§ 12. NEBULAR THEORY OF THE UNIVERSE. 43 



forest, though unable by a glance to discover that the trees 

 around him ate in a state of progressive change, yet per- 

 ceiving that there are plants in different stages of growth, 

 from the acorn just bursting from the soil to the lofty oak 

 that stands the monarch of the woods, infers, from the 

 succession of changes thus at once presented to his view, 

 the progression of vegetable life, though extending over 

 a period far beyond his own brief existence : — in like 

 manner, the astronomer, by surveying the varied conditions 

 of the heavenly bodies around him, can, by careful induc- 

 tion, determine the nature of those changes, which, as 



Ltgn. 4.— Telescopic appearance of various NRBuia;. 



regards a single nebula, the human mind would otherwise 

 be unable to ascertain. And thus have been traced from 

 nebular masses of absolute vagueness, to others which pre- 

 sent form and structure, the effects of the mysterious law 



