This small stream, known as Sulphur Creek, has the honor, or the dishonor if you choose, of being the first desperado of the Yellowstone, but one so much greater than its two petty imitators of human times that there is no comparison of misdeeds. Sulphur Creek stole the lake from the Snake River and used it to create the Yellowstone River, which in turn created the wonderful canyon. Here at last is a crime in which all will agree that the end justified the means. How this piracy was accomplished is written on the rocks; even the former lake outlet into the Snake River is plainly discernible to-day. At the lake's north end, where the seeping waters of Sulphur Creek and the edge of the lake nearly met on opposite sides of what was then the low flat divide, it only required some slight disturbance indirectly volcanic, some unaccustomed rising of lake levels, perhaps merely some special stress of flood or storm to make the connection. Perhaps the creek itself, sapping back in the soft lava soils, unaided found the lake. Connection once made, the mighty body of lake water speedily deepened a channel northward and Sulphur Creek became sure of its posterity. At that time, hidden under the lake's surface, two rhyolite dikes, or upright walls of harder rock, extended crosswise through the lake more than half a mile apart. As the lake-level fell, the nearer of these dikes emerged and divided the waters into two lakes, the upper of which emptied over the dike into the lower. This was the beginning of the Great Fall. And presently, as the Great Fall cut its breach deeper and deeper into the restraining dike, it lowered the upper-lake level until presently the other rhyolite dike emerged from the surface carrying another cataract. And thus began the Upper Fall. Meantime the stream below kept digging deeper the canyon of Sulphur Creek, and there came a time when the lower lake drained wholly away. In its place was left a bottom-land which is now a part of the Hayden Valley, and, running through it, a river. Forthwith this river began scooping, from the Great Fall to Inspiration Point, the scenic ditch which is world-celebrated to-day as the Grand Canyon of the Yellowstone. IV