"
"You deceive yourself. It is not scientifically built, to begin, and
there is a cause at work that will infallibly burst it, if not looked to
in time."
"And what is that, sir?"
"The dam is full of crabs."
"So 'tis; but what of them?"
"I detected two of them that had perforated the dyke from the wet side
to the dry, and water was trickling through the channel they had made.
Now, for me to catch two that had come right through, there must be a
great many at work honeycombing your dyke; those channels, once made,
will be enlarged by the permeating water, and a mere cupful of water
forced into a dyke by the great pressure of a heavy column has an
expansive power quite out of proportion to the quantity forced in.
Colossal dykes have been burst in this way with disastrous effects.
Indeed, it is only a question of time, and I would not guarantee your
dyke twelve hours. It is full, too, with the heavy rains."
"Here's a go!" said Dick, turning pale. "Well, if it is to burst, it
must."
"Why so? You can make it safe in a few hours. You have got a clumsy
contrivance for letting off the excess of water: let us go and relieve
the dam at once of two feet of water. That will make it safe for a day
or two, and to-morrow we will puddle it afresh, and demolish those busy
excavators.
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