variability has been confirmed by observations from the 

 TRIESTE. 



Although particles are conspicuous in the "Tyndall 

 beam" of the external lamps, there has been little evidence 

 to suggest that they are alive. It is highly probable, of 

 course, that the particles are of microscopic size and 

 beyond the resolution of the human eye. Despite the con- 

 spicuousness of these particles during deep water observa- 

 tions, the water was still relatively clear compared with 

 surface coastal water. 



Kalle^'^^and others have noted that in sea water water- 

 soluble pigments of yellow color are present. This yellow 

 substance has been found in the ocean as well as in coastal 

 waters. However, it has not been observed on bathyscaph 

 dives. 



Deep water has nearly the clarity of clear oceanic 

 surface water. On one occasion, the author and another 

 observer were able to see the sea floor at 5678 meters 

 clearly as it was illuminated by the outside lights at a 

 maximum range of 60 feet. The observations were made 

 both approaching the off-white bottom and later as the 

 ascent commenced. 



By contrast, in the highly productive waters off the 

 San Diego coast visibility may be reduced to less than 2 5 

 feet. However, three TRIESTE dives made in virtually 

 the same location off San Diego on different dates revealed 

 that there can be significant difference in the quantity of 

 suspended matter present on different days. These varia- 

 tions are obviously due to the horizontal transport of 

 material and organisms into the area by deep water currents. 

 On one occasion, the water was a puree of suspended par- 

 ticles and living forms, primarily chaetognaths, cteno- 

 phores, medusae and mysids. As the majority of these 

 animals are clear and relatively transparent, they did not 

 reduce the maximum range of visibility as much as might 

 be expected. 



Observations made during several dives of the bathy- 

 scaph FNRS-III revealed the presence of a crystalline 

 clear layer near the sea floor. In no instance has this 

 observation been duplicated by the TRIESTE dives either 

 in the Mediterranean or in the Pacific. 



Water clarity near the sea floor in deep water is 



42 



