CHAPTER IX.

THE LIGHTHOUSE SYSTEM.

Imperfect Illumination of the old Lighthouses--First Improvements--The Argand Lamp and Reflecting Mirrors--Revolving Lights--The Catoptric System--Varieties of Lights--The Dioptric System--Its Details--Introduction of this Method into Great Britain--Comparison of the two Methods--The Drummond and Voltaic Lights--Gurney's Lamp--Captain Basil Hall's Experiments--Ventilation of Lighthouses 110

SMEATON AND LIGHTHOUSES.