ON GEOLOGICAL TIME. 35 



perienced tides and viscous resistance against the 

 tidal motion. The only other view we can have 

 the only other hypothesis we can make is that 

 the moon was created with such an angular 

 velocity as to turn always the same face to the 

 earth. But the course of speculative and physical 

 science is absolutely irresistible as regards the 

 relation between cause and effect. Whenever we 

 can find a possible antecedent condition of matter, 

 we cannot help inferring that that possible ante- 

 cedent did really exist as a preceding condition 

 a condition, it may be, preceding any historical 

 information we can have but preceding and 

 being a condition from which the present con- 

 dition of things has originated by force acting 

 according to laws controlling all matter. The 

 theory that the moon has been brought to her 

 present condition of rotation by tidal friction of 

 her own mass was, I believe, first given by Helm- 

 holtz. I cannot say so certainly, because so many 

 philosophers have speculated and drawn con- 

 clusions regarding antecedents of the solar system 

 from very general philosophic principles ; but, so 



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