in one application. It is essential that the specification be a full and intelligible description of the invention. Obscurity or ambiguity in this respect may defeat the patent. It is also of prime importance that the claim be coextensive with the invention, and discriminate distinctly between the old and what is claimed as new. If it appear that anything claimed is not new, the patent will be broader than the invention and therefore void. It will also be a fatal defect if the claim is for a machine when the invention is a process; or for the discovery of a law in nature or property of matter, when the invention is the practical application of such law or property. Cases are numerous in which patents have been declared void on account of defective specifications. It sometimes happens that two or more persons claim each to be the first inventor of the same thing. Then the commissioner declares a case of “interference” to exist, and after due notice to the parties, they are heard in support of their several claims before a primary examiner, and if either party is dissatisfied with his decision, before the board of examiners in chief, and if still dissatisfied, before the commissioner on appeal. This may happen although one of the claimants has previously received a patent; for the commissioner, if he comes to the conclusion that the second claimant has a better right, or an equal right, will give him also a patent, and leave the two to determine by legal measures which is valid. Appeals from the commissioner may be taken in all cases except interferences to the supreme court of the District of Columbia. If a patent is void by reason of a defective specification, or because the patentee claimed as his own invention more than he had a right to claim as new, he may surrender his patent to the commissioner, and file with him a new and corrected specification, and the commissioner may thereupon issue to him a new patent, provided the error has arisen from inadvertence, accident, or mistake, and without any fraudulent or deceptive intention. Or the patentee may make a disclaimer in writing of such parts of the thing patented as he does not wish to claim; and this disclaimer, being duly received and recorded, shall have the same effect as if it had been originally a part of such specification. Even without such surrender or disclaimer, a patent may still be sustained by the court for any material and distinguishable part for which the claim was valid, although there are other parts of the claim to which the patentee is not entitled; but he can recover no costs for the infringement of such a patent without surrender or disclaimer. There is a very wise provision to meet the frequent case where an inventor wishes to secure his right, but is not ready to present a full and complete specification, and needs time for experimenting or other purposes. He may file a caveat, which will be placed in the secret archives of the patent office; and if there be any application within a year for anything which appears to interfere with his claim, he shall have notice and may appear and prove priority; and by a second caveat he may renew it for another year, and so on successively. It is to be noticed, however, that a caveat cannot be filed by an alien, unless he has resided in the United States one year, and has made oath of his intention to become a citizen, according to law. Even where caveats are not taken out, all pending applications are regarded as so far confidential that, until after a patent is issued, no information will be given to any one but the claimant respecting the existence of any application, or any questions which may have arisen in relation to it. To guard against deception of the public as to what inventions are protected by patent, all patented articles are to be marked with the date of the patent, and any person who shall put any word or remark upon a thing not patented which shall indicate that it is the subject of a patent, or put upon it the name of any patentee without his consent, is liable to a penalty of $100 for each offence. A fee of $15 is required on filing the application, and $20 when the patent issues; $10 on filing a caveat, and $30 when application is made for a reissue. The fees for designs are $10 for 3½ years, $15 for 7 years, and $30 for 14 years.—Patents may be assigned by instruments in writing, which must be recorded in the patent office within three months from execution. The assignment may be of the whole or an undivided part of the patent, or a license may be given conferring the exclusive right to make, use, and sell the thing patented within any specified part of the United States.—Term. By the act of 1836 patents were granted for 14 years, and provision was made for an extension in certain cases for 7 years more. In 1861 the original term was fixed at 17 years, and extensions were prohibited for patents granted after that year. This provision was retained in the act of 1870, so that patents are now issued for 17 years without the privilege of renewal. Patents granted prior to 1861 might formerly be extended by the commissioner after hearing the parties interested, and after public notice to others disposed to object, provided he was satisfied that the patentee, without neglect or fault on his part, had failed to obtain from the use and sale of his invention or discovery a reasonable remuneration. The last patent coming within the provisions of the law in regard to extensions expired March 2, 1875, so that no extension can now be granted except by special act of congress. Such acts have been passed, but the practice is liable to abuses. Patents for designs may be taken out for 3, 7, or 14 years, as the applicant may elect.—Infringement. To determine what constitutes an infringement is one of the most difficult matters connected with the subject of patents. So much depends upon the points of resemblance and difference between the infringing and infringed matter, that
