upright the centre of gravity of the man G falls within the base of support; and if his load L falls without the base, as does likewise _g_, the common centre of gravity of the man and load, the consequence would be that he would fall backwards; but this is prevented, or, which is the same thing, the point _g_ is brought within the base by the man bending his body forward."[15] What is called the lay figure of the painter--a wooden image with many joints--may be bent here and there; but the artist who wanted to draw a porter with a load could not put a hundredweight upon the back of his image and keep it upon its legs. The natural machinery by which a man even lifts his hand to his head is at once so complex and so simple, so apparently easy and yet so entirely dependent upon the right adjustment of a great many contrary forces, that no automaton, or machine imitating the actions of man, could ever be made to effect this seemingly simple motion, without showing that the contrivance was imperfect,--that it was a mere imitation, and a very clumsy one. What an easy thing it appears to be for a farming man to thrash his corn with a flail; and yet what an expensive arrangement of wheels is necessary to produce the same effects with a thrashing-machine! The truth is, that the man's arm and the flail form a much more curious machine than the other machine of wheels, which does the same work; and the real question as regards the value of the two machines is, which machine in the greater degree lessens the cost of production?