This is a case in equity. On the 15th of January, 1864, Hill, the appellant, executed a deed of trust to Edward Shoemaker, conveying in fee simple four lots in Georgetown to secure the payment of three promissory notes therein described. The notes were executed by Hill. All of them bore date on the 21st of October, 1863, and were payable to the order of Judson Mitchell and John Davidson. They were each for the sum of $2,210.33, and were to be paid respectively, at one, two and three years from date, with interest at the rate of six per cent. per annum to be paid half yearly. In the event 451] of any default of payment by Hill, the trustee was authorized to sell the premises for the satisfaction of the debt. The lots were numbered 1, 2, 3 and 4, and were all contiguous. On each of three of the lots there was a brick tenement. Lot 4 was unimproved. The appellant bought the premises with the view of using them for a paper-mill. This purpose he proceeded to carry out. He altered the buildings, put in the requisite machinery, and took a lease of water-power from the Chesapeake and Ohio Canal Company, "To be used at his property at the corners of Potomac and Water Streets (being the premises in question), and to be used in propelling the machinery of a paper-mill and appurtenant works." He introduced the water upon the premises, and applied it according to the terms of the lease. The several notes were duly assigned and transferred to the complainant. Hill having made default by allowing all the notes to become overdue without payment, the trustee, under the power conferred by the deed, advertised and sold the real estate as it was when the deed was executed, and irrespective of the water-power and the paper-mill machinery. A bill was thereupon filed by Hill to set the sale aside. The Supreme Court of the District sustained the bill and annulled the sale, upon the ground that the realty, the water-power and the machinery constituted an entirety, and should have been sold together. The court said: "The complainant placed in these structures, at great expense, all the machinery necessary to a paper-mill, and procured from the Chesapeake and Ohio Canal Company a water-power, which he conveyed underground some three or four hundred feet to the mill property, for the purpose of operating the machinery, and also incurred a heavy expense for an underground tail-race, to conduct the water way. many cases applied together: actual annexation to the realty, or to something appurtenant thereto; application to the use or purpose to which the realty is appropriated; the intention of the party making the annexation to make it a permanent part of the realty. Teaff v. Hewitt, 1 Ohio St., 511; Ottumwa Woolen Mill Co. v. Hawley, 44 Iowa, 57, 24 Am. Rep., 719; Thomas v. Davis, 76 Mo., 72; Clore v. Lambert, 78 Ky., 226; McRae v. Cent. Natl. Bk., 66 N. Y., 489; St. Sav. Bk. v. Kercheval, 65 Mo., 682; McMillan v. N. Y. W. P. P. Co., 29 N. J. Eq.,610. The following authorities hold that the rolling stock of a railroad is part of the realty: Meyer v. Johnston, 53 Ala., 332; Douglass v. Cline, 12 Bush. 630; Morrill v. Noyes, 56 Me., 458; Youngman v. Elmira, etc., R. R. Co., 65 Pa. St., 278; Farmers,' etc., Trust Co. v. Hendrickson, 25 Barb., 484; Scott v. Clinton, etc., R. R. Co., 6 Biss., 529; Galveston, etc., R. R. Co. v. Cowdrey, 11 Wall. 459, 20 L. ed., 199. Other authorities hold that it retains the character of personal property: Williamson v. N. J., etc., 29 N. J. Eq., 311; Coe v. Col., etc., R. R. Co., 10 Ohio St., 372; Hoyle v. Plattsburgh, etc., R. R. Co., 54 N. Y., 314, 13 Am. Rep., 595. Statute regulates this in some States. Laws of N. Y., 1868, chap. 779; Civil Code of Cal., sec. 2955, et seq. The great mischief done, as we think, was not in selling the lots together, but in selling them without reference to the fixed machinery and water-power connected therewith. We are governed in our conclusion in setting this sale aside by the fact that both parties had a right to permanent improvements upon the premises, so far as the same were inalienably fixed upon each other, and that there was no exclusive right of either to divide them." *This bill was thereupon filed by the [452 Bank against Hill and the Chesapeake and Ohio Canal Company to enforce the payment of the amount due upon the notes by a decree for the sale of the lots described in the deed of trust, together with the water-power and machinery used upon the premises, if the court should deem that the two latter could be included in the sale. The court below finally decreed "That the said real estate and premises, including said fixtures and machinery, and also said waterpower, according as the same are referred to. mentioned or described in said bill, be sold as an entirety, and as forming and being a paper