176 



ELEMENTS OF GENERAL SCIENCE 



The knowledge of the use of machines is of great value 

 to civilized man. If we had been compelled to. depend on 

 bare hands and our own physical strength alone for accom- 

 plishing all sorts of work, our present civilization could not 

 have developed. Our condition would probably be much 



or lift 



Weight or 

 pressure 



Force 



^Fulcrum 



FIG. 89. Applications of the lever 



The lever involves a weight to be lifted or pressure to be exerted, a force to be 



applied, and a fulcrum or pivotal point where the force works against the weight 



or pressure. Note the above and other applications of the lever and discover 



what advantages are derived from it 



like that of the tribes in those parts of Africa, Asia, and 

 Australia where the soil is dug with a stick and goods are 

 transported on the backs of men. The use of various con- 

 trivances which assist in the accomplishment of work, and 

 the knowledge of their possibilities, are among the marks 

 which distinguish civilized people from savages. In times of 

 war the use of machines makes war more terrible. 



