[The first paragraph of this note covers all of the Caveats in Record Group 241.]
Until 1910 the U.S. Patent Office permitted an inventor to file caveats, which were official notices regarding work in progress. Caveats were valid for one year and were renewable for an annual fee. If another inventor subsequently filed an application for a similar invention, the Patent Office notified the original inventor. These Edison caveats, which cover the years 1872-1891, relate to telegraphy, electric pens, telephones, electric light and power, phonographs, iron ore separation, and other topics. They contain detailed notes, drawings, and specifications regarding each invention.
Two versions of Caveat 45 are presented in this edition. Edison began drafting this caveat at the beginning of August 1873 to record his priority of invention while still experimentally testing his concept. Portions of the caveat were subsequently revised and the second version was signed on October 28, 1873, although it was not filed in the U.S. Patent Office until the summer of 1874. A printed copy of the final version appears as an exhibit in the patent interference case, Edison v. Nicholson. The earlier version, although not part of the printed record, can also be found in the case file for Edison v. Nicholson in the Patent Interference Records at the National Archives.