LAWS OF CHEMICAL AFFINITY. 101 



and there it is burning under the water ; and so 

 it will continue until exhausted, and all by 

 reason of the requisite amount of oxygen being 

 contained within the substance. It is by this 

 kind of attraction of the different particles one 

 to the other that we are enabled to trace the 

 laws of chemical affinity, and the wonderful 

 variety of the exertions of these laws. 



Now I want you to observe that one great 

 exertion of this power which is known as chemical 

 affinity is to produce HEAT and light; you know, 

 as a matter of fact, no doubt, that when bodies 

 burn they give out heat, but it is a curious thing 

 that this heat does not continue the heat goes 

 away as soon as the action stops, and you see 

 thereby that it depends upon the action during 

 the time it is going on. It is not so with gravi- 

 tation; this force is continuous, and is just as 

 effective in making that lead press on the table 

 as it was when it first fell there. Nothing occurs 

 there which disappears when the action of falling 

 is over; the pressure is upon the table, and will 

 remain there until the lead is removed ; whereas, 

 in the action of chemical affinity to give light 

 and heat, they go away immediately the action 

 is over. This lamp seems to evolve heat and 



H 3 



