55 
Chapter VIII. 
THE SEA-ICE AND THE SHORE-ICE. 
The Sea-ice. 
During tlie winter months the surface of the sea in high latitudes often freezes 
in a uniform sheet which does not vary greatly in thickness. This covering has 
had many names given to it, but on the whole Sea-ice is perhaps the most suitable, 
as suggesting that the ice is derived directly from the sea. 
Sea-ice requires to be distinguished from other floating ice (ice at sea) of 
different origin, and this 
can readily be done by the 
close examination of even 
a small fragment. The 
Structure of sea-ice has 
been dealt with by Dr. 
Axel IIamberg,* Dr. von 
Drygalski,! and others. 
Dr. von Drygalski describes 
sea-ice as being composed 
of bundles of fibres packed 
together perpendicularly to 
the surface of cooling. A 
point not mentioned by 
him is, that, when the sea 
first freezes, the upper two 
inches consists of plates, 
a quarter of an inch across 
and a sixteenth of an inch thick, which lie horizontally, and only gradually do these 
give place to the sheaves of vertical fibres which make up the greater mass of the 
ice. Between the plates and the fibres is a layer of ice, about half an inch thick, 
of which the structure is very confused. Fig. 29 shows a mass of ice-crystals which 
have grown upon a fishing line. Mr. Hodgson records these crystals as occupying 
a length of 17 fathoms of his line, and gradually diminishing in quantity from 
the surface downwards. 
The Salinity * f seems to depend more upon the rate of freezing than upon the 
depth or distance from the surface. Both the authors quoted above have made 
* Axel Hamberg, Bihang, K. Svenska. Vet.-Akad. Handl., 1895, Bd. xxi, Afd. 2, No. 2. 
t Drygalski, 1 Gronland-Expedition,’ 1897, Bd. i, p. 424. 
Fig. 29. — Crystals of Ice which have grown upon a Fishing Line 
SEVERAL FATHOMS BELOW THE LOWER (OR FREEZING) SURFACE OF 
THE SEA-ICE. 
