366 SCIENTIFIC THOUGHT. 



though matter and energy be indestructible, the succes- 

 sion of phenomena, the changes and processes which we 

 call the genesis or history of things, are dependent on the 

 condition in which energy exists; it being a general 

 tendency for energy not to be lost, but to become un- 

 available; change and action, the life of things every- 

 where, depending on an equalisation of existing differ- 

 ences, say of level or temperature, or quicker and 

 slower motions. This great property of natural, as dis- 

 tinguished from purely mechanical, processes, explains 

 the fact that the processes of nature are irreversible, 

 that the clock cannot be turned back, that everything 

 moves in a certain direction. Various attempts have 

 been made to explain mechanically this remarkable 

 property of all natural processes, which seems to lead 

 us to the conception of a definite beginning and to 

 shadow forth a possible end the interval, which con- 

 tains the life or history of nature, being occupied with 

 the slow but inevitable running down or degradation 

 of the great store of energy from an active to an in- 

 active or unavailable condition. 

 54. This doctrine of the degradation or dissipation of 



Mystery of 



the actual energy leads us one step farther towards an understand- 



processes of 



ing, or at least a description, of the processes of nature, 

 but also of their mystery. It has been urged that, as 

 we always only deal with a small portion of existing 

 things, we have no right to apply conceptions which are 

 based upon a restricted observation to the totality of 

 things in the universe. For instance, we know nothing 

 of what becomes of the energy radiated away into empty 

 space. This is a reflection we should always bear in 



