PHYSICAL OCEANOGRAPHY 265 



still that we could work with the current-meters from deck, but 

 the strain on the wire was enormous. Double staying is much 

 too difficult at great depths, although a single line may some- 

 times do. At Station 58, south of the Azores, we had the 

 trawl out in about 900 metres of water, when it caught on 

 something and stuck fast on the bottom, holding the ship 

 practically still (the compass was carefully observed the whole 

 time) ; we improved the occasion by making a series of current- 

 observations, and the results, which will be discussed farther 

 on, prove the drift or the swing to have been insignificant, so 

 that the observations are fairly reliable. 



In the deep ocean, where current-measurements would be 

 of special interest, it is impossible to anchor the ship on the 

 bottom, but the drift of the vessel may, when exactly known, 

 be allowed for, and measurements may be made at any depth. 

 We tried this two or three times. At Station 19, in the Medi- 

 terranean, all the nets and young-fish trawls were towed at the 

 same time. The speed of the vessel then just balanced the 

 surface current ; the motion appeared to be quite steady, and 

 some observations were made at different depths to determine 

 the deeper currents in comparison with the surface current. 

 Again, at Station 49 C, west of the Canaries, we employed the Current- 

 large bag-net (3 metres in diameter) with the wire as a drift- "o?he w^st^of 

 anchor. The net was lowered to a depth of 1000 metres and the Canaries, 

 held there for many hours ; the drift of the vessel was fairly 

 steady, and the compass showed the swing to be trifling. The 

 depth of water was about 5000 metres, and measurements were 

 made at different depths down to 1830 metres (1000 fathoms) 

 with two Ekman current-meters, the results being indicated 

 in Fig. 178. It may be interesting to see how an attempt at 

 determining the currents above so great a depth turned out. 



The cardinal points of the compass are shown by dotted 

 crosses, and arrows are used to indicate the velocity and 

 direction according to the current- meters sent to different 

 depths, a broken line for 915 metres (500 fathoms) and 1830 

 metres (1000 fathoms), and a thin line for 10 metres. Now, 

 we know nothing directly about the currents in deep water in 

 the open ocean between 500 and 1000 fathoms, but we must sup- 

 pose the movements to be comparatively insignificant when the 

 depth to the bottom is very great, say more than 2000 fathoms. 

 Supposing there were no current at these depths, the apparatus 

 would act as a log, showing the velocity and direction of the 

 drift of the vessel. Granting this to have been the case, the 



