Lecture Ii. Pages 26-53

LIGHTNING CONDUCTORS.

Destructive Effects of Lightning--Destruction of Buildings--Destruction of Ships at Sea--Destruction of Powder Magazines--Experimental Illustrations--Destruction of Life by Lightning--The Return Shock--Franklin’s Lightning Rods--Introduction of Lightning Rods into England--The Battle of Balls and Points--Functions of a Lightning Conductor--Conditions of a Lightning Conductor--Mischief Done by Bad Conductors--Evil Effects of a Bad Earth Contact--Danger from Rival Conductors--Insulation of Lightning Conductors--Personal Safety in a Thunder Storm--Practical Rules--Security Afforded by Lightning Rods

APPENDIX. Pages 55-62

RECENT CONTROVERSY ON LIGHTNING CONDUCTORS.

Theory of Lightning Conductors Challenged--Lectures of Professor Lodge--Short Account of his Views and Arguments--Effect of Self-Induction on a Lightning Rod--Experiment on the Discharge of a Leyden Jar--Outer Shell only of a Lightning Rod Acts as a Conductor--Discussion at the Meeting of the British Association, September, 1888--Statement by Mr. Preece--Lord Rayleigh and Sir William Thomson--Professor Rowland and Professor Forbes--M. de Fonvielle, Sir James Douglass, and Mr. Symons--Reply of Professor Lodge--Concluding Remarks of Professor Fitzgerald, President of the Section--Summary Showing the Present State of the Question

LIST OF ILLUSTRATIONS.

PAGE

THE ELECTRIC SPARK: A TYPE OF A FLASH OF LIGHTNING, 8

CARDBOARD DISC WITH BLACK AND WHITE SECTORS; AS SEEN WHEN AT REST, 12

SAME DISC; AS SEEN WHEN IN RAPID ROTATION, 12

THE BRUSH DISCHARGE, ILLUSTRATING ST. ELMO’S FIRE, 17

ORIGIN OF SUCCESSIVE PEALS OF THUNDER, 22

VARIATIONS OF INTENSITY IN A PEAL OF THUNDER, 24

DISCHARGE OF LEYDEN JAR BATTERY THROUGH THIN WIRES, 27

GLASS VESSEL BROKEN BY DISCHARGE OF LEYDEN JAR BATTERY, 32

GUN COTTON SET ON FIRE BY ELECTRIC SPARK, 33

VOLTA’S PISTOL; EXPLOSION CAUSED BY ELECTRIC SPARK, 34

THE RETURN SHOCK ILLUSTRATED, 35

PROTECTION FROM LIGHTNING BY A CLOSED CONDUCTOR, 48

INDUCTION EFFECT OF LEYDEN JAR DISCHARGE, 56