Opinion,
Mr. Justice Clark:It appears from the case stated that the Ridge Avenue Passenger-Railway Company resulted from the merger and consolidation, under the statute, of the Girard College and the Ridge Avenue & Manayunk Passenger-Railway companies; the former incorporated under the act of April 15,1858, P. L. 300, and the latter under the act of March 28,1859, P. L. 264: By the terms of their respective charters, the original companies were required, annually, to “ pay into the treasury of the city of Philadelphia, for the use of the said city, whenever the dividends shall exceed six per centum per annum on the capital stock, the sum of six per centum on the said dividends thus declared.” After the consolidation, however, an act of assembly was approved, March 8, 1872, P. L. 264, entitled “An Act relating to the Ridge Avenue Passenger-Railway Company,” which provided that the said company should pay annually into the treasury of the city of Philadelphia, for the use of the said city, “ a tax of six per centum upon so much of any dividend declared, which may exceed six per centum upon their said capital stock,” etc. It is now contended on the part of the city that this act of 1872 was in conflict with § 8, article XI., amendment of 1864, of the constitution of this state, in force at the time of its passage, and that the company, therefore, remains liable for the greater tax imposed in the original charters. The company having paid, and the city having received the taxes, .according to the provisions of the act of 1872, for the years 1880 and 1888, inclusive, this suit is brought to recover the *491balance which would remain unpaid for these years, according to the rate fixed in the original charters.
The provision of the constitution was as follows: “ No bill shall be passed by the legislature containing more than one subject, which shall be clearly expressed in the title, except appropriation bills.” Article III., § 3, of the present constitution, is precisely to the same effect; it differs from the amendment of 1864 in phraseology only.
Although it is not necessary that the title to an act of assembly should be a complete index to its provisions, all the cases agree that the subject of the proposed legislation must be so -expressed therein as to give notice of its purpose to the members of the legislature, and to others specially interested: Commonwealth v. Green, 58 Pa. 233; Dorsey’s App., 72 Pa. 192; Beckert v. Allegheny, 85 Pa. 191; Phœnixville Road, 109 Pa. 44; Sewickley Bor. v. Sholes, 118 Pa. 165. A distinction exists, however, between the title to an original act and that of a supplement. When an act of assembly is a supplement to a former act, if the subject of the original act is sufficiently expressed in its title, and the provisions of the supplement are germane to the subject of the original, the general rule is that the subject of the supplement is covered by a title which contains a specific reference to the original by its title, giving the date of its approval, and declaring it to be a supplement thereto : State Line R. Co.’s App., 77 Pa. 429; Craig v. First Presb. Church, 88 Pa. 42; Pottstown Bor., 117 Pa. 538; Millvale Bor. v. Railway Co., 131 Pa. 19. Although the cases at the outset, after the adoption of this amendment, were a little loose in its construction, yet, if the distinction just referred to is kept in view, they will be found to have established a reasonably consistent rule, which may now be recognized as the settled law of the state.
The question of the constitutionality of the act of March 8, 1872, upon the ground of its defective title, was on a previous occasion argued in this court before a full bench ; and in a per Curiam opinion it was held that the subject of the bill, as it was passed by the general assembly, was not clearly expressed in the title: Ridge Ave. Ry. Co. v. Philadelphia, 124 Pa. 219; and upon that ground the act was held to be in conflict with the constitutional provision referred to. In the case cited, the com*492pany sought to have the advantage of a provision of the act of 1872, relieving it from the burden of repairing the streets, a burden imposed by the original charters, and releasing the company from control by the city councils; whilst in this case the company seeks to have advantage of a provision of the same act, which would in part relieve it from the payment of city taxes. If the title of the bill was not so expressed as to warn the city as to the former feature or effect of the bill, it was clearly defective as to the latter, for there is no reference in the title to either; indeed, there was nothing expressed in the title to call the attention of the city, that her rights were in any way affected by it. We are not inclined to change the conclusions to which we came in the case referred to, nor to recede from the rule so' well settled in our cases. It follows that the act of 1872 must be treated as unconstitutional, and therefore void, in so far, at least, as it affects the rights of the city and changes the rate of taxation for city purposes.
But, assuming that upon this ground the act of 1872 is unconstitutional and void, in so far as it affects the rights of the city of Philadelphia, and that the company was and is liable according to the provisions of the original charters of 1858- and 1859, is the city now in condition to insist upon that measure of liability for the years 1880 to 1888, inclusive ? It appears that, some time after the year 1879, the city brought suit against the company for the taxes of 1872 to 1879, inclusive. The claim was for taxes according to the provisions of the act of 1872. The company, admitting its liability under that act, contended that, upon a proper construction of the act, it was not liable for tax, excepting when any single or separate dividend declared exceeded six per cent of the authorized capital of the company. The city’s contention was, however, that as, upon this construction of the statute, the company could declare dividends as often as the directors desired, they might so manipulate their dividends as to defeat the manifest design of the legislature to provide revenue for the city. Suit having been brought, as we have said, defence was taken and such proceedings were afterwards had that the cause came into this court upon a writ of error, where it was held that the extent of the company’s liability under that act was to be ascertained by applying the aggregate annual dividends to the capital actual*493ly paid in, and judgment was entered against the company accordingly. The constitutionality of the act of 1872 was not drawn in question, and the company was compelled to pay according to the demands of the city under the provisions of that act: Philadelphia v. Railway Co., 102 Pa. 190.
