31) 



Smtgus reported blowing her whistle but hearing no echo until the 

 vessel backed off the ice ledge when a faint echo was heard. The 

 absence of an echo during a fog, while in the ice area, does not 

 necessarih' indicate the absence of ice nor does an echo necessarily 

 indicate an obstruction. 



The ice mirage was only observed on one day during the patrol 

 and that was to the southward, in latitude 43° 12' N. during the 

 latter part of May, when a large berg, 500 feet long and 262 feet high, 

 was observed 20 miles away. A peculiar ice blink was noticed before 

 the berg made its appearance. Mirages are frequent under favorable 

 atmospheric conditions on the southern and eastern sides of the ice 

 regions where the cold and warm waters mix. Bergs then appear 

 inverted and assume fantastic shapes, causing them to appear much 

 larger than they really are. 



Experiments were made to determine the submergence of ice^ 

 Regular cakes of ice 9 by 18 by 9 inches, were cut and placed in the' 

 sea water and tested under various conditions. The ice variably 

 floated 8 inches underwater and 1 inch out of water. 



In carrying out the above experiments it was found that the water 

 from the bergs was fresh and pure. Furthermore, no definite lines 

 of cleavage were noted in the ice and that submergence seemed to 

 depend on the mass and not on the height. 



Generally speaking, the presence of a berg did not influence the 

 temperatures of the water in the immediate vicinity. It was usually 

 the case that when a vessel passed from water of one temperature 

 to water of a lower temperature, it marked the passage of the vessel 

 from a warm current to a colder current. The method of taking 

 temperatures on board sliip does not really enable detection of a 

 slight rise or fall in temperature — not less than one-half degree; 

 so that possibly the use of a ver}^ sensitive thermometer may dis- 

 prove these statements. But it is believed that for practical pur- 

 poses the berg does not alter the temperature of the water. 



The Labrador current was ordinarily considered the carrier of 

 the menace until the Tail of the Banks was reached, when the ice 

 was subjected to other influences. Next to the current the wind 

 affected the drift of the bergs the greatest. The wind affected some 

 bergs more than others. Bergs with, one or two pinnacles were 

 affected the most and were the hardest to trail. Heavy seas affected 

 the drift, also, in addition to materially assisting in destroying the 

 berg. It was rarely the case of a berg drifting against the current, 

 but it was quite often the case of a berg drifting against the -svind. 

 It was noted in a number of cases that the bergs were in the center 

 of the area surrounded by detritis and growlers. It was thus shown 

 that it was not always the case that the disintegrated fragments 

 drifted to leeward, leaving clear water to windward. Vessels thus 

 observing growlers should navigate with extreme caution. 



