The stop-cocks were opened, the reservoirs filled, and the _Nautilus_, slowly sinking, disappeared beneath the surface of the lake. But the colonists were yet able to follow its descent through the waves. The powerful light it gave forth lighted up the translucent water, while the cavern became gradually obscure. At length this vast effusion of electric light faded away, and soon after the _Nautilus_, now the tomb of Captain Nemo, reposed in its ocean bed. CHAPTER EIGHTEEN. REFLECTIONS OF THE COLONISTS--THEIR LABOURS OF RECONSTRUCTION RESUMED-- THE 1ST OF JANUARY 1869--A CLOUD OVER THE SUMMIT OF THE VOLCANO--FIRST WARNINGS OF AN ERUPTION--AYRTON AND CYRUS HARDING AT THE CORRAL-- EXPLORATION OF THE DAKKAR GROTTO--WHAT CAPTAIN NEMO HAD CONFIDED TO THE ENGINEER. At break of day the colonists regained in silence the entrance of the cavern, to which they gave the name of "Dakkar Grotto," in memory of Captain Nemo. It was now low-water, and they passed without difficulty under the arcade, washed on the right by the sea. The canoe was left here, carefully protected from the waves. As an excess of precaution, Pencroft, Neb, and Ayrton drew it up on a little beach which bordered one of the sides of the grotto, in a spot where it could run no risk of harm. The storm had ceased during the night. The last low mutterings of the thunder died away in the west. Rain fell no longer, but the sky was yet obscured by clouds. On the whole, this month of October, the first of the southern spring, was not ushered in by satisfactory tokens, and the wind had a tendency to shift from one point of the compass to another, which rendered it impossible to count upon settled weather. Cyrus Harding and his companions, on leaving Dakkar Grotto, had taken the road to the corral. On their way Neb and Herbert were careful to preserve the wire which had been laid down by the captain between the corral and the grotto, and which might at a future time be of service. The colonists spoke but little on the road. The various incidents of the night of the 15th October had left a profound impression on their minds. The unknown being whose influence had so effectually protected them, the man whom their imagination had endowed with supernatural powers, Captain Nemo, was no more. His _Nautilus_ and he were buried in the depths of the abyss. To each one of them their existence seemed even more isolated than before. They had been accustomed to count upon the intervention of that power which existed no longer, and Gideon Spilett, and even Cyrus Harding, could not escape this impression. Thus they maintained a profound silence during their journey to the corral. Towards nine in the morning the colonists arrived at Granite House.