in advance, if desired, and in some instances, when selling a foreign patent dependent for its existence on the continuance of the English patent, the purchaser requires that the English annual taxes shall be paid up in full.

If, by accident, mistake, or inadvertence an inventor fails in the payment of any of these taxes as they become due, the Comptroller, on its being proved to his satisfaction that the omission was unintentional, may grant a prolongation of the time for paying the tax-not exceeding three months—an additional penalty being imposed, however, in such cases of £1 10s. for one month's extension, or £3 10s. for two months', or £5 10s. for three months', including costs. The patentee is debarred from obtaining damages for infringements committed within such prolonged time, and prior to the actual payment of the tax.

PROLONGATION.

At the expiration of fourteen years from the date of application, the invention becomes public property, unless the inventor can obtain a prolongation of his patent from the Judicial Committee of the Privy Council. This can sometimes be obtained if the invention be a very important one, and the inventor has used due exertion in working it, has not received a fair and reasonable profit for its use, and still has an interest in the patent.

The application has, however, to be made at least six months before the expiration of the period for which the patent was granted, and must be duly advertised, and the applicant must be prepared with elaborate statements of accounts and proof of their correctness. Any profits obtained by the applicant on foreign patents for the same invention should also be

set forth. Any interested party can oppose the grant of such extension, and the Privy Council has power to grant costs to either party. The cost of this application is usually considerable, even in unopposed cases, amounting to from £300 to £400.

DISCLAIMERS AND AMENDMENTS.

It very frequently happens that something has been claimed in the specification that was unpatentable, or without utility, or utterly unworkable, or which was in public use, or published in this country before the date of application; or there is some error, obscurity, or want of sufficient information in the specification that would make it difficult or impossible for an ordinary workman of the trade to which the invention relates to manufacture from the description alone.

Such a defect makes the whole patent null and void at law. When, therefore, a patentee finds such a flaw, he should immediately apply for leave to amend his specification, including, if necessary, the drawings forming part thereof, by way of disclaimer, correction, or explanation, stating the nature of such amendment and his reasons for the same.

The request and the nature of such proposed amendment must then be duly advertised in the prescribed manner, and at any time within one month from its first advertisement any interested person may give notice at the Patent Office of opposition to the amendments.

Where such notice is given, the Comptroller gives notice of the opposition to the person making the request, and he hears both parties (or if there be no opposition he examines the documents, and if necessary he hears the applicant), and then decrees whether, and subject to what conditions, if any, the amendment

shall be allowed, subject to an appeal to the Law Officer.

The Law Officer, when appealed to, hears the applicant and opponent, if any, if in his opinion the latter be entitled to be heard in opposition, and ratifies, alters, or reverses the decision of the Comptroller as he may consider just, with or without costs.

If the appeal be by an unopposed applicant against the decision of the Comptroller, the Law Officer hears both the applicant and the Comptroller, and from his decision there is no appeal.

In case of a disclaimer the judge cannot grant damages for infringements prior to the date of the disclaimer unless he is satisfied that the original specification was drawn "in good faith and with reasonable skill and knowledge," and it is very rarely that a judge is satisfied of this when a disclaimer has been made.

No amendment can be allowed that would make the specification, as amended, claim an invention. substantially larger than or substantially different from the invention claimed by the specification as it stood before amendment.

An amendment, too, which will reduce a patent from a large field of invention down to some insignificant detail in that field is generally refused. Thus where a man claimed an improved process of and apparatus for canning meats, and it was shown that the entire apparatus and process was old except a special arrangement of lid, a patent was refused for the latter though a new part of the original invention.

Leave to amend is conclusive as to the right of the party to make the amendment allowed, except in case of fraud; and the amendment, in all courts and for all purposes, is deemed to form part of the specification.

The foregoing provisions for disclaiming do not

apply when and so long as any action for infringement or other legal proceeding in relation to a patent is pending.

In an action for infringement of a patent, and in a proceeding for revocation of a patent, the court or a judge may order that the patentee shall, subject to such terms as to costs and otherwise as the court or a judge may impose, be allowed to disclaim for the purpose of such action any part of the invention specified in such order, and give the disclaimer in evidence.

This clause is, however, of little use, as the judges almost invariably make it a condition of allowing the disclaimer that all the costs of the action up to that date be paid by the patentee. As, too, the disclaimer is restricted in this case to the actual matter at issue, it is generally best, if a disclaimer be necessary, to abandon the action, pay the costs, make the disclaimer, and commence a fresh action.

Cost of amendment (unopposed) is usually about £13.

PRINTED COPIES.

Printed copies of the specifications and drawings (with disclaimers if there be any) of all British patents still in force (but not of abandoned provisional specifications of later date than 1883) can be obtained at is. each, including postage. Copies of all patents were formerly kept in stock, but latterly all but a limited number of copies of each specification were ordered to be destroyed; and now it is impossible to obtain printed copies of many of the early patents, especially those that are of value and in demand, except by ordering six copies, in which case the Government will usually reprint and supply them in a few days' time.

COMPULSORY LICENSES.

It having been found that many patents taken out in this country by foreigners, were held without being worked to the great disadvantage of English trade (the patented invention being made abroad and imported), it has been enacted :

(1) Any person interested can petition the Board of Trade, alleging that the reasonable requirements of the public with respect to a patented invention have not been satisfied, and praying for the grant of a compulsory license, or in the alternative the revocation of the patent.

(2) The Board of Trade shall consider the petition, and if the parties cannot come to an arrangement between themselves, it shall, if satisfied that a reasonable case has been made out, refer the petition to the Judicial Committee of the Privy Council, or, if satisfied that there is no reasonable case, dismiss the petition.

(3) The Judicial Committee (a most expensive Court), after hearing the parties, can order the patentee to grant licenses on such terms as they may consider just, or, if convinced that this will not satisfy the reasonable demands of the public, can revoke the patent altogether. If, in hearing the petition, it be proved that the patent is worked, or the patented article manufactured, wholly or mainly outside the United Kingdom, this will be taken into consideration against the patentee, and the onus will rest with the latter to prove that the reasonable requirements of the public have been satisfied, or an order for a compulsory license or for a revocation of the patent will be made.

(4) But in all cases no order of revocation of a patent can be made within the three years of the date of the patent, or so long as the patentee gives satis