These are the objects of the series of Readable Books in Natural Knowledge to which the present volume belongs. Each volume will endeavour to stimulate interest in the studies with which it is concerned, and to present natural phenomena and laws broadly and attractively. It is hoped that the books will provide the reading matter urgently required in connection with the science work in schools and will appeal also to a wide circle of other readers. The series should be of service in directing attention to the nobility of scientific ideals and the ultimate value of results obtained by careful and faithful work. CONTENTS CHAP. PAGE 1. ARCHIMEDES 1 2. THE WISE MEN OF ALEXANDRIA 11 3. ARABIAN DAYS 22 4. DR. GILBERT OF COLCHESTER 34 5. GALILEO 50 6. THE BAROMETER 65 7. THE AIR-PUMP 80 8. THE INVENTOR OF THE STEAM-ENGINE 88 9. ELECTRIC SPARKS 100 10. THE ELECTRIC CURRENT 113 11. THE ELECTRIC TELEGRAPH 124 12. THE TELEPHONE 136 13. ELECTRIC LIGHT 149 14. MICHAEL FARADAY 159 15. TELEGRAPHING WITHOUT WIRES 170 16. THE NEW RAYS 178 17. AIR-SHIPS AND FLYING MACHINES 190 CHAPTER I ARCHIMEDES THE land of Italy is shaped like a boot, and at the toe of the boot lies a three-cornered island called Sicily. It was famous in ancient times for its cities, temples, and palaces; for its fruit-gardens and cornfields; and for its great volcano called Etna, from the top of which a cloud of steam and dust ascends, and sometimes a fiery stream of molten rock flows down. Sicily has often been shaken by earthquakes, but the worst of all was the earthquake which destroyed the town of Messina at Christmas 1908. The greatest city of Sicily was called Syracuse. It is now a town of 25,000 inhabitants, built on an island joined to the mainland by a bridge. But in ancient times it had ten times as many people, and its buildings covered the heights and cliffs opposite, and extended along the banks of the river, up to where the papyrus plants grow, which the ancients made into paper.