1872.] 



' Shearwater 9 Scientific Researches. 



643 



pleteness adequate (it might have been thought) to satisfy even his re- 

 quirements. For it was stated two hundred years ago by Dr. Smith (who 

 first advanced the hypothesis of the Gibraltar Under-current), on the au- 

 thority of an intelligent Seaman who took part in the experiment, that a 

 boat having been taken into the mid-stream of the Sound, where it was 

 carried along violently by the outward current, a bucket was sunk with a 

 heavy cannon-ball to a certain depth cf water, which gave a check to the 

 boat's motion ; and that on sinking the bucket still lower, the boat was 

 carried to windward against the upper current. The surface-current 

 seemed to be not more than four or five fathoms deep ; and the under- 

 current was found to increase in strength, the lower the bucket was let fall*. 

 — Again, it was stated by Prof. Forchhammerf that a steamer having been 

 sunk, some years since, by a collision near Elsinore, a diver who went down 

 to save the passengers' goods, found a strong Under-current running towards 

 the Baltic. — Now since demonstrative evidence of the opposite movements 

 of the upper and under strata, to which no exception has been taken by 

 Captain Spratt, is here also in complete accordance with the inferences 

 drawn from the contrast between their Specific Gravities, I must own 

 myself unable to see by what right he excludes the case of the Baltic from 

 the general Physical Theory which I have brought to bear upon it Z> 



1/6. But further, since the date of Capt. Spratt's communication, an 

 important series of Researches on the Physics of the Baltic § has . been 

 published by Dr. H. A. Meyer, who has been led, by his independent and 

 long-continued inquiries, to feel assured of the existence of an inward 

 under-current through the Baltic Sound, and who has been good enough 

 further to inform me by letter that he has obtained additional evidence to 

 the same effect of a still more satisfactory character. He quotes, also, the 

 following observations made by Capt. Patton, R.N., in 1821 : — The ship 

 which he commanded having had occasion to anchor some miles from 

 Elsinore, he found a surface-current running from the Baltic at the rate of 

 four miles an hour by the log. Upon dropping the lead, in order to ascer- 

 tain the depth of water, which was about fourteen fathoms, he found the 

 line continue perpendicular from his hand, while the lead itself was 

 raised a little from the ground. Hence he concluded that an under- 

 current equally rapid with that of the surface had prevented the lead 



* Philosophical Transactions, vol. xix. p. 364. 

 t Ibid,, 1865, p. 230. 



X Here, again, as in the case of the Black-Sea currents, Capt. Spratt considers it a 

 sufficient disproof of the "Under-current Theory" to cite the fact mentioned by Prof. 

 Forchhammer, that for 24 days out of 134 the mr/ace-current runs inwards past Elsi- 

 nore. This only shows that the level of the Baltic was then reduced, S3 that heavier 

 water flowed back into it from the German Ocean ; and does not in any way disprove 

 the existence of an z'^ward under-current when the surface-current is running onwards. 



§ Untersuchungen iiber physikalische Verhiiltnisse dea westlichen Theilea c!er 

 Ost-See. Em Beitrag zur Physik des Meeres, von Dr. II. A. Mejer, Kiel. 



