Assertion: lens | /r/ObjectUse | used as burning-glasses
Facets:
value: for at least 2400 years
type: TEMPORAL
Source sentences:
text: Since ignition can be achieved even with a poorly made lens, lenses have been used as burning-glasses for at least 2400 years.
text: Since ignition can be achieved even with a poorly made lens, lenses have been used as burning-glasses for at least 2400 years.