done on board H.M.S. 'Challenger. 3 



597 



Temp. 

 °0. 



Volume. 



Temp. 



°0. 



Volume. 



Temp. 



°C. 



Volume. 



Temp. 



°0. 



Volume. 



-1 



0-99792 



+7 



0-99853 



+15 



0-99987 



+23 



1-00194 







795 



8 



866 



16 



1-00010 



24 



224 



+1 



799 



9 



878 



17 



034 



25 



256 



2 



804 



10 



893 



18 



059 



26 



288 



3 



812 



11 



910 



19 



086 



27 



320 



4 



820 



12 



927 



20 



111 



28 



352 



5 



830 



13 



947 



21 



137 



29 



385 



6 



840 



14 1 



967 



22 



164 



30 



420 



By means o£ the results given in this Table a chart of isothermals 

 was constructed, giving by inspection, as soon as the specific gravity 

 at any one temperature is known, its reduced values at any other. In 

 this way the specific gravity of every water has been reduced to its 

 value at 15°-56 O. and at the temperature which it possessed when in its 

 place in the sea. 



The results obtained since leaving Teneriffe on 15th February, 1873, 

 are given in a series of Tables, in which those relating to surface-water 

 are collected together and grouped in sections, as Teneriffe to St. 

 Thomas's, St. Thomas's via Halifax to Bermuda, and so on. Those 

 relating to bottom-water are collected in larger groups — the first contain- 

 ing all those observed in the Atlantic, the second those in the Southern, 

 the third those on the western side of the Pacific Ocean, and the 

 fourth those observed between Japan and Valparaiso. Where series of 

 observations on waters from intermediate depths have been obtained, 

 each series is given by itself. By far the greater number of the obser- 

 vations relate to surface-water, the specific gravity of which was, as a 

 rule, taken once a day when at sea, the temperature of the water being 

 at the same time observed with the standard thermometer above men- 

 tioned. 



With a single exception, off the coast of Brazil, the densest water 

 which we have met with in the ocean was found on the section from 

 Teneriffe to St. Thomas's in the heart of the north-east trade-wind 

 territory, where, from the strength and dryness of the wind, the amount 

 of evaporation must be very large. Bound about the Canary Islands 

 the mean specific gravity was found to be 1*02730 ; to the westward it 

 rises steadily until in longitude 28° W. it has reached 1*02762. Between 

 longitude 28° W. and 54° W. the mean specific gravity is 1*02773, the 

 maximum being 1*02781. On approaching the West Indies it rapidly 

 falls off to an average of 1*02719 in the neighbourhood of St. Thomas's ; 

 and if we take into account all the observations made on the western 

 side of the Atlantic, from St. Thomas's northward to the edge of the cold 



