The main question upon the trial was whether the defendant’s dam did injuriously affect the plaintiffs’ water privilege. The learned trial court, as we learn from the opinion, was satisfied that since the erection of the defendant’s dam the plaintiffs’ water privilege has been injuriously affected by back-water. The testimony in support of this contention is practically uncontradicted, and amply justifies the statement of the learned judge that “since the erection of defendant’s dam, in 1882 or 1883, there has been some increase in the depth of the water at plaintiffs’ mills.” This increase appears to have been constant, and its effect was to impair the efficiency of plaintiffs’ water-power and mills. But the trial court found that the plaintiffs had not shown that this increased depth of water was caused by defendant’s dam. Expert witnesses on the part of the defendant testified that it was an “hydraulic impossibility” for it to be so caused. Expert witnesses on the part of the plaintiffs did not specifically testify to the contrary opinion. They testified that they discovered no other cause than the defendant’s dam, and, in substance, that this case demonstrated itself, since the rise of the water followed the erection of the dam so closely as to be convincing that the dam was the cause. The conclusion of the trial court has the support of the testimony of defendant’s experts, and we cannot demonstrate that it is erroneous. It is easy to assume certain propositions respecting the slack water *656in the defendant’s dam acting as an obstruction to the flow of the water from above; as that the retardation of the flowing volume by the slack water at the point of impact causes the flowing volume to flow more slowly immediately above that point, and that the retarded current itself becomes at every point up the stream a new obstruction, retarding the flow above it; and that, this continuing to the plaintiffs’ tail-race, would cause the obstruction there. Now, conceding that under certain conditions the phenomenon called the “piling” of water in a flowing stream exists, the conditions which would produce such a result are not so definitely and clearly understood as to enable the judge or juror, in the absence of assistance from expert testimony, to decide correctly respecting its existence or non-existence in a case like this. It may be that the knowledge of the so-called “experts” upon the subject cannot be greatly relied upon when they pass from theoretical propositions to their concrete application. Be this as it may, the burden rested upon the plaintiffs to prove their case, and that required them to show that the defendant’s dam was the cause of the back-water at the tail-race of their mills. This they did not do, and hence the judgment must be affirmed. Judgment affirmed, with costs.
Learned, P. J., concurs.