(after stating the facts as above). Appellee’s primary valve, instead of being a disk, as described in the *113Glauber patent, is plug shapedand instead of being removable from the stem, is integral with the stem. Upon these differences chiefly the argument' of non-infringement is based. But these are differences of construction only. Appellee’s device performs the same function, and brings about the same result, as the Glauber patent. The function is the prevention of the sudden shutting off of the water column or other fluid under pressure, thereby relieving the strain, for an interval, during which the water or fluid column continues to flow in a sheet or film around the primary valve—the result being the prevention of hammering; so that whether the appellee’s device is an infringement of the Glauber patent or not, depends upon the scope of that patent; for if the Glauber patent is for the mere specific form of performing that function, embodied in the disk shaped primary valve, and further limited by its removability, appellee’s device is not an infringement; but if the Glauber patent is more generic—embodies a discovery carried out by suitable mechanical means or their equivalent—appellee’s device, notwithstanding the slight difference in form, is an infringement.

With that in view it is to be noted that the removability of the Glauber patent is no essential part of his combination. It is introduced because, as the patent says “it enables me to adapt the valve to faucets of different sizes and kinds, and it also enables me to place the primary valves on faucets now in use, so that old faucets can be equipped with them, and made as good as new ones, so far as hammering is concerned,” which makes it a mere incidental advantage, not a function of the combination.

Nor is the Glauber patent limited to the peculiar form of disk shown in figure 1. The description in the claim is “a substantially disk shaped primary valve.” “Disk” as described in the Century Dictionary is “any flat or approximately or apparently flat circular plate or surface.” A plug shaped device, such as appellee uses, may have a disk shaped face or “surface”; and there is nothing in the proceedings in the patent office that limit this definition; for though in his letter to the patent office appellant describes his disk as a “plain, thin disk,” it' evidently was not that, that differentiated it in the opinion of the patent office from the prior art, but the new function set forth, viz.: that “its edge is the same all around, and it fits quite closely in the water passage, and depends on a very slight leakage all around, to relieve the hammering.”

The truth is, that the gist of appellant’s patent is a discovery—the discovery that there will be no hammering in water valves if, instead of a sudden closing of the water column under pressure, the pressure is relieved by means of a continuation, for a brief interval, of a thin sheet or film around a primary valve. True, prior inventors had some inkling of this discovery, groping their way toward it with primary disks that were perforated, or were open at the edges—devices, however, that failed of their object. Glauber was the first to complete the discovery—to see that not only must the volume of water under pressure not be suddenly shut off, but that the gradual shutting off must be by means of a film or sheet that would permit the periphery of the column, for the interval needed, a continued flow.

Why this manner of relief prevents hammering—whether it is be*114cause the integrity of the column under pressure is not broken up, as perhaps it would be in the case of perforations or notches at the edges —is not a thing on which we need to speculate. What this record makes certain is the fact that it does for the first time prevent hammering; and that man is entitled to a patent who, being the first to hit upon a way of bringing about the fact, embodies it in mechanical form, ready to be presented to the world; and this we think Glauber has done, his claim being broad enough to cover other means that are mere mechanical equivalents of the means that he has set forth.

We have considered appellee’s contention of “prior use” as also the contention that the patent is too indefinite, but do not regard them as presenting any obstacle to the conclusion to which we have come.

The decree of the Circuit Court is reversed with instructions to enter a decree sustaining the validity of claim 1 of the patent, and finding the appellee’s device an infringement thereof, and for an injunction and other relief accordingly.