In silence, then, the party commenced the tedious ascent of the mound by the narrow path to the top, until at some hundred and twenty feet above the surrounding plain they found themselves actually under the wall of the mighty building. The donkeys were made fast.
"Sime and I," said Dr. Cairn quietly, "will enter the pyramid."
"But—" interrupted his son.
"Apart from the fatigue of the operation," continued the doctor, "the temperature in the lower part of the pyramid is so tremendous, and the air so bad, that in your present state of health it would be absurd for you to attempt it. Apart from which there is a possibly more important task to be undertaken here, outside."
He turned his eyes upon Sime, who was listening intently, then continued:
"Whilst we are penetrating to the interior by means of the sloping passage on the north side, Ali Mohammed and yourself must mount guard on the south side."
"What for?" said Sime rapidly.
"For the reason," replied Dr. Cairn, "that there is an entrance on to the first stage—"
"But the first stage is nearly seventy feet above us. Even assuming that there were an entrance there—which I doubt—escape by that means would be impossible. No one could climb down the face of the pyramid from above; no one has ever succeeded in climbing up. For the purpose of surveying the pyramid a scaffold had to be erected. Its sides are quite unscaleable."
"That may be," agreed Dr. Cairn; "but, nevertheless, I have my reasons for placing a guard over the south side. If anything appears upon the stage above, Rob—anything—shoot, and shoot straight!"