This combination has provided the lighthouse engineer with a new, powerful, and efficient means of overcoming abnormal difficulties. Many a rock, reef, or stretch of uninhabited coastline has demanded indication, but has defied such protection from motives of cost, inaccessibility, or searching problems concerning the accommodation and relief of the keepers. As I have shown in the course of this volume, the erection of a first-class lighthouse is a costly undertaking, and the shipping interests, which in the case of Great Britain and a few other countries are called upon to pay the bill, naturally demur, unless the rock or other obstacle is situate in the centre of the marine thoroughfare, or the approach to a pitiless coast is extremely hazardous, when the erection of the tower becomes absolutely imperative. If one were to add up the costs of all the great lights scattered throughout the seven seas, it would be found that several millions sterling had been sunk in this humane effort, and yet, relatively speaking, but a small area of danger in the aggregate is safeguarded. [Illustration: THE PLATTE FOUGÈRE LIGHTHOUSE UNDER CONSTRUCTION. This automatic light marks a dangerous reef, off the Guernsey coast, which is familiar to readers of Victor Hugo’s “Toilers of the Sea.”] Then the human factor demands consideration. A colony of four or six men scarcely could be found willing to suffer isolation from the world at large and to be deprived of intercourse with their fellow-beings in the interests of shipping, say, through the Straits of Magellan, around Cape Horn, among the icy fastnesses of the Northern Labrador coast, or in Hudson Bay. Life in the lighthouses which guard the busy steamship lanes is monotonous and nerve-shattering enough, but to maroon men in such remote places as those mentioned above would be to promote a wholesale rush of inmates for the lunatic asylums.