ter for the courts to decide. It is true there was no assertion of right against the Berdan device in consequence of the difference between it and the device used by the Government as, it may be said, there was in the case at bar by the letter of Admiral Ramsey of September 3, 1891. But the position taken in that letter was, as we have seen, abandoned, and it was declared that so far as the De Bange patent was valid its claim for royalties was, in the opinion of the Bureau of Ordnance, a proper one and would be sustained by the courts. This was in 1894. Prior to that time and afterwards the Government continued to use the device. We think the Court of Claims had jurisdiction.

The Government contends that it has not infringed the De Bange patent. Infringement is a question of fact, and as an aid to its solution courts are furnished usually with an expert comparison of the contending devices, their identity or difference of construction and modes of operation. This record is destitute of such testimony. The Government contends for the very narrow construction of the patent based on its claims and the prior art. The only proof of the prior art, however, is a reference to thirteen or fourteen patents by number and patentee, some of which are English, some French and some Ameri

can.

The only explanation of them is in the argument of counsel and an exhibition of the patents. It is very doubtful if we may take notice of even the American patents; more doubtful if we may of the foreign ones. We, however, have considered counsel's explanation of them. They reveal nothing material to be considered that the findings of the Court of Claims do not show of the prior art and the progress from its failure to the success of the De Bange invention, a success, it may be conceded, that availed itself of all that the prior art demonstrated, but went beyond it to the fulfillment that it had not achieved.

The necessity of a gas check to the success of breech

loading guns all could see, and what a device, to be successful, must do; but the world struggled a long time with the problem, and that problem was to find something which would stand the intense heat generated and the great force caused by the explosion of the powder in a high power gun and the backward escape of the resultant gas under the enormous pressure exerted, and this not in one service of the gun, but in many services. The experiments are detailed in the findings. Metallic cups were tried and paper cups. As early as 1858 India rubber was suggested. Its elasticity, it was thought, would afford all that was necessary for a complete automatic obturation, the gas by its expansion "to seal its own escape."

Rubber had some success when constructed in rings of varying degrees of suppleness and hardness, and seemed to have settled the problem. But defects subsequently developed and experiments continued for something better and which would fulfill all the conditions. Then soap obturators were tried, and finally Colonel De Bange's invention of tallow and asbestos. If our purpose was speculative, not practical, we might pause to wonder how such substances could produce such results under the conditions to which they are subjected, and by wondering we express in a way the quality of the invention. We are told by the findings of the Court of Claims that a gas check "is subject to a pressure of from 30,000 to 40,000 pounds per square inch, to very high temperatures, to the effects of corrosive gases, and the effects of rapid and violent shocks."

We need not, however, dwell longer on the excellence of the invention. The Government has testified to its excellence by using it in the guns intended for the national defense.

But it is contended that the claim of the patent is for a specific combination of elements and that that combination of elements is not used by the Government.

Opinion of the Court.

224 U.S.

This contention is based upon what is considered to be the proper construction of claim 1 of the patent, a strict construction being urged of it-indeed, as we understand the argument, the claim must be confined to the specific forms of its elements, giving the widest latitude to imitation.

The patent answers the contention. Describing his invention, De Bange calls it "certain new and useful improvements in breech-loading guns." Specifying the improvements, he says that they "apply to breech-loading guns which employ a screw-plug having its threads interrupted." Further specifying, he adds: "I have devised a system of packing placed in advance of the plug, and which is expanded by the force of the explosion of the powder to make a tight joint to prevent the leakage of gas." He declares the drawings form a part of the specification and represent what he considers the best means of carrying out the invention. It is only necessary to give Figures 1, 2, 6 and 7.

They are described in the patent as follows: "Figure 1 is a central longitudinal section. The strong lines show the parts ready for firing. The dotted lines show the transverse lever in a position for conveniently operating to turn the screw-plug. Fig. 2 is a rear view showing the parts locked. Fig. 3 is a corresponding view showing

the parts unlocked. Figs. 6 and 7 represent the packing-ring detached. Fig. 6 is a face view, and Fig. 7 a section in the plane of the axis." The specification then proceeds as follows:

"A liberal hole in the line of the axis of the screw-plug B carries a stout sliding pin, N, at the extreme front of which is a stout head, N'. The portion of the body adjacent to the head N' is slightly enlarged. The head N' is adapted to receive the force of the powder at the discharge. At the moment of the discharge this head moves backward, compressing a relatively soft and expansible packing-ring, M, behind it. Certain portions of this ring will be distinguished, when necessary, by additional marks, as M' M2. The body M' of this packing is of asbestos saturated with tallow, and affords a sufficiently yielding mass with the required capacity for enduring heat and for withstanding the very strong compressive force to which it is subjected by the discharge. It is inclosed between two thin shells, M2 M2, of copper, one fitting the body M' on the inner and the other on the outer side, and nearly incasing the entire packing. Both the body M' and the copper M2 are then inclosed between two strong shells of brass, M3 M3. The entire packing thus made is adapted to maintain its form, but to allow a small amount of radial expansion sufficient to pack the joint tightly against the escape of gas. This expansion is due to two causes the tapering form of the front end of the pin N, which acts on the interior of the packing, and the powerful compression received from the head N'. The expansion from one or both causes is sufficient to press the exterior of the copper M2 tightly against the interior of the gun, thus effectually preventing any leakage of gas."

Claim 1 is the important one and is as follows:

"1. The partially-threaded plug B, headed pin N N', extending through said plug, and the yielding packing M,

Opinion of the Court.

224 U.S.

arranged between the head N' and the inner end of the plug, in combination with each other and with the gun A, arranged as shown, to allow the pin to be driven rearward and compress the packing, as herein specified."

It will be observed, therefore, that De Bange declared that what he devised was a "system of packing" which by the force of the explosion of the powder is expanded to make a tight joint to prevent the leakage of gas. The mechanical parts are but aids to this result, securing in place the packing and enabling its qualities to operate, enabling it to maintain its form but to allow radial expansion sufficient "to pack the joint tightly against the escape of gas." This expansion has also the effect of pressing "the copper (M2)" against the interior of the gun and coöperates to prevent the leakage of gas.

That this packing constitutes the very essence of the invention is declared in all of the literature on the subject and recognized in all of the Government publications. The Government now contends for a limitation of it, and insists that it consists of "a yielding packing M," exactly as described, although the description is declared by De Bange to represent "the best means of carrying out his invention," and he declares also that "modifications could be used in the forms and proportions."

We cannot therefore assent to the contention of the Government, and in rejecting it we do not render "the claim elastic and indefinite where it should be certain." We preserve that which was declared to be and which has always been recognized to be the invention, and by those competent to declare, whose duty it was to comprehend and estimate, not only the result achieved but by what achieved.

In the description furnished by De Bange to Commander Chadwick a covering of cloth is described. The description in the Ordnance Notes of April 20, 1883, mentions "plates of tin, strengthened at the edges by thin brass