delivered the opinion of the Court:

The question presented by this appeal calls for the determination of the title, as prior inventor, to certain improvements in friction-springs summed up in the following issue:

“1. A device of the character described comprising a series of expansible resilient rings having inclined frictional surfaces and a compressible resilient ring interposed between adjacent expansible rings and having complemental inclined frictional surfaces.

“2. A device of the character described comprising a series of open spring rings having inclined frictional surfaces and a. series of members having inclined frictional surfaces interposed between said rings and engaging the inclined surfaces of the adjacent rings, whereby when said series of rings are subjected to-compression they are placed under tension through engagement of the inclined surfaces thereof with the inclined surfaces of the interposed members.”

While, fortunately, there is no dispute as to the facts, the-conclusion to be drawn from them does not seem free from doubt as evidenced by the conflicting decisions of the various-tribunals of the Patent Office. The Examiners of Interferences- and the Acting Commissioner found for ITien, while the Exam-in ers-in-Chief united in awarding priority to Gallagher.

It is established beyond reasonable doubt that Gallagher conceived and disclosed the invention about December 1, 1901, and that the device known as “Gallagher’s Exhibit Eriction Spring”' was made in December, 1901, and very shortly thereafter subjected to certain tests.

It is equally well established that Hien’s conception and. disclosure were made on June 28, 1902. It also appears that,, subsequent to the date of his constructive reduction to practice, by filing his application for patent on July 19, 1902, and prior to Gallagher’s constructive reduction to practice by the filing of his application for patent on November 22, 1902, Hien had made an actual reduction to practice by constructing a full-size friction-spring which was tested and shown to Gallagher in the *80latter part of October, 1902, and at the same time to George. A. Host, president of the Standard Coupler Company.

From the foregoing statement it appears that Gallagher was the first to conceive and disclose to others the invention, and that if the device of December, 1901, is entitled to be held a reduction to practice he is entitled to an award of priority. If, however, such device is not to be so considered, he must be shown to have been exercising diligence in adapting and perfecting his invention when Hien entered the field and until his application for patent was filed in November, 1902.

The record discloses an utter lack of diligence on the part of Gallagher. From December, 1901, or January, 1902, his only efforts, until after the Hien device was shown to him, consisted in more or less desultory talk about his invention, indecisive efforts to get the Standard Coupler Company, through Mr. Post, its president, to take up the invention, and, about the latter part of September, to start, in a leisurely manner, to make drawings of the device and modifications thereof. The invention is a simple one, and no good reason is shown why he did not earlier file an application for patent. It would have cost but little to have reduced the invention to actual practice beyond any shadow of doubt, and to have made proper tests. It is attempted to be shown that Gallagher had not the means to do more than he did do, and that he was a very busy man, engaged not only in his regular employment, but was developing or assisting in the development of another line of invention. The proofs show that his time was well employed, and that he was not in a position to enter upon the manufacture of the invention. It appears, however, that from January 1, 1902, he was in receipt of a salary of $175 a month, that he was a draftsman, and further, that, though not bound by any contract to the Standard Coupler Company not to exploit the invention through others, he made no efforts to do so, and that as early as June, 1902, Mr. Dennis, secretary and treasurer of the Standard Coupler Company, expressed a willingness to become personally interested if that company did not care to take up the matter. Gallagher preferred to wait upon the pleasure of the Coupler Company, al*81though not a novice in matters relating to patents, and that was undoubtedly the reason for his inaction. The record, so far from showing that he was excusable in his lack of diligence, shows conclusively that he could have filed an application for patent at almost any time between December, 1901, and November 22, 1902. He was neither without money nor without friends to aid him in perfecting his invention and securing his rights to its exclusive ownership. He merely failed to appreciate the necessity for prompt action, and it was only the discovery that there was another Hichmond in the field that spurred him to action. Gallagher’s conduct is in striking contrast with that of Hien. The latter moved with most commendable promptitude, and in view of the disclosures of the record it is apparent that a patent would have probably been issued to Hien before Gallagher was roused into activity, for the Hien application was ready for allowance as early as August 18, 1902, subject to a prospective interference. It is true that in the latter part of September, 1902, the Standard Coupler Company finally decided to take up Gallagher’s invention, but even after that he made haste slowly. Our conclusion on this point is that Gallagher was not diligent, and fails to excuse his lack of diligence by any situation of affairs that the well-settled rules hold to constitute sufficient excuse.

Gallagher therefore cannot prevail unless his exhibit “Friction-Spring,” taken in connection with such tests as were made, constitutes a reduction to practice.

In considering this question we apprehend that the same act or set of acts may or may not constitute a reduction to practice, modified, as they may be, by the special circumstances of the particular case.

