14 BORDER LINES OF KNOWLEDGE 



electricity, by magnetism, by mechanical agencies ; 

 and, vice versa, that chemical action develops heat, 

 light, electricity, magnetism, mechanical force, as we 

 see in our matches, galvanic batteries, and explosive 

 compounds. Proceeding with our experiments, we 

 find that every kind of force is capable of producing 

 all other kinds, or, in Mr. Faraday's language, that 

 " the various forms under which the forces of matter 

 are made manifest have a common origin, or, in other 

 words, are so directly related and mutually dependent 

 that they are convertible one into another." 



Out of this doctrine naturally springs that of the 

 conservation of force, so ably illustrated by Mr. Grove, 

 Dr. Carpenter, and Mr. Faraday. This idea is no 

 novelty, though it seems so at first sight. It was 

 maintained and disputed among the giants of philos- 

 ophy. Des Cartes and Leibnitz denied that any new 

 motion originated in nature, or that any ever ceased 

 to exist ; all motion being in a circle, passing from 

 one body to another, one losing what the other gained. 

 Newton, on the other hand, believed that new motions 

 were generated and existing ones destroyed. On the 

 first supposition, there is a fixed amount of force al- 

 ways circulating in the universe. On the second, the 

 total amount may be increasing or diminishing. You 

 will find in the Annual of Scientific Discovery for 

 1858 a very interesting lecture by Professor Helm- 

 holtz of Bonn, in which it is maintained that a cer- 

 tain portion of force is lost in every natural process, 



