The agreement between the plaintiff, and defendant, as described by plaintiff in his answer to the interrogatories, was, that if the defendant was legally compelled, and forced, to pay for the patent right of the saw, that such payment should be a charge against the plaintiff. Under this contract, the defendant yielded to the right'of the patentee, without suit, and paid him $ 100, and now insists on this payment, as an offset to the note given to the plaintiff for the saw. Did the court err in the charge, that the defendant was not bound to permit himself to be sued, but might pay the patentee, and insist on this payment as a defence to the note, if the defendant showed that the patentee was entitled to it?
If one purchase land of another, with warranty, and without suit yields to a paramount title, he may sue on the covenant, and if he show that the title to which he yielded, is paramount to the title of his vendor, he may recover. Dupuy v. Roebuck, 7 Ala. 485; 2 Greenl. Ev. 202; Hamilton v. Cutts, 4 Mass. 349; Tuft v. Adams, 8 Pick. 547; 5 Conn. 497; 9 Wend. 416. The vendee, however, assumes the burthen of proving, that the title to which he yielded is paramount to the title of the vendor, and thus, in the action of covenant, the right of his vendor, and the right of him to whom the vendee yielded, will be tried. We think the contract in this case, resembles, in this respect, a covenant of warranty; and that the defendant, upon demand, might yield to the right of the patentee, and pay the sum to which his right entitled him, without suit. The language of the contract is, that if the defendant was legally compelled to pay, that then the payment should be borne by the plaintiff.
In this case, the burthen of proof lay on the defendant, to show the right to which he yielded, entitled the patentee to recover; and it is therefore as effectually tried in this suit, as it would have been, had he permitted himself to be sued. *382But it is contended, that by the express terms of the contract, the defendant stipulated to litigate with the patentee, his right to demand payment for using the saw. We do not think the contract is to be thus interpreted. It is true, if such a stipulation, in express terms, was embraced in the contract, and if the defendant had undertaken expressly to submit to a law-suit, and to litigate the right of the patentee with him, before he could claim of the plaintiff the amount due the patentee, he then must have shown, that such litigation had been commenced, and determined against him. But we cannot infer from the contract, as proved, that the defendant did agree, to litigate in law, the right of the patentee; but we think, by a fair interpretation of it, that the contract resembles a covenant of warranty, and that the defendant might yield to the demand of the patentee, without suit, if satisfied that he was entitled to recover.
2. Nor is there any error in the charge of the court, that - the jury should determine from the evidence, whether the patent produced, embraced the saw, or not. It is the duty of the court to construe all written instruments, but the application of them to the subject matter to which they relate, is always a matter of fact: that is, if a deed is introduced as evidence, the nature, quality, or quantity, of the estate conveyed by it, is a matter of law, and must be determined by the court; but the identity of the land conveyed, or whether the land in controversy, is covered by the deed, is a matter of fact, to be tried by the jury. In this case, it was the duty of the court to construe the patent, if any question of construction had arisen ; but whether the saw purchased by the defendant, from the plaintiff, was one of the description embraced by the patent, and which gave the patentee the right to demand the sum for its being used by the defendant, depended on the evidence, and was a question of fact, to be determined by the jury.
There is no error in the judgment, or in the ruling of the court, and the judgment is consequently affirmed.