424 B.C. Lenses made and used by the Greeks. And a lens has been found in the ruins of Nineveh. 79 A.D. Glass known and used by the Romans. 697. Glass brought to England. 1100. Alcohol first obtained by the alchemist, Abucasis. 1287. Nitric acid first obtained by Raymond Lully. Present properties made known by Dr. Priestley, 1785. 1297. Camera-obscura constructed by Roger Bacon. 1400. Chloride of gold solution known to Basil Valentine. 1500. Camera-obscura improved by Baptista Porta. 1555. Chloride of silver blackening by the action of light. Doubtless it was the knowledge of this that induced Thomas Wedgwood and Sir Humphry Davy to make their experiments. 1590. Paper first made in England, at Dartford, Kent, by Sir John Speilman. It is said that the Chinese made paper 170 years B.C. 1646. Magic lantern invented by Athanasius Kircher. 1666. Sir Isaac Newton divided a sunbeam into its seven component parts, and re-constructed the camera-obscura. 1670. Salt mines of Staffordshire discovered. 1727. J. H. Schulze, a German physician, observed that light blackened chalk impregnated with nitrate of silver solution and gold chloride. 1737. Solution of nitrate of silver applied to paper, by Hellot. 1739. Chloride of mercury made by K. Neumann. 1741. Platinum first known in Europe: M. H. St. Claire Deville's new method of obtaining it from the ore, 1859. 1750. J. Dolland, London, first made double achromatic compound lenses. 1757. Chloride of silver made by J. B. Beccarius. 1774. Dr. Priestly discovered ammonia to be composed of nitrogen and hydrogen; but ammonia is as old as the first decomposition of organic matter. 1777. Charles William Scheele observed that the violet end of the spectrum blackened chloride of silver more rapidly than the red end. Chlorine discovered. 1779. Oxalate of silver made by Bergmann. 1789. Uranium obtained from pitch-blende by Klaproth. 1791. Thomas Wedgwood commenced experiments with a solution of nitrate of silver spread upon paper and white leather, and obtained impressions of semi-transparent objects and cast shadows. Sir Humphry Davy joined him later. 1797. Nitrate of silver on silk by Fulhame. 1799. Hyposulphite of soda discovered by M. Chaussier. 1800. John William Ritter, of Samitz, in Silesia, observed that chloride of silver blackened beyond the violet end of the spectrum, thus discovering the action of the ultra violet ray. 1801. Potassium discovered by Sir Humphry Davy. 1802. Examples of Heliotypes, by Wedgwood and Davy, exhibited at the Royal Institution, and process published. 1803. Palladium discovered in platinum by Dr. Wollaston. 1808. Strontium obtained from carbonate of strontia by Sir Humphry Davy. 1812. Iodine discovered by M. D. Curtois, of Paris. -- Nitrate of silver and albumen employed by D. Fischer. 1813. Ditto investigated by M. Clement. 1814. Joseph Nicéphore de Niépce commenced experiments with the hope of securing the pictures as seen in the camera-obscura.