delivered the opinion of the court:

The appellants, who were complainants below, obtained a preliminary injunction restraining the defendant corporation from enforcing the payment of an assessment which had been laid on certain real estate belonging to complainants, on Monroe street, in the city of Wilmington, for the construction of a public sewer. After a hearing before the Chancellor, on bill, answer, and depositions, the bill was dismissed, and thereupon an appeal taken to this court. The transactions which led to the application for an injunction are fully set forth in the bill, but the material charges on which the complainants rely for equitable relief are, that the city’s officers and agents acted without lawful authority, both in the construction of the sewer and in the manner and *129 mode of laying the assessment, and that the latter is, therefore, illegal and void. It is charged that the sewer was made for the purpose of diverting a small water course, which had previously flowed through a portion of the property now assessed, and not for the purpose of general drainage; that the diversion of the water course was the exercise of the right of eminent domain without authority, the city government not being invested with legal power to divert the stream; and that, even admitting the possession of the power, the assessment was illegal and void by reason of the neglect or failure of an officer of the city to perform an essential duty in relation thereto, the performance of which duty was necessary to the making of a legal and valid assessment. It appears, from the papers on file, that the water course was not only of no value to any of the complainants, or to the former owners of the assessed property, but by reason of its being an outlet for the refuse of factories and slaughter-houses located higher up the stream, was at times a positive nuisance, so that one or more of the complainants, with some sixty residents in the same neghborhood, signed a petition addressed to the City Council requesting that a culvert might be constructed to carry off by perfect drainage all the water coming from above, and thus prevent a continuance of what the petitioners represented to be a source of danger to the public health. The fact is not disputed that the petitioners contemplated the construction of the sewer in Monroe street as being the best and most effectual means of removing the difficulties and annoyances of which they complained. The sewer was made under and along Monroe street, from a point above to a point below the complainants’ land, at a cost of seven thousand two hundred and sixty-six dollars and thirty-five cents, being at the rate of nine dollars and ninety-eight cents per lineal foot, and, the water-course being turned into it, the nuisance was entirely abated. There was some attempt to show that the city was in fault in causing the nuisance by not keeping that part of the water-course which was below the complainants’ land open and unobstructed, and thus backing up the waters, but the evidence does not sustain this. The surface of some of the complainants’ land was depressed below the banks of the *130 stream and the grades of the surrounding streets, making a basin in which, during heavy rains, the flooded waters would collect and remain until carried off by absorption or evaporation. On the completion of the sewer a statement of its cost was presented to the city council, which body ordered that one-half of the said cost should be paid out of the city treasury, and directed that a portion of the remainder, amounting in all to one thousand and thirty-six dollars and ninety-two cents, should be charged against “ the estate of John Montgomery,” a former owner of the land, now belonging to the complainants, and of which he had died seized and intestate. The property had descended to the children and heirs of John Montgomery, and had continued in their possession as coparceners until a short time before the entry of the assessment upon the lien book of the city. The description in the lien book is a general one, being for 257.8 feet on the west side of Monroe street, between Second and Front streets, and for 157.8 feet on the southeast corner of Second and Monroe streets. The complainants, by claiming ownership of the assessed prop'erty, have established its identity and thus removed any objection to the generality and indefiniteness of its description.

The answer, admitting property in the complainants, and the diversion of the water-course, claims that the latter was done at the instance and with the knowledge and approval of the complainants ; that the sewer was made for general drainage, and that the assessment was regularly and legally imposed. The cost of the sewer was reported to the city council on May 29, 1873, and the matter of the assessment appears to have been considered by that body at several subsequent meetings until September 11, 1873, when it was finally approved and ordered to be entered on the lien boob. In the meantime, in the month of June, in the same year, the assessed property was sold at public sale, by an agent duly appointed for that purpose by the heirs of John Montgomery. The land was divided into building lots and sold to sundry purchasers, now the complainants. The agent retained out of the proceeds of the sale a sufficient sum to pay the assessment, in fulfillment of a condition previously announced, that the assessment would be paid, and the land sold “ clear.” Part *131 of the money so retained by the agent he afterwards paid over to the heirs, who protested against the validity of the city’s claim. One of the purchasers and a party to the bill deposed that the value of the property was increased three thousand dollars by the sewer.

