An elementary treatment of the theory of spinning tops and gyroscopic motion, by Harold Crabtree.

6

INTRODUCTORY CHAPTER

continue to spin in an upright position; the other one will
lie down on its side at once, and spin violently lying at full
length on the table. Some such tops are a little uncertain
which to do. That in Fig. viII. has been constructed so that
the head can be unscrewed and water poured in. If empty
it spins very well, whether a big or
little spin be originally given to it.
When it is full of water a little spin
will only result in the top falling to
the ground; a good spin will keep it
upright in spite of the water. Such
tops can be readily constructed out
of small tins or similar receptacles
capable of being soldered and made
water-tight.
Figs. IX. and x. represent two hol_ Ad low china eggs, exactly similar, with
the exception that one has been filled
FI. VIII. with water and the hole stopped up
with sealing wax. If they are laid
down on the table, and a spin is given to each of them about
a vertical axis, they will behave in entirely different ways. The
empty one jumps up briskly on its end and continues to spin
in that position for a long time; the other will spin slowly on
its side for a short time and continue this uninteresting motion
till it stops: or if stopped prematurely by laying a finger on
it, will begin to spin again on removing the finger.
i
FIG. IX.-Egg full. FIG. X.-Egg empty.
A real egg, if unboiled, and especially one which has had
its yolk thoroughly shaken up into liquid form, will behave
in precisely the same way; but a hard boiled egg will spin
up on its end at once (especially if the table is rough) and
continue spinning for a long time. A similar phenomenon can
also be observed with acorns at a time when they are lying
thick in the roads. If they are kicked, in any way whatever,
they almost invariably skid along for a little way and then