To the Irish the important thing therefore was that the way of the sea was still open. Traders from Gaul sailed along the western coast, and up the Shannon to Roscommon and Loch Cé, and on the eastern side their ships passed by the Irish Sea to what is now Down and Antrim, to Iona, and Cantyre. They still as of old carried the wine of Provence in great wooden tuns, in one of which three men could stand upright; there still came men speaking Greek, and scholars of the east, and artists of Gaul. At this time indeed the Irish were no recluse people, living in a backwater or severed from the great world. An Old Irish poem tells of the traditions of Leinster under its ancient kings—“The sweet strain heard there at every hour; its wine-barque upon the purple flood; its shower of silver of great splendour; its torques of gold from the lands of the Gaul.” The metropolis of Columcille’s church organization at Iona, the established centre of Irish learning at Bangor in Down, both alike lay in the track of the sailing ships, and in frequent communication with Europe. News of the destruction by earthquake of Citta Nuova in Istria was brought to Columcille that same year by Gaulish mariners. Columbanus and his companions could take ship from Bangor to Nantes on their mission to Europe (589). Northwards Irishmen sailed to the Hebrides, the Orkneys, the Shetlands. They seem to have traded and married with Scandinavians a century before the invasion of Ireland by the Wikings. Moreover Irishmen had travelled as far as Iceland in 795, where Nadoddr the Norseman heard of them some sixty years later.

Thus the old civilization, rudely interrupted elsewhere, was carried on unbroken in Ireland. Now was the time (500-1000) when the island began to give back to Europe the treasures of learning which she had stored up in the time of the Roman Empire, and had kept safely through the barbarian wars. Missionaries and scholars from Iona and Ireland carried letters and Christian teaching to every part of England, while ship-loads of Englishmen went to Ireland for instruction. Other Irishmen sailed to Brittany, and journeyed east over northern France beyond the Rhine. A greater number travelled by Nantes, Angers, Tours, past the monastery of Columbanus at Lisieux, and thence over middle Europe, or by St. Gall southward through Italy as far as Tarentum, and to the Holy Land. Occasionally pilgrims and missionaries took the road to Europe through Britain, when with the settlement of the English kingdoms and the coming of Augustine (597) a new intercourse had opened between the English and the continental peoples. That is, some few travellers went this way, but merchants still kept to the old sea route, and the greater number of Irish pilgrims and scholars. It was by that way, for example, according to the old story by a monk of St. Gall, that two Scots from Ireland sailed to Gaul in the early days of Charles the Great, and in the market-place, where the merchants trafficked with the crowds, raised their cry of an Irish trade:—“If anyone is desirous of wisdom, let him come to us and receive it, for we have it to sell.” At last they were brought to Charles himself, who asked what payment they would need; nothing more, they answered, than convenient situations, ingenious minds, and as living in a foreign country to be supplied with food and raiment; and the king formed a school for one of them in France, and set the other at the head of the great school at Pavia. Irish monasteries, one after another in rapid order, rose along the main highways of travel, among the ruined heaps of Roman towns where wild beasts alone found shelter, in forest and desert and mountain. Every school had Irish teachers and Irish manuscripts, relics of which still remain in continental libraries. Ireland became the source of culture to all Germanic nations: indeed wherever in the seventh and following centuries education or knowledge is found it may be traced directly or indirectly to Irish influence. It has been justly said that at the time of Charles the Bald every one who spoke Greek on the Continent was almost certainly an Irishman, or taught by an Irishman. By degrees Irish monasteries, built and supported by Irish money, spread over Europe from Holland to Tarentum, from Gaul to Bulgaria.

The Continent was therefore well known to Ireland when about 800 a.d. a new revolution passed over Europe.

Continental trade, as we have seen, had perished with the Roman Empire. Commerce had fallen to its lowest point. There was scarcely any money, nor in any country, neither England, nor France, nor Germany, a native class of merchants; wandering Jews and Greeks and Syrians, and later Italians, carried on what little buying and selling still survived. On the shores of the North Sea, however, the Frisians had made their town of Duurstede, near the mouth of the Rhine, a centre for traffic carried down the river; and in their stout, flat-bottomed, high-boarded sailing ships traded across the North Sea and the Baltic. Duurstede became for a time the chief port of western Europe. There Charles the Great coined money, and the lines along which the Frisian traders carried their wares may still be traced by the finding of the Duurstede coins. But even in the time of the Emperor Charles came the change which was to sweep away the Frisian traders. This was the rise of the new lords of the sea—the Scandinavians—who were to wrest commerce from Frisians and Gauls, and open a new trade for northern Europe.

The Scandinavians got their training in a hard school. They had a thousand miles of stormy shores to practice seamanship, fishing along their mountain coasts, and sailing against Arctic tempests round the North Cape. They had to build better ships than anyone else, and to sail them better. They invented a new kind of vessel where both oars and sails were used. And in a short time the Frisians were outdone both in seamanship and in trade.

