Along the British Pacific Cable. 307 



nautical mile. On the Fanning-Suva section 220 lbs. of cop- 

 per and 180 lbs. of gutta percha ; and on the remaining three 

 sections the copper and dielectric were in equal proportions of 

 130 lbs. each. 



In the neighborhood of Fiji at a depth of 2500 fathoms, 

 a temperature of 34. 1° Fahrenheit was noted, being the 

 lowest temperature taken during the survey. There is very 

 little difference in the temperature of the ocean at great depths, 

 say below 3000 fathoms, over a great extent of the earth's sur- 

 face, the temperature being only a few degrees above the freez- 

 ing point, or 32 ° Fahrenheit. The greatest depth, 3070 fathoms, 

 about three and a half miles, was found on the Fiji-Fanning 

 section, where the bottom specimens consisted principally 

 of radiolarian ooze. This ooze is found at the greatest depths, 

 and was obtained by the Challenger's deepest sounding in 

 4475 fathoms. The United States steamer Nero sounded 

 in 5269 fathoms, 6 miles (this last being the deepest sounding 

 recorded in the ocean), and the material brought from the 

 bottom was radiolarian ooze. Of the 597 samples of sea bot- 

 tom obtained on the Pacific Cable survey, 497 were such that 

 they could be divided into distinct types of deposits It was 

 found that 



294 samples referred to globigerina ooze 1 



65 

 43 

 45 

 27 

 12 

 1 1 



red clay 



radiolarian ooze 

 coral mud or sand 

 pteropod ooze 

 blue or green muds 

 organic mud or clay. 



The pressure at a depth of 3000 fathoms, in which a con- 

 siderable portion of the Pacific Cable is laid, is about four tons 

 to the square inch. When the cable is being laid at such 

 depths, it will be approximately twenty miles astern of the ship 

 before it touches the bottom. 



Deep sea cables last longer in the tropics than in the 

 northern oceans. The reason is to be found in the fact that in 

 the tropics marine life, from which globigerina ooze is derived, 



1. Report by Sir John Murray. 



