But there is one way in which the analogy between scientific and social progress will be noteworthy. It is a commonplace of industrial history that an improvement in one machine, or the introduction of some novel method of applying power, always produces, and may very often necessitate, modifications in a number of procedures not previously seen to be connected with it: and great results from little causes flow. No one foresaw, when Mr Edison discovered the differences in the electrical conductivity of carbon induced by slight variations of pressure--a discovery at first utilised only in the micro-tasimeter, the appliance used for measuring small changes in the size of objects submitted to it--that the same discovery would presently render commercially practicable the electrical transmission of speech and numerous other conveniences, themselves the progenitors of fresh inventions now in constant use. Similarly, political and social changes quite easy to foresee will undoubtedly have effects which in their entirety no one can possibly foresee. The rate of advancement cannot be calculated like a geometrical progression: all that we can hope to do is to realise more or less vaguely the acceleration which the action and interaction of anticipated (and often antagonistic) forces will produce; the general manner of the world's progress representing the resultant of their activities. What we must constantly keep in mind is the fact that changes in the institutions of society can only be stable when they are the result of corresponding changes in the temper of the age which yields them. As this temper is a thing of gradual development, we must believe that many temporary expedients will have to be tolerated by advanced thinkers since (as Spencer remarks) society can only be held together when the institutions existing, and the conceptions generally current, are in tolerable harmony. We can foresee many changes which will be in beneficent existence a hundred years hence; but it would be irrational to show impatience because these changes cannot be immediately proposed; since, being not yet in harmony with the current conceptions of the world, their immediate adoption would be mischievous instead of beneficial, and their results anarchic instead of stable. For a great many years we must go on passing laws for the regulation of social life, which we can quite easily perceive that the altered social life of a future age will not need, because they would be injurious to it. The zealous reformer who wishes, as we must all wish, to help the world in its wearied way to perfection must aim rather to assist the mind of people to demand greater reforms than it could as yet assimilate, than to procure the arrival of reforms for which society is not yet ripe, and must be content with the effort "... to ease the burden of the world Laboriously tracing what must be And what may yet be better."