That night the weather was so cold that water froze in a basin to a thickness of three-quarters of an inch, and the grass around the camp was stiff with frost, although the month of July was nearly a week old. The boats taken from the cache were now loaded, and the explorers were divided into two bands, one to descend the river by boat and the other to take the same general route on horseback, the objective point being the Yellowstone. The story is taken tip here by the journal in these lines:-- “After breakfast (July 10) the two parties set out, those on shore skirting the eastern side of Jefferson River, through Service (-berry) Valley and over Rattlesnake Mountain, into a beautiful and extensive country, known among the Indians by the name of Hahnahappapchah, or Beaverhead Valley, from the number of those animals to be found in it, and also from the point of land resembling the head of a beaver. It (the valley) extends from Rattlesnake Mountain as low as Frazier’s Creek, and is about fifty miles in length in direct line; while its width varies from ten to fifteen miles, being watered in its whole course by Jefferson River and six different creeks. The valley is open and fertile; besides the innumerable quantities of beaver and otter with which its creeks are supplied, the bushes of the low grounds are a favorite resort for deer; while on the higher parts of the valley are seen scattered groups of antelopes, and still further, on the steep sides of the mountains, are observed many bighorns, which take refuge there from the wolves and bears. At the distance of fifteen miles the two parties stopped to dine; when Captain Clark, finding that the river became wider and deeper, and that the canoes could advance more rapidly than the horses, determined to go himself by water, leaving Sergeant Pryor with six men to bring on the horses. In this way they resumed their journey after dinner, and camped on the eastern side of the river, opposite the head of Three-thousand-mile Island. The beaver were basking in great numbers along the shore; there were also some young wild geese and ducks. The mosquitoes were very troublesome during the day, but after sunset the weather became cool and they disappeared.” Three-thousand-mile Island was so named by the explorers, when they ascended these streams, because it was at a point exactly three thousand miles from the mouth of the Missouri. But no such island exists now; it has probably been worn away by the swift-rushing current of the river. The route of Captain Clark and his party, up to this time had been a few miles west of Bannock City, Montana. As the captain was now to proceed by land to the Yellowstone, again leaving the canoe party, it is well to recall the fact that his route from the Three Forks of the Missouri to the Yellowstone follows pretty nearly the present line of the railroad from Gallatin City to Livingston, by the way of Bozeman Pass. Of this route the journal says:--