At times the transformation from three-master to war-ship, or from war-vessel to three-master, takes place before the watcher's eyes, as though some mighty wizard were doing the "Presto, change!" act for the gazer's benefit. Then, very likely, the Buttes lose all resemblance to ocean craft and assume their natural shape, but appear to be surrounded by water--a granite isle in a placid sea. So vivid is this picture that the mountain casts a perfect inverted shadow of itself in the waters which apparently surround it, but which actually do not exist. There are other peaks and mountains which are worthy of mention among the features of the Colorado Desert. One of these is Pilot Knob, and Signal Mountain is another. These two mountains are landmarks which serve to guide those who have occasion to cross the forbidding region. Pilot Knob, in the southeastern part of the desert, is the point toward which eastern-bound travelers shape their course. The peak can be seen more than a hundred miles, and it stands out so distinctly from other mountains in that quarter of the desert that its identity is not easily lost. Signal Mountain rises abruptly from the level plain near the western side of the desert at the international line. It is visible from all points in the desert, and has served to guide many a traveler to safety who otherwise would have perished in the desert wastes. The mountain is pyramidal in form, and is distinctive from all other peaks of that region. Along the eastern rim of the desert stretches a long line of hills two or three hundred feet in height, which are known as the "Walking Hills." They are gray and barren but not lacking in picturesqueness, for many strange and fantastic shapes may be traced in their outlines. These hills are constantly changing both shape and position, and that is the reason they have received the name of Walking Hills. East of these hills run the trains of the Southern Pacific Railroad. The road was built a little more than a quarter of a century ago, and at that time the tracks were from one fourth of a mile to two miles west of the hills. Now the latter are encroaching upon the road and threaten to bury it beneath millions of tons of sand.