—, opaline, cause of color of, xxvi, 66.

— for optical purposes, manufacture of, A. Bourne, xl, 207.

—, porosity of, vii, 192.

—, spectacle, xxvii, 80.

—, silvering of, according to Drayton's method, xlix, 198.

— beads, manufactory of, at Venice, xxvii, 78.

— houses, improved mode of drying wood for, xvii, 163.

— vessels, method of cutting, xxiv, 206.

— or porcelain vessels, a crust formed on, removed by muriatic acid, xxvi, 188.

Glasses, lamp, to prevent the cracking of, xxi, 165.