154 On the Source of Motions upon the Earth, 



perhaps be worthy of consideration, whether the nervous influence is 

 not a force bearing a relation to vital affinity, similar and analogous 

 to that which galvanism has to chemical affinity. It is hardly ne- 

 cessaiy to enter into any examination of the forces of electricity, 

 galvanism, and magnetism, and of chemical action between non- 

 organisable matter. Suffice it to say, that in nature almost all of these 

 are called into existence, or are rendered active, by the physical and 

 chiefly by the chemical changes and circumstances we have already 

 considered, and seem to depend upon the vital and solar influences ; 

 and it may be held to be certain that if all of these were in a state 

 of equilibrium and quiescence upon the earth, none of the others 

 could be called into being. Even when these forces seem to be pro- 

 duced in the most artificial way, they might, in most cases, I believe, 

 be shewn to be the product of the forces of life and external nature, 

 and the equivalent of these forces actually so employed : — that in the 

 case of a galvanic battery, for example, which may be regarded as 

 one of the most artificial sources of motion known, we employ in the 

 production of the different metals, acids, or other bodies, which form 

 it, as much of what we have endeavoured to shew is vital and solar 

 force in the form of fire, manual labour, &c., as we can gain froin 

 them, in the form of galvanism. By our operations on certain sub- 

 stances, we destroy their neutrality ; when these are brought to- 

 gether, in a certain manner, they neutralize each other, and in doing 

 so, they evolve the force of galvanism ; and it is, I think, manifest, 

 that the force so evolved, will be the equivalent, and the measure 

 of that which was employed in the destruction of their neutrality. 

 It is true, that the elements of a battery may be found existing 

 ready formed in nature, in which case the source of the galvanism 

 may not be capable of being traced farther back than to the in- 

 herent chemical forces. But, for the most part, the elements of a 

 battery are formed by art. We commenced our view of the origin 

 of terrestrial motion, by supposing that the matter of the earth had 

 been carried through all the changes which its inherent forces were 

 capable of inducing, and that it had been rendered neutral ; and we 

 acknowledged at the time, that this was a mere supposition, and 

 that all matter was not carried through its whole series of molecular 

 changes. The motions, therefore, produced by such a battery as we 

 have mentioned, do not come within the limits of our subject. 



Before finishing this part of the subject, and with a view to its 

 completeness, it is perhaps proper to advert to those terrestrial mo- 

 tions which originate in the interior of the earth, such as volcanoes, 

 earthquakes, and the like, and which, according to the general opinion, 

 are the eftects of a great heat existing in the interior of the globe. 

 Nothing can positively be said with regard to the origin of this in- 

 ternal heat, but it is commonly looked upon as a relic of some former 

 condition of the earth. Thus, it has been supposed, that the various 

 elementary substances of which the earth consists had, in the early 



