1844.] 



On the Specific Gravity of Sea Water. 



767 



hydrometer prevented the continuance of my experiments to, at least, 

 our farthest Southing. 



The hydrometer used by me was of great delicacy, and was made for 

 the express purpose under my directions : hundredths, the zero point 

 being of distilled water, 1000 could be ascertained with ease when the 

 ship was very steady, but as this was not frequently the case, I was con- 

 tent to record in my ordinary experiments, only tenths. As the tempera- 

 ture of the sea rose much higher than I had anticipated, the range of 

 my instrument was insufficient, although I managed to extend it. Any 

 person desirous of pursuing similar investigations on the same field, 

 should be provided with a hydrometer ranging from 1022.5 to 1028.0. 



Before 1 had completed my experiments for ascertaining the law of 

 decrease of specific gravity with increase of temperature, my hydrome- 

 ter became unfortunately useless, so that I have not entire confidence in 

 my results. My doubts in that regard would have been less, did not 

 the law inferable from my experiments differ so greatly from that to 

 which the varying gravity of distilled water under change of tempera- 

 ture seems subject. As I am not aware that the law alluded to has been 

 previously observed, I deem it worthy of statement and explanation here, 

 as well for its own intrinsic interest as for the connection it may be 

 found to bear with the development of heat and electricity, relations 

 which I have not the opportunity and facilities at present to consider. 

 For this purpose I shall quote from the tables of specific gravity given 

 by Berzelius, Lehrbuch der Chemie, 1843, p. 382, (the two left hand 

 columns are those quoted.) 



Temperature Cen- 

 tigrade. 



Greatest density 1 . 



Differences, 

 First order. 



Differences, 

 Second order. 



16 



09992260 







17 



0.9989752 



0.0001508 





18 



0.9988125 



0.0001627 



0.0000119 



19 



0.9986387 



0.0001738 



0.0000111 



20 



0.9984534 



6.0001853 



0.0000115 



21 



0.9982570 



0.0001964 



0.0000111 



22 



0.9980489 



0.0002081 



0.0000117 



23 



0.9978300 



0.0002189 



0.0000108 



24 



0.9976000 



0.0002300 



0.0000111 



25 



0.9973587 



0.0002413 



0.0000113 



26 



0.9971070 



0.0002517 



0.0000104 



27 



0.9968439 



0.0002631 



0.0000104 



28 



j 0.9965704 



0.0002735 



0.0000104 



29 



! 962864 



j 0.0002840 



0.0000105 



30 



| 0.9959917 



0.0002947 



0.0000107 



