perature was to be regulated; or regulating the ventilation of a room by governing the admission of air into it. Afterwards the matter came before Judge Nelson on a motion for a new trial. This motion was denied, and the Court made the following statement of the patentee's invention, of the pre-existing structures, and of the law as applied to the facts.

"The substance of the discovery as claimed by the plaintiff and secured to him by the patent, is the application of the principle of the contraction and expansion of a metallic rod, by the use of certain mechanical contrivances particularly described and set forth, to the cast or sheet iron stove in common use, by which means he produces a self-regulating power over the heat of the same at any given degree of heat that may be desired within the capacity of the stove. This is the thing invented. It is in a word the application of a well known principle to a new and useful purpose; and the question is whether or not the patentee was the first and original inventor, or whether it was before known and in public use. Now, although it is shown (assuming for the present that we may look into the books not in evidence) that the principle had before been applied to the regulation of heat, as in the instance of Dr. Ure's Thermostat,' and Bonnemain's Heat Regulator,' and some others, yet, from aught that appears from the testimony or from any book that has been produced, the plaintiff was the first person who applied the principle to the regulation of the heat of stoves; and for this he was entitled to a patent, and to be protected in its enjoyment. Phillips, Patents, chap. 7, § 6, p. 101. It is not a new use of the principle as previously applied to the regulation of heat, which would not be patentable; but a new application

of it, by new mechanical contrivances and apparatus, by means of which a new and beneficial result is produced in the use of the article to which it has been thus applied, namely, the common cast or sheet iron stove." Foote v. Silsby, 1 Blatchf. 445.

Subsequently the case came again before Judge Nelson upon the trial of a feigned issue with reference to the novelty of the patented invention, several alleged anticipations of the two claims of the patent having been put in evidence. The Court then charged the jury as follows as to the rule of patent law applicable to the first claim, which was not restricted to particular machinery.

"Where a party has discovered a new application of some property in nature, never before known or in use, by which he has produced a new and useful result, the discovery is the subject of a patent, independently of any peculiar or new arrangement of machinery for the purpose of applying the new property in nature; and, hence, the inventor has a right to use any means, old or new, in the application of the new property to produce the new and useful result, to the exclusion of all other means. Otherwise the patent would afford no protection to an inventor in cases of this description; because, if the means used by him for applying his new idea must necessarily be new, then, in all such cases, the novelty of the arrangement used for the purpose of effecting the application would be involved in every instance of infringement, and the patentee would be bound to make out, not only the novelty of the new application, but also the novelty of the machinery employed by him in making the application." Foote v. Silsby, 2 Blatchf. 264.

The Court on this subject referred to the well known hot-blast case of Neilson v. Harford (Webster, Pat. Cases, 295, 310, 328), and also to Curtis on Patents, § 81.

The subject of the second claim of the patent was the new combination of four devices by which the application of the differential expansion of two different metals was made to regulate the draft valve of the stove, and thereby regulate the heat. On this subject the court said:

"There are four elements in it which I have named. The claim is for the combination of all of them, not for any one of them. It is immaterial whether or not the plaintiff was the inventor of any one or two of them, or of any less than the combination of the whole. They may all be old; and yet if the plaintiff was the first to combine all four of them for the particular purpose of regulating the heat of the stove by means of its own heat, he is entitled to be protected in that improvement." Foote v. Silsby, 2 Blatchf. 270.

It thus appears that when there is a new application of some property in nature, never before known or in use, by which "a new and useful result is produced," the thing done is not a mere application but is an invention or discovery constituting the subject-matter of a patent. It further appears that when the application of the old thing is by a new combination of it with other devices, it is not a mere application, but produces a new combination which is an invention.

With reference to this case of the Foote heat regulator it is proper to add that the first claim was found to be anticipated by an older construction; consequently a disclaimer was filed restricting its scope to the regulation of the heat of the stove in which the expansive rod shall be acted upon directly by the heat of the stove, or the fire which it contains.

The case was subsequently appealed to the United

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States Supreme Court which by a majority affirmed the decision of the lower court as to the validity of the patent. Silsby v. Foote, 2 Blatchf. 270, 61 U. S., 20 How. 378, 15 L. ed. 953.

The fact that the first broad claim of the Foote patent (before the disclaimer was filed) was anticipated by an older invention does not affect the rule of law laid down by Judge Nelson as applicable to such a case.

§ 14. Invention by Application of an Old Device to Perform its Usual Function.

The mere application of an old thing to perform its usual function does not amount to an invention. Thus let it be assumed that some inventor has devised new seats for a carriage body fitted with a top, but has not represented it in his patent nor manufactured it with side curtains to keep out wind and rain, while such side curtains have been long in common use for the same purpose in other carriages fitted with tops. Would the application of side curtains to the carriage body with the new seats be an invention, when the side curtains had been employed in the same art to perform the same function with the same mode of operation? We think that the application of the side curtains under such circumstances would be a mere application falling short of invention.

There are, however, cases in which the change amounts to more than a mere application. Thus, a Reissue Patent, No. 6229, was granted for the invention of Keene for improvements in carriage steps, the main improvement consisting in the application of a covering or plating of india rubber to the carriage step so as to produce a resilient surface which also tended to prevent slipping.

In a suit under the patent it was proved that similar platings of india rubber had been applied to stirrups and to the soles of shoes, and that such earlier platings were resilient and tended to prevent slipping. It was also proved that iron (non-resilient) carriage steps had been constructed previously with substantially the same form of surface as those of the patented rubber platings. The Court decided that the use of the preceding stirrup and sole platings, and the use of the non-resilient carriage steps did not establish any anticipation of the invention; and the patent was sustained. Rubber Step Mfg. Co. v. Metropolitan R. Co. 3 Bann. & Ard. 252. In this case it appears that the patentee's invention, although an application of an old thing (india rubber plating) to perform an old function (to give resiliency and to prevent slipping) introduced this function or mode of operation into a class of devices (carriage steps) or art in which it. had not been previously attained; and in such case the change is not a mere application but produces a new combination which amounts to invention.

Another instance of the application of an old device to perform its usual function is found in the steam packing of D. C. Gately described in his Patent No. 86296, January 6, 1869. It consisted of a peculiar packing of cloth and certain other materials combined with an elastic backing of vulcanized india rubber. The first member of this combination (the peculiar packing) was old, being described in an earlier patent, but it was defective in being too rigid and in lacking the requisite elasticity to enable it to exert the requisite elastic pressure against piston rods which were packed with it. On the other hand, the second member (the vulcanized rubber) was old as an elastic material, and it had been