1 04 Mental energy can be stored up. 



they are stored up in what is termed a potential or 

 latent state, ready for liberation at a future occasion, 

 when the suitable conditions are present ; the storage 

 of chemical power in gunpowder, of solar heat in 

 coal, and its subsequent liberation in our fires, are 

 suitable examples. The principle of deferred activity 

 and storing up of power, occurs also in vital and 

 mental phenomena ; potential heat is stored up in 

 our food, and is afterwards evolved by oxidation in 

 our tissues. Muscular power is stored up during sleep, 

 ready to be evolved during labour. The storage also 

 of cerebral impressions, and cerebral energy, ready to 

 call forth ideas, and thereby powerful emotions, by 

 the exciting action of memory, may also be viewed as 

 an instance of similar kind belonging to mental phen- 

 omena. A new and striking instance of the storage 

 of energy has been shewn in Faure's improved form 

 of secondary voltaic battery, in which the most 

 powerful voltaic current may be (at least practically) 

 stored up (in a box containing lead plates immersed 

 in dilute sulphuric acid) and conveyed to a distance 

 with little loss, and then liberated. 



Exciting causes operate very extensively in mental 

 actions as well as in physical ones, a mere look or 

 word from an eloquent speaker will excite the passions 

 and liberate the muscular power of a multitude. 

 Every part of the human body, especially the muscles 

 and nerve centres, is a store-house of power always 

 ready to be set free by the slightest suitable causes ; 

 this is strongly illustrated in the irrepressible activity 



