where the gas is burned, obviously the length of the cylinder, or one-half the block, may be greater or less, so far as we are informed by this portion of the patent. And when this is taken with the language as to mixing in the fourth claim; with the allowance of two or more sets of air holes, one above another; with the uncertain statement of the theory ('the operation seems to be,' 'the result seems to be';) and with the statement of the air holes alone as the feature that prevents the deposit, it seems to us impossible to say that sufficient instructions are given on the supposed vital point. Again, no proportions are indicated; the number, size and position of the air holes, except that they enter the cylinder above the gas, are left at large, and if the plaintiffs' theory is the true one, the public are told little more than to try experiments until they find a burner that works. The plaintiffs say that a burner with a distance of four-fifths of an inch or over between gas and discharge orifice is a Bunsen burner, and that for the burner to be effective for illuminating purposes the distance should be only a few millimeters. But if experiment had proved the contrary we cannot doubt that they equally would have claimed the successful burner as the one Dolan had contrived.

If, as now is said, a rat-tail flame is the mark of Dolan's burner, the words "funnel shaped" in the original application were not apt to describe it, and did not purport to indicate a test. They were used merely to show how the perfect combustion was achieved which is the declared object throughout. The cause assigned was not peculiar to Dolan's tip. The amendment, in the passage as to the unaltered shape of the flame when the burner is cut off, goes on to say that 'of course' the shape, though cylindrical as it issues from the round hole, increases in diameter, 'approximating in some degree to the form of an inverted cone.' This of itself almost excludes the notion that the rat-tail shape is the test, and no reader would draw that or any similar notion from the specification as a whole.

We appreciate the difficulties that would beset an attempt to make the directions more precise, but it certainly was possible to indicate with greater clearness the specific object to be attained, and that in any ordinary burner the tip must be very short. Vacillation in theory led to uncertainty of phrase. If, however, we are wrong, then it appears to us plain that Dolan's attorney introduced not merely the theory but the mode of applying it, for the first time, in the amended specification, or, in other words, then for the first time pointed to an invention, the essence of which was to have so short a chamber or cylinder as to prevent the mixing of the air taken into it and to emit the current of gas surrounded by the greater part of such air as an envelope or film. Of course, Dolan desired to produce the result which the patented article is said to produce, but beyond that desire his specification did not give a hint of the means by which it now is said to be achieved. It spoke, it is true, as we have said, of producing a hollow-shaped funnel flame by reason of the gas being forced through contracted openings at very great pressure. But this did not disclose the invention and was dropped in the amendment. He made no claim for a process and disclosed no invention of a device. This being so, the amendment required an oath that Dolan might have found it difficult to take, and for want of it the patent is void. Rev. Stat., § 4892. Railway Co. v. Sayles, 97 U.S. 554. Eagleton Manufacturing Co. v. West, Bradley & Carey Manufacturing Co., 111 U.S.490. Kennedy v. Hazelton, 128 U. S. 667. De La Vergne Refrigerating Machine Co. v. Featherstone, 147 U. S. 209, 229.

The patent was held void below on the further ground that it had been anticipated. We turn to this last because the question is complicated with the theory that we have mentioned. If the Dolan patent had unreservedly committed itself to the notion of a cooling envelope with a contrivance made very short for the purpose of securing that result, the argument in defense of it would be that the leading earlier patents proceeded upon the opposite theory of mixture and admitted, if

