The army accordingly halted, and the necessary arrangements were made for the review. The first thing was to ascertain the numbers of the troops; and as the soldiers were too numerous to be counted, Xerxes determined to _measure_ the mighty mass as so much bulk, and then ascertain the numbers by a computation. They made the measure itself in the following manner: They counted off, first, ten thousand men, and brought them together in a compact circular mass, in the middle of the plain, and then marked a line upon the ground inclosing them. Upon this line, thus determined, they built a stone wall, about four feet high, with openings on opposite sides of it, by which men might enter and go out. When the wall was built, soldiers were sent into the inclosure--just as corn would be poured by a husbandman into a wooden peck--until it was full. The mass thus required to fill the inclosure was deemed and taken to be ten thousand men. This was the first filling of the measure. These men were then ordered to retire, and a fresh mass was introduced, and so on until the whole army was measured. The inclosure was filled one hundred and seventy times with the foot soldiers before the process was completed, indicating, as the total amount of the infantry of the army, a force of one million seven hundred thousand men. This enumeration, it must be remembered, included the land forces alone. This method of measuring the army in bulk was applied only to the foot soldiers; they constituted the great mass of the forces convened. There were, however, various other bodies of troops in the army, which, from their nature, were more systematically organized than the common foot soldiers, and so their numbers were known by the regular enrollment. There was, for example, a cavalry force of eighty thousand men. There was also a corps of Arabs, on camels, and another of Egyptians, in war chariots, which together amounted to twenty thousand. Then, besides these land forces, there were half a million of men in the fleet. Immense as these numbers are, they were still further increased, as the army moved on, by Xerxes's system of compelling the forces of every kingdom and province through which he passed to join the expedition; so that, at length, when the Persian king fairly entered the heart of the Greek territory, Herodotus, the great narrator of his history, in summing up the whole number of men regularly connected with the army, makes a total of about five millions of men. One hundred thousand men, which is but one fiftieth part of five millions, is considered, in modern times, an immense army; and, in fact, half even of that number was thought, in the time of the American Revolution, a sufficient force to threaten the colonies with overwhelming destruction. "If ten thousand men will not do to put down the rebellion," said an orator in the House of Commons, "fifty thousand _shall_."