(after stating the facts). The defendants Dalton and Hardin had leased a coal mine, together with its mining machinery and equipment, from the defendants "Ward, McWilliams and Clark, and agreed to pay them a royalty at the rate of 75 cents per ton for all coal taker from the mine hy them. They -wrongfully mined 4,005 tons of coal on an adjoining tract belonging to the plaintiff, and paid the royalty on this coal to their lessors.

Under these circumstances the defendants Dalton and Hardin were trespassers, and, the tort having been waived hy the plaintiff, it had a right to sue Dalton and Hardin for the value of the coal taken hy them. To entitle the plaintiff to a judgment against Ward, McWil-liams and Clark, the lessors of Dalton and Hardin, it must not only appear that they were landlords of Dalton aud Hardin, who took the coal, hut also that they participated in some way in the act of going into the plaintiff’s land to get it. In other words, it must appear that the defendants acted in concert in committing tlie trespass complained of, or that the lessors in some way aided and assisted their lessees to actually commit the trespass. This is in application of the well-known rule that, to render one man liable in trespass for the acts of others, it must appear either that they acted in concert or that the act of the individual sought to be charged ordinarily and naturally produced the acts of the others. Offerman v. Starr, 2 Pa. St. 394; Bard and Wenrich v. Yohn, 26 Pa. St. 482; and Dundas v. Muhlenberg's Executors, 35 Pa. St. 351.

On the part of the plaintiff it was shown that McWil-liams, acting for himself and Ward and Clark, told Hardin, one of the lessees, to go ahead and mine the coal which is the subject of the controversy in this case. This fact was testified to by James ¡Hardin. Hardin said that McWilliams told him to go ahead and take the coal out between their mine and the Sunshine mine. McWilliams said that the Sunshine mine could not get to the coal in question, and, for that reason, told him to take the whole thing out. On the other hand, McWilliams denied having told Hardin to take out the coal in question, and said that he did not know anything about it until the plaintiff demanded payment for the coal taken, which was some time after the royalty had been paid them for the coal taken.

The .chancellor found the issues on this point in favor of the plaintiff, and it cannot be said that his finding is against the weight of the evidence. Hence it may be said to be established that McWilliams and his associates acted in concert with Dalton and Hardin in taking out the coal in question, or at least advised them to mine. Therefore, under the principles of law above announced, they became jointly liable to the plaintiff for the value of the coal taken.

The measure of damages in an action for unlawfully extracting ore from the premises' of another depends upon whether the invasion of the premises was through inadvertence or honest mistake, or was willful. If the trespass is the result of an honest mistake, the defendant is compelled to pay only the value of the ore as it was when originally in place in the ground. If, on the other hand, the defendant takes out the ore wilfully and intentionally, he must pay the value of the ore as found at the mouth of the mine. Lindley on Mines, 3 ed., vol. 3, par. 868; Hall v. Abraham 44 Ore. 75 Pac. 882; Central Coal & Coke Co. v. Penny 173 Fed. 340; Resurrection Gold Min. Co. v. Fortune Gold Min. Co. 129 Fed. 668; Lyons v. Central Coal & Coke Co. 239 Mo. 626, 144 S. W. 503; and Ege v. Kille, 84 Pa. 333.

The measure of damages for wrongfully taking ore from the la.nd of another, through mistake or in good faith, is the value of the ore in place in the mine. The wrongful taking of the ore raises a presumption of fact that the trespasser took it intentionally and wilfully, but this presumption may be overcome by the evidence in the case.

As we have already seen, the chancellor accepted the evidence for the plaintiff on the question of McWilliams and his associates advising their lessees to mine the ore in controversy. James Hardin, one of the lessees, was the witness who testified for the plaintiff on this point. His evidence establishes the fact that his lessors and the plaintiff both operated mines on adjoining forty-acre tracts of land. His lessors had been mining the ore themselves, and, in consequence, knew the direction of the vein they were mining. They knew that they were near the boundary line of their own mine, and it is fairly infer-able from the testimony of Hardin, taken as a whole, that they thought the vein would run out by the time their boundary line was reached, or, in any event, soon after-wards; that they did not believe that it would be practicable for the plaintiff to mine the coal in question.

Under these circumstances, we think that, while the defendants were trespassers, they were innocent trespassers within the meaning of the rule relative to the measure of damages, and that they took the coal inadvertently, or in the honest belief that they had a right to do so. Hence they were only liable for the value of the coal as it lay in the ground.

It results from the authorities cited above that such value depends upon the position and circumstances of each particular mine, on the quality of the ore, the cost of mining and preparing it for market, its proximity to the places where it is to be used or sold, and on the facilities for transportation.

On these points there is a lack of evidence in the record. The chancellor allowed 75 cents per ton on the ore taken as its value. There is nothing in the record to show where he got this value, unless it is the royalty provided for in the lease between McWilliams and his associates and Dalton and Hardin. The royalty in this lease cannot be considered under the circumstances of this case as a proper method in arriving at the value of the ore in the ground. The work of mining is one of magnitude, and requires a considerable outlay of money. In this case the lessors had mining machinery and equipment of the value of $35,000. They had also expended several hundred dollars in track-laying. These outlays were proper matters to be considered in fixing the royalty they were to receive in leasing their mine. Hence the royalty provided for in the lease could not be considered as a proper method of ascertaining the value of the coal as it originally lay in the ground.

On the other hand, there was evidence in the record which tended to fix the value of the coal in the ground. The plaintiff and the defendants were coal operators. The evidence in the record tends to show that the royalty usually paid in that locality for mining* coal, where the machinery and equipment was not considered, was ten cents for slack coal and fifteen cents for hard coal. This evidence is not disputed, and should have been taken by the chancellor in fixing the value of the coal taken. The coal taken amounted to 4,005 tons. It is fairly inferable that it was hard coal. The value of the coal taken amounted, in round numbers, to $600.

Interest on the value of the coal in place at the time of the conversion was properly directed to be allowed. It is as necessary a part of complete indemnity as the value itself. It has always been the law of this State that interest from the time of conversion, in addition to the value of the property converted, is allowed as damages. The coal in question was taken in November and December, 1920. The trial Was had on the 19th day of December, 1923. Interest on $600 for three years at six per cent, would amount to $108.

The result of our views is that the measure of damages is the value of the coal in place at the time of the conversion, which we have found to be $600, with interest up to the time of the trial, amounting to $108. Therefore the decree of the chancei’y court must be reversed, and a decree will be entered here for $708, with interest at six per cent, from the 19th day of December, 1923.

It is so ordered.