Still, in a more limited way, the same principle applies to knowledge that applies to foresight. It is enough that such circumstances were actually known as would have led a man of common understanding to infer from them the rest of the group making up the present state of things. For instance, if a workman on a house-top at mid-day knows that the space below him is a street in a great city, he knows facts from which a man of common understanding would infer that there were people passing below. He is therefore bound to draw that inference, or, in other words, is chargeable with knowledge of that fact also, whether he draws the inference or not. If then, he throws down a heavy beam into the street, he does an act [56] which a person of ordinary prudence would foresee is likely to cause death, or grievous bodily harm, and he is dealt with as if he foresaw it, whether he does so in fact or not. If a death is caused by the act, he is guilty of murder. /1/ But if the workman has reasonable cause to believe that the space below is a private yard from which every one is excluded, and which is used as a rubbish heap, his act is not blameworthy, and the homicide is a mere misadventure. To make an act which causes death murder, then, the actor ought, on principle, to know, or have notice of the facts which make the act dangerous. There are certain exceptions to this principle which will be stated presently, but they have less application to murder than to some smaller statutory crimes. The general rule prevails for the most part in murder.