As in that of an absolute conveyance, more particularly when the mortgage instrument contains a covenant of warranty or other covenant.25 And it has been so applied not only in jurisdictions in which the legal title passes to the mortgagee,26 but in other jurisdictions likewise.27 There appears to be no difference, as regards the doctrine of estoppel, between the principles applicable to a mortgage and to an absolute conveyance, and the statements here made in reference to the latter will ordinarily apply as well to the former.27a

If a conveyance is for any reason absolutely invalid, there is no estoppel upon the grantor as to an after-acquired title.28 But that the conveyance is in25. Jones v. Wilson, 57 Ala. 122; Curren v. Driver, 33 Ind. 480; West Michigan Park Ass'n v. Pere Marquette R. Co., 172 Mich. 179, 137 N. W. 799; Hagen-sick v. Castor, 53 Neb. 495, 73 N. W. 932; Smith v. De Russy, 29 N. J. Eq. 407; Jackson v. Littell, 56 N. Y. 108; Donovan v. Twist, 85 N. Y. App. Div. 130, 83 N. Y. Supp. 76; Jarvis v. Aikens, 25 Vt. 635; Doswell v. Buchanan, 3 Leigh (Va.) 365, 23 Am. Dec. 280.

26. Howze v. Dew, 90 Ala. 178, 24 Am. St. Rep. 783, 7 So. 239; Hoyt v. Dimon, 5 Day (Conn.) 479; Gochenour v. Mow-ry 33 111. 331; Lagger v. Mutual Union Loan & Building Ass'n, 146 111. 283, 33 N. E. 946; Parsons v. Little, 66 N. H. 339, 20 Atl. 958; White v. Patten, 24 Pick. (Mass.) 324; Cockrill v. Bane, 94 Mo. 444, 7 S. W. 480; Northrup v. Ackerman, 84 N. J. Eq. 117, 92 Atl. 909; Rauch v. Dech, 116 Pa. St. 157, 2 Am. St. Rep. 598, 9 Atl. 180.

27. Clark v. Boyreau, 14 Cal. 636; Yerkes v. Hadley, 5 Dak.

324, 2 L. R. A. 363, 40 N. W. 340; Hill v. O'bryan, 104 Ga. 137, 30 S. E. 996; Rice v. Kelso, 57 Iowa, 115, 7 N. W. 3, 10 N. W. 335; Whitley v. Johnson, 135 Iowa, 620, 113 N. W. 550; Thalls v. Smith, 139 Ind. 496, 39 N. E. 154; Watkins v. Houck, 44 Kan. 502, 24 Pac. 361; Gray v. Franks, 86 Mich. 382, 49 N. W. 130; Caple v. Switzer, 122 Mich. 636, 81 N. W. 560; Osborn v. Scottish American Co., 22 Wash. 83, 60 Pac. 49.

27a. If one who has no title to land undertakes to mortgage the land to one who has a perfect title, and subsequently acquires the land by descent from the latter, he is not estopped, it has been held, to assert such title as against the latter's representative. "Neither the mortgagee nor her representative can deny that her own title was good, because she had taken a conveyance from one having no title." Harding v. Springer, 14 Me. 407, 31 Am. Dec. 61.

28. Kercheval v. Triplett, 1 A. K. Marsh (Ky.) 493; Patter2 R. P. - 59 valid as to one grantor obviously does not affect the estoppel upon another grantor.29

- (c) Necessity and character of covenants.

Applying the view, above referred to, that a conveyance is given the effect of transferring an after-acquired title as a means of avoiding the necessity of suing on the covenant for title, it has frequently been asserted that the presence of such a covenant is necessary in order that an after-acquired title may pass.30 And the cases occasionally distinguish between the different classes of covenants as regards their efficacy in this respect. Thus a covenant of warranty has been referred to in many cases as effective for this purpose,31 frequently as the result of a mistaken application of the doctrine of warranty at common law,32 and the same effect has been given to a covenant for quiet enjoyment,33 while it has, in some states, been denied to a covenant for seisin son v. Pease, 5 Ohio, 191; Kemery v Zeigler, 176 Ind. 660, 96 N. E. 950.

29. Blakeslee v. Mobile Life Ins. Co., 57 Ala. 265; Chapman v Abrahams, 61 Ala. 108; Wellborn v. Finley, 7 Jones L. (N. C.) 228.

30. See cases cited 11 A. & E. Encyc. Law (2nd Ed.) 409.

31. Schuman v. George, 110 Ark. 486, 161 S. W. 1038; Doe d. Potts v. Roe, 3 Houst, (Del.) 369, 11 Am. Rep. 757; Oliver v. Holt, 141 Ga. 126, 80 S. E. 630; Walton v. Follansbee, 131 111. 147, 23 N. E. 332; Childs v. Mc-chesney, 20 Iowa, 431, 89 Am. Dec. 545; Creekmore v. Bryant, 158 Ky. 166, 164 S. W. 337; Bennett v. Davis, 90 Me. 457, 38 Atl. 372; Knight v. Thayer, 125 Mass. 25; Morris v. Jansen, 99 Mich. 436, 58 N. W. 365; De-merse v. Mitchell, 187 Mich. 683,

Or for good right to convey.34 On the other hand there are numerous decisions and judicial dicta that if the conveyance purports to transfer some certain estate, the grantor is estopped, irrespective of the presence of covenants therein, to assert that such an estate did not pass thereby.35

164 N. W. 97; Barron v. H. D. Williams Cooperage Co., 185 Mo. App. 625, 171 S. W. 683; Moore v. Rake, 26 N. J. L. 574; Ford v. Mcbrayer, 171 N. C. 420, 88 S E. 736; Broadwell v. Phillips. 30 Ohio St. 255; Blackwell v. Harrelson, 99 S. C. 264, 84 S. E. 233; Johnson v. Brauch, 9 S. D. 116, 62 Am. St. Rep. 857, 68 N. W. 173; Ferguson v. Prince, 136 Tenn. 543, 190 S. W. 548; Raines v. Walker, 77 Va. 95.

32. 2 Smith's Leading Cases, Judge Hare's note (8th Am. Ed.) 841 et seg; Rawle, Covenants for Title, Sec.Sec. 252, 254; Bigelow, Estoppel (6th Ed.) pp. 453, 463.

33. Smith v. Williams, 44 Mich. 240, 6 N. W. 662; Long Island R. Co. v. Conklin, 29 N. Y. 572; Tully v. Taylor, 84 N. J. Eq. 459, L. R. A. 1918B, 731, 94 Atl. 572. See Taggart v. Risley, 4 Ore. 235.

When the conveyance does not purport to convey such interest only as the grantor has, or a limited interest only, the fact that a covenant therein is special, that is, against the acts of the grantor and those claiming under him only, does not appear to affect its operation by way of estoppel.36

- (d) Cases to which doctrine inapplicable.

The doctrine that a grantor is estopped to assert an after-acquired title applies only when such assertion would involve a denial that the conveyance passed the interest or estate which it purported to pass. Consequently the grantor may freely assert a title subsequently acquired by him from the grantee either by voluntary conveyance,37 judicial or execution sale,38