it covers some of the advantages mentioned; in such a case it may still no doubt be a good patent.'

Vague, speculative claims to be avoided.-A patentee will not be allowed to make wide hypothetical or speculative claims based on mere conjecture or surmise, nor will his patent be permitted to cover matters of which he was ignorant at the date of his patent. In the specification under a patent for improvements in machinery for raising water, the patentee said, 'If any gases or elastic media other than atmospheric air are used, with which to charge the case [part of the machinery], I claim the sole right to do so.' Pollock, C. B., who tried an action brought for infringing this patent (Tetley v. Easton, Macr. P. C. 48), remarked upon this passage, that, in point of law, the patentee had no right to make such a claim; the law would not permit a patentee to claim more than he has invented. 'It will permit him to claim that which he has invented by means of successful experiments or otherwise, and which he has given to the public, but not that which is the mere subject of his speculation or imagination, or of his endeavouring to grasp more than he is entitled to. I think we are bound to give, as far as possible, the fullest effect to an invention; but, on the other hand, I think we are also bound to oppose the endeavours to make a patent grasp at and embrace a number of matters that were never in the head of the inventor.'

In another part of the specification, the patentee described a wheel with straight arms, and then he said, I propose to construct the wheel of every variety of configuration, so long as it is constructed with a channel in the interior.' The defendant had made use of a wheel with bent arms, and the patentee treated this as an infringement, although he admitted that at the time he obtained his patent he had never thought of bent arms, and also that curved arms almost trebled the effect of the machine. The judge told the jury that the patentee's claim to every shape of arm would not stand. To hold that it was good would be to reward a man who had rashly and ignorantly

taken out a patent on a subject he had not appreciated. The same learned judge, when presiding at the trial of Stevens v. Keating (2 W. P. C. 184)-an action for infringing a patent for processes for combining materials to form cements-said, with reference to that part of the specification which was held to claim the use, not only of a particular acid, but of all acids which might succeed, that no patentee could be allowed to make such a claim, and to say, Whereas other substances will succeed, I claim them all.

A perusal of these cases will show that it is safer for a patentee to restrict his claim to the use of those processes, or those materials, which he has found by actual trial to answer the purpose, than to extend it to matters of which he has no accurate knowledge; since, in doing this, he may either claim something which will not answer the object in view, something which is not new, or something which he does not sufficiently describe. The law will aid him, without any general claim in his specification, in repressing infringements which are an illegal imitation of his process behind a colourable variation, or by means of mechanical or chemical equivalents.

The safest course for patentees to adopt' (said Pollock, C. B., to the jury on the trial of Crossley v. Potter, Macr. P. C. 256) in framing their specifications is, instead of including everything, to confine themselves specifically to one good thing, and a jury will always take care that if that be a real invention, no man under colour of improvement shall be allowed to interfere with that which is the offspring of their genius.'

In the case of Arnold v. Bradbury (L. R. 6 Ch. 706) Lord Hatherley, C., said that a claim must be very large and vague indeed to justify any court in saying, independently of evidence, that it is impossible to sustain a patent based upon it. In that case he decided that the claims for making ruffles by machinery' meant by the described machinery, and that there was no ground for holding that the claims were too large per se. In the course of his

judgment, he remarked that it was a singular fact that no case had been cited from the law books of any claim being held to be too large on account of the greatness of the claim independently of external evidence. But he referred to an American case (Wyatt v. Stone, 1 Storey 273) where the patentee had claimed every method of cutting ice by machinery.

CHAPTER X.

ON THE INTERPRETATION OF SPECIFICATIONS.

FORMERLY there was a disposition in the Courts to take part against patentees, under the impression that monopolies were not to be encouraged, attaching the old odious sense of the term to the phrase indicating a patent privilege for an invention. The judges were then astute to detect flaws in specifications, to the language of which they were accustomed to apply a rigorous criticism. Then came a change, and some of the judges thought that a specification ought to be read with indulgence; that a liberal construction should be put upon it, and that the words should receive a benign or a benevolent interpretation. But of late years the Courts have laid down that specifications are to be construed like other written documents, that is, with a disposition to read them fairly, and with an endeavour to ascertain their real meaning, not straining the language nor giving effect to petty objections. In the case of Newton v. Halbard (Hil. Term, 1872) Mr. Justice Grove said, 'A specification should not be construed in a technical or captious spirit, but with a fair intention to give it effect if it be reasonably intelligible.' In the case of Harrison v. The Anderston Foundry Company (L. R. 1 App. Cas. 574) Lord Chelmsford said, 'In the construction of a specification it appears to me that it ought not to be subjected to what has been called a benign interpretation, or to a strict one. The language should be construed according to its ordinary meaning, the understanding of technical words being, of course, confined to those who are conversant with the subject-matter of the invention.' 'I am

anxious' (said Sir G. Jessel, M. R., in Hinks v. Safety Lighting Company, L. R. 4 Ch. D. 607), ' as I believe every judge is who knows anything of patent law, to support honest bonâ-fide inventors who have actually invented something novel and useful, and to prevent their patents from being overturned on mere technical objections or on mere cavillings with the language of the specification, so as to deprive the inventor of the benefit of his invention. This is sometimes called a "benevolent" mode of construction. Perhaps that is not the best term to use, but it may be described as construing a specification fairly, with a judicial anxiety to support a really useful invention, if it can be supported on a reasonable construction of the patent.' See also the remarks of the same learned judge, and of Brett, L. J., in Plimpton v. Spiller (L. R. 6 Ch. D. 412). Also the observations of Sir G. Jessel, M. R., in Otto v. Linford (Court of App. 46 L. T. N. s. 35). In Dudgeon v. Thomson (L. R. 3 App. Cas. 53), Lord Blackburn said, 'I apprehend the duty of the Court is fairly and truly to construe the specification, neither favouring the one side nor the other; neither putting an unfair gloss or construction upon the specification for the purpose of saving a patent, nor in order to extend it.'

The same learned judge, in Clark v. Adie (L. R. 2 App. Cas. 423), said, 'In construing the specification we must construe it like all written documents, taking the words and seeing what is the meaning of those words when applied to the subject-matter; and in the case of a specification which is addressed, not to the world at large, but to a particular class, namely, skilled mechanicians possessing a certain amount of knowledge, it is material for the tribunal to put itself in the position of such a class, . . . and by the admission of evidence or otherwise put itself in a position to understand and then to say what the words of the specification mean when applied to such a subject-matter.' In delivering the judgment of the Court of Appeal in the same case (L. R. 3 Ch. D. 142), L. J. James said, 'It cannot be effectually contended that there is any principle to be applied