ment of the patent. (5 H. L. Cas. 505; 16 C. B. 713; 25, L. J., C. P. 8.)

Crompton, J., in delivering judgment in the Exchequer Chamber, said: "The discovery of the new mode of making the carburet in the pot, in the course of the process, so as to be ready to alloy with the steel in a subsequent part of the process, may have been a discovery and an improvement on the plaintiff's invention, for which a patent might perhaps have been taken out, and, if taken out by a stranger, the plaintiff could not have used the new method without infringing the patent for the improvement. On the other hand, the new method could not in such case have been carried on without infringing the plaintiff's patent, if, as I think, it was an improved and neater mode of bringing the two substances together." (22 L. J., C. P. 10.)

Coleridge, J., in delivering judgment in the same Court, said: "There can be no doubt, I think, that an equivalent has been used. If that equivalent were known at the date of the specification to the plaintiff or ordinary chemists-those, I mean, who would bring to the reading of the specification such knowledge as must be presumed in those to whom the patent must be taken to be addressed —then it is within the specification, and the use of it is an infringement. If not, the contrary conclusion follows, and the use of it is an improvement, in virtue of a new discovery. . . Whether the equivalent be in its nature near to or remote from the thing itself, seems to be in principle wholly immaterial, and equally so that the one should be so nearly identical with the other, as that the one should be the component parts and the other the composite substance." (Ib. 13.)

The Judges, in answering the question put to them by the House of Lords, differed as to the question of infringement.

Crowder, J.: "The process of the plaintiff in error is an improvement upon the invention of the defendant in error (the patentee), while at the same time it is an infringement of his patent." (25 L. J., C. P. 11.)

Williams, J.: "Though the use of a chemical or mechanical substitute, which is a known equivalent to the thing pointed out by the specification and claimed as the invention, amounts to an infringement of the patent, yet if the equivalent were not known to be so at the time of the patent and specification, the use of it is no infringement. If a patent is taken out for the application of a principle, coupled with a mode of carrying the principle into effect, the patentee is entitled to protection from all other modes of doing so, whether known or not known at the time of the specification." (Ib. 13.)

Erie, J.: "I am of opinion that a patent for the use of a substance in a process is infringed by the use of the elements of that substance known to be equivalent thereto at the time of the use, if used for the purpose of taking the benefit of the patent and of making a colourable variation therefrom. If the discovery had been made after the patent, that carbon and manganese were elements of the carburet, equivalent to the carburet

of manganese in the patented process, the use of those elements in that process for the purpose of being equivalent to the carburet, would, in my judgment, be a colourable variation and an infringement." (Ib. 15.)

The Lord Chancellor said that judgment ought to be for the defendant on the short ground that the invention claimed was for the use of a particular substance, whereas the defendant had used two other substances of a cheaper kind, the use of which for the same purpose was not known when the patent was obtained. (Ib. 21.)

(k) BOVILL v. PIMM. [1856]

In 1844, G. obtained a patent for "improvements in grinding wheat and other grains." He described as his invention "the forcing and distributing of atmospheric air from the eye or centre of mill-stones, for the purpose of cooling the grain during the process of grinding;" this was effected by an air-box placed below the mill-stones, into which air was forced by the rapid rotation of a fan or blower, which caused a current of air perpendicular to the axis of the fan; and the air was conducted by a pipe through the eye of the lower stone to the centre of the two stones, and there distributed between them by an apparatus provided with fans or arms. In 1846, the plaintiff obtained a patent for "improvements in manufacturing wheat and other grain into meal and flour." His invention consisted in the application of ventilating vanes or screws at the centre of the stones for supplying the air between the grinding surfaces; a portable ventilating machine, blowing by a screw vane, which caused a current of air parallel to the axis of the vane, was attached externally to the eye of the upper mill-stone; the screw vane being set in rapid motion, the air was compelled to pass through the eye into the centre of the two stones, and so find its way out between them. In 1851, the defendant obtained a patent for "improvements in grinding wheat," and his plan was to remove from the centre of both stones a large circular portion of each, and in this space, opposite to the separation of the two stones, to place a fan or blower, by the rapid rotation of which a centrifugal motion was given to the air, and it was driven between the stones :-Held, that the defendant's invention was no infringement of the plaintiff's, but that each was a new method of accomplishing a well-known object, viz., the cooling grinding substances by the common principle of obtaining a current of air by a rotating vane. (11 Exch. 718.)

