lion, and long prior to the alleged patent or invention of the said Brady and the dates of his patent or caveat, and one of which said light-draft monitors was built at the works of these defendants."

The answer further stated that in 1866 and 1867, prior to the date of Brady's alleged invention, he was acting as agent for one Tyler, in carrying out a contract with the government for the improvement of the mouth of the Mississippi River; that General McAlester was then stationed at New Orleans to supervise and inspect, on behalf of the United States, the execution of the contract; that Brady was fitting and preparing a steamboat for the purpose on a plan entirely different from that of his alleged invention; that McAlester then detailed and described to him a plan for a dredge-boat identical with that of the boat constructed by the defendants; which plan McAlester communicated to the board of engineers of the army before the date of the alleged invention by Brady; that Brady's boat was a failure, and the contract was annulled; that then Brady made drawings for a boat on the plan described to him by McAlester, and afterwards claimed to be the inventor of it, and made application for his patent, and obtained the same after the defendants had commenced work on the boat complained of.

Evidence was taken, and on a hearing before Mr. Justice Clifford, in September, 1876, a decree was made sustaining the patent, declaring that the defendants had infringed the same, and referring it to a master to take an account of the profits received by the defendants from the infringement. The master reported the sum of $6,604.82. Both parties excepted, but their exceptions were overruled, and a final decree, in accordance with the report, was rendered Oct. 9, 1878, with costs. Both parties have appealed.

The most important question, and first to be considered, is the validity of the patent.

It is obvious from reading the specification that the alleged invention consists mainly in attaching a screw (which the patentee calls a mud-fan) to the forward end of a propeller dredge-boat, provided with tanks for settling her in the water. It is operated by sinking the boat until the screw comes in contact with the mud or sand, which, by the revolution of the

screw, is thrown up and mingled with the current. The use of a series of tanks for the purpose of keeping the vessel level whilst she settles is an old contrivance long used in dry-docks, and is shown, by the evidence, to have been used in many lightdraft monitors during the late war. The defendants themselves built one of these vessels, the "Casco." Mr. Edwards, the president of the Atlantic Works, in his testimony, says: "The Casco' was built double, leaving a water-space on each side nearly the entire length of the vessel, with an arrangement of valves for flooding the compartments at pleasure, for the purpose of sinking the vessel to the desired draft of water, and with powerful steam-pumps to pump the water out for the purpose of raising it in the water. The compartment on the side was divided into several, and one or all of them could be filled as desired. The object was to enable them to put her on an even keel, or to raise or depress one end at pleasure." The employment of their screws by propeller ships, driven stern foremost, for the removal of sand and mud accumulated at the mouths of the Mississippi, had frequently occurred years before the patentee's invention is alleged to have been made. Several French steamers, one of which was named the "Francis Arago," had used this method there prior to the year 1859. In that year the "Enoch Train," a double propeller, that is, having two screws at her stern, was used in the same way by certain contractors under the government, for dredging the mouth of the Mississippi. Mr. Hyde, one of the contractors and owners, in his testimony, describes her construction and operation as follows:

"She was a propeller of burden between three and four hundred tons, with two propeller screws at her stern, about nine feet in diameter each; the cylinders were thirty-six inches in diameter and thirty-four inches stroke; she had one doctor engine; was fitted also with a large wrecking pump, with two lowpressure boilers; engines were also low-pressure engines. Her draft of water, in ordinary trim, with three hundred barrels of coal on board, was about thirteen feet aft, and a little less at the bows. By ordinary trim I mean the usual sailing trim. The propeller screws were one on each quarter, or each side of the stern-post. Before going to dredging on the bar, I fitted her up

with a water-tight apartment, or tank, at the stern, by a bulkhead running ath wartships, say about twenty or twenty-five feet from the stern. That space was divided by a fore-and-aft bulkhead, making two water-tight compartments.

"The mode of filling the compartments was by stop-cocks in the sides of the vessel opening into the water-tight compartment; the draft of water could be increased from her natural draft of water, say thirteen feet to eighteen feet, according to the quantity of water let into the tanks. The mode of operating was by running the vessel up and down over the bar, and thus stirring up the mud with the propeller screws. When the water was too shoal for her to pass over, the stern of the vessel was turned to the bar, and she was run stern on, the engines being reversed. Whenever we got done working on the bar there was a valve in the water-tight compartments for letting the water into the hold of the vessel, from which the water was pumped out of the vessel, by the steam-pumps, and the vessel would then be left at her ordinary draft.

