Zosimus, New History 3.10
Zosimus (Greek Ζώσιμος): Early Byzantine, pagan author of a history of the Roman Empire, published in the first quarter of the sixth century CE.
The translation of Zosimus' New History offered here was printed in 1814 by W. Green and T. Chaplin in London, and was probably prepared by J. Davis of the Military Chronicle and Military Classics Office. The translator is anonymous. The text was found at Tertullian.org. The notes were added by Jona Lendering.
[3.10.1] The summer being advanced, he had no sooner settled affairs among the barbarians beyond the Rhine, having in part forced them to moderation by the sword, and partly persuaded them by experience of the past to prefer peace to war, than he put his army in a posture to take a long journey, and having appointed officers both civil and military to govern the towns and the borders, he marched his army towards the Alps.
[3.10.2] Upon his arrival in Raetia, where the river Ister rises, which runs through Noricum, Pannonia, Dacia, Moesia, and Scythia, until it empties itself in the Euxine Sea, he constructed a number of boats, and with three thousand of his troops sailed down the Ister, commanding twenty thousand of them to march by land to Sirmium.
[3.10.3] As they rowed with the stream, and had the advantage of the annual winds called Etesian he arrived on the eleventh day at Sirmium. When it was reported there that the emperor was arrived, the people thought that Constantius was the person meant; but on finding that it was Julian, they were amazed, as if they had taken him for an apparition. The army from Celtica having joined him, he wrote to the Roman Senate, and to the forces in Italy, desiring them to keep their cities safe, he being the emperor.
[3.10.4] As Taurus and Florentius, the consuls for that year, left Rome as soon as they heard that Julian had crossed the Alps into Pannonia, he ordered them to be stiled the fugitive consuls in all public instruments. He behaved with great kindness to all the towns he passed through, and though in great haste, gave them all good expectations of him. He likewise wrote to the Athenians, the Lacedaemonians, and the Corinthians, to inform them of the reason of his approach.