A HISTORY OF SCIENCE 



universe where this force does not prevail. We do 

 not know that there may not come a period when this 

 force will cease to operate in our universe, and when, 

 for example, it will be superseded by the universal 

 domination of a force of mutual repulsion. For aught 

 we know to the contrary, our universe may be a pulsing 

 organism, or portion of an organism, all the particles 

 of which are at one moment pulled together and the 

 next moment hurled apart the moments of this com- 

 putation being, of course, myriads of years as we hu- 

 man pygmies compute time. 



To us it would be a miracle if a heavy body, unsup- 

 ported, should fly off into space instead of dropping 

 towards the centre of the earth; yet the time may 

 come when all such heavy objects will thus fly off into 

 space, and when the observer, could there be such, 

 must marvel at the miracle of seeing a heavy object 

 fall towards the earth. Such thoughts as these should 

 command the attention of every student of science 

 who would really understand the meaning of what are 

 termed natural laws. But, on the other hand, such 

 suggestions must be held carefully in check by the 

 observation that scientific imagining as to what may 

 come to pass at some remote future time must in no 

 wise influence our practical faith in the universality of 

 certain natural laws in the present epoch. We may 

 imagine a time when terrestrial gravitation no longer 

 exerts its power, but we dare not challenge that 

 power in the present. There could be no science did 

 we not accept certain constantly observed phenomena 

 as the effect of certain causes. The whole body of 

 science is made up solely of such observations and in- 



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