such invention, a jury, or a court trying the facts, is warranted in finding that he has so far recognized the obligations of service flowing from his employment and the benefits resulting from his use of the property, and the assistance of the co-employés, of his employer, as to have given to such employer an irrevocable license to use such invention".

Solomons v. United States (1890) 137 U.S. 342 (346). There the facts upon which the court held that the license should be implied were as follows: The patentee was in the employ of the government when he invented an improved stamp. His experiments were wholly at the expense of the government. He was consulted as to the proper stamp to be used, and it was adopted on his recommendation. He notified the government that he would make no charge if it adopted his recommendation and used his 'stamp; and for the express reason that he was in the government employ, and had used the government machinery in perfecting his stamp. He never pretended, personally, to make any charge against the government. The court considered that the mere fact that the servant's wages were not increased in this case, while in the case next cited such an increase was granted, was not sufficient to create a distinction between the two cases.

An earlier decision which was relied in in the Solomons Case, as a precedent precisely in point, was McClurg v. Kingsland (1843) 1 How. 202. There it was held that a license to the employer to use the invention might justifiably be presumed from evidence to the effect, that the patentee, while working for wages in a factory, had, after making several unsuccessful experiments at the expense of his employer invented the improvements patented; that his wages had been increased in account of the useful result; that he remained for some months afterwards in the same employment. continuing during that period to manufacture the improved article for his employers; that he finally applied for and obtained a patent; that, while continued in the employment he proposed that his employers should take out a patent, and purchase his right, which they declined; that he made no demand on them for any compensation for using his improvement, and gave them no notice not to use it, till, on some misunderstanding on another subject, he gave them such notice, about the time of his leaving their establishment, and after making the agreement with the plaintiffs for an assignment to them of his right.

For other cases which illustrate the doctrine stated in the text, see Lane & B. Co. v. Locke, (1893) 150 U.S. 193, 37 L. ed. 1049, (engineer and draftsman, at a fixed salary, in the employ of the defendants, and using their tools and patterns, invented a stop valve, which the firm used with his knowledge in certain elevators constructed until its dissolution, and after that a corporation organized by the firm used it in the same way and with the like knowledge); Keyes v. Eureka Consol. Min. Co. (1893) 158 U. S. 150, 39 L. ed. 929, (employé of smelting company who had invented a new method of withdrawing molten metal from a furnace took out a patent for it, and permitted his employer to use it without charge so long as he remained in its employ, which was about ten years); Chabot v. American Button-Hole & O. Co. (1872) 9 Phila. 378, 6 Fish. Pat. Cas. 71, (presumption of license held to be strengthened by the terms of an express contract, which had been made before the employé applied for a patent, and which provided that a large number of machines should be manufactured by the use of the defendant's factory, machinery, tools and materials, the employé supplying, at a specified price, merely the labour ex

In a later case the same court carried the doctrine still further in the masters' favour by declaring that the presumption of a license will be entertained, irrespective of the consideration whether the property of the employer and the services of his other employer's were or were not used in the experiments necessary to develop the invention, or in the preparation of patterns

pended upon them, and his own services); Continental Windmill Co. v. Empire Windmill Co. (1871) 8 Blatch. 295, (suit for infringement held not to be maintainable by the assignee of the patent against a former employer of the patentee who had engaged him on a salary, with the understanding that he was to receive $500 for any patentable improvements he might make;) Magoun v. New England Glass Co. (1877), 3 Bann. & Ard. Pat. Cas. 114, Fed. Cas. 8,960 (articles constructed by or under the direction of the servant, and at their own expense placed by his employers in their factories with his knowledge and consent); Davis v. United States (1888) 23 Ct. of Cl. 329, (cost of experiments by foreman of a division of the Ordinance Department was paid by the United States: patents were taken out under the advice of the chief of the Ordnance Bureau: after they were issued the Navy Department paid employee a sum of money to reimburse him for the expense incurred in securing them, as a royalty for the right to their use); Barry v. Crane Bros. Mfg. Co. (1884) 22 Fed. 396; (complainant, by introducing into his employer's business certain improved tools which he had produced while working as a departmental foreman, was held to have licensed or consented to the use of those tools by the defendant company, not only for the time that he was in its employ, but so long as the tools shall last); Bensley v. North-Western Horse-Nail Co. (1886) 26 Fed. 250 (patented improvements developed and perfected at the sole expense of an employer, by employés who received extra pay on account of their known ability as inventors); American Tube-Works v. Bridgewater Iron Co. (1886) 26 Fed. 334 (inventor and patentee had supervised and directed the building of a machine for the defendant company, while he was in its employ); Withington-Cooley Mfg. Co. v. Kinney (1895) 68 Fed. 500, 15 C.C.A. 531, (right to continue constructing machines after pat terns which an inventor had been employed upon a salary to devise, held not to have been terminated by the destruction of the original patterns in a fire); Jencks v. Mills (1886) 27 Fed. 622 (employé, while experimenting upon his invention, of which he had several, took the time which belonged to the defendants, used their tools, workmen, and materials, and tested the inventions in the machinery which was run by them); Fuller etc. Co. v. Bartlett (1887) 68 Wis. 73, 31 N.W. 747 (superintendent of a manufacturing company, knowing its intention to perfect and put upon the market a new machine, voluntarily disclosed his conception of a device to be used in connection therewith, and, under the direction of the company and with its material and at its expense, voluntarily went to work to perfect such device and construct the machines and to aid in putting them upon the market.

