Applications for United States patents must be addressed to the Commissioner of Patents, Washington, D.C., and signed and sworn to by the inventor. The invention must not have been in public use or on sale for more than two years prior to the application. The applicant must fully describe his invention and distinctly claim those parts which he believes to be new. The application must be illustrated with drawings when possible. When filed, a first fee of $15 is payable, and a second fee of $20 is exacted if the application is allowed before the patent will be issued. The patent runs seventeen years from date of issue. Extensions can be obtained only by special act of Congress. A pamphlet of rules and forms is distributed free by the Commissioner of Patents. Suits to enjoin infringement of letters patent are brought by bill in equity in U. S. District or Circuit courts. The profits realized by an infringer can also be recovered.

The total number of United States Patents granted up to and including Oct. 25, 1892, was 485,158. The average issue is about 25,000 a year. The average number of applications for patents is 40,000 a year. Since 1881, the annual receipts of the Patent Office have exceeded $1,000,000. The figures for fiscal year ending June 30, 1892, were $1,268,727.35. The expenditures for the same year were $1,114,134.23. The total balance to the credit of the Patent Fund in the United States Treasury on June 30, 1892, was $4,102,441.00. The two main items of expense are salaries, about $650,000, and printing and photo-lithographing, about $400,000 annually. The Patent Office Library contains 60,000 volumes. The model hall has 154,000 models. The office does not require models now, except in special cases.