An amendment to the charter of Wilmington, passed January 30, 1866, confers upon the city council the entire jurisdiction and control of the drainage of the city, with power to pass ordinances for the opening of gutters, drains and sewers, and for the regulating, maintaining, cleansing and keeping the same and the natural water-courses, runs and rivulets within the city limits open, clear and unobstructed, and for the entry upon private land for such purposes, and by general regulations to prescribe the mode in which the work shall be done, and who shall bear the expense thereof, and in its discretion to assess the costs thereof upon the persons and property, real and personal, of those particularly benefited thereby, or of those holding lands through or along which said sewers, drains and water-courses shall flow or pass, and prescribe the mode of collection thereof. The statute provides that private property shall not be taken for public use without j ust compensation, but is silent as to the mode in which such compensation shall be ascertained. A city ordinance passed June 21, 1866, by virtue of the authority thus given, sets out in detail the manner in which the costs of constructing sewers, etc., shall be assessed. It makes it the duty of the street commissioner to keep an accurate account of the costs of such construction and, through the street committee, to report the same to the council, together with a list of the persons and estates particularly benefited thereby, as well as of those holding lands through or along which said sewers shall pass, and an estimate of the value of the lands upon which said expense ought to be assessed, the said value to be estimated independently of buildings or improvements. The city council may, or may not, order any part of such expense to be paid out of the general fund, and the whole or remainder, as the case may be, shall be apportioned among those persons and estates particularly benefited, or among those holding lands along which the sewer shall pass. If the *132 owners be unknown, the assessment shall be generally against the lot or premises by particular or general description. The assessment, being approved by council, shall be entered on the lien book, and may be collected by warrant under the hand and seal of the mayor.

The bill denies the authority of the city to lay a special tax for the payment of the sewer, and assumes that the expense should be wholly defrayed out of the funds produced by general taxation. But the position most earnestly contended for by the complainants is, that the city having constructed a work partly for an unlawful object, namely, the diversion of a natural watercourse without license from the owners thereof, such unlicensed act of diversion being outside of its chartered powers, taints the entire work with illegality, and no portion of the expense can be lawfully assessed on the property-holders, notwithstanding that another and a lawful end may have been intended at the same time. The doctrine insisted on is, that where a tax or assessment is laid partly for a legal and partly for an illegal purpose, and such tax or assessment is entire and indivisible, the whole tax or assessment is illegal and void. The evidence, however, does not warrant the application of this principle to the present case. The city had the power, under the statute of 1866, to regulate and change the flow or direction of the natural drains and water-courses within its limits, to construct sewers and to assess the cost upon the owners of property especially benefited. Ho authority is given to invade or appropriate private property without compensation; this is expressly prohibited. It is true, the statute does not point out any way of fixing the compensation, but in this instance there is no necessity for ascertaining what might be due for taking for public use a property which was worthless and detrimental to its owners who asked for its removal as a boon, and have derived profit from its loss. These owners, and their privies in estate, stood by and saw the preparations made for depriving them of their property without remonstrance or objection. The building and completion of the sewer occupied several months, and its uses and objects were well known. Ho attempt was made to interfere with the work, nor *133 was the diversion of the water-course objected to. Some of the complainants requested the city council to carry off by perfect drainage the waters coming from above, and no word of disapproval was heard until the parties benefited were called upon to contribute to the payment of the expense. These facts admit of but one interpretation. The diversion having been made with the consent and approval, and to the evident advantage of the property-owners, the action of the defendant corporation was not illegal or ultra vires. The water-course had no existing or prospective value for the driving of machinery or for domestic uses, and by its continuance in its old channel rendered the lots through which it flowed unsalable. Its appropriation by the city was more of a public burden than a public benefit, while it afforded a special and advantageous relief to the lot-owners. Such an appropriation, under all circumstances, does not fall within the definition of the exercise of the right of eminent domain. We may, therefore, dismiss the further consideration of the want of power in the city, under the statute of 1866, to make the diversion complained of, and direct our attention to other points presented on behalf of the complainants.

