Chemistry also received valuable extensions of its field. Dr. John Mayow published new facts respecting nitre, and on the phenomena of respiration and combustion, as revealed by experiments on this and other substances. At the commencement of the eighteenth century Stahl, a German chemist, propounded his theory of phlogiston as the principle of combustion, which was only exploded by the further discoveries of Dr. Black, Cavendish, and Priestley. Soon after, Dr. Hales threw new light on aëriform bodies, or, as they are now termed, gases; and finally, Dr. Black demonstrated the presence of a gas in magnesia, lime, and the alkalies, which had long before been noticed by Van Helmont, but had been forgotten. This was then termed fixed air, but has now acquired the name of carbonic acid gas, or carbon dioxide. At the end of this period chemistry was extensively studied, and was rapidly revealing its secrets. The kindred science of medicine was also in marked advance. Dr. Thomas Sydenham, who died in 1689, at the very commencement of this period, had prepared the way for a more profound knowledge of the science by his careful and persevering observation of facts and symptoms; and the improvements he introduced guided medical men in the treatment of disease till the end of this period. Anatomical science was greatly advanced at this era by Malpighi, Steno, Ruysch, Duverney, Morgagni, Albinus, Haller, and other Continental physicians. In England Humphrey Ridley published a work on the brain in 1695, and William Cowper, in 1698, his anatomical tables, said to be borrowed from the Dutch anatomist, Bidloo. In 1726 Alexander Munro published his "Osteology;" he was also founder of the Medical School of Edinburgh. In 1733 William Cheselden, the most expert operator of his day, published his "Osteography." In 1727 Stephen Hales published his "Vegetable Statics," and in 1733 his "Hæmastatics," which carried both vegetable and animal physiology beyond all preceding knowledge either here or abroad. Zoology and comparative anatomy also received some progress from the labours of Nehemiah Grew, Tyson, Collins, and other members of the Royal Society. Music advanced at an equal rate with its sister arts, and during this period added to its conquests the compositions of Purcell and Handel. William was too much engaged in war to become a patron of music, or of any of the fine arts, and his queen, Mary, does not appear to have possessed much taste for it. She is related by Sir John Hawkins to have sent for Purcell and Mrs. Arabella Hunt, a famous singer, to entertain her. Mrs. Hunt sang some of Purcell's splendid compositions, and Purcell accompanied them on the harpsichord; but Mary soon grew weary of these, and called on Mrs. Hunt to sing the Scottish ballad, "Cold and Raw!"