MANUAL WORK. 385 



periments with a few glasses and tubes, they 

 mostly find the greatest difficulties in grasping 

 the mechanical introduction into physics, partly 

 because they do not know geometry, and espe- 

 cially because they are merely shown costly 

 machines instead of being induced to make 

 themselves plain apparatus for illustrating the 

 phenomena they study. 



Instead of learning the laws of force with 

 plain instruments which a boy of fifteen can 

 easily make, they learn them from mere draw- 

 ings, in a purely abstract fashion. Instead of 

 making themselves an Atwood's machine with a 

 broomstick and the wheel of an old clock, or 

 verifying the laws of falling bodies with a key 

 gliding on. an inclined string, they are shown 

 a complicated apparatus, and in most cases the 

 teacher himself does not know how to explain 

 to them the principle of the apparatus, and 

 indulges in irrelevant details. And so it goes 

 on from the beginning to the end, with but a 

 few honourable exceptions.* 



* Take, for instance, the description of Atwood's machine 

 in any course of elementary physics. You will find very great 

 attention paid to the wheels on which the axle of the pulley is 

 made to lie ; hollow boxes, plates and rings, the clock, and 

 other accessories will be mentioned before one word is said upon 

 the leading idea of the machine, which is to slacken the motion 

 of a falling body by making a falling body of small weight move 

 a heavier body which is in the state of inertia, gravity acting 

 on it in two opposite directions. That was the inventor's idea ; 

 13 



