242 PHYSICAL GEOaRAPHY OF THE SEA, AND ITS METEOROLOGY. 



479. On the fii'st of April De Haven measured tlie ice, and 

 Thickness of a foiind it seven feet two inches tliick. It was formed 

 winter's ice. probablj mostlj of rain and river water, which, like 



our o^Ti littoral waters (§ 426), protect the Salter and heavier waters 

 below from the cold, for De Haven invariably found the tempera- 

 ture of the water under the ice 28°, which is the temperatm^e that 

 average sea water invariably assumes during the process of congela- 

 tion (§ 442). Moreover, the specific gravity of the surface water 

 which Eodgers measured in the Arctic Ocean was (§ 427) less than 

 that of average sea water — a fact in confirmation of this conjecture 

 as to the office of rain and river water in the polar seas. The freez- 

 ing-point of strong brine is 4° ; consequently the freezing-point of 

 water in the sea may vary according to the proportion of salts in it, 

 from 4° all the way up to just below 32°. Thus the salts of the 

 sea impart to its waters an elasticity, as it were, giving a law, — a 

 sort of sliding-scale — both for the thermal dilatation and of congela- 

 tion, which varies between that of fresh water and the saltest sea 

 water according to the degree of its saltness. 



480. Kodgers tried with his hydrometer and thermometer the 



of the Arctic Ocean must have drifted in an unbroken mass over towards Baffin's 

 Bay ; for these vessels were brought out upon a tongue of ice tlu-ust through that 

 bay down into Davis' Straits ; or that this tongue must have been separated from 

 the main mass, leaving behind that from which it had been severed. 



" By the latter supposition all the known facts of the case may be reconciled ; 

 by the former not one. 



" If we suppose this drifting field of ice to be formed upon the very verge of an open 

 sea, and to drift to the south as fast as it is formed, then the whole phenomenon be- 

 comes one of easy solution. At any rate, we are now possessed of a physical fact 

 which probably would have returned Captain Crozier and his companions to us all 

 safe and sound had they been aware of its existence ; and that fact is in this oft- 

 occurring, if not regular and annual, southward drift of ice from the Arctic Ocean 

 down through Baffin's Bay into Davis' Strait. Captain Franklin, being ignorant of 

 it, placed his vessels out of its reach on the south, where he was frozen in and died, 

 and where Captain Crozier, his successor, remained imprisoned for eighteen months 

 and then abandoned his ships : their drift in the mean time, and for obvious 

 reasons, being almost, if not quite insensible, except as influenced by the summer 

 thaw and 'winter wedgings.' Now if those vessels, with their scurvy-riddled, 

 frost-worn and disabled crews, could have been placed farther to the north, as in 

 Barrow's Strait, or in the fair way of any of those channels connecting with it from 

 the northward and westward, or with Baffin's Bay, the probabilities are that this 

 regularly occurring winter drift would have brought them down sfifely into milder 

 climates, and into the glad' waters of the Atlantic Ocean, as it did those four other 

 vessels. 



" The frequent, if not the regular annual occurrence of this drift down through 

 Baffin's Bay is a fact which will be considered by all future arctic explorers as one 

 of great importance, for it affords the means of escaping from the Arctic Ocean in 

 tlie severest winter." — Transactions of the American Geo. Society, 18G0. 



