The other sciences were also joining in the march of progress. Chemistry was fast becoming a settled science; Priestley’s discovery of oxygen, in 1774, had created a great sensation; Cavendish shortly afterwards, in 1783, discovered the constitution of water; and Lavoisier, in 1789, summarised the combined researches of these two chemists and himself in his “Elements of Chemistry,” which at once was recognised as the standard work on the subject. Astronomy had, since Newton’s discovery of gravitation, assumed a more settled condition, but was destined to further modification by the enunciation of the nebular hypothesis by Laplace, who commenced to publish his bulky work, “ Mecanique Celeste,” in 1799. The nineteenth century opened with progress, as it were, on the gallop. In 1804 the first locomotive engine was started in England, at the same time that the first screw steamer was run at New York. It is needless to enumerate all the inventions of scientific men during the century, which are so well known to every one. Suffice it to say that, in a marvellously short space of time, the whole face of Europe has been changed. Railways cross each other at all points, like a huge network; telegraph wires link together as one place all important centres of population; public buildings are protected from nature’s freaks by lightning conductors; lighthouses dot the whole length of our coasts; the penny postage conveys our thoughts to and fro throughout the length and breadth of the land; a free press ventilates our grievances and enlightens our minds; hospitals and dispensaries minister to the sick and maimed wherever we go; and the Habeas Corpus Act endows each well-disposed individual with freedom and liberty. What a metamorphosis to be effected in so short a time!