UPON REHEARING.
Mr. Justice Campbelldelivered the opinion of the court.
A rehearing upon both branches of this case has been allowed. Additional counsel have favored us with elaborate *332written and oral arguments. While the former arguments upon the main propositions have been cast in new settings, and in some respects urged with greater vehemence and more superlatives,—-with the exception of an attempt by appellant to change position in some particulars,—■ neither side has presented any questions that were not thoroughly argued and considered at the original hearing.
One of appellant’s new counsel opens his brief with the following statement: “It is the belief of many members of the profession that an application for rehearing cannot succeed unless the error of the court is suggested in terms of such modest contention as to amount almost to an apology and with plausible avenues of retreat, should the error be made apparent. With that belief we do not agree, llorare we disposed to adopt the method of argument which it requires.”
Our experience, based upon an examination of many such applications, would not lead us to suspect that such belief was widespread, or had effected permanent lodgment in the minds of many of the profession. Certainly, in the case at bar, while counsel has observed that respect for the court which is fitting, he has, in his argument, left no room for doubt as to his own notion of the method of argument to pursue, and if that argument is given the weight which it is assumed to possess, there is left for the court no avenue of graceful retreat.
First, as to the ditch and canal priorities: Complaint is made because, in the opinion, we treated this action as in the nature of a collateral attack upon the ditch decrees. Counsel now say its object was to correct the decree in question on the ground of a mistake of the court in computing the quantity of water appropriated by the owner of the Larimer and Weld canal.
That we were justified in our characterization is apparent from the complaint itself; but, if we were mistaken in this respect, counsel for appellant fell into the same error,.for in his original brief he says that “ the complaint was a bill in *333equity, in the nature of a bill of peace * * * and, particularly, to obtain judicial determination of the respective rights of the corporation litigants to divert water from the Cache la Poudre river, both for direct irrigation, and for storage in reservoirs.”
Since the proceedings in question were instituted and prosecuted to obtain, and the decrees thereunder resulted in, a judicial determination of the same rights which the plaintiff seeks here to readjudieate, we said then, and now say, that this is a collateral attack. The appellant, after once stating what the object of his action was, should not complain if we adopt his own definition. But if a party should be permitted thus to shift his position, and if we were to assume with him that the complaint pleads a mistake as the equitable cause of action, we proceed to an examination of the record upon that hypothesis.
Among the findings of the district court were the physical dimensions of the canal and the quantity of water appropriated. Counsel say that by the latest and most approved test a canal of such ascertained dimensions is incapable of carrying such computed capacity.
In Ditch Co. v. Ditch Co., 22 Colo. 115, it was ruled that in a decree, like that under consideration, one of the things to be embodied therein is the quantity of water; hence, when once ascertained, it is res judicata. Counsel now seize upon this declaration and say that the physical dimensions of the ditch are likewise to be determined; and taking these dimensions as one verity, we have, it is said, in the same decree two verities absolutely inconsistent with each other. Both cannot be true; one must be false; which shall be upheld, which rejected? Having propounded this query to us, counsel proceed to answer it for themselves by rejecting the computed quantity as of less dignity, because, they say, it is the result merely of a mathematical calculation based upon an absolute and fixed verity, viz : physical dimensions.
