The descriptions of abandoned works are not all printed in small type. If this rule is adopted in the directory, it should be uniformly adhered to. The maps accompanying the directory, which were made by the photolithographic process, are all on too small a scale, and consequently lack clearness. The colored lithographs, which exhibit the anthracite furnaces of Pennsylvania and the iron works of the region east of the Hudson River, are altogether the best illustrations in the book. An elaborate discussion of iron as a chemical element occupies another division of the book. Its purpose is to instruct the iron master in the chemical properties and relations of the metal with which he deals; and to this end it should be clear, concise, and definite, and, leaving all disputed points, should explain the known and well-determined characteristics of iron and its compounds with other elements. Mr. Lesley, the compiler of the book, distinctly states in the Preface that he is no chemist, and we are therefore prepared to meet the occasional inaccuracies observable in this chemical portion of the "Guide." It lacks condensation and system; matters of very little moment receive disproportionate attention; and pages are filled with discussions of nice points of chemical science still in dispute among professed chemists, and wholly out of place in what should be a brief elementary treatise on the known properties of iron. If these questions in dispute were such as the practical experience of the iron-master might settle, or, indeed, throw any light upon, there would be an obvious propriety in stating the points at issue; but if the question concerns the best chemical name for iron-rust, or the largest possible per cent. of carbon in steel, the practical metallurgist should not be perplexed with problems in analytical chemistry which the best chemists have not yet solved. Valuable space is occasionally occupied by the too rhetorical statement of matters which would have been better presented in a simpler way; thus, the fervid description of oxygen, however appropriate in Faraday's admirable lectures before the Royal Institution, is out of place in the "Iron-Manufacturer's Guide." We must also enter an earnest protest against the importation, upon any terms, of such words as "ironoxydulcarbonate," "ironoxydhydrate," and the adjective "anhydrate." Some descriptions of considerable imaginative power have found place even in the directory of works. From the description of the Allentown furnaces we learn, with some surprise, that "no finer object of art invites the artist"; and again, "that the _repose_ of bygone _centuries_ seems to sit upon its immense walls, while the roaring _energy_ of the present day fills it with a truer and better life than the revelry of Kenilworth or the chivalry of Heidelberg." The average age of the Allentown works subsequently appears to be nine years.