after stating the case as above, delivered the opinion of the court.
The difference between causes of action at law and in equity is matter of substance, and not of form. In the national courts the in*854eradicable distinction between them is as sedulously preserved in the forms and practice available for their maintenance as it is in the natures of the causes themselves and in' the principles upon which they rest. A legal cause of action may not be sustained in equity, because there is an adequate remedy for the wrong it presents at law, and it is only when there is no such remedy that a suit in equity can be maintained. Equitable causes and defenses are not available in actions at law, because they invoke the judgment and appeal to the conscience of the chancellor, and the free exercise of that judgment and conscience is forbidden in actions at'law by the rule which entitles either party to a trial of all the issues of fact by a jury. In the federal courts an action at law cannot be maintained in equity, nor is an equitable cause of action or an equitable defense available at law. Bagnell v. Broderick, 13 Pet. 436, 10 L. Ed. 235; Foster v. Mora, 98 U. S. 425, 428, 25 L. Ed. 191; Scott v. Armstrong, 146 U. S. 499, 512, 13 Sup. Ct. 148, 36 L. Ed. 1059; Lindsay v. Bank, 156 U. S. 485, 493, 15 Sup. Ct. 472, 39 L. Ed. 505; Schoolfield v. Rhodes, 82 Fed. 153, 155, 27 C. C. A. 95, 97; Davis v. Davis, 72 Fed. 81, 83, 18 C. C. A. 438, 440.
The parties to this action framed their pleadings and argued this case in utter disregard of the long established rule to which we have adverted. The plaintiff pleaded a perfect cause of action in ejectment, and prayed for possession of the premises' and an injunction against their continued use by the defendant. The defendant, by its answer, admitted that it had unlawfully entered upon the premises in dispute, and denied nothing essential to the maintenance of the plaintiff’s action but his ownership of the property. Plaintiff proved his title, and rested. Defendant then offered to prove the value of the strip of land on which its tramway rested. The court refused to permit it to do so, and instructed the jury to return a verdict for the plaintiff. The judgment upon that verdict is presented for our consideration by writ of erro'r. If the pleadings in this action had been carefully examined at the opening of the trial, a grave doubt might have arisen whether this was an action at law or a suit in equity. But the subsequent proceedings of the parties have settled that question. One who consents to the hearing in equity of a legal cause of action, or to ,the trial of an equitable cause of action at law, is thereby estopped from successfully objecting for the first time in an appellate court to the method of trial which he adopted. Schoolfield v. Rhodes, 27 C. C. A. 95, 99, 82 Fed. 153, 157; Hooven, Owens & Rentschler Co. v. John Featherstone’s Sons, 111 Fed. 81, 86, 49 C. C. A. 229, 234; Preteca v. Land Grant Co., 1 C. C. A. 607, 50 Fed. 674; Railway Co. v. Harris, 12 C. C. A. 598, 601, 63 Fed. 800, 803; Railway Co. v. Phillips, 13 C. C. A. 315, 319, 66 Fed. 35, 40; Tyler v. Savage, 143 U. S. 79, 12 Sup. Ct. 340, 36 L. Ed. 82; Reynes v. Dumont, 130 U. S. 354, 395, 9 Sup. Ct. 486, 32 L. Ed. 934; Scott v. Armstrong, 146 U. S. 499, 512, 13 Sup. Ct. 148, 36 L. Ed. 1059; Hollins v. Iron Co., 150 U. S. 371, 14 Sup. Ct. 127, 37 L. Ed. 1113. The defendant consented to the trial of its case at law and by a jury, and it is now too late for it to claim that this was a suit in equity. Moreover, it has brought the case to this court by a writ of error, and not by an *855appeal. The acts of congress give to defeated litigants in the national courts the right to a review of final judgments at law against them by writs of error and a right to a review of final decrees in equity by appeals. These acts grant the power and fix the jurisdiction of the federal appellate courts. A decree in equity cannot be reviewed by a writ of error, nor can a judgment at law be challenged by an appeal. Rev. St. § 699; Hooven, Owens & Rentschler Co. v. John Featherstone’s Sons, 111 Fed. 81, 86, 87, 49 C. C. A. 229, 234, 235; McCollum v. Eager, 2 How. 61, 11 L. Ed. 179; Sarchet v. U. S., 12 Pet. 143, 9 L. Ed. 1033; Ballance v. Forsyth, 21 How. 389, 16 L. Ed. 143; Walker v. Dreville, 12 Wall. 440, 20 L. Ed. 429; Bondurant v. Watson, 103 U. S. 278, 26 L. Ed. 447; Ex parte Ralston, 119 U. S. 613, 7 Sup. Ct. 317, 30 L. Ed. 506; Stevens v. Clark, 62 Fed. 321, 323, 10 C. C. A. 379, 381. The defendant, by trying its case to a jury as an action at law, and by bringing it to this court by writ of error, is es-topped from claiming that the action was a suit in equity; and the questions it presents must be heard and decided in this court in accordance with the rules of law applicable to the method of trial adopted below and to the method of review which the plaintiff in error has chosen.
