APRIL* 25, 185+4.] 
of planking in their vulnerable parts for ice- 
navigation, makes the ordinary metal sheathing 
of but little importance. This wooden sheath- 
ing varies considerably in arctic vessels as to 
the parts of the ships that are plated, the 
thickness and amount, and kinds of hard or 
soft wood planking. 
Having decided to build a wooden vessel, 
the shape of the hull is not a matter of in- 
difference. The full, round ship, or, nautically 
speaking, a ship with full lines, is much more 
liable to be crushed by ice-pressure than one 
built with sharp lines; as fully illustrated in 
Koldeway’s German expedition, when the Ger- 
mania, built upon the latter principle, stood 
the ice-nip without very serious consequences 
during a heavy storm, while her companion 
the Hansa was crushed and sunk, -she being 
modelled upon the former plan; and this, de- 
spite the fact that the Germania was the larger 
vessel, and therefore more liable to destruc- 
tion than her lighter escort. This was also 
said to be the fault with the Jeannette, whose 
cross-section is shown in fig. 1, taken from 
Mrs. De Long’s ‘The voyage of the Jean- 
nette.’ Nothing less than an ‘ ice-tongue,’ 
whose submerged edge would be below the 
point braced by the inclined beam at its foot, 
would have been of much use to save her in 
a ‘nip’ by the method of lifting already 
noticed. 
These ‘ ice-tongues’ are very much less fre- 
quent than most people might suppose from 
the constant use of the expression in this arti- 
cle. ‘They are really very rare; at least, of 
such shape and size as those indicated. The 
edges of an ice-cake or an ice-floe may be 
of any shape consistent with unequal melting of 
its parts, and the ‘tongue’ is only one of the 
rare varieties. If very acute, it may be too 
weak to wedge up a boat, and may break off, as 
I saw in one instance, which, luckily, was not 
caused by a‘ nip,’ or the ship would have been 
immediately crushed. It is upon the relative 
position of these inequalities of the ice-edge 
fore and aft of a ship, that depends whether 
or not she will inevitably be crushed when 
two cakes or floes come together at her posi- 
tion during a heavy ice-pressure: therefore, 
the larger the ice-cakes in a pack, the better is 
her chance of escape. 
The ease with which a ship can be lifted is, 
of course, a direct function of her size and 
weight. The size for an arctic exploring-ves- 
sel may vary, depending upon the service to 
which she may be put, and the time she is to 
be employed in polar seas; still, the general 
principle that a vessel should be as small as 
SCIENCE. 507 
possible, compatible with the object in view, 
is a good one. The smaller and lighter the 
boat, the more easily is she raised by the 
squeezing floes ; and the cases where this lifting 
of a vessel from the glacial vice, in one or 
two instances completely from her element, 
has been the salvation of her, are sufficiently 
numerous to be taken into account. Again: 
a small ship is more readily handled in the 
tortuous channels through which she is often 
compelled to thread her way while working 
in floes just sufficiently open to allow pro- 
gress. 
While arctic authorities agree upon the em- 
ployment of small ships, the exact size in tons 
is seldom stated; but, in the few cases men- 
tioned, about four hundred tons may be taken 
as the maximum limit. The superiority that 
a large vessel has over a smaller one in its 
greater momentum, when called upon to ‘ ram’ 
the ice, so as to force a passage, is compen- 
sated by the fact, which experience has fully 
settled, that the large ship will succumb sooner 
to these severe and repeated shocks that she 
is thus compelled to bear. It should be added, 
that it is only when the floes are small, and 
the ice comparatively loose, that any ship, 
whatever may be her size, can ‘ram’ it with 
any fair prospect of effecting a passage. A 
steamer intended for ‘ramming’ the ice is 
always strengthened at the bows by ‘dead- 
a 
Fig. 2.—‘ Deadwood * backing for bows. 
wood,’ or a solid wood backing (Fig. 2) not 
unlike that given to trial-targets for ordnance 
practice in solidity and strength. The depth 
of this may reach as much as twenty feet, 
although I have only heard of and never seen 
such depth. It may be cut off abruptly perpen- 
dicular to the keel (a), or given a parabolic 
flare (6), which, for the same amount of wood, 
is evidently the stronger for the various strains 
that the bow of an ice-vessel may be called 
upon to bear. 
With a vessel thus provided, sometimes a 
triangular indentation of a thin floe may be 
‘rammed,’ and the ice split by the wedge, the 
vessel burying herself in the crack; and then, 
when there is a large crew, their running in a 
body from port to starboard, and reverse, by 
rocking the vessel, has been known to increase 
the new ‘lead,’ and allow the vessel to baek 
