are formed, are the natural properties of steam; its expansiveness and condensibility; whether the machines are formed in one shape or another; whether the cylinder is kept hot or suffered to cool; whether the steam is condensed in one vessel or another, still the radical principles are the same. When the present patentee set his inventive faculties to work, he found fire engines already in existence; and the natural qualities of steam already known, and mechanically used. He only invented an improvement in the mechanism, by which they might be employed to greater advantage. There is no newly discovered natural principle as to steam, nor any new mechanical principle in his machine. The only invention, is a new mechanical employment of principles already known. The specification describes a practical use of improved mechanism, the basis on which the improvement is founded. The object of the patentee was, to condense the steam without cooling the cylinder: the means adopted to effect this, were to inclose the cylinder in a case which will confine the heat, or transmit it slowly; to surround it with steam or other heated bodies; and to suffer neither water, nor any other substance, colder than the steam, to enter or touch it during that time. These means are set forth. The objection

is, that there is no drawing or model of a particular engine; and where is the necessity of such drawing or model, if the specification is intelligible without it? Had a drawing or model been made, and any man copied the improvement, and made a machine in a different form, no doubt this would have been an infringement on the patent: why? because the mechanical improvement would have been introduced into the machine, though the form was varied. It follows from thence, that the mechanical improvement, and not the form of the machine, is the object of the patent; and if this mechanical improvement is intelligibly specified, of which a jury must be the judges; whether the patentee calls it a principle, invention, or method, or by whatever other appellation, we are not bound to consider his terms, but the real nature of his improvement, and the description he has given of it; and we may, I think, protect him without violating any rule of law. The patent is for a method already adopted; and the two first and most material articles, are set forth as already accomplished; and the case states it was new and useful at the time of making the patent. I therefore consider the most essential part of the patent, the keeping the cylinder hot, inclosing it in a case, and surrounding it with steam, as carried into practi

cal effect at the time of granting the patent: this the defendant has infringed. As to the -objection of the want of a drawing or model, that at first struck me as of great weight. I thought it would be difficult to ascertain what was an infringement of a method, if there was no additional representation of the improvement, or thing methodized. But I have satisfied my mind thus: infringement or not, is a question for the jury. In order to decide this case, they must understand the the nature of the improvement, or thing infringed. If they can understand it without a model, I am not aware of any rule of law which requires a model, or drawing, to be set forth, or which makes void an intelligible specification of a mechanical improvement, merely because no drawing or model is annexed. In the present case, the want of a drawing or a model did not occasion any difficulty to the jury: they have expressly decided, that Mr. Watt has the merit of a new and useful invention; and that this invention was infringed by the defendant. How then can I say that they could not understand it for want of a drawing? especially, when they have added that the specification is sufficient to enable a mechanic, acquainted with fire engines previously in use, to construct fire engines producing the effect of lessening the

consumption of fuel and steam, upon the principle invented by the plaintiff. For these reasons, I think the second objection, that no particular engine is set forth, is not of sufficient weight to destroy the effect of the pa

tent.

Heath, J.* This patent is expressly for a new invented method for lessening the consumption of steam and fuel in fire engines.It appears that the invention of the patentee is original, and may be the subject of a patent; but the question is, inasmuch as his invention is to be put in practice by means of machinery, whether the patent ought not to have been for one or more machines; and whether this is such a specification as entitles him to the monoply of a method? If method and machinery had been used by the patentee as convertible terms, and the same consequences would result from both, it might be too strong to say that the inventor should lose the benefit of his patent, by the misapplication of his term. In truth, it is not so. His counsel have contended for the exclusive monopoly of a method of lessening the consumption of steam and fuel in fire-engines,

* The opinion of Judges Heath and Butler in this cause are controverted, in the case of Hornblower and Maberly against Boulton and Watt, cited hereafter.

and that therefore would better answer the purposes of the patentee, for the method is a principle reduced to practice; it is in the present instance the general application of a principle to an old machine. There is no doubt that the patentee might have obtained a patent for his machinery, because the act of parliament he obtained acknowledged his patent, and he himself, in 1782, procured a patent for his invention of certain new improvements upon steam and fire engines, for raising water, &c. which contained new pieces of mechanism, applicable to the same. Upon this statement, the following objections arise to the patent, which I cannot answer, viz.: that if there may be two different species of patents, the one for an application of a principle to an old machine, and the other for a specific machine, one must be good, and the other bad. The patent that admits the most lax interpretation should be bad, and the other alone conformable to the rules and principles of common law, and to the statute on which patents are founded. The statute 21 Jac. 1. prohibits all monopolies reserving to the king by an express proviso, so much of his ancient prerogative as shall enable him to grant letters patent, and grants of privileges for the term of fourteen years, or under, of the sole working or making of any