hereinafter mentioned. The plan and limits of this paper do not include the question of compositions in which there has been a substitution of ingredients. Altho in a sense this is a substitution of material the situation is different because ordinarily the identity of material substituted in an article is not lost, while in the case of a composition the substituted ingredient is lost. As stated by Justice Bradley in Hicks vs. Kelsey, 18 Wall. 670 (1873) "in compositions of matter a different ingredient changes the identity of the compound, whereas an iron bar in place of a wooden one and subserving the same purpose does not change the identity of a machine." This is believed to be a workable distinction and will be followed.

We may assume that usually there is no invention in making a substitution of material. The reason for this is simply that substituting one material for another is an obvious expedient, resorted to by neolithic man when he substituted woven cloth for animal skins, and again when he substituted metal for stone implements. The broad idea of substitution is therefore lacking in novelty and by itself does not constitute progress. Sometimes, however, there is not only substitution, but also something in the nature of discovery, and in the discovery there may be patentable merit. Sometimes also the substitution may be incidental to other changes, the whole constituting invention. Again the results may be so striking as to carry conviction that invention must be present, even tho the inventor is unable to point out precisely where it lies. In any of the suggested situations patents will be sustained. These are not submitted as an enumeration of every attribute that may ever render substitution inventive, but they are believed to embrace all the instances in which substitution has properly been sustained, up to the present time. They are somewhat developed in the following table:

I.

Discoveries.

1. New property in the material.

2. New use of a known property.

3. Nonanalogous use for article or machine.
4. Hidden defect in prior devices.

II. Incidental substitution.

5. New method of manufacture.
6. New Construction.

III. Extraordinary result.

7.

Success out of failure.

Decisions that have sustained patents under each of these seven heads will be separately analyzed.

1. Development of new property in the material.

If the invention brings to light a property in the substituted material not previously recognized, the case for patentability is very strong. It has sometimes been suggested, but perhaps never with judicial approval, that this is the only situation in which a change of material should be accepted as amounting to a contribution that would warrant a monopoly. Frost v. Cohn, 119 Fed. 505, 508 (C..C. A.-2: 1902). Certainly when this factor is present the legal problem is not difficult.

Perhaps the most frequently cited case under this head is Westmoreland v. Hogan, 167 Fed. 327 (C. C. A.— 3: 1909). The old metal top of salt dredges had been replaced by one composed of celluloid, bringing to light the previously unknown attribute of celluloid of insulating against moisture. The inventor, himself, apparently did not appreciate this particular advantage in the new top, and whether or not there is any such advantage may be questioned. Accepting the court's conclusion of fact, however, the patent was clearly valid. The prior art showed that celluloid had been used on talcum powder bottles, but this was dismissed as not pertinent because the non-hygroscopic nature of talcum powder would preclude the discovery of this particular property in the material.

Three other cases involve electrical patents, one of them for a lamp filament, one for a resistance element, and the third for an insulator. In General Electric Company v. Laco Philips, 233 Fed. 96 (C. C. A.-2: 1916), the substitution of tungsten for carbon in a lamp filament was characterized as invention of high order. The opinion of the court is not very helpful for the present purpose, since it relied upon the authority of Edison v. U. S. Electric Lighting Co., 52 Fed. 300; 61 O. G. 564; 1892 C. D. 606 (C. C. A.-2), omitting discussion of principles. The earlier case was held to have settled conclusively that the material of which a filament is composed may be the subject matter of invention. It would seem, however, that the patentability of a filament made of tungsten might properly have been based on the ground of discovery of its high resistivity and practical non voltilization in vacua, these properties having, it appears, been previously unknown.

The resistance element case is closely allied to the preceding, the invention being an element composd of a known alloy. General Electric Co. v. Hoskins, 224 Fed. 464 (C. C. A.—-7: 1915). The new property discovered was the high specific resistivity coupled with durability; without the latter the former is not commercially useful. In these properties the alloy had been found superior to everything then known except platinum, and that material was and is prohibitively costly. This case may be close to the border line, but is thought to fall within it.

Besides these two cases involving electrical conductors, there is the third case mentioned, involving an insulator, more specifically an improvement in insulating submarine cables. Colgate v. Western Union Telegraph Co., 15 Blatchford 365, 369; 14 O. G. 943; 1878 C. D. 440 (C. C., S. Dist. N. Y.). India rubber had previously been used, and the material substituted was gutta percha. This also had been used to cover wires serving as a protection against abrasion or similar injurious action. Nevertheless the patent was sustained because of the discovery of the electrical insulating property of the gutta percha.

A meagerly reported British case sustained a patent for soft metal packing, the inventor having discovered a non-friction property in the metal. Newton v. Vaucher, L. J., 1852, N. S., Vol. XXI, part II.

In these cases of discovery of a new property it seems that logically the inventor should receive a monopoly on all uses of the property. Socially, such an expansion of monopoly might be unwise.

2. New use of known property.

Even tho it may have been known that a particular material possessed a particular property, the novel utilization of this property will usually be patentable. The distinction between a new use of a known material and a new use of a known property, needs to be kept in mind. In the ordinary substitution case the old material is applied to a new use, but the properties availed of are availed of just as they were before the toughness of wrought metal, or the transparencey of glass, or the low melting point of lead. Contrasting with such instances, the principle discussed under this sub-heading involves the use of a property, function, or attribute which though previously known, had not been utilized.

What has been suggested as to granting a broad monopoly on the use of a newly discovered property would be either not applicable to this class of cases, or of much less force here, for the reason that the property itself has not been discovered.

Of the two cases to be considered, one turned on the porosity of yoshino paper as utilized in the making of stencils, Dick v. Fuerth, 57 Fed. 834 (Cir. Ct. D. N. J., 1893), and the other on the comparative non-corrosiveness of rubber as utilized in a steam-gage gasket, Dalton v. Nelson, 2 Bann. & A. 225 (C. C., S. D. N. Y.: 1876). The first of these cases may be said to have included a double substitution of material. The patent was for a "prepared sheet for stencils," and, in one aspect, consisted of the substitution of a thin highly porous sheet

of material such as Japanese dental paper, or yoshino, coated with a soft waxy substance such as paraffine in place of a sheet of ordinary cellulosic material covered with hard wax, whereby old properties were combined to yield a new result. The yoshino paper, unlike others, has a loose fibrous texture that provides sufficient porosity to permit of its use as a transmitting medium while the soft wax, by virtue of its highly plastic nature, is easily displaced in conformity with the lines of impression of a writing or printing instrument, leaving impervious the unimpressed surface of the paper. Such a stencil was particularly valuable for the perfect reproduction of loop letters or in general any configurations wherein there were void spaces, because the ordinary stencil cannot produce the little solid islands required in such spaces as the center of the letter O. The new properties availed of by the patentee had never before received consideration as being applicable jointly to the stencil art. The court acknowledged that the general properties of porosity and plasticity as related to the materials in question were well known and that merely extending the application of them might be a matter of degree, yet it was concluded that in view of the novel result the difference wrought was really one of kind rather than of degree. Therefore the patent was sustained.

Altho rubber had earlier been used as gaskets in various places, on delivery valves for instance, the use of vulcanized rubber on the opposing surfaces of a steam. gage, instead of cork, leather, or soft metal, was held to be patentable in the other case cited. The quality not previously utilized was the resistance to corrosive and erosive action by the steam. The other materials used had lacked this property, and it seems that the property had not been utilized in the rubber-at least it is only upon that assumption that the case, herein before cited, may be accepted as consistent with the test for patentability herein developed. In expressing its opinion the court said: "Here the substitution does not merely produce the same result in the same way, but produces a