Our march to-day had been twenty-one miles, and the astronomical observations gave us a chronometric longitude of 98 deg. 22' 12", and latitude 40 deg. 26' 50". We were moving forward at seven in the morning, and in about five miles reached a fork of the Blue, where the road leaves that river, and crosses over to the Platte. No water was to be found on the dividing ridge, and the casks were filled, and the animals here allowed a short repose. The road led across a high and level prairie ridge, where were but few plants, and those principally thistle, (_carduus leucographus_,) and a kind of dwarf artemisia. Antelope were seen frequently during the morning, which was very stormy. Squalls of rain, with thunder and lightning, were around us in every direction; and while we were enveloped in one of them, a flash, which seemed to scorch our eyes as it passed, struck in the prairie within a few hundred feet, sending up a column of dust. Crossing on the way several Pawnee roads to the Arkansas, we reached, in about twenty-one miles from our halt on the Blue, what is called the coast of the Nebraska, or Platte river. This had seemed in the distance a range of high and broken hills; but on a nearer approach was found to be elevations of forty to sixty feet into which the wind had worked the sand. They were covered with the usual fine grasses of the country, and bordered the eastern side of the ridge on a breadth of about two miles. Change of soil and country appeared here to have produced some change in the vegetation. _Cacti_ were numerous, and all the plants of the region appeared to flourish among the warm hills. Among them the _amorpha_, in full bloom, was remarkable for its large and luxuriant purple clusters. From the foot of the coast, a distance of two miles across the level bottom brought us to our encampment on the shore of the river, about twenty miles below the head of Grand Island, which lay extended before us, covered with dense and heavy woods. From the mouth of the Kansas, according to our reckoning, we had traveled three hundred and twenty-eight miles; and the geological formation of the country we had passed over consisted of lime and sand stone, covered by the same erratic deposits of sand and gravel which forms the surface rock of the prairies between the Missouri and Mississippi rivers. Except in some occasional limestone boulders, I had met with no fossils. The elevation of the Platte valley above the sea is here about two thousand feet. The astronomical observations of the night placed us in longitude 98 deg. 45' 49", latitude 40 deg. 41' 06".