Both Uses

ballast
in
Nation, by Terry Pratchett
(Auto-generated)

And here they came.... And so it was that the schooner Sweet Judy sailed though a rain forest, with Captain Roberts, inspired to instant creativity, making up a new verse explicably missing from the original hymn: "Oh Thou who built'st the mountains high, To be the pillars of the sky—" He wasn't totally certain about built'st, but bidd'st was apparently acceptable—"Who gave the mighty forests birth"—branches cracked like gunshots under the keel, thick vines snatched at what remained of the masts— "And made a Garden of the Earth"—fruit and leaves rained down on the deck, but a shudder meant that a broken tree had ripped away part of the hull, spilling the ballast—"We pray to Thee to stretch T†
Chpt 1.
Maybe they brought the stones as ballast.†
Chpt 9. *

Definitions:

(1) (ballast)
something that helps to stabilize -- especially heavy material in the bottom of an empty ship
(2) (meaning too rare to warrant focus)
Less common senses of ballast include: coarse gravel laid to form a bed for streets and railroads

or:

a resistor inserted into a circuit to compensate for changes (such as is used to start and regulate fluorescent bulbs)