Crownhart, J.
It devolved upon the appellants herein to establish their case by. a preponderance of the evidence. If they did this, even though the evidence was that of experts, such evidence could not be disregarded by the court unless it was in some way impeached. It seems that the testimony of appellants’ expert witnesses was not impeached in any manner. Instead of its being contradicted, as to the children it was in substance agreed to by the only expert produced by the defendant who' had any experience with monoxide gas poisoning and who was qualified to testify. He testified to facts which would justify a conclusion of the court that the children survived the father. As we view this case the evidence is practically undisputed, and only one conclusion can be drawn from the evidence if we are to give the expert evidence any weight, and that is that the children and the mother survived the father. That the children survived the father all the expert evidence is in *146agreement. The trial court evidently disregarded the expert testimony, following the rule often laid down that such evidence is to be viewed with caution and may be disregarded altogether where it conflicts with the common knowledge of judge or jury. Baxter v. C. & N. W. R. Co. 104 Wis. 307, 80 N. W. 644; Ladwig v. Jefferson Ice Co. 141 Wis. 191, 124 N. W. 407. Language used in the Baxter Case lends some support to the action of the court in disregarding the opinion evidence in this case. However, there is a class of expert testimony that is competent, worthy of consideration, and which cannot be ignored by the trial court or jury, and that is the evidence of those persons who, by reason of special study and experience, possess knowledge and judgment not possessed by mankind in general. Our Reports contain many cases where such evidence has been considered of much probative force. See U. S. H. Co. v. Jenss, 128 Wis. 162, 107 N. W. 293. Where expert testimony is properly admitted it must be weighed and considered as other, testimony. In this case there were many physical facts which the judge might consider together with the expert testimony. Rut without expert testimony the cause would have been left wholly in the dark. It was only by respondent’s expert witness that the cause of death was determined. The size of the room in which the deaths occurred, the location of the entry of the poisonous gas, the location of the bed and the position of the bodies thereon, the age of the decedents together with their physical conditions, were physical facts established in the case. But the effects of monoxide gas on different persons when inhaled, its relative weight and its diffusion with the air, the probable currents of air following the heat that came from the hot-air register, were properly matters of expert testimony. None but experts could know the effect of monoxide gas on the human system or how it would affect different persons under different circumstances. We consider that *147the trial judge was bound by such expert testimony in the absence of anything tending to impeach it. The evidence being substantially all one way, the duty of the court was to find accordingly.
By the Court. — The judgment of the county court is reversed, with directions to enter judgment in favor of the appellants.