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 Ch.X.Sec.IL] Patents, 187 the same benefit which he himself does {a). In a case before Lord Mansfield, for infringing a patent for steel trusses, it ap- peared, that the patentee in tempering the steel, rubbed it with tallow, which was of some use in the operation, and because this was omitted, the specification was held to be insufficient, and the patent was avoided (6). And in a recent case, the wilful omission to state an article, which, though it was not necessary to the composition of the manufacture, produced it more expeditiously, was held to vacate the grant (c). In short, the exact nature, and the mode of conducting the processes, and the times they are to be continued, should be accurately stated, and specifically pointed out {d). It is not necessary to set forth a model or drawing, illustra- tive of the invention described in the specification {e) : but it is usual and perhaps advisable so to do. It should be drawn on a scale, especially where relative sizes or distances are im- portant {/). The general rule however seems to be, that the specification must contain within itself the necessary informa- tion, and should not refer to other distinct instruments or books, &c. for particulars (g). But in Harmar v. Playne {k a patent for improvements upon a former machine was held good, although the specification described the whole machine, without distinguishing the improvements from the part of the whole machine or referring to the former specification, other- wise than as the second patent recited the first. Care must also be taken that the denomination or title of the invention in the patent is not more or less extensive, and does not vary from that mentioned in the specification. The lan- guage of the patent as was observed in a late case (/), may be explained and reduced to a certainty by the specifica- tion; but the patent should not represent the party to be the inventor of one thing, and the specification shew him to be the inventor of another ; because, perhaps, if he had represented himself as the inventor of that other, it might have been well known that the thing was of no use, or was in common use, (a) 1 Term R, 607. and 1 Holt, R. (/) Hands on Patents, 11, N. P. 60. (A) 1 Term, 608. (c) Holt's Rep. N. P. 58. (H) 2 Barncw and Aid. 345. («) Se€ 2 Hen. Bla. 463. (g) Harmar u. Playne, 11 East, 112, 3. 1 Ves. and B. 67. (h) 11 East, 101. (i) 2 Barnew and Aid. 350, 1. and