"The old order changeth yielding place to the new. And God fulfils Himself in many ways Lest one good custom should corrupt the world." --Tennyson, Alfred, _The Passing of Arthur_. The conception of social change as used in this monograph also needs definition. By social change is meant those rapid mutations which accompany sudden interferences with the equilibrium of society, break up the _status-quo_, dissipate mental inertia and overturn other tendencies resistant to structural modification. The various forces which initiate such disturbances are factors in social change. These factors may be intra-social,--within the group--such factors as operate in the regular social process, imitation and adaptation, for example; or they may be extra-social, "stimuli" factors--from without the group--such as, accidental, extraneous or dramatic events. Of the latter conquest may be one, or the sudden intrusion of a foreign element, or rapid changes of environment.[4] [4] Ross, Edward A., _Foundations of Sociology_ (N. Y., 1905), ch. viii, p. 189. These sudden changes are fully worthy of careful study by scientific method. However important the accumulation of impulses toward social transformation may be, there is often a single "precipitating factor" which acts as the "igniting spark" or "the knocking away of the stay-block," or "the turning of a lever."[5] It is among such extra-social or "stimuli" factors that catastrophe falls as a precipitating agent in social change. [5] Ross, _op. cit._, p. 198.