There is some indication in the Georgics of the manner in which the ancient seamen made use of stars and weatherology. “As carefully must the star of Arcturus, and the days of the Kids, and the bright Dragon be observed by us on land, as by those who, homewards bound across the stormy seas, venture to the Euxine and the straits of oyster-breeding Abydos.” ... “Hence we can learn coming changes of weather in the dubious sky, hence the days of harvest and the season of sowing, and when ’tis meet with oars to cut the faithless sea, when to launch our rigged fleets, and when at the proper time to fell the pine tree in the woods: nor will you be disappointed, if you watch the setting and rising of the heavenly signs, and observe the year fairly divided by four distinct seasons.” ... “Straightway, when winds arise, either the straits of the sea begin to swell with agitation, and a dry crash is heard on the high hills, or far in the distance the shores are filled with confused echoes, and the murmur of the woods thickens on the ear. The wave can but ill forbear to do a mischief to the crooked keels, even when gulls fly swiftly back from the high sea, sending their screams before them.... Oft too, when wind impends, you will see stars shoot headlong from the sky.... But when it lightens from the quarter of grim Boreas, and when the home of Eurus and Zephyrus thunders, then are the dykes filled and all the country is flooded, and every mariner out at sea furls his dripping sails.... The sun also, both when rising and when he hides himself beneath the waves, will give you signs; infallible signs attend the sun ... a blue colour announces rain, or fiery winds; but if the spots begin to be mixed with glowing red, then you will see all nature rage with wind and stormy rain together. On such a night let no one advise me to venture on the deep, or pluck my cable from its mooring on the shore.” CHAPTER VI THE VIKING MARINERS War has always been a great incentive to shipbuilding. But this statement requires modification by excluding both civil war and the merchant ship. Of the former, no better instance could be found than the disastrous Wars of the Roses. Of the latter, the manner in which the Romans and others developed the war-galley at the neglect of the merchant ship is a clear example.