42 



after this berg was placed under observation, the entire mass that had 

 been above water, chiefly in two massive cUffs, respectively about 

 150 and 200 feet high, had been lost, and that the whole of the berg 

 then showing to an approximate average height of 60 feet had been 

 below the surface when the observation began on the 9th instant. 

 Owing to the substantial underfooting of this berg, it was at all times 

 in stable equilibrium, although there was considerable shifting of 

 trim at times — the result of important losses above water at various 

 points on its periphery. Stability was helped by the condition that, 

 as the berg emerged by successive stages, there was a generally 

 extended ledge of footing on all sides. The reduction of girth due to 

 loss had been carried on more rapidly above and near the surface 

 than below. Presenting on the 9th of June a general formation which 

 may be likened to that of floating dry dock, with the two cliffs at 

 either side running the full length of the berg, 400 to 500 feet, and a 

 floor between 80 to 100 feet wide at or near the surface, the action of 

 the sea was sufficient to maintain this condition for the berg through- 

 out. It continued to hold this form, although at the end of the sixth 

 Modoc cruise the floor was eroded to water level only at the side of 

 the smaller cliff; the emergence had become too rapid at the end 

 of the period to permit erosion of the whole floor. The berg con- 

 tinued to reduce in size from an upright position until June 24, when 

 it broke up into a small berg and innumerable growlers and finally 

 on June 30 it had completely disintegrated. 



A berg of average size in the mixed waters south of the Tail of the 

 Banks will survive as a menace to navigation for a period of 12 to 14 

 days during the months of April, May, and June, but will not sur- 

 vive longer than 10 to 12 days after that period. During the 1925 

 patrol the patrol vessels trailed a large berg in those waters for 30 

 days. A medium-sized berg will last about 7 days in the Gulf 

 Stream. The bergs grounded on the Banks last the longest. 



As stated before, the bergs seen by the patrol vessels were of the 

 Greenland type. It may be of interest, therefore, to state in general 

 the origin of the bergs and the nomenclature used in referring to the 

 ice. Although some definitions have been referred to in previous 

 reports, they will be repeated. 



Greenland, as is known, is covered by a large area of ice. The 

 temperature remains usually so low that no material decrease is 

 encountered by melting, and thus one layer of snow can not melt 

 before the next one falls. Thus a massive ice formation is produced 

 known as the Greenland ice cap. It is the largest in the Northern 

 Hemisphere. From this ice cap the Greenland glaciers are formed. 

 The process is never ending. The snow is converted into a form of 

 ice by the immense pressure. The ice is forced down to the sea by 

 the force of gravity and by the weight of the accumulation of the 

 snow and ice. The movement seaward is constant, as an enormous 



