XVIII 



The Deepest Depths 



ON the way south from Japan to Maniis Dr. Gaskell had 

 said that he wished to carry out one of his seismic experi- 

 ments in a deep trench in order to find out something of 

 the structure of the sea-floor in such an area. So, as the ship moved 

 into the Marianas Trench between Guam and UHthi, John 

 Swallow was active with the seismic gear, using it purely as a 

 reflection or sounding machine to record the time of the double 

 passage of sound from the small charge he exploded until it 

 returned as an echo from the sea-bed to his hydrophone, thus 

 giving him the depth. The soundings rapidly increased and soon 

 Swallow was reporting over 5^000 fathoms and finally ^663 

 fathoms. 



This was an exciting report, for it was known to be nearly as 

 deep as any sounding so far recorded. But unfortunately it was 

 about 1000 fathoms beyond the scope of the deep echo sounding 

 machine at this time. But using the taut wire machine, with 140 

 pounds of scrap iron attached to the end of the wire, as a sounding 

 machine, a depth of _^899 fathoms was recorded. This was a new 

 deep record for the world. 



The history of deep sounding in the ocean is not a long one. It 

 was during Lord Mulgrave's expedition to the Arctic in 1773 

 that some of the earliest attempts at deep sounding were made, 

 the greatest depth sounded being 683 fathoms, from whence a 

 sample of sediment was obtained. 



In 1 8 1 7— 1 8 Sir John Ross, during a voyage to Baffin Bay, made 

 some deep sea soundings using a 'deep sea clamm' on the end 

 of his rope which brought up several pounds of greenish mud 

 from his deepest sounding of 10^0 fathoms. 



Sir James Clark Ross led an expedition to the Antarctic in the 

 ships Erebus and Terror in the years 1839-43, during which time 

 he really started systematic deep sea sounding. He had a line 3600 

 fathoms long made up onboard, and this he allowed to run out 



225 



