delivered the opinion of the Court:

It is well-settled law that a patent cannot issue for a result sought to be accomplished by the inventor of a machine, but only for the mechanical means or instrumentalities by which that result is to be obtained. One cannot describe a machine which will perform a certain function, and then claim the function itself, and all other machines that may be invented by others to perform the same function.

Sec. 4888, Rev. Stat., U. S. Comp. Stat. 1901, p. 3383, requires that the applicant for a patent shall describe his invention in such full, clear, concise, and exact terms as to enable any person skilled in the art to make and use the same; and that, in case of a machine, he shall explain the principle thereof, and the best mode in which he has contemplated applying that principle, so as.to distinguish it from other inventions; and that he shall particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention •or discovery. The purpose of this requirement is not only to secure to the inventor the benefit of his invention, but also that -the public may know what they are prevented from doing during rthe existence of his monopoly. Brooks v. Fiske, 15 How. 212, *252214, 14 L. ed. 665, 666; O'Reilly v. Morse, 15 How. 62, 119, 14 L. ed. 601, 626. In the case last cited the requirements are thus stated by Chief Justice Taney:

“Whoever discovers that a certain useful result will be produced in any art, machine, manufacture, or composition of matter by the use of certain means is entitled to a patent for it,, provided he specifies the means he uses, in a manner so full and exact that any one skilled in the science to which it appertains can, by using the means he specifies, without any addition to- or subtraction from them, produce precisely the result he describes. And if this cannot be done by the means he describes, the patent is void. And if it can be done, then the patent confers on him the exclusive right to use the means he specifies to produce the result or effect he describes, and nothing more. And it makes no difference, in this respect, whether the effect is produced by chemical agency or combination; or by the application of discoveries or principles in natural philosophy, known or unknown before his invention; or by machinery acting altogether upon mechanical principles. In either case, he must describe the manner and process as above mentioned, and the end it accomplishes. And any one may lawfully accomplish the same end, without infringing the patent, if he uses means substantially different from those described.”

It is the duty of the Commissioner of Patents to see that these conditions are performed.

Testing the appealed claims by the rules above stated, we are of the opinion that they were rightly rejected as claims for functions or results. If allowed, they would cover means substantially different from those described, which might be discovered by another for accomplishing the same results, namely, the determination of the percentage of entrained liquid in the vapor, as in claim 13, and the indication of heat characteristics and conditions as to dryness, etc., as in the other claims. We deem it unnecessary to add anything, by way of argument, to the grounds assigned by the Primary Examiner and the Examiners-in-Chief in their decisions, which are sufficiently full and satisfactory.

*253Tbe decision appealed from will be affirmed. It is so ordered, and that the clerk certify this decision to the Commissioner of Patents as the law requires. Affirmed.