It is evident that before the astronomers at Nineveh could foretell eclipses, they had achieved considerable progress as scientists. The data at their disposal probably covered nearly two thousand years. Mr. Brown, junior, calculates that the signs of the Zodiac were fixed in the year 2084 B.C.[350] These star groups do not now occupy the positions in which they were observed by the early astronomers, because the revolving earth is rocking like a top, with the result that the pole does not always keep pointing at the same spot in the heavens. Each year the meeting-place of the imaginary lines of the ecliptic and equator is moving westward at the rate of about fifty seconds. In time--ages hence--the pole will circle round to the point it spun at when the constellations were named by the Babylonians. It is by calculating the period occupied by this world-curve that the date 2084 B.C. has been arrived at. As a result of the world-rocking process, the present-day "signs of the Zodiac" do not correspond with the constellations. In March, for instance, when the sun crosses the equator it enters the sign of the Ram (Aries), but does not reach the constellation till the 20th, as the comparative table shows on p. 308. When "the ecliptic was marked off into the twelve regions" and the signs of the Zodiac were designated, "the year of three hundred sixty-five and one-fourth days was known", says Goodspeed, "though the common year was reckoned according to twelve months of thirty days each[351], and equated with the solar year by intercalating a month at the proper times.... The month was divided into weeks of seven days.... The clepsydra and the sundial were Babylonian inventions for measuring time."[352] The sundial of Ahaz was probably of Babylonian design. When the shadow went "ten degrees backward" (_2 Kings_, xx, II) ambassadors were sent from Babylon "to enquire of the wonder that was done in the land" (_2 Chron._ xxxii, 31). It was believed that the king's illness was connected with the incident. According to astronomical calculation there was a partial eclipse of the sun which was visible at Jerusalem on 11th January, 689 B.C, about 11.30 a.m. When the upper part of the solar disc was obscured, the shadow on the dial was strangely affected. The Babylonian astrologers in their official documents were more concerned regarding international omens than those which affected individuals. They made observations not only of the stars, but also the moon, which, as has been shown, was one of their planets, and took note of the clouds and the wind likewise.