Our Salt-JFater JForld 319 



the ship's logs of to-day have special headings under 

 which are listed the various phenomena as they occur 

 on the surface. But undoubtedly the greatest advances 

 in oceanography were occasioned by the researches of 

 those expeditions made in vessels especially equipped 

 for the purposes of exploration and Investigation. Ob- 

 viously, these are costly affairs and are not often under- 

 taken; but limited as have been these enterprises, their 

 achievements have been remarkable. Various govern- 

 ments and private individuals have by means of these 

 expeditions done much to further our knowledge of the 

 open sea; however, the most noteworthy expedition 

 may be said to be that of the Challenger^ which was 

 really the scientific pioneer of the seas. This vessel, 

 under the English flag, made a voyage starting In 

 December 7, 1872, and lasting until May 24, 1876. In 

 this period of three and one half years she several times 

 crossed and recrossed various seas; having covered in 

 the entire length of the cruise nearly 69,000 nautical 

 miles. From the time of this epoch-marking event 

 dates the beginning of oceanography as a science of 

 precision. 



Not only is the area of the sea larger than that of the 

 land, but Its volume Is also greater. If the entire ex- 

 posed portion of the earth were dumped Into the ocean, 

 It would not take up more than one fourth of the space 

 occupied by the water; in short. It would be covered by 

 an ocean 8,700 feet In depth. The mean elevation of 

 the land above the sea level owtv the whole world is 

 less than half a mile; this is to say that If all the moun- 

 tains and high portions of land could be made to fill 

 the low parts the leveled earth would rise above the sea 



