Bailey Willis as Chief Geologist spent a week with us in camp, and I saw his genius for drawing in line, and he explained the four-step pacing method. Willis mapped distances by pacing across mountains, counting in his head, while talking at the same time. He compiled in color a geologic map of the United States. His marvellous experiments on mountain folding, his explorations in all the continents and his poetic faith in hydrogen and crystallization as internal forces made his name immortal. N. H. Darton mapped the Great Plains; and his genius was for hard work, long field hours, color photography at its very beginning, and an extraordinary eye for detail in the field. Darton showed me how to find the Chadron Formation on the divides, white clays easily overlooked. Darton’s many years, traversing the entire West, and publishing superb monographs of artesian waters and of immense fossil sea bottoms, summarizing the geology of whole states from Texas to Canada, ranks him among the great geologists. I learned from him detail of infinite discovery possible in every rock ledge. He found tiny fossil shells everyone else had missed. Powell and King had painted impressionistic geology. Darton followed and painted thousands of miniatures, but also combined these into large books. Charles Doolittle Walcott was Director of the U. S. Geological Survey at that time, and no greater geologist ever lived. His Cambrian fossils, those of the first great fossil-making “Mediterranean Sea” of North America, lay buried in the United States from shore to shore. Unswervingly he followed every inland sea of 531 million years ago and thereafter, through advances three times across the continent. Lands were of moderate relief and climates were mild. Marine animals and sea weeds, large and small, were abundant for 80 million years. And remember that a million years is a thousand times the interval since William the Conqueror. The continent Walcott mapped of that ancient time was the North America of today, with sags that let in shallow sea strips and pools where the Cambrian shales and limestones now lie. He wrote a description of that vast history, and all his later summers were spent in the Canadian Rockies, where fossil-bearing strata make the most startling mountain peaks on earth. My Black Hills surveys of 1898 and 1899 were near Deadwood and Spearfish and Mato Tepee, the Devil’s Tower National Monument. In those badlands with weird desert gorges, appear the bones of ancient rhinoceroses and many grotesque animals, huge and tiny, of 40 to 60 million years ago. We found little bones in white earth on the divides still preserved against erosion.