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Until 1910 the Patent Office permitted an inventor to file an official notice, or caveat, that he was working on a particular invention. If another individual subsequently filed a patent application for a similar invention, the first inventor was so notified. He was then given the opportunity to file his own patent application, which would be put in interference with the earlier application to establish priority. A caveat was valid for one year and could be renewed from year to year upon payment of a fee ($10 in 1875).

There are few caveat materials at the Edison National Historical Park for the 1870s. In addition to the documents presented in this series, there are also copies of caveats in the Document File and in other series. Fourteen caveats relating to electric lighting and the telephone can be found in Experimental Researches, Vol 5. An extensive collection of caveats for this period can be found at the National Archives in Record Group 241, Records of the Patent and Trademark Office.

Courtesy of Thomas Edison National Historical Park.