222 PHYSICAL GEOGRAPHY OF THE SEA : 



stating it. The question in itself is one of much difficulty, 

 and we can see no evidence that it is ever likely to go beyond 

 presumption. The uniformity in the quantity, quality, and 

 proportion of the saline constituents, and the fossil animal 

 remains of ancient Salt seas, now found many thousand feet 

 above the ocean surface, would seem the strongest proofs of 

 identity of state from the beginning. The presence in all 

 sea- water, though in most minute proportion, of those sin- 

 gular elements (or what are provisionally called such) Iodine 

 and Bromine, becomes a special part of this argument, and 

 cannot be neglected. We do not venture to cite to the same 

 effect the recent discovery of Silver, as another ingredient ; 

 since further experiments are needed to attest its univer- 

 sality * ; and perhaps we must yet postpone that still later 

 discovery (1861) of Lithium in sea-water, by the new and 

 marvellous method of the spectrum analysis. But all these 

 researches show in their results the complex and wonderful 

 nature of that ocean-fluid, which wraps round so large a part 

 of the solid globe. 



In treating of the various ocean temperature, and its in- 

 fluence in producing currents, we do not observe any notice 

 of that singular and important discovery which we owe to Sir 

 James Ross ; viz., the existence of a stratum of invariable tem- 

 perature (39^ Fahrenheit), pervading the ocean from north to 

 south, and represented on each side the equator by a similar 



* The discovery of silver in sea-water by Malaguti and Durocher, is curiously 

 confirmed by certain experiments of Mr. Field, showing the presence of silver, 

 even to the amount of seven ounces to the ton, in the copper sheathing of ships 

 after long- con tinned voyages. These observations are related in a paper read to 

 the Royal Society some months ago. 



"We may notice here the curious experiments of Professor Chapman of Toronto, 

 as to the comparative rate of evaporation from salt and fresh water. They 

 show that the greater the proportion of salt, the slower the evaporation ; and 

 that water containing the same percentage as that of the sea, loses in 24 hours 

 not quite half as much as fresh water. This fact gives some support to Mr. 

 Chapman's theory, that one great use of the salt in the Ocean is that of re- 

 gulating and controlling the evaporation ever going on over its vast surface. 



