“Located higher up on the side of the hill not far from the Grotto, is the most remarkable mud-spring we have ever seen in the West. It may not improbably be called the Giants Cauldron. It does not boil with an impulse like most of the mud-springs, but with a constant roar which shakes the ground for a considerable distance, and may be heard for half a mile. All the indications around this most remarkable cauldron show it has broken out at a recent period....” Examining the mud-springs and geysers was hazardous business and could be a painful experience, as Hayden discovered: “The entire surface is perfectly bare of vegetation and hot, yielding in many places to slight pressure. I attempted to walk among these simmering vents, and broke through to my knees, covering myself with hot mud, to my great pain and subsequent inconvenience.” [Illustration: Boiling Mud Springs at Crater Hills near Sulphur Springs.] Finally, the expedition reached Yellowstone Lake, the focal point of their exploration, causing Hayden to remark: “On the 28th of July we arrived at the Lake, and pitched our camp on the northeast shore, in a beautiful grassy meadow or opening among the dense pines. The lake lay before us, a vast sheet of quiet water, of a most delicate ultramarine hue, one of the most beautiful scenes I have ever beheld. The entire party was filled with enthusiasm. The great object of our labors has been reached, and we were amply paid for all our toils. Such a vision is worth a lifetime, and only one of such marvelous beauty will ever greet human eye. From whatever point of view one may behold it, it presents a unique picture.” [Illustration: The Head of Yellowstone Lake.] Hayden’s party split into groups, with some continuing to explore the perimeter of the lake, while Hayden, Schoenborn and other members of the expedition went on toward the Firehole Geyser Basin. Eventually, the entire party arrived back at Boetler’s Ranch, having spent 38 days in the wilderness. The most important product of the expedition, in addition to Jackson’s photos, was a 500-page report by Hayden documenting findings of his party. Hayden presented this report and photos to Senators, Congressmen, his superiors in the Interior Department and nearly anyone else who could possibly influence the founding of a park. He also wrote articles in magazines with national circulation, and spent much personal time and effort in trying to convince Congress to establish the park.