If, in the middle ages, aristocracy was founded upon land, society derived a great advantage from the circumstance; for territorial property, which does not change, which is always the same, preserves the institutions and manners of a people better than industrial property, which most frequently belongs no more to one country than another, and which, on that account, bears within itself the germs of corruption. If it was for this reason that formerly nobility was degraded by giving itself up to the speculations of commerce and industry, it must be agreed that the usage thus established, had at least a respectable aim, and arose from a salutary principle.[99] Territorial property had then such an influence over the social state, that it is quite enough to be acquainted with the changes it experienced, to judge of the changes to which society was subjected. “As soon as the state of the property of a certain period is discovered,” says Robertson, “we may determine with precision what was at the same time the degree of power then enjoyed by the king or the nobility.” During the crusades, ecclesiastical and civil laws permitted nobles to alienate their domains. A great number of them availed themselves of this fatal privilege, and did not hesitate to sell their lands; which displaced property, and consequently power. The nobility thus lost its power, and the crown gained that which the aristocracy lost. The crusades, however, were not unproductive of good fruit for the nobility; gentlemen acquired principalities in the East; most of the cities of Greece and Syria became so many lordships, which recognised as masters counts and barons enrolled under the banners of the holy wars; some, still more fortunate, ascended the throne of David, or that of Constantine, and took place among the greatest monarchs of Christendom. The military orders likewise presented the nobility with amends for the losses they experienced in ruinous wars. These orders had immense possessions in both the West and the East; they were for the European nobility, an asylum in peace, and a school of heroism in war. It was at this period that the use of surnames was introduced, and coats of arms were assumed. Every gentleman added to his own name the name of his estate, or the title of the lordship he possessed; he placed in his coat of arms a sign which distinguished his family and marked his nobility; genealogy became a science, and consecrated, by its researches, the illustration of races. Whatever value may be now-a-days attached to this science, it must be admitted that it often threw a great light upon the history of illustrious families, and sometimes upon the general history of a country to which these families belonged.