1871.] 



Theory of the Ocean. 



541 



134 the surface-current was running from the north at Elsinore," that is, 

 into the Baltic from the Kattegat and German Ocean, and of course then 

 doing what I have shown to occur in the Sea of Marmora and Black Sea, 

 with every recurring and return- current into them, viz. restoring the lost 

 saline density of the surface and deeps of those seas. Now the proportion 

 of the inward return surface-current from the denser seas is very much 

 greater in the Baltic Straits than in the Black Sea Straits, and, moreover, 

 the depth on the dividing ridges of the Sound and Great Belt leading into 

 the Baltic does not exceed 9 fathoms, or about 50 feet only ; and thus, 

 even here (notwithstanding the great supply of fresh water from the Baltic 

 rivers into the Baltic between April and September, when the observations 

 were made, and, therefore, the time of greatest supply in the whole year), 

 the outside influences of wind &c. so outbalanced the surface-level be- 

 tween the Baltic and German Ocean, as to produce twenty -four days inward 

 current in that period, and twenty-four days without any current, then 

 stopping the Baltic outflow in fact. So that Dr. Forchhammer himself 

 shows that the phenomena of the currents to and from the Baltic are, 

 at one time, a mass of diluted water outwards over the very shallow 

 barrier forming the straits, and then a run of the Kattegat denser water 

 inwards for the restoration of the normal saltness. What need, then, 

 was there for looking to an undercurrent as the great source of such 

 a resupply, when it was evidently produced by a greater agency during 

 the twenty-four days return surface-current inwards, when the German 

 Ocean must have stood at a higher level than the Baltic? One more remark 

 is necessary to show another fallacious conclusion of Dr. Forchhammer in 

 favour of the undercurrent theory. In p. 233 he says, " I observed on 

 the 2nd of March, 1850, the temperature of the undercurrent at a depth 

 of 108 feet to be 36 0, 8 Fahr., while the temperature of the surface was 

 34°*9 Fahr.," — thus intimating that because he found a higher tempera- 

 ture and density in 108 feet at Elsinore it positively indicated an under- 

 current from the German Ocean or Kattegat, the conditions of density and 

 temperature being those of the outside sea and not of the Baltic. But these 

 were the natural conditions of things there, because in the depth of 108 feet 

 at Elsinore he was in a depth more than twice that of the submarine shallow 

 barrier that separates the Baltic from the Kattegat, and on the Kattegat 

 side of the ridge. The barrier or ridge is at the southern end of both the 

 Great Belt and Sound, and is thirty miles to the south of Elsinore, which 

 is therefore on the German Ocean side of the ridge ; and, moreover, the 

 depth of 108 feet at Elsinore was in the greatest depth of the Kattegat any- 

 where within fifty or sixty miles northward, and the barrier ridge is only 

 30 feet deep here. The undercurrent view, then, has no ground of sup- 

 port from this fact ; but the contrary, for the increase of temperature and 

 density was found exactly where it was natural to expect it, that is, in the 

 region of depths below the comparatively shallow barrier of about 50 feet 

 in depth which separates the Baltic from the Kattegat ; and especially so as 



