514 



REPORT 1879. 



There is nothing unnatural in the fact that friction decreases with speed. 

 Friction is mechanical work ; it requires a definite force to move a body which is 



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i n contact with another, and such movement causes a perceptible wear of the sur- 

 faces in contact. The manner in which this work is accomplished can be explained 



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only by the fact that the surfaces in contact are not perfectly smooth, but irregular, 



