The questions to be decided, therefore, are whether the English patent (which was given in evidence) was for the same invention as the American patent; and, if so, whether the latter is limited to expire at the end of 17 years from the sealing of the former. We think that both of these questions must be answered in the affirmative.
As to the first question, we have carefully compared the two patents, the English and American, and can see no essential difference between them. They describe the same furnace in all essential particulars. The English specification is more detailed, and the drawings are more minute and full; but the same thing is described in both. There is only one claim in the English patent, it is true. But that claim, under the English patent system, entitled the patentees to their entire invention, and is at least as broad and comprehensive as all four claims in the American patent. It is in these terms: 'Having now described the nature of our invention, and the best modes we are acquainted with of performing the same, we wish it to be understood that we do not confine ourselves to the precise details shown on the accompanying drawings; but we claim as our invention the various arrangements of regenerative furnaces worked by the gases resulting from an imperfect combustion of solid fuel in separate places, as hereinbefore set forth.'
It is contended by the counsel of the complainants that the American patent contains improvements which are not exhibited in the English patent. But, if this were so, it would not help the complainants. The principal invention is in both, and, if the American patent contains additional improvements, this fact cannot save the patent from the operation of the law which is invoked, if it is subject to that law at all. A patent cannot be exempted from the operation of the law by adding some new improvements to the invention; and cannot be construed as running partly from one date, and partly from another. This would be productive of endless confusion.