On examining our treasure, we found it to be a pile of manuscripts, of letter-paper size and three inches thick, with printed scraps from newspapers and pamphlets interspersed. All was in the loosest state of disorder; but we strung the leaves together, paged them, and made an index of their contents. The book thus extemporized has been our companion, as the reader will see, in the ensuing history. The number of its pages is seven hundred and forty-seven. The index has the names of sixty-nine Associative experiments, beginning with Brook Farm and ending with the Shakers. The memoirs are of various lengths, from a mere mention to a narrative of nearly a hundred pages. Among them are notices of leading Socialists, such as Owen, Fourier, Frances Wright, &c. The collection was in no fit condition for publication; but it marked out a path for us, and gave us a mass of material that has been very serviceable, and probably could not elsewhere be found. The breadth and thoroughness of Macdonald's intention will be seen in the following circular which, in the prosecution of his enterprise, he sent to many leading Socialists. PRINTED LETTER OF INQUIRY. "_New York, March, 1851._ "I have been for some time engaged in collecting the necessary materials for a book, to be entitled '_The Communities of the United States_,' in which I propose giving a brief account of all the social and co-operative experiments that have been made in this country--their origin, principles, and progress; and, particularly, the causes of their success or failure. "I have reason to believe, from long experience among social reformers, that such a work is needed, and will be both useful and interesting. It will serve as a guide to all future experiments, showing what has already been done; like a light-house, pointing to the rocks on which so many have been wrecked, or to the haven in which the few have found rest. It will give facts and statistics to be depended upon, gathered from the most authentic sources, and forming a collection of interesting narratives. It will show the errors of enthusiasts, and the triumphs of the cool-thinking; the disappointments of the sanguine, and the dear-bought experience of many social adventurers. It will give mankind an idea of the labor of body and mind that has been expended to realize a better state of society; to substitute a social and co-operative state for a competitive one; a system of harmony, for one of discord.