144 POPULAR LECTURES AND ADDRESSES. 



motion ; and showed experiments with gyrostats 

 in which upright positions, utterly unstable with- 

 out rotation, were maintained with a firmness and 

 strength and elasticity such as might be by bands 

 of steel. A flexible endless chain seemed rigid 

 when caused to run rapidly round a pulley, and 

 when caused to jump off the pulley, and let fall 

 to the floor, stood stifflly upright for a time till 

 its motion was lost by impact and friction of its 

 links on the floor. A limp disc of indiarubber 

 caused to rotate rapidly seemed to acquire the 

 stiffness of a gigantic Rubens hat-brim. A little 

 wooden ball, which when thrust down under still 

 water jumped up again in a moment, remained 

 down as if embedded in jelly when the water 

 was caused to rotate rapidly, and sprang back, 

 as if the water had elasticity like that of jelly, 

 when it was struck by a stiff wire pushed down 

 through the centre of the cork by which the glass 

 vessel containing the water was filled. Lastly, large 

 smoke rings discharged from a circular or elliptic 

 aperture in a box were rendered visible, by aid of 

 the electric light, in their progress through the 



