THE PHYSICAL CONDITION OF THE OCEAN. 349 



maritime nations have aided. In the immediate past the additions have 

 mainly been from the soundings which Her Majesty's surveying ships 

 continually take whenever on passage from one place to another, from 

 the work of our cable companies, and from United States vessels. We 

 have as a result a very fjiir general knowledge of the prevailing depths 

 in the Atlantic, but of the Indian and Pacific oceans it is very fragmen- 

 tary. We have enough to give us a general idea, but our requirements 

 increase as years roll on. It is a vast task, and it may be safely said 

 will never be completed, for we shall never be satislied until we know 

 the variations of level under the water as well as we know those on the 

 dry land. 



It is hopeless to do more than to briefly sketch the amount of our 

 knowledge. First, as to the greatest depths known. It is very remark- 

 able, and from a geological point of view significant, that the very deep- 

 est parts of the ocean are not in or near their centers, but in all cases are 

 very near land. One hundred and ten miles outside the Kurile Islands, 

 which stretch from the northern point of Japan to the northeast, the 

 deepest sounding has been obtained of 4,655 fathoms, or 27,930 feet. 

 This appears to be in a deep depression, which runs i)arallel to the Kurile 

 Islands and Japan, but its extent is unknown, and may be very large. 

 Seventy miles north of Puerto Eico, in the West Indies, is the next deep- 

 est cast known, viz, 4,561 fathoms, or 27,366 feet — not far inferior to the 

 Pacific depth; but here the deep area must be comparatively small, as 

 shallower soundings have been made at distances 60 miles north and 

 east of it. A similar depression has been sounded during the last few 

 years west of the great range of the Andes at a distance of 50 miles 

 from the coast of Peru, where the greatest depth is 4,175 fathoms. 

 Other isolated depths of over 4,000 fathoms have been sounded in the 

 Pacific — one between the Tonga or Friendly Islands of 4,500 fathoms, 

 one of 4,478 fathoms near the Ladrones, and another of 4,428 fathoms 

 near Pylstaart Island, all in the Western Pacific. They all require 

 further investigation to determine their extent. With these few excep- 

 tions the depth of the oceans so far as yet known nowhere comes up to 

 4,000 fathoms, or 4 sea miles, but there can be little doubt that other 

 similar hollows are yet to be found. 



The sea with the greatest mean depth apjiears to be the vast Pacific, 

 which covers 67,000,000 of the 188,000,000 of square miles composing 

 the earth's surface. Of these 188,000,000, 137,000,000 are sea, so that 

 the Pacific comprises just one-half of the water of the globe and more 

 than one-third of its whole area. The Northern Pacific has been esti- 

 mated by Mr. John Murray to have a mean depth of over 2,500 fathoms, 

 while the Southern Pacific is credited with a little under 2,400 fathoms. 

 These figures are based on a number of soundings, which can not be 

 designated otherwise than very sparse. 



To give an idea of what remains to be done I will mention that in the 

 eastern i)art of the Central Pacific there is an area of 10,500,000 square 



