5. The limits of time during which tradition can be considered as a sufficiently accurate medium for preserving the memory of events, may be put generally at from one hundred to one hundred and twenty years. Within this period careful investigation and inquiry will enable the historian to report the main features of events with substantial truth, from the testimony of those who were contemporaries, or who derived their information from those who were. Beyond this period, when the knowledge of occurrences has to pass through three or four media of transmission, tradition becomes an uncertain and untrustworthy informant, and after the lapse of a greater interval, it is utterly unreliable, affording no means of checking the introduction of legendary narratives. There may be a few exceptional cases which have impressed themselves deeply on the public recollection. Occasionally the protracted lives of a few individuals may lengthen the period of trustworthy transmission, but this is an event of such rare occurrence as but slightly to modify the general rule. It must be observed that there are two cases in which the traditional knowledge of events is transmitted with far more accuracy, and over far longer intervals of time than in ordinary ones, viz., those of families which have an historical importance derived from the actions of their ancestors, and those of bodies of men who have a kind of corporate life, succeeding one another in unbroken succession, especially when this corporate life is founded on the events themselves. This latter case presents the means best adapted for the traditionary transmission of facts, and one in which it is hardly possible that they should fail of being accurately transmitted within a reasonable interval of time. This was precisely the position occupied by the Christian Church during the first century of its existence respecting the chief events in the life of its founder.