40 FERGUSON'S LECTURES. 



g. Take oft' the catgut string E from the great wheel 

 an d the small wheel H, and let the string F remain 



TJi . upon the wheels D and G. Take away also the bearer 



dity of the MX from the whirling-board d, 



vortexes. an ^ instead thereof put the ma- 

 chine AB upon it, fixing this 

 machine to the center of the 

 board by the pins c and d in 

 such a manner, that the end ef may rise above the board 

 to an angle of 30 or 40 degrees. 2 * In the upper side of 

 this machine are two glass tubes a and b, close stopp- 

 ed at both ends ; and each tube is about three quarters 

 full of water. In the tube a is a little quicksilver, which 

 naturally falls down to the end a in the water, because 

 it is heavier than its bulk of water ; and on the tube b 

 is a small cork which floats on the top of the water at 

 e, because it is lighter ; and it is small enough to have 

 liberty to rise or fall in the tube. While the board b, 

 with this machine upon it, continues at rest, the quick- 

 silver lies at the bottom of the tube a, and the cork 

 floats on the water near the top of the tube b. But, 

 upon turning the winch, and putting the machine in 

 motion, the contents of each tube will fly off towards 

 the uppermost ends (which are farthest from the center 

 of motion) the heaviest with the greatest force. There- 

 fore the quicksilver in the tube a will fly off quite to 

 the end /', and occupy its bulk of space there, exclud- 

 ing the water from that place, because it is lighter than 

 quicksilver ; but the water in the tube b flying off to 

 its higher end e, will exclude the cork from that place, 

 and cause the cork to descend towards the lowermost 



Note 24. A better mode of performing this experiment consists in 

 screwing a hollow globe to the whirling table. If this be half filled 

 with water, and a wax taper placed upon a cork float in the center, 

 the water, on being whirled, will rise above its previous level, and 

 occupy the equator of the globe, so that the taper will be seen to burn 

 beneath the water, which will thus form a fluid wall around it several 

 inches in height. 



