Murray, C. J., concurred.

A covenant for a lease to be renewed indefinitely at the option of the lessee, is, in effect, the creation of a perpetuity; it puts it in the power of one party to renew for ever, and is therefore against the policy of the law.

Another and substantial objection to the enforcement of the clause of renewal in the lease disclosed by the record, consists in the want of any certain basis for the ascertainment of the rent to be paid. It says the rent shall be stipulated according to the value of the property. But who is to fix the value of the property ? Certainly each party would have the right to do it for himself, in the absence of any other stipulation. I know of no rule of law which can compel a party to change his estimate of the value of his property, when by contract he has the right to determine it for himself. A Court of Equity is always *66chary of its power to decree specific performance, and will withhold the exercise of its jurisdiction in that respect, unless there is such a degree of certainty in the terms of the contract as will enable it at one view to do complete equity. The maxim id certum est quod certum reddi potest, is here improperly invoked; for, governed by the language of the lease, there is no test by which certainty can be attained.

The judgment is reversed, and the cause remanded.