| "The doctor reached the summit with some little difficulty." |
"It has occurred to me," he said to them, "to build a lighthouse at the top of the cone up there."
"A lighthouse?" they cried.
"Yes, a lighthouse; it will be of use to show us our way back at night when we are returning from distant excursions, and to light up the neighborhood in the eight months of winter."
"Certainly," answered Altamont, "such an apparatus would be useful; but how will you build it?"
"With one of the Porpoise's lanterns."
"Very good; but with what will you feed the lamp? With seal-oil?"
"No; it doesn't give a bright enough light; it could hardly pierce the fog."
"Do you think you can get hydrogen from our coal and make illuminating gas?"