462 HARSHBERGER— INFLUENXE OF SEA WATER [April 22, 



hydrometers, one was obtained which fulfiUed all the conditions of 

 experimentation most perfectly. The hydrometer purchased of 

 Arthur H. Thomas Company is one designed to test the specific 

 gravity of liquids heavier than water. The scale reads from 0.995 

 to 1.065 ^"d is divided into single units and half units (Fig. i). 

 For example, beginning at i.oooo, the divisions of the scale read 

 as follows: 1.0005, i.ooio, 1.0015, 1.0020, 1.0025, 1-0030, 1.0035, 

 1.0040, 1.0045, T.0050. The last figure is the next prominent figure 

 on the scale printed in black letters. Altogether 140 separate read- 

 ings can be made from this scale, and if the observer wished to test 

 the salinity of the water of Salt Lake, Utah, the length of the scale 

 would have to be increased to the point indicated in Fig. i, and the 

 size of the bulbs would have to be increased correspondingly. There 

 are three bulbs blown in the hydrometer tube. The lower one is 

 the sinker with metallic mercury. The middle one carries the mer- 

 cury of the thermometer, which is inclosed in the third and upper 

 bulb. The thermometer scales reads from — 5° C. to +45° C, and 

 is divided into degrees with the fifteenth marked in red. With this 

 instrument temperature and specific gravity can be determined 

 simultaneously. 



Corrcciions to Readings. — In actual use, the experimenter finds 

 that the hydrometric readings vary with the temperature of the 

 water, and that to make the results harmonious all of the readings 

 for specific gravity must be reduced to the uniform temperature of 

 15° C. No table exists by which the reduction can be made directly 

 without calculation. Such a table for all temperature degrees and 

 degrees of specific gravity is a desideratum. A mechanic rule, or 

 sliding scale, might be constructed from which corrected readings 

 might be taken directly by adjusting the movable parts of the scale 

 to corresponding degrees of specific gravity and of temperature. In 

 the absence of such a table and mechanic scale after a prolonged 

 search through theoretic text-books of chemistry, the following one 

 was discovered, which enabled me to standardize all of the readings 

 made by the hydrometer by reference to the specific gravity at 



15° C. ' ' 