manufactory, according to a suitable description thereof, to be made for the purpose of a sale by the trustees to be hereinafter appointed to make said sale." This decree was affirmed at the General Term. The appellant has brought the case here for review, and assigns three errors: (1) That the court erred in decreeing the sale of lot 4 with the other property. (2) In decreeing the sale of machinery not permanently annexed, without evidence as to the mode, object and intention of the annexation. (3) In decreeing the sale of the water-power as appurtenant to the land. The appellant does not deny that the debt is bona fide; that it is overdue; that it belongs to the appellee; nor that the decree is for the proper amount. His objections are only those assigned as errors. To all three of them there is a common answer. The points are res judicatæ between the parties. In setting aside the sale made by the trustee, upon the appellant's bill filed to bring about that result, the court adjudged, expressly, that the entire premises, including lot 4 and the machinery and waterpower, should be sold together as an entirety; and the sale was set aside because it was not so made. The appellant now asks that the decree before us be reversed, because it requires the sale to be made in the manner prescribed in the former case. This cannot be done. The ques Mortgagees stand upon the same footing as to fixtures as ordinary purchasers, and are entitled to everything constructively or actually annexed to the freehold., Quinby v. Manhattan, etc., Co., 24 N. J. Eq., 260; Voorhees v. McGinnis, 48 N. Y., 278; Maples v. Millon, 31 Conn., 598; McKim v. Mason, 3 Md. Ch. Dec., 186; Walmsley v. Milne, 7 C. B. N. S. 115; Ex parte Colton, 2 M. D. & DeG., 725. A steam-engine and boiler, with the appurtenances, and the shafting, belting, pulleys and couplings to communicate the power, are fixtures which pass under a mortgage of the realty. Bigler v. Nat. Bk., 26 Hun, 520; Coleman v. Stearns Mfg. Co., 38 Mich., 30; Keeler v. Keeler, 31 N. J. Eq., 181; Ottumwa Woolen Mill Co. v. Hawley, 44 Iowa, 57, 24 Am. Rep., 719. A portable iron furnace held not a fixture (Rahway Sav. Inst. v. Irving St. Bapt. Ch., 36 N. J. Eq.. 61); nor gas fitting screwed onto the pipes; nor mirrors supported by hooks driven into the wall (MeKeage v. Hanover F. Ins. Co., 81 N. Y.. 38, 37 Am. Rep., 471); nor heavy machines screwed to the floor and connected with the shafting, but remov. able without injury to the factory. Hubbell v. E. Cambridge, etc., Sav. Bk., 132 Mass., 447, 42 Am. Rep., 446. 1. Where an invention is developed in different and independent forms, all original and yet all bearing a somewhat general resemblance to each other, if one inventor precedes all the rest and strikes out something which includes and underlies all that they produce, he acquires a monopoly and subjects them to tribute. 2. But if the advance towards the thing desired is gradual and proceeds step by step, so that no one can claim the complete whole, then each is entitled only to the specific form of device which he pro duces. tions raised by the assignments are concluded But, irrespective of this consideration, we think the decree appealed from is correct. It is not questioned that the realty, the waterpower and the machinery constituted a papermill. They were, therefore, ex vi termini, a unit, and could not be disintegrated and the parts sold separately without large depreciation, and a diminished amount in the aggregate of the yield. It is, obviously, best for all concerned that the property should be sold pursuant to the decree. According to the terms of the lease, the water-power could be employed only on the premises, and for driving there a paper-mill. Lot 4 is convenient and important for use in connection with the rest of the property, and hence should be sold with it. That lot is the only vacant and unimproved part of the premises, but it is not on that account the less necessary for various purposes in operating the estab Eshment. Olcott v. Bynum, 17 Wall., 44, 21 L. ed.. 570. Without the water-power the machinery would be worthless, except to be torn out and removed. By placing it in the buildings in constructing the mill, every part and parcel of it, as between mortgagor and mortgagee, became a fixture and a part of the freehold. There is some conflict in both the English and American authorities upon this subject; but we think the view we have expressed is the better one, and sustained by the greater weight of authority. The intent and conduct of the mortgagor, under the circumstances of this case, are conclusive. Ex parte Astbury, L. R., 4 Ch., 630; Metropol. Co. Soc. v. Brown, 26 Beav., 454; Christian v. Dripps, 28 Pa., 271; Hill v. Sewald, 53 Pa., 271; Seeger v. Pettit, 77 Pa., 454] 437; Palmer v. Forbes, 23 Ill., 301; Deal v. Palmer, 72 N. C., 582; Walmsley v. Milne, 7 C. B. (N. S.), 115; Powell v. Mfg. Co., 3 Mas., 459; Trull v. Fuller, 28 Me., 545; Corliss v. McLagin, 29 Me., 115; McKini v. Mason, 3 Md. Ch., 187; Winslow v. Ins. Co., 4 Met., 306. The decree of the court below is affirmed. 