[124] If this be the proper conclusion in plain cases, further consequences ensue. Facts do not often exactly repeat themselves in practice; but cases with comparatively small variations from each other do. A judge who has long sat at nisi prius ought gradually to acquire a fund of experience which enables him to represent the common sense of the community in ordinary instances far better than an average jury. He should be able to lead and to instruct them in detail, even where he thinks it desirable, on the whole, to take their opinion. Furthermore, the sphere in which he is able to rule without taking their opinion at all should be continually growing. It has often been said, that negligence is pure matter of fact, or that, after the court has declared the evidence to be such that negligence may be inferred from it, the jury are always to decide whether the inference shall be drawn. /1/ But it is believed that the courts, when they lay down this broad proposition, are thinking of cases where the conduct to be passed upon is not proved directly, and the main or only question is what that conduct was, not what standard shall be applied to it after it is established. Most cases which go to the jury on a ruling that there is evidence from which they may find negligence, do not go to them principally on account of a doubt as to the standard, but of a doubt as to the conduct. Take the case where the fact in proof is an event such as the dropping of a brick from a railway bridge over a highway upon the plaintiff, the fact must be inferred that the dropping was [125] due, not to a sudden operation of weather, but to a gradual falling out of repair which it was physically possible for the defendant to have prevented, before there can be any question as to the standard of conduct. /1/ So, in the case of a barrel falling from a warehouse window, it must be found that the defendant or his servants were in charge of it, before any question of standard can arise. /2/ It will be seen that in each of these well-known cases the court assumed a rule which would make the defendant liable if his conduct was such as the evidence tended to prove. When there is no question as to the conduct established by the evidence, as in the case of a collision between two trains belonging to the same company, the jury have, sometimes at least, been told in effect that, if they believed the evidence, the defendant was liable. /3/