We concur in so much of the opinion of the court below as holds that
“If more than one application could be made, the final application must be made within two years after the allowance of the original application, the term ‘the original application,’ as used in this section, meaning the first application.”
There is no ambiguity in the language of the statute as to the limitation of time within which the later application must be made. The provisions for withholding the patent upon the nonpayment of the final fee within six months, and for relief from the effect of such provision, are imperative. The construction contended for by the appellant would permit an indefinite prolongation of a monopoly by means of unlimited forfeitures and renewals, and would nullify the policy of the law, which requires diligence in the prosecution of applications for and issuance of patents. The patent in suit, therefore, was granted by the Commissioner of Patents under a mistake as to the law, but without authority of law, because upon an invalid application. This defense may be raised in an action for infringement. “Where it is evident that the commissioner, under a misconception of the law, has exceeded his authority in granting or reissuing a patent, there is no sound principle to prevent a party sued for its infringement from availing himself of the illegality, independently of any statutory permission so to do.” Mahn v. Harwood, 112 U. S. 354, 358, 6 Sup. Ct. 451, 28 L. Ed. 665; Planing-Machine Company v. Keith, 101 U. S. 479, 25 L. Ed. 939.
The decree is affirmed, with costs.