not the defendant's profits, but those realized by other companies. This was in effect showing what, in the opinion of the master and the Court he might reasonably have made, and not those which he did make. The fallacy of this application of the rule is obvious, for nothing is more common than for one manufacturing concern to make profits where another, with equal advantages, operates at a loss. The learned judge seems to have thought that the course of the defendant, in not himself disclosing the condition of his business, justified the master in estimating his profits upon the basis of those of other similar establishments. But, as we have seen, the burden of proof was upon the plaintiff. He relied, notwithstanding defendant's objections, on incompetent and irrelevant evidence, and the decree in his favor, in so far as it awards more than nominal damages, cannot be sustained. The decree of the court below is reversed; the costs in this Court to be paid by the appellee; and this cause is remanded with directions to enter a decree for nominal damages with costs. [Supreme Court of the United States.] MILLER et al. v. EAGLE MANUFACTURING COMPANY. Decided January 8, 1894. 1. WRIGHT-CULTIVATORS—THE CONSTRUCTION OF PATENTS AND IDENTITY OF INVENTIONS THEREIN ARE Matters for THE COURT TO DETERMINE. The construction of two patents and determination of the identity of the inventions described and claimed therein are matters of law for the Court to determine. (Heald v. Rice, C. D., 1882, 215; 21 O. G., 1443; 104 U. S., 749.) 2. SAME-EArlier and LATER PATENTS FOR THE SAME INVENTION-ANTICIPATION. Letters Patent No. 242,497, dated June 7, 1881, for an improvement in cultivators, issued to Edgar A. Wright, Held to be anticipated by an earlier patent, No. 222,767, dated December 16, 1879, for improvements in wheel cultivators, issued to the said Wright, and Patent No. 190,816, dated May 15, 1877, issued to W. P. Brown. 3. EARLIER AND Later PATENTS FOR THE SAME INVENTION TO THE SAME INVENTOR. Of two patents for the same invention issued to the same inventor the later is void. (Suffolk Company v. Hayden, 3 Wall., 315; James v. Campbell, C. D., 1882, 67; 21 O. G., 337; 104 U. S., 382; Mosler Safe Co. v. Mosler, C. D., 1888, 420; 43 O. G., 1115; 127 U. S., 355; McCreary v. Pennsylvania Canal Co., C. D., 1891, 539; 57 O. G., 1131; 141 U. S., 467; Underwood v. Gerber, C. D., 1893, 340; 63 O. G., 1063; 149 U. S., 224.) 4. THE REASON FOR THE RULE ESTABLISHED BY THE ABOVE-CITED CASES. The reason for the rule established by the above-cited cases is that the power to create a grant is exhausted by the first patent, and for the further reason that a new and later patent for the same invention would operate to extend or prolong the monopoly beyond the period allowed by law. (Odiorne v. Amesbury Nail Factory, 1819, 2 Mason, 28; 1 Robb, 300.) 5. THE RESULT OF THE FOREGOING AND OTHER AUTHORITIES ON THIS POINT OF LAW-INDIVISIBLE VERSUS INDEPENDENT INVENTIONS. The result of the authorities on this point of law is that no later patent can be issued for an invention actually covered by an earlier patent, especially to the same patentee, although the terms of the claims in the two patents may differ and the later patent may contain the broader claims, but that where the later patent covers matter described in the earlier patent, which, however, is essentially distinct and separable from the invention covered by the earlier patent and claims made thereunder, its validity may be sustained. 6. SAME-MUST BE INDEPENDENT INVENTIONS, NOT MERE DIFFERENCE IN THE BREADTH OR SCOPE OF THE CLAIMS IN THE TWO PATENTS. In the last class of cases just mentioned it must distinctly appear that the invention covered by the later patent was a separate invention, distinctly different and independent from that covered by the first patent. It must consist in something more than a mere distinction of the breadth or scope of the claims of each patent. 7. THE MATTER OF DIVISION OF AN APPLICATION MAY INVOLVE THE VALIDITY OF THE PATENTS Issued on the DivisIONS. Nor, in view of the aforecited authorities, can the proposition be sustained that, whether the invention shall be protected in part of its features by one patent, and as to the rest by another, or shall be completely protected by a single patent, is a matter which concerns solely the Patent Office and the inventor. 8. SAME AS TO THE RULE of Law that Product and PROCESS, APPARATUS AND PRODUCT, and an Improvement of a Patented DEVICE MAY BE SEPARATELY PATENTED. While it is settled law that a process and its product, an apparatus and its product, and an improvement on a patented invention each may be patented in separate later patents, yet in each case the invention must be clearly distinct from and independent of the one previously patented. (Sewall v. Jones, C. D., 1876, 255; 9 O. G., 47; 91 U. S., 190; Merrill v. Yeomans, C. D., 1877, 279; 11 O. G., 970; 94 U. S., 94.) 