Geology 



hypothesis and others of later date will shortly be 

 discussed. 



We have seen that the Earth on which we live is a 

 comparatively insignificant member of a group of bodies 

 known as the Solar System, which, taken together, form 

 a mere infinitesimal drop in the vast ocean of the visible 

 Universe, our knowledge of whose size is being added 

 to by every improvement in our means of vision. 



Most of the bodies in the Universe must have been 

 in existence for countless ages before the Earth, and 

 perhaps even the Sun, was formed. We must therefore 

 disabuse our minds of any idea that we are the centre 

 and purpose of all things, and that the Sun was made to 

 give us light by day, and the Moon by night, and approach 

 the study of these vastnesses in all humility, considering 

 this fact and that, sifting out truth from mere supposition, 

 and remembering that our theories are only theories, 

 and that if they fail to stand the test of time and the 

 accumulation of new facts, we must be prepared to give 

 them up in favour of others. 



Origin of the Planets. Many years ago Laplace 

 brought forward his great theory of the origin of the 

 Sun and planets, and this, which became known as the 

 Nebular Hypothesis, has remained perhaps in some 

 slightly modified form the accepted view until quite 

 recently, when considerable doubt has been thrown upon 

 it by several astronomers, but particularly by Moulton, 

 a citizen of the United States of America. 



Laplace supposed that all the matter now contained 

 in the Sun and planets was once so hot that it was all in 

 a state of gas, and that in consequence of its great heat 

 it glowed as do some of the nebulae. 



22 



