
    Alsworth Baker, Appellant, v. Samuel Whiteside, Appellee.
    APPEAL FROM MADISON.
    As a general rule, the terms of a written agreement can not be changed by parol, but the time of its performance may be extended. 
    
    To a declaration on a contract to convey a lot of ground by deed, if one hundred and twenty-five dollars was paid at a certain time, a plea, that no demand was made for the deed, and that defendant was always ready and willing to execute it, and that the defendant offered to make the deed according to his covenant, and the plaintiff objected and said when he wished the deed he would apply for it, is good. 
    
    
      
       The time of performance of a contract may be extended by a subsequent parol agreement, and no new consideration is necessary, where there are mutual acts to be performed by the parties. Wadsworth et al. v. Thompson, 3 Gilm., 423.
      , It is a familiar principle, that you may give evidence to explain, but not to vary, add to, or alter a written contract. This is a general rule. But if there is doubt and uncertainty, not about what the substance of the contract is, but as to its particular application, it may be explained and properly directed. Lane v. Sharp, 3 Scam., 573. Doyle et al. v. Teas et al., 4 Scam., 257. Scott, administrator v. Bennett, 3 Gilm., 254. Scammon v. Adams et al., 11 Ill., 577. O’Reer v. Strong, 13 Ill., 689. Harlow v. Boswell, 15 Ill., 57.
    
    
      
       In case of bond to convey land, the purchaser is not bound to prepare and tender a deed to the vendor to execute, unless such obligation can be fairly inferred from the terms of the contract. The rule may be different in England. Buckmaster v. Grundy, 1 Scam., 314. 2 Randolph, 20.
    
   Opinion of the Court by

Chief Justice Wilson.

This is an appeal from the Madison circuit court, in an action of covenant on a writing obligatory, executed by S. Whiteside to A. Baker, in the penalty of two hundred dollars, that if he, the said Baker, should pay to the said Whiteside one hundred and twenty-five dollars, on or before the first day of October next ensuing, he, the said Whiteside, would execute and deliver to the said Baker, a deed in fee simple, for a lot in the town of Bdwardsville.

Baker avers in his declaration, that he did pay the sum of one hundred and twenty-five dollars, according to agreement; nevertheless, the said Whiteside did not, on the first day of October, or at any time before or since, execute and deliver to the said Baker, a good and sufficient deed, although often requested so to do. To this declaration, the defendant pleaded two pleas :

1. That the plaintiff made no demand of the said defendant, for the deed specified, and that the said defendant was always ready and willing to execute the same.

2. That the said defendant offered to make the deed according to his covenant, and the said plaintiff objected, and said, when he wished the deed he would apply for it.

Starr, for appellant.

Cowles, for appellee.

Both these pleas are demurred to, and the question presented for our determination is, whether or not, the court below erred in overruling the demurrers.

As the second plea presents the strongest ground of defense, we will consider it first. If it is a correct principle of law, and that it is, the court is fully satisfied, that he who prevents a thing from being done, shall not avail himself of the non-performance he has occasioned, the demurrer was correctly overruled. The plaintiff’s conduct can be considered in no other light than a waiver of the condition of the bond so far as related to the time of its performance. As a general rule, it is true, that the terms of a written agreement can not be changed by parol, but that the time of its performance may be extended, is settled by a variety of cases; that of Keating v. Price, 1 Johns. Cases, 22, is directly in point. In that case, the defendant promised in writing, to deliver a quantity of staves, on or before the first day of May, 1796. The defendant, on the trial, proved, that in January, 1796, the plaintiff agreed to extend the time until the spring following. The court said, that an extension of time may often be essential to the performance of contracts, and there can be no reason why a subsequent agreement for that purpose, should not be valid, and proved by parol evidence.

The first plea, the court is of opinion, is also good. According to the true construction of the contract, no time is fixed for executing and delivering the deed; a demand by the plaintiff was therefore necessary, and as no such demand is averred specially, the demurrer to the plea was correctly overruled. The judgment of the court below is affirmed, and the cause remanded, with leave to the plaintiff to with-' draw his demurrer, and take issue on the pleas filed,

Judgment affirmed. 
      
       Justice Smith having been counsel in this cause, gave no opinion.
     
      
      
         3 Durnford and East’s T. R., 591. Philip’s Evidence, 439. The time of the performance of the condition of a bond may be enlarged by a parol agreement between the parties. Fleming v. Gilbert, 3 Johns. Rep., 528. See also Thompson v. Ketchum, 8 Johns. Rep., 189.
     