This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
In some jurisdictions the consideration is said not to be any part of the contract,1 and accordingly an oral modification of the consideration is enforceable if such oral modification does not affect the covenant on the part of the party who was to do an act within the statute, and if it is limited to the promise of the adversary party, which is a consideration for such covenant.2 A written oil and gas lease, to be extended from year to year as long as production continues, upon a payment of specified royalty, may subsequently be so modified by parol as to discharge the lessee from liability as to such royalty.3 A written contract for the sale of land, which provides for the time of payment, may be modified by a subsequent oral contract, changing the time for making such payment.4 If the oral contract provides for the payment of certain monthly installments, and the delivery of the deed when the purchase price is paid in full, a subsequent oral contract to accept the rest of the purchase money with interest on deferred payments at once, gives the vendee a right to a deed for the property upon tender of such amount.5
3 King v. Crone, 114 Ark. 121, 160 S. W. 238; Hawkins v. Studdard, 132 Ga. 265, 131 Am. St. Rep." 190, 63 S. E. 852; McConathy v. Lanham, 116 Ky. 735, 76 S. W. 536.
4 Lawyer v. Post, 109 Fed. 512, 47 C. C. A. 491 (obiter); King v. Orone, 114 Ark. 121, 169 S. W. 238; Platt v. Butcher, 112 Cal. 634, 44 Pac. 1060.
5 Clark v. Guest, 54 0. S. 298, 43 N. E. 862.
6 Bradley v. Harter, 156 Ind. 499, 60 N. E. 139.
7Bonicainp v. Starbuck, 25 Okla. 483, L. R. A. 1917B, 141, 106 Pac. 839.
1See Sec. 1349 et seq.
2 Anderson v. Moore, 145 111. 61, 33 N. E. 848; Crawford v. Gas Co., 183 Pa. St. 227, 38 Atl. 595.
3 Crawford v. Gas Co., 183 Pa. St. 227, 38 Atl. 595.
4 Anderson v. Moore, 145 111. 61, 33 N. E. 848.