(_b_) EXPERIMENT TO SHOW THE PRODUCTION OF MAGNETISM BY AN ELECTRIC CURRENT 48 (_a_) LINES OF MAGNETIC FORCE OF TWO OPPOSITE POLES 50 (_b_) LINES OF MAGNETIC FORCE OF TWO SIMILAR POLES 50 A TYPICAL DYNAMO AND ITS PARTS 70 LOTS ROAD ELECTRIC POWER STATION, CHELSEA 76 POWER STATION BATTERY OF ACCUMULATORS 80 ELECTRIC COLLIERY RAILWAY 86 TYPICAL ELECTRIC LOCOMOTIVES 90 NIGHT PHOTOGRAPHS, TAKEN BY THE LIGHT OF THE ARC LAMPS 96 WHERE ELECTRICAL MACHINERY IS MADE 120 SPECIMEN OF THE WORK OF THE CREED HIGH-SPEED PRINTING TELEGRAPH 140 LARGE ELECTRIC TRAVELLING CRANE AT A RAILWAY WORKS 164 (_a_) MARCONI OPERATOR RECEIVING A MESSAGE 188 (_b_) MARCONI MAGNETIC DETECTOR 188 RÖNTGEN RAY PHOTOGRAPH OF BRITISH AND FOREIGN FOUNTAIN PENS 240 BACHELET “FLYING TRAIN” AND ITS INVENTOR 272 (_a_) CAVALRY PORTABLE WIRELESS CART SET 280 (_b_) AEROPLANE FITTED WITH WIRELESS TELEGRAPHY 280 ELECTRICITY CHAPTER I THE BIRTH OF THE SCIENCE OF ELECTRICITY Although the science of electricity is of comparatively recent date, electricity itself has existed from the beginning of the world. There can be no doubt that man’s introduction to electricity was brought about through the medium of the thunderstorm, and from very early times come down to us records of the terror inspired by thunder and lightning, and of the ways in which the ancients tried to account for the phenomena. Even to-day, although we know what lightning is and how it is produced, a severe thunderstorm fills us with a certain amount of awe, if not fear; and we can understand what a terrifying experience it must have been to the ancients, who had none of our knowledge. These early people had simple minds, and from our point of view they had little intelligence; but they possessed a great deal of curiosity. They were just as anxious to explain things as we are, and so they were not content until they had invented an explanation of lightning and thunder. Their favourite way of accounting for anything they did not understand was to make up a sort of romance about it. They believed that the heavens were inhabited by various gods, who showed their pleasure or anger by signs, and so they naturally concluded that thunder was the voice of angry gods, and lightning the weapon with which they struck down those who had displeased them. Prayers and sacrifices were therefore offered to the gods, in the hope of appeasing their wrath.