Another mode was by rude astronomical observations, which must have been resorted to in the very earliest periods. For a good portion of the year, the sun was seen to come regularly north. Then he remained apparently stationary; and then, slowly _turning_, made his retreat again to the southern limit, there to perform the same movement--and so on without interruption or variation. Hence the word _tropic_, signifying the _turning_, and of which St. James makes so sublime and beautiful a use when he tells us (James i. 17) that the Unchangeable Spiritual Sun, or "Father of Lights," has no _parallax_[6] and no "_shadow of turning_," or _tropical shadow_, as it should be rendered, referring to the mode of determining the period of _turning_ by the shortest shadow cast by a perpendicular object. Still all this was merely an approximation to the length of the year, but with errors which only repeated observations could correct. By taking, however, a large number of these self-repeating repeating phenomena for a divisor, and the whole number of carefully ascertained days for a dividend, the error in each case would be diminished in an inverse ratio; so that we should not wonder that the number of three hundred and sixty-five days was fixed upon at quite an early period. [6] The word parallax, or "_parallage_," here must refer to the sun's declination north and south of the equator. We have no reason for supposing that the ideas connected with the term in modern astronomical science were at all known to the Apostle. It may, however, be taken generally, for any deviation from one unchangeable position, and, in such a sense, preserve all the beauty and sublimity of the metaphor.