much in the same way as a land Frontier may be crossed by a railroad or pierced by a tunnel. The sea was such a link in the case of Greece and her city colonies, enabling her (no hostile power having command of the Mediterranean) to maintain connexion with her foreign colonies, in spite of the fissiparous influence of her physical configuration on the mainland. Similarly, the Mediterranean was a connecting link between Rome and her outlying possessions, just as it is at the present day between France and her North African colonies. Indeed the Mediterranean has never in civilised times been the southern Frontier of Europe; the latter has in reality been supplied by the Atlas Mountains and the great Desert of Sahara. The Persian Gulf is another illustration of a sea that has shown itself to be not a barrier but a link: the Arabs who were skilled and courageous mariners from early times (witness the story of Sinbad the Sailor) having occupied both shores with their settlements. The sea may also act as a vehicle of invasion. It brought the Jutes and Saxons, the Norsemen and Danes to England, just as it had brought the Romans before them.
Nevertheless, the opposite or separating quality of the sea is undoubtedly the more striking and familiar aspect. I have already alluded to its influence upon the relations of Great Britain and France, and of Great Britain and Ireland. Only when England ceased to be a Continental power did the national spirit blossom into any fullness. The project of a Channel Tunnel between the coast of England and France has twice perished because of the invincible and legitimate repugnance of the Englishman to sacrifice his maritime Frontier for no tangible return. It was because of the