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 of 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 thickness 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 the open 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 Resolute, 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 brine 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