3. The Stevens brake for cars is no infringement on that of Thompson and Bachelder's or Tanner's. 4. The law does not permit such enlargements of other subsequent inventors. an original specification as would interfere with [No. 84.] 1878. Appeal from the Circuit Court of the United States for the Northern District of Illinois. The case is very fully stated by the court. An outline representation of the brakes directly in controversy is given, to aid a clear understanding of their similarities and differences. The other brakes, invented and used prior to either the Stevens or the Tanner brake, which are referred to in the opinion for purposes of comparison, will be sufficiently understood from the description given in the opinion. BRAKE BRAKE BRAKE LEVER LEVER BRAKE Fig. 2. These figures represent in each case only one end of the car. The other end of each car is exactly like the one here given. Reversing the ends of course reverses the sides, as the figures show to be necessary in order to connect the rods into one system. The Tanner brake, which the appellee alleges has been infringed by the appellant, is shown in Fig. 1. The Stevens brake, which is alleged to be an infringement on the Tanner brake, is shown in Fig. 2. Messrs. George Payson, B. C. Cook and A. J. Poppleton, the argument of B. R. Curtis, in the circuit court being also filed, for appellant. Messrs. S. D. Cozzens and Albert H. Walker, for appellee. Mr. Justice Bradley delivered the opinion of the court: This suit was commenced in the Circuit Court in December, 1861, by bill in equity filed by the appellee, on letters patent, for an improvement in railroad car brakes, issued on the 6th day of July, 1852, to Henry Tanner, as assignee of Lafayette F. Thompson and Asahel G. Bachelder. The bill charged that the defendant, from the 1st of June, 1859, to the time of filing the bill, infringed and was still infringing the said patent, of which the complainant had become the owner, and prayed for an injunction and an account of profits received by the defendant from the use of the invention patented. The defendant answered, setting up prior invention and use by others of the improvement claimed, and denying infringement. After proofs taken, a decree was rendered for the complainant in February, 1865, and a reference ordered. This decree was afterwards opened, and the defendant was allowed to introduce newly discovered evidence. A decree was again rendered for the complainant in July, 1871, and reference again ordered. The master reported profits received by the defendant, for the period of five years, from June 2, 1859, to June 2, 1864, to the *amount of $63,638.- [556 40, being $41,280 for saving in wages of brakemen, and $22,358.40 for saving in car wheels. A decree was rendered for the whole amount in December, 1873; but on a further rehearing in September, 1875, the item for saving on carwheels was apparently thrown out, and the decree was reduced to the sum of $47,725. From this decree the present appeal is taken. The counsel for the appellee now concedes that, in the light of our decision in Mowry v. Whitney, 14 Wall., 620, 20 L. ed., 860, the principle adopted by the master was not correct, and consents that the decree be further reduced to the sum of $24,768, with interest from the date of the report. The evidence in the case is very voluminous, especially in reference to the question of priority of invention, and would be well calculated to present questions of much embarrassment and difficulty for our determination, if we felt obliged to pass upon the validity of the patent. But as we are satisfied that the Stevens brake used by the defendant is not an infringement of the plaintiff's patent, we are relieved from that unpleasant and difficult duty, involving the weight of evidence given by witnesses speaking to facts and occurrences long passed, and often in direct conflict with each other. At the time when the complainant alleges that Thompson and Bachelder completed the invention for which the letters patent on which the suit is brought were granted, namely: in 1846 and 1847, double trucks under railroad cars had come into general use in the country, and it was a desideratum to have a brake, or system of brakes, which could be operated from either end of the car, upon the wheels of both trucks; and a number of inventors were in the field, contriving and testing their various devices. Like almost all other inventions, that of double brakes came when, in the progress of mechanical improvement, it