As we got farther among the sand dunes we found them all sizes and shapes, though usually circular, and from fifteen to forty feet high. Of course the surface of this country was very irregular, and there would be places here and there where the grass had obtained a little footing and the sand had not drifted up. There were also some hills which seemed to be independent of the sand piles. We stopped for noon on a little flat where there was some struggling grass. This flat ran off to the north, and narrowed into a small valley through which in the spring probably a little water flowed. We had finished dinner when we noticed a flock of big birds circling about the little valley, and, on looking closer, saw that some of them were on the ground. "They are sand-hill cranes," said Jack. "I've seen them in Dakota, but this must be their home." They were immense birds, white and gray, and with very long legs. Jack took his rifle and tried to creep up on them, but they were too shy, and soared away to the south. [Illustration: OUR FIRST CAMP IN THE SAND HILLS.] We soon passed the first station on the railroad, called Crookston. The telegraph-operator came out and looked at us, admitted that it was a sandy neighborhood, and went back in. We toiled on without any incident of note during the whole afternoon. Toward night we passed another station, called Georgia, and the man in charge allowed us to fill our kegs from the water-tank. We went on three or four miles and stopped beside the trail, and a hundred yards from the railroad, for the night. The great drifts of sand were all around us, and no desert could have been lonelier. We had a little wood and built a camp fire. The evening was still and there was not a sound. Even the blacksmith's pet, wandering about seeking what he could devour, and finding nothing, made scarcely a sound in the soft sand. The moon was shining, and it was warm as any summer evening. Jack sat on the ground beside the wagon and played the banjo for half an hour. After a while we walked over to the railroad. We could hear a faint rumble, and concluded that a train was approaching. "Let's wait for it," proposed Jack. "It will be along in a moment." We waited and listened. Then we distinctly heard the whistle of a locomotive, and the faint roar gradually ceased. "It's stopped somewhere," I said. "Don't see what it should stop around here for," said Jack. "Unless to take on a sand-hill crane." Then we heard it start up, run a short distance, and again stop; this it repeated half a dozen times, and then after a pause it settled down to a long steady roar again. "It isn't possible, is it, that that train has been stopped at the next station west of here?" I said. "The next station is Cody, and it's a dozen miles from here," answered Jack. "It doesn't seem as if we could hear it so far, but we'll time it and see."