536 THE POPULAR SCIENCE MONTHLY. 



nean fissures or crevasses in which the waters of the Baltic and the 

 Mediterranean, incessantly swelled by the rivers and by the currents 

 of the Sund and of the Strait of Gibraltar, constantly lost themselves. 

 During the last three years, the question of the evaporation of sea- 

 water has been much discussed between the partisans of the Saharian 

 sea and their adversaries. The great point was to ascertain whether 

 the proposed sea would not in the end become an enormous marsh. 

 The sub-commission of the French Academy of Sciences was of the 

 opinion that, other things being equal, salt water would evaporate less 

 rapidly than fresh. Experiments by M. Dieulefait, on the other hand, 

 indicated that a nearly equal loss would occur in the case of salt water 

 and of fresh. 



Fresh water freezes at 32° Fahr., but a liquid charged with salt 

 congeals at lower temperatures ; the rule is about the same as for the 

 maximum of density, except that water slightly salt undergoes its 

 contraction before being converted into ice, while normal sea-water 

 acquires its minimum volume only in a state of surfusion, or when 

 maintained artificially in a fluid state in capillaiy tubes. In this con- 

 dition, a number of substances, water among them, are susceptible of 

 being cooled considerably below their point of congelation and still re- 

 maining liquid. In the Baltic and White Seas, the waters of which for 

 some depth are but weakly charged with salt, ice forms on the surface 

 when the surrounding temperature has become low enough, while im- 

 mediately below are strata more dense and relatively warmer. But 

 suppose that below a certain depth of a brackish and warm liquid there 

 is a cold salt current ; the latter would produce such a refrigeration in 

 the mixed intermediate strata that a mass of ice would be formed in 

 the interior of the sea at the expense of the less saline zone. The 

 block when formed would rise to the surface by virtue of its specific 

 levity. This is what happens at the mouths of the great Siberian riv- 

 ers. The Lena, in particular, pours out an enormous mass of warm 

 water which overwhelms the salt waves from the polar regions. Even 

 in the most favorable seasons, the navigator sails in the midst of float- 

 ing ice-cakes that constitute a constant source of danger, while the 

 thermometer dipped in the sea will indicate a temperature above the 

 freezing-point. The depth of the warm stratum varies with the year, 

 the place, and the prevailing winds ; and hence we account for some 

 explorers declaring impracticable tracks which others have easily sailed 

 over. The northeast passage along the Siberian coast can never be- 

 come a regular commercial route, unless, by repeated soundings accom- 

 panied by attentive studies, we can finally discover regular and peri- 

 odical laws for the phenomena under consideration. 



The Swedish physicist, Edlund, having inquired of the Scandina- 

 vian fishermen, was assured that they had sometimes, though rarely, 

 seen the sea near the fiords of their country "vomit fragments of ice." 

 The following is a textual reproduction of the story of one of the sail- 



