MAN'S STRENGTH NOT SUFFICIENT 



309 



calculated as necessary is 100 pounds, the loss due to friction is 

 50 pounds, and the machine, instead of being thoroughly 

 efficient, is only two thirds efficient. 



Machinists make every effort to eliminate from a machine 

 the waste due to friction, leveling and grinding to the most 

 perfect smoothness and adjustment every part of the ma- 

 chine. When the machine is in use, friction may be further 

 reduced by the use of lubricating oil. But friction can never 

 be totally eliminated, and machines of even the finest con- 

 struction lose by friction some of their efficiency, while poorly 

 constructed ones lose by friction as much as one half of their 

 efficiency. 



Man's strength not sufficient for machines. A machine, 

 an inert mass of metal and wood, cannot of itself do any 

 work, but can only distribute the energy which is 

 brought to it. Fortunately it is not necessary that 

 this energy should be contributed by man alone, 

 because the store of energy possessed by him is 

 very small in comparison with the energy required 

 to run locomotives, automobiles, or sawmills. Per- 

 haps the greatest value of machines lies in the fact 

 that they enable man to perform work by the 

 use of energy other than his 

 own. 



Figure 181 shows one way 

 in which a horse's energy can 



be Utilized in lifting heavy FlG - 



, fl i 



loads. Even the fleeting wind 



has been harnessed by man, and, as in the windmill, made 



to work for him (Fig. 182). One sees dotting the country 



windmills large and small, and in Holland, the country of wind- 



mills, the landowner who does not possess a windmill is poot 



indeed. 



- Man's strength is not sufficient 



for heay y work - 



