MUNN & CO., Publishers, 361 Broadway, New York, N. Y. * * * * * Useful Engineering Books Manufacturers, Agriculturists, Chemists, Engineers, Mechanics, Builders, men of leisure, and professional men, of all classes, need good books in the line of their respective callings. Our post office department permits the transmission of books through the mails at very small cost. A comprehensive catalogue of useful books by different authors, on more than fifty different subjects, has recently been published, for free circulation, at the office of this paper. Subjects classified with names of author. Persons desiring a copy have only to ask for it, and it will be mailed to them. Address, MUNN & CO., 361 Broadway, New York. * * * * * PATENTS. In connection with the =Scientific American=, Messrs. MUNN & CO. are solicitors of American and Foreign Patents, have had 42 years' experience, and now have the largest establishment in the world. Patents are obtained on the best terms. A special notice is made in the =Scientific American= of all inventions patented through this Agency, with the name and residence of the Patentee. By the immense circulation thus given, public attention is directed to the merits of the new patent, and sales or introduction often easily effected. Any person who has made a new discovery or invention can ascertain, free of charge, whether a patent can probably be obtained, by writing to MUNN & CO. We also send free our Hand Book about the Patent Laws, Patents, Caveats, Trade Marks, their costs, and how procured. Address MUNN & CO., 361 Broadway, New York. Branch Office, 622 and 624 F St., Washington, D. C. * * * * * Transcriber's Amendments Transcriber's Note: Some illustrations may have been moved. We have rendered consistent on a per-word-pair basis the hyphenation or spacing of such pairs when repeated in the same grammatical context. The table of contents has been moved to the front. Other changes are listed below. The listed source publication page number also applies in this reproduction except for the table of contents since it has been moved. Page Change