EXPERIMENTS ON CENTRIFUGAL FOKCE. 141 



the disc to project 2 cm below the tnbe. Place the vessel for the 

 alcoholic mixture, so that the disc may be in the middle of it ; 

 fill the vessel with the mixture, and form a globe of oil, about 3 cm 

 in diameter, with the pipette, round the disc. If the globe rises 

 too much above the disc, add a little alcohol ; if it shows a tendency 

 to sink, add a little water. The flattening of the globe requires so 

 little speed, that it is only necessary to place the point of the finger 

 near the edge of the wooden plate of the apparatus, and move it 

 slowly round ; if greater speed is given by the fly-wheel, the oil forms 

 a ring freely suspended round the disc. The apparatus should be 

 stopped immediately when the ring is formed, or otherwise it soon 

 breaks up into single drops which do not again combine into one. The 

 flattening alone maybe shown,without the whirling- table, by bending 

 the upper end of the wire which projects from the glass tube into a 

 small handle for turning. To see the form of the globe better at a 

 distance, the oil may be coloured by placing a few pieces of alkanet 

 root in it and leaving them there for some time before using the oil. 



A circular disc, a b, fig. 100, of stout pasteboard 

 ('6 to 4 mm thick), of 25 Cffi diameter, is suspended to the 

 ower end of the shaft of the whirling -table by means 

 )f a semicircular hook fixed into the middle and a 

 straight wire about 60 cm long and l mm '5 thick, the 

 ipparatus projecting from the edge of the table as in 

 he pendulum experiment. It is obvious that the wire 

 tself prevents the disc being quite vertical: the point 

 i will be at some little distance from the wire, in the 

 igure to the left of it, while the lower portion inclines 

 |0 the right. As soon as rotation commences, the 

 entrifugal force tends to throw all parts away from 

 be axis of rotation, that is, from the vertical line 

 irough the centre of the disc, about which the latter 

 )tates ; hence the disc assumes first the oblique 

 baition c d, and very soon it places itself horizontally, 

 i ef. 



If the disc be suspended from a point near the edge, 

 y simply hooking the wire into a hole punched close 



