By allowing the boys to create fire, the first necessity of civilization, Piggy's glasses represent science and technology, mankind's power to transform and remake their environment to best suit its needs.
Piggy's Glasses Symbol Timeline in Lord of the Flies
The timeline below shows where the symbol Piggy's Glasses appears in Lord of the Flies. The colored dots and icons indicate which themes are associated with that appearance.
...tomorrow and have a feast. To cook the meat, they'll raid Ralph's group for Piggy's glasses. Meanwhile, Ralph, Piggy, and Samneric discover four people aren't enough to keep the fire going.... (full context)