Centuries.--Sketch of Goodyear.--His Inventions and Present State of the Art.--Glass Wool of Volcano of Kilauea and Krupp’s Blast Furnaces. 457 INVENTIONS IN THE CENTURY. CHAPTER I. INTRODUCTORY--INVENTIONS AND DISCOVERIES--THEIR DEVELOPMENT. In treating of the subject of Inventions it is proper to distinguish them from their scientific kindred--Discoveries. The history of inventions is the history of new and useful contrivances made by man for practical purposes. The history of scientific discoveries is the record of new things found in Nature, its laws, forces, or materials, and brought to light, as they exist, either singly, or in relation, or in combination. Thus Galileo invented the telescope, and Newton discovered the law of gravitation. The practical use of the invention when turned to the heavenly bodies served to confirm the truth of the discovery. Discovery and invention may be, and often are, united as the soul is to the body. The union of the two produces one or more inventions. Thus the invented electro-telegraph consists of the combination of discoveries of certain laws of electricity with an apparatus, by which signs are communicated to distances by electrical influence. Inventions and discoveries do not precede or follow each other in order. The instrument may be made before the laws which govern its operation are discovered. The discovery may long precede its adaptation in physical form, and both the discovery and adaptation may occur together. Among the great _inventions_ of the past are alphabetical writing, Arabic notation, the mariner’s compass, the telescope, the printing-press, and the steam-engine. Among the great _discoveries_ of the past are the attraction of gravitation, the laws of planetary motion, the circulation of the blood, and velocity of light. Among the great inventions of the nineteenth century are the spectroscope, the electric telegraph, the telephone, the phonograph, the railways, and the steam-ships. Among the great discoveries of this century are the correlation and conservation of forces, anæsthetics, laws of electrical energy, the germ theory of disease, the molecular theory of gases, the periodic law of Mendeljeff in chemistry, antiseptic surgery, and the vortex theory of matter. This short enumeration will serve to indicate the different roads along which inventions and the discoveries of science progress. By many it is thought that the inventions and discoveries of the nineteenth century exceed in number and importance all the achievements of the kind in all the ages of the past.