44 THE LAST CRUISE OF THE CARNEGIE 



They are towed from the ship during oceanographic stations, 

 and may be lowered to any depth desired. 



It is true that the lack of fishing and dredging equipment de- 

 prived us of the excitement of bringing up fantastically shaped 

 monsters from the deep. But in the plankton-nets we can catch 

 a hundred bizarre forms to every one recovered from a dredge; 

 we can find animals painted with all the colors of the rainbow, 

 whereas the deep-sea organisms are either black or red. Anyone 

 who has once seen these exquisite creatures through a microscope 

 will never again envy the man with a deep-sea dredge. 



A double boat-boom projects over the water from the fore 

 rigging — a glorified pirates' plank, as someone has suggested. 

 This boom-walk was similar to that used on Beebe's expedition. 

 On calm days it may be lowered for the use of the biologist, who 

 is thus able to dip up floating objects beyond the wash of the vessel. 



A step over the high doorsill and we are in the chemical labora- 

 tory. Here each water-sample is analyzed for salinity, phosphates, 

 silicates, oxygen, and hydrogen ions. All these substances are 

 intimately related to the life of plankton. We limited ourselves 

 to such determinations as could be made on board, for we had no 

 room to stow away samples for study ashore. 



There were several unusual features about our chemical work. 

 The salt-content of the sea-water was measured electrically by a 

 resistance-bridge designed for our use by Dr. Wenner of the Bureau 

 of Standards in Washington. By measuring the electrical re- 

 sistance of a sample of sea- water, we are able to calculate its 

 salinity. This method was regularly checked by the conventional 

 titration of samples with silver-nitrate solutions. 



The apparatus for measuring the so-called "hydrogen-ion con- 

 centration" of sea-water at various depths was ingenious. It 

 avoided the use of permanent color standards in test-tubes, and 

 gave more accurate readings than are ordinarily obtained at sea. 

 It was a modification of the double-wedge comparator described 

 in technical journals by Barnett and Barnett. 



To analyze for phosphates and silicates, chemicals are added 

 to the specimen to bring about the development of a certain color, 

 the intensity of which is a measure of the phosphate or silicate 



