U.S. Supreme Court
Tyler v. Boston, 74 U.S. 7 Wall. 327 327 (1868)
Tyler v. Boston
74 U.S. (7 Wall.) 327
1. When a patent is claimed for a discovery of a new substance by means of chemical combinations of known materials, 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."
2. The doctrine of equivalents as applied to chemical inventions explained, and the distinction between mechanical inventions and chemical discoveries, where experiment is required to ascertain the effect of chemical substances, pointed out.
3. Whether one compound of given proportions is substantially the same as another compound varying the proportions is a question for the jury.
Tyler brought suit, in the Circuit Court for Massachusetts against the City of Boston for infringement of a patent, the case being this:
The plaintiff professed to have discovered a new compound substance, being a combination of fusel oil with the mineral and earthy oils, which compound constitutes a burning fluid, "by which term," he says, "I mean a liquid which will burn for the purpose of illumination without material smoke in a lamp with a small solid wick and without a chimney."
The claim of his patent which the defendant was charged chanrobles.com-red
with infringing, was
"the compound produced by the combination of the mineral or earthy oils with fusel oil in the manner and for the purpose substantially as herein set forth, said compound constituting a new manufacture."
The component parts of this new manufacture were described as "by measure crude fusel oil one part, kerosene one part." This combination, the patent stated, might be varied by the substitution of naphtha or crude petroleum in place of Kerosene, or a part of the kerosene by an equal quantity of naphtha or crude petroleum, "the exact quantity of fusel oil which is necessary to produce the most desirable compound must be determined by experiment."
The defendants used a burning fluid composed of naphtha seventy-two and fusel oil twenty-eight parts, and experts, chemists, proved that seventy-two parts in bulk of naphtha was the substantial equivalent of twenty-eight parts of kerosene.
The court below charged the jury, "that the patentee, in suggesting that naphtha might be substituted for kerosene, intended to describe the same proportion in the combination," and
"that the jury should understand the construction of the suggested substitution, to-wit, naphtha for kerosene, as contemplating the same proportion of the two ingredients -- that is, one and one, or fifty percent of one, and fifty percent of the other."
It charged further 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."
Under this charge, the jury found for the defendant, and the case was now here on error. chanrobles.com-red