or improperly detained them after a disaffirmance of the sale, the action would have been maintainable.1

Whether a demand is necessary where property has been sold and delivered by one having no authority to sell, has been a point of conflict of authority. The better view, however, is that the unauthorized sale and delivery are sufficient to constitute a conversion, and hence that demand before suit is not necessary. It is conceded that if the buyer has taken the goods away, there is a conversion.3

2

A very common instance of the necessity of demand and refusal is where goods have been put into the hands of another for a special purpose, upon agreement to return them when the purpose is accomplished; in regard to which the rule is, that a breach of the contract by the mere failure so to return the goods does not amount to a conversion. Before the bailee can be liable in trover in such a case, supposing there had been no misappropriation or other act of dominion, there must be a demand for the goods and a refusal to restore them. An unqualified refusal will itself, in almost all cases, constitute a conversion.5

A qualified refusal to deliver goods on lawful demand may, however, be only prima facie evidence of a conversion.6 The defendant may have found the goods, and 1 Bloxam v. Hubbard, 5 East, 407.

2 Galvin v. Bacon, 2 Fairf. 28; Parsons v. Webb, 8 Greenl. 38; Stanley v. Gaylord, 1 Cush. 536; Trudo v. Anderson, 10 Mich. 357; Whitman Mining Co. v. Tritle, 4 Nev. 494. Contra, Marshall v. Davis, 348; Nash v. Mosher, 19

1 Wend. 109; Barrett v. Warren, 3 Hill,

Wend. 431; Talmadge v. Scudder, 38 Penn. St. 517; Sherry v. Picken, 10 Ind. 375; Justice v. Wendell, 14 B. Mon. 12.

3 Ely v. Ehle, 3 Comst. 506; Nash v. Mosher, supra; Marshall v. Davis, supra.

4 Severin v. Keppell, 4 Esp. 156.

5 Alexander v. Southey, 5 B. & Ald. 247, 250.

6 Burroughes v. Bayne, 5 H. & N. 296; Alexander v. Southey, supra.

refused to surrender them to the plaintiff until he shall have proved his right to them. It follows from what has already been said that such a refusal is justifiable, since, if the plaintiff is not entitled to the goods by right, the defendant as finder has the better claim; and he cannot or may not know that the plaintiff may not be a pretender until he has furnished evidence that he is not. And other cases of the kind might be stated; 1 the only question, where the refusal to return is qualified, is whether it is reasonable.2

1

If the demand be not made upon the defendant himself, but merely left at his house in his absence, it seems that a reasonable time and opportunity to restore the goods should be suffered to elapse before the defendant's noncompliance with the demand can be treated as a refusal amounting to a conversion. Non-compliance with the demand after a reasonable opportunity has been afforded to obey it is, however, clearly tantamount to a refusal, and is presumptive evidence of a conversion, thus requir ing the defendant to explain that the omission to deliver the goods was justifiable.

8

1 See Pollock, Torts, 306, 307, 2d ed.

2 Alexander v. Southey, 5 B. & Ald. at p. 250.

8 1 Chitty, Pleading, 160; Thompson v. Rose, 16 Conn. 71; White v. Demary, 2 N. H. 546.

CHAPTER XI.

INFRINGEMENT OF PATENTS, TRADE MARKS, AND

COPYRIGHTS.

§ 1. INTRODUCTORY.

Statement of the duty. A owes to B the duty (1) to forbear to make, use, or vend, without B's license, a thing patented by B; (2) to forbear, without B's license, to print, publish, or import any copyrighted book of which B owns the copyright, or knowing the same to be so printed, published, or imported, to sell or expose for sale any copy of such book; and to forbear to violate the rights of B in respect of any other copyrighted matter of which B owns the copyright.1

§ 2. OF PATENTS.

The Revised Statutes of the United States grant to patentees, their heirs and assigns, for the term of seventeen years, the exclusive right to make, use, and vend the patented article throughout the United States and the territories thereof; 2 and for an infringement they allow (besides bills in equity for equitable protection) an action on the case in the name of the party interested, either as patentee, assignee, or grantee.

That for which the laws give patents is invention,' something, that is to say, which is created by original thought, not something which is discovered except in the

1 It would make the statement of this duty far too prolix to spe cify all of the rights and duties arising under this last clause. 8 Ib. § 4919.

2 U. S. Rev. Sts. § 4884.

6

narrower sense of discovery. When therefore the word discovery' is used of something patented, it must be understood in the sense of 'invention.' The laws of nature may be discovered by man, but they cannot be invented by him; hence discovery of them cannot be patented.1 'Principle' or 'scientific principle' is often used in this sense of a law of nature, and in that sense falls without the patent laws.

6

Invention may cover processes, however, in which any of the laws of nature are called into use; but it is the process (or 'principle' or ' discovery' in that sense) that is patentable, not the law of nature, though that law may never have been known before. And then with regard to processes, it is not processes generally that may be patented. A merely mechanical process, or rather the effect produced by such a process, cannot be patented; or as the law has been laid down from the bench, a man cannot have a patent for the function of a machine,' 2 for that would be to prevent the use of better machines for performing the same function or attaining the same result. The processes necessary for making the machine may be patented, not the effect or result to be produced (except with reference to patents for designs). In a word, those processes are patentable which look to results which are to be produced otherwise than by any particular machine or by means not purely mechanical.*

Anything to be the subject of a valid patent must, besides being the subject of invention, be new and useful.5

1 Telephone Cases, 126 U. S. 531; O'Reilly v. Morse, 15 How. 112; Walker, Patents, § 2, 2d ed.

2 Corning v. Burden, 15 How. 252, 268.

8 Id.

4 Walker, § 6; Mowry v. Whitney, 14 Wall. 620; Tilghman v. Proctor, 102 U. S. 707; Telephone Cases, 126 U. S. 531.

5 Fermentation Co. v. Maus, 122 U. S. 413, 427 ; Telephone Cases, 126 U. S. 533.

Having the foregoing considerations in mind, the specific subjects of patent, by the laws of the United States, are the following; arts, machines, manufactures, compositions of matter, and designs.1 These terms are not intended to be used with perfect exactness, and yet within certain limits they are intended to be in a general way exclusive of each other; a patent would, however, be good, generally speaking, if it fell under any one of the subjects named, though it might have been improperly assigned in the letters-patent to a particular subject. But notwithstanding their inexactness, the terms have legal limits, and things which do not fall within the legal meaning of any of them cannot be covered by patents. Thus the word manufacture' has in the American law of patents a narrow and technical meaning; it appears to be limited to such things as are made by the hand of man, not embraced within the legal meaning of arts, machines, compositions of matter, or designs.2

6

Attention will now be turned to infringement. This must consist in the wrongful making, using, or vending the patented thing. But the statutes leave it to the courts to determine what constitutes a making, using, or vending.

Generally speaking, an infringement in the making takes place whenever another avails himself of the subject of the invention of the patentee, without such variation as will constitute a new discovery; or an infringement is a copy made after and agreeing with the principle laid down in the specification of the patent. When a person has obtained a patent for a new invention or a discovery made by his own ingenuity, it is not in the power of any one else, by simply varying in form or in immaterial par1 Walker, §§ 2, 20. 2 Id. § 17. 8 Curtis, Patents, § 289; Calloway v. Bleaden, Webs. Pat. Cas. 523