54 



measurements gave 15 additional points on the calibration curve, and 

 as the computed curve agreed well with these additional points the 

 computed curve was accepted as final. Early in the post-season 

 cruise it was necessary to return to St. Johns to hospitalize a case of 

 acute appendicitis and one of follicular tonsillitis. Advantage was 

 taken of this brief stay in port to measure, by both bridge and titra- 

 tion methods, five samples in the low-salinity range. The result was 

 a further verification of the computed calibration curve. 



As may have been inferred from the above, silver-nitrate titration 

 using Knudsen burettes and automatic pipettes was used for deter- 

 mining the salinities of the samples collected during the April oceano- 

 graphic cruise and for arriving at the calibration curve for the new 

 salinity bridge. It was further considered as a stand-by method for 

 the remainder of the season and during the post-season cruise. Each 

 sample was measured twice, and where the disagreement between the 

 two measurements was greater than 0.02 %o in clilorine, a third 

 titration was made. The titration measurements are considered ta 

 be accurate to 0.02 %o in salinity. 



The new salinity bridge was used as the routine method of deter- 

 mining the salinities of the samples collected on the May, June, and 

 post-season oceanographic cruises. Each sample was measured 

 twice, and out of a total of 2,570 such measurements no two measure- 

 ments of the same sample differed by more than 0.015 %o in salinity. 

 This precision is very much better than that obtained with the silver- 

 nitrate titration method at sea, although the accuracy may be no 

 better. Both titration and bridge measurements were referred ta 

 Copenhagen standard water, and in the case of the bridge all standard 

 water was from the same batch. Pis, so that any variations in salt 

 ratios wliich might possibly exist between different batches of stand- 

 ard water would not invalidate the calibration curve of the bridge. 

 Copenhagen standard water was used for every series of measurements 

 and either Copenhagen standard or a substandard water was used in 

 each cell once every 10 or 12 measurements. The titrations and the 

 routine bridge measurements were performed by the oceanographer's 

 assistant, Bernard S. Loebig, yeoman, first-class. 



At the 129 stations occupied during the season serial observations 

 of temperature and salinity extended to depths of between 1,000 and 

 1,500 meters where the depth of water permitted. The levels from 

 which it was attempted to obtain measurements were 0, 25, 50, 75, 

 100, 150, 200, 300, 400, 600, 800, 1,000, and 1,500 meters. The 

 measurements from the depths to 300 meters, inclusive, were usually 

 obtained on one series, a second series being used to obtain the deeper 

 measurements. An unprotected thermometer was invariably sent 

 down with the deepest bottle of a series, and in the deep series addi- 

 tional unprotected thermometers were attached to the uppermost 



