end to the desired extent, and hence, subsequent to this process patent, it became necessary to have some rolls invented which would effect the end.
Now, it is an elemental proposition as to patents that they shall be so clear that by ordinary means they can be worked out by a person skilled in the art. It is clear that this patent could not be operated by any method until some person invented rolls, which, while they should not be corrugated, because that would be as bad as the mill-stones in triturating, but should be smooth, and yet have sufficient grip and be of sufficient hardness; and that was not ail, they must have the same diameters and work with equal speed, instead of differential speed. Neither of which was suggested in the patent.
To summarize, the claim of the patent is specific: "The herein described process of manufacturing middlings flour by passing the middlings, after their discharge from a purifier, through or between rolls, and subsequently bolting and grinding the same for the purposes set forth." Those purposes, as the specification states, are mainly for flattening the germ. That object was effected by the interposition of rolls at that particular stage of the process. Rolls at other stages of the milling process had been previously used, and even rolls by Mowbray at that particular stage ; hence, if the patent is to be construed by its terms as covering the use of rolls at any stage of the milling process, it had been long anticipated prior thereto. If it is to be restricted to the use of rolls at the particular stage mentioned, then, so far as this case is concerned, the plaintiff is estopped, because he himself, as heretofore decided, placed the only rolls used at that stage in the defendant's mill.
On the other hand, irrespective of the question of estoppel, if the patent is for a process to be effected without any known means of accomplishing the result, but requiring inventive faculty, whereby rolls to accomplish the purposes, and their modes of operation, were to be determined by new inventions or discoveries, then the patent does not furnish to any one, as then skilled in the art, means whereby the bene-
