52 A Retrospect of Oceanography 



was the Seine bank, and it had been discovered the year before 

 by the s.s. "Seine," belonging to the Telegraph Construction 

 and Maintenance Company. While she was laying the second 

 Brazilian cable between Portugal and Madeira, and in water 

 which she had every reason to believe to be about 2000 fathoms, 

 the cable suddenly parted, and, on sounding, the depth was 

 found to be no fathoms. Instead of being laid along a plain, 

 the ship was quite unawares laying it over the top of an isolated 

 peak some 12,000 feet high. It is needless to say that the 

 precautions to be observed in laying over such ground are 

 different from those demanded by a level bottom, and the 

 result was rupture of the cable and detention of the ship. 

 Unwittingly and unwillingly, the ship had made an important 

 oceanographical discovery. It was to avoid making such 

 discoveries in a similar way that the "Dacia" did her best 

 to find them in the preliminary survey, and was successful. 

 The Lisbon-Madeira route had been surveyed by soundings 

 about 30 miles apart, and when this enormous submarine 

 mountain, the Seine bank, occurred, there was nothing in 

 the soundings to indicate its existence but a slight shoaling 

 from 2100 to 1800 fathoms. It was by taking this lesson 

 to heart, and looking on a slight shoaling, even in very deep 

 water, as the possible indication of the existence of a formidable 

 shoal in the neighbourhood, that the "Dacia's" researches 

 had the success that rewarded them. 



It is not only in laying cables that the ships engaged in 

 this work add to our knowledge of the bed of the ocean ; it is 

 in the repairing and recovering operations that we obtain minute 

 and detailed information which cannot be got otherwise. 

 The causes themselves of the rupture of a cable, which may 

 have been laid for years and worked well, are of interest, but 

 not always easy to ascertain. In one place the cable may 

 have got covered up by mud, and all attempts to hook it with 

 the grapnel are fruitless ; the ship has to follow its line, dragging 

 across it frequently with the grapnel, until she comes on it 

 lying bare on the bottom. What are the causes which cover 

 it in one place and leave it bare in another? In warm and 

 shallow seas the cable gets quickly grown over by corals and 



