Grayton PREFACE. www THE Indexes to Patents are now so numerous and costly as to render their purchase inconvenient to a large number of inventors and others, to whom they have become indispensable. To obviate this difficulty, short abstracts or abridgments of the Specifications of Patents under each head of Invention have been prepared for publication separately, and so arranged as to form at once a Chronological, Alphabetical, Subject-matter, and Reference Index to the class to which they relate. As these publications do not supersede the necessity for consulting the Specifications, the prices at which the printed copies of the latter are sold have been added. The number of Specifications from the earliest period to the end of the year 1866 amounts to 59,222. A large proportion of the Specifications enrolled under the old law, previous to 1852, embrace several distinct inventions, and many of those filed under the new law of 1852 indicate various applications of the single invention to which the Patent is limited. Considering, therefore, the large number of inventions and applications of inventions to be separately dealt with, it cannot be doubted that several properly belonging to the group which forms the subject of this volume have been overlooked. In the progress of the whole work such omissions will, from time to time, become apparent, and be supplied in second or supplemental editions. EL. This volume is a continuation of the "Abridgments of "Specifications relating to Electricity and Magnetism, "their Generation and Applications," already published, and brings the Abridgments to the end of the year 1866. From that date the Abridgments have not been published in classes, but will be found in chronological order in the quarterly volumes of the "Chronological and Descriptive Index" (see List of Works at the end of this book). It is intended, however, to publish these Abridgments in classes as soon as the Abridgments of all the Specifications from the earliest period to the end of 1866 have appeared in a classified form. Until that takes place, the reader (by the aid of the Subject-matter Index for each year) can continue his examination of the Abridgments relating to the subject of his search in the Chronological and Descriptive Index. The rules for including inventions in this series, and the method of making abridgments therein, are the same as those adopted in the preceding volume; and in regard to the scientific terms used, the same care has been taken to preserve uniformity and correctness. This series contains some inventions that relate to the protection of ship's bottoms from fouling and from corrosion. In cases where electric force is prevented in order to ensure non-corrosion, the invention is not included ; but when, by means of the corrosion, or slow and equable oxidation of a conductor of electricity-such as zinc-electric force is called into action and the corrosion of the ship's bottom is thereby obviated, the invention is included in the present series. The Abridgments marked thus (**) in the following pages were prepared for another series or class, and have been transferred therefrom to this volume. October, 1870. B. WOODCROFT. |