INTRODUCTION. 77 



which is not frozen has taken up the salt which 

 has been precipitated by the ice. As the sea-water 

 has other ingredients besides salt mixed with it, 

 which only chemical analysis can discover, it can 

 do no harm to give some bottles of" it to a good 

 chemist. 



The very important question of the daily eva- 

 poration of the immense surface of the ocean, is 

 connected, in a manner, not yet sufficiently investi- 

 gated, with the saltness of the sea-water. The 

 investigations into this point are most easily made 

 with the areometer, by suspending in the open air, 

 a cylindrical vessel containing a portion of water, 

 the specific gravity of which is to be deter- 

 mined from time to time. The surface of the 

 water must also be known, and the temperature of 

 the water and the air be frequently examined be- 

 tween the measuring. But the same water must 

 not be used for several days together, because the 

 evaporation decreases in proportion, as the solution 

 becomes stronger, so that no inference on the 

 evaporation of the sea could be drawn from it. 



Another important point towards the general 

 climatology of our globe, is the investigation of the 

 temperature of the sea, both on the surface and be- 

 low it. A connected series of observations on the 

 temperature of the sea made at the same season of 

 the year, and at the same deptli, at the distance of 

 every 5° of latitude from the equator to the pole, 

 would procure us much sooner, and more certainly. 



