140 
CRUISE OF H.M.S. CHALLENGER . 
colours were traced along its edges. Bright streams 
of light frequently darted upward from the clouds 
to the zenith, forming coronse, and exhibiting 
brilliant flashes of all the prismatic colours. Several 
whales and numerous sea-birds were in sight. 
Feb. 19 th . — From the great quantities of ice found 
drifting along our course, it appears evident we are 
not far from extensive fields, and as many as eighty 
magnificent icebergs were in sight at one time ; thus 
for days we sail on a straight course, bounded with ice 
islands from a quarter of a mile to five miles in length. 
The question naturally arises, how and where are 
these masses formed ? * That they are commenced 
on the land seems to be considered conclusive from 
the fact that earth and stones are frequently seen 
on them. After a time they are probably detached 
from their original place of formation by some violent 
storm, and the prevailing winds drive them to the 
north and west, where they are met with in every 
stage. Those that had been recently detached were 
easily detected by their beautiful stratified appearance, 
while others of older date had lost their original 
form by the sea constantly washing over them. 
There is a great variety of opinions as to the time 
required for the formation of these immense masses 
of ice, for those met with farthest south, and seem- 
ingly showing but little signs of decay, averaged 
200 to 250 feet in height above the water. The 
* ‘ United States Exploring Expedition.’ 
