Under his direction, the crew turned the ship in its course until it was headed for the point in space where Damis planned to intercept the red planet. With the course set to his satisfaction, he gave orders for the stern motors to be operated at such a power as to give the highest acceleration consistent with comfort for the crew. There were no windows in the ship but two observers seated at instruments kept the entire heavens under constant observation. Damis motioned one of them to stand aside and told Lura to take his place. She sat down before a box in which were set two lenses, eye-distance apart. She looked through the lenses and gave a cry of astonishment. Before her appeared the heavens in miniature with the entire galaxy of stars displayed to her gaze. In the center of the screen was a large disk thickly marked with pocks. "The moon," explained Damis. "We are headed directly toward it now but we'll shift and go around it. We'll pass only a few hundred miles from its surface, but unfortunately it will be between us and the sun and you'll be able to see nothing. Look in the other observer." * * * * * Lura turned to the second instrument. A large part of the hemisphere was blotted out by the Earth which was still only a few thousand miles away. The sun showed to one side of the Earth, but a movable disk was arranged in the instrument by means of which it could be shut off from the gaze of the observer. Despite the presence of the sun, the stars shone brilliantly in the intense black of space. "How fast are we traveling?" asked Lura. "It is impossible to tell exactly," he replied. "I can approximate our speed by a study of the power consumed in our stern motors and again I can approximate it by a series of celestial observations, provided we do not have to change our course while I am doing so." "Isn't there some sort of an instrument which will tell you how fast we are going?" she asked in astonishment. "Unfortunately not. We are traveling through no medium which is dense enough to register on an instrument. Our course is not straight, but is necessarily an erratic one as we are subject to the gravimetric pull of all of the celestial bodies. Just now the Earth supplies most of the pull on us but as soon as we approach the moon, we will tend to fall on it and frequent sideblasts will be needed to keep us away from it. Once we get up some speed that is comparable with light, we can measure by direct comparison, but our speed is too low for that now." "I saw you lay out your course, but how are we steering?" "The observer who works on the front instrument keeps a cross hair on a fixed star. When the curving of the ship deviates us more than five degrees from our course, a side motor is turned on until we straighten out again. It is quite a simple matter and I'll take the ship myself when we near Mars. There is no need to be frightened."