Bibliography. 161 
ed at a time, without the aid of a glass, and some of them several miles 
long.” On the 18th, there were snow-flakes in six-rayed stars; tem- 
perature, 28° ; barometer, 28°76 inch. 
On the 19th the barrier trended more to the north; deep bays were 
frequent, out of which it was often necessary to return almost to the 
point of entrance, and the smoothness of the sea, which was narrowed 
by the ice so as to be like a river, produced some apprehension that 
the barrier might preelude a retreat ; but an increasing swell, indicating 
their approach to a clear sea, relieved this anxiety. it appears from 
the observations of the squadron, both in the present season and the 
last, that very little change takes place in the line of ice.* 
“It may be inferred that the line of perpetual congelation exists in a lower 
latitude in some parts of the southern hemisphere than in others. The icy bar- 
Tier retreats several degrees to the south of the Antartic Circle to the west of Cape 
Horn, while to the eastward it in places advances to the northward of that line, 
which is no doubt owing to the situation of the land. From the great quantities 
of ice to be found drifting in all parts of the ocean in high southern latitudes, I am 
induced to believe that the formation of the ice-islands is much more rapid than 
is generally supposed. The manner of their formation claimed much of my atten- 
tion while among them, and I think it may be explained satisfactorily and without 
difficulty, In the first place, I conceive that ice requires a nucleus, whereon the 
fogs, snow, and rain, may congeal and accumulate ; this the land affords. Acci- 
dent then separates part of this mass of ice from the land, when it drifts off, and 
is broken into many pieces, and part of this may again join that which is in pro- 
cess of formation. The sketch in Chapter LX. has already given the reader some 
idea of its appearance in this state. 
“From the accumulation of snow, such a mass speedily assumes a flat or table- 
topped shape, and continues to increase. As these layers accumulate, the field- 
ice begins to sink, each storm (there of frequent occurrence) tending to give it 
more weight. The part which is now attached to the land remains aground, 
whilst that which is more remote, being in deep water, is free to sink. The ac- 
cumulated weight on its outer edge produces fissures or fractures at the point 
where it takes the ground, which the frosts increase; thus separated, the surface 
again becomes horizontal, and continues to receive new layers from snow, rain, 
and even fogs, being still retained to the parent mass by the force of attraction. 
The fogs have no small influence in contributing to the accumulation : some idea 
may be formed of the increase from this cause, from the fact, that during a few 
hours the ice accumulated to the thickness of a quarter of an inch on our rigging 
and spars, though neither rain nor snow fell. It may, therefore, I think, be safely 
asserted that these icebergs are at all times on the increase; for there are few 
days, according to our experience in this climate, in which some mode of precipita- 
tion does not prevail in these high latitudes, where, according to our observations, 
ice seldom melts. The temperature of even the summer months being rarely 
above the freezing point, masses of a thousand feet in thickness might require but 
few years to form. Icebergs were seen in all stages of formation, from five to two 
hundred feet above the surface, and each exposed its stratification in horizontal 
* The remainder of this chapter is so important that we give it without abridg- # 
ment, that the author may present his conclusions in the most ample manner. 
Vol. xurx, No. 1.—April-June, 1845. 21 
