Show unbreakable spectacle unbreakable spectacle lenses are a recent invention two pieces of glass with a piece of celluloid between them are cemented together under pressure for forming ieng one solid piece this glass sandwich to la slightly thicker than ordinary glass but it to la just as transparent the celluloid being invisible unbreakable glass has tor for some boine tinne time been employed in the windshields wind shields of motor vehicles find and airplanes and in goggles but this la Is believed to be its first uso use in spectacles |