Opinion,
Mr. Justice Mitchell :The dividing line between the right to use one’s own, and the duty not to injure another’s, is one of great nicety and importance, and frequently of difficulty. The Pennsylvania decisions have endeavored with unusual care, to preserve the substance of both rights, as far as their sometimes inevitable conflict may permit.
With regard to the use and control of flowing water, and of water-courses, the case of Penna. Coal Co. v. Sanderson, 113 Pa. 126, definitively settled the rule that for unavoidable damage to another’s land, in the lawful use of one’s own, no action can be maintained. No other result seems possible, without restricting the uses, derogating from the full enjoyment, and diminishing the value of property. But the rule does not go beyond proper use and unavoidable damage. It is thus clearly expressed in the opinion of our Brother Clark: “ Every man has the right to the natural use and enjoyment of his own property; and if, while lawfully in such use and enjoyment, without negligence or malice on his part, an unavoidable loss occurs to his neighbor, it is damnum absque injuria:” 113 Pa. 146. That this is the rule as to surface streams was conceded by the defendant below; but it contended that as to subterranean waters, or at least, as to percolations and hidden streams, an owner was not bound to pay any attention to the effect of his *157operations within his own land, upon the land of others. The learned judge below, though seeing and expressing the force of the reasons for a uniform rule applicable to both classes of waters, felt himself so far constrained by adjudicated cases that he directed a verdict for the defendant. W e have therefore to examine the cases, to see what the true distinction is between surface, or visible, and subterranean waters, and whether different principles are applicable to the rights in them, respectively, or the same principle, with only such modifications as may be necessary in practical application.
In Wheatley v. Baugh, 25 Pa. 528, the plaintiff had a spring upon his property, which he had used in his tannery for more than twenty-one years, when defendant opened a mine on his adjacent land, and put in a steam-pump to take out the water, with the result of drying up the plaintiff’s spring. It was held that plaintiff had no cause of action. This case settled the law on the subject of percolating waters, and has not since been questioned. It was followed in Haldeman v. Bruckhart, 45 Pa. 514, but was re-stated rather narrowly by Justice Strong, thus: “In that case it was ruled that where a spring depends for its supply upon filtrations or percolations of water through the land of an owner above, and, in the use of the land for mining or other lawful purposes, the spring is destroyed, such owner is not liable for the damages thus caused to the proprietors of the spring, unless the injury was occasioned by malice or negligence. To such percolations or filtrations, then, the inferior owner has no right. This was all that was necessary to the decision of the case.” He then criticises the rest of the opinion in Wheatley v. Baugh as dictum, and formulates the rule again in the following terms: “ A proprietor of land may, in the proper use of his land for mining, quarrying, building, draining, or any other useful purpose, cut off or divert subterraneous water flowing through it to the land of his neighbor, without any responsibility to that neighbor.” These forcible statements of the rule are, as I apprehend, the main ground of the contention on behalf of the defendant in the present case, that an owner is not bound to pay any regard to the effect of his operations on subterranean waters. But this contention overlooks the qualification made in all the cases, that there must be no negligence. The opinion of Chief Justice Lewis in Wheatley v. Baugh is as able, elab*158orate, and convincing a discussion of the subject as can be found reported, and in it the necessary and unavoidable character of the damage is explicitly insisted on: “ When the filtrations are gathered into sufficient volume to have an appreciable value, and to flow in a clearly-defined channel, it is generally possible to see it, and to avoid diverting it without serious detriment to the owner of the land through which it flows. But percolations spread in every direction through the earth, and it is impossible to avoid disturbing them without relinquishing the necessary enjoyment of the land: ” Page 532. “The owner of a spring, although his right is imperfect where the supply is derived through his neighbor’s land, has nevertheless a privilege subordinate only to the paramount rights of such neighbor; and it is only when the fair enjoyment of those paramount rights requires its destruction that he is bound to submit to the deprivation: ” Page 535. And even in Haldeman v. Bruckhart, which is the most strongly expressed of all the decisions in favor of the rights of the proprietor on his own land, it is clear that the same qualification is not lost sight of, although not prominently put forward. “ A surface stream,” says Strong, J., “ cannot be diverted without knowledge that the diversion will affect a lower proprietor. Not so with an unknown subterraneous percolation or stream. One can hardly have rights upon another’s land which are imperceptible, of which neither himself nor that other can have any knowledge.....These appear to us very sufficient reasons for distinguishing between surface and subterraneous streams, and denying to inferior proprietors any right to control the flow of water in unknown subterranean channels upon an adjoiner’s land. They are as applicable to unknown sub-surface streams as they are to filtrations and percolations through small interstices.” And in Lybe’s App., 106 Pa. 634, it is said: “ The rule is that, wherever the stream is so hidden in the earth that its course is not discoverable from the surface, there can be no such thing as a prescription in favor of an adjacent proprietor to have an uninterrupted flow of such stream through the land of his neighbor.” On the other hand, where the subterranean water is not hidden, but has a defined flow, which is known or ascertainable, rights in it will be treated on the same basis as rights in a surface stream: Whetstone v. Bowser, 29 Pa. 59.
