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.