It was competent for the defendant to show that he was a surety only, and that the plaintiff knew it. Carpenter v. King, 9 Met. 511. An agreement with the principal, for a consideration, to give time, and not to sue him within a time limited, discharges the surety. Greely v. Dow, 2 Met. 176. But mere omission to sue the principal will not discharge a surety. Hunt v. Bridgham, 2 Pick. 581.

And the court are of opinion that the averment in the answer was sufficient to let in this proof, especially as the plaintiff did not object to the proof when offered.

Exceptions overruled.