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INTRODUCTION. xxiil 
Every step in this research tends to convince us that the succession of strata, when 
clearly shown, furnishes conclusive proofs of the existence of a regular sequence among 
the earlier organisms. We are more and more able, as we advance, to observe that the 
Author of nature, though always working upon the same plan, and producing an infinite 
variety of forms almost incomprehensible to us, has never repeated the same forms in 
successive creations. The various organisms called into existence, have performed their 
parts in the economy of creation ; have lived their period, and perished. This we find to 
be as true among the simple and less conspicuous forms of the palreozoic series, as in the 
more remarkable fauna of later periods. The truth of all these conclusions is now so well 
sustained by the results of scientific investigations, that we regard the history of the past, 
from the dawning of vitality till man assumed the dominion over the whole, as marked in 
certain and intelligible characters, incapable of misinterpretation. 
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