324 APPENDIX. [No. XXIII. 



the lowest equivalent, because the least weight would answer our purpose ; 

 hydrogen and carbon have the lowest equivalent, and coal being an hydro- 

 carbon, is that matter which is pre-eminently adapted to combine with 

 oxygen, the more especially as the product of the new attraction is readily 

 dissipated. If we compare zinc with coals, we find that it has an equiva- 

 lent eight times higher, and its energy of combustion with oxygen is 

 perhaps not more than one-third that of carbon : moreover, the cost of 

 zinc is forty times dearer than coals ; consequently, as a source of power, 

 zinc would be 960 times dearer than coals. 



Our theory thus indicates why we select coals for light, heat, motion, 

 and chemical changes, instead of zinc ; and this difference of cost prevents 

 the voltaic battery, the most perfect human device, from universal 

 application. 



In animals the hydrogen and carbon in the food they consume is the 

 source of power, and the horse without hay and oats is as powerless as the 

 steam-engine without coals or the battery without zinc. 



Starting with the new attraction of hydrogen and carbon, with oxygen 

 as a source of power, we must take care so to apply it upon attracted 

 matter, that we may produce, according to our necessity, heat, light, 

 motion or electricity ; for it would not be difficult, in fact it constantly 

 happens in practice, for one variety of force to be produced when another 

 is desired, and whatever is thus improperly generated is wasted. 



In physics and physiology, in mechanics and medicine, facts, no less 

 than theory, declare that no effect occurs without material cause, that 

 no initial change takes place without equivalent result, and in all cases 

 there is but one source ; in fact a complete " Monogenesis of all Physical 

 Forces." 



In consequence of the " Monogetic Origin of Physical Forces," each 

 possesses within itself the power of a new attraction, which, according to 

 the amount of the initial change, can produce an equivalent or relational 

 amount of any other force. Electricity may produce light, heat or motion. 

 Motion may produce heat, light, electricity ; light may produce electricity ; 

 motion, heat ; heat may produce motion, electricity, light ; and so we may 

 ring the changes of the convertibility of physical forces ad infinitwm. 



Whenever a new attraction acts upon matter under attraction, the 

 attraction already existing seeks to maintain itself, and in consequence of 

 this resistance time is occupied, and according to the energy of the change, 

 so is the time diminished or increased. 



I know no part of physical science which presents more important 

 matter for consideration than the phenomenon of time : for let us suppose 

 that a change of matter could take place without time ; the coals in our 

 grates would be consumed instantly if our house caught light, the whole 

 would momentarily vanish if we set in motion any body, it would arrive 

 at its destination quicker than thought, and be dashed to pieces. 

 Chemistry supplies us with substances, the particles of which are held 

 together so slightly, that upon the slightest application of force they are 

 separated : iodide of nitrogen, for instance, separates upon the slightest 

 agitation into its component parts. The safety of the proper use of gun- 

 powder depends upon its progressive action, which is slow as compared 

 with iodide of nitrogen, or with some varieties 'of gun-cotton. 



Man derives the idea of time from the resistance to change : if the 