We observe, first, that the statute requires the court in its decree to set forth the quantity of water appropriated, *334describing snob amount in cubic feet per second of time, if the evidence shall show sufficient data to ascertain the same. If, however, such data are not in the evidence, then, in lieu of the quantity, the decree must set forth the width, depth and grade of the ditch, and such other description as will most certainly and conveniently show said amount. If sufficient data are at hand, as they were in this case, physical dimensions áre not required. In this there is the implication that physical dimensions alone are not sufficient data from which to ascertain the quantity; other description, other data enter into the problem. This decree contains botli the quantity in cubic feet and physical dimensions; and it might be argued that the contingency under which the court might ascertain dimensions not having happened, the ascertainment of the latter was unauthorized, and that only the quantity ascertained was a judicial verity. At least, it would seem, counsel have not correctly stated the proposition, and the premises laid down in the foregoing argument are not strictly correct, and their reasoning not conclusive. But interesting as may be the question which, if either, of these two alleged verities is of the higher rank, the requirements of this case do not call for its resolution. Involved in appellant’s argument is the assumption that, if we use this new test, the calculation as made by the district court is erroneous. In the formula commonly designated as Kutter’s the value of “ w,” the coefficient of roughness, which is one of the most important factors, varies under different conditions. Where the ditch is smooth, with no obstructions in it, with but few and well rounded curves, with banks and bottom hard and well packed, it has one value; where its surface is rough, covered with grass, weeds' or other obstacles that naturally accumulate in the use of the ditch, with numerous and sharp curves, this value is different. The alleged proof of the erroneous calculation is found in the testimony of Prof. Carpenter that from two measurements or experiments made by him, he so determined. But, as stated in the original opinion, we think it clear from his testimony and that of other wit*335nesses as to this point, and from what the authorities say of the value and accuracy of this formula that thereunder substantially the same result might be reached as that arrived at by the trial court under another formula. At any rate, it is not made clearly to appear by this record that a different result would necessarily follow if this new formula should be used.
However this may be, it is altogether sufficient for the purposes of this case to say that, when this decree was entered, the computation of the court was made under a test, or formula, then in general use in this state and, as the evidence tends to show, recognized as the most accurate then employed; and that said computation upon that basis is correct.
This is by no means a case where the decree on its face shows that a formal or clerical error as to calculation was committed. The claim is not that the court erred in making the computation from the formula which it used, but, on the contrary, the mistake complained of consists in the use of a wrong formula, and in not selecting the-one which, as is said, has since been discovered and found to be more accurate. It seems clear, however, where the issues are framed with that object in view, that such a mistake cannot be corrected. If so, it would permit a court, not upon a review in appellate proceedings, but in a direct proceeding, to overturn a decree because, upon further consideration, and in the light of new evidence, the court thought a different conclusion should have been reached. If we should now correct the decree of 1882 for the reason urged, then at the end of the next decade there may be evolved a new method of determining the carrying capacity of ditches giving even more accurate results than under the Kutter formula, and in an action then brought to correct the mistake made by us now in applying the Kutter test, the court must set aside our decree and enter a new one, and so there would be no end to the litigation, provided new and more accurate tests are discovered. Union M. & M. Co. v. Dang-*336berg, 81 Fed. Rep. 73, 116, is an instructive case upon this point, and is squarely against appellant.
We conclude the discussion of tins branch of the case by remarking that counsel’s entire attack upon this decree is an attempt, only partly disguised, under the pretense of correcting a mistake therein, at this late day to reopen and readjudicate the relative rights of ditch owners whose predecessors in interest were parties to the proceedings in which the decree determining these rights was rendered; and therein consists the fundamental error in much of their argument. This attempt is the more clearly apparent when we find that, with much apparent earnestness, they aver that it is of common knowledge that these early decrees,—entered when lawyer and layman were in doubt as to the meaning .of the recently enacted law, and when knowledge of irrigation was limited,—awarded to the ditches a greater quantity of water than they were entitled to, or could carry. That since that time many of the statutory obscurities have been elucidated by legislative amendment and judicial decision, and the science of irrigation has greatly developed. That among the discoveries made is the fact that the carrying capacity of ditches can now be more accurately determined than formerly. In view of these considerations, counsel ask us arbitrarily, as we think, to correct these early mistakes; —their client and its grantors not having availed themselves of the relief which could be awarded under the statute had a review been seasonably asked, or an appeal taken.
