II 



SOURCES OF POWER FOR PLOWING 



MAN has risen in the scale of civilization in exact 

 proportion to the extent to which his brain has de- 

 vised means of lessening'physical work. From the 

 time that practical necessity pulled the Sacred Bull 

 off his high pedestal, and lashed to his horns the long branch 

 of a forked sapling, man has accomplished the world's work 

 with less and less drudgery. First the weaker human beings, 

 then the more powerful though less cunning animals, and 

 finally, one by one, the great forces of nature, have been brought 

 under man's control, harnessed, and made to do work. Man 

 has attained wondrous mental power and a capacity for work 

 that is impossible to the unaided hand. The brain has 

 accomplished what the arm and hand never attempted, 

 converting the power of the sunshine into blessings for the 

 human race. 



The sun is the original source of all energy used on this earth. 

 The steam engine, the gas engine, the windmill, the water- 

 wheel, the draft horse, and man himself are all prime movers 

 to make use of the sun-power which comes to us in widely 

 different natural forms. Steam and hot-air engines burn coal 

 or oil, which contains the energy stored from sunshine in pre- 

 historic vegetation, or wood and straw of more recent growth. 

 The gas engine burns alcohol, which was stored up in the plants 

 of this year's growing, or else products of coal and crude pe- 

 troleum, which contain the power of the sun of past ages. 

 The sun heats' different portions of the earth's sur- 



12 



