CIjc '^bnsixal Jformiitioir ai the €nrllj. 



By S. W. TYACK. 



FROM times of remote antiquity wild speoulntions con- 

 cerning the origin and physical form of the earth 

 have been handed down to us, through Hindoo poetry, 

 Egyptian lueroglyphic, and a hundred other channels ; those 

 all showing that i.bo ancient idea was that the earth was 

 flat, or almost so. Careful invcstigatiou pi-ovod, however, 

 to unbiassed minds the fact, now never called in ([uostion, 

 that our world is spherical. 



The nebular hypothesis of Laplace (M6ca,nique G(Uesto, 

 1799) wa,s the first and most successful attempt to explain 

 the actions which called the earth into being. According 

 to his theory, our planet, together with the other members 

 of the solar system, was originally part of the sun, then 

 existing as a huge mass of highly heated vapour revolving 

 with enormous rapidity about its axis. Portions of its 

 gaseous substance it flung off from itself by centrifugal 

 force, and these, under the attractive influence of their 

 parent mass, commenced to circle round it as satellites. 

 This theory is now in the main accepted, though it is con- 

 sidered probable that the eai-th. was not in a gaseous, but 

 liquid condition when it began its separate existence. 



