258 



SCIENCE. 



[N. S. Vol. XXII. No. 557. 



by reference to political instituti( .ns, be- 

 cause we all fancy we understand, some- 

 thing of politics. 



The complex interactions of man with 

 man in a community are usually described 

 by such comprehensive terms as ' the state, ' 

 'the commonwealth' or 'the government.' 

 Various states differ widely in their con- 

 stitution and in the degree of the complex- 

 ity of their organization, and we classify 

 them by various general terms, such as 

 'autocracy,' 'aristocracy' or 'democracy,' 

 which express somewhat loosely their lead- 

 ing characteristics. But for the purpose 

 of showing the analogy with physics we 

 need terms of wider import than those 

 habitually used in politics. All forms of 

 the state imply inter-relationship in the ac- 

 tions of men, and action implies movement. 

 Thus the state may be described as a con- 

 figuration or arrangement of a community 

 of men; or we may say that it implies a 

 definite mode of motion of men — that is to 

 say, an organized scheme of action of man 

 on man. Political history gives an account 

 of the gradual changes in such configura- 

 tions or modes of motion of men as have 

 possessed the quality of persistence or of 

 stability to resist the disintegrating in- 

 fluence of surrounding circumstances. 



In the history of a state we find this 

 stability or power of persistence contin- 

 ually changing. It sloMdy rises to a maxi- 

 mum, and then declines; when it falls to 

 nothing a revolution ensues, and a new 

 form of government is established. This 

 new mode of motion of men, or govern- 

 ment, has at first but little stability, but 

 it gradually acquires strength and perma- 

 nence, until in its turn the slow decay in 

 the power of persistence leads on to a new 

 revolution. Such crises in political history 

 may give rise to a condition in which the 

 state is incapable of perpetuation by trans- 

 formation. This occurs when a savage 

 tribe nearly exterminates anothet and leads 



the few survivors into slavery; the pre- 

 vious form of government then becomes 

 extinct. 



Now turn to the evolution of the various 

 forms of life. The fundamental idea in 

 the theory of natural selection is the per- 

 sistence of those types of life which are 

 adapted to their surrounding conditions, 

 and the elimination by extermination of 

 the ill-adapted types. The struggle for 

 life amongst forms possessing various de- 

 grees of adaptation to slowly varying con- 

 ditions is held to explain the transmutation 

 of species. Although a different phraseol- 

 ogy is used when we speak of the physical 

 world, yet the idea is essentially the same. 

 Theories of physical , evolution involve the 

 discovery of modes of motion or configura- 

 tions of matter which are capable of per- 

 sistence. The physicist describes such 

 types as stable; the biologist calls them 

 species. 



The physicist, the biologist and the his- 

 torian alike watch the effect of slowly vary- 

 ing external conditions; they all observe 

 the rise and decline of stability, with the 

 consequent change of type of motion, trans- 

 mutation of species or revolution. 



And now after this preface I turn to as- 

 tronomical theories of evolution. 



The German astronomer Bode long agO' 

 propounded a simple empirical law con- 

 cerning the distances at which the several 

 planets move about the sun, and his for- 

 mula embraces so large a number of cases- 

 with accuracy that we are compelled to 

 believe that it arises in some manner from 

 the primitive conditions of the planetary 

 system. 



The explanation of the causes which have 

 led to this simple law as to the planetary 

 distances presents an interesting problem, 

 and although it is still unsolved, we may 

 obtain some insight into its meaning by 

 considering what may be called a working- 

 model of ideal simplicity. 



