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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.
