THE PROBABLE AGE OF THE WORLD. 661 



to have taken place in the planets. The experiment has siuce been 

 several times repeated. When the rotation becomes very rapid, the 

 figure becomes more oblately spheroidal, then hollows out above and 

 below round the axis of rotation, stretches out horizontally until 

 finally the outside layer of oil abandons the mass and becomes trans- 

 formed into a perfectly regular ring. After a little while the ring of 

 oil, losing its own motion, gathers itself once more into a sphere. As 

 often as the experiment is repeated the ring thrown off immediately 

 takes the globular form. These are seen to assume at the instant of 

 their formation a movement of rotation upon themselves, which takes 

 place in the same direction as that of the ring. Moreover, as the 

 ring at the instant of its rupture had still a remainder of velocity, 

 the spheres to which it has given birth tend to fly off at a tangent ; 

 but, as on the other side, the disk, turning in the alcoholic liquor, 

 has impressed on the liquor a movement of rotation, the spheres are 

 carried along and revolve for some time round the disk. Those 

 which revolve at the same time upon themselves " present the curi- 

 ous spectacle of planets revolving at the same time on themselves 

 and in their orbit." Another curious result is almost always exhibited 

 in this experiment. Besides three or four large spheres into which 

 the ring resolves itself, there are almost always two or three very 

 small ones which may thus be compared to satellites. The experi- 

 ment presents, therefore, an image in miniature of the formation of 

 the planets, according to the hypothesis of Laplace, by the rupture 

 of the cosmical rings attributable to the condensation of the solar 

 atmosphere. 



Modern discoveries carry the matter on much further. Recent 

 investigations into the doctrine of the conservation of energy have 

 shown the generation of cosmical heat. The amount of force com- 

 prised in the universe, like the amount of matter contained in it, is a 

 fixed quantity, and to it nothing can either be added or taken away. 

 It is, therefore, constantly undergoing change from one form to an- 

 other. If it ceases in one form it is not destroyed, it is converted. 

 The blow of a hammer on an anvil sets a certain amount of energy 

 in motion. The anvil stops the blow, but the force changes into 

 heat. Hammer a nail, and it will burn your fingers. Apply a brake 

 to a wheel, and you will stop the motion, but the force will be changed, 

 into heat, which will burn you if you touch the brake. Measure the 

 hammered nail, and you find that it has expanded by the vibration 

 of its particles ; heat it still more, and the particles will overcome the 

 attraction of cohesion and revolve about each other, that is, they will 

 become molten ; heat them still more, and they will assume the vapor- 

 ous or gaseous form. Xow, seeing that motion was convertible into 

 heat, and heat into motion, it became an object of inquiry what was 

 the exact relation between the two. Dr. Mayer, in Germany, and Dr. 

 Joule, in England, set themselves to the solution of this problem. By 



