There are certain established rules of evidence-by which the rulings of the circuit judge on the trial rejecting or admitting testimony must be tested. These will be stated and briefly considered.
1. It is settled that the rule by which the damages to-plaintiffs’ land adjoining the defendant’s railway is to be determined, is the depreciation of the market value of such land caused by the construction and operating of the railway through their farm, less any special benefits which may thereby accrue to the plaintiffs. Also that witnesses, may, after stating the amount of depreciation, testify as to the elements or items which make up that amount. In other words, they may state their grounds or reasons for fixing the damages at the specific sum named by them.. *521The admissibility of testimony of the character last mentioned was first asserted in this state in Snyder v. W. U. R. R. Co., 25 Wis., 60, under the qualifications and restrictions stated in the opinion written by the present chief justice. One of these qualifications is that if such testimony has been received, the same'should not be submitted to the jury as a basis for their assessment of damages. Because such testimony was so submitted in Hutchinson v. C. & N. W. R'y Co., 37 Wis., 582, the judgment was reversed. The opinion by the late chief justice in that case so clearly states the nature and extent of the decision in Snyder v. W. U. R. R. Co., and the grounds for admitting, and the effect of, the kind of testimony under consideration, that we are justified in quoting from it somewhat at length. It is there said: “ The rule in Snyder v. W. U. R. R. Co. is that the measure of damages is the actual depreciation in value as established in evidence, exclusive of all remote, fanciful, or speculative injuries; but that, in order to account for and support their opinion of depreciated value, the witnesses who prove it may be permitted to state all causes of injury which they believe go to make up the depreciation to which they testify. But these do not go as evidence to the jury to assess damages upon, but only as means by which the jury can estimate the value of the evidence of depreciated value. This is not distinction without difference; it is a practical and important one. The witnesses who are permitted to state the grounds of their judgment, are subject to cross examination, and their judgment to criticism; there is some safety in permitting thém to speculate on the causes' of depreciation. But to admit evidence of remote and conjectural sources of injury for the jury to consider and assess damages upon, without restraint or scrutiny, would be going outside of all safe rule and plunging into the abyss of wild and supposititious damages. We think that Snyder's Case went fully as far as it is safe to go,— farther, perhaps, than *522they go elsewhere (Presbrey v. O. C. & N. P. R'y Co., 103 Mass., 1; Sunbury & E. R. R. Co. v. Hummell, 27 Pa. St., 09);- — -and we are not disposed to go beyond it. Witnesses may testify to depreciation and be permitted to state the grounds of their opinion, as in Snyder's Case; but evidence of remote and conjectural causes of depreciation should not be submitted to the jury as a basis for their assessment of damages.” Page 610. See S. C., 41 Wis., 541.
It will be observed that such testimony cannot properly go to the jury as the basis for an assessment of damages, but only as aiding the jury to determine the weight they ought to give to the direct testimony of depreciated value. Its sole function is to strengthen the testimony of the witnesses on that subject. Ordinarily such testimony is inadmissible on behalf of the party who produces the witness. It is the function of a cross examination thus to test the grounds and value of the testimony. But, for reasons satisfactory to the court, it was determined that the party might, in this class of cases, test the value of the testimony of his witness by a sort of cross examination. The rule, however, is exceptional, and, as intimated in Hutchinson v. C. & N. W. R'y Co., supra, should not be extended. The privilege thus accorded the plaintiff is very liable to abuse, to prevent which it is necessary that the trial court should have a liberal discretion in the matter of admitting or excluding such testimony. Indeed, were the court to exclude it entirely, it is not clear that it would be error. We do not decide that proposition, but because such testimony is only collateral to the real issue in the case; because it partakes largely of the nature of cross examination; because its admission in this class of cases is exceptional; and more especially because its uncontrolled admission may raise numerous side issues on collateral matters, thus leading to great abuses,— we hold that the trial court may, in its discretion, limit and control the extent to. which such testimony shall be received, just as *523the court may always do in the investigation of any matter which is merely collateral to the issue. It necessarily follows that nothing short of an abuse of discretion in that behalf will work a reversal of the judgment. A considerable number of the questions propounded in this case to the witnesses by the plaintiffs, to which the court sustained objections, called for testimony relating only to the grounds or reasons upon which those witnesses fixed the depreciation in the value of plaintiffs’ farm by reason of the construction of the railroad through it. We do not think that any of these rulings involve any abuse of a sound discretion.
2. Any damages to the land of plaintiffs, caused by an improper construction of a railroad, cannot lawfully be included in the assessment. This proposition was held in Lyon v. G. B. & M. R'y Co., 42 Wis., 538. It is there said: “When the damages to such contiguous lands are appraised by the commissioners before the railroad is constructed, the appraisal should be made with reference to the effect upon them of the railroad when properly constructed. If the appraisal is not made until after the railroad is constructed, it should, we think, be made on the same basis. If it is properly constructed, its actual effect upon the contiguous lands .should control the appraisal; but if improperly or negligently constructed, no additional damages should be given for that reason. The remedies of the land-owner in such a •case are to compel the company, by appropriate judicial proceedings, to construct its road in a proper manner, or, by a •common law action, to recover damages for its failure to do so.” Some of the questions to which the court sustained objections called for estimates of damages of that character, and such testimony was clearly inadmissible.
3. Many of the questions called for facts within the [knowledge of the jury, who, by order of the court, bad viewed the premises, and who knew the facts called for as well as the witnesses could have known them. Other ques*524tions called for the opinions of witnesses in respect to matters concerning which the jury could form an opinion as intelligently as could the witnesses. Opinions in such cases-are entirely outside the range of authorized expert testimony. These rules are elementary, and they justify very many of the rulings of the circuit judge. A" few of the rejected questions were answered in other portions of the testimony, and some of them seem immaterial. It would be a profitless task to discuss each interrogatory in this opinion. It-must suffice to say that they have been carefully considered, in the light of the above rules of evidence, and our conclusion is that each of the material questions to which an objection was sustained, contravenes one or more of those rules, or was properly ruled out by the court in the exercise of a sound legal discretion.
4. The objections by plaintiffs to questions put to their witnesses on behalf of defendants, by way of cross examination, were properly overruled. These questions were clearly competent. At least, it was within the discretion of the court to permit them to be put on cross examination.
5. The objection that ex-Gov. Taylor, and other witnesses for defendant, were not competent witnesses to testify to the value of plaintiffs’ farm, and the depreciation in such value caused by the railroad, is not well taken. The bill of exceptions does not contain all of the evidence. Hence, were it silent on the subject, we should be bound to presume, in support of the ruling allowing them to testify, that it was made to appear that they were duly qualified witnesses in that behalf. Enough appears in the bill, however, to show that they possessed the requisite knowledge of the farm and its value to make them competent witnesses in respect thereto.
Upon the whole case we conclude that the judgment of the circuit court must be affirmed.
By the Court.— Judgment affirmed.