And so it came about that it was the gold-seeker who finally revealed the well-kept secret of the Yellowstone. Itself destitute of mineral wealth, this region could not escape the ubiquitous prospector. It was not, indeed, by him that it was publicly proclaimed to the world. He cared little for any country that was destitute of "color" or "pay." But the hints he dropped put others on the track and opened the door to real discovery. This fact of long delay in the discovery of the Upper Yellowstone is the most important in its history. Had it been known at an earlier date, its fate would have been deplorably different. The period of the fur traders was too early for the interest of the people to demand, or the power of the government to enforce, its protection. If Captain Raynolds had discovered it, all its most valuable tracts would have been preempted long before the government would have been able to give it attention. Fortunately, the discovery was delayed until there was a considerable population in the country near by, and the government was prepared actively to consider the matter. Before settlers could establish a permanent foothold, the Park was created, and all the vexatious obstacles, which might otherwise have defeated the project, were avoided. CHAPTER XII. LATER EXPLORATIONS. As soon as the remarkable character of the country about the sources of the Yellowstone became generally known, there was a rush of explorers to its borders. Every expedition that could possibly extend the field of its labors in that direction did so, and there was scarcely a summer during the next twenty years that the Park was not the scene of some official exploration or visit. By far the most important of these were the various expeditions under the United States Geological Survey. Dr. Hayden was again in the country with two parties in 1872, and very widely extended the range of observations of the previous year. In 1878, survey parties again entered the Park and resumed work there on a much more minute and extensive scale. The result of that year's explorations appeared in 1883 in the form of an elaborate report by Dr. Hayden and his co-workers, which entered with much detail into the more important subjects of scientific interest. It was embellished with a great number of engravings and colored plates, and with an exhaustive series of topographical and geological maps. The work was again taken up in 1883, and was continued for several years. All questions of scientific importance were investigated more thoroughly than ever before, and many valuable official reports and monographs, together with a superb map, have been the result.