IN THE ANIMAL ORGANISM. 235 



at once recognised in the complete supply of the matter 

 consumed. In old age more is wasted ; in childhood 

 more is supplied than wasted. 



The force available for mechanical purposes in an 

 adult man is reckoned, in mechanics, equal to |th of his 

 own weight, which he can move during eight hours, 

 with a velocity of five feet in two seconds. 



If the weight of a man be 150 Ibs., his force is 

 equal to a weight of 30 Ibs. carried by him to a dis- 

 tance of 72,000 feet. For every second his momen- 

 tum offeree is= 30X2-5 =75 Ibs.; and for the 

 whole day's work, his momentum of motion is = 30 X 

 72,000 = 2,160,000. 



By the restoration of the original weight of his body, 

 the man collects again a sum of force which allows him, 

 next day, to produce, without exhaustion, the same 

 amount of mechanical effects. 



This supply of force is furnished in a seven hours 1 

 sleep. 



In manufactories of rolled iron it frequently happens, 

 that the pressure of the engine, going at its ordinary 

 rate, is not sufficient to force a rod of iron of a certain 

 thickness to pass below the cylinders. The workman, 

 in this case, allows the whole force of the steam to act 

 on the revolving wheel, and not until this has acquired 

 a great velocity does he bring the rod under the rollers ; 

 when it is instantly flattened with great ease into a 

 plate, while the wheel gradually loses the velocity it 

 had acquired. What the wheel gained in velocity, the 



