^ll_ _._ THE USE OF HYPOTHESIS. 61 



space; it is .in positive contradiction to the o]d~di^ 

 that nothing can act but through some medium T^ 



r 



ordinary air at til ' '3S' f tlmes the ehlsiic f of 



Works, vol. i. p. 4I5 . 

 r W*w* on ^ctewtt/fc Sw&jecfc, p. 28^ 



L L 2 