That the expense of local improvements in a town or city may be met by local assessments, in whole or in part, appears to be so well established as to require no discussion. Stroud v. Philadelphia, 61 Pa. St., 255; 2 Dillon, Mun. Cor., 596 and notes. But when, under what conditions and to what extent, a court of equity should interfere to prevent the collection of such assessments, are questions which have not been uniformly decided. The inconvenience and confusion which might be caused by an indefinite delay in the receipt of municipal or other public revenues, and the serious embarrassments that might follow such delay, are obvious, and courts of equity, have, therefore, been disinclined to put any obstacle in the way of their prompt collection, except under special circumstances, such as left the complainant without any remedy at law, or where it was clear that the tax had been imposed without authority and was absolutely void. Even in the latter case, where the only question is one of excess of authority, depending on purely legal principles, it is doubt *134 ful whether equity should interpose. Those courts which most closely adhere to the distinctions between legal and equitable jurisdiction have generally refused to interfere by injunction with municipal assessments, except in cases which come under some one of the recognized heads of equity jurisdiction, and the doctrine is universally accepted that the collection of a tax will not be enjoined except upon the clearest grounds. The most important question, therefore, to be considered is that of jurisdiction ; for, although the arguments addressed to us by counsel were chiefly directed to other matters, this question was not waived, but it was expressly contended on the part of the city that the complainants, whatever might be their rights in a court of law, were not entitled to redress in a court of equity.

The complainants insist upon their right to an injunction for the reason that, the assessment being illegal and void, a threatened sale thereunder for its collection casts a cloud upon their titles, which they have no adequate legal remedy to remove; that such sale would cause them an irreparable injury; that some of the complainants having only an equitable title are absolutely without any remedy at law; and that, to refuse the writ would lead to circuity of action and a multiplicity of suits. •' These are recognized heads of equity jurisdiction, and we are to inquire whether thq complainants’ case falls under any one of them.

