patent; but the independent inventors of separate and independent improvements in the same machine cannot obtain a joint patent for their distinct inventions. To be entitled to a patent as the inventor or discoverer, the claimant must be the real author of the invention; and he is the real author who has conceived the essential plan or principle of the discovery. The inventor may, without prejudice to his rights, receive suggestions, hints, or practical aid from others; and he may avail himself of the practical knowledge or manual skill of others necessary to bring his invention into practical form. Thus Morse conceived the idea of the electric telegraph; and it was held by the supreme court of the United States that the information obtained by him from men of science and mechanicians for the purpose of giving practical embodiment to the conception “neither impairs his rights as an inventor nor detracts from his merits.” But if the principle or plan of the invention is substantially communicated to the patentee, who contributes only the ordinary skill of the constructor or mechanic, he will not be regarded in law as the inventor.—What may be patented. Any “art, machine, manufacture, or composition of matter, or any new and useful improvement thereof,” may be the subject of a patent. By “art” is meant the mode, process, or manner of doing a thing; the term “manufacture” embraces fabrics or substances, but not machinery; and “composition of matter” is usually applied to medicines, and less frequently to compositions used in the arts, as metallic alloys, paints, chemical compounds, &c. A machine must not be a mere function or abstract mode of operation, separate from any particular mechanism, but a function or mode of operation embodied in mechanism designed to accomplish a certain effect. If this effect is new, the mechanism which produces it may be new or old; or a new machine which produces an old effect may be patented. The invention may embrace the entire machine, or one or more parts, or it may consist in a combination which may be entirely of old and well known things, or new ones, or old and new together; but the combination must be new, and must produce a new and useful result, not due to the separate action of any one of the devices used, but to the coöperative action of all. In this case the patent protects only the combination and the new elements; any one may use the old devices either separately or in a different combination. A patent for an improvement covers only the improvement, and does not give to the patentee a right to use the original invention. The improvement of an existing machine must be real and material, and not merely a change of form. The improvement need not be very great. The difference between the old and the new may to all appearance be very slight, and yet be of great importance. Thus, when it was the practice to make cloths water-proof by immersing them in a solution of soap and alum, a patent was obtained for immersing cloths first in a solution of alum (with an ingredient or two added), and afterward in a solution of soap; and this patent was sustained, because it was proved that the immersion into the separate solutions successively made the cloth much more completely and permanently water-proof. Since 1842 the law has provided for issuing patents for designs used in manufactures. In England this class of objects is protected by the law of copyright. By the act of congress of 1870 letters patent may be obtained for any new and original design for a manufacture, bust, statue, alto rilievo, or basso rilievo; or for the printing of woollen, silk, cotton, or other fabrics; any new and original impression, ornament, pattern, print, or picture intended for any article of manufacture; or any new, useful, and original shape or configuration of any article of manufacture. For a statement of what is protected by the law of trade marks see Trade Marks.—The essential requisites of every patentable invention or discovery are novelty and utility. A valid patent will not issue to an applicant if what he claims as new was, before his invention, invented or discovered by another in this country, or if he has abandoned it to the public. Inventors, however, may permit the public use or sale of their inventions for two years before applying for a patent, without prejudicing their rights; but if this use extends over a longer period, or if it amounts to an abandonment, a valid patent will not issue. In regard to a prior invention, it is not sufficient that another may have previously conceived the idea that the thing patented could be done; he must have reduced his idea to practice and embodied it in some useful practical form; it must have been not merely an experiment, but a completed invention or discovery put into practical form and capable of working successfully. Whether it was in actual use is immaterial except so far as that fact may go to determine whether the invention was completed and capable of use. Whoever restores an abandoned or lost art or invention may obtain a patent for it. If a person having made a discovery or invention applies for a patent in this country, his claim will not be defeated by the fact that the same invention has been previously known and in use in a foreign country, unless it has been patented or fully described in some printed publication. Any inventor or his assignee may obtain a patent for an invention which he has first patented in a foreign country, provided it has not been in public use in the United States for more than two years prior to the application. In this case the patent will expire at the same time as that in the foreign country, or, if there be more than one foreign patent, at the same time with the one having the shortest term; but in no case will it last longer than 17 years. Thus if a patent is granted in this country for an invention previously patented in Prussia
