14 MARION AND GENERAL GREENE EXPEDITIONS 



AVashington, D. C, a description of the instriinients having been 

 published by Wenner, Smith, and Soule (1930). The adjustment 

 of the variables were checked at least every 4 days, and often once or 

 twice daily by means of two or more tests with water of known 

 salinity. Frequent duplicate determinations of the salinity of 

 samples was performed where there was any reason to doubt the 

 reliability of any determination; also duplicate determinations were 

 made of nearly every sample from depths greater than 1.200 meters. 

 The precision of the salinity values, therefore, shown in the 1928 

 tables is believed to be equal to 0.02%o. 



In addition to the temperature and salinity observations approxi- 

 mately oO samples of the bottom from the shelves and slopes of the 

 Labrador Basin were secured by means of a home-made sampler. 

 A report of the scientific findings regarding the bottom collections 

 has been published by Ricketts & Trask (1932). 



The Marion was equipped with a fathometer, manufactured by the 

 Submarine Signal Corporation, Boston, Mass., with which sound- 

 ings were made at half-hour intervals and sometimes oftener. A 

 description of the instrument and the methods employed in the 

 bathymetrical survey have also been reported by Ricketts & Trask 

 (1932). 



The Greene-Bigelow water bottles gave us continual trouble and 

 their unreliability necessitated unceasing vigilance to guard against 

 errors entering the observations. The Marion received these instru- 

 ments immediately on the expiration of Ice Patrol, where for the pre- 

 vious 3 months they had received hard usage. No time was available 

 to give them the much-needed attention of a machine shop. The 

 material, moreover, from which the bottles had been manufactured 

 was entirely too soft and malleable to withstand the shocks and 

 handling incident to field work. Despite continual repairs on board 

 the bottles occasionally would fail to close after releasing the mes- 

 sengers or would sometimes, during rough seas and lively motion of 

 the ship, release a messenger prematurely, thus necessitating the en- 

 tire retaking of the observations at a station. 



It was our practice, however, by pressing against the suspended 

 wire, to feel and count the messengers as each one of the series 

 tripped its respective bottle. If these did not check with the total 

 number of bottles, then those depths not so recorded were retaken. 

 In order to guard more carefully against faulty operation of the 

 water bottles it was routine procedure for those responsible for the 

 station observations to construct a temperature curve of the ther- 

 mometer readings on cross-section paper before the ship was per- 

 mitted to depart from the spot. If the temperature curve was found 

 to contain any marked irregularities, those observations considered 

 suspicious were immediately retaken and rechecked. 



No unprotected thermometers were included in the 1928 equip- 

 ment, and because of this fact particular attention at stations was 

 given to the elimination, as much as possible, of the wire angle. 

 It was found j)ossiblc to maintain a nearly vertical wire with the 

 Marion even during a gale of wind by a kick ahead, first on one 

 motor and then on the other, as she fell off either side of "'the 

 eye" of the wind. The fact that the Marion possessed twin screws 

 made this possible and reduced this source of error to a minimum. 



