delivered tbe opinion of tbe Court:

This is an appeal by Arthur C. Eastwood from tbe decision of tbe Commissioner of Patents in an interference proceeding awarding priority of invention to Lewis D. Kowell, appellee, *282the senior party. The invention in issue relates to a magnet for Handling iron and steel by means of magnetic attraction. Tbe issue is sufficiently defined by tbe count of tbe interference, as follows: “A lifting magnet Having a central pole, an outer-pole concentric with and surrounding said central pole and removable pole shoes on tbe bottom faces of both of said poles, tbe pole shoe on tbe outer pole being deeper tban tbe pole shoe on tbe central [role, sucb that its under face is lower tban tbe under face of tbe pole shoe on tbe central pole.”

Tbe principal question raised in this case is tbe construction to be placed upon tbe following language in tbe count, which originated as a claim in appellant’s application: “The pole shoe on tbe outer pole being deeper tban tbe pole shoe on tbe central pole, such that its under face is lower tban tbe under face of the pole shoe on tbe central pole.” Appellant contends that tbe last clause so defines tbe word “deeper” as to make it synonymous with tbe word “lower,” thus making this portion of count call merely for an outer pole shoe with its under face lower tban the central pole shoe. All of tbe tribunals of the Patent Office, however, held that this word should be construed as equivalent to “thicker.” It seems hardly probable that appellant would have used a word in a sense which apparently be knew to be ambiguous, and then have followed it with a clause of twenty words to explain that lower was meant, when tbe whole claim could have been left free from doubt by the use of tbe word “lower” in place of “deeper” in tbe first instance, thus rendering a defining clause unnecessary. If given tbe construction adopted by tbe tribunals of tbe Patent Office, effect may be given to every word in tbe claim, since, in tbe state of tbe art, tbe use of an outer pole shoe of great thickness tban tbe central pole shoe would insure tbe former being-lower tban tbe latter. That this was tbe intention of appellant is borne out by tbe following language in bis specification: “It is noted that I have shown tbe pole shoe e’ of sucb dimensions that its active face will be lower than tbe active face of tbe central pole shoe b.’ * * * Tbe depth of tbe pole ring c’ is also of advantage mechanically, since tbe ring will *283be very strong in a vertical direction, and therefore capable of withstanding the heavy blows which it receives when the completed magnet, which may readily weigh 5,000 pounds, is dropped upon piles of iron and steel.” In the first sentence quoted, the language is somewhat similar to that of the claim. The word “dimensions” there used could only be applied to thickness. In the second sentence, the word “depth” is used as synonymous with thickness, since otherwise there would be no difference in the vertical strength. While it is true that there is nothing in this record to show that such a limitation as that imposed by the tribunals below is necessary to sustain the validity of the claim, yet this structure is shown in appellant’s Patent Office drawing, and, if he thought it advisable to limit himself thereto, it is not within the province of this court to reconstruct his claim.

A test claimed by appellant to constitute a reduction to practice was made at South Chicago, Illinois, which, if sustained, would give appellant priority. It is conclusively shown, however, that the magnet tested had a central pole shoe 1/16 of an inch thicker than the outer shoe, and, though it seems to have worked perfectly, it cannot be held to constitute a reduction to practice, since the magnet was not constructed strictly in conformity with the claim in issue.

The next question presented is whether or not a device known as the “Latrobe magnet” constituted a reduction to practice. This magnet was one half the size of the one tested at South Chicago. The tribunals of the Patent Office held that, although the drawings by which this magnet was made called for an outer pole shoe 1/16 of an inch thicker than the central pole shoe, the evidence was insufficient to establish the fact that the completed structure conformed accurately to the dimensions called for in the drawings. We have examined the record carefully, and agree with their conclusion on this point. Appellant is here not alone with the burden attaching to the junior party, hut with the additional burden imposed by the .unanimous decisions of the Patent Office against him. An inaccuracy in following the drawings of 1/16 of an inch in the *284relative thicknesses of the pole shoe, in a device about 2 feet wide and 6 inches high, would be sufficient to prevent this device from constituting a reduction to practice; hence the necessity of some proof to the effect that the completed magnet conformed strictly to the requirements of the drawings. The question, it must be conceded, is an exceedingly close one. We are not satisfied, however, that error has been committed.

The decision of the Commissioner of Patents is affirmed, and the clerk is directed to certify these proceedings as by law required. Affirmed.