and public.” See also
Merrill v.
Yeomans, 94 U. S. 568, 573;
Water Meter Co. v.
Desper, 101 U. S. 332, 337.
Miller v. Brass Co., 104 U. S. 350. These authorities dispose of the contention of the plaintiff’s counsel that their patent covers one of the separate elements which enters into the combination, namely, a slotted wooden beam, because, as they contend, that element is new, and is the original invention of the patentees.
The patent being for a combination, there can be no infringement unless the combination is infringed. In Prouty v. Ruggies, 16 Pet. 336, 341, it ivas said: “This combination, composed of all the parts mentioned in the specification, and arranged with reference to each other, and to other parts of the, plough in the manner therein described, is stated to be the improvement and is the thing patented. The use of any two of these parts only, or of two combined with a third which is substantially different, in form or in the manner of its arrangement and connection with the others, is, therefore, not the thing patented. It is not the same combination if it substantially differs from it in any of its parts. The jogging of the standard into the beam, and its extension backward from the bolt, are both treated by the plaintiffs as essential parts of their combination for the purpose of brace and draft. Consequently, the use of either alone, by the defendants, wrould not be the same improvement nor infringe the patent of the plaintiffs.” To the same effect see also Stimpson v. Baltimore & Susquehanna Railroad Co., 10 How. 329; Eames v. Godfrey, 1 Wall. 78; Seymour v. Osborne, 11 Wall. 516; Dunbar v. Myers, 94 U. S. 187; Fuller v. Yentzer, 94 U. S. 288.
But this rule is subject to the qualification, that a combination may be infringed when some of the elements are employed and for the others mechanical equivalents are used which were known to be such at the time when the patent was granted. Seymour v. Osborne, ubi supra; Gould v. Rees, 15 Wall. 187; Imhaeuser v. Buerk, 101 U. S. 647.
In the light of these principles, we are to inquire whether the defendants use the combination described in the patent of the plaintiffs. The contention of the defendants is that the brace-bar, which is one of the elements of the combination