The rule adopted in the above cases is held to be equally applicable in cases where a machine is constructed with the inventor's knowledge and consent, before his application for a patent, by a partnership of which he is a member. The machine may be used by his copartners after the dissolution of the partnership, although the agreement of dissolution provides that nothing therein contained shall operate as an assent to such use, or shall lessen or impair any rights which they may have to such use. Wade v. Metcalf (1889) 129 U.S. 202.

and working drawings, and the construction of the completed machines. The principle was stated to be "really an application or outgrowth of the law of estoppel in pais, by which a person looking on and assenting to that which he has power to prevent is held to be precluded ever afterwards from maintaining an action for damages” 5.

If the license which is thus implied from, the general terms of the employment and the acquiescence of the employee in the use of his invention by the employer relates to an improvement in a process, the employer is ordinarily deemed to be authorized to continue to the improvement, during the whole period covered

5 Gill v. United States (1896) 160 U.S. 426 (p. 430). The court said: "This case raises the question, which has been several times presented to this court, whether an employé paid by salary or wages, who devises an improved method of doing his work, using the property or labour of his employer to put his invention into practical form, and assenting to the use of such improvements by his employer, may, by taking out a patent upon such invention, recover a royalty or other compensation for such use." After pointing out that the existence of any such right had been uniformly denied, the court proceeded thus: "It should be borne in mind that the fact upon which so much stress has been laid by both sides, that the patentee made use of the property and labour of the government in putting its conceptions into practical shape, is important only as furnishing an item of evidence tending to show that the patentee consented to and encouraged the government in making use of his devices. The ultimate fact to be proved is the estoppel, arising from the consent given by the patentee to the use of his inventions by the government without demand for compensation.

The servants consent may be shown by parol testimony, or by conduct on the part of the patentee proving acquiescence on his part in the use of his invention. The fact that he made use of the time and tools of his employer, put at his service for the purpose, raises either an inference that the work was done for the benefit of such employer, or an implication of bad faith on the patentee's part in claiming the fruits of labour which technically he had no right to enlist in his service." The acquiescence of the claimant in this case in the use of his invention by the government is fully shown by the fact that he was in its employ; that the adoption of his inventions by the commanding officer was procured at his suggestion; that the patterns and working drawings were prepared at the cost of the government; that the machines embodying his inventions were also built at the expense of the government; that he never brought his inventions before any agent of the government as the subject of purchase and sale; that he raised no objection to the use of his inventions by the government; and that the commanding officer never undertook to incur a legal or pecuniary obligation on the part of the government for the use of the inventions or the right to manufacture thereunder."

This case was followed in one where it was held that a employé who, while earning weekly wages, constructs with his employer's tools and materials, and in his shop, machines which latter uses as part of his tools, without knowledge of any objection thereto, cannot, after obtaining a patent, enjoin his employer from further use of the particular machines. Blauvelt v. Interior Conduit & I. Co. (1897) 80 Fed. 906.

by the patent. If it relates to a certain description of machine, only the specific machine or machines which are set up during the term of the employment are protected".

An implied license of this description is not transferable by the employer to a third person".