We do not think that the size of a device is necessarily controlling in determining the question of a reduction to practice. In the Corn-planter Patent, 23 Wall. 181, 23 L. ed. 161, a half-sized device was held to be the equivalent of a reduction to practice, but that device was actually used in planting corn, and completely demonstrated the utility and practicability of the device.

*82Nor do we think that mechanical perfection, or that, as has been well stated, there are “possibilities of greater excellence in shape, location, arrangement, material, or adjustment,” essential for a reduction to practice. Tested by any such requirements, nearly every pioneer invention, as put upon the market, would have failed to support the patent granted for it.

Nevertheless, it is essential that a device to constitute a redtiction to practice must show that “the work of the inventor must bo finished, physically as well as mentally. Nothing must be left for the inventive genius of the public.” 1 Robinson, Patents, p. 183.

Nor is it always essential that actual tests of the invention be made in order to complete the inventive act. Mason v. Hepburn, 13 App. D. C. 86. The device relied upon as a reduction to practice must, however, if it has not been worked, clearly be capable of work, and not have been a mere experiment. “Experiments in the direction of the desired result are not such reduction, no matter how nearly they approximate that end.” 1 Robinson, Patents, p. 183.

In the case at bar it appears that Gallagher during December, 1901, caused to be made a small-sized spring composed of two inside and two outside split friction-rings. The exterior ring3 were something over three inches in diameter and about an inch wide, and the inner rings were somewhat smaller. lie says they were made to make clear to Mr. Post and to others something of the nature of the invention, to establish a record, and to prove the utility of the device. The device was sufficient to show something of the nature of the invention, to establish at least a conception, but of itself, and without thorough tests, was not sufficient to prove either the utility or practicability of the invention.

The invention undoubtedly belongs to that class which requires either actual use or thorough tests to demonstrate its practicability, and therefore there can be no actual reduction to practice until one or the other thing takes place and is proven. Both parties in effect admit this necessity, for they both subjected their devices to certain testó. It is unnecessary to *83determine whether Hien’s tests were sufficient, for his constructive reduction to practice preceded any claimed actual reduction. However, it may be said that his tests went far beyond any made by Gallagher. As to the necessity for thorough tests in this case, our views are confirmed by the testimony of Mr. Dennis, a witness called by Gallagher. He characterizes the invention as “a radical departure from the previous methods.” Gallagher thus describes the tests made by him. He says the device was first put in a vise, and subjected to pressure. What that pressure was he does not state, nor does he state any facts which enable us to determine whether he was justified in his conclusion that the result of the test was satisfactory. No one seems to have been present at this test, and, in our opinion, it proves nothing. Thereafter he took the device to Bridgeport, where some slight changes were made, and the springs tempered. The device was then put in a vise, and then on the anvil of a strong and powerful steam-hammer, the rings being held in place by a pair of blacksmith’s tongs held by Mr. Wilder. After being, as he says, repeatedly struck with the hammer, they were broken by a hard blow. The pieces were put in a package, taken to New York, and laid away for future use. They do not seem to have been used for any purpose after that until they appear in these proceedings. Mr. Wilder, who assisted Gallagher in the test at Bridgeport, says that, not having a power-press, the device was put in the vise and squeezed, and found to work as a spring, but the power of the vise was not great enough to close the spring. He goes on to say: “We put it under our steam-hammer and hit it a light blow which showed its action, but in giving it a little too hard a blow it broke.” He expresses no opinion as to wdiat the test demonstrated, or proved, if anything, nor does he give any data from which we can draw the conclusion that the test proved anything of value. The tests, in our opinion were inconclusive and insufficient upon which to predicate a finding that they proved the practicability of the invention. It will be noted, as stated by the Acting Commissioner “that no measurements were taken to show the tensile strength or the pressure to which the springs were subjected.” We are confirmed in our *84belief that the device, tested as it was, still remained in the domain of experiments, by the testimony of Mr. Dennis, one of the officers of the Standard Coupler Company. He evidently did not consider that the experimental stage had been passed. Speaking of his faith in the invention, he says that he thought it “worth experimenting with,” that “there was enough in the idea to warrant experiments,” and as late as June, 1902, he says he stated to Mr. Sessions, “I thought there was enough in the idea to warrant some experiments.”

We find that Gallagher was the first to conceive, disclose, and make an experimental device, which was tested experimentally, but that he was the last to reduce the invention to practice, and he failed to exercise ordinary diligence in connecting his earlier conception with his later reduction. He has failed to overcome the presumption that Hien is the first inventor, arising out of his being the earliest to apply for a patent.

We think the Acting Commissioner of Patents was right in his judgment, and that it should be affirmed.

The clerk of the court will certify this opinion, and the proceedings in this court in the premises, to the Commissioner of Patents according to law. Affirmed.