CHRONOLOGICAL ORDER OF THE SCIENCES. 185 



of the various physical and chemical forces appear to con- 

 tradict a mechanical interpretation of them. Something 

 analogous also to the hydrostatic law of equal distribution 

 of pressure is exhibited among men. Each man tends to 

 recede from an excess of pressure, and to distribute it upon 

 his neighbours. The notion of an universal ether, which 

 pervades all bodies and all space, is first introduced as a 

 part of science in the subjects of light and heat, the ether 

 being considered to be the medium by which light, radiant 

 heat, electric and magnetic induction are transmitted. The 

 forces of light and heat are also less complex than those of 

 electricity, magnetism, and chemical affinity. Light and 

 heat are single, electricity is dual and polar, magnetism is 

 of two kinds, para and dia, each of which is dual and 

 polar. Chemical affinity is also dual ; basic affinity requires 

 acid affinity to enable it to act. Heat may be produced 

 by friction of different parts of the same substance ; but 

 electricity requires either two substances, or two portions 

 of the same substance in different states; and chemical 

 affinity nearly always requires two, and sometimes more 

 substances. We further know that chemical phenomena 

 necessarily include and are governed by physical conditions, 

 but physical phenomena do not necessarily include chemical 

 conditions ; and that vital actions include the operation 

 of all the physical and chemical powers. The concrete 

 sciences, crystallography, mineralogy, geology, meteorology, 

 botany, zoology, &c., being each composed of portions of 

 several of the simple sciences, do not belong to the list, 

 and their positions in such a series are more difficult to 

 determine. 



From these and other considerations, based upon an 

 immense number of facts, we have gradually acquired the 

 idea of the above natural order of dependence of the simple 

 sciences, and of their respective forces and phenomena. 



