42 THE OCEAN 



3000 fathoms, and in some cases exceeding 

 4000 and even 5000 fathoms in depth. 

 The contour-Hnes of depth are as a rule very 

 irregular, the average depth varying from 

 1500 to 2500 fathoms, with innumerable 

 volcanic ridges rising almost or quite to the 

 surface, their summits for the most part 

 crowned by coral reefs. The Coral Sea, 

 lying between Australia, New Guinea, New 

 Hebrides and New Caledonia, forms a deep 

 oceanic basin exceeding 2500 fathoms in 

 depth, but cut off from the general oceanic 

 circulation by barriers covered by about 1300 

 fathoms of water, as proved by the " Chal- 

 lenger " temperature observations, which 

 showed that at all depths beyond 1300 fathoms 

 the temperature was uniform at 36° F. The 

 region to the east of Australia is remarkable 

 for the number of submarine elevations 

 revealed by recent soundings, such as the 

 " Britannia Hills," discovered in 1903 to the 

 east of Southport, Queensland, covered by less 

 than 300 fathoms, and the Balfour Shoal, 

 described by the writer in 1897, covered by 

 836 fathoms of water. The Pacific Ocean 

 extending northwards from the Antarctic 

 Continent to Bering Strait is estimated to 

 cover an area of about 69 millions of square 

 miles, distributed according to depth as 

 follows : — 



