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418 pressure more and more considerable, then with different temperatures, and each time note the variations resulting from the influence of each of these variables. Suppose that we have experimented carefully and tested separately everything that reason, ordinary common sense, points out as playing a part in the descent of dust particles through the ocean. If we then verify, first in a lake, then in the ocean, each of the laws discovered in the laboratory; if we determine that in the latter they are simply multiplied by a number, the constant coefficient of increase, we shall refute the critics. If there is a disagreement, we are apprised of the influence of some variable of which we have not taken account; and it will be necessary, after having discovered it, to experiment on it in turn. When all the work is finished we shall have the proof that, while with a single experiment taken separately we can not analyze nature, with the entire series we can do so.

It is thus that we should consider oceanography, which, proceeding upon the plan of not studying the past until the present is well understood, has introduced the experimental method into all that part of geology relative to sedimentary deposits. It is thus properly a branch of this science.

When a traveler, overcome by the long and painful ascent of a mountain, finally reaches the summit, he finds it pleasant to him to sit on a rock and, while recovering from his fatigue, contemplate the plain which he has crossed, the river whose windings he has followed and which at this moment spreads out below him, and also the difficult, even dangerous, ground, the sand, the marshes, over which he has come with great exertion. Certain stages of the journey had seemed to him short, others had appeared very long, and now he calculates what they are in reality. He distinguishes each error that he has committed. If, then, turning round, he looks down the other slope of the mountain, he sees what road he must follow to arrive surely and promptly at the end of his journey, visible afar in the mist of the horizon. What he has done gives him courage to complete his task; the victory he has won over fatigue and obstacles is the warrant of his victory over the fatigues and difficulties of the future. He gathers new ardor, strength, and hope. Is not this traveler like the man of science in his journey, laborious and painful as is all travail, toward the distant truth which, in his short life, he is certain never to reach? At least he will approach it at the cost of many mistakes. He has opened up the path, and those who follow behind him, profiting by his labor, will surpass him. They will go on farther and yet farther, obedient to that thirst for truth with which God has endowed every human soul as a mark of its divine origin and future immortality.

It is necessary to know the history of a science to understand those works with which it deals and to foresee those which remain for it to accomplish. Let us now show in the history of oceanography how its development has been influenced by different sciences and how it