as Athens had been for its vases before the time of the Empire, and as Gaul became for its woolens and linens during the Empire. In such cases these products would be exported to other localities. But since under the Empire workmen could move about without danger and go wherever there was a demand for their serv- ices, the general rule was that most of the articles used by the inhabitants of a town were made in that town. Historians disagree widely in their estimates of the popu- lation of the Empire — a matter difficult to determine. Rome was certainly a more populous city than to-day, as its vast extent and many ruinous quarters indicate, and there were at least half a dozen other cities each with a population of three hundred thousand or over. But of course lands like Gaul and Britain had a much smaller population than they support now, while Greece and Italy had become depopulated to a considerable extent by the time of the Empire. On the other hand, North Africa was more populous than it has been since. The East was undoubtedly the most thickly settled part of the Empire. In large cities like Rome and Carthage there were buildings many stories high, and the narrow streets were crowded by the passing throng. Leaving city for country, and commerce and industry Land for agriculture, we find the leading feature of system ^ e j anc ] S y S tem to be the large domain of the great landowner, cultivated by small tenants and by slaves.
