MAGNETISM AND CHEMICAL AFFINITY. 147 



as this. And there is also another beautiful re- 

 sult dependent upon chemical affinity in that fine 

 lead-tree ( 24 ), the lead growing and growing by 

 virtue of this power. The lead and the zinc are 

 combined together in a little voltaic arrangement, 

 in a manner far more important than the power- 

 ful one you see here, because in nature these 

 minute actions are going on for ever, and are of 

 great and wonderful importance in the precipi- 

 tation of metals and formation of mineral veins, 

 and so forth. These actions are not for a 

 limited time, like my battery here, but they act 

 for ever in small degrees, accumulating more 

 and more of the results. 



I have here given you all the illustrations 

 that time will permit me to show you of 

 chemical affinity producing electricity, and 

 electricity again becoming chemical affinity. 

 Let that suffice for the present ; and let us now 

 go a little deeper into the subject of this chemical 

 force, or this electricity which shall I name first 



the one producing the other in a variety of 

 ways. These forces are also wonderful in their 

 power of producing another of the forces we have 

 been considering, namely, that of magnetism, and 



you know that it is only of late years, and long 



L 2 



