What subjects-matter are properly within the domain of patent law and what is neces sary to constitute a patentable invention or discovery, are important questions. As to the first the language of the statute provides for the granting of patents to the inventor " of any new useful art, machine, manufacture, or composition of matter, or any new and useful improvement thereof." Time term manufnetnre is construed in a more limited sense than-in the patent laws of most foreign countries, as it is used exclusive of machin ery and compositions. Under the head of "art" are included all patentable processes, or methods. Xis often difficult to tell within which classification a specified invention properly falls, but it is sufficient that its nature is such as to bring it within the limits of one or more of the four classes. Every discovery does not entitle the discoverer to an invention. Thus a mere enunciation of a scientific abstract principle, or philo sophical truth, is not patentable. But if such principle be so reduced to a practicable and tangible form, so as to be a concrete construction of component parts, or structure capable of producing useful results, this will be patentable. It is not necessary that all parts of the invention be new, but what is new must produce some tangible useful effect or improvement. Where two or more existing processes or parts of machinery are for the first time united, if a new effect be produced, the combination is patentable; other • wise not. No invention injurious to public morality, or which would assist crime, can be patented. But an invention of a process or tool which would be useful in legitimate business cannot be rejected on the ground that it might also be of aid to burglars or counterfeiters. That which is useful is also to be distinguished front that which is trivial or frivolous, but a glance at the patent office models will quickly dispel any fear that undue severity is exercised on this point. "Double use" is not patentable, that is, a new use of a process or machine already in use for a different purpose, is not considered a new invention. A mere substitution of one substance or element (or, in a process, of a chemical ingredient) will not be considered, if the two have the samo function only. A patentable process is one which by the application of some principle or natural law, such as the application of one form of !natter to another, or by chemical, action, produces some new and useful effect. Important instances are the patented processes used in manufactur ing vulcanized india-rubber, in smelting ores, and in making high grades of steel. Au aban
donment by an inventor may be inferred from his neglecting to make objectio" to the use of his invention by unauthorized parties within his knowledge, or from unreasona ble delay in making application after the completion of the invention. If the utter be in public use for two years before the time of application the inventor's claiin is abso lutely forfeited. To constitute such public use it is necessary to show only a single instance. When a patent has been granted and application is made by a second person, claiming priority of invention, it is too late for the "interference" investigation by the patent office, and the only course for the commissioner to pursue is to grant a second patent to the applicant, if he feel warranted by the facts, and thus laave the parties to contest their rights on an equal footing in the courts.
Patents are the subject of sale in whole or in part, and may be mortgaged orassigned. Such assignment must be recorded at the patent office to protect the assignee against a vendee or mortgagee claiming through the original patentee. Licenses to use art inven tion may be written or oral, but cannot be assigned to a third party without special authority. A contract to sell or assign an invention not yet patented is a good executory contract, but actual sale or assignment is null. To constitute infringement of a patent there must be the making, use, Or sale to another of that which is the subject matter of an existing patent. The test is whether the two are not substantially identical. Changes in form, relative position, or substitution of one material for another, will not save an infringer from the penalties attached to infringement. Damages may be recov ered by the patentee in an action on the casein courts of common law, or by equity pro ceedings. In the former method the measure of damage is the actual damage incurred; in the latter the infringer may be compelled to account for the profits received by him, and a temporary or permanent injunction may be obtained. Notice must be given of the patentee's right by marking the article with the word "patented " and the date of issue. Penalties are provided for the wrongful use of such mark or stamp. The best work on patents in this country is that of George Ticknor Curtis; Phillips aud Fessenden are also standard authors. The latest English workis that of Agnew.