THE United States of America have certainly done noble work in the exploration and mapping of their vast empire. Most of the long-settled States have for many years possessed elaborate maps and reports upon the topography, geology, and agricultural features of their territory. The central Government has likewise carried on extensive and admirable coast surveys, besides innumerable expeditions and surveys for opening up the less known or wholly unvisited regions of the interior of the continent. Were all the literature connected with this subject gathered together it would be found to form of itself a goodly library. Some of it has been published in most costly and indeed luxurious style; other portions, and these sometimes not the least interesting or valuable, have to be unearthed from the pages of flimsily printed “blue-books” But whatever be their external guise, these narratives are pervaded by an earnestness and enthusiasm, a consciousness of the magnitude of the scale on which the phenomena have been produced, and yet a restrained style of quiet description, which cannot but strike the reader. Their writers have evidently had their feelings of awe and admiration worked sometimes up to the highest pitch, yet they contrive on the whole to present just such plain frank statements of facts as to convey clear and definite notions of the regions they describe. Though little is said about hardships and hair-breadth escapes, one can see that these bold explorers could not have accomplished what they so modestly and quietly narrate without a vast amount of privation and danger. Some of them, indeed, like poor young Loring in 1871, have lost their lives by Indian assassins, others have fallen victims to the disease and debility necessarily attendant on so much exposure. But on the whole the work seems to be healthy, and the men engaged upon it like it and keep to it.