A writ of error challenges the rulings of the trial court upon questions of law, and those rulings only. The only complaint of the action of the court below is that it refused to permit the defendant to prove the value of the strip of land occupied by the tramway, and that it instructed the jury to return a verdict for the plaintiff. The admissions of the answer and the patent which the plaintiff offered in evidence conclusively established his right to1 the possession of the premises in the absence of countervailing evidence. Counsel for the defendant invoke the rule that, where the owner of land has knowingly permitted a corporation that is entitled to exercise the right of eminent domain to construct and put in operation its railway, tramway, or other, improvement upon his property, he is thereby estopped from recovering possession of the property occupied, and is restricted to his judgment for just compensation. Buckwalter v. Railway Co. (Kan.) 67 Pac. 831, 832, and cases there cited. Conceding, without deciding, the soundness of this rule, and its applicability to the case at bar, there are two insuperable objections to a reversal of this judgment on its account. In the first place, the estoppel upon which counsel relies is an equitable, and not a legal, one. It is not an estoppel of record, but an estoppel in pais. The defense which he founds upon it is not a defense at law, but a defense in equity; and an equitable defense, as we have seen, is not available in the federal courts in an action at law. The remedy of the defendant is a bill in equity to restrain the action at law until the equities of the defendant can bé considered. In Bagnell v. Broderick, 13 Pet. 436, 10 L. Ed. 235, which was an action of ejectment in which equitable titles were pleaded in defense, the supreme court said: “The equity side of the circuit court is the proper forum, and a bill the proper remedy, to investigate the equities of the parties.” And in Foster v. Mora, 98 U. S. 425, 428, 25 L. Ed. 191, that court declared: “In actions of ejectment in the United States courts the strict legal title prevails. If there are equities *856which would show the right to be in another, these can only be considered on the equity side of the federal courts.” In the second place, under the statutory practice in actions at law in the state of Utah, the equitable defense which was pleaded in the answer stood denied. 'Rev. St. Utah 1898, § 2981. It was not established by the evidence, and the record contains no offer to establish it; The defendant offered to prove nothing but the value of the strip it was occupying. The bill of exceptions does not disclose upon what ground the court refused to permit the introduction of this evidence, and in this state of the case, if there was any ground upon which its ruling could, have been legally sustained, the presumption is that it rests upon that basis. That ruling may well have been sustained upon the ground that there had been no: evidence offered or introduced to establish the proposition that it was necessary for the defendant to use the premises it was occupying, or any part of the property of the plaintiff, for the purpose of conducting its mining and smelting operations. It is always an indispensable prerequisite of the right to exercise the power of eminent domain over the property of an owner of real estate to show that it is necessary to use his property to carry on the business of the quasi public corporation which seeks it. Mining Co. v. Seawell, 11 Nev. 394; Mining Co. v. Corcoran, 15 Nev. 147, 154. There was no proof, and no offer of proof, that it was necessary to use any portion of the property of the plaintiff to conveniently conduct the business of the defendant. In the absence of this and other evidence which would warrant this company in exercising its right of eminent domain, if it has that right, there was no error in the refusal of the court to permit it to prove the value of this property, nor in its instruction to the jury to return a verdict for the plaintiff. The mere acquiescence of the owner of property in the continuing trespass of a wrongdoer does not deprive him of his right to maintain ejectment for the possession of his property at any time within the limit prescribed for such actions by the statutes of his state. The value of the property was not relevant to the plaintiff’s claim for damages, because he had withdrawn that claim.
There was no error in the trial of this case, and the judgment below is affirmed.