9. SAME-SAME-THE RULE OF NO APPLICATION TO THE PATENTS IN THIS SUIT. The invention covered by the first patent (No. 222,767) consists in a spring which serves the double purpose of lifting or holding down the plows at will, the patent thus embracing both the lifting and depressing operations, and the later patent (No. 242,497) consists in the identical spring used for the single purpose of the lifting operation. The subject-matter being the same, no patentable distinction can be drawn between the two patents, and the rule above announced can have no application to the case. 10. SAME-What the SuBJECT-MATTER OF A PATENT IS. It is not the result, effect, or purpose to be accomplished which constitutes invention or entitles a party to a patent, but the mechanical means or instrumentalities by which the object sought is attained. (Pencil Co. v. Howard, 20 Wall, 507; Fuller v. Yentzer, C. D., 1877, 218; 11 O. G., 551; 94 U.S., 288.) A patentee cannot so split up his invention for the purpose of securing additional results or of extending or of prolonging the life of any or all of its elemental parts. 11. SAME-SAme-Patentee Entitled to ALL THE USES OF PATENTED Device. The invention in the earlier patent covered the means by which the results sought by the later patent were to be accomplished, and, as it is settled law that the patentee of a device is entitled to all its uses whether described or not, (Roberts v. Ryer, C. D., 1876, 439; 10 O. G., 204; 91 U. S., 105; Stow v. City of Chicago, C. D., 1882, 131; 21 O. G., 790; 104 U. S., 547,) the increased lifting effect of the spring sought to be covered in the later patent being clearly shown and described and claimed in the earlier patent, it follows that it was not the subject of a later patent. 12. SAME-EFFECT OF A RESERVATION CLAUSE IN A PATENT. This conclusion is in no way affected by the reservation attempted to be made in the earlier patent of the "broad idea of a lifting-spring which acts with increased force as the beam rises," for the reason that the broad idea sought to be reserved is embodied in identically the same mechanical device constituting the invention and covered by the first patent, which completely occupies all the ground that was reserved. 13. SAME THE CLAIMS IN BOTH PATENTS MIGHT HAVE BEEN MADE IN EITHER. The claims in both patents might have been made in either patent, as they covered one and the same invention, and to hold that the second patent, which was for one part of the invention or in its function, after such part or its action had been covered by a prior patent, presents distinct invention, or that both are valid for the same invention, would involve the drawing of distinctions too refined for the practical administration of the patent law. 14. LETTERS Patent No. 222,767 Construed-Not a PIONEER INVENTION. In view of the prior state of the art Letters Patent No. 222,767 cannot be construed as being for a pioneer device, and in consequence thereof the patentee cannot invoke the doctrine of equivalents, such as the law extends to primary inventions. 15. INTERCHANGEABILITY OR NON-INTERCHANGEABILITY OF THE ALLEGED INFRINGING DEVICE WITH THE DEVICE SUED ON-IMPORTANT TEST IN DETERMINING THE QUESTION OF INFRINGEMENT. Where the specific device described in and covered by the patent sued on could not be used in the defendant's combination, nor his device be used in the machine in the patent, this interchangeability or non-interchangeability is an important test in the question of infringement. (Prouty v. Ruggles, 16 Pet., 336; Brooks v. Fiske, 15 How., 212; Eames v. Godfrey, 1 Wall., 570.) APPEAL from the Circuit Court of the United States for the Southern District of Iowa. Mr. John T. Morgan, Mr. H. A. Toulmin, and Mr. L. L. Bond for the appellants. Mr. G. H. Christy for the appellee. Mr. Justice JACKSON delivered the opinion of the Court. The appellee, as assignee of Letters Patent No. 222,767, dated December 16, 1879, and No. 242,497, dated June 7, 1881, issued to Edgar A. Wright, for certain new and useful improvements in wheeled cultivators, brought this suit against the appellants, who were the defendants in the court below, for the alleged infringement thereof. The defenses made in that court were that Wright was not the first and original inventor of the improvements described in the patents; that the same were shown and described in previous devices and Letters Patent, set forth in the answer; that the invention shown in each of the patents in suit is identical; that in each the supposed improvements relate to a spring and its attachments; that the function and operation of the parts are exactly the same in each; that one or both of the Letters Patent in controversy were issued without authority of law, and, therefore, void; that in view of the state of the art at the date of the alleged improvements of Wright, the Letters Patent granted to him did not exhibit any patentable invention, and for that reason are invalid; that the defendants were not engaged in the manufacture of cultivators, but have sold cultivators manufactured by P. P. Mast & Co., of Springfield, Ohio, constructed under and in accordance with various Letters Patent owned by that company; that they sold the cultivators of this company without notice or reason to suppose that they were an infringement of the patents of Wright, and that they do not, in fact, infringe the same. The class of cultivators to which the Wright patents in question relate are of the ordinary character of wheeled, straddled-row cultivators, having vertical swinging beams, or drag-bars, to carry the shovels or plows, suspended from an arch or frame, mounted on two wheels a tongue fastened to the frame and beams connected with the horizontal portions of the arch, which serves as an axle for the wheels, and surrounding the axle on each side a pipe-box, to which the beam is secured, the pipe-box revolving on the axle, and the beam carrying the shovels