As an illustration that courts avail themselves of the latest developments of science, we are admonished that the science of operating a railroad is of constant growth and expansion, and that in actions sounding in damages for personal injuries, involving the correlative duties of master and servant, the court constantly takes notice of these advances, and so modifies and expands old rules to conform to new processes and to meet new conditions. So we are asked in the decision of this controversy, in determining whether the district court erred in computing the capacity of the Lari-. *337mer and Weld canal, to apply to that question a test or formula that is said to have come'into general use since the district court had occasion to determine what was a proper test.
The illustration from railroading was unfortunate for the appellant, for, as is well said by counsel for appellee, while courts do avail themselves of new processes and new discoveries in all branches of science and apply them to new cases as they arise, they do not, in a direct proceeding, open up solemn judgments, rendered upon competent and proper testimony, for the purpose of setting aside a calculation or a deduction therein made by the trial court, based upon ligitimate testimony, and substitute therefor a different conclusion merely because subsequent discoveries in some science or art would seem to require it. In a new case upon the same facts, or in the former case had such later facts then been in evidence, the question is entirely different. So, here,, this ditch decree cannot be reopened to correct an alleged mistake made in the calculation of the quantity of water appropriated, based upon a formula which the evidence then established to be the most correct in general use, because, as the result of later investigations, another test has been discovered, said to give more accurate results. And if this Kutter formula was then known and not used by the court, we must presume that it was the finding and judgment of the court that the one that was used was more accurate. In either case the decree cannot be disturbed.
In passing upon the reservoir rights,, the appellant complains that this court in its opinion, as well as the district court in its findings, entirely ignored the decree of the district court of Larimer county of March, 1885, in which, it is claimed, there was decreed to the appellant’s various reservoirs certain priorities of the same date as that awarded to its canal. In this great injustice is said to have been done.
It is true that the opinion states that the reservoirs in question were unaffected by any decrees of the court, as the reservoirs were built after the decrees were rendered. *338Though the decree of 1885 was ignored as a material question in the case, it was by no means overlooked. That decree, in one clause, purports to award certain priorities to the reservoirs of appellant, which, taking that one portion by itself, apparently makes them superior to that of the defendant reservoir company. That we had abundant reason for our statement will now be shown from the record, even though the effect be to prolong the opinion.
In his original brief filed in this court the counsel of appellant, who also tried this case in the district court, in summarizing his argument on the reservoir priorities concludes with this statement:
“ In the foregoing’ deductions from the evidence, we have said nothing concerning the decree of 1885, adjudicating that the Larimer county ditch (appellant’s grantor) had a right to use its priority, dating from 1881, to fill Long Pond; nor have we referred to the fact that water had been stored, to some extent, in Long Pond during the ’80s, by appellant’s grantor. We do not need to rely on any claims based on the decree of 1885, or any exercise of rights under that decree by the old company. We do call attention to the point, however, that if a non-use of any excess over 560 cubic feet per second, by the Larimer and Weld Irrigation Company, for irrigating purposes, from April 11,1884, to June 20,1893,— a period of nine years,—did not constitute an abandonment of any pretended rights, based on a computation in the decree of 1884, then a failure to beneficially use water stored in Long Pond, between October 30, 1885, and May,-1892,—a period of only six and a half years,—did not constitute an abandonment of any rights.”
The zeal of counsel to claim under this decree, and thus shift the former position, is born since our original opinion was handed down; for as we therein held in favor of the defendant reservoir company, under the evidence upon the issue of diligence in construction, they now seek to escape the effect of that holding by claiming under a prior decree.
But if the appellant’s own concession in argument, as *339above quoted, does not work an estoppel to allege the contrary, the record itself otherwise furnishes most ample authority for disregarding the decree. Its complaint, by which, of course, appellant is bound, does not predicate any rights upon this decree, but only upon the fact that appropriations of water for its reservoirs were perfected prior to the inception of defendant’s rights. Turning to the evidence, we find that no pretense is made that the reservoirs were completed, or appropriations of water therefor perfected, prior to 1892. A sworn statement was filed October 10,1892, by the appellant company under section 2265, Mills’ Ann. Stats. (Gen. Stats, sec. 1720) wherein is not only no claim of priority for any of the reservoirs under any decree, or any reference thereto, but the priority of all is claimed, by way of relation only to the date when the work of construction was begun in the month of September, 1891.
