The strange error he twice commits in imagining that there were vaults under the pyramid of Kheops in an island formed by a canal which the builder had introduced from the Nile is due to the same cause. Doubtless his dragoman had told him something of the kind. A subterraneous chamber in the rock actually exists under the great pyramid, as was discovered by Caviglia, and there are pyramids into whose lower chambers the Nile has long since infiltrated. Professor Maspero found his exploration of the pyramids of Lisht, south of Dahshûr, stopped by the water which had filled them, and Professor Petrie had the same experience in the brick pyramid of Howâra, though here the infiltration of the water seems to have been caused by a canal dug in Arab times. But the pyramids of Gizeh stand on a plateau of limestone rock secure against the approach of water, and the story reported by Herodotos is more probably the result of misapprehension on his own part than of intentional falsehood on the part of his guides. His ready credence of it, however, can be explained only by the condition of the country at the time of his visit. The whole land was covered with water, and in going to Memphis he had to sail by the pyramids themselves. It was in a boat that his visit to them must have been made; and it was easy, therefore, to believe that a canal ran from the water on which he sailed through the tunnelled rock whereon they stood. He did not know that the lowest chamber of the pyramid was high above the utmost level of the flood. Surprise has often been expressed that Herodotos should make no mention of the Sphinx, which to Arabs and modern Europeans alike has appeared one of most noteworthy monuments of Gizeh. But in sailing along the canal which led from Memphis to the pyramids he would have passed by it without notice. As his boat made its way to the rocky edge on which the huge sepulchres of Kheops and Khephren are built, it would have been concealed from his view; and buried as it was in sand his guides did not think it an object of such surpassing importance as to lead him to it over the burning sand. In the immediate neighbourhood of the great pyramid he was surrounded by monuments more interesting and more striking, which were quite enough to occupy his day and satisfy his curiosity.