526 Professor Howard T. Barnes [May 31, 



it may be stated that floating ice may be met with anywhere in the 

 North Atlantic Ocean, northwards of the 40th degree of latitude, at 

 any season of the year. 



Surface Tempeeature of the Labrador Current 

 IN Winter and Summer. 



During tlie winter months the surface temperature of the Labrador 

 current often falls to the freezing point of salt water, about 28° F., 

 but it is more often at 29° or 30° F. As the spring advances the line 

 of low temperature advances farther north, until in July or August the 

 temperature on the Grand Banks towards the Straits of Belle Isle 

 reaches 40° or 45° F., and gradually falls northwards to 29° F. in 

 Hudson Straits. The surface temperature varies considerably, de- 

 pending on the proximity of ice or land, as will be explained shortly. 

 No measurements have iDeen made north of the Banks in winter or 

 spring, when the Straits of Belle Isle are ice-bound. Reports of the 

 temperature of the ice track are frequently given by sea captains. 

 Results as low as 22° F. have been shown to me, but I believe these 

 to be impossible, and due to some error of measurement arising from 

 the crude method now in vogue on our Atlantic liners. 



Influence of Icebergs on the Temperature of the Sea. 



There can be no question but that icebergs have an important 

 influence on the temperature of the sea. Composed of frozen fresh 

 water from the north, they melt rapidly when they drift down to 

 the warmer waters of the Banks and when they reach the Gulf 

 Stream. On account of the small conductivity of the water, no 

 appreciable cooling can result from this cause. If it were not for 

 the currents in the sea and the circulation set up by the melting 

 berg, no cooling effect would be appreciable. That there is a small 

 cooling effect has been shown by captains and others, but this has 

 not been made use of for telling the proximity of ice with any success. 

 What is called salt-water ice — that is, ice formed by the freezing of 

 salt water — contains a small trace of salt in its composition and 

 frequently holds salt mechanically, but there is very little difference in 

 the purity of the ice. It is well known that water in freezing expels 

 all the impurities, hence it is erroneous to say that salt-water ice 

 floats under the surface. What is called salt-water ice is really 

 the same as field-ice, and is exceedingly hard to break. Its structure 

 is not uniform, and, composed often of irregular broken pieces, it has 

 no line of cleavage. 



Pettersson's Theory of Ice Melting. 



Dr. Otto Pettersson has for some time shown experimentally that 

 ice melting in salt water produces three currents (Fig. 1). (1) When 



