FIRST SECTION · THIRD CHAPTER · FIFTH PART · Third Article
Third Article
It describes the various movements of the seas.
O dear one! It should be known that philosophers and scholars of astronomy have unanimously stated as follows:
They have said: The element of water, namely the seas, has various movements.
The first movement is the movement downward. Since the element of water is connected to the element of earth, which possesses the quality of heaviness, by the nature of its constitution it moves toward the center, like the earth. The first movement of water is its natural movement downward.
The second movement is the undulating motion caused by the effect of winds.
The third movement is its movement from east to west. It has been experienced and established by all sailors that there is a current in the ocean from west to east. For example, those who depart from the Strait of Ceuta (Jabal Ṭāriq, i.e., Gibraltar) of the Mediterranean reach the New World (America) by way of the ocean in a month and a half heading west. And it takes them only four or five months to return eastward. Portuguese sailors, while traveling by way of the ocean from the New World to India, which is located on the lower side of the globe, have observed that the ocean flows eastward. Indeed, the existence of this movement has also been experienced in the Mediterranean. And the cause of this movement has been known from the daily motion of the greatest celestial sphere. For it has been found that the greatest celestial sphere secretly influences the ocean and causes it to rotate like the celestial spheres.
The fourth movement is the movement from north to south. This movement, too, has been proven by the experience of sailors. The cause of this movement has been known to be the fact that the land is somewhat elevated in the north. There are many great rivers flowing in the northern regions that have been found to aid the course of the oceans. For example, the Don River flows into the Sea of Azov, the Danube and others flow into the Black Sea, and thus contribute to the aforementioned current. Since the northern region is distant from the direct rays of the sun and its winters are cold, the waters in the seas increase and flow toward the southern regions.
The fifth movement is its circular movement (ḥarakat-i raḥviyya, i.e., rotary motion like a millstone). This movement occurs in the Mediterranean. Its cause is the movement of the water toward the east, which, upon reaching capes and gulfs, returns back. Thus, a broad/circular movement arises along those coasts.
The sixth movement is the movement of ebb and flow (tide). By this movement, the water of the seas reaches the shores in a manner of coming and going, remains for about six hours, and then returns again. Philosophers have disagreed about its cause, and most of them have said: "The entirety of beings in this material world (ʿālam al-shahāda) is a living being composed of the mixture of the four elements, subsisting with intellect and spirit (rūḥ), and moving and resting with a soul (nafs); one of its movements is ebb and flow." Some have said: "Ebb and flow arise from the breathing of living beings found within the oceans and those possessing spirit (rūḥ) around them."
Others have said: "Ebb and flow occur due to the effect of the wind generated by the movement of the sun." Yet others have said: "Ebb and flow occur due to the influence of the moon." Indeed, an explanation of this has been given above.
In summary, since there are many wisdoms and benefits in everything and every affair, [75/a] the constant movement of this element of water is not without meaning, and there are many benefits beneath it.
The first benefit is that, due to this movement, the seas do not become putrid. For with its movement, the heaviness that would cause putrefaction is dispersed. For example, if a person were to walk toward the sun at an average pace, he would experience and be certain that this is the case (that the movement of water prevents putrefaction). For a person standing in the sun is not affected by its heat as much as one sitting still in place.
The second benefit is the purification of sea water due to ebb and flow. For stagnant waters are generally dirty and harmful. However, in the moving and undulating sea water, filth does not remain; the waves drive it to the shore and the water remains clean.
The third benefit is the general advantage of the movements of ebb and flow for ships. For there are some docks to which, if there were no ebb, it would not be possible to approach; ships would not be able to enter them. With the ease provided by the phenomenon of ebb, ships can easily depart from these harbors and are not left stranded.