A couple of lazy weeks passed by rapidly, lazy because the Westerner insisted on doing all the work that needed to be done, and before they were over Roger found that he had nearly regained his full strength, his wiry frame recuperating without loss of vitality. Masseth, on his return, was much gratified to find how well the boy had got along, and the following week he took him alone to one of the most prominent stations on the northern side. "Now, Roger," Masseth said to him, "I've just about finished what I want to do on this side, so I'm going across to run a level on the other side. But I'm very anxious to get a clear sight of this peak, where we're standing, for an extensive triangulation, in order to correct or rather verify some results. The only way in which this can be done is to flash a heliograph message to me, at a certain time on a certain day, in the way I showed you last week." "Across seven miles?" asked the boy in amazement. "More than that," said his chief, smiling. "Now here is the way you had better get at it. In this box, which you see has been securely fastened to the rock, are two pieces of tin, one with a quarter of an inch hole in it, the other with a hole an inch square. They point, with mathematical correctness, to a peak on the other side, which is an old station, and easily seen. If you look through, you can see the place." Roger bent down, and looking through the aperture was able to determine a slight projection on the far distant bank, which he described and which was in verity the point sought. "Now," continued Masseth, "two months hence, or to be more exact, sixty days from now, at eight o'clock in the morning, I will be waiting at that point on the other side, and I shall expect you to be here. Over the further piece of tin, as you see, I have hung a cloth, which you can drop while you are testing the glass. In this movable frame, so devised that it can be screwed up or down, or shifted slightly sideways, arrange the glass so that the reflection of it, shining through the larger hole, appears at an equal distance on all sides of the smaller opening. You understand me?" "Quite, Mr. Masseth," answered the boy, who had been listening with all his ears. "Very well," the older man continued. "At eight o'clock sharp, then, you will raise quickly the curtain in front of the smaller hole, and drop it again, doing this three times, allowing the hole to remain open for ten seconds each time. Do that every five minutes for half an hour, or six times in all, to allow for any possible variation of time in your watch. By the way, you had better have two watches in the event of one of them stopping or the hands catching, or something of that sort, because a month's work will depend on getting that signal. But I think I can trust you." "You can, indeed, Mr. Masseth," said Roger. "But what shall I be doing during those two months? Am I to remain alone in camp?"