For three or four miles the road was much like that to which we had been accustomed. Then it gradually began to grow sandier. We were following an old trail which ran near the railroad, sometimes on one side and sometimes on the other; and this was the case all the way through the hills. The railroad was new, having been built only a year or two before. There were stations on it every fifteen or twenty miles, with a side track, and a water-tank for the engines, but not much else.
There was no well-marked boundary to the sand hills, but gradually, and almost before we realized it, we found ourselves surrounded by them. We came to a crossing of the railroad, and in a little cut a few rods away we saw the sand drifted over the rails three or four inches deep, precisely like snow.
"Well," said Jack, "I guess we're in the sand hills at last if we've got where it drifts."
"I wonder if they have to have sand-ploughs on their engines?" said Ollie.
"I've heard that they frequently have to stop and shovel it off," answered Jack.
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.
