EXPERIMENTS ON CENTRIFUGAL FORCE. 145 



water, which may be coloured with magenta, closed 

 with a flat cork, and suspended as in the figure, in 

 which the cork is not shown. Setting it in rotation, 

 iirst slowly, but gradually more and more rapidly, the 

 water will fly from the middle of the vessel towards the 

 sides, finally leaving the central portion without water, 

 as shown in figure. 



In this state of matters the cork could be dispensed with, and 

 the water would not run out. But as it is not well possible to with- 

 draw the cork from the mouth while the vessel is in rapid rotation, 

 the use of the cork may be altogether avoided. It will be seen 

 farther on, when speaking of the pressure of the atmosphere, that if a 

 vessel be filled with a liquid and its mouth be covered with a piece 

 of stiff paper, the liquid will not run out if the vessel is inverted. 

 Out of a piece of stiff drawing-paper, or an old playing-card, cut a 

 rectangle, 10 cm long, 5 cm broad ; fill the vessel nearly half with 

 water, press the paper with the fingers of the left hand upon the 

 mouth, and invert the vessel with the right hand, after having 

 placed upon the table a china plate so as to receive the few drops 

 which will run out. As soon as the paper cover is in a perfectly 

 lorizontal position, the hand may be withdrawn. The plate should 

 ie kept underneath the vessel during the experiment, in case of acci- 

 lental discharge of the water. The rotation must be very gradually 

 ncreased, otherwise the string gets twisted and knotty. When 

 he water is observed to have left the paper altogether, the fore- 

 inger is brought near it from the side, and as soon as it is touched 

 he paper will fly off ; if you are not quite sure of the steadiness of 

 r our left hand, leave the handle of the flywheel for a moment, and 

 ise the right forefinger. When the rotation is very rapid, it will, 

 >y the inertia of the apparatus, go on with sufficient speed to allow 

 ou a few moments for the removal of the paper cover. When the 

 xperiment is to be finished, and you cease to work the handle, the 

 essel will rotate longer than the apparatus, the cord becomes twisted 

 nd shorter, and the vessel rises. Therefore follow the vessel with 

 our plate, in order to prevent both the breaking of the vessel or 

 f the plate in case the cord should break, and also the splashing 

 bout of the water when it begins to leave the mouth of the vessel ; 

 ut take care not to touch the vessel with the plate. 

 A suitable vessel, 10 or ll cm wide, rather shallow, can easily be 

 looted from the stock of a dealer inparaffine lamps. The collar is 



