Herein lies the unity of subject of this book; not in its concern with a given class of experiences during a given period. Roughly speaking, in the two half-centuries preceding and succeeding the year 1600, the practice of the upper classes of sending sons abroad as part of their education became successively an experiment, a custom, and, finally, a system. By the middle of the seventeenth century this system had become a thoroughly set system, and the "Grand Tour" a topic for hack-writers. Of the latter, James Howell was the first. His "Instructions for Foreign Travel" (1642) may serve to date the beginning of "Grand Touring" in the modern sense of the phrase, while the publication of Andrew Boorde's "Introduction of Knowledge" a century earlier, does the same for this preceding period, that of the development of travel as a means of education. Delimiting the movement by means of English books suggests that it was a merely English movement, but it was in fact European, though true of the different countries in varying degrees. The increase of diplomatic journeys,[6], already mentioned, the core of this development and its chief instrument, was common to all divisions of Europe in proportion to the degree of the civilisation attained. In the Empire and Poland the custom grew up less suddenly; it had begun earlier. In Italy, it began later, since it was not till later that there was much for an Italian to learn that he could not learn better at home. Sir Henry Wotton[7] noted in 1603 that travelling was coming into fashion among the young nobles of Venice. In France, an early beginning was broken off by the civil wars, not to start afresh till Henry IV's sovereignty was established. As for Spaniards and Portuguese, they alone had dominions over-sea to attend to. In England, on the other hand, political reversals being at once frequent, thorough, and peaceable, migrations were very common and usually short. That touring would result from migration was certain, because it familiarised English people with the attractions and the affairs of the continent and with the uses of that familiarity, and established communications. Other special causes existed, too, truisms concerning which are so plentiful that there is no need to repeat them here.