68 



DEPTHS OF THE OCEAN 



Pelagic inves- 

 tigations in 

 the Mediter- 

 ranean. 



Water strata 

 in the Medi- 

 terranean. 



Noctihuc 



of great assistance towards a proper understanding of the 

 water circulation in the Strait of Gibraltar. 



At Station 19, a few hours' steaming from the entrance to 

 the Mediterranean, we experimented with different appliances, 

 to ascertain the best way of arranging our subsequent pelagic 

 investigations. The big silk tow-net, 3 metres in diameter, 

 was lowered to a depth of 900 metres and immediately hauled 

 up again. It was found to work well, and captured a number of 

 pelagic fish (eight specimens of Argyi^ope/ectis, a. few scopelids, 

 and some young fish), but our catch seemed to indicate that 

 vertical hauls were not nearly so productive as horizontal hauls, 

 and we therefore decided to make long horizontal hauls our 

 principal mode of catching pelagic fish during the remainder of 

 the cruise. 



At this part of the Mediterranean there was a sharply 

 defined limit between an upper water-layer, where the temper- 

 ature was fairly high and the salinity almost identical with that 

 of the upper layer in the Spanish Bay in the Atlantic, and a lower 

 water-layer with " bottom-water" of uniform temperature (a little 

 below 13° C.) and salinity (over ;^S per thousand). Several 

 series of temperatures and water-samples were taken, and the 

 limit between the two layers was found at a depth of 150-200 

 metres, though subject to considerable variation, as in the Strait 

 of Gibraltar but not to such an extent. 



The surface water here was so full of phosphorescent 

 Noctiluca as to be almost as thick as broth, and when the 

 contents of the tow-net were emptied into a glass they formed a 

 sediment a centimetre in thickness at the bottom of the glass. 

 In the evening the sea resembled a star-spangled sky, and the 

 wires following the vessel looked like gleaming stripes. During 

 the day we now saw for the first time the beautiful surface 

 organisms of the south, such as Velella and the Portuguese 

 man-of-war [P/iysalia), with which zoologists and sailors in 

 Mediterranean waters are so well acquainted. 



From the 

 Spanish Bay 

 southwards 

 along the 

 north- west 

 coast of 

 Africa. 



The region from Spain along the coast of North Africa is 

 well known to zoologists from the successful labours of the 

 French " Travailleur " and " Talisman " Expeditions. Series of 

 trawlings at various depths were undertaken by these two ships 

 with only small beam trawls, so that we had every hope of 

 accomplishing something with our large trawl. We were able 

 besides to turn to good account the information acquired from 

 the fishermen, large numbers of whom have shot their trawls 



