THE SALTS OF THE SEA, 235 



conjecture, the thickest part of the " middle ice " should be that 

 which has been exposed to the longest and severest cold, and 

 this is probably that which began to be formed on the edge oi 

 the open sea in January. As it drifted to the south it continued 

 to form and grow thick, and perhaps would be the last to melt : 

 while that which began to be formed at the edge of the open sea 

 in March or April would drift out, and not attain much thick- 

 ness before it would cease to freeze and commence to thaw. It 

 is this spring-made " middle ice " then, which, as it drifts to the 

 south, would, being thin, be the first to break up ; and experience 

 has taught the whalemen to look north, not south, for the first 

 breaking up and the earliest passage through the "middle ice." 



460. Position of tlie o;pen sea. — The open sea, therefore, is, it 

 may be inferred, at no groat distance from the several straits, 

 which, leading in a northwardly direction, connect Baffin's Bay 

 with the Arctic Ocean. It is through these straits that the 

 winter drift takes place. The ice in which the Fox, the Eesolute, 

 the Advance, and the Rescue each drifted a thousand miles or more, 

 came down through these straits. The fact of this annual winter 

 drift from the Arctic Ocean is a most important one for future 

 explorers. Had Captain Franklin known of it, he might have 

 put his vessels in the line of it, and so escaped the rigours of 

 that second winter. It would have brought him safely to the 

 parallel of 65° or 60", and set him free, as it did four other 

 vessels, in the glad waters of the Atlantic Ocean. 



CHAPTER X. 



§ 461-499. THE SALTS OF THE SEA. 



461. The trine of the ocean. — The brine of the ocean is the ley 

 of the earth (§ 43). From it the sea derives dynamical power, 

 and its currents their main strength. Hence, to understand the 

 dynamics of the ocean, it is necessary to study the effects of 

 their saltness upon the equilibrium of its waters ; wherefore this 

 chapter is added to assist in the elucidation of what has already 

 been said concerning the currents and other phenomena of the 

 sea. Why was the sea made salt ? It is the salts of the sea that 

 ill part to its waters those curious anomalies in the laws of 

 freezing and of thermal dilatation which have been described in a 



