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for an improved machine or apparatus for treating or preparing meal. The specification stated that the squeezing rolls of the improved machine were to have

a surface consisting of a material containing so much silica as not to colour the meal or flour,' and the patentee preferred to make them of iron coated with china,' and finely turned with diamond tools. It was shown that there are two kinds of china-Oriental or Chinese china, which contains 73 per cent. of silica, and is very hard; whilst the china usually made in this country contains only about 40 per cent. of silica, and is much softer. Now the first kind of china would answer the purpose, but the second would not. It was therefore held by the Court of Appeal, confirming the decision of the court below, that although the invention was useful in milling operations, the specification was ambiguous and inadequate, as it did not state what kind of china was to be employed. Experiments would have been required to discover a suitable material for the apparatus.

A specification will be construed with reference to the state of knowledge at the time it was prepared. Thus, the specification under a patent for a chemical invention will be held to refer to what was known at the time, and not to anything which was discovered subsequently. The language will not be deemed too wide because it is extensive enough to embrace unsuitable ingredients of later discovery. As a patentee would not be allowed to secure the exclusive use of materials unknown at the date of the patent, although the words of the specification are sufficiently ample to cover them, it would be manifestly unjust to hold that his language, having become applicable by the advance of knowledge to more than he contemplated, should render the patent void, if it was properly limited and accurate at the time it was employed. An inven

tion may be superseded by the progress of discovery, but the specification will not be thereby rendered invalid. (Badische Anilin und Soda Fabrik v. Levinstein, L. R. 24 Ch. D. p. 156. And see Crossley v. Beverley, 3 C. & P. 515.)

It is not obligatory on a patentee, when referring to materials and ingredients to be used in carrying his invention into effect, to enter into minute details as to such materials and ingredients, if they are known in the shops, and can be readily purchased under the names which he gives them (Mackintosh v. Everington, 2 Carp. Rep. 191).

The names of articles mentioned in a specification must be taken to be used in their ordinary commercial sense. Thus, a direction in a specification to use dry arsenic acid in the manufacture of dyes was held to refer to the ordinary arsenic acid of commerce (which is dry to the touch, although it contains water in combination), not to anhydrous arsenic acid, which could not be commonly bought in the trade, and which would not answer the purpose. (Simpson v. Holliday, 20 Newt. Lon. J. 118; 5 N. R. 340; I.. R. 1 H. L. C. 315). And see Sturtz v. De la Rue, 1 W. P. C. 83 N.; Stevens v. Keating, 2 W. P. C. 183, 187; Muntz v. Foster, 2 W. P. C. 104.

A person who takes out a patent for an invention consisting of the use of known materials in new proportions, though bound to state the most suitable proportions within his knowledge, is not bound to limit his claim to the precise proportions recommended by him in his specification. (The Patent Type Founding Company v. Richard, Johns. 381.)

Whether or not a specification describes with sufficient accuracy the material out of which an article is to be made, is a question for the jury, where the case is tried before one. (Bickford v. Skewes, 1 W.

K

P. C. 214; Derosne v. Fairie, 1 W. P. C. 154; Elliot v. Turner, 2 C. B. 446; Wallington v. Dule, 7 Ex. 888.)

Must communicate the latest information.

It frequently occurs that in the interval between the application and the lodging of the complete specification, the inventor discovers that the original invention is capable of material improvement. The intervening period is allowed him for the very purpose of improving the details of his invention; and if he fails to communicate to the public the best information he possesses at the time of lodging the complete specification, the patent will be held void. In Crossley v. Beverley (1 W. P. C. 117) it was objected that the patentee had added something to the invention as finally specified, but, said Bayley, J., I think that if between taking out the patent and filing the specification, the inventor makes a discovery which will enable it better to effectuate the thing for which the patent was obtained, not only is he at liberty to introduce them into his patent, but it is his bounden duty so to do, and it is not sufficient for him to communicate to the public the knowledge he has obtained before the specification.' It must, however, be understood that the additions must strictly relate to the invention as it stood at the date of the application. The introduction of new heads into the specification or an extension of the subject-matter of the original invention will not be permitted. Crossley v. Potter (Macr. P. C. 240.) Bailey v. Roberton (L. R. 3 App. Ca. 1055). complete specification, said Lord Chelmsford in Penn v. Bibby (L. R. 2 Ch. D. 58) is in a sense supplemental to the provisional specification, not going beyond nor varying from it as to the nature of the invention, but conveying additional information which may have been

The

acquired during the currency of the provisional specification as to the manner in which the invention is to be performed.'

Must describe the best method of operating.

A patentee is bound to describe the most advantageous method within bis knowledge for carrying his invention into effect; and he ought to put the public in possession of his secret in as ample and beneficial a way as he himself uses it. In Wood v. Zimmer (Holt, N. P. 57) a patent for a method of making verdigris was contested. It seemed that verdigris was made by the process set forth in the specification; but that the patentee was in the habit of secretly putting aquafortis into the boiler. The copper, forming one of the ingredients, was thereby more rapidly dissolved; but the verdigris produced was neither better nor cheaper than that made according to the specification. Gibbs, C. J., considered however, that this was a prejudicial concealment, and held the patent to be invalid.

Letters patent were obtained for a mode of making a medicine, composed of three salts, commonly sold in the shops under certain well-known names. The specification, instead of describing these salts by their names, described the processes by which they were produced, and then pointed out the proportions in which the salts were to be combined in order to form the medicine the subject of the patent. The methods of producing the separate salts were not essential to the combination, and formed no part of the invention. It was held at Nisi Prius that the specification was bad, Abbott, C. J., saying that it is the duty of any one to whom a patent is granted to point out in his specification the plainest and most easy way of producing that for which he claims a monopoly; and to make the

public acquainted with the mode which he himself adopts. If a person would be led to suppose a laborious process necessary to the production of any one of the ingredients, when in fact he might go to a chemist's shop and buy the same thing as a separate simple part of the compound, the public are misled. Price, 1 Ry. and Moo. 1; 1 W. P. C. 83.)

(Savory v.

There are many other cases which show that if the patentee knows of any circumstance which conduces to the advantage of his manufacture or process, he is bound to mention it in his specification. Nothing of importance can be withheld or concealed without danger to the patent. In Turner v. Winter (1 W. P. C. 81). Buller, J., said, that if the patentee make the article for which the patent is granted of cheaper materials than those which he has enumerated, although the latter may answer the purpose equally well, the patent is void, because he does not put the public in possession of his invention, or enable them to derive the same benefit as he himself does.

If a patentee is acquainted with any particular mode by which his invention may be most conveniently carried into effect, he ought to state it in his specification. Per Alderson, B., in Morgan v. Seward (1 W. P. C. 170.)

In Sturtz v. De la Rue (1 Carp. Rep. 463, 5 Russ. 322, 1 W. P. C. 83), it appeared that the patentee had mentioned in his specification a certain substance, under the name of the finest and purest chemical white lead, which was to be used in giving paper a glaze, preparatory to its receiving an impression from an engraved plate. He himself imported from Germany, for this purpose, a preparation called Kremnitz white; but he said nothing about this in his specification. It was shown that there was no article known in the chemists' shops in London which answered to the patentee's