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 180 Patents. [Ch.X. Sec.IL cification direct the thing to be produced several ways, or by several different ingredients, and any one of them fail {a). So, if the thing could only be made with two or three ingredients specified, and the patentee has inserted others which will not answer the purpose, that will avoid the patent {b). As stated by Sir V. Gibbs, in Bovill v, Moore (c), " another con- sideration respecting the specification, which is also a material one, is, whether the patentee has given a full specification of his invention, not only one that will enable a workman to con- struct a machine answering to the patent, but one that will enable a workman to construct a machine answerable to the patent, to the extent most beneficial within the knowledge of the patentee at the time ; for a patentee who has invented a ma- chine useful to the public, and can construct it in one way more extensive in its benefits than in another, and states in his speci- fication only that mode which would be least beneficial, reserv- ing to himself the more beneficial mode of practising it, al- though he will have so far answered the patent, as to describe in his specification a machine to which the patent extends ; yet he will not have satisfied the law, by communicating to the public the most beneficial mode he was then possessed of, for exercising the privilege granted to him." As if the prosecu- tion of a manufacture be assisted in a lace machine, by bend- ing together two of the teeth of the dividers, or making one Ipnger than the rest, if it appear to have been a subsequent dis- covery, it will not break in upon the validity of a patent, it will only shew that the patentee has since found out the means of carrying on his own invention to better effect (d); but if at the time when he obtained his patent, he was apprized of this more beneficial mode of working, and did not by his specification communicate this more beneficial mode of working to the pub- lic, that will have been a fraudulent concealment from the pub- lic, and will render the patent void (e). So, if the patentee make the article with cheaper materials than those which he has enumerated, although the latter will 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 (a) 1 T. R. 602. (rf) Davies on Patents, 3S1. Sir V. (b) 1 Ibid. 607. Gibbs in Bovill v, Moore. (c)AtN. P. Davies, 400. luC.P. (e) Ibid. 401. J2 Marshall, 211. ^ the