Two lines of attack were rapidly rendering impossible the continuance of slavery in the United States. Mrs. Stowe gave effective expression to the moral, religious, and humanitarian sentiment against slavery. In the year in which her work was published, Frederick Law Olmsted began his extended journeys throughout the South. He represents the impartial scientific observer. His books were published during the years 1856, 1857, and 1861. They constitute in their own way an indictment against slavery quite as forcible as that of "Uncle Tom's Cabin," but an indictment that rests chiefly upon the blighting influence of the institution of slavery upon agriculture, manufactures, and the general industrial and social order. The crisis came too soon for these publications to have any marked effect upon the issue. Their appeal was to the deliberate and thoughtful reader, and political control had already drifted into the hands of those who were not deliberate and composed. In 1857, however, there appeared a book which did exert a marked influence upon immediate political issues. There is no evidence that Hinton Rowan Helper, the author of "The Impending Crisis," had any knowledge of the writings of Olmsted; but he was familiar with Northern anti-slavery literature. "I have considered my subject more particularly," he states in his preface, "with reference to its economic aspects as regards the whites--not with reference, except in a very slight degree, to its humanitarian or religious aspects. To the latter side of the question, Northern writers have already done full and timely justice.... Yankee wives have written the most popular anti-slavery literature of the day. Against this I have nothing to say; it is all well enough for women to give the fictions of slavery; men should give the facts." He denies that it had been his purpose to cast unmerited opprobium upon slaveholders; yet a sense of personal injury breathes throughout the pages. If he had no intention of casting unmerited opprobrium upon slaveholders, it is difficult to imagine what language he could have used if he had undertaken to pass the limit of deserved reprobation. In this regard the book is quite in line with the style of Southern utterance against abolitionists. Helper belonged to a slaveholding family, for a hundred years resident in the Carolinas. The dedication is significant. It is to three personal friends from three slave States who at the time were residing in California, in Oregon, and in Washington Territory, "and to the non-slaveholding whites of the South generally, whether at home or abroad." Out of the South had come the inspiration for the religious and humanitarian attack upon slavery. From the same source came the call for relief of the poverty-stricken white victims of the institution.