McClain, J.
1 *922 *90The motion for a new trial was sustained, as appears from the written opinion filed by the judge, on account of the action of the court in sustaining the •objection to certain questions propounded to nlaintifPs witness and objected to as incompetent. This witness was the head brakeman of the train in connection with which Quinlan was employed at the time of the accident, and it appears that at that time witness was controlling the motions of the train by means of signals to the engineer, for the purpose of having some cars kicked off upon a switch, from which cars Quinlan fell, and received the injuries resulting in his ■death. The witness testified that Quinlan climbed upon these cars, while the train was being backed, for the purpose -of throwing the rear cars upon a switch, and while witness was attempting to uncouple these cars; that witness failed to ■effect the uncoupling; and that, when the signal to stop the train was obeyed, the cars were checked with a jerk, and Quinlan, who stood either erect or leaning over on top of 'the rear car near one corner of it, was thrown to the ground. It was proper for plaintiff to show that deceased was at the place where he was standing on top of the car in the proper •discharge of his duties, not only in order to disprove contributory negligence, which was a question in issue, but also for the purpose of attempting to show that the witness was negligent in his conduct, in view of the danger to deceased which was involved in the discharge óf his duties. The following questions, with such answers as appear in the record to have been allowed to be given, were asked, and to those not answered the objection that they were incompetent was sustained in each instance: “Tell the *91jury Avliat Quinlan’s duties were on top of the car.” “Tell the jury, if you knoAV, what Quinlan’s duties Avere on top •of that car.” “Tell the jury what Quinlan was on top of that car for.” “Tell the jury for Avhat purpose Quinlan Avas on top of that car.” “What Avas he there for ?” “Do you knoAV Avliat his duties Avere on top of the car at any time ?” “If the car had been detached when the train stopped, and had gone back and the kicked switch made, what were Quinlan’s duties then Avith reference to stopping the’ car ?” “If the car had been kicked in'there as you intended, Avhat were Quinlan’s duties Avith reference to setting that brake, and endeavoring to stop the car from running into those other cars, when the kick Avas made ?” “If the switch had been made as you came to it, and the brake had not been set, Avhat would have occurred to this car that Avas being kicked in there colliding with the cars that stood on the house track? Ans. It may have run down to the cars. May have hit the cars a little; that is,, if it had gone in the Avay I intended it to.” “What were Quinlan’s duties standing on that car as it was being kicked in, as to setting that brake and preventing the collision?” “State what was the custom in making a kick of this kind, and putting a car in that manner in on the switch, as to somebody being with the car and setting the brake. Ans. The man generally catches the car that is kicked.” The witness then said: “It is all right for him to be on the car when it is being kicked. Tie Avatches the car, and Avhen it gets to where he wants it he stops it by setting the brake.” It Avas for error in these rulings that the motion for new trial Avas sustained. Appellant contends that these questions Avere improper, and that the original ruling sustaining the objections to them was correct. TIis contention is that they call for conclusions of the witnesses as to Quinlan’s duty at that particular time, and not for his testimony as an exnert as to the general nature of Quinlan’s duties and his ordinary and customary Avork. ' The general rule as to Avhat is admissible in this respect on the part of expert witnesses under such *92circumstances is thus clearly stated, and is supported by authority cited, especially the cases of Belair v. Railway Co 43 Iowa, 662; Allen v. Railway Co., 57 Iowa, 623; Muldowney v. Railway Co., 36 Iowa, 462; Jeffrey v. Railway Co., 56 Iowa, 546; Hamilton v. Railway Co.. 36 Iowa, 36. Appellee does not question the correctness of this distinction, but- contends that the questions asked were not open to the-objection urged*, and we think that in this contention the appellee is corrept. While the question is not one which is-free from doubt, we are thoroughly convinced that the meaning intended to- be conveyed to the witness by the question and the understanding which the witness must have had of their meaning, were-that he should state the general purpose for which a brakeman, under the circumstances, would go upon the top-of the car, and stand near the corner of it, where the brake was situated, while the cars were being backed for the purpose of kicking them upon a switch, and that the answers to such questions would have been competent evidence for the-purpose of showing that deceased was in a proper place, and that the witness had reason to know that he was properly at that place, preparing to do an act which was proper in itself,, although it might subject him to danger. In support of our construction of these questions, see Czezewzka v. Railway Co., 121 Mo. 201 (25 S. W. Rep. 911) ; Railroad Co. v. Smith, 22 Ohio St. 227, 246; Howland v. Railway Co., 115 Cal. 487 (47 Pac. Rep. 255); Reifsnyder v. Railway Co., 90 Iowa, 76; Railroad Co. v. Dorsey, 68 Ga. 228, 235. Putting this construction upon the questions, the court should not have sustained the objections, but should have-allowed the questions to be answered. 'Therefore the court’s-refusal to allow them to be answered was error for which a new trial was properly granted, unless, as is contended by appellant, the ruling was error without prejudice.
*93;3 *92With reference to the question of prejudice, appellant contends that, in the first place, it does not appear what; *93.answers it was expected to elicit, and therefore, under the doctrine that prejudice must appear, we cannot presume that any detriment resulted to the plaintiff. A doctrine such as that contended for has been frequently announced by this court, but we think not under such circumstances as appear in this case. Of course, where the object for which the questions are asked is not apparent, but it is sought thereby to establish collateral facts, the materiality of which is to be afterwards shown, counsel must state what he expects to prove, and in what way the ■facts sought to be elicited will become material; otherwise, the sustaining of the objection to his question will be error without prejudice. Jenks v. Mining Co., 58 Iowa, 549; Gronan v. Kukkuck, 59 Iowa, 18; Mosier v. Vincent, 31 Iowa, 478. It must be conceded that the language used in these cases does not indicate any limitation on the general proposition that, unless the nature of the answer to be ■elicited appears in the record, the exclusion of the evidence will be deemed to have been without prejudice; but we feel bound to say that in this respect the language used goes too far. There'is another proposition equally well established by the authorities, that, where error appears, it will be presumed to have been prejudicial, unless want of prejudice ■appears from the record itself. Potter v. Railroad Co., 46 Iowa, 399; George v. Railroad Co., 53 Iowa, 503; Strobhel v. Moser, 70 Iowa, 126.
In this instance we find that the questions called for evidence the materiality and competency of which were plainly apparent, and therefore there was error in sustaining the •objections. The presumption of error arises, and this presumption is not in any way overcome, unless, as appellant finally contends, the facts sought to be elicited were established by answers which the witness was allowed to give or by other evidence in the case. We did not find, however, elsewhere in the record, any evidence which clearly determines in favor of the plaintiff *94the facts which were sought to be shown by the asking of these questions, and we are therefore of the opinion that the action of the trial court in sustaining the motion for a new trial must be affirmed.
We cannot accede to the further contention of appellant, that, whatever might have been the answers to these questions, the plaintiff would, under the evidence, have been unable to recover. There was a question of fact for the jury, and it is not for us to say what influence this evidence, if admitted, would have had on the result. — Aeeirmed.