350 



SCIENTIFIC THOUGHT. 



as. 

 interest 



attached 



dimensions 



And we cannot but be struck by the fact that only those 

 dimensions which we call molar appear to be the abode 

 ^ li y i n g an d conscious beings. The cosmical world has, 

 so far as we know, no inhabitant which can behold it in 

 the same way as man beholds this planet, and the same 

 obtains so far as we are acquainted with the molecular 

 world. So far as our knowledge goes and is likely ever 

 to reach, a special importance or dignity will therefore 

 always belong to molar dimensions and masses. The pro- 

 cess by which we try to picture to ourselves in tracings and 

 models, constructed in molar dimensions, the behaviour 

 and appearance of cosmical as well as molecular masses will 

 always recommend itself, not only as the most practical, but 

 likewise as the most interesting and plausible, for only by 

 this procedure do these unreachable worlds become amen- 

 able to direct observation and to the processes of experi- 

 ment in the physical laboratory. It seems prima facie 

 that the wealth of phenomena and the variety of different 

 kinds of motion decrease as we ascend into the cosmical, 

 or as we descend into the molecular world, giving 'way 

 in the former to essentially uniform, though to many 

 times multiplied modes of motion, and disappearing in 



Punivers sont inde"pendantes de ses 

 dimensions absolues, comme elles 

 le sont, du mouvement absolu, 

 qu'il peut avoir dans 1'espace ; et 

 nous ne pouvons observer et con- 

 naitre que des rapports." This is 

 easily seen. For if in the formula 



/= , the dimensions be all 



* /f*n ' 



multiplied by K, we get the new 



formula F= K 6 ~ n x , and the 

 r n 



acceleration of a body moving round 



a centre like the sun would be 



.. , = K s ~ n x . which is only 

 K^m r n 



K times the acceleration 



if 



n = 2. In another passage Laplace 

 repeats the above statement in 

 slightly different words: "L'uni- 

 vers reduit successivement jusqu'au 

 plus petit espace imaginable, offrir- 

 ait tou jours les memes apparences 

 a ses observateurs " (p. 440). That 

 this would not apply to molecular 

 attractions or repulsions is evident. 



