A second edition having been called for, I have endeavoured to render the present volume less unworthy of the public attention by a careful revision and correction of the text, and especially by availing myself of the valuable suggestions of several friends, as well as of those criticisms in periodicals which, from bearing any evidence of honesty, fairness, or ability, seemed deserving of notice. I have thus been led to make many additions, besides numerous lesser alterations; — but, to no modification of the essential argument, which it is hoped those changes will only render more clear and forcible.

My Third Essay more especially, having been publicly adverted to by Mr. W. J. Hamilton, P.G.S. in his anniversary address to the Geological Society, 1856, I have felt it necessary to revise carefully the points in which he has criticised my argument, (though in no instance impugning my facts,) while he has given a flattering general commendation of the object and tenor of my work.

At the same time, I cannot help remarking as curious, how eagerly eminent geologists seem to single out, for the display of their controversial zeal, the obnoxious topic of the Development hypothesis, which, after all, I do not maintain.