1872.] 



( Shearwater > Scientific Researches. 



639 



appears to me so readily demonstrable, that I should have thought it 

 sufficient to point out what I regard as the just interpretation of them, 

 leaving it to the scientific public to decide whether his or my view of the 

 case has the stronger claim to acceptance. 



166. But as Capt. Spratt has made his experiments on the Dardanelles 

 Current the basis of an assault*, not merely on the position I had ventured 

 to assume (on theoretical grounds only) in regard to that current, but also 

 on the Under-current doctrine which I had put forward as experimentally 

 substantiated in the case of the Gibraltar and Baltic Currents, and, by 

 implication, on the Doctrine of a General Oceanic Circulation which the 

 inquiries I have recently had a share in conducting appear to me to justify, 

 it is necessary for me to address myself to a more formal refutation of his 

 arguments. 



167. It may be thought presumptuous in one Avho can only claim to 

 possess a merely elementary knowledge of Physical Science, and a very 

 limited amount of practical acquaintance with inquiries of this nature, to 

 call in question the unhesitating dictum of a Surveying Officer of Capt, 

 Spratt's acknowledged ability and large experience, in regard to a matter 

 lying completely within his own province. For however simple the case 

 may appear, it might naturally be thought more probable that some essen- 

 tial condition had been left out of view on my part, than that Captain 

 Spratt's interpretation of his results should be precisely the reverse of 

 that which his own data necessitate. In order, therefore, to secure my- 

 self against any such error, I have submitted the case to several Naval 

 Officers who have made a special study, both theoretically and practically, 

 of all matters relating to Currents ; and finding that their judgment en* 

 tirely accords with my own, I venture to believe that the validity of my 

 claim to a complete reversal of C&pt. Spratt's conclusion will be generally 

 admitted. 



168. Dardanelles Current. — The method of experimenting adopted by 

 Capt. Spratt was so nearly the same as that followed by Capt. Nares 

 (under instructions from the Admiralty) in the experiments on the Gibraltar 

 Current, of which the detail has already been givtn, that it is only requi- 

 site to recall its two essential features. — A float or buoy was attached to a 

 sinker resting on the bottom, so as to serve as a fixed point of reference ; 

 this we shall call, as before, the anchored buoy. To another float or buoy, 

 exactly resembling the first, was suspended at any desired depth a " cur- 

 rent-drag," offering a large surface of resistance to any current in which it 

 might hang ; and the float which supports this we shall call (as before) 

 the current-buoy. 



169. Now I quite agree with Capt. Spratt, that if a surface-current 

 flows past the " anchored buoy " and the " current-buoy " at the same 

 rate, the current-drag suspended from the latter must be as motionless as 

 the sinker to which the anchored buoy is attached ; but I differ from him 



* Proceedings of the Royal Society, vol. xix. p. 528 ct scq. 



