The saline matter obtained from the ashes of wood, by causing water to pass through them; the water imbibes the salt, which is then obtained from it by evaporation. When purified by calcination, it is termed pearlash. In countries where there are vast forests, as in America and Russia, it is manufactured on a very large scale. What can you say of the origin of Glass? The period of its invention is quite unknown. Pliny relates that some merchants, driven by a storm to the coast of Phenicia, near the river Belus, made a large fire on the sand to dress some food, using as fuel some of the plant Kali, which grew there in great abundance; an imperfect glass was thus formed by the melting of the sand and ashes together. This production was picked up by a Syrian merchant, who, attracted by its great beauty, examined the cause of its origin, and, after many attempts, succeeded in its manufacture. Who was Pliny? A celebrated Roman naturalist and historian. At what place was Glass first made? Some authors mention Sidon in Syria, which became famous for glass and glass-houses; but others maintain that the first glass-houses noticed in history were built at Tyre; which, they add, was the only place where glass was made for many ages. It is certain that the art was known to the Egyptians. What is Phenicia? A sub-division of Syria in Asia. What is an author? A person who writes a book. What is signified by a glass-house? A building erected for the making and working of glass. What countries had glass windows first? Italy, then France and England; they began to be common about the year 1180. In what year, and where, was the making of glass bottles begun? In 1557, in London. The first glass plates for mirrors and coach-windows were made at Lambeth, in 1673. What is a Mirror? A body which exhibits the images of objects presented to it by reflection. The word mirror is more peculiarly used to signify a smooth surface of glass, tinned and quicksilvered at the back,[3] which reflects the images of objects placed before it. [Footnote 3: See Chapter XII., article Mercury.] Are they a modern invention? The use of mirrors is very ancient; mention is made of brazen mirrors or looking-glasses in Exodus, the 38th chapter and 8th verse. Some modern commentators will not admit the mirrors themselves to have been of brass, but of glass set or framed in brass; but the most learned among the Jewish rabbins say that in those times the mirrors made use of by the Hebrew women in dressing their heads were of metal, and that the devout women mentioned in this passage made presents to Moses of all their mirrors to make the brazen laver for the Tabernacle. It might likewise be proved that the ancient Greeks made use of brazen mirrors, from many passages in the ancient poets. _Commentators_, explainers of passages in the Bible, &c. _Rabbins_, doctors among the Jews, their learned men or teachers.