they did not contemplate, a longer tube, however similar otherwise they might be. They, at least. exhibit the state of the art at the date of the supposed invention, and show within what narrow and precise limits Dolan had to move if he was to produce anything new. So much may be said to be undisputed, and we have mentioned some of the facts that cannot be denied. But on the view that we have taken of Dolan's specification, they anticipate all that he can be said to have disclosed to the public. We think it unnecessary to go over much of the disputed ground and shall mention but two of the patents put in evidence. The most important of these is one issued in France to Bullier. This also was for a tip (bec) for acetylene gas. This tip was structurally similar to Dolan's, admitting the gas through a very small orifice and having the same slanting air passages entering the cylinder above and around the gas, and, in one drawing at least, entering it very near its upper end. Bullier definitely adopted the theory of mixture and stated the proportions-40 per cent of air to 60 per cent of gas-and, after stating his preference for a duplex burner, he added that in this manner the illuminating portion of the flames is relatively far from the orifice by reason of the air introduced, and that for the same reason the combustion of the carbon is complete between the orifice and the point where the flame flattens, the flame as it issues from the orifices being blue and not illuminating. In this way, he said, he avoided any deposit of carbon. The degree of mixture is affected by the length of the cylinder or tube, and when mixture is desired naturally a longer tube would be employed than when it is to be prevented. The drawings, which are admitted to be only diagrams, indicate a longer cylinder than Dolan's, and although Bullier does not state the length it will be perceived without more that if the plaintiffs' theory and construction of their patent were adopted the distinction insisted upon by them might be held to exist. Otherwise the anticipation is complete. It is significant that some of the plaintiffs manufacture under a Bullier license in France.

The other patent to be mentioned is another French one, to Letang. He also states, as means to prevent clogging, the removal of the outlet opening sufficiently far from the point of ignition and the cooling of the burner by a current of air. This current was produced by separate plates above the gas nozzle so arranged that a certain quantity of air would be carried along by the gas. It would seem from the diagram that the distance intended to exist between the nozzle and the flame was very short. We do not dwell upon the earlier patents in more detail, because we believe that we have said enough to show that the plaintiffs' cannot be sustained.

Decrees affirmed.

MR. JUSTICE MCKENNA dissents.

LOUISIANA ex rel. HUBERT, RECEIVER, v. MAYOR AND COUNCIL OF THE CITY OF NEW ORLEANS.

ERROR TO THE SUPREME COURT OF THE STATE OF LOUISIANA.

No. 11. Argued November 1, 2, 1909.-Decided November 29, 1909. This court has not jurisdiction to review the judgment of a state court based on the contract clause of the Constitution unless the alleged impairment was by subsequent legislation which has been upheld or given effect by the judgment sought to be reviewed. Bacon v. Texas, 163 U.S. 207.

A power to tax to fulfill contract obligations continues until the obligation is discharged.

The power of taxation conferred by law enters into the obligation of a contract, and subsequent legislation withdrawing or lessening such power and which leaves the creditors without adequate means of satisfaction impairs the obligation of their contracts.

Where a municipality has power to contract and tax to meet the obligation, the proper remedy of the creditor is by mandamus to the authorities of the municipality either to pay over taxes already collected for their debt or to levy and collect therefor.

The legislature of a State cannot take away rights created by former legislation for the security of debts owing by a municipality of the State or postpone indefinitely the payment of lawful claims until such time as the municipality is ready to pay them.

Act of November 5, of 1870 of State of Louisiana providing for registration and collection of judgments against the city of New Orleans so far as it delays the payment, or collection of taxes for the payment, of contract claims existing before the passage of the act is void as impairing the obligation of contracts within the meaning of the Federal Constitution.

119 Louisiana 623, reversed.

THE facts are stated in the opinion.

Mr. Charles Louque, and Mr. J. D. Rouse, with whom Mr. William Grant were on the brief, for plaintiff in error.

Mr. Frank B. Thomas for defendants in error.

MR. JUSTICE DAY delivered the opinion of the court.

This case presents the question of the right of the relator, as receiver of the Board of Metropolitan Police of the Metropolitan Police District, consisting of the parishes of Orleans, Jefferson and St. Bernard and including the city of New Orleans, in the State of Louisiana, to compel an assessment, by mandamus, of taxes to pay a certain judgment recovered by the relator in his capacity as receiver, against the city of New Orleans, in the sum of $123,475.57, with interest from April 4, 1904.

On September 14, 1868, the general assembly of the State of Louisiana passed an act establishing a Metropolitan Police District, constituting the same of the parishes of Orleans, Jefferson and St. Bernard (including the city of New Orleans). Section 29 of that act provides:

"SEC. 29. Be it further enacted, etc., That the common councils of the cities of New Orleans, Jefferson City and Carrollton, and the police juries of the towns of Algiers and Gretna, and of the parishes of Orleans, Jefferson and St. Ber