MECHANICS. 61 



by those who are unaware of what has already been 

 done, and who are astonished, on presenting their 

 claims at the patent office, or to the public, to find they 

 have been anticipated long ago by others of whose in- 

 ventions they never had heard. By not attending 

 sufficiently to the principles of the mechanic arts, 

 many contrive new machines of complicated form, with 

 variety of wheels, and pulleys, and cogs, and bands, 

 imagining that by all this trumpery they are gaining 

 power, when in truth every additional item of gearing 

 serves only to diminish power by the multiplication 

 of friction. Hence the hundreds of patents for churns, 

 for washing-machines, (fee. (fee. each more complicated 

 than its predecessor, and of course requiring more 

 power. Simplicity is the grand desideratum in all 

 machinery, but that is too often disregarded. First 

 principles are neglected, and we waste our strength in 

 vain. The principle of the lever and steelyard are not 

 generally understood, and we have been surprised at 

 the ignorance, on these subjects, of those who ought to 

 be better informed. 



The simplest mechanical power is that of the lever. 

 When the lever is ten feet long, and the fulcrum, or 

 prop, is one foot distant from the body to be raised, one 

 pound attached to the long end of the lever will raise 

 nine pounds hung on the short end, because the one 

 pound is nine times as distant from the fulcrum, or pivot, 

 as the nine pounds are. 



On this principle is formed the common steelyard ; 

 and any one who has an exact rule may prove the 

 accuracy of a pair of steelyards merely by applying 

 that rule and measuring the distances of the notches, 

 or indents, in which the poise, or balance^ rests in 

 weighing. 



Suppose the weight on the hook of your steelyard 



be five pounds, your fulcrum^ or pivot, by which you 



hold up the steelyard is one inch distant from the hook ; 



then take just one pound for your poise, and place it 



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