Is this assessment a cloud upon their titles? It is not every irregular or even void assessment that clouds a title. A lien or incumbrance, to throw a shadow upon title to real property so as to give the owner a right to relief in equity, must be one that is regular and valid on its face, but is in fact irregular and void from circumstances which have to be proved by extrinsic evidence. The test is well defined in Heywood v. The City of Buffalo, 14 N. Y., 539, to be where there is an apparent validity in the incumbrance and a total invalidity in fact which can only be proved by evidence aliunde. If the authority under which the assessment was made is unconstitutional, or if the power to tax is conceded, and the officers entrusted with the duty of fixing the tax rate have exceeded their authority, or if from any other cause, appearing on the face of the proceedings, the tax is *135 irregular and void, it will not affect the title, the defect being visible and undoubted. But a tax may be, from all that appears to the contrary, entirely regular and valid, the authority to levy it may be undisputed and every preliminary step necessary to be taken by way of notice to the owners of property and its valuation, the amount of revenue to be raised and the final apportionment may have been, on the face of the record, in strict compliance with the requirements of the law, and yet, by reason of fraud, corruption or neglect on the part of the officers making the assessment, the tax is void. The record may be false. Notice to owners and valuation of property may not, in fact, have been made, or the assessing officers may have conspired to make an unjust and partial assessment. An assessment or tax made and levied in the manner supposed, being apparently regular and legal, and in reality arbitrary and corrupt, but requiring extrinsic evidence to establish the fact, casts a cloud upon title. The contention here is, that the statute of 1866, which grants power to the city to regulate or change, within its limits, the course of natural rivulets, to construct sewers and assess the costs upon the parties specially benefited by the improvement, is unconstitutional, in so far as it undertakes to give the right of taking private property without providing any mode of ascertaining the amount of compensation to be paid to the owner; and that, waiving this objection and admitting the statute to be valid, certain conditions precedent, prescribed by the city ordinance, and which must be observed in order to make a legal assessment, have not been complied with. It is the duty of the street commissioner, under the ordinance, when he reports to the city council the cost of constructing a sewer, to present at the same time an estimate of the value of the lands upon which said expense ought to be assessed, the value of such lands to be estimated independently of any buildings or improvements thereon. It is charged that the commissioner failed to perform his duty in this respect, and that the records and proceedings of the city council do not show, nor does it appear from any other source, that the required estimate of value was made or presented. The only answer to this is the presumption that official duties have *136 been regularly fulfilled. Without entering into any inquiry as to the effect of this alleged omission of duty by the commissioner, it is sufficient to know that the omission appears on the face of the proceedings. Conceding, then, all that is claimed by the counsel for the complainants, the assessment is void by reason of its inherent defects. An unconstitutional law confers no authority, and if a city ordinance imposes certain conditions which must be complied with in order to make a legal tax, the failure to comply with any one of the conditions renders' the tax void; so that, on the one hand, the city council having acted without authority, and on the other, in violation of its own self-imposed restrictions, the assessment is not binding, creates no lawful lien and does not cloud the titles of the complainants. But all these matters are wholly within the jurisdiction of a court of law, to be determined by an examination of the statute, an inspection of the journals and records of the city government connected with this particular assessment, and do not call for any outside evidence for the purpose of ascertaining the validity of the tax. Authority in support of this view of what makes a clouded title may be found in the opinion of Chancellor Walworth, in Wiggin v. The Mayor, etc., of New York, 9 Paige, 23 ; a case involving the validity of an assessment for the opening of a street. “ If the whole proceedings,” says the chancellor, “ in relation to the opening were absolutely void in law, and that fact appears upon the face of the ordinance itself, a sale for the assessment upon the claimants’ lots would not even create a cloud upon his title. For as every person must be presumed to know the law, a proceeding which is upon its face not only illegal, but absolutely void, does not constitute a cloud upon the title to real estate against which a court of equity will relieve.” In Van Doren v. The Mayor, etc., of New York, 9 Paige, 389, the same eminent judge, reaffirming the principle of the previous case, adds: “A valid legal objection appearing upon the face of the proceedings, through which the adverse party can alone claim any right to the complainants’ land is not in law such a cloud upon the complainants’ title as can authorize a court of equity to set aside or stay such proceedings. But where the claim of the *137 adverse party to the land is valid upon the face of the instrument, or the proceedings sought to be set aside, as where the defendant has procured and put upon record a deed obtained from the complainant by fraud, or upon a usurious consideration, which requires the establishment of extrinsic facts to show the' supposed conveyance to be inoperative and void, a court of equity may interfere and set it aside as a cloud upon the real title to the land.” The chancellor cites Simpson v. Lord Howden, 3 My. and Craig, 97, in which it was decided that there is no jurisdiction in equity to order a legal instrument to be delivered up, on the ground of an illegality which appears upon the face of the instrument itself. In Pixly v. Huggins, 15 Cal.,127, it was held, that if the sale which it was sought to restrain is such that, in an action of ejectment brought by the purchaser under the sale, the real owner would be obliged to offer evidence to defeat a recovery, then such a cloud would be raised as to warrant the interference of equity to prevent the sale. High on Injunction, § 272, recognizes the same rule as settled by the general current of authorities which draw a distinction between cases where the invalidity or illegality charged as the cloud is shown by evidence dehors the record, and where it appears upon the face of the proceedings. And while in the former case the relief is freely granted, in the latter, courts of equity will not interfere. To the same effect is Heywood v. The City of Buffalo, already cited, approved by Ewing v. St. Louis, 5 Wall., 413, and by Dows v. Chicago, 11 Wall., 108. In Ewing v. St. Louis, the courts say that with the proceedings and determinations of inferior boards or tribunals of special jurisdiction courts of equity will not interfere, unless it should become necessary to prevent a multiplicity of suits or irreparable injury, or unless the proceeding sought to be annulled or corrected is valid upon its face? and the alleged invalidity consists in matters to be established by extrinsic evidence. The most recent case on this point that has come under our notice is Wells v. The City of Buffalo, 21 Albany Late Journal, 234, which was an application to set aside an assessment as a cloud upon the title to the plaintiff’s land on the ground that the statute authorizing the assessment was un *138 constitutional, and the court held that no cloud could be created by an assessment which was void upon its face, and dismissed the complaint.

The owner of personal or real property, seized or sold under execution for the collection of an illegal municipal tax, has an adequate remedy at law, either by paying under protest the amount demanded, and bringing an action against the city to recover it back, or by an action of trespass for the recovery of damages. In the case of a sale of real property under a void assessment, as in the case of a sale by the sheriff on a void judgment, the purchaser buys at his peril, and the owner may fold his arms in defiance, or, if dispossessed, maintain his rights by an action of ejectment. Under such circumstances the owner can sustain no irreparable injury, and would suffer a loss only by his own passive submission to a wrong. A party claiming title under a corporation tax sale must show that every prerequisite to the power of sale has been complied with, and compliance with law must appear on the face of the proceedings. 2 Dill, on Mun. Cor. 658; The Collector v. Day, 11 Wall, 113.

A writ of certiorari will afford the owner of property, subject to an illegal assessment, another mode of redress or relief. This remedy is expressly referred to as an appropriate one by Mr. Justice Field in delivering the opinion of the court in Ewing v. St. Louis, and is approved by Judge Dillon in his excellent work on Municipal Corporations. That learned author remarks: “ The unquestionable weight of authority in this country is, if an appeal be not given, or some specific mode of review provided, that the superior common law courts will, on certiorari, examine the proceedings of municipal corporations, even although there be no statute giving this remedy; and if it be found that they have exceeded their chartered powers, or have not pursued those powers, or have not conformed to the requirements of the charter or law under which they have undertaken to act, such proceedings will be reversed or annulled. An aggrieved party is, in such case, entitled to a certiorari ex debito justitia.” 2 Dill, on Mun. Cor., 740.