Pollock, C.B., in delivering the judgment of the Court, said: "Where a subject is not new, as this certainly was not, viz., the cooling of substances undergoing the process of grinding' (which had been long known to be a desideratum in grinding, and to effect which various contrivances had been adopted, and several, if not many, patents taken out), any patent taken out for a method of performing the operation is substantially confined to that method, and cannot be extended to other methods obviously different, because they involve some common principle applied to the common

object, and may apparently be described by the same general. phrase." (Ib. 739.)

(1) SIMPSON v. HOLLIDAY. Ch. [1864]

If a patentee claims as his invention the mixing of two chemical substances, and boiling them together, to produce a certain result; and the same result is arrived at by mixing the two substances together in the presence of a third body, without boiling, that would be an infringement. (20 Newt. Lon. Journ., N. S. 111.)

(m) NEEDHAM v. OXLEY. Ch. [1865]

Where a patentee has been led up to the invention of his patented machine, by an idea thrown out by a previous patentee of a machine for the same purpose, but arrives at a similar result by another and different mode, there is no infringement. (21) Newt. Lon. Jour., N. S. 300.)

(n) CURTIS v. PLATT. H. L. [1866]

Held, affirming the judgment of the Lord Chancellor, that a patent for an entire combination is not infringed by a different combination, for the same object, of the same elements, though important, or of equivalents for them, if not a mere colourable evasion or imitation. The principle which protects a patentee against the use by others of mechanical equivalents is inapplicable to a case where the whole invention depends entirely on the particular machinery by means of which a well-known object is attained. (35 L. J., Ch. 852.) The Lord Chancellor, in delivering his judgment in the court below, said: "If the invention be, as I have already described, nothing in the world more than a particular means to attain to a given result which is perfectly well known, then the invention is for the means, and you can no more prevent the invention of one distinct set of means being interfered with-you can no more say that it interferes with the invention of another, than you could say originally that there ought not to be patents granted for the invention of distinct means to an end." (11 L. T. Rep. N. S. 249.)

(0) MURRAY v. CLAYTON. Ch. [1872]

A clumsy imitation of a patented machine, or a patented article, may be an infringement, although it is not such as would have been an anticipation defeating an inventor's right to a patent. Decided on the authority of Daw v. Eley. (L. Rep., 7 Ch. 585.)

(p) JOHNSON v. RYLANDS. [1873]

Action for infringement of a patent for improvements in testing the strength of wire for telegraphic and other purposes. The invention consisted of two drums, g and i; the wire from a reel was carried to drum i, and coiled several times round it, and was then carried to drum g, which was driven at a higher surface

speed than drum i. The alleged infringement consisted in the use of two drums and the passing of wire over them, so as to take the kinks out, the second drum being retarded by a clip so as not to go as fast as the first; the wire pulled round the second drum being gathered up on the first. The defendant had used this method before the date of the plaintiff's patent, but not for the purpose of testing the strength :-Held, that there was no infringement. Blackburn, J.: "Inasmuch as the front wheel which gathers up the defendant's wire (which must necessarily be subjected to strain and to expansion) must gather up a greater length of wire than that which travels over the other drum behind, your front wheel must travel quicker than your second, which is true, and it is said that any means by which you retard the other wheel which receives the wire first is a mechanical equivalent' for the machinery in the plaintiff's machine, by which it was secured that the first should travel quicker than the second. That phrase, ⚫ mechanical equivalent,' according to my experience in patent cases, is always used when a man intends to disguise something else which he cannot clearly express in any other way. But I do not think that this can be said in any sense to be a mechanical equivalent. In the one case the relative motion of the wheels is the cause of the wire expanding instead of being the effect." (Griff. 138.) (4) THORN v. WORTHING SKATING RINK COMPANY. M. R. [1876]

