550 



Captain Spratt on the Undercurrent [June 15, 



Strait shows, and not on the east or up-hill side, for an undercurrent 

 coming from the Mediterranean, even if such existed there as an under- 

 current. But I must give my reason for not considering this temperature 

 and density at Station 67 as abnormal; for the position being clearly 

 several miles on the Atlantic side of the ridge*, we should expect to find 

 proximate Atlantic conditions on that side. Now, as Dr. Carpenter has no 

 densities between Lisbon and the Straits, except at Station 67, he has no 

 true comparison with the Atlantic conditions of either the surface or the 

 deep water at that part ; for the lighter density of the surface-water of 

 the Straits is apparently due to its being a diluted or lowered condition 

 of that of the Atlantic in the same parallel from the influence of the two 

 large Spanish rivers, the Guadiana and Guadalquiver, which fall into the 

 sea so near the entrance to the Straits : not so, however, the density in the 

 depths of 188 fathoms; for there we should expect to find the normal 

 density nearly of the proximate part of the Atlantic, which, if denser than 

 the Atlantic in general, the same would be found in the deeper waters 

 drawn from it by the indraft current into the Mediterranean, the river in- 

 fluence being confined to the surface and being also drawn into the Straits. 



Then in regard to the specific gravity of 1028*1 at the bottom, which in- 

 duced Dr. Carpenter to consider it to be Mediterranean water and not At- 

 lantic, because some slightdegree heavier than the mean of the Atlantic found 

 by him between Lisbon and England, I am induced to believe, from Dr. 

 Forchhammer's researches, that such a density is about the normal con- 

 dition of the Atlantic deeps near the African coast in this parallel ; for 

 he shows that the maximum salinity of the Atlantic lies to the south-west 

 of the Straits, about the parallel of 24° and up to about 36° north latitude, 

 and some 300 miles only distant from the African coast, where he says it is 

 37*908 per 1000, and that this salinity is nowhere exceeded in the Mediter- 

 ranean, but where its abnormal maximum density between Crete and the 

 Libyan coast is found, which he shows is only exceeded in the whole ocean 

 by the density found in the Red Seaf . This great salinity off the Morocco 

 coast he attributes to the absence of rivers upon it ; therefore it seems 

 to me that as we have a source for a salinity as great as that of the mean 

 salinity of the Mediterranean so near, on the outside of the Straits, we have 

 no proof that the water of 1028*1 specific gravity, found by Dr. Carpenter 

 at the depth of 188 fathoms at Station 67, and clearly on the outside of 

 the barrier-ridge, is not Atlantic water, instead of being Mediterranean 

 water, as he concluded, and concluded from it also that there was an " up- 

 hill outflow" as a necessary result. 



This, however, is an excusable oversight or misunderstanding of the 

 conditions, as, with all due deference, it seems to me to be, in one not familiar 

 with the indications of a few scattered soundings on a chart of the probable 

 line of direction of the crest of a submerged ridge. 



* See Chart of the Cruise of H.M.S. ■ Porcupine.' 

 t See Phil. Trans. 1865, p. 220. 