was needed; and being sought by many minds, it is not wonderful that it was developed in different and independent forms, all original, and yet all bearing a somewhat general resemblance to each other. In such cases, if one inventor precedes all the rest, and strikes out something which includes and underlies all that they produce, he acquires a monopoly, and subjects them to tribute. But if the advance towards the thing desired is gradual, and proceeds step by step, *so that no one can [557 claim the complete whole, then each is entitled only to the specific form of device which he produces, and every other inventor is entitled to his own specific form, so long as it differs from those of his competitors, and does not include theirs. These general principles are so obvious, that they need no argument or illustration to support them. We think they are specially applicable to the case before us. The patent sued on was granted on the sixth day of July, 1852. It was not the first patent granted for double car brakes. A patent for such a brake had been granted to one Charles B. Turner, on the 14th of November, 1848; another to Nehemiah Hodge, October 2, 1849; and a third to Francis A. Stevens, November 25, | the car body they attached thereto, by a pivot, 1851; and double acting brakes had been con- a vibrating horizontal lever, situated midway structed by other persons before any of these between the trucks, and arranged crosswise of patents were issued. The patent granted to the car. To the outer ends of this lever were Tanner antedates the other patents referred to, attached connecting rods, one of which extended by reason of its being issued upon an applica- to and connected with the truck lever on one tion for a patent made by Thompson and Bach- of the trucks; and the other extended to and elder, on the 29th of June, 1847. It is alleged connected with the truck lever on the other by the complainant that Thompson and Bach- truck. By this arrangement, when one of the elder completed their invention as early as the truck levers was forced inward, towards the fall of 1846, and made a model of it in January, center of the car, it would push back the con1847, a copy of which is put in the case. The necting rod attached to it, and cause the vibratapplication filed by them in the Patent Office in ing lever to revolve on its pivot, and thus draw June, 1847, is the first authentic evidence, of a the other connecting rod towards the center public character, of what their invention was. from the other direction, and force the truck A copy of this application and of the drawings lever on the other truck *inward at the [559 and model by which it was accompanied have same time. Thus when the windlass was wound been exhibited in evidence, and necessarily con- up at either end of the car, it had the effect of stitute an important feature of the case. Being operating the brakes on both trucks, by pushing regarded as defective and insufficient by the one connecting rod at the same time that it Patent Office, no patent was granted at the worked the truck lever, and simultaneously pulltime, and the application lay dormant and with- ing the other connecting rod. The bumpers proout alteration for the space of five years; when, duced the same effect by having gains cut into being purchased by Tanner, and being consid- their sides for receiving the upper arms of the erably modified and changed, the letters patent truck levers, and thereby forcing them inward now in question were issued to him as assignee when driven inward themselves. A long iron of Thompson and Bachelder. It is obvious that rod extended the whole length of the car, which the original exhibit of the invention made by was provided with a device for forcing the truck them, and remaining so long in the Patent Of levers out of the gains in the bumpers when it fice unchanged, should possess great weight as was desired to ease the brakes. to what their invention really was, and what they claimed it to be. Of course their object was to connect the brakes of the two trucks together in such a manner as to make them operate together by the application of force at either end of the car. This force they proposed to apply either by 558] hand at the windlass on the platform, or by the bumpers when the train was slowed and the cars came together. The latter seems to have been their favorite plan, and to effect it was one of the principal objects of their im provement. The system of brakes attached to each truck was not materially changed by them. An upright lever in the center of the truck was so connected with the brakes on both pair of wheels as to draw them tightly to the wheels when its upper extremity was forced inward towards the center of the car. To this upper extremity of the lever the external force was applied