PREFACE TO THE FIRST EDITION.

Nearly one-third of the present volume appeared a fewmonths ago, in the form of a series of sketches in the Witnessnewspaper. A portion of the first chapter was submitted tothe public a year or two earlier, in “ Chambers’ EdinburghJournal.” The rest, amounting to about two-thirds of thewhole, appears for the first time.

Every such work has its defects. The faults of the pre-sent volume,—faults all too obvious, I am afraid,-—wouldhave been probably fewer had the writer enjoyed greaterleisure. Some of them, however, seem scarce separable fromthe nature of the subject; there are others for which, fromtheir opposite character, I shall have to apologise, in turn,to opposite classes of readers. My facts would, in most in-stances, have lain closer had I written for geologists exclu-sively, and there would have been less reference to familiarphenomena. And had I written for only general readers,my descriptions of hitherto undescribed organisms, and thedeposits of little known localities, would have occupied fewerpages, and would have been thrown off with perhaps less re-gard to minute detail than to nictorial effect May I crave,