THE CARNEGIE PERSONNEL, EQUIPMENT, AND WORK 



65 



Depth, temperature, salinity, and current computation. 

 The data for all these subjects are converted to the final 

 form in which they are to be published, all computations 

 are carefully made and checked, and the final results 

 plotted on a rough graph which serves as a convenient 

 index of the accuracy and completeness of the work and 

 as a guide for making minor changes in the program. 

 No steps are taken toward preparing the material for 

 publication. 



Sonic depth measurements are made every three or 

 four hours or oftener when the bottom is irregular. The 

 depth found is corrected for density by means of tem- 

 perature and salinity curves for the nearest oceano- 

 graphic station. 



Owing to errors in the depth recorders used on the 

 oceanographic stations and to the often very consider- 

 able wire angle caused Ijy the drifting of the boat, the 

 depths indicated by the depth recorders often are great- 

 ly in error, even after being corrected for the wire 

 angle observed at the surface. Consequently the depths 

 for temperatures and water samples are based entirely 

 on depths indicated by the pressure thermometers. To 

 several of the Nansen bottles are attached one protected 

 and one unprotected thermometer. From the readings 

 of these thermometers, correction factors for the cor- 

 responding depth recorder readings are computed and 

 used for correcting the depths indicated by the depth re- 

 corders. 



In recording the temperatures a rather involved and 

 time-consuming method is used but this undoubtedly 

 could be simplified without seriously lessening the ac- 

 curacy of the results. 



Salinity is determined by the conductivity method 

 but for about every stsrth station a number of samples 

 are analyzed by Khudsen's method. On board ship the 

 conductivity method probably is the most convenient. It 

 is said that the results wUl not be accurate unless de- 

 terminations are made within a few hours after the sam- 

 ples are collected. One disadvantage of this method is 

 that a large quantity of standard water is required. This 

 water is expensive and takes up a considerable amount 

 of storage space. 



From the temperatures and salinities current com- 

 putations are made. Because the stations are too far 

 apart, and the lines often diagonal or parallel to the cur- 

 rent, the results may not always be satisfactory. 



In regard to current measurements, the writer 

 wishes to suggest that, whenever possible, courses 

 should be laid out so as to cross known or suspected 

 currents at right angles, and in certain localities sta- 

 tions should be made sufficiently close together to give 

 adequate information concerning the current. 



For the work in physical oceanography discussed 

 above, the time required averages, according to the es- 

 timate given in table 2, about ten hours per day. Adding 

 to this the time required for an oceanographic station, 

 the average per day becomes twelve hours. 



A subject that is not investigated now, but should be 

 included on future scientific cruises, is submarine illu- 

 mination. This subject has been studied by modern 

 methods only in coastal waters and any information ob- 

 tained concerning it, therefore would be of especial 

 value. The methods for measuring the penetration of 

 light do not appear to be in a very satisfactory condition, 

 however, and should he studied thoroughly and standard- 

 ized before being included in the routine of an extended 

 cruise. 



Chemistry. --In all the samples collected at present, 

 four chemical substances are determined, namely; oxy- 

 gen, silica, phosphate, and hydrogen ions. It is not cer- 

 tain, however, whether one man will be able to continue 

 to make all these determinations properly without some 

 assistance either with the laboratory or the clerical 

 work. The records for the chemical studies are brought 

 to the same state of completion as those for the physical 

 studies. 



A number of other chemical studies are desirable 

 on a cruise like that of the Carnegie but they require 

 more man power than is available. For example, nitrate 

 should be determined provided the technique is improved; 

 carbon dioxide and alkalinity studies should be made; and 

 the total fixed nitrogen, as well as ammonia nitrogen, 

 should be determined. Because atmospheric nitrogen in 

 sea water probably takes no part in either chemical or 

 biological reactions, it is no longer determined. Be- 

 cause of its inertness, however, nitrogen no doubt would 

 be a better index of the origin of the water of different 

 strata than any other chemical or group of chemicals 

 and therefore should be studied. Nitrogen could be de- 

 termined with the manometric Van Slyke (1) apparatus 

 since it would be practically the only gas remaining after 

 the removal of C02 and 02- It also could be determined 

 directly by other more elaborate methods. For chemis- 

 try also, then, two men would be needed if a more com- 

 plete chemical program were to be carried out. One 

 man would need to have only an elementary knowledge of 

 chemistry and no knowledge of oceanography. 



Biology. --The biological work performed on board 

 on the present cruise consists almost entirely of collect- 

 ing plankton samples which are forwarded to the labora- 

 tory at Washington and stored for possible future study. 

 At each station, samples are taken from the surface, 50, 

 and 100 meters, both by horizontal towings and with the 

 plankton pump. A vertical haul with an open net from 

 150 meters to the surface also is made. 



Although the time required for carrying out a com- 

 plete biological program on board ship would be prohibi- 

 tive, a fairly extensive program of plankton work is 

 feasible. A surprising amount of plankton, even of phyto- 

 plankton, is brought up by the townets. This material 

 should be studied both qualitatively and quantitatively. 



For carrying out the more elaborate program of 

 plankton studies it will not be necessary to have the bio- 

 logical identifications made on board, but provisions 

 should be made for collecting the material and for study- 

 ing the collections as soon as they reach the laboratory. 

 The planning of the biological work probably should be 

 left to the biologist in charge, whether on board or at the 

 laboratory on shore. The program, however, should 

 provide for ascertaining the quantity, either weight or 

 volume, of the total plankton in a vertical colunm of 

 water or in known volumes of water from various depths. 

 Plankton volumes could be measured on board by any 

 worker and only a small amount of time would be re- 

 quired. The data obtained would be useful in planning 

 the collecting work. 



In connection with a more elalwrate biological pro- 

 gram, collecting methods need to be given a good deal of 

 thought and planning. Methods that would delay the work 

 at a station much beyond the time reqmred for the Nan- 

 sen series (or about four hours) should not be considered. 

 Such delays would be caused by the Petterssen plankton 

 pump if an adequate number of samples were to be ob- 

 tained. The closing bottle -filtration method apparently 



