40 ECHO-SOUNDING AND HYDROGRAPHICAL STUDIES 



1951, in the deep water of the Phihppine Trench, where previously only 

 the Snellius Expedition had recorded a full station down to the bottom. 

 Our operations with the uppermost series of water bottles went smoothly 

 and successfully, but in the great depths we encountered every sort 

 of unforeseen difficulty. In the first deep series we lost four thermo- 

 meters owing to the heavy pressure of the water. One thermometer of 

 the bottle lowered down to 7,700 metres was crushed, and the force of 

 the explosion broke the other (Fig. p. 39). On the same occasion the 

 thermometers of the lowermost bottle, 8,503 metres deep, exploded with 

 a violence which tore off their metal frame. The surface of the bottle 

 showed marks of glass splinters from the thermometers. After this we 

 could not afford to put more than one thermometer on each bottle. 



Another frequent source of trouble was the inability of the messenger 

 weights to release the bottles at depths beyond 7,000 metres. The whole 

 series came up un-released on no fewer than five occasions, with the 

 loss of many valuable hours' work. Earlier on, defecti\'e release had been 

 caused by the twisting of the tentacles of jellyfish and squids round the 

 wire. They are so strong that they can only be removed with a knife. 

 We had to cut these off here also; yet still the bottles failed to function, 

 and even two weights tied together were ineffective. We eventually located 

 the source of the trouble as the grease in which the funnel of the wire is 

 spun. It was squeezed from the top by the heavy weight of wire; and 

 though the messenger slid without difficulty through the warm upper 

 levels, when it passed through the cold water at 3,000 — 4,000 metres 

 the grease which it picked up on the way became stiff and acted as a 

 brake. By constantly wiping the wire while it was being paid out we 

 were able to remo\'e enough grease to enable the weight to slide easily, 

 and the last station in the Philippine Trench was completed without 

 difficulty. Altogether, we obtained four successful series from the deepest 

 layers of the trench, down to a depth of 9,864 metres. 



The principal data from the observations in the Philippine Trench 

 have been collated in the figure on page 39. From the outline diagram 

 on the right it will be seen that the high surface temperature of about 

 29° G extends no further down than 100 metres; already at 300 metres 

 the temperature is only 10° C. The lowest temperature (i.58°C) is at 

 nearly 4,000 metres, after which there is a steady rise of nearly one degree 

 down to the bottom. The salinity at the surface is comparatively low, as 

 it is everywhere near the Equator. A small maximum is found at 150 metres, 

 and after the minimum at 400 metres there is a steady progression to the 

 absolute uniformity of the abyssal waters. The oxygen content is greatest 



