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192 Patents. [Ch.X.Sec.lL patentee's, still, if the defendant has availed himself substanti- ally of the new idea of the plaintiff, however ingeniously the exterior of the production may have been worked up into a different shape, the remedy seems clear (a). The law will not suffer an individual to do indirectly that which it directly forbids* And in ex-parte Fox (5), the Lord Chancellor observed, " If the petitioners have invented certain improvements upon an engine for which a patent had been granted, and those im- provements could not be used without the original engine, at the end of fourteen years the petitioners could make use of a patent taken out upon their improvements, though, before that period expired, they would have no right to make use of the others' substratum^ The remedies are by action at law for damages, or by pro- ceedings in Chancery, Perhaps it is in general advisable as a matter of course to commence proceedings in Chancery with all possible expedition, for an account of the profits made from the illegal use of the invention. An injunction may thereby also be obtained to restrain the party from the further use of the patent right (c) ; but there must be separate bills upon every distinct invasion of the patent (d An action at law to try the validity of the patent is almost invariably directed by the Lord Chancellor. On the trial of the action, the plaintiff must give some general or slight evidence, shewing the nature of the invention and that it produced the effect specified. It is in strictness incumbent on the defendant to falsify the specification (e) ; but it is advisable that the plaintiff should be prepared with the strongest possible evidence in support of the merits of the discovery, and the sufficiency of the specification. Letters patent being under the great seal are matters of record (y), and are therefore read without proof: and by statutes S and 4 Ed. 6. c. 4. and 13 El. c. 6. patentees and all claiming under them, may make title by shewing the exemplification or constat of the roll. These statutes have been held to extend to all the (a) See per Rooke, J. in Boulton v. (d) 2 Ves. Jun. 486. Bull, 2 H. B. 477. Sir V. Gibbs, C. J. (e) 1 Term R. 602. Bovill V. Moore, Davies, 405. (/) 2 Bla. Com. 346. Dr. and StH- (b) 1 Ves. and B. 67. dent, book I. dial. 8. Phillips's Evid. (c) See Mitf. Chancery Pleadings, 173,4. See Bull. N. P. 227. 124. King's