2. A positive statute, unrepealed, can never be repealed by non-user alone. 4 Yeates, Rep. 181; Id. 215; 1 Browne's Rep. Appx. 28; 13 Serg. & Rawle, 447. The disuse of a law is at most only presumptive evidence that society has consented to such a repeal; however this presumption may operate on an unwritten law, it cannot in general act upon one which remains as a legislative act on the statute book, because no presumption can set aside a certainty. A written law may indeed become obsolete when the object to which it was intended to apply, or the occasion for which it was enacted, no longer exists. 1 P. A. Browne's R. App. 28. "It must be a very strong case," says Chief Justice Tilghman, "to justify the court in deciding, that an act standing on the statute book, unrepealed, is obsolete and invalid. I will not say that such case may not exist-where there has been a non-user for a great number of years-where, from a change of times and manners, an ancient sleeping statute would do great mischief, if suddenly brought into action-where a long, practice inconsistent with it has prevailed, and, specially, where from other and latter statutes it might be inferred that in the apprehension of the legislature, the old one was not in force." 13 Serg. & Rawle, 452; Rutherf. Inst. B. 2, c. 6, s. 19; Merl. Repert. mot Desuetude.