SS 
Jun 20, 1912] 
NATURE 
ALI 
ICEBERGS AND THEIR LOCATION 
NAVIGATION. 
Origin of the North Atlantic Ice. 
*HE icebergs each year met with in the North 
Atlantic are almost entirely derived from 
western Greenland. The interior of Greenland is 
covered by a large ice-sheet forming an enormous 
glacier, which gradually moves outwards, meeting on 
its journey mountains and islands which form a 
fringe varying in width from a mere border up to 
eighty miles. This mountainous belt is penetrated by 
deep fiords, through which the ice passes towards the 
sea. As the huge ice-sheetsare forced into the sea 
they are broken off and set adrift as bergs. The 
“calving,” as it is called, may take place in a number 
of ways. 
Von Drygalski distinguishes three classes of bergs; 
those of the first class are the most massive of all, and 
separate with a sound like thunder from the entire 
thickness of the glacier front. They result from the 
buoyant action of the water as the glacier pushes out 
into the deep water. They usually regain their 
equilibrium after rhythmic oscillation, and float away 
in an upright position. Bergs of the second class are 
broken off under water from time to time. They rise 
and often turn over before they gain equilibrium, 
displaying in this way the beautiful blue colour of 
the lowest layers of ice. Bergs of the third class 
form almost continuously, and consist of large and 
small fragments which separate along the crevasses 
and fall into the sea. 
According to the report of the U.S. Hydrographic 
Office, the size of the pieces of ice set adrift varies 
very much, but bergs 60 to too ft. to the top of 
their walls, with spires and pinnacles from 200 to 
250 ft. high, are most often found. The length of 
such an average berg would be from 300 to 500 yards. 
The depths of these masses under water is variously 
given as from seven to eight times the height, but 
this is not always the case. It is possible to have a 
berg as high out of the water as it is deep below 
the surface, since the submergence depends entirely 
on mass, and not on height. It is possible to find 
bergs with a pinnacle rising high out of the water, 
but offering little weight to the mass below. Besides 
the icebergs formed from the Greenland glaciers, a 
few come around Cape Farewell from the Spitsbergen 
Sea, and some may be traced from Hudson’s Bay. 
IN 
Movement of Ice from the Arctic Regions. 
The Labrador current flows southward along the 
coasts of Baffin Land and Labrador. The average 
rate is from ten to thirty-six miles per day, but 
occasionally it ceases altogether (U.S. Hydrographic 
Report, 1909). Its rate is influenced by the wind, 
especially near the coast. As soon as free the ice- 
bergs find their way into the Arctic current and float 
gradually southward. The journey is by no means 
an easy one, and few bergs survive. There are 
many mishaps, such as grounding in the Arctic basin 
with ultimate breaking up, stranding along the 
Labrador coast, where destruction takes place, and 
falling to pieces entirely in the open sea. Only a 
small percentage ever reach the Grand Bank and the 
routes of the Transatlantic liners, so many delays | 
attend their journey. It is well known that many 
bergs seen in any one season may have been pro- 
duced several seasons before. Taking the Labrador 
current as ten miles per day, a berg once formed and 
drifting freely would make the journey southward 
in from four to five months. The difference in time 
1 Abridged from a discourse delivered at the Royal Institution on Friday, 
May 31. by Prof. Howard T. Barnes, F.R.S. 
NO. 2225, voL. 89| 
of two bergs reaching a low latitude may cover a 
period of one or two years, even when these start on 
the same day, so devious are the paths into which 
chance may direct, these floating masses. Under- 
currents affect the largest icebergs, and frequently 
they are seen to move backward against the wind 
and surface water. Extensive field-ice offers an 
obstruction to the movements of the bergs, hence 
the number met with from one season to another 
must depend on the mildness or severity of the 
previous summer in the north. 
Field-ice and its Distribution in the Gulf of St. 
Lawrence during the Winter. 
Icebergs are not alone in causing an obstruction to 
navigation in the Labrador current. Field-ice, which 
may extend over wide areas, presents great difficul- 
ties. This ice is salt water frozen in the bays and 
inlets along the shore, as especially in the Gulf of 
St. Lawrence. Immense fields are formed of pieces 
blown by the wind and massed together in an 
irregular way. Change of wind and tide causes the 
fields to float away. When several fields are blown 
shorewards together they grind and crush together, 
forming irregular ice many feet thick. Frost and 
spray soon cement this together into a hard mass, 
almost impossible to break. Floating again, these 
agglomerated ice masses, often many miles in extent, 
are carried out to sea, there to produce great danger 
to navigation. While the Gulf of St. Lawrence 
never freezes over entirely, there is to be found all 
the winter floating areas, which take up their posi- 
tion with the direction of the wind. As the spring 
advances these fields become weaker, and finally 
disappear. The last to open is the Straits of Belle 
Isle, where towards the end of June it becomes 
sufficiently free for ships to navigate. 
Limits of Region of Icebergs and Field-ice. 
From the reports carefully compiled by the U.S. 
Hydrographic Office, it has been found that in April, 
May, and June are to be found the greatest number 
of icebergs and the largest extent of field-ice. They 
have been seen so far south as the thirty-ninth degree 
of latitude, and so far east as longitude 38° 30’. In 
general, it may be stated that floating ice may be 
met with anywhere in the North Atlantic Ocean, 
northwards of the fortieth degree of latitude, at any 
season of the year. 
Surface Temperature of the Labrador Current in 
Winter and Summer. 
During the winter months the surface temperature 
of the Labrador current often falls to the freezing 
point of salt water, about 28° F., but it is more often 
at 29° or 30° F. As the spring advances the line of 
low temperature advances further north, until in July 
or August the temperature on the Grand Banks 
towards the Straits of Belle Isle reaches 40° or 45° F., ” 
and gradually falls northwards to 29° F. in Hudson’s 
Straits. The surface temperature varies considerably, 
depending on the proximity of ice or land, as will be 
explained shortly. No measurements have been made 
north of the Banks in winter or spring, when the 
Straits of Belle Isle are ice-bound. Reports of the 
temperature of the ice track are frequently made 
by sea captains. Results as low as 22° F. have been 
given to me; but I believe this to be impossible, and 
| due to some error of measurement arising from the 
crude method now in vogue on our Atlantic liners. 
Pettersson’s Theory of Ice Melting. 
Dr. Otto Pettersson has for some time shown ex- 
perimentally that ice melting in salt water produces 
