DEPTHS OF THE OCEAN 



Relation 

 between 

 Mediter- 

 ranean and 

 Atlantic 

 waters. 



r 





procured at Gibraltar were a thorough success, and stopped the 

 twisting in the trawl-warp and bridle. The bottom was every- 

 where well adapted for trawling. 



At Station 23 we towed a small young-fish trawl at 12 15 

 metres. It touched the bottom and brought up a quantity of 

 empty pteropod shells which had been sifted out from the 

 bottom deposit. It is extraordinary to find these deposits of 

 shells belonging to plankton organisms only at certain relatively 



shallow and intermediate depths, for, when 



alive, the pteropods float over all depths. 



Our trawlings further resulted in a fine 

 collection of invertebrate animals ; at Station 

 24, for instance, we found the trawl full of 

 siliceous sponges. 



These waters offer a good field for a 

 thorough study of the distribution of animal 

 life, for the nature of the bottom and the gentle 

 slope permit of trawling at all depths. Our 

 time unfortunately was too short to permit us 

 to do more than obtain a general impression. 



We next turned our attention to the hydro- 

 graphical investigations, and steamed to the 

 north side of the bay near Cadiz (Station 26), 

 whence we ran a series of stations, at all of 

 which careful hydrographical observations were 

 made (Stations 26-30). 



At the conclusion of the " Challenger " 

 Expedition Buchan showed that it was pos- 

 sible to trace the course of the comparatively 

 warm Mediterranean water out into the North 

 Atlantic Ocean, In 1909 the Danish expedition in the " Thor" 

 under Schmidt made some observations from the Strait of 

 Gibraltar westwards, and secured extremely accurate determina- 

 tions of temperature and salinity, showing that the Mediterranean 

 water (in a very diluted state) makes its way out through the 

 Spanish Bay, sinking down to a depth of 1000-1200 metres. 



In our investigations we aimed at studying more closely the 

 relation between Atlantic water and Mediterranean water, and 

 we also endeavoured to become familiar with the currents on 

 both the Spanish and Moroccan sides of the bay. Unfortun- 

 ately we had to abandon our current measurements, but the 

 variations of salinity and temperature from our many adjoining 

 stations give a fairly good idea of the conditions. It is enough 



Fig. 50. — The 

 Swivel. 