Referring again to the proceedings terminating in the decree of 1885, there is no finding of fact by the court, or recital in its decree, that these reservoirs 'at the time were completed, or that water had ever been stored therein. Upon the contrary, it is clear from the entire record in the case that neither in the decree of 1885, nor in the preliminary or conditional decree entered in 1882, was there ever any intention to award any priority to the reservoirs of appellant, unless completed within a reasonable time. These decrees must be taken together, and every part thereof must be considered. By section 6 of the decree of 1882 (which decree, by express recital to that effect in the decree of 1885, is made part of the latter), pleaded by appellant itself, it is expressly declared that its provisions should not apply to any ditches, canals, or reservoirs completed after the closing of the testimony in that proceeding; and it was further provided that the decree should apply only to such as were finished before the decree itself was entered. So we conclude that the decree of 1885, taken in connection with that of 1882. as should be done, rightly interpreted, did not award, and did not purport to award, to these reserviors any priority prior *340to their appropriation of water and their completion within a reasonable time, and then by relation to date as of the beginning of the work of construction. If, however, it did, other facts in this record show that the reservoirs themselves were never completed until some time in the year 1893; that practically they were not used for storage purposes until that time. These facts, coupled with the sworn statement filed in October, 1892, by their owner that work was begun on them in September, 1891, and the priority claimed only from that date,-—-constitute, as pleaded by the defendants, virtually an abandonment by appellant of any alleged priority secured by the decree by expressly making the inception of its right date when work began, long after the decree was entered.
The record also shows beyond any serious controversy that the chief, if not the only, issue at the time of the trial as to these reservoirs was as to the diligence employed by the defendant reservoir company in completing its work. Counsel on both sides thus tried the case, and the evidence was directed almost exclusively to that issue; and the parties should be held to the case as thus made.
Appellant, however, for the purposes of the argument, conceding our statement to be true, further contends that, under the evidence produced at the trial upon this issue, the findings of the court below were wrong, and should be set aside. Courts do not lay down a general rule by which, in every case, due diligence may be determined; but it is a question of fact depending largely upon the facts and circumstances of the particular case. To attempt to give a general definition would be unwise, and we do not deem it necessary to this case, or helpful as a precedent, to give in detail the facts in this record. We content ourselves by saying that, after a very careful rereading of the evidence, we are satisfied that the defendant reservoir company observed due diligence in completing its work, and that the findings of the trial court to that effect are sustained by the evidence.
What to us, however, is the most plausible argument made *341in support of the appellant’s contention that its reservoir priorities are superior is this: Since the appellant finished its reservoirs before the defendant reservoir company completed its work, although said latter company first began the work of construction, the priority of the defendant may not, by relation,' take effect as of said beginning, because the defendant failed to file its map and statement, as provided by section 2265 Mills’ Ann. Stats., until after the appellant had made its filing, entirely finished its work and perfected its appropriation. The statute is as follows:
“ Every person, association or corporation hereafter constructing or enlarging any ditch, canal or feeder for any ditch or reservoir for irrigation and taking water directly from any natural stream, and of a carrying capacity of more than one cubic foot of water per second of time, as so constructed or enlarged, shall, within ninety days after the commencement of such construction or enlargement, file in the office of the county clerk and recorder of the county in which the head-gate of such ditch or feeder may be situated, and also in the office of the state hydraulic engineer, a map, etc., showing certain things. * * * If such statement he filed within the time above limited, priority of right of way, and water accordingly, shall date from the day named as the day of commencing work, otherwise, only from the date of the filing of the same.”
The appellee contends, inter alia, that this statute is inapplicable to the case in hand; yet, if so, that for various reasons it is unconstitutional.
