Scientific Lectures. 221 



Heat is power. Coal burned under steam boilers supplies the 

 power to move machinery, drive locomotives, propel steamships, run 

 mills. It takes the place of human muscle. 



Dr. Lardner has given us an excellent illustration of the power of 

 coal. Herodotus tells us that it required 100,000 men twenty years 

 to build the great pyramid of Egypt. Dr. Lardner estimates that 

 480 tons of .coal would have hoisted every block of stone into its place. 



The burning of coal is now a source of great national wealth. 

 Great Britain now leads the world, simply because she mines and 

 consumes more coal than any other country. In Great Britain 

 20,000,000 tons of coal are consumed in a year under steam boilers, 

 which is equal to the muscle of 133,000,000 of men. What an enor- 

 mous power is here represented in an industrial point of view! She 

 has only 12,000 square miles of coal area; we have 130,000 square 

 miles of coal area. Great Britain raises, for heat, exportation and 

 other purposes, 110,000,000 of tons a year, while the United States 

 has thirty times as much coal land, and only raises 30,000,000. 

 We have a treasure of coal beneath our territory, which would enable 

 us to do all the work of 400,000,000 of men. This is the secret of 

 the wealth of countries where manufacturing industries prevail. 



The Sun the Source of Power. 



And the power which is derived from the coal is, after all, only 

 sun power. It is the power of the sun that drives the steam engine ; 

 it was the chemical force of the sun which caused the plants to grow 

 which produced the coal. Coal is sun power stored up hundreds of 

 thousands of years ago for the use of man. Almost all the power and 

 force that we have in the earth come from the sun. From the sun 

 comes my activity this moment ; it gives me food, and food makes 

 my muscles, nerves and brain, which are now undergoing oxidation 

 to supply the force by which I think, speak and act. 



The sun, therefore, is the great source of power. We depend upon 

 it for heat, for light, for thought. We live by it. It is the power 

 which drives our steam engines. Its power is exhibited everywhere. 



Fires — their Causes and Prevention. 

 I want to say a word or two with regard to fires, which are a 

 most undesirable form of combustion. From September 1, 1S69, to 

 May 31, 1871, the last two years, the damage by fire, not counting 

 Chicago, cost us $76,150,000, only about one-half covered by 

 insurance. It therefore becomes extremely important to ascertain 



