This reminds me a joke about two scientists who have to spend a night in a room in the house of a poor man. In the middle of the room there is a stove and under the stove are four big stones serving as four long legs that the stove is nearly one meter above the floor. The scientists begin to think to find out the reason of which should be for about the strange position of the stove. One says, " I think it is probably because of obtaining the most effective circulation of heated air", and the other says, "I think it is likely because of obtaining sustainable burning progress." As they disagree with each other they think the best is asking it to the poor man. The poor man says," it is simply because of lack of stovepipe."

Is there a joke about valves too? Or have I told it in the past?