MATTER AND FORCE. 69 



permitted to wander away into the atmosphere. But 

 what is it in nature that plays the part of the electric 

 current in our experiments, tearing asunder the locked 

 atoms of carbon, oxygen, and hydrogen? The rays 

 of the sun. The leaves of plants which absorb both 

 the carbonic acid and the aqueous vapour of the air, 

 answer to the cells in which our decompositions took 

 place. And just as the molecular attractions of the 

 silver and the lead found expression in those beautiful 

 branching forms seen in our experiments, so do the 

 molecular attractions of the liberated carbon and 

 hydrogen find expression in the architecture of grasses, 

 plants, and trees. 



In the fall of a cataract and the rush of the wind 

 we have examples of mechanical power. In the com- 

 binations of chemistry and in the formation of crystals 

 and vegetables we have examples of molecular power. 

 You have learned how the atoms of oxygen and hydro- 

 gen rush together to form water. I have not thought 

 it necessary to dwell upon the mighty mechanical en- 

 ergy of their act of combination; but it may be said, 

 in passing, that the clashing together of 1 Ib. of hydro- 

 gen and 8 Ibs. of oxygen to form 9 Ibs. of aqueous 

 vapour, is greater than the shock of a weight of 1,000 

 tons falling from a height of twenty feet against the 

 earth. Now, in order that the atoms of oxygen and 

 hydrogen should rise by their mutual attractions to the 

 velocity corresponding to this enormous mechanical 

 effect, a certain distance must exist between the parti- 

 cles. It is in rushing over this that the velocity is 

 attained. 



This idea of distance between the attracting atoms 

 is of the highest importance in our conception of the 

 system of the world. For the matter of the world may 



