Croesus sent embassadors to Sparta to inform the people of the plans which he contemplated, and to ask their aid. He had been instructed, he said, by the oracle at Delphi, to seek the alliance of the most powerful of the states of Greece, and he accordingly made application to them. They were gratified with the compliment implied in selecting them, and acceded readily to his proposal. Besides, they were already on very friendly terms with Croesus; for, some years before, they had sent to him to procure some gold for a statue which they had occasion to erect, offering to give an equivalent for the value of it in such productions as their country afforded. Croesus supplied them with the gold that they needed, but generously refused to receive any return. In the mean time, Croesus went on, energetically, at Sardis, making the preparations for his campaign. One of his counselors, whose name was Sardaris, ventured, one day, strongly to dissuade him from undertaking the expedition. "You have nothing to gain by it," said he, "if you succeed, and every thing to lose if you fail. Consider what sort of people these Persians are whom you are going to combat. They live in the most rude and simple manner, without luxuries, without pleasures, without wealth. If you conquer their country, you will find nothing in it worth bringing away. On the other hand, if they conquer you, they will come like a vast band of plunderers into Lydia, where there is every thing to tempt and reward them. I counsel you to leave them alone, and to remain on this side the Halys, thankful if Cyrus will be contented to remain on the other." But Croesus was not in a mood of mind to be persuaded by such reasoning. When all things were ready, the army commenced its march and moved eastward, through one province of Asia Minor after another, until they reached the Halys. This river is a considerable stream, which rises in the interior of the country, and flows northward into the Euxine Sea. The army encamped on the banks of it, and some plan was to be formed for crossing the stream. In accomplishing this object, Croesus was aided by a very celebrated engineer who accompanied his army, named Thales. Thales was a native of Miletus, and is generally called in history, Thales the Milesian. He was a very able mathematician and calculator, and many accounts remain of the discoveries and performances by which he acquired his renown. For example, in the course of his travels, he at one time visited Egypt, and while there, he contrived a very simple way of measuring the height of the pyramids. He set up a pole on the plain in an upright position, and then measured the pole and also its shadow. He also measured the length of the shadow of the pyramid. He then calculated the height of the pyramid by this proportion: as the length of shadow of the pole is to that of the pole itself, so is the length of the shadow of the pyramid to its height.