Jessel, M.R., in delivering judgment, said: "The question I have to decide is, whether the defendant's skate is, in substance, an infringement of the plaintiff's. I take it this is the first test. Is it so like the patented thing that your mind is not directed in the first instance to dissimilarity, but to similarity? In other words, have you to examine it very carefully to find any distinction or difference? If that is the real position of the matter, primâ facie it is an infringement; not necessarily so, because you may, on examination, find that what you had overlooked in the first instance was really so essential and important a part of the invention, that you ought to decide at once that it is not an infringement. Then, having arrived at that conclusion on the inspection, the next thing is to see what really has been done. In one sense, what has been done is undoubtedly a mechanical equivalent; but whether it is a mechanical equivalent in the sense in which that expression is used in patent law is, of course, the question I have to decide." (L. R., 6 Ch. D. 417 (n).)

(r) CLARK v. ADIE (First App.). H. L. [1877]

Lord Hatherley: "The case of Seed v. Higgins (8 H. L. Cas. 550) is one which I have always thought exceedingly illustrative of the great difficulty which patentees are put to. . . . There the plaintiff was put to this extraordinary difficulty: He first claimed an improvement by using centrifugal force in the winding of bobbins. He then found that, having been anticipated as to the use of centrifugal force, he

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could only claim in respect of a certain weight, which was moved by centrifugal force in a given position, and he disclaimed all but that weight. When another person sought to substitute what was a mechanical equivalent for the weight (it was not applied in exactly the same place or the same position, but the effects were almost the same), the Court came to the conclusion that the very disclaimer itself showed that the plaintiff was only claiming the exact thing which was left open to him by the numerous other patents which had been taken out for the application of centrifugal force; and that, although the defendant had come as near as could be conceived to infringement, yet he had not actually violated or infringed the patent, because the patent must be confined very strictly to what was expressed in it-that is to say, very strictly to the application of the weight there mentioned." (L. R., 2 App. Cas. 332.)

(8) FLOWER v. LLOYD. C. A. [1877]

Action for the infringement of a patent for improvements in the method and process of printing on tin plates, and in furnaces or ovens for heating or drying printed tin plates. It was contended for the plaintiffs that the specification claimed a combination of four processes, old in themselves, but from which a marketable product was for the first time obtained. The combination was said to consist of (1) printing from raised surfaces with heat-resisting inks; (2) drying in an oven of a particular kind; (3) varnishing; and (4) final heating. The defendants were charged with employing three of these processes and making only a colourable imitation of the fourth. The defendants alleged that the plaintiff's patent was not for a combination, but for a dry process of printing, whereas they had employed the old and well-known process of printing from damp lithographic stones. It was also shown that although, as a last step in the manufacture, they varnished the tin plates and put them again into an oven, this oven was not the plaintiff's improved oven or anything like it :-Held, reversing the judgment of V.-C. Bacon (W. N. 1877, p. 71), that in order to constitute an infringement of a patent for a combination there must be an infringement of the whole combination, not in the sense that every step of the combination must be adopted, but that there must be an adoption of that which constitutes the essence of the combination. In this case the process of the defendants differed from that of the plaintiffs in every step, except that, after the plates had been printed and baked, they varnished them and replaced them in an oven, but in an oven of a different construction from that employed by the plaintiffs. Moreover, that this was a well-known process which could not,

a fair construction of the plaintiff's specification, be considered as any part of what constituted the essence of the combination protected thereby. (W. N. 1877, p. 132; Johnson's P. M., 4th ed., p. 245.) The plaintiffs afterwards tried to set aside the judgment on the ground that the defendants had fraudulently