I! It had been so often and so confidently said that a definite and constant order of succession existed throughout all rocks, that it had passed into an axiom in geology. Time has not yet dissipated this phantom, though it is gradually fading from among the realities in which the science abounds. As there are few among the dogmas of geologists which have more contributed to impede the progress of investigation, it will be useful to examine the grounds on which it still holds its place. The first step in forming a firm foundation is to remove the tottering materials of the old one. As the doctrine of universal formations is in a great measure implicated in this hypothesis, the same ex amination will serve to try the truth of both. Such also are the catenations of hypotheses, that I must equally notice that branch of the same theory, which asserts that the successive rocks are found to terminate at lower levels above the mean surface of the earth, in an order corresponding to that of their superposition or formation. As also it is held to be unfair to examine part of a theory separated from its connexions with the re mainder, it must be remembered that in this one it is asserted that no extensive denudations of the surface have taken place, particularly in antient times. In strictness of meaning, the term universal forma-