Cæsar soon after collected about eighty vessels of burden, placed in them two legions, and, having made his final arrangements, started for England from Boulogne at midnight on August 26, B.C. 55, having on board a force of about eight thousand men. Eighteen other transports conveyed about eight hundred horses for the cavalry.[426] Beyond the number of the vessels, Cæsar has left us no information in regard to them, and no indication of their capacity beyond the incidental statement that two of the galleys, which on his return got adrift, carried altogether three hundred men. The number of men constituting a legion varied very much during the different periods of Roman history, and, in Cæsar’s time, amounted to about five thousand two hundred and eighty men, all told; but as Cæsar obviously took with him as few troops as possible, intending his first descent upon England to be rather a visit of observation than a conquest, it is likely that the whole number of his force did not exceed what we have stated, making for each of the eighty galleys a complement of somewhere about one hundred men. [Sidenote: Size of his transports.] At present about three hundred passengers can be accommodated in a sailing vessel of one thousand tons register on a distant voyage; but, in coasting vessels, the number is very much greater.[427] It may therefore be assumed that the average size of the vessels in which Cæsar embarked his legions on this occasion was not more than one hundred tons register. The horse transports[428] may have been somewhat larger, as more than thirty-three horses, with their provender, water, and attendants, could not well be conveyed in a vessel of less register than one hundred tons, even on so short a voyage as from Boulogne to Romney[429] or Lymne, performed, as this voyage was, with a fair wind, in fifteen hours, or at the rate of about two miles an hour. The ships of burden or transports were all flat-bottomed, that they might float in shallow water, and be more expeditiously freighted. Although the facts preserved with regard to the ships which Cæsar employed on his first invasion are of the most meagre description, they are sufficient to show that they drew comparatively little water, or the men could not have “jumped” out of them, and made good their footing on the beach with their standard and arms against the whole British force: most likely, they were rather good stout-decked or half-decked barges than the ordinary sea-going coasting vessel, which, if one hundred tons burden, would draw, when laden, from seven to eight feet of water. There is no record of the ports where these vessels were constructed; but some of them, Cæsar tells us, had been employed by him, earlier in the same year, in his war with the Veneti. [Sidenote: Second invasion, B.C. 54.]