East and west the Scandinavians sailed. As early as the eight century colonies of Swedes were passing by the Baltic and the gulf of Finland to settle on the opposite coast about Novgorod and along the Dnieper—the East way, as they called it. They left Scandinavian names along the rapids of the river as their travellers pushed forward, till in 839 they came in contact with the Greeks, and Swedes who had journeyed by the Dnieper were introduced by the Emperor of the East to the Western Emperor Louis the Pious. Their ships were soon the terror of the Black Sea shores—laden with warriors tall like palm trees, ruddy, fairhaired, who were in turn traders and plunderers, conquerors and slave-dealers. In 865 two hundred of their vessels appeared before Constantinople; in 880 they had reached the Sea of Azof, the Don and the Volga; in 913 they had five hundred ships, each carrying a hundred men, in the Caspian. Novgorod was the mart of their vast eastern commerce. There have been found in Sweden nearly twenty thousand Arabian coins, dating from 698 to 1002 a.d., carried across the Baltic by home-going merchants. Gothland became the general centre of exchange for the Eastway trade, where Danes sailed from their settlements on the Mecklenburg coast and the mouth of the Oder, to buy Russian furs, Greek and Arabian silks, and Indian spices, and here have been discovered thirteen thousand coins of the tenth and eleventh centuries—Byzantine, Arabian, and from central Asia.

Other adventurers from Norway and Denmark turned towards the Atlantic Ocean, trading and plundering in every harbour of the west, as far as Seville and the Spanish coasts. Northward they peopled Iceland and the Orkneys, and in time rounded the North Cape. They fished the Ocean for whales, and opened a trade in whale-meat and in the furs and cod of the White Sea with Normandy and England. The English liked better to buy than to catch whales. “Can you take a whale?” we read in an old West-Saxon dialogue. “Many,” says the home-loving Englishman, “take whales without danger, and then they get a great price, but I dare not from the fearfulness of my mind.”

Besides opening out this world-wide trade, the Scandinavians made a revolution also in the manner of trading. Up to this time buying and selling had been carried on by travelling dealers, Syrian and Italian. Now however Norsemen and Danes, who had no towns in their own lands, planted themselves in their new countries in fortified cities; and, for example, showed their enterprise by forming in the Five Danish Burghs in England the earliest federation of towns known outside Italy. In the new towns a settled class of merchants was established, who learned to group themselves according to the English system of guilds. The Scandinavians learned also to strike coins after the manner of the Frisians. In all these ways, by their new ships, their new trade routes, their money, their guilds, and their settled merchants in towns, the Scandinavians won a pre-eminence on the sea, which they were to hold in their own hands for some two hundred years.

What was the effect in Ireland of this new peril, an attack on Europe from the sea? In the first place the highways of the sea, never before closed, were barred by the Scandinavian free-booters. A few Irish travellers (even from Leinster) did even in 800 and 850 take the old accustomed journey to the Loire and so across France to Germany; but the passage was now dangerous. The terrors of the sea journey drove travellers to the land route, and the way across England to the Continent became so important that clerics of the tenth century could not imagine that any other way had ever been possible. The new sea-kings, moreover, were not the people to forget the ancient and profitable trade routes of the wine commerce, or the Irish harbours into which trading ships from north and south had sailed for the last two thousand years, or the gold that had been dug from Irish mines in old days. They seized every harbour, sent their boats up every creek and river, plundered the monasteries and wealthy houses, broke into every burial mound for treasure, and put a poll-tax on the men. Scholars and Christian monks fled from the heathen barbarians, carrying to Europe their treasures and manuscripts. The time of mere destruction, however, was not long. The Scandinavians were practical men of affairs, and Norsemen and Danes had settled in Ireland for business. The “Great Island,” as they called it, was a natural centre of their new world-wide commerce; lying within the trade circle formed by the ships that swept from the Orkneys and Hebrides round the Atlantic coast to the Loire and the Garonne, or that traversed the Irish Sea from Cantyre to Devonshire and Brittany. It was the shelter of voyaging ships, the recruiting ground of raiders, the winter-quarters of fleets; its commerce fell in naturally with the traffic of the western world. Danes and Irish were presently to the full as busy in trading as in fighting. Ireland became a commercial centre, a meeting place of the peoples. There came Grett with the Greek hat to buy captives for the Iceland market. A host of Saxons and Britons were brought over by Olaf and Ivar in 871. Almost every king of Norway sailed his fleet into Irish harbours, to drive off the rival Danish merchants, to broaden his traffic, to spy out some new store of gold, to load up with corn, to sweep the cattle down to the seashore for the “strand-hewing” that was to provision his crews with meat, fresh and salt, for their ocean course. Traders bargained then just as they bargain now. There is a harbour of Ardglass on the coast of County Down where a castle was built many centuries ago to protect the commerce of the port. The other day an Irishman repaired its ruins, and for a sign flew from it the flag of one of the Irish lords of the country, the Red Right Hand of O’Neill. At that very moment a light schooner sailed into the offing and at once flew in answer the Danish flag. The vessel was from Marsthal. Getting into port the crew bargained for herrings, counting out a hundred and ninety-five barrels of them by “chequers,” while the Ardglass men checked the number on notched sticks. Neither knew one word of the other’s tongue. So the Danes did business and sailed away, exactly as their forefathers had done a thousand years ago.