Tyler v. Boston/Opinion of the Court

The patent states that 'the exact quantity of fusel oil which is necessary to produce the most desirable compound must be determined by experiment.'

Now a machine which consists of a combination of devices is the subject of invention, and its effects may be calculated a priori, while a discovery of a new substance by means of chemical combinations of known materials is empirical and discovered by experiment. Where a patent is claimed for such a discovery, it should state the component parts of the new manufacture claimed with clearness and precision, and not leave the person attempting to use the discovery to find it out 'by experiment.' The law requires the applicant for a patent-right to deliver a written description of the manner and process of making and compounding his new-discovered compound. The art is new; and therefore persons cannot be presumed to be skilled in it, or to anticipate the result of chemical combinations of elements not in daily use.

The defendants used a burning-fluid composed of naphtha seventy-two and fusel oil twenty-eight parts; and expert chemists proved that seventy-two parts n bulk of naphtha was the substantial equivalent of twenty-eight parts of kerosene.

This term 'equivalent,' when speaking of machines, has a certain definite meaning; but when used with regard to the chemical action of such fluids as can be discovered only by experiment, it only means equally good. But while the specification of the patent suggests the substitution of naphtha for crude petroleum, it prescribes no other proportion than that of equal parts by measure. The explanation that the 'kerosene must be replaced by an equal quantity of naphtha' does not alter the case.

The charge which the court gave is a clear and intelligible statement of the principles of law which should govern the jury in making up their verdict. It said properly, that 'whether one compound of given proportions is substantially the same as another compound varying in the proportions-whether they are substantially the same or substantially different-is a question of fact and for the jury.'

If the jury in finding for the defendants have erred, the remedy is not in this court.

JUDGMENT AFFIRMED.