For a work of such scope as wthis, the first word of the author should be an apology for what is doubtless the too ffambitious effort of a single writer. A quarter of a century in the high tide of the arts and sciences, an ardent interest in all things that make for scientific progress, and the aid and encouragement of many friends in and about the Patent ffThOffice, furnish the explanation. The work cannot claim the authority of a text-book, the fullness of a history, nor the exactness of a technical treat