Opinion by

This was an action of assumpsit for the recovery of arrears of ground rent. If was brought against Jacob R. Heitz to whom the deed, in which the ground rent was reserved, was made by the plaintiff. Heitz interposed no defense to the action, but James Arthur under a deed from him intervened as terre-tenant. *597The plaintiff put in evidence his deed to Heitz and rested. Thereupon Arthur made two offers of evidence which were rejected, and there being no other offer made, the court directed a verdict for the amount of the plaintiff’s claim. From the judgment entered on the verdict this appeal -was taken.

It appears that there was a contract entered into between Leibert and Arthur on April 24, 1896, by which the former agreed to sell and the latter to buy the lot described in the deed from Leibert to Heitz and in the deed from Heitz to Arthur. The contract was prepared by Arthur and it was provided therein that Leibert, upon the demand of Arthur, should dedicate by deed at his own cost to the city the whole bed of Mower street, fifty feet wide, adjoining the lot above referred to and lying between the same and other ground of Leibert. This provision in the contract is noted herein as proper for consideration in connection with the rejected offers. It should also be noted hare that it was agreed on the trial that Leibert had complied with the provisions aforesaid. The offers did not allege fraud, accident or mistake on the part of Leibert, but averred that he stated to Arthur prior to and at the time of the execution of the contract, and as an inducement to the execution of the same, that he had a contract with the Drexel syndicate by which they were to open Mower street at any time upon his demand, and that he would procure them to open it at any time on Arthur’s request that he should do so. It is a singular circumstance that the party who prepared the contract with Leibert and included in it the provision hereinbefore referred to omitted from it an oral agreement which induced him to enter into said contract, and a breach of which he now alleges would entitle him to damages in the sum of $17,000, from which he could pay the arrears of the ground rent sued for, and for the balance of which he could have a certificate under the defalcation act. It is also noticeable that the rejected offers contain no denial by Arthur of the existence of an agreement by the syndicate to open Mower street, nor any assertion by Arthur of a refusal by Leibert to demand of the syndicate performance of their agreement with him. It should also be noted here that the offers of evidence were not germane to the defense set up in the notice of special matter, and that an agreement of the syndicate to dedicate to the city of Philadelphia so much of their *598land as formed the bed of Mower street was not an agreement to open said street. Besides it is quite clear that the rejection of evidence not relevant to the defense presented by the pleadings furnishes no ground for reversing a judgment.

We have duly considered the rejected offers and are unable to find in them any sufficient warrant for the appellant’s claim as made. There is no such measure of damages admissible in the suit as is contended for. The allowance of it might result in a set-off which would not only satisfy the arrears of ground rent sued for but would extinguish the principal. A set-off based upon unliquidated damages measured as proposed is not applicable to this action. Set-offs are allowed in order to prevent multiplicity of actions, and ought not to be allowed so as to be themselves the cause of new disputes. If allowed, they might “ throw open a perpetual rent to a perpetual dispute by an unwritten alteration of its amount, and thus make set-offs to be the cause of strifes instead of a way of ending them: ” Mangle v. Stiles, 31 Pa. 72; Provident Life and Trust Co. v. Fiss, 147 Pa. 232.

The specifications of error are overruled and the judgment is affirmed.