ICEBERGS IN NA\'T:GATI0N BARNES. 723 



a canvas bucket over the side and bring up a sample of sea water, 

 the quartermaster then inserts a good household thermometer in the 

 water, waits for a few minutes, and then reports the reading to 

 the bridge. The thermometer is usually graduated in 2° intervals, 

 representing a length of stem about one-eighth of an inch. The 

 interval of time between the dipping of the water and the report of 

 the reading may be anything from 5 to 10 minutes. In the mean- 

 time the ship has sailed some miles beyond the point of observation. 

 It is not surprising, in the light of my results, that no value whatever 

 can be attached to measurements of this kind. As an example I can 

 quote from a standard work on navigation, Capt. Lecky's Wrinkles 

 in Practical Navigation, fifteenth edition: 



Allied to fog is the question of danger from ice. It is a popular delusion among 

 passengers on board ship that by taking the temperature of the sea surface at short 

 intervals the approach to ice is unfailingly indicated. Unfortunately such is by no 

 means the fact, and reliance thereon invites disaster. More than ordinarily cold 

 water merely shows that the ship is in a part of the ocean where ice may possibly 

 be encoimtered, and not that it is actually present. 



By kind permission, and on the unexceptional authority of Tapts. Ballantine, Dutton, 

 and Smith, of the Allan Mail Steamship Line, all men of high standing in the profes- 

 sion and well acquainted with ice navigation, it is here stated that no appreciable 

 difference in the temperature of the sea surface is caused by the proximity of even the 

 largest icebergs, and when one considers what a poor conductor of heat water is, their 

 statement can be well believed. * * * 



In a letter to the author, Lord Kelvin says: "The conducting power of water is so 

 small that there would be absolutely no cooling effect by conduction to a distance 

 from an iceberg; but there might be a considerable effect by the cold and light fresh 

 water running down from the iceberg, and spreading far and wide over the surface 

 of the sea. " 



This seems a reasonable supposition, but it is more than likely that the film of cold 

 fresh water would be broken up by the agitation of the wind and waves, and in any 

 case disturbed and turned over by the plowlike action of a vessel's bow going at speed. 

 Under these circumstances the hydrometer would be no better than the thermometer. 



Again, it is well known that about the Banks the Labrador current is someimes colder 

 when no ice is to be seen than it is when the contrary is the case. In winter its surface 

 temperature even falls to 28° F. Large icebergs have been actually passed at a dis- 

 tance of a quarter of a mile, and the sea-surface temperature tested carefully without 

 finding a single degree of difference from what previously existed when there were none 

 in sight. 



It may be fairly assumed, therefore, 1hat no reliance is to be placed upon the ther- 

 mometer as an immediate or direct means of detecting the presence of ice, especially 

 when it takes the form of stray bergs. In fog it will simply tell you when the ship 

 has entered the cool current, which may, or may not, be ice bearing. 



Dr. W. Bell Dawson, director of the Canadian In'drographic 

 survey, has made a stud}^ of the temperature effect of an iceberg in 

 the Strait of Belle Isle. In his report to the department of marine 

 and fisheries, in 1907, he says: 



Icebergs in relation to ivater temperature. — On August 7, 1894, an unusually large 

 iceberg was agroimd in 57 fathoms off C'hateau Bay, An instrumental survey made 

 in a boat showed it to be 780 feet long, 290 feet wide, and 105 feet high. The water 