The argument of the company’s counsel now is that, although, in the case referred to, the point does not appear to have been made or decided, yet the constitutionality of the act of 1872 must be taken to have passed in rem judicatam; that the judgment in that case necessarily involved a decision that the statute imposing the tax was to that extent valid, and, although the cause of action is not the same, the city is estopped of record from re-litigating that question. In support of this doctrine they cite Beloit v. Morgan, 7 Wall. 619; Aurora City v. West, 7 Wall. 85; Durant v. Essex Co., 7 Wall. 107; Corcoran v. Canal Co., 94 U. S. 741; Wilson v. Deen, 121 U. S. 525; and Duchess of Kingston’s Case, 2 Smith Lead. Cas., 8th ed., 941.
Whilst the general rule declared in these authorities is undoubtedly correct, it does not extend to estop a person from setting up the unconstitutionality of a statute, when the cause of action is not the same. The former judgment is absolutely conclusive upon the parties, as to the cause of action involved in it, although the statute upon which the proceedings wore taken was not constitutional; that judgment can only be impeached collaterally for fraud or want of jurisdiction. It is a matter of no consequence now that the act of 1872, upon which judgment was entered for the amount of the tax, was unconstitutional and void ; judgment having been entered, and no appeal taken, the subject matter of the issue in that suit is res judicata. The former judgment, therefore, operates as a bar to any subsequent action founded on the same demands: Bigelow on Estop., 80-88. In the case at bar, however, whilst the point in issue may perhaps be the same, the cause of action is different; and, although the verdict, with the judgment thereon, would furnish conclusive evidence of the matters in controversy upon which the verdict was rendered, and operate as a bar to the further litigation thereof, it would not preclude the plaintiff in this suit from asserting the unconstitutionality of the act upon which the previous action proceeded: Bigelow on Estop., 90-108.
*494The distinction is thus stated by Mr. Justice Field in Cromwell v. Sac County, 94 U. S. 352, 353:
“ It should be borne in mind that there is a difference between the effect of a judgment, as a bar or estoppel against the prosecution of a second action upon the same claim or demand, and its effect as an estoppel in another action between the same parties, upon a different claim of cause of action. In the former case, the judgment, if rendered upon the merits, constitutes an absolute bar to a subsequent action. It is a finality as to the claim or demand in controversy, concluding parties and those in privity with them, not only as to every matter which was offered and received to sustain or defeat the claim or demand, but as to any other admissible matter which might have been offered for that purpose.....But when the second action, between the same parties, is upon a different claim or demand, the judgment in the prior action operates as an estoppel only as to those matters in issue or points controverted, upon the determination of which the finding or verdict was rendered. In all cases, therefore, where it is sought to apply the estoppel of a judgment, rendered upon one cause of action, to matters arising in a suit upon a different cause of action, the inquiry must alwaj^s be as to the point or question actually litigated and determined in the original action, not what might have been thus litigated and determined. Only upon such matters is the judgment conclusive in another action.”
This same distinction is illustrated in Outram v. Morewood, 3 East 346, which is a leading case of high authority upon this subject; in Gardner v. Buckbee, 3 Cow. 120; in Betts v. Starr, 5 Conn. 550; and in the Duchess of Kingston’s Case. See, also, Washington Packet Co. v. Sickles, 24 How. 342; Davis v. Brown, 94 U. S. 423. The doctrine, as we have stated it, is consistent with our own cases: Long v. Long, 5 W. 102; Kilheffer v. Herr, 17 S. & R. 319; Smith v. Elliott, 9 Pa. 345.
But, from the year 1880 to 1887, inclusive, the city has from year to year formally rendered their claims and demanded payment of taxes from the company under the provisions of the act of 1872, which demands, as they were made, were met by prompt and full payment. These demands were for the whole, and not for any portion of the taxes supposed to be due and owing for these years, respectively, and were paid and *495receipted for in ful]. Whether the act of 1872 was in conformity with the constitution or not, was matter of law, not of fact. The city chose to treat it as a valid enactment and to' collect the tax it imposed, and, having done so, we are of opinion she must be taken to have waived or relinquished her right to receive more. She cannot in this manner repudiate the authority under which she assumed to act, to the prejudice of the company’s rights. The company accepted the results of the litigation which the city originated, and paid the taxes annually, at the rate demanded, and in accordance with the judgment of this court. Relying upon the annual adjustment of these taxes, the company, from time to time, declared dividends and distributed their surplus earnings among the stockholders, and upon these dividends, presumably larger by reason of the reduced burden of taxation, the city has from year to year received the tax at the rate demanded. Non constat that the stockholders then are the stockholders now, or were stockholders when this suit was brought. The city could not split up her claim in this way to the prejudice of the company, and we are of opinion that in so doing she must be held to have waived and relinquished her right to receive beyond the amounts from year to year demanded.
It is plain that if the parties had treated the act of 1872 as unconstitutional, and the taxes had been paid and received pursuant to the original charters, a subsequent adjudication that it was a valid enactment would not entitle the company to receive back the excess, and this is but the converse of the proposition now advanced by the city. It is said to be a poor rule that will not work both ways. The city cannot occupy inconsistent positions. Having chosen to treat the act of 1872 as constitutional, and proceeded against and treated with the company accordingly, she will not now be permitted to rip up the annual settlements, made under it, to the prejudice of others’ rights.
As to the taxes for the year 1888, and for the years subsequent to that, the city is entitled, under the provisions of the acts of 1858 and 1859.
The judgment is therefore reversed; and judgment is now entered, on the case stated, in favor of the plaintiff, and against the defendant, for «i>l,512 and costs.