THE PRESIDENTIAL ADDRESS 19 



curves, camber or super-elevation, angles of crossings, bridge stresses. 

 The harmony has been destroyed. Especially may this be the case if 

 the new factor applies to some units only, and not to all, when the 

 potential density of traffic may be actually lessened. The analogy 

 for the social system is obvious, and its form of government matters 

 little for the presence of the problem, though it may be important 

 in the handling of it. 



I have spoken as though the normal span of life of men and 

 machinery themselves provides a phase to which scientific advance 

 might be adjusted for a completely smooth social advance. But 

 this would be to ignore customs and institutions, even as we see 

 in Federal America, Australia and Canada, constitutions which 

 lengthen that phase and make it less amenable as a natural transition. 

 At one time we relied on these to bring about the economic adjust- 

 ment necessary. But technical changes take place so rapidly that such 

 forces work far too slowly to make the required adaptation. Habits 

 and customs are too resistant to change in most national societies 

 to bring about radical institutional changes with rapidity, and we 

 patch with new institutions and rules to alleviate the effects rather 

 than remove the causes of maladjustments. The twenty mile speed 

 limit long outstayed its fitness, and old building restrictions remained 

 to hamper progress. Edison is reported to have said that it takes 

 twenty-five years to get an idea into the American mind. The Webbs 

 have given me a modal period of nineteen years from the time when 

 an idea comes up as a practical proposition from a ' dangerous ' left 

 wing to the date when it is effectively enacted by the moderate or 

 ' safe ' progressive party. This period of political gestation may be a 

 function of human psychology or of social structure. We do not 

 know how ideas from a point of entry, permeate, infiltrate or saturate 

 society, following the analogues of conduction, convection, or lines 

 of magnetic force. 



Our attitude of mind is still to regard change as the exceptional, 

 and rest as the normal. This comes from centuries of tradition and 

 experience, which have given us a tradition that each generation will 

 substantially live amid the conditions governing the lives of its 

 fathers, and transmit those conditions to the succeeding generation. 

 As Whitehead says : ' we are living in the first period of human 

 history for which this assumption is false.' As the time span of 

 important change was considerably longer than that of a single human 

 life, we enjoyed the illusion of fixed conditions. Now the time 

 span is much shorter, and we must learn to experience change 

 ourselves. 



I have so far discussed modification of impact to meet the nature 

 of man. Now we must consider modifying the nature of man to meet 

 impact. 



