delivered the opinion of the Court:

This is an appeal by Osias O. Kruh, from a decision of the Commissioner of Patents in an interference proceeding.

The invention in issue, in the words of the primary examiner, “belongs to that class of mercury rectifiers which utilize an inductance to maintain continuity of flow over the zero point of the supply, in order to prevent extinguishment of the apparatus. According to this invention the inductance is placed in the leads to the positive electrodes.” In each of the applications the device is shown to contain two positive electrodes, or anodes, in the leads of each of which are placed the inductances and one negative electrode, or cathode, although in appellant’s device there is also added a starting positive electrode in the lead to which there is no inductance.

The issue is embraced in five counts, which are as follows:

“1. In a system of electrical distribution, a source of single-phase alternating current, a direct current work circuit supplied therefrom, an interposed vapor converter having suitable negative electrode and a plurality of positive electrodes, and an inductance introduced into each of the leads of the positive electrodes to maintain the converter in operative condition.

“2. In a system of electrical distribution wherein a vapor converter is employed in connection with a source of single-phase alternating current, and a direct current work circuit is supplied through the vapor converter, a negative electrode in the converter and a plurality of positive electrodes, and energy-storing devices in the leads to the positive electrodes whereby the converter is maintained in operative condition.

“3. The combination with a source of single-phase current and a work circuit supplied thereby, of a vapor converter un*339able of itself to maintain, operation over tbe zero point of tbe supply, unless means are provided for carrying it over the natural zero point, a plurality of positive electrodes and a negative electrode in tbe said converter and energy storing devices in tbe leads to tbe positive electrodes for preventing tbe ex-tinguishment of tbe converter at tbe zero point.

“4. In a system of electrical distribution, a source of alternating current, a direct current work circuit supplied therefrom, an interposed vapor converter having a suitable negative electrode and a plurality of positive electrodes and an inductance introduced into each of tbe leads to a plurality of tbe positive electrodes for tbe purpose of maintaining tbe converter in operative condition.

“5. In a system of electrical distribution, a source of alternating current, a direct current work circuit supplied therefrom, an interposed vapor converter and a positive electrode therefor, and an energy — storing device in tbe lead thereto for tbe purpose of maintaining tbe converter in operative condition.”

Appellant’s application was filed February 20, 1904, and appellee’s July 6, 1904. Both parties rely for evidence of conception and disclosure and for a constructive reduction to practice upon prior applications filed by them respectively. That depended upon by appellant, filed December 12, 1903, shows in figure 5 a device consisting of two primary and two secondary positive electrodes. Tbe two primary electrodes derive their current direct from tbe source of current supply. No inductances are placed in their leads. Tbe apparatus is kept alive by means of tbe secondary electrodes, which are supplied with a part of the current which has passed from tbe primary positive electrodes through tbe appartus and the negative electrode to tbe negative lead. In this lead is placed an inductance. Speaking of tbe operation of this device, appellant, in bis application, says: “I have found, however, that one of. tbe anodes, and that one which carries tbe small current for tbe purpose of maintaining tbe other or main anode in operation, may be supplied with current derived solely by *340an inductive discharge from the energy-storing device traversed by current passing through the main anode.”

Whether or not the flow of current to a positive electrode through an inductance placed in the negative lead causes a different operation and result from that obtained through an inductance placed in the positive lead alone, we regard as an exceedingly close question. The tribunals below were unanimous in holding that appellant’s earlier application failed to disclose the invention here in issue. It is true that they seem to base their opinion upon figures 1 and 2; but we must assume, however, that, having the whole application before them, figure 5 was also given due consideration, if that figure was brought to their attention. In a case like the present, involving an invention so highly technical, where we are unable to have the benefit of the testimony of witnesses skilled in the art, we are unwilling to overturn the unanimous decisions of the experts of the Patent Office, who are more competent to pass upon questions of his nature, unless it is clearly apparent that error has been committed.

We come now to the consideration of appellee’s earlier application, filed December 24, 1903. All of the tribunals below united in holding that this application disclosed the subject-matter of counts 2 to 5, inclusive. There seems to be no doubt of the correctness of this conclusion. Appellee there shows a device containing two primary and two secondary electrodes, the inductances, however, being in only the secondary leads. The issue merely calls for a “plurality of positive electrodes,” and is not limited to the number shown in the applications involved in this interference. Neither do counts 2 to 5, inclusive, call for a separate inductance for each positive lead, but merely for an “inductance introduced into each of the leads to a plurality of the positive electrodes.” This, appellee undoubtedly discloses in his 1903 application.

Whether the elements of count 1 can also be read on to this application presents a question of greater difficulty. The Primary Examiner and the Board of Examiners in Chief decided this question in favor of appellant, but this decision *341was reversed on appeal to the Commissioner. Count 1 calls for “an inductance introduced into each of the leads of the positive electrodes.” As we have seen, appellee only placed inductances in the leads to the secondary, and not to the primary, positive electrodes. We must agree with the primary examiner and the Board of Examiners in Chief that count 1 is specific, and that a fair construction requires that there shall be an inductance in each of the positive leads, a mere plurality of inductances not being sufficient. Appellee, however, contends that appellant, in his application here in interference, shows one positive electrode containing no inductance in its lead, and that if this count is so construed as to read upon that device, as it must be, then it can be read equally well upon the disclosure in his 1903 application. This electrode, however, is not used for the purpose of operating the apparatus, but is merely for tho purpose of starting it, being switched off when the other positive electrodes become active.

The two lower tribunals of the Batent Office also held that, although appellee produced evidence of conception of the subject-matter of count 1 prior to appellant, yet being the last to reduce to practice, and lacking in diligence, he was not entitled to priority. With this conclusion also, we must agree.

The decision of the Commissioner of Patents is affirmed as to counts 2, 3, 4, and 5, and reversed as to count 1. The clerk is directed to certify these proceedings as required by law.

Affirmed in part and reversed in part.