when the brakes were to be put on. The inner end of the bumper being attached thereto, produced the desired effect when the bumper was pushed in by the adjoining car. The same effect was produced by winding up the windlass by hand, by means of a chain and pulley working from a point inside of the lever; that is, nearer to the center of the car. Such, substantially, was Thompson and Bachelder's brake, according to the description thereof deposited and left by them in the Patent Office. In the new application, filed in their name by Tanner in 1852, the bumper arrangement was left out entirely and, as before stated, considerable modifications were introduced. The connecting rods were attached to the vibrating lever nearer to its pivot, and two additional rods were applied to the outer ends of this lever, extending respectively to the two windlasses at either end of the car, being used for the purpose of working the lever; and the parts were so arranged as to supply the power by drawing or pulling both of the connecting rods, instead of pushing one and pulling the other. Now, in 1847, when Thompson and Bachelder filed their application for a patent, and in 1846, when it is said they completed their invention, double brakes were already in existence, formed as theirs was (though not in the same manner), by connecting together the movements of the two systems of truck brakes, so that one brakeman, at either end of a car, could apply the brakes to both trucks at the same time. Without noticing those inventions, the dates of which are disputed, it is sufficient to refer to two instances in point, the existence of which before 1846 cannot be seriously controverted. We refer to those known as the Springfield brake and the Millholland brake. These brakes may not have been, and were not, so perfect as that of Thompson and Bachelder, and others constructed at a later period; but they were used, and used successfully; sufficiently so, at least, to have sustained patents for the inventions, had patents been applied for. The next point was to communicate this movement of the brakes in one truck to those of the other, by some device that would cause the upper extremity of the lever, in the latter, to be drawn inward, towards the center of the car, at the same time that the lever on the first truck was forced inward; a simple rod connecting them together would not do this, but it would have the contrary effect. The upper extremities *The Springfield brake was made by [560 of the two levers must be so connected that, up- one Harris, in 1842 or 1843, and placed on a on the application of force, they would approach long platform car for carrying freight crates on each other, each being forced inwardly towards the Western Railroad of Massachusetts. Each the center of the car. To effect this, Thompson truck was provided with two levers, one to each and Bachelder proposed a device constructed of the brakes; and these levers were connected substantially as follows: under the center of together by a rod which caused them both to be operated at the same time by the windlass which was connected by a short chain to the nearest one. A long rod connected one of the levers of the other truck to the same windlass by means of another chain, so that when the windlass was worked it wound up both chains and operated the brakes on both trucks simulta neously. A like arrangement was connected with the windlass at the other end of the car. Each windlass could thus be made to operate the brakes of both trucks. This brake was used, as we gather from the evidence, for a year or two, until the car was broken up. It was undoubtedly attended with some inconveniences in its operation, especially in going around sharp curves; but this did not prevent it from being used; and on a straight track or on a track having only slight curves it operated very satisfactorily. In 1856 and 1857, when some difficulty arose about the right to use another brake, the employment of this Springfield brake was resumed for more than a year on the passenger cars of the same railroad, with only the slight and obvious modification of attaching the long connecting rod to a lever in each of the trucks, instead of attaching it to the windlass at one end of the car, and to a lever in the truck at the other end. It is useless to argue that this brake was an imperfect one, or that it worked far less satisfactorily than the Tanner or other brakes. It did work; and under favorable circumstances worked as well as the most improved form of brakes. The same brake with only a single windlass, was applied to tenders (which require and admit of only one windlass) as early as 1841, and continued to be thus used to the time of this litigation. The Millholland brake approached much nearer in its mode of operation to the Tanner