We appreciate the difficulty and importance of the questions raised as to the constitutionality, the meaning and effect of this act; and in a proper case would not hesitate to determine them. But hr the view we take of this case, the constitutional question is not properly before us. A careful reading of the act shows that the intention of the general assembly was to make its provisions apply only to ditches, canals or feeders for reservoirs of the designated capacity, taking water directly from a natural stream. Ditches, etc., *342taking water from a natural stream indirectly through some previously constructed conduit, or ditches of other capacities, or those taking water from an artificial stream, fall without its provisions.
Now the feeder for the reservoir begun by the defendant reservoir company in 1890 was not intended to, and does not, take water directly from the Cache la Poudre river, or any natural stream, but its head-gate is in the previously constructed Larimer and Weld canal at a point therein situate in W eld county. The head-gate of the canal itself is in Larimer county. These facts are conceded by the appellant when, in answer to a contention that the defendant’s filing of the map in Weld county was a compliance with the act for the reason that the head-gate of its feeder in the canal was in Weld county, its counsel replied thereto by saying that the canal is an artificial, and not a natural, stream. Indeed, it may well be said that, if this act is applicable, the defendant complied therewith, for it filed its map and statement in that county in which the head-gate of its feeder was situate. But we say that the defendant’s feeder did not take water directly from a natural stream; and the act being penal, in character, its scope should not be extended to include feeders or ditches that are not, by reasonable construction, within its provisions.
If, however, it be said that defendant, by attempting to file its map thereunder, recognized the applicability of the act to its enterprise, it can scarcely be seriously argued in one breath that the priority of the defendant is lost by reason of the failure to comply with a certain act, and in the next breath to say that an unsuccessful attempt to comply with its provisions estops the party to deny its applicability. But even if defendant company had made full compliance with this act by filing its map, and even though counsel on both sides concurred in holding it applicable to the defendant’s ditch, this would not bind the court to follow their opinion on a question of statutory construction.
But it is said further that the defendant reservoir com*343pany has made no appropriation of water for reservoir purposes from the natural stream, and intended to take none, but, on the contrary, appropriated, and intended to appropriate, only the excess of water in the Larimer and Weld canal when not required by its owners for direct irrigation. This is said to appear both from the pleadings and the evidence. The defendant’s answer avers directly to the contrary, and distinctly alleges a claim of, and an intention to claim, an appropriation both of such excess and an original appropriation of water from the stream itself, and the evidence clearly warrants the findings of the trial court to that effect.
The fact that the head-gate of the feeder of the reservoir tapped the Larimer and Weld canal, and not the stream itself, is by no means conclusive evidence, even if, in fact, it is any evidence, of an intention not to make an appropriation of the water of the natural stream. The canal is tiot owned by the defendant reservoir company, yet if the latter is able to make an arrangement with the owner thereof, Avhereby it may put in the canal a head-gate and use the canal itself as a conduit for carrying water directly from the stream to said head-gate, and thence, by its own feeder, carry the water of the stream to its reservoir for storage purposes, that is a matter of contract between the two. Such a right might be acquired by condemnation in a proper case (Mills’ Ann. Stats, sec. 2263; Gen. Stats, sec. 1718), and, of course, by contract. We perceive no reason why a distinct and valid appropriation of water from the natural stream, either for direct irrigation or for storage in a reservoir, may not thus be made. Indeed, section 2265 itself, if valid, when it makes applicable its provisions only to ditches, etc., of a certain carrying capacity, and to those taking water directly from a natural stream, tacitly, and by implication, recognizes that a valid and original appropriation of water from a natural stream itself may be made by and through ditches of other carrying capacities, and by those taking water indirectly therefrom. The feeder constructed by the defendant not *344being of the class specified in the act, is unaffected by its provisions. It was not necessary, therefore, for defendant to file a map and statement.
Many other propositions have been discussed, but we do not consider them material to this decision. The foregoing sufficiently disposes of the questions necessary to he determined. The former opinion is adhered to.