The amount of the rent to be paid must be certain or capable of reduction to a certainty,99 but it is sufficient that the amount can be ascertained before the time for payment.1 As an example of rent which is thus ascertainable at the time for its payment, though not at the time of the demise, may be mentioned rent consisting of a certain portion of the crop which may be raised upon the land, or computed with reference to the amount of minerals extracted from the land. So it may be made to fluctuate with the price of wheat,2with the income which the tenant may derive from the use of the premises,3 or with the particular use which the tenant may make of the land.4

95. Leighton v. Theed, 2 Salk. 413; Robinson v. Deering, 56 Me. 357; Hammond v. Thompson, 168 Mass. 531, 47 N. E. 137.

96. Hall v. Joseph Middleby, 197 Mass. 485, 83 N. E. 1114.

97. Clun's Case, 10 Coke 127a; ex parte Smyth, 1 Swanst. 337, and notes; Hogland v. Crum, 113

111. 365, 55 Am. Rep 424; Watson v. Penn, 108 Ind. 21, 8 N. E. 636, 58 Am. Rep. 26. Gee v. Gee, 22 N. C (2 Dev. & B. Eq.) 103.

98. See Tiffiny, Landlord & Ten. pp. 1076-1079; Wilson v. Hagey, 251 111. 452. 96 N. E. 277; Smithwick v. Oliver. 94 Ark. 451, 127 S. W. 706.

Not infrequently the amount of the rent is reduced by an agreement entered into between the landlord and tenant after the making of the lease. That such an agreement must be supported by a valid consideration has been recognized in a number of cases,5 and there are several decisions upon the sufficiency of the consideration in the particular case.6 In spite of these decisions, there is, it is submitted, room for question whether, applying common law standards, a consideration should be regarded as necessary. At common law, one entitled

99. Co. Litt. 142a; Gilbert, Rents, 9.

1. Co. Litt. 96a; Selby v. Greaves, L. R. 3 C. P. 594; Walsh v. Lonsdale, 21 Ch. Div. 9; Mc-farlane v. Williams, 107 111. 33; Dutcher v. Culver, 24 Minn. 584.

2. Kendall v. Baker, 11 C. B. 842.

3. Hardy v. Briggs, 14 Allen (.Mass.) 473; Long v. Fitzsimmons, 1 Watts & S. (Pa.) 530.

4. Roulston v. Clark, 2 H. Bl. 563; Bowers v. Nixon, 12 Q. B. 558.

5. Goldsborough v. Gable, 140 111. 269, 15 L. R. A. 294, 29 N. E. 722, Id. 152 111. 594, 38 N. E. 1025; Wheeler v. Baker, 59

Iowa, 86, 12 N. W. 767; Bow-ditch v. Chickering, 139 Mass. 283, 30 N. E. 92; Wharton v. Anderson, 28 Minn. 301, 9 N. W. 860; Hazeltine v. Ausherman, 87 Mo. 410; Coe v. Hobby, 72 N. Y. 141, 28 Am. Rep. 120.

6. Doherty v. Doe, 18 Colo. 456, 33 Pac. 165; Raymond v. Krauskopf, 87 Iowa, 602, 54 N. W. 432; Lamb v. Rathburn, 118 Mich. 666, 77 N. W. 268; Ten Eyck v. Sleeper, 65 Minn. 413, 67 N. W. 1076; Bowman v. Wright, 65 Neb. 661, 91 N. W. 580, 92 N. W. 580; Holmquist v. Bavarian Star Brew. Co., 1 App. Div. 347, 72 N. V. St. Rep. 443, 37 N .Y. Supp. 380.

To rent can extinguish it by executing a release in favor of the person whose estate was charged therewith,7 and an agreement to reduce the rent is, it is conceived, in effect merely a partial release of the rent, that is, a pro tanto transfer of the rent by way of release, which is perfectly valid at common law, without any consideration.8 The common law release, however, required a seal, and in so far as a seal may still be necessary to the validity of a release, an agreement, not under seal, for the partial or total extinguishment of rent, might well be regarded as a contract to execute a release, to which the court would give effect only if supported by a consideration.

An agreement, made after the making of the lease, in terms to increase the rent, does not, strictly speaking, increase the rent. The additional sum agreed to be paid is not rent, since it is not reserved upon the making of a lease or other conveyance.9 The only theory on which it could be regarded as rent would be by considering the agreement as a new demise, effecting a surrender by operation of law of the original lease,10 but this would give to the agreement a force ordinarily not contemplated by the parties.11