brake than did the Springfield. According to the testimony, it was placed on a passenger car of the Baltimore and Susquehanna Railroad in or 561] about the year *1843, and was continued in use for a considerable period, one witness says, a year or eighteen months. It was taken off because the brakemen were opposed to it, inasmuch as it had to be worked by hand by means of a windlass, whilst they were used to brakes that were operated by the foot. Whilst used, however, it worked with entire success. It is thus described by the inventor, James Millholland. in his testimony. He says: "It broke upon all the eight wheels from either end of the car; the brakes were operated by means of a drum placed under the car, about the center; there were connections running from this drum to the levers on each truck, and also from the drum to the windlasses of the car." He then describes the manner in which the connecting rods were attached to the truck lever, and their mode of operation. It is apparent from this description that the drum performed almost pre cisely the same office which is performed by the vibrating lever in the Tanner brake, operating, by means of the connecting rods, upon the brakes in nearly the same manner. In 1846, Millholland applied a double brake somewhat like the last named to car tenders, using a rock shaft with an arm on it instead of the drum as means of connecting the brakes to the two trucks. This brake was continued in use for many years. But The subsequent invention of double brakes of improved and better forms superseded these early brakes, it is true; so that, excepting the modified forms in which they were applied to tenders, and excepting the temporary resuscitation of the Springfield brake in 1856, and again in 1871, they went entirely out of use. their construction and use, though with limited success, are sufficient to show that Thompson and Bachelder were not the pioneers in this field of improvement, and that they were not the originators of the double brake, nor of the use of rods, chains and similar appliances for connecting the brake systems of two trucks under a car. They invented a particular apparatus for doing the desired work; and they can only claim their particular apparatus, or that which is substantially the same. This brings us to the question whether the apparatus used by the defendant, and known as the Stevens brake, is substantially the [562 same as Thompson and Bachelder's, or whether it contains in it anything substantially the same. They Now, the Stevens brake has no vibrating lever between the trucks, as the Tanner brake has, for the purpose of reversing the motion communicated from one truck system to the other and causing the truck levers to move in opposite directions, that is, towards each other when the brakes are put on, and away from each other when the brakes are relieved. This is a marked feature in the Tanner brake, and one on which stress is laid in the original application. The parts particularly pointed out by Thompson and Bachelder as their improvements, exclusive of those connected with the bumpers, are only these three, namely: the vibrating lever, the two rods connected therewith, and their connection with the truck levers. speak of their improvement as "An improvement upon the car brake now in general use." expressly disclaiming its original invention. This language is somewhat vague; but it sufficiently indicates that they regarded their improvement as consisting in their particular apparatus for effecting the desired result. The claim of the patent as finally issued to Tanner is only for so combining the brakes of the two trucks by means of the vibrating lever, or its equivalent, or mechanism essentially as specified (and no other is specified), as to enable the brakeman operating the windlass at either end of the car to simultaneously apply the brakes of both trucks. Now the apparatus for effecting the same purpose in the Stevens brake is essentially different from this. As before stated, it has no central vibrating lever at all and, as we think, no equivalent of it. It connects the brakes of the two trucks by a single straight rod, extending from the truck lever connected with the outside brake of one truck to the lever connected with the outside brake of the other truck. This outside lever in each truck is connected, by a rod running across and under the axles of the truck, with a similar lever attached to the inner brake of the same truck; and that again is connected with the windlass by another rod running back over the axles of the truck; thus establishing a direct and continuous connection, from one windlass to the other, between all the brakes in both trucks, so that when either windlass is wound up (the other being held by a [563 ratchet), it winds up and tightens the whole |