128 
HISTORY OF THE 
[1850-60 
own speculations and carried with it the hope of further advances. 
The essential unity of nature, a unity assumed in the earlier nebular 
hypothesis, and now actually verified for our own system by the 
demonstration that the sun contained the same elements as the 
earth, was thus in part proved, while the complete proof, though 
difficult, was seen not to be impossible. The extension of this same 
unity to the stellar universe soon followed, and with this extension 
the ancient science of Astronomy entered upon a richer and a 
fuller life.