ning or not. It seemed to float idly in the
water, sinking slowly all the time; and yet they could not tell whether
it was drawn in by the drifting of the portion of the line already down,
or by the weight of the shot. So they could not tell certainly whether
they had reached bottom or not.

"There is another thing that is curious about it," added the captain;
"and that is, that, when a line is let out to such a length, they can
never get it back again."

"Why not?" asked Rollo.

"It is not strong enough," said the captain, "to bear the strain of
drawing such an immense length out of the water. There is a very
considerable degree of friction produced in drawing a line of any kind
through the water; and when the line is some miles in length, and has,
besides, a heavy ball at the end of it, the resistance becomes enormous.
Whenever they attempt to draw up a sounding line of such a length, it
always parts at a distance of a few hundred fathoms from the surface, so
that only a small part of the line is ever recovered."

"I should not suppose it would be so hard to draw up the line," said
Rollo. "I should have thought that it would come up very easily."

"No," said the captain. "If you draw even a whiplash through the water,
you will find that it draws much harder than it does on the grass; and
if a boy's kite were to fall upon a pond at a great distance from the
shore, I don't think he could draw it in by the string. The string would
break, on account of the friction of the string and of the kite in the
water. Sometimes, in naval battles, when a ship is pretending to try to
escape, in order to entice another ship to follow her, away from the
rest of the fleet, they tow a rope behind, and this rope, dragging in
the water, retards the ship, and prevents her from going very fast,
notwithstanding that all the sails are set, and she seems to be sailing
as fast as she can."

"That's a curious way of doing it," said Rollo; "isn't it, Jennie?"

Jennie thought that it was a very curious way indeed.

"There is no difficulty," said the captain, resuming his explanations,
"in finding the depth of the sea in harbors and bays, or at any place
near the shore; for in all such places it is usually much less than a
hundred fathoms. So when in a dark night, or in a fog, the ship is
driven by the wind in a direction where they know there is land, they
sound often; and when they find that the water is shoal enough, they let
go the anch