The earliest evidence for the presence of these 'Rus' in Eastern Europe is found in the story of the Byzantine embassy to the emperor Lewis the Pious in 839 (_v. supra_, p. 19), when certain people called 'Rhôs,' who had been on a visit to Constantinople, came in the train of the embassy and asked leave to return home through the empire. Enquiries were made and it was found that these 'Rhôs' were Swedes. This would point to the presence of 'Rus' in Russia at a date earlier than that given by Nestor, and indeed the rapid extension of their influence indicates a period of activity considerably longer than that allowed by him. These 'Rus' or 'Rhôs' soon came into relations, both of trade and war, with the Byzantine empire. We have preserved to us from the years 911 and 944 commercial treaties made between the 'Rus' and the Greeks showing that they brought all kinds of furs and also slaves to Constantinople, receiving in exchange various articles of luxury including gold and silver ornaments, silks and other rich stuffs. The names of the signatories to these treaties are, on the side of the 'Rus,' almost entirely of Scandinavian origin and may to some extent be shown to be of definitely Swedish provenance. About the year 950, the emperor Constantine Porphyrogenitus, writing a tractate on the administration of the empire, describes how traders from various parts of Russia assemble at Kiev and sail down the Dnieper on their way to Constantinople. Their course down the Dnieper was impeded by a series of rapids, and Constantine gives their names both in 'Russian' and in Slavonic form, and though the names are extremely corrupt in their Greek transcription there is no mistaking that the 'Russian' names are really forms belonging to some Scandinavian dialect. The Rus were also well known as warriors and raiders. In 865 they sailed down the Dnieper, across the Black Sea and made their way into the Sea of Marmora. Their fleet was dispersed by a storm, but they were more successful in 907 when Oleg with some 2000 ships harried the environs of Constantinople and was bought off by a heavy tribute. These attacks were continued at intervals during the next century.