"Int. 13. Please to state how you happened to employ this mode of dredging by the Enoch Train.'

“Ans. Well, I thought it would be an effectual way of removing the mud from the bar; that by the screws coming in contact with the mud and deposit, and the revolutions of the screws about sixty times a minute, would create a current of water by which the sediment would be washed away."

The evidence of Henry Wright, the master of the "Enoch Train," under whose charge her operations were conducted, is to the same purport. He says:

"We used to work our propellers in cutting up the mud. The operation consisted in cutting through the mud with our propellers. Sometimes we went at the mud stern foremost, sometimes sideways, and sometimes bows on. When I went to the bar at first there was about fifteen feet of water on it, and when I quit operating there were eighteen feet on it in most places. Where the water was shallow we invariably went at the mud stern foremost. The stern was always loaded down to eighteen feet when dredging, but the bows were not loaded down. In dredging, the stern was always several feet lower down than the bows, say three or four feet."

The boat built by the defendants, which was called the "Essayons," was operated in precisely the same way. Being built expressly for dredging, her dredging screw was placed at her stem, it is true; but her mode of operation was the same as that of the "Enoch Train." Her master, Putnam, describes it as follows:

"The method we use is to go outside the bar into deep water; then we sink the dredging end of the vessel, by filling up the tanks at that end with water to any depth required. Then we start the propelling screw at the other end of the vessel, and go in with that until the vessel grounds; then we stop the propelling screw and start the dredging screw, and as that screw revolves it cuts up the mud at the bottom and drags the vessel after it at the same time; after going as far as we wish we stop the dredging screw, lower the rake at the dredging end, and back out into deep water, using either or both of the screws to go back with, thus dragging the mud after us that the dredging screw has cut up from the bottom, and carrying it out into deep water; or rather, the operation is, that the dredging screw agitates the mud and throws it up into the surface current, and the current takes it out to a large extent, while the rake takes fresh hold of the bottom and also carries out whatever is broken up by the screw and settles from the current. After backing out into deep water, we hoist the rake and go back again and repeat the operation. When we first arrived at the bar we made several experiments as to the best mode of dredging, but the mode above described we found to be the correct one, and have ever since used."

Nearly all the witnesses examined on the subject declare that there is no difference in principle between the mode of operation of the "Enoch Train" and that of the " Essayons." The scraping or raking apparatus is not mentioned in the plaintiff's patent at all. This, as will be hereafter seen, is part of the original design of General McAlester, the govern ment officer who had charge of the improvement of the mouth of the Mississippi.

It is further noticeable that the "Essayons," as is abundantly established by the evidence, always worked with her stem

sunk and depressed, and never with an even keel, upon which special emphasis is placed by the patent in suit.

It may well be asked, at this point, Where was there any invention in the device described in the patent? Was it invention to place a screw for dredging at the stem of the boat? Nothing more than this was in reality suggested by the patentee. And that was substantially what was done with the French steamers prior to 1859, and with the "Enoch Train" in that year. They were turned end for end, and the stern was used as the stem, and the scre went forward, working in the bottom deposit in advance of the vessels. When the "Enoch Train" was procured for the service which she performed, she was ready made, and the contractors, to save time and expense, simply supplied her with a tank, in order to settle her to the proper depth, and they found her very serviceable. Had she been built for a dredge-boat, with the design of using screws for dredging (as she did use them), can it be doubted that her dredging screw would have been placed forward instead of turning her stern forward? Would not this have been suggested by ordinary mechanical skill? The plan and mode of operation would have been precisely the same. When, after this, the government proceeded to build a boat expressly for dredging the mouths of the Mississippi, we should naturally expect to find it built as the "Essayons" was built, with her dredging screws at the stem instead of the stern. The making of them with longer blades than those of the propelling screw, and sharpened at the points, would be a matter of course. No invention would be requisite for any of these arrangements. It seems to us that the whole principle of the Essayons's" construction and furnishment, as well as that of the patent in question, was anticipated by the "Enoch Train," if not by the French steamers, and that a patent for that principle, though qualified by the natural incidents and adjuncts of its application, ought not to be sustained.

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The process of development in manufactures creates a constant demand for new appliances, which the skill of ordinary head-workmen and engineers is generally adequate to devise, and which, indeed, are the natural and proper outgrowth of such development. Each step forward prepares the way for