The earliest of these expeditions seem to have been annual visitations; and as the northern winter sets in about October, and the Baltic is seldom navigable before May, the summer was the season of their depredations. Awaiting the breaking up of the ice, the intrepid adventurers assembled annually upon the islands in the Cattegat or on the coast of Norway, awaiting the favourable moment of departure. Here they beguiled their time between the heathen rites they rendered to their gods, their wild bacchanal festivals, and the equipment of their galleys. The largest ship built in Norway, and probably in the north, before the eleventh century, had 34 banks of oars. The largest class of vessel carried from 100 to 120 men. The great fleet which invaded Ireland in 837 counted 120 vessels, which, if of average size for such long voyages, would give a total force of some 6,000 men. As the whole population of Denmark, in the reign of Canute who died in 1035, is estimated at 800,000 souls, we may judge from their fleets how large a portion of the men were engaged in these piratical pursuits. The ships on which they prided themselves so highly were flat-bottomed craft, with little or no keel, the sides of wicker work, covered with strong hides. They were impelled either by sails or oars as the changes of the weather allowed; with favourable winds they often made the voyage in three days. As if to favour their designs, the north and north-west blast blows for a hundred days of the year over the sea they had to traverse. When land was made, in some safe estuary, their galleys were drawn up on shore, a convenient distance beyond highwater mark, where they formed a rude camp, watch-fires were lighted, sentinels set, and the fearless adventurers slept as soundly as if under their own roofs, in their own country. Their revels after victory, or on returning to their homes, were as boisterous as their lives. In food they looked more to quantity than quality, and one of their most determined prejudices against Christianity was that it did not sanction the eating of horse flesh. An exhilarating beer, made from heath, or from the spruce tree, was their principal beverage, and the recital of their own adventures, or the national songs of the Scalds, were their most cherished amusement. Many of the Vikings were themselves Scalds, and excelled, as might be expected, in the composition of war songs.