OCEANOGRAPHY. 409 



Oceanography has to do then, directly or indirectly, with a multi- 

 tude of sciences and, more than any other, with geology. The present 

 is at the same time the key of the past and of the future, especially in 

 natural history. Man, in his investigations, works from the known to 

 the unknown, from what he can see with his eyes, touch with his hands, 

 measure with his instruments, to that of which he can perceive only 

 the results ; from phenomena present before him to those which were 

 accomplished thousands of centuries ago. For a long time geology 

 advanced in a rut out of which oceanography has forced it perhaps a 

 little against its inclination. Old people and old sciences have their 

 habits and a dislike to change, but old sciences, more fortunate than 

 man, can grow young again. 



Rocks are of igneous or metamorphic and of sedimentary origin. The 

 former are the object of the researches of a special science, petrogra- 

 phy, which studies their intimate nature and all the different branches 

 of knowledge which relate to eruptive phenomena. Stratigraphy deals 

 with rocks of aqueous formation, and, as the genesis of these is inti- 

 mately connected with the order of their superposition, stratigraphists, 

 in their investigations, consider together the constitution and the order 

 of the sedimentary strata. Now, since these strata have been found 

 beneath the water, nothing is more fitted to make their genesis clear 

 than observation of the manner in which at the present time rocks are 

 being formed on the bottom of our oceans. This task, to which it 

 applies itself with ardor, is the duty of oceanography. When the par- 

 ticular character of the formations on the coasts or in the depth of the 

 sea is known, when careful observation and exact measurement of 

 actual phenomena shall have taught, for example, the necessary rela- 

 tion between the form and dimensions of a grain of sand and the 

 exact velocity of the current which has transported it and affected its 

 shape — angular when supported by force of the water, worn and 

 rounded when simply rolled along the bottom among other grains; as 

 soon as the presence, recognized quantitatively, of a fixed proportion 

 of clay in the midst of a sandy deposit shall allow us, by means of 

 physical and mechanical laws, to determine whether this deposit was 

 formed in calm or agitated water; as soon as numerous measurements, 

 repeated in different parts of the ocean, shall have established the 

 generality of these relations — that is to say, made laws for them — we 

 shall be ready to reconstruct the past. It will be sufficient to find 

 the same characteristics in an old deposit to be able to call established 

 relations to our aid. We may affirm that the point where the deposit 

 was formed was at such and such a depth in the ocean, at such a dis- 

 tance from the shore. If, later, other sciences bring forward their 

 cooperation and point out new relations, all the details will, one after 

 another, appear. We shall then ascertain the size and form of the 

 Silurian, the Carboniferous or the Cretaceous Sea, the force of its waves, 

 its salinity, the temperature of its waters, the intensity and direction 



