2 XJ. S. COAST AND GEODETIC SURVEY 



with the possible exception of the apparatus of Monsieur and Madame 

 Chauchard, available conductivity apparatus is too expensive for the 

 purposes of this bureau, principally because more precise than the 

 requirements demand. 



The method of obtaining salinity by the method of balancing 

 columns of liquids is given brief mention in the pages that follow. 

 Finally, two standard laboratory methods, the pycnometer method 

 and the sinker method, respectively, are discussed briefly. 



Fig. 1. — Hydrometer set 

 HYDROMETER METHOD 



Hydrometer sets are furnished to ships of this bureau, as illustrated 

 in Figure 1. The three hydrometers cover the specific-gravity range 

 from that of fresh water to the greatest specific gravity likely to be 

 encountered in ocean waters. Calibration data are furnished for the 

 three hydrometers. The set includes also a 0° to 50° C. thermometer 

 and a hydrometer jar. The following procedure is suggested for the 

 use of the hydrometer: 



Pour the sea water to be tested into the hydrometer jar to such 

 depth that, when the hydrometer is put in, the water will not over- 



