GILBERT, Circuit Judge
(after stating the facts as above). [1] The appellants admit the validity of the Wilfley patent, but they contend that it covers an invention which is an extremely narrow improvement of an art which was old, and that since the invention described is for a specific improvement in that art, the claims are to be so limited as to apply closely to the apparatus described in the specifications and claims, since Wilfley patented as that feature of his invention only a specific form and arrangement of riffles, and a specific smooth surface upon the concentrating-table, and went no farther, and that when so construed the claims are not infringed by the appellants’ apparatus. The contention of the appellee is that the Wilfley invention marks a distinct advance, and discloses the application of principles and the performance of functions theretofore unknown to the art,- and that the claims thereof are entitled to a construction' commensurate with the step in advance, find that with such construction, and without expanding the Wilfley invention, the device used by the appellants will be found to infringe the same.
It is true that the use of concentrating-tables with riffles and with smooth surfaces was old, and that patents prior to Wilfley’s showed the wet concentration of ore on automatically vibrating tables having transverse riffles or corrugations for the purpose of arresting the metal and separating it from the gangue. It does not appear, however, that any of the prior patents was successful, or that any of the concentrating-tables described therein went into general use. Wilfley invented a table divided into two areas, a smooth surface and a surface covered with riffles of unequal length, the' shortest being at the top of *103the table, and the others increasing in length until the last riffle extended the whole length of the table, leaving a triangular smooth surface of about one-fourth the area of the table. In operation the pulp as it flows upon the upper side of the Wilfley table is subjected to two forces, one the endwise oscillation of the table, the other the transverse flow of water across the same. As the ore pulp is discharged upon the uppermost riffle, the side wash and the motion of the table cause the same to flow transversely over the riffles, and cause the heavier minerals to settle between the riffles in the order of their specific gravity, the gangue flowing over the top of the riffles until it is discharged from the tables. In the meantime the mineral is caused to travel forward, toward the discharge end, while at the same time it is subjected to a repeated side wash of water in a continuous operation, which removes the lighter gangue and leaves the mineral clean. The riffle cleats terminate in a diagonal line, and they restrain the material and guide it in the line of motion, causing an automatic and visible line of separation between the mineral and the gangue.
[2] The improvement made by Wilfley, as measured by the prior art and as proven by the testimony, is evidently of such merit that the claims of his patent are entitled to a reasonably liberal construction. The mere form of his table does not measure the scope of his invention. He did more than to invent a table of a precise form and configuration. He discovered a method of application of principles and an effectual mode of operation, and the appellee should be protected in that feature of the combination which is new in principle and function. In view of the evidence, we are not convinced that the court below erred in reaching the conclusion that the appellants' apparatus infringed claims 1, 2, and 7 of the Wilfley patent. In so deciding we are not unmindful of the rule that the protection afforded by a patent is to that only which is. specified in the claims, that the language of the claims is intended to convey public notice of the limits of the invention, and that, as was said by Mr. Justice Brown, in McClain v. Ortmayer, 141 U. S. 419-424, 12 Sup. Ct. 76, 77 (35 L. Ed. 800):
“Tlie object of the patent law in requiring the patentee to ‘particularly point out and distinctly claim the part, improvement or combination which he claims as his invention or discovery’ is not only to secure to him all to which he is entitled, but to apprise the public of what is still open to them.”
But form is immaterial unless it is essential to the result, or indispensable by reason of the state of the art to the novelty of the claim.
“When the whole substance of the invention may be copied in a different form, it is the duty of courts and juries to look through the form for the substance of the invention.” Winans v. Denmead, 15 How. 330, 14 L. Ed. 717; Metallic Extraction Co. v. Brown, 104 Fed. 345, 43 C. C. A. 568; Benbow-Brammer Mfg. Co. v. Simpson Mfg. Co. (C. C.) 132 Fed. 614.
The riffles in the Deister table, used by the appellants, differ from those of the Wilfley table in that each alternate riffle terminates with minute and slightly deflected ends, which have an elevation of but one thirty-second of an inch, so that at the conclusion of the separa*104tion the material is discharged into the open spaces between them. If the deflected ends were removed, there would remain a table having riffles with advancing terminals, as in the Wilfley table. We are of the opinion that the use of these deflected terminals so greatly reduced in elevation does not serve to differentiate the Deister table from that of the patent in suit, whether the space covered by them be regarded as substantially a smooth surface, as was held in Wilfley v, Denver Engineering Works Co. et al. (C. C.) 111 Fed. 760, and in Mine & Smelter Supply Co. v. Braeckel Concentrator Co. (D. C.) 107 Fed. 897, or whether they be regarded as a continuation of the riffles. There is presented in either view a table with riffles terminating in a diagonal course with reference to their general direction, a course which is essential to the successful operation of either table, and thereby the appellants have availed themselves of the distinctive feature of the Wilfley table, and therewith they have performed the same function by the same means, and in substantially the same manner, as in the Wilfley combination.
The decrees are affirmed.