The origin of these valuable instruments is uncertain: that the ancients were acquainted with the laws of refraction is beyond all doubt, since they made use of glass globes filled with water to produce combustion; and in Seneca we find the following very curious passage—“LitterÆ, quamvis minutiÆ et obscurÆ, per vitream pilam aqu plenam majores clarioresque cernuntur;” yet thirteen centuries elapsed ere spectacles were known. It is supposed that they were first invented by Salvino or Salvinio Armati; but he kept his discovery secret, until Alessandro de Spina, a monk in Pisa, brought them into use in 1313. Salvino was considered their inventor, from the epitaph on his tomb in the cathedral church in Florence: “Qui giace Salvino d’Armato, degl’ Armati di Firenze, inventor delli occhiali, &c., 1317.” Another circumstance seems to add weight to this presumption: Luigi Sigoli, a contemporary artist, in a painting of the Circumcision, represents the high-priest Simeon with a pair of spectacles, which, from his advanced age, it was supposed he might have needed on the occasion.