io8 Mind indirectly influences itself. 



bodies. With the electric locomotive, the greater the 

 load it has to draw, or the steeper the incline it has 

 to ascend, the more strongly does it exert its strength, 

 up to the full limits of its power. Neither in physical 

 nor in mental actions can a body or force usually act 

 directly upon itself to change its state whether of 

 activity or rest. In both classes of cases however we 

 meet with plenty of instances where, a body by an 

 .almost imperceptible expenditure of energy on its own 

 part either alters some surrounding conditions, or 

 excites a powerful liberation of energy in another 

 body which then reacts upon it to change its state. 

 In this way the action of clock-work in the self- 

 exploding apparatus of a torpedo liberates at a par- 

 ticular moment a spring, and causes an explosion 

 which destroys the apparatus. Similarly, whilst a 

 man, in many cases, is unable to directly alter his 

 mental state, to increase or diminish his mental 

 activity, to cause sleep, &c., he is able indirectly to 

 change his mental condition by drinking stimulants or 

 by adopting means of self-education ; and to induce 

 sleep by means of opium, suitable exercise, &c. 



The principles of indestructibility or conservation 

 of matter and energy, flow from the preceding ones, 

 and are exhibited in mental actions as well as in 

 physical ones. Whilst the universal experience of 

 mankind has not yet afforded us a single well verified 

 instance of actual creation or destruction of matter or 

 energy, it has supplied us with plenty of examples of 

 apparent destruction and creation of each of them. 