The existence of a license is treated by the courts as a mixed question of law and fact, and a determination of this issue in one suit does not furnish a decisive precedent for another.

4. Engagement of employé for the purpose of prefecting an original conception of the employer. The rule applicable to cases in which a servant is employed to render assistance in perfecting the mechanical details and arrangements requisite for the complete elaboration of an invention of which the general idea has been conceived by the employer was thus formulated by Erle, J., during the trial of a patent case, in terms which were afterwards approved by all the other judges of the Court of Common Pleas :

"If a person has discovered an improved principle, and employs engineers, and they, in the course of the experiments arising from that employment, make valuable discoveries accessory to the main principle, and tending to carry that out in a better manner, such improvements are the property of the inventor of the original improved principle, and may be embodied in

6 Lowell J. in Wade v. Metcalf (1883) 16 Fed. 130. This point was not referred to by the Supreme Court (129 U.S. 202); but the doctrine enunciated in the text has received the approval of the Court of Appeals in City of Boston v. Allen (1898) 91 Fed. 248, where the scope of the doctrine was restricted by a ruling to the effect that, where an engineer employed by a city to build a ferry, makes and afterwards patents an improvement in the gangway used, no presumption, either of law or fact, arises in favour of an implied license to the city to use the patented device at another ferry built at another place several years afterwards. It was intimated, however, that, when the patented matter is a product, particularly if it is a minor product, or even if it is a minor machine, so that in either case it is used in quantities, its unlimited use during the time of employment may raise an implication of fact in favour of a license for a time likewise unlimited, as in the case of a process.

7 Hapgood v. Hewitt (1886) 119 U.S. 228, relying upon an earlier case in which the general rule was laid down that "a mere license to a party without having his assigns or equivalent words to them, showing that it was meant to be assignable, is only the grant of a personal favour to the licensees." Tivy Etc. Factory v. Corning (1852) 14 How. 193 (p. 216) citing Curtis, Patents, § 198.

8 City of Boston v. Allen, (1898) 91 Fed. 248.

his patent; and, if so embodied, the patent is not avoided by evidence that the agent or servant made the suggestions of that subordinate improvement of the primary and improved principle"1.

The principles which are controlling under such circumstances have been thus stated by the Supreme Court of the United States:

"Where the employer has conceived the plan of an invention and is engaged in experiments to perfect it, no suggestion from an employé, not amounting to a new method or arrangement, which in itself is a complete invention, is sufficient to deprive the employer of the exclusive property in the perfected improvements 2. But where the suggestions go to make up a com

1 Allen v. Rawson (1845) 1 C.B. 551 (p. 567). In the Court of Common Pleas, Tindal C. J. thus stated his views as to the facts in evidence: "It would be difficult to define how far the suggestions of a workman employed in the construction of a machine are to be considered as inventions by him, so as to avoid a patent incorporating them taken out by his em ployer. Each case must depend upon its own merits. But, when we see that the principle and object of the invention are complete without it I think it is too much that a suggestion of a workman, employed in the course of the experiments, of something calculated more easily to carry into effect the conceptions of the inventor, should render the whole patent void. It seems to me that this was a matter much too trivial and too far removed from interference with the principle of the invention, to produce the effect which has been contended for."

That a mechanic employed for the purpose of enabling the employer to carry his original conception into effect is not an inventor was assumed by Alderson, B., in his direction to the jury in Barker v. Shaw (1831) 1 Webst. Pat. Cas. 126.

2 In a latter judgment by the same court we find the passage: "Where a person has discovered a new and useful principle in a machine, manufacture, or composition of matter, he may employ other persons to assist in carrying out that principle, and if they, in the course of experiments arising from that employment, make discoveries ancillary to the plan and preconceived design of the employer, such suggested improvements are in general to be regarded as the property of the party who discovered the original principle, and they may be embodied in his patent as part of his invention." Collar Co. v. Van Dusen (1874) 23 Wall. 530 (563, 564).

The general rule is that "one, who, by way of partnership or contract, or in any other, empowers another person to make experiments upon his own conception for the purpose of perfecting it in its details, is entitled to the ownership of such improvements in the conception as may be suggested by such other person." Gedge v. Cromwell (1902) 19 App. D.C. 192 (198).

"A person may be the real author of a plan of a complicated machine, or invention which requires for its perfection the skill and, to some extent, inventive faculties of workmen or engineers in adapting the best means to