408 OCEANOGRAPHY. 



of facts carefully considered and elucidated. We shall say a few 

 words concerning' what has been done in this line of thought by differ- 

 ent nations, with the character which their peculiar temperament, the 

 conditions of their past and of their present have given to their work. 

 In fact, just as the acts of each man, physical as well as moral, are 

 marked with the special iinprint of his personality so in the domain of 

 science every race stamps its work, the product of its collective intel- 

 ligence, with an impress peculiar to it, which constitutes the very essence 

 of its genius. 



I. 



Oceanography is the study of the sea. Static oceanography deals 

 with salt water considered independently of the movements which are 

 manifested in it; it treats successively of the topography of the ocean 

 beds and of their formation, their lithology. It analyzes the waters, 

 their composition and their influence on the nature of the depths, their 

 numerous physical properties, the effect on them caused by changes of 

 temperature, their density, their compressibility, the way in which 

 light is diffused throughout the superposed strata, and the different 

 optical phenomena. The ice of the polar region offers subject matter 

 for a chapter on the effect of cold on the sea. 



In dynamic oceanography the ocean is studied in motion. We study 

 the waves, which move the surface under the influence of the wind, and 

 the currents, which, like the network of our arteries and veins, traverse 

 its mass to a certain depth, and result from the simultaneous actions 

 of heat, evaporation, the topography of the sea bottom, the geographic 

 configuration of the surrounding continents, the climate, the force of 

 the winds; in a word, from the total of exterior causes which, whatever 

 they may be, all exert some influence and in turn are influenced — a 

 constantly recurring cycle of change whose cessation would bring 

 instant death to our planet as the last beat of the human heart termi- 

 nates the life of the body. Dynamic oceanography also includes the 

 study of the tides, whose rhythmic movements accord with those of the 

 stars, and the examination of those processes by which the debris of 

 the continents, swept off by winds or washed away b} T rivers, reach the 

 great common reservoir, are diffused throughout its waters, descend in 

 a shower to the very lowest depths, and there accumulate to form 

 rocks like the greater part of those which we find now on our continents 

 and which formed the bottom of the oceans of former ages. It deals 

 with the phenomena that result from the contact between sea and 

 land, seeks out the laws which control the formation of deltas or of the 

 bars which extend across the mouths of rivers, the filling up of estua- 

 ries, the way in which waves and currents shape the contours of the 

 shores, dunes, lagoons, and those madreporic formations — atolls and 

 coral islands — conquests of organic life over inorganic matter, of the 

 infinitely small, the zoophyte, over the infinitely powerful, the ocean. 