adjusted so as to swing up or down with the pipe-box, according to the direction in which it is turned. The patented device consists of a round steel rod, or wire spring, having at its fixed end a coil attached to the swinging beam, or plow. bars, and extending from the coil a slightly-curved arm, the outer end of which terminates in a bend or shoulder, from which the rod continues to form a short arm terminating in a sharp bend, or curl, at the free end of the spring. This spring is so adjusted that the outer, or free end thereof, bears against the under side of an adjustable grooved roller, fixed upon an outwardly-extending arm upon the upright portion of the axle. This spring, with its adjustment, is intended to have a duplex action, covering the double effect, of either raising or depressing the beams carrying the shovels. The curvature of the spring is such that as it moves along the groove of the roller it presses against the latter at different points of its periphery, and thereby the direction of its action is shifted or changed, as the position of the swinging beam is changed. Such changes in the direction of its action will assist in drawing or pulling the beam upward in a vertical direction, giving it increased leverage as the spring is moved forward in its bearings on the roller. In his original application, filed May 23, 1879, Wright fully described his improved device for use in connection with cultivators and claimed for it, not only its lifting and depressing action, but also its lifting power, which increased as the beams were raised. An interference with other pending applications being anticipated as to the broad claims of the invention, the application was divided, on November 12, 1879, for the purpose of obtaining one patent for the lifting and depressing effect of the spring on the beams, and another for the lifting power of the spring, increasing as the beams rise, the latter being sought upon the original application, while the former was based upon the divisional application of November 12, 1879. Patent No. 222,767, for the double effect or duplex action of the improved spring, was granted on December 16, 1879, and thereafter on June 7, 1881, Patent No. 242,497, for the single effect of increased lifting force in raising the plow-beams, was granted, after interference had been disposed of. The court bel w sustained the validity of both patents, and held that the defendants infringed the first, second, third, fourth, and sixth claims of Patent No. 222,767, and the first, second, third, and fourth claims of the patent granted June 7, 1881, (No. 242,497.) The complainant waiving an accounting for profits and damages, a final decree was entered, enjoining the defendants from making, using, or selling to others to be used, cultivators constructed and operated in the manner, and upon the principle described in the Letters Patent in controversy. From this decree the present appeal is prosecuted. The appellants assign numerous errors, which need not be separately noticed and considered, as they are embraced in the general proposition that the court erred in holding that the patents sued on were valid, and that the cultivators sold by the defendants infringed the same. In the specification, forming part of the Letters Patent No. 222,767, issued December 16, 1879, under the divided application filed November 12, 1879, the patentee states: The object of my invention is to give the operator mechanical assistance in raising and lowering the plows without interfering with their usual action and movement, to prevent the plows from rising out of the ground accidentally, and to limit their descent; and to this end the invention consists in a spring which serves the double purpose of lifting or holding down the plows at will, as may be required; in so constructing and applying a spring that it exerts a lifting action on the plow only when the latter is raised above its usual operative position; in so constructing and applying a spring that it limits the descent of the plow; also, in details of minor importance, hereinafter described. In carrying out my invention the one spring may be adapted to serve all or either one or more of the offices above enumerated, and may be modified in its form, construction, and arrangement, as desired, provided its mode of action is retained. It further stated that the improved springs may be attached to either the plows, as shown in Figs. 1 and 2, or to the axle, as shown in Fig. 3. The improvements are described in the specification as follows: As shown in Figs. 2 and 3, each spring consists of a round steel rod or wire having at the fixed end a coil, a, and extending from the coil a long slightly-curved arm, b, the outer end of which terminates in a sharp bend or shoulder, c, from which the rod continues to form a short arm, d, the end of which has a sharp bend or curl, e, as represented in Figs. 2 and 3. When the spring is to be applied to the plow-beam, as shown in Figs. 1 and 2, I first provide the upright portion of the axle with an outwardly-extending arm or rod, E, carrying a laterally-adjustable grooved roller, F. to serve as a bearing for the free end of the spring. The coiled end of the spring is then seated in a metal bearing-plate, G, which is secured rigidly but adjustably to the beam by means of a bolt, HI, as shown, the free end of the spring being at the same time scated against the under side of the |