



EXPERIMENTS ON CENTRIFUGAL FORCE. 137 



lighter piece of cork. If the thread which connects 

 the cylinders is long enough to allow the cork to be on 

 the farther side of the centre of the frame when the 

 wood is close against one of the uprights, it will remain 

 stretched, because the centrifugal force tends to drive 

 the cork to the opposite side ; but, if the thread was so 

 short that the wooden cylinder, in moving close to the 

 frame, pulled the cork beyond the centre and to the 

 same side of it, the centrifugal force will drive the 

 cork to the same side as the wood, and they will be 

 found close together. 



The places for the holes are first accurately marked and the holes 

 are best pierced by a red-hot wire, from 0'5 to O mm '7 thick ; the 

 wire will have to be heated repeatedly before the frame is perfo- 

 rated. For the cork cylinder a common cork of the proper size 

 will easily be found ; the wooden cylinder is cut first into shape with 

 a knife ; a soft kind of wood (the wood of the limetree, for instance) is 

 best for the purpose. It is then rounded off with a rasp. For per- 

 forating the cylinders the wire should be somewhat thicker, from 1 to 

 l mm> 5; the thread (silk or linen) for connecting the cylinders is passed 

 with a needle through the cork, and fixed by a knot on the other 

 side ; the wooden cylinder must be perforated in the middle, the 

 thread is passed through, and fixed on the other side by a small 

 plug of wood. The threads between the uprights should be of silk. 

 A small piece of wood or wire -is tied to the end of a thread of silk, 

 about 30 cm long, and prevents that end from slipping through the 

 hole ; the other end is passed through one of the holes from the 

 outside to the inside of the frame, through both cylinders, through 

 the corresponding hole in the opposite side of the frame, then back 

 through the adjacent hole, through the second holes of the cylin- 

 iders, and finally through the hole next to the one through which it 

 \v:is passed first. The thread is now tightly stretched, and clamped 

 n the hole by a small wooden plug, which should be allowed to 

 )roject about O cm< 5. A couple of centimetres of thread should also 

 )e left, so that the thread may be withdrawn, after removing the 

 ittle plug, and used again for a repetition of the experiment. 



In a soft or pliable body centrifugal force may cause 

 i change of form. All its parts tend to recede from 



