The Missouri, taken in connection with the Mississippi, is the longest river in the world, its length from the highest navigable stream to the Gulf of Mexico being four thousand four hundred and ninety-one miles, and its length to its junction with the Mississippi, three thousand and ninety-six miles. Add to this the immense distance not navigable because of the cataracts and falls, next to Niagara the grandest on this globe, and reaching to the Rocky Mountains, and some idea may be formed of the great extent of this river. The entrance of the Yellow-Stone is nearly two thousand miles above its mouth. A journey of one thousand miles up the Missouri a century or more since, while it was an undertaking of no slight magnitude and attended with many hardships and dangers, did not bring the traveller over more than one-fourth of its length. The course pursued by Griffith and his companions can be marked out with singular accuracy by the use of subsequent knowledge, obtained during the last one hundred years, respecting the country that river traverses. He speaks of finding lead-mines. The lead-mines of Missouri are extremely valuable, and yield millions of pounds annually. He speaks of salt springs. The line of his journey conducted him by the salt licks of Nebraska, which, when the springs are low and evaporation is rapid, have the appearance of layers of snow. He speaks of white mountains. Passing from the broad open prairies to the uplands and mountains, the soil is sandy and in many places remarkably white. The writer himself has often seen on the Missouri bold projections of limestone which in the distance appeared like banks of snow. He speaks of the Indians being all white. This presents a difficulty not easily reconcilable with the intermixture theory. The predominating color, it would be supposed, was that of the red race. But he partially explains this by saying that "they intermixed with no other people by marriage: there was not a dark-skinned man in the nation." Could they without intermixture have increased to such considerable numbers as to be able, as he supposes, to put into the field "fifty thousand men capable of bearing arms"? It need not be thought impossible, but it certainly is improbable. At any rate, this people were sufficiently white to be called, by Griffith and by a large number of reliable witnesses, "White Padoucas," "White Panis," "White Indians." He speaks of their having no records and no horses. In this respect his recital differs somewhat from those given by others, some of whom assert that they saw some old manuscript books, and that they had horses for the chase. His statement, however, offers no contradiction to that made by others, because it is pretty certain that many of them came upon different branches of the same extensive nation.