prepared the opinion for the court.
1. The only question presented for consideration on this appeal is whether the court erred in holding that the mortgage dated December llj 1885, was barred by the statutes of limitation at the time of the commencement of this suit. The period prescribed by the statute at the time the right of action accrued *439on tbe note described in that mortgage was six years.' This note fell due June June 11, 1886, 'and the right of action thereon was barred June 11, 1892, unless extended by some means or agreement outside of the instrument itself.
The Act of 1889 (Session Laws 1889, p. 172) extended the period within which action might be brought on a written instrument to eight years, but expressly provided that the Act should not affect causes of action which had accrued prior to its passage. The right of action on this first note having accrued prior to that time, it was not affected by this Act; and, the statute of limitation having fully run, unless tolled, prior to the time when the Codes of 1895 took effect, the status of the case is not affected by the Codes. (First Div. Comp. St. 1887, Sec. 42; Sess. Laws 1889, p. 172; Code Civ. Proc. Secs. 512, 557, 8456; Political Code, Sec. 9; Sherman v. Nason, 25 Mont. 283, 64 Pac. 768; Guiterman v. Wishon, 21 Mont. 458, 54 Pac. 566.) The last case cited further decides that the statute of limitation does not confer a vested right, to’ that extent modifying the decision in Gillette v. Hibbard, 3 Mont. 417, by establishing the doctrine that limitation Acts affect the remedy and not the right.
2. Counsel for respondent contends that the provisions of Section 3842 of the Civil Code apply to this case. That section provides that a mortgage “can be created, renewed or extended only by writing, with the formalities required in the case of a grant of real property.” This statute is direct and certain, and admits of but one interpretation. A mortgage lien since its approval cannot be created, renewed or extended in contravention of its provisions.. (Wells v. Harter, 56 Cal. 342; London & S. F. Bank v. Bandmann, 129 Cal. 220, 52 Pac. 583, 65 Am. St. Rep. 179.) This statute, however, did not take effect or become law until July 1, 1895, while the last renewal of the note in the case before us was executed February 8, 1890. If at the last-named date the renewal of a note, as a matter of law, extended or renewed a mortgage lien given to secure the indebtedness evidenced by the former note, such extension or renewal *440became and was, at tbe time of the enactment of Section 3842, supra, a valid, subsisting contract, and the legislature could not impair its obligation by an enactment subsequent to the execution of such contract. (Cooley, Const Lim. (6th Ed.) 328.) And, if a renewal of the note did not toll the statute of limitation, the plaintiff’s right of action was barred thereby June 11, 1892, six years from the date when the first note became due. In either event, the section above quoted can have no application to the facts of this case. No part of the Civil Code is retroactive unless expre.ssly so declared. (Civil Code, Sec. 4651.)
3. A mortgage does not create an estate in real property. It is a mere security for the payment of a debt. It is an incident to that which it secures. (Hull v. Diehl, 21 Mont 71, 52 Pac. 782.)
The general doctrine appears to be that a mortgage secures a debt or obligation, and not the evidence of it, and no change in the form of the evidence or time of payment can operate to discharge the mortgage. So long as the debt secured remains unpaid, the renewal of the evidence of the debt will not impair the lien of the mortgage. The mortgage is barred only when the debt is barred. (Lent v. Morrill, 25 Cal. 492; Vick v. Smith, 83 N. C. 80; Kerr v. Lydecker, 51 Ohio St. 240, 37 N. E. 267, 23 L. R. A. 842; 15 Am. & Eng. Ency. Law (1st Ed.), 869; Balch v. Arnold, 9 Wyo. on page 36, 59 Pac. on page 438; Crawford v. Hazelrigg, 117 Ind. 69, 18 N. E. 603, 2 L. R. A. 139; Dumell v. Terstegge, 85 Am. Dec. 466.) To this latter case is appended a monographic note, containing a large collection of cases, and a full discussion of the above principles.
This general rule is modified to the extent that a court of equity will, on the presentation of a proper case, protect the intervening rights of third parties, and that the’parties to the mortgage may, at the time of renewing the note, by express agreement, or a plain manifestation of a contrary intention, negative the presumption that the renewal of the note renews the mortgage lien; but the burden of proof is on the party asserting such proposition fi> show that it was not the intention that *441such renewal of the note should renew or extend the mortgage. (Brown v. Dunckel, 46 Mich. 29, 8 N. W. 537; Oliphint v. Eckerley, 36 Ark. 69; Vick v. Smith, supra; California Bank v. Brooks, 126 Cal. 198, 59 Pac. 302; Barber v. Babel, 36 Cal. 11.)
4. At the time defendants executed the second mortgage, on January 20, 1888, to secure the payment of the note of that date, and of the note dated December 20, 1886, there was some discussion relative to the former mortgage, and the defendants were asked to give a new mortgage covering the same property described in the first mortgage. Mrs. Pickering refused to execute such new mortgage, and John Gr. Pickering refused to execute the same for the reason that his wife would not join him; but at the same time he requested the plaintiff to bring suit to foreclose this first mortgage. The facts presented in the agreed statement are not of themselves sufficient as a matter of law to repel the presumption that it was the intention of the parties that the execution of the new note and the new mortgage on other property should extend the lien of the former mortgage.
No question is raised with reference to the inchoate interest of the wife in the trust estate under the deed from the railroad company to Kleinschmidt. We therefore do not discuss that question.
On a consideration of the whole case, we are of the opinion that the judgment appealed from should be reversed, and the cause remanded, with direction to the district court to grant a new trial.
Pee Cueiam. — Por the reasons given in the foregoing opinion, the judgment is reversed, and the cause remanded for a new trial.