AND CIRQUES IN NORWAY AND GREENLAND. 155 



once only in three days. The " calving " was accompanied by a ter- 

 rific crash, and by white clouds of spray (or comminuted ice ?) 

 hurled into the air. Simultaneously an enormous jagged mass of 

 ice, forming part of the terminal wall of the glacier, was seen to 

 turn over, bringing its edge, as it rotated, high above the level of 

 the glacier. As it rose, huge towering pinnacles were shattered, 

 and came crashing down in fragments, like a shower of gravel. Tho 

 " calving," which had commenced at a place near the middle of the 

 glacier, was continued in another. A second large mass of the solid 

 glacier broke loose, and at first moved almost horizontally, at tho 

 rate of perhaps a metre in a second. This, like the glacier itself, 

 was cleft into ice pinnacles, and the one group in moving past the 

 other produced a curious effect. How many bergs were produced in 

 this " calving" I cannot say, as they were formed simultaneously in 

 several places ; further, white clouds of spray partly concealed the 

 glacier, and the old bergs in front of it were set in motion ; there 

 was an indescribable confusion and a continuous crashing noise, 

 which lasted for about half an hour, then things became once more 

 quiet. The height of one of the bergs formed by the " calving " 

 was by measurement 89 metres. 



In order to estimate the quantity of ice discharged by a fjord, we 

 must know the thickness, breadth, and rate of motion of the glacier. 

 The first cannot be directly measured, except so far as it rises above 

 the sea; but if we know the proportional parts of a berg above and 

 below water, we can form an idea of the thickness of the glacier. 

 Taking the specific gravity of water as unity and that of ice 0918 

 (according to Brunner), the volume above the water is O082, or 

 about one twelfth of the whole. In the case of the bergs, however, 

 there is not so much submerged, because of the saltness of the fjord 

 water and the lower specific gravity of the ice, owing to the included 

 air-bubbles. To determine this specific gravity, I took five pieces of 

 ice from the bergs and put them into water. Into this I continued 

 to pour alcohol until three of the pieces sank, the others still float- 

 ing, and observed the specific gravity with an alcoholometer. I 

 then placed in the mixture a piece of solid ice, and added water 

 until it would neither sink nor rise. The difference between the 

 specific gravity of these two mixtures is about equal to the difference 

 between the specific gravities of the ice with bubbles and the solid 

 ice*. From these experiments (on ice from bergs in Disko Bay) I 

 found that the specific gravity of the bergs is decreased by 0*032 

 on account of the air-bubbles, or from 0*918 to 0*886. The specific 

 gravity of the water in the ice-fjord varies; it was 1*0228 in 

 Jakobshavn Fjord, near to the mouth of Tasiussak. From these ex- 

 periments it results that 0*86 of a berg is under, and 0*14 is above 



* The specific gravity of the ice when it neither sinks nor rises is not exactly 

 equal to the specific gravity of the mixture ; for the fragments partly dissolve and 

 are surrounded by water, and so sink in a niixl are of higher specific gravity than 

 that of the ice itself: the difference, however, between the specific gravity of 

 the mixtures is nearly, though not exactly, equal to the specific gravity of the 

 ice-pieces. 



