PART I. PATENTABLE INVENTION. § 1. The Statute. Section 4886 of the Revised Statutes of the United States declares that "Any person who has invented or discovered any new and useful art, machine, manufacture, or composition of matter, or any new and useful improvement thereof, not known or used by others in this country, and not patented or described in any printed publication in this or any foreign country, before his invention or discovery thereof, and not in public use or on sale for more than two years prior to his application, unless the same is proved to have been abandoned, may upon payment of the fees required by law, and other due proceedings had, obtain a patent therefor." The statute, however, does not define what is meant by the word "invented" or what is meant by the term "invention," and consequently the determination of what constitutes invention is left to the courts. § 2. Dictum of the Court. As to what constitutes invention the following dictum was pronounced in 1880 by the United States Supreme Court (Pearce v. Mulford, 102 U. S. 112, 26 L. ed. 93): "But all improvement is not invention, and entitled to protection as such. Thus to entitle it, it must be the product of some exercise of the inventive faculties." What these faculties are, or how they are to be distinguished from the constructive faculty of the mind, is a matter that is left by the Court in profound obscurity. No two persons can agree as to the line of demarcation between the two faculties, because from the variations in the characters of the minds of men, their differences in training and in experience, a change which to one mind appears to have involved the exercise of the so-called inventive faculty, is thought by another (after the event) to have been the result of merely the constructive faculty or of mechanical skill. Hence to test the existence of invention by the assumption of the exercise of mental faculties by which it has been produced, and which are indefinable, amounts simply to an attempted determination of a truth by mere judicial opinion, without reliance upon evidence and without recourse to rules by which a just conclusion can be reached. § 3. Determination of Invention by Assumption of the Action of a Peculiar Mental Faculty a mere Opinion. To the scientific mechanic the procedure of determining the nature of an effect by an assumption of a cause by which it may or may not have been produced,. is contrary to the method of proceeding in other cases. Thus, the faculties of the mind are forces, and, as with other forces, we know nothing of them except by their effects. We know nothing of the real constitution of the forces of electricity and heat; it is true that we have hypotheses that electricity is a fluid of some un-known kind, and that heat is a form of motion, but. these are but hypotheses which suit the present condition of human knowledge. On the other hand we know that when a certain effect is produced, the action or presence of the agency, whether heat, or electricity, or some other impalpable force, is to be inferred. It is the same with the impalpable forces of the human mind, such as those we call the constructive faculty and the inventive faculty; their action is to be inferred from the effects produced; and we should determine whether one or the other faculty has acted by the nature or character of the effect, instead of attempting to classify the effects as inventions or as mere skillful constructions falling short of invention, by an assumption that in some cases the inventive faculty has been exercised, while in others only the constructive faculty has acted,-an assumption which is incapable of proof in every case, and is a matter of mere opinion. § 4. Invention a Change from what is Old. On the other hand, it has been well said (1 Robinson, Patents, p. 114) that "an invention is an unchangeable fact to which the law must conform." If this be true, then that fact, like any other fact, should be susceptible of being proved by evidence, and should not be determinable by the mere opinion of the court before whom the question of invention is tried. An invention, according to the statute first quoted, must be "new;" hence it must of necessity amount to a change from that which has previously been known, and if the question of how much or how little change is required to constitute invention is to be determined in every case by the mere opinion of the court, formed in every case after the event, the matter is at once removed from the domain of evidence and is cast upon the sea of uncertainty where it is subjected to the varying qualities and the shifting views of the minds of judges, who, however well trained in the science of law, have as a general rule no personal experience in the operation of an inventor's mind. § 5. Determination of Invention by Rules and Evidence. If the nature or character of the thing or effect produced is to determine whether it is to be classified as an invention or as a mere construction produced by mere mechanical skill, the question naturally arises, by what rules, if any exist, are we to measure this nature or character. On this subject it appears that the earlier decisions of the courts differ materially from many of those of later years in the respect that certain definite rules are deducible from the former, and those which have followed in the same line; while according to many later decisions of our highest court, invention is a matter of mere opinion formed by the court after the event. According to the earlier decisions and those which have followed in the same line, a change was decided to be new under the Patent Law when it had not been known or used before (Earle v. Sawyer, 4 Mason, 1); and to be useful if it would accomplish the purpose for which it was designed, and was not noxious or hurtful. These two requirements of novelty and utility are clearly susceptible of proof by evidence; and it is deducible from the earlier decisions and those which have followed in the same line, that a change which involves those requirements is an invention within the meaning of the Patent Law with certain well defined exceptions. § 6. Exceptions to the General Rules. These exceptions are that the change, even when new and useful, does not amount to invention when it is either one of the following matters: A simple change of form, (using the language of the old Act of 1793) or (using the language of later days) a mere change of form. A mere change in size or degree. A mere change in proportions. A mere change of location. A mere change of arrangement. A mere application of an old thing to a new purpose; or a double use of an old thing, as such an application is frequently styled. A mere application of an old thing to perform its usual functions with its usual mode of operation, or move ment. A mere substitution of one old device for another. A mere change of the direction of movement of a moving device. The discovery of a new property of matter. The word mere as above used is significant and important, because it involves the proposition that there are changes of some kind in each of the above respects which are not mere changes, but are substantial and amount to invention when the changes are new and useful. A consideration of a few cases will demonstrate the correctness of this proposition. 7. Invention by Change of Form. As an instance of a change of form which was an invention and patentable, we have the case of the Winans coal car of conoidal form. Previous to the date of his |