SCIEXTIFIC RESULTS 125 



measurements of the temperature may be made to give warnino; of 

 the proximity of berths. An electrical resistance thermometer frrad- 

 iiated to one-thousandtli of a degree centigrade called a microthermo- 

 gram Avas experimented with on a trip to Hudson Bay in July, 1910o 

 Barnes (1910. p. 131) shows that a typical thermograph upon ap- 

 proaching a berg begins with a slight rise and then drops from 4.6° C. 

 at 1 mile, to 2.2° C. at onedialf mile. The primary peak and then the 

 fall in temperature Avere explained as due to Pettersson's No. (1) 

 current, i. e., to the thaw water spreading out on the surface, the outer 

 fringe l)eing heated most by the sun. was warmest. But Barnes's 

 (1913) further investigations from the Canadian Pacific steamship 

 Mont calm near the Strait of Belle Isle the summer of 1912 found, 

 contrary to his earlier experiments, a continuous rise of temperature 

 as bergs were approached suggesting the drop in the thermographs 

 noted in 1910 Avas actually due to the generally Ioav temperature of 

 the cold Labrador current in Avhich the bergs floated. Barnes con- 

 chules therefore that Pettersson's current Xo. (1) does not prevail 

 under actual conditions at sea, but instead that there is an infloAving 

 surface current toAvard a berg. Aitken (1913. p. 501) carried out a 

 laboratory experiment similar to Pettersson's, finding that fresh 

 ice melting in salt Avater induces a circulation Avhereby all of the thaAV 

 comes to the surface. Taylor (1914. p. 05). employing a microther- 

 mogram similar to Barnes's, failed to secure any definite reliable tem- 

 perature graphs Avhen the Scotia approached close to icebergs on the 

 Grand Banks in the spring of 1913. Sometimes there Avas a rise, 

 sometimes a drop, and usually the record Avas masked by fluctuations 

 in the temperature due to causes other than icebergs. Thuras (1915. 

 p. 67) approached bergs on the ice ])atr<)l ship using a thermometer 

 graduated to one-tenth of a degree centigrade, finding that no definite 

 rise and fall of the instrument Avas re])eated Avith regularity. Cruis- 

 ing past some bergs the instrument Avould remain quite steady, Avhile 

 at others it Avould be A^ery erratic. Aitken (1915, p. 561) criticizes 

 Barnes's Avork in vieAv of the contradictory results obtained by him- 

 self and by Taylor. 



Barnes (1927, p. 92), in a recent article descrilies the circulation in- 

 duced by melting icebergs as folloAvs : 



Every iceberg is a hydraulic pump sinking the surrouiuliiig sea water liy cool- 

 ing and drawing to itself the warm surface waters and thereby contributes to 

 its own destruction. The warmed surface layers flow more rapidly to the cold 

 ice surface than do the cool layers, hence the iceberg becomes the central point 

 for the collection of the warmer surface water. 



By his vieAv the Avarmed surrounding Avater is an indraft from the 

 surface layers Avhich compensates for the sinking thaw water. This 

 horizontal movement keeps them uppermost and explains their 

 greater insolation and Avarmth near a melting iceberg. 



Ricketts (1930, p. 119) discusses the conventional theory of circula- 

 tion around icebergs and he finds it difficult in vieAv of the stratifica- 

 tion and marked stability of the surface layers to belieA'e that melting 

 icebergs establish currents of any appreciable magnitude. He as- 

 sumes, however, for the sake of argument, that an aA-erage-sizecl 

 berg south of NeAvfoundland chills a 10-foot layer of the surrounding 

 Avater to a temperature of 20° F. He then shoAvs that under the given 

 conditions the resulting horizontal indraft Avill be 27 feet per day 



