ot over the bottom if the cylinder is tipped to any
extent. So the cylinder falls over easily and lies quietly on its
side.]

[Illustration: FIG. 16. But in this one the center of weight is so low
that it is over the base, no matter what position the cylinder is in.]

[Illustration: FIG. 17. So even if the cylinder is laid on its side it
immediately comes to an upright position again.]

Try to tip the cylinder over. Now stuff some crumpled paper loosely
into the cylinder, filling it to the top. Tip the cylinder again. Will
it stay on its side now? Force all the crumpled paper to the bottom
of the cylinder. Now will it stay on its side? Take out the crumpled
paper and lay a flat stone in the bottom of the bell, holding it
in place by stuffing some crumpled paper in on top of it. Will the
cylinder tip over now? Take the stone out, put the crumpled paper in
the bottom of the cylinder, put the stone on top of the paper, and
again try to tip the cylinder over. Will it fall?

* * * * *

The center of the cylinder was always in one place, of course. But the
_center of the weight_ in that cylinder was usually near the bottom,
because the bell weighed so much more than the paper. When you raised
the center of weight by putting the stone up high or filling the
cylinder with crumpled paper, just a little tipping moved the center
of weight so that it was not directly over the bell on which the
cylinder was resting. Whenever the center of weight is not over the
base of support (the bottom on which the thing is standing), an object
will topple over. Moving the center of weight up (Figs. 15 and 16)
makes an object less stable.

The two main points to remember about stability are these: the wider
the base of an object, the harder it is to tip over; and the lower the
center of the weight is, the harder it is to tip over.

If you were out in a rowboat in a storm, would it be better to sit up
straight in the seat or to lie in the bottom of the boat?

Why is a flat-bottomed boat safer than a canoe?

[Illustration: FIG. 18. Which vase would be the hardest to upset?]

Where do you suppose the center of weight of the Leaning Tower of Pisa
is,--near the bottom or near the top?

_APPLICATION 8._ If you had a large flower to put into a vase
and you did not want it to tip over easily, which of the three
vases shown in Figure 18 would you choose?

_APPLICATION 9._ Some boys made themselv