Opinion by

The plaintiff is seeking to reform a written agreement be*359tween himself and the defendant. He alleges that he entered into an agreement for exploring and operating the land of the defendant for oil upon the terms-and conditions appearing in the form of lease attached to his bill known as “ Exhibit B ; ” that this lease had been to some extent defaced by erasures and interlineations, and the form of lease marked “ Exhibit A ” was filled out by his attorney to take its place, and was signed by the parties. He further alleges that it was so signed with the understanding on the part of the defendant and himself that it was in legal effect the same as the form “ Exhibit B; ” and that he was so advised by his counsel. He now finds the lease to be different in one important particular from what he supposed the effect of “ Exhibit B ” to be, and for this reason lie asks to reform the lease so as to make it conform to “ Exhibit B.”

No fraud is alleged. No stipulation was omitted by mistake. The contract was read before it was signed; and the complaint now made is that the plaintiff was mistaken in his construction of it, and that, as the court now expounds it, it is not in accordance with the understanding between the parties. This is denied by the defendant, and we concur in opinion with the learned master, that the proof of mutual mistake is not so clear and precise as to justify a decree, if the plaintiff was in other respects entitled to the relief he seeks.

But as the learned master points out, the legal effect of both forms of lease, so far as the forfeiture clause is concerned, is the same. The lessor is the only person who can assert a forfeiture. The lessee may do, or omit to do, that which the lease declares shall be a cause of forfeiture, and so subject his leasehold interest or estate to an entry and forfeiture by the lessor; but he cannot enter on himself, and declare his own estate forfeited, and so divest the rights and defeat the remedies of his lessor. A tenant of a dwelling house may forfeit his right and title under his lease by doing that which his lease names as a ground of forfeiture; but that he can by his own breach of his contract forfeit his «landlord’s right to the rent, is a proposition so preposterous that whoever asserts it must show a plain unambiguous agreement of the lessor to that effect. In form “ B ” the lessor had a right of forfeiture which he might exercise or not. The lessee could prevent its exercise by payment but he could not compel its exercise by nonpayment.

*360The learned auditor and the court below were right on both questions considered. The proofs did not come up to the standard required by a court of equity. If the proofs had been sufficient to reform the lease so as to make it conform to the original draft, “ Exhibit B,” still the legal effect of the lease would be unchanged.

The decree is affirmed at the cost of the plaintiff.

Cf. McMillan v. Pa. Co., above, page 142, and Cochran v. Pew, above, page 184.