The curious notion that the need-fire cannot kindle if any other fire remains alight in the neighbourhood seems to imply that fire is conceived as a unity which is broken up into fractions and consequently weakened in exact proportion to the number of places where it burns; hence in order to obtain it at full strength you must light it only at a single point, for then the flame will burst out with a concentrated energy derived from the tributary fires which burned on all the extinguished hearths of the country. So in a modern city if all the gas were turned off simultaneously at all the burners but one, the flame would no doubt blaze at that one burner with a fierceness such as no single burner could shew when all are burning at the same time. The analogy may help us to understand the process of reasoning which leads the peasantry to insist on the extinction of all common fires when the need-fire is about to be kindled. Perhaps, too, it may partly explain that ceremonial extinction of all old fires on other occasions which is often required by custom as a preliminary to the lighting of a new and sacred fire.[740] We have seen that in the Highlands of Scotland all common fires were extinguished on the Eve of May-day as a preparation for kindling the Beltane bonfire by friction next morning;[741] and no doubt the reason for the extinction was the same as in the case of the need-fire. Indeed we may assume with a fair degree of probability that the need-fire was the parent of the periodic fire-festivals; at first invoked only at irregular intervals to cure certain evils as they occurred, the powerful virtue of fire was afterwards employed at regular intervals to prevent the occurrence of the same evils as well as to remedy such as had actually arisen. [The needfire among the Iroquois of North America.]