The hand : its mechanism and vital endowments, as evincing design, and illustrating the power, wisdom, and goodness of God . humerus, or arm-bone ; c. theieltoid muscle of the shoulder, arising from the shoulder-blade and clavicle,and inserted into the arm-bone ; D. a muscle >\hich draws the arm down, as instriking with a sword or hammer. K 130 OF THE MUSCLES OF chap. iv. equal to force. The advantage of the rapid descent ofa heavy body is, that a smart blow is given, and an effectproduced which the combined power of all the muscles,without this mechanical distribution of force, could notac
The hand : its mechanism and vital endowments, as evincing design, and illustrating the power, wisdom, and goodness of God . humerus, or arm-bone ; c. theieltoid muscle of the shoulder, arising from the shoulder-blade and clavicle,and inserted into the arm-bone ; D. a muscle >\hich draws the arm down, as instriking with a sword or hammer. K 130 OF THE MUSCLES OF chap. iv. equal to force. The advantage of the rapid descent ofa heavy body is, that a smart blow is given, and an effectproduced which the combined power of all the muscles,without this mechanical distribution of force, could notaccomphsh. It is, in truth, similar to the operation ofthe fly-wheel, by which the gTadual motion of an engineis accmnulated in a point of time, and a blow struckcapable of stamping a piece of gold or silver. Inwhat respect does the mechanism of the arm differfrom the engine with wliich the printer throws offhis sheet ? Here is a lever with a heavy ball at theend; in proportion to its weight it is difficult to be putin motion; the printer, therefore, takes hold of thelever near the ball, at A.; were he to continue pulhng. at that part of the lever, he would give to the ball nomore velocity than that of his hand; but having put theball into motion, he slips his hand down the lever to he applied his hand near b. at first, he could nothave moved the weight; but the ball being now inmotion, if he direct the whole strength of his arm to thelever near the centre of motion, the velocity of the CHAP IV. THE AEM AND RAKD. 131 weight at the further end ^^dll be greatly the weight and velocity being combined, theimpulse given to the screw is much more powerful thanif he had continued to pull upon the fui^ther end of thelever at a. If we now turn back to the diagram (page 129), weshall miderstand how much is gained by the muscle, c,being inserted near the centre of motion, although,in one sense, at a mechanical disadvantage. First,that mode of insertion is in correspon
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjecthand, bookyear1874
