delivered the opinion of the Court:

This is an appeal from a decision of the Commissioner of .Patents in an interference proceeding. The issue of the interference is as follows:

“1. In a block-signaling system, the combination of a step-by-step controller at each end of the block, one of which is operated a step forward and backward respectively in response to each car entering and leaving the block in a given direction, a danger signal set in response to the first forward movement of said controller and cleared by its last return movement, a signal set at the entering end of the block in response to the setting of said danger signal, danger and caution signals similarly arranged with respect to the other controller and governed thereby in response to cars entering and leaving the block in the opposite direction, two line wires only extending along the block for controlling and operating said signals, and means including a switch for causing an indication of the movement of the operating controller to be given each following car entering the block after the signals are set.

“2. In a signaling system, the combination of step by step controllers, one at each end of a block, one of said controllers operated a step forward and backward respectively in response to cars entering and leaving the block in one direction, a danger signal set when said controller assumes its first forward movement and cleared when the controller is restored, the other step-by-step controller similarly operated in response to cars entering and leaving the block in the other direction, a danger signal similarly set by said controller, a single line wire for controlling the setting of either of said signals, and a signal set in response to the setting of one of said danger signals for indicating to the first car of a series the setting of said danger signal.

“3. In a block-signaling system, the combination of a step-by-step controller at each end of the block, one of which is op*92erateH a step forward and backward respectively in response to eacb car entering and leaving tbe block in a given direction, a danger signal at one end of the block set in response to tbe first forward movement of said controller and cleared in response to its last backward movement, a signal at tbe entering end set in response to tbe setting of tbe danger signal, means for causing an indication to be given eacb subsequent car to show tbe forward movement of its signal controller, signals and circuits similarly arranged and controlled by tbe other step-by-step controller in response to cars entering and leaving tbe block in tbe opposite direction, and a common line circuit for controlling tbe setting of tbe danger signals.

“4. In a block-signaling system, a signal circuit extending along tbe block, signal-setting means at one end controlled through said circuit by tbe first car of a possible series entering tbe block for setting a signal at that end, a signal at tbe other end controlled through said circuit by tbe setting of tbe first signal, and a switch operated in advancing tbe controller and controlled by tbe entry of eacb succeeding car of tbe series for causing an indication of the controller movement to be given eacb of said cars without affecting said first signal.”

It appears from tbe record that appellant, Lawrence A. Hawkins, disclosed tbe invention about May 25, 1907, and filed bis application on November 29, 1907. Appellee, Samuel M. Ward, Jr., disclosed it about June 15th, and filed bis application on July 22, 1907. Neither party reduced tbe invention to practice. It is conceded that appellant was tbe first to conceive and disclose tbe invention.

Tbe sole question, therefore, is whether appellant exercised due diligence toward reducing tbe invention to practice. It appears from tbe record that appellant is an engineer and patent attorney in tbe employ of tbe General Electric Company, tbe assignee of bis application. It may, therefore, be presumed that be is skilled in tbe art to which this invention belongs, as well as tbe practice in procuring patents. It appears that a large part of tbe time between the date of disclosure and tbe date of filing bis application in tbe Patent Office was con*93sumed in making an investigation to determine whether or not this invention would be an infringement upon any prior existing patent. It is contended that such investigation constitutes a proper excuse for delay. With this contention we cannot agree. We see no distinction between delay for the purpose of ascertaining whether or not there is infringement, and delay for the mere business purpose of exploiting an invention before making application for patent. In neither case does this furnish a valid excuse.

It does not affect the patentability of a novel device that it may, perchance, have to pay tribute to some dominating patent. This is merely a question between the pioneer inventor and the one who conceives the improvement. The latter is not entitled to withhold his improvement from the public until he may manufacture free from the claims of earlier inventors, and then secure a monopoly for the full period allowed by the patent laws. Neither is he entitled to delay the completion of his invention pending an examination into the prior art for the purpose of discovering dominating patents, in order to determine whether it should seem advisable to him to modify his invention so as not to come within the scope of such earlier patents. This is what appellant did here, for in his testimony he says, I “felt reasonably sure that Mr. Fairfax was not going to find any patents which would force us seriously to modify the system.” It can hardly be contended that actions which might result in the modification of the invention in issue constitute diligence in reducing this system to practice.

The decision of the Commissioner oí latente is and the clerk is directed to certify these proceedings as by law required. Affirmed.