*159It is therefore clear, from the principles and the reasoning of all the cases, that the distinction between rights in surface and in subterranean waters is not founded on the fact of their location above or below ground, but on the fact of knowledge, actual or reasonably acquirable, of their existence, location, and course. The principle of Penna. Coal Co. v. Sanderson is precisely the same as that of Wheatley v. Baugh, and is of general application. It is, that the use which inflicts the damage must be natural, proper, and free from negligence, and the damage unavoidable. On the question of negligence, the question of knowledge is always important, and may be conclusive. Hence the practical inquiry is, first, whether the damage was necessary and unavoidable; secondly, if not, was it sufficiently obvious to have been foreseen, and also preventable by reasonable care and expenditure ? In Penna. Coal Co. v. Sanderson the damage was unavoidable. In Wheatley v. Baugh it was not ascertainable beforehand; hence the plaintiff had no cause of action in either ease. Later cases, following Wheatley v. Baugh, have held that injury to springs, wells, etc., supplied by mere percolation, was not actionable, and the reason has always been the same, that the damage could not be foreseen or avoided. If the boundaries of knowledge have been so enlarged as to make an end of the reason, then, cessante ratione, cessat ipsa lex. Geology is a progressive, and now, in many respects, a practical science; and, as truly remarked by the learned judge below, in his opinion on the motion for a new trial, “ since the decisions in Acton v. Blundell, and Wheatley v. Baugh, probably more deep wells have been drilled in Western Pennsylvania than had previously been dug in the entire earth in all time. And that which was then held to be necessarily unknown, and merely speculative, as to the flow of water underground, has been, by experience in such cases as this, reduced almost to a certainty.” If this is the state of knowledge at the present day; if the existence of a stratum of clear water, and its flow into wells and springs of the vicinity, and the existence of a separate and deeper stratum of salt water, which is likely to rise and mingle with the fresh, when penetrated in boring for oil or gas, are known, and the means of preventing the mixing are available at reasonable expense, then, clearly, it would be a violation of the living *160spirit of the law not to recognize the change, and apply the settled and immutable principles of right to the altered conditions of fact. The learned judge, in his charge, said: “ There is evidence from which the jury could fairly find that the defendant, when the well was drilled, knew, or ought to have known, if they had exercised any reasonable judgment, or investigated or paid attention to it, that the boring of this well in the way it was done, without shutting off the salt water from the fresh water, would almost inevitably ruin these and other wells in the immediate vicinity. And I think there is evidence from which the jury could fairly find that the defendant could, with the outlay of a small amount of money, have shut off the salt water from the fresh water so that it could not have done any injury.” If the jury had found the facts as this charge assumes that they fairly might on the evidence, then the plaintiff had made out a case of negligence, and was entitled to recover. Negligence in this sense is the absence of such care and regard for the rights of others as a prudent and just man would and should have in the same situation. If the plaintiff showed that the injury was plainly to be anticipated, and easily preventable with reasonable care and expense, he brought himself within the exception of all the cases from Wheatley v. Baugh to Penna. Coal Co. v. Sanderson, inclusive.
It may be well to say that, in cases of this nature, juries should be held with a firm hand to real cases of negligence within the exception, and not allowed to pare down the general rule by sympathetic verdicts in cases of loss or hardship from the proper exercise of clear rights. The danger of such result is not to be ignored, but we cannot on that account shut the door to suitors entitled to redress for genuine wrongs. The duty to maintain the line firmly where justice and law put it is,in the first instance and chiefly, upon the trial courts.
Judgment reversed, and venire de novo awarded.