Equity will interpose, in a proper case, to prevent a multipli *139 city of suits, excessive litigation, or circuity of action. A court of equity, on a bill being filed for a discovery, will sometimes proceed to take jurisdiction of all the matters in controversy between the parties, instead of sending them to a court of law, and thus avoid circuity of action. And so, to prevent a multiplicity of suits, as of one against many, or of many against one, in relation to the same cause of action, the aid of equity may be invoked, But multiplicity does not mean multitude, and equity will not interfere where the object is to obtain a consolidation of actions, or to save the expense of separate actions. Sheldon et. al v. The Centre School District, 25 Conn., 224; Dodd v. The City of Hartford, 24 Conn., 232; Lord Tenham v. Herbert, 2 Atkyns, 483; Eldridge v. Hill, 2 Johns. Chan., 283. Or where the claim of right rests on a mere question of law, as for ascertaining the legality of the proceedings of a municipal corporation. West v. The Mayor of Albany, 10 Paige, 539. Chancellor Kent, in Eldridge v. Hill, supra, says: “ Enjoining litigation at law seems to have been allowed in only one of these two cases, either where the plaintiff has already established his right at law, or where the persons who controvert it are so numerous as to render an issue under the direction of this court indispensable to embrace all the parties concerned, and to save multiplicity of suits.” A distinction is also to be observed between bills for the prevention of multiplicity of suits or bills of peace, whose object is the suppression of useless and vexatious litigation, and cases where the real object of the relief sought is the consolidation of a number of suits of like nature, since in the former class of cases courts of equity may properly enjoin, but in the latter they will refuse to interfere. Thus, where an injunction was asked to stay proceedings in ninety-two actions of ejectment, until one or more might be tried, the parties, pleadings, title and testimony being the same in all the cases, the relief was refused, the real object sought being a consolidation of the actions which a court of law might properly grant. High on Inj., 329; Peters v. Prevost, 1 Pain C. C., 64. In Penna. Coal Co. v. Del. and H. Canal Co., 31 N. Y., it was said, that where a right can- only be adequately protected or enforced by ruinous Or expensive law-suits, courts of equity have *140 interposed their jurisdiction, and have given the party redress by injunction, specific performance or other adequate relief, in order thereby to prevent litigation and the mischief which results from it. Bills of peace, says another authority, have been sustained by the court to settle the rights of parties in a single suit, in cases where the questions to be determined were questions of fact, or mixed questions of law and fact. But no such bill can be sustained to restrain a defendant from suing at law where the rights of the parties depend upon a question of law merely, and where the defendant in a suit at law must eventually succeed in his defense, without the aid of a Court of Chancery, if the law is in his favor. West et al. v. The Mayor of Albany, supra. The real object sought to be reached by the complainants being a consolidation of their actions, or remedies, against the defendant corporation, they have not presented such a case on the facts and the law as would warrant a court of equity in taking cognizance of their controversy to the exclusion of a common law court which has all the necessary jurisdiction and power to grant them full and adequate redress. It would be an evasion of principle to allow a dozen or twenty property owners to tie up the hands of a tax collector, while the individual owner was compelled to seek his remedy in a court of law. A combination of taxables could at any time arrest the operations of a municipal government by enjoining the collection of taxes and thus subordinate public to private interests.

The charge that some of the complainants, being only equitable owners of a portion of the real estate subject to the lien of the assessment, are absolutely remediless at law, would furnish a strong reason for interference if they were not represented by a trustee duly appointed, who has accepted the trust, is acting in that capacity, and has signed the bill of complaint. Holding the legal title to the land, he is in all respects competent to protect the rights and interests of his eestuis que trust in a court of law.

The application for an injunction being unsupported by the facts and the settled principles and practice of equity, as we understand them, we think the bill was properly dismissed by the *141 Chancellor. In coming to this conclusion we have purposely abstained from expressing any opinion on the sufficiency of the main objections to the assessment. The appropriate tribunal for their settlement is the Superior Court, by which they can be heard and determined without interrupting for a single hour the collection of the public taxes, and without impairing the rights or injuring the property of the complainants.