There was a man whose wife is about to deliver a child. He wanted a Boy child & he was quite confident that she will deliver only Boy child. So he went along with his wife to his in-laws place & stayed there. He stayed there for more that 15 days, but she didn`t deliver the child at all. So he went back to his place. Before leaving he told his father in law that when she delivers the child just call up & tell me that "the clock has arrived" & that is the code word to understand that boy is born.
Next day she delivered a girl child. The father in law didn`t know how to inform his son in law. He can`t say that the Clock hasn`t arrived also. So he calles up & said, "The Clock has arrived but the pendulum is missing"