The foregoing considerations enable us to appreciate in its principal characteristics the method employed in oceanography. The application of experiment and of measurement seems at first particularly difficult, if not impossible. It is neither. As regards the ocean, it is certain that the phenomena apparent there are more than complicated—they are terrible; and their grandeur apparently puts them far beyond the power of man. It would be of no use to approach the study directly. However, even the forces of the sea are forced to yield to experimentation on condition that we proceed gradually, studying first lakes—oceans in miniature, governed by laws similar, although less complicated, and consequently more easy to discover and verify. In oceanography a phenomenon must pass through three phases of study: It is established on the ocean, found in lesser degree on lakes, and studied by synthesis in the laboratory. Thus its law is discovered. Then, taking the inverse order, it is ascertained whether the law is verified on lakes, and at last we come back to the ocean. We observe whether the law holds good there, and in case of modifications (which usually occur) we seek their causes and consider what new elements have become involved which were absent, or perchance ineffective, on lakes or in the laboratory. The study is now complete and definite, since, if necessary, we may return to the laboratory, where, rich in the suggestions which have arisen from our new survey, fortified by a first approximation, we can arrive at a greater precision, thanks to a new synthesis established by new experiments. We work from the known to the unknown and from the simple to the complex, retracing our steps if necessary.
The objection has been made to the experimental method that phenomena in miniature such as we can produce in the laboratory are not identical with natural phenomena, since they represent them on a reduced scale. This reasoning rests on a misunderstanding; everything goes to prove the contrary. Why should a heavy body left unsupported descend into the sea in any different manner than it descends in a tube some meters in height filled with salt water? If the changes are brought about by the duration of the fall, the depth, the pressure of the layers of water, and other circumstances, these changes can be studied and estimated by means of separate experiments. It is the usual method of resolving a natural phenomenon by means of curves of a single equation with multiple variables. Admitting that in certain cases a single experiment in the laboratory is insufficient to reproduce the phenomenon, yet a series of experiments, each of which would be performed to make clear the action of one of the components of the problem, would represent it in its entirety. When, for example, we have measured in a tube 3 or 4 meters long the duration of the fall of globigerina in sea water, we evidently do not learn all the laws of such a fall in the sea. It would be otherwise if, after having made the experiment with ordinary pressure, we repeat it with
