apparently has no bottom. It will be filled and apparently the earth on
top is solid. After a few days there will follow either a gradual
shifting away or a sudden cave in, and the quicksand must once more be
attacked.

This condition had been experienced more than a dozen times with the
Man-killer before Tom and Harry had been called to solve the problem.

There is no definite way of attacking a quicksand. Much must depend
upon the local conditions. Where it is a small one, yet of seemingly
considerable depth, it is sometimes quickest and cheapest to cross it
with a suspension bridge, the terminal pillars resting on sure
foundations. Some quicksands are overcome by merely filling in new sand
or loam, patiently, until at last the trap is blocked and a permanently
solid foundation is laid. There are many other ways of overcoming the
difficulty.

The method hit upon by Tom and Harry, after looking over the situation,
was one that was largely original with them.

It consisted of laying logs, of different lengths, from twelve to
eighteen feet, in a transverse net work filling in earth on this and
allowing the structure gradually to sink where the quicksand shifted or
caved. The sideway drift, at some points, was overcome by hollow steel
piles, driven in as firmly as might be, and then filled with cement from
the top. A line of such piles when imbedded in the ground, helps to
make an effective block to side drift.

At the outset a few feet of these steel piles were left exposed above
the surface, their gradual settling serving as a reliable index to the