122 DISCOVERY REPORTS 



possibly 20 or even more, in other words long enough for them to undergo a latitudinal displacement 

 the extent of which would depend on the speed with which the warm deep water was moving, wherever 

 that is it should happen to be travelling towards the south. Although little is known, experiments with 

 drift frames,^ undertaken by Dr G. E. R. Deacon off South Georgia in October and December 1936, 

 indicate that there it may be moving in a south-easterly direction at the rate of about 3 miles a day. The 

 drift frames, or drogues, employed, each consisting of two 6-ft. square brass frames covered with 

 cotton drill and arranged in two planes fixed to intersect each other at right angles, were suspended 

 from light floating pellets 20 in. in diameter on ordinary Kelvin sounding wire, the distance and 

 direction in which they travelled being recorded in relation to an anchored buoy. The results obtained 

 at four diff'erent levels in the warm deep layer are shown in Table 23. 



Table 23. Rate and direction of travel of drogues in the warm deep current near South Georgia 



Depth Miles Bearing from 



(m.) per day anchored buoy 



250 3-8 143F 



500 2-S 145F 



750 2-6 137° 



1000 3"o 144° 



These figures no doubt must be accepted with some reserve since they may have only a local 

 significance. Nevertheless, we might reasonably I think regard them as providing at least some 

 indication of the possible order of the speeds that might be expected in the other parts of the Antarctic 

 such as, for example, the Weddell and East Wind zones, where the deep intermediate current is known 

 to be carrying the climbing stages. It is possible indeed, in so far at least as the South Georgia area 

 is concerned, that the speeds recorded there were too low, for in the final reckoning no allowance was 

 made for the frictional drag on the suspending wires, nor was any made for the considerable counter 

 drag that must have been exerted by the Antarctic surface layer which at one point was found to be 

 travelling in exactly the opposite direction to that of the deep current at a rate of 7-3 miles a day. 



Over a century ago Maury (1855) called attention to the sometimes quite remarkable speeds that 

 subsurface currents may attain. In the following passage he refers to the work of Lieutenants J. C. 

 Walsh and S. P. Lee of the United States Navy. 



They made some interesting experiments upon the subject. A block of wood was loaded to sinking, and, by means 

 of a fishing-line or a bit of twine, let down to the depth of one hundred or five hundred fathoms (six hundred or three 

 thousand feet). A small float, just sufficient to keep the block from sinking farther, was then tied to the line, and 

 the whole let go from the boat. 



To use their own expressions, ' It was wonderful, indeed, to see this barrega move off, against wind, and sea, and 

 surface current, at the rate of over one knot an hour, as was generally the case, and on one occasion as much as 

 if knots [i.e. 42 nautical miles per day]. The men in the boat could not repress exclamations of surprise, for it really 

 appeared as if some monster of the deep had hold of the weight below, and was walking off with it'. Both officers 

 and men were amazed at the sight. 



Although with the above exceptions there are no direct measurements to prove it, it is generally 

 thought that the southward movement of the warm deep water is exceedingly slow, being probably of 

 the order of little more than a mile a day. Such a slow rate of transport, if true, clearly could not bring 

 about any major southerly displacement of the larvae unless their ascent from deep water is a very 

 much more protracted phenomenon than even at its longest I have supposed it to be. It would mean 

 at the most that they would travel no more than 20 or 30 miles to the southward of their deep point 



* Deacon gives a full account of this work in the 22nd Scientific Report to the Discovery Committee on the work of 

 'Discovery II'. 



