ICEBERGS IN NAVIGATION — BARNES. 



729 



sea. It was supposed that the iceberg effect was caused by the fresh 

 water observed by Pettersson in his tank experiments dikiting the 

 sea water, and creating a blanket of lighter water in which the sun's 

 heat is absorbed. In the open sea the warming of the sea by the sun 

 is offset by the vertical circulation, but in the fresher and lighter water 

 this is impossible, and the warmer water remains on the surface. 



DISTURBING INFLUENCE OF LAND ON THE TEMPERATURE OF THE SEA. 



One of the most interesting results of the Hudson Bay experiments 

 was the effect of land on the temperature of the sea. The coast 



iSmiiaa 



36tni\e.S 



S4-mi\as> 7Z.m(l«& Somilas 



Fig. 5.— Miceo-tuermogram of the iceberg effect from record made on the micro- 

 thermometer ON ('anadian northern steamship Royal George. 



of Labrador appears to exert an influence in turning up the colder 

 undercurrents of the Arctic stream. Thus, whenever the ship 

 steamed in toward the coast line the temperature was found to fall 

 1° or 2°. The limit of the influence appears to be about 5 miles. It 

 has been shown by Dr. Dawson that the shoals in the Bay of Fundy 

 influence the surface temperatures, and this is in accord with the 

 present results. Taking this into consideration, it appears that the 

 microthermometer may be of gi'oat service in telling the presence of 

 land and shoals from a ship at sea. Figure 4 shows the effect of the 

 coast line of Labrador in lowering the surface temperature of the sea. 



