se up, so that the whole sea seems to be covered with
them, and little water can be seen, it is called "pack" ice. When the
pack is squeezed together, so that lumps of it are forced up in the form
of rugged mounds, these mounds are called "hummocks." A large mass of
flat ice, varying from one mile to many miles in extent, is called a
"field," and a mountain of ice is called a "berg."

All the ice here spoken of, except the berg, is sea-ice; formed by the
freezing of the ocean in winter. The berg is formed in a very different
manner. Of this more shall be said in a future chapter.

"Well, my lad," said Gregory, in reply to Jim Croft's last observation,
"I have not seen much of the ice yet, as you truly remark, so I hope
that the wind will not come to help us out of it for some time. You
don't think it dangerous to get into the pack, do you?"

"Well, not exactly dangerous, sir," replied Croft, "but I must say that
it aint safe, 'specially when there's a swell on like this. But that'll
go down soon. D'ye know what a nip is, Dr Gregory?"

"I think I do; at least I have read of such a thing. But I should be
very glad to hear what you have to say about it. No doubt you have felt
one."

"Felt one!" cried Jim, screwing up his face and drawing his limbs
together, as if he were suffering horrible pain, "no, I've never felt
one. The man what _feels_ a nip aint likely to live to tell what his
feelin's was. But I've _seed_ one."

"You've seen one, have you? That must have been interesting. Where was
it?"

"Not very far from the Greenland coast," said Croft, giving his quid
another turn. "This was the way of it. You must know that there was
two ships of us in company at the time. Whalers we was. We got into
the heart of the pack somehow, and we thought we'd never get out of it
again. There was nothin' but ice all round us as far as the eye could
see. The name of our ship was the _Nancy_. Our comrade was the
_Bullfinch_. One mornin' early we heard a loud noise of ice rubbin'
agin the sides o' the ship, so we all jumped up, an' on deck as fast as
we could, for there's short time given to save ourselves in them seas
sometimes. The whole pack, we found, was in motion, and a wide lead of
water opened up before us, for all the world like a smooth river or
canal windin' through the pack. Into this we warped the ship, and
hoistin' sail, steered away cheerily. We passed close to the
_Bullfinch_, which was still