1871.] 



Theory of the Ocean, 



535 



on a large scale was weighted with a piece of lead of about 4 pounds, and 

 slung by its corners like a kite, so as to act as a suspended anchor or sinker, 

 and was lowered to a depth of 5 fathoms ; and as no current was observed 

 passing the float when the sinker was at this depth, it follows that both 

 float and sinker were in the same amount of current, or in the upper stratum 

 of the current ; that is, both were drifting along in a current of 0'9 of a 

 mile per hour. 



It was then lowered to 10 fathoms, when a sensible current was ob- 

 servable passing the buoy or float, which measured about 0*3 of a knot per 

 hour, or just one-third of the rate of current running past the float attached 

 to the shot at the bottom in 350 fathoms ; therefore the rate of current at 

 10 fathoms was ascertained to be only 0*6 of a knot per hour. 



The suspended sinker was then lowered to 20 fathoms, when there ap- 

 peared a much greater amount of current passing the float, and the rate was 

 found by the log-line to be about 0*5 of a mile per hour, thus showing that 

 the float of the suspended sinker was held in check by the sinker being in 

 a current about half that of the surface-current, or running at only about 

 0*4 of a mile per hour at 20 fathoms' depth. 



Again, on lowering the sinker to 30 fathoms there was immediately 

 observed an increase of the superficial current passing its float, showing, 

 therefore, a still diminishing current as the suspended sinker descended, 

 since it was thus kept more stationary. 



Then at 40, 50, 100, 200, and 300 fathoms the rate of the current passing 

 the float of the suspended sinker was about 0*8 of a mile, — that is, nearly 

 that of the surface-current when in all depths below 40 fathoms, so that an 

 outward current of 0*1 of a knot per hour would appear to exist there ; but 

 in reality this was the result of using in this instance a too bulky float, by 

 which the suspended sinker was dragged along at that rate ; still water, 

 therefore, undoubtedly existed below 40 fathoms, as confirmed by the density 

 experiments and others in those depths. 



This result was given to show the confusion and error almost sure to arise 

 from using bulky apparatus as a float, that offered too much resistance to 

 the surface-current ; and a double source of confusion and error is the sure 

 result if the observation is also carried out with any wind and sea. 



No undercurrent could therefore have existed here on the eastern ap- 

 proach to the Dardanelles as many have imagined ; for an undercurrent 

 being an opposite current to the current observed running past the fixed 

 float, the current then observed running past the float attached to the sus- 

 pended sinker or current-anchor would ha\ e measured a greater rate than 

 that passing the fixed float. Moreover, also, as the suspended sinker would 

 have been dragged along by the undercurrent in an opposite direction to 

 the surface-current, its float would have presented the singular phenomenon 

 of going to windward of the fixed one ; or, in other words, would have run 

 up against the stream instead of down with the surface-stream. This, on 

 a slight consideration of the phenomena, will be evident, and the delicacy 



