VEGA -EXPEDITIONENS VETENSKAPLIGA A Ii BETEN. 



363 



has drawn special attention to the frequent occurence of ice 

 masses in those parts of the sea, wbich we should expect to 

 l^e most free of ice, altliougli he seems not to have appreciated 

 the real cause of the phenomenon. 



Another remarkable phenomenon, which certainly must 

 be due to the influence of the cold water-stratum below, was 

 observed on the evening of the 30'^^ August. Nordenskiöld 

 writes : 



»The temperature of the water near the surface varied 

 between + 1° and + 1°.6 C, the temperature of the air was 

 found + 1°..5 to + 1°.8 C. Notwithstanding both air and water 

 had a temperature higher than 0°, ice began to appear at the 

 surface of the sea (which was quite calm and unruffled) in 

 the shape of needles or a thin film of frozen water. Several 

 times before I had witnessed the formation of ice in the arctic 

 sea, when the temperature of the air was above zero. In this 

 case, when the temperature of the upper water-stratum was 

 also above zero, the formation of the ice clearly must depend 

 upon a radiation of heat either upwards to the air or down- 

 wards to the cool water-stratum at the bottom.» 



I think the most plausible explanation of the phenomenon 

 is : that the undermost layer of the fresh-water at the surface 

 of the sea, being cooled below its freezing point [= — 0°.76 C 

 corresponding to the spec. weight = l.oiioj, gave up ice, which 

 on account of its higher spec. volume rose to the surface of 

 the calm sea and thus made the impression upon the spectators 

 of a spontaneous formation of ice-crystals from the surface- 



Very interesting is the description of the encounter of the Vega with 

 ice in the inidst of the waters of the Lena river in tlie afternoon of the 

 28"' August. From the map (plate 25) and the seetion VII the reader will 

 get an idea of the situation. 



Tincontro di nuovo ghiaccio. — Fummo anche costretti a farlo dall' 

 apparire di alcuni pezzi di ghiaccio clie per la loro natura indicavanö che 

 non si erano staecati da molto tempo dal banco principale. Ed in fatti 

 verso le 2, il ghiaccio cominciö a spesseggiare, ed alle 4 pom. divenne tanto 

 denso, da obbligarci ad avanzare lentamente e con continuo maneggio di 

 timone.» 



^In x>'>'6senza del ghiaccio nessun sensibile cambiamento avviene nella 

 temjyeratura e colore dclle acque. — Contrariamento a quanto ci era sin qui 

 accaduto, Tapprossimarsi del ghiaccio non fu annunciato da alcun sensibile 

 cambiamento di temperatura e di scoloramento dell' acqua; la temperatura 

 deir acqua alla superficie ed a qualche metro di profonditå si mantenne al 

 (lisopra de' -j- 3' ed il colore continuo ad essere di un giallo terreo, le quali 

 cose indicavanö che non eravamo ancora usciti dall' estuario della Lena» . . . 



[Spedizione artica Svedese, G. B o ve.] 



