from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
TO ALTER. To change. Alterations are made either in the contract itself, or
in the instrument which is evidence of it. The contract may at any time be
altered with the consent of the parties, and the alteration may be either in
writing or not in writing.
2. It is a general rule that the terms of a contract under seal,
cannot be changed by a parol agreement. Cooke, 500; 3 Blackf. R. 353; 4
Bibb. 1. But it has been decided that an alteration of a contract by
specialty, made by parol, makes it all parol. 2 Watts, 451; 1 Wash. R. 170;
4 Cowen, 564; 3 Harr. & John. 438; 9 Pick. 298; 1 East, R. 619; but see 3
S.& R. 579.
3. When the contract is, in writing, but not under seal, it may be
varied by parol, and the whole will make but one agreement. 9 Cowen, 115;
5.N. H. Rep. 99; 6 Harr. & John, 38; 18 John. 420; 1 John. Cas. 22; 5 Cowen,
606; Pet. C. C. R. 221; 1 Fairf. 414.
4. When the contract is evidenced by a specialty, and it is altered by
parol, the whole will be considered as a parol agreement. 2 Watt 451; 9
Pick. 298. For alteration of instruments see Erasure; Interlineation. See,
generally, 7 Greenl. 76, 121, 394; 15 John. 200; 2 Penna. R. 454.