The instrument relied upon, and pleaded, in defence of the present action, is an unsealed agreement, whereby the former holder of the note declared upon granted an extension of the time of payment thereof, of two years for one third, three years for an additional third ; and four years for the balance. The makers of the note, on their, part, agreed to pay the debt in full, within the period of this extension. The first instalment was not paid, when payable by the terms of this contract; after which, the holder of the note, who had executed this agreement, transferred it to the present plaintiff, who now attempts to collect the entire note.
It is fully settled, in this Commonwealth, that a covenant, or other agreement, not to sue for a limited time an existing cause of action, is only a collateral contract, and cannot be pleaded in defence of an action at law upon the original cause of action. A perpetual covenant not to sue is equivalent to a release, and to avoid circuity of action may be pleaded as such. But if the agreement, whether under seal or riot, is a limited one, the only remedy for breaking it is by an injunction in equity, or by an action on the agreement for damages. Perkins v. Gilman, 8 Pick. 229. Foster v. Purdy, 5 Met. 442. Even before this doc trine was established, the nonpayment, at the time stipulated. *427of any instalment under such a letter of license or agreement of extension, was held to warrant an immediate recovery of the entire balance of the original debt. Upham v. Smith, 7 Mass. 265.
Inasmuch as the defendants have failed to perform any part of the mutual agreement, there is apparently no equitable, certainly no legal, ground of defence to the note, and there must Judgment for the plaintiff on the agreed, facts