In the development of the life of a State, the distance in time between causes and their visible effects often makes the sequence obscure or sink from sight altogether. As in geology the century is useless as a unit to measure the periods with which that science deals, and as in astronomy the mile is useless as a standard for the interstellar spaces; so in history, in tracing the organic changes within the conscious life of a State, the lustrum, the dekaetis, or even the generation, would sometimes be a less misleading unit than the year. The England of Elizabeth drew the first outline of the Empire of the future; but five generations were to pass before the Britain of Chatham[7] could apply itself with a single-hearted resolution to fill that outline in, and yet three other generations before this people as a whole was to become completely conscious of its high destiny. Freedom of religion and constitutional liberty had to be placed beyond the peril of encroachment or overthrow, before the imperial enterprise could be unreservedly pursued; but the deferment of the task has nerved rather than weakened the energy of her resolve. Had England fallen in the Maryborough wars, she would have left a name hardly more memorable than that of Venice or Carthage, illustrious indeed, but without a claim to original or creative Imperialism. But if she were to perish now, it would be in the pursuance of a design which has no example in the recorded annals of man. Similarly in Rome, two centuries sever the Rome which rose from Cannae from the Rome which administered Egypt and Hispania. And in Islam four generations languish in misery before the true policy of the Abbassides displays itself, striking into the path which it never abandoned.