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TO THE READER.

Of the twelve following Lectures, four (the First, Second, Fifth, and Sixth) were delivered before the members of the Edinburgh Philosophical Institution (1852 and 1855). One (the Third) was read at Exeter Hall before the Young Men's Christian Association (1854), and the substance of two of the others (the Eleventh and Twelfth) at Glasgow, before the Geological Section of the British Association (1855). Of the five others, — written mainly to complete and impart a character of unity to the volume of which they form a part, - only three (the Fourth, Seventh, and Eighth) were addressed viva voce to popular audiences. The Third Lecture was published both in this country and America, and translated into some of the Continental languages. The rest now appear in print for the first time. Though their writer has had certainly no reason to complain of the measure of favor with which the read or spoken ones have been received, they are perhaps all better adapted for perusal in the closet than for delivery in the public hall or lecture-room; while the two concluding Lectures are mayhap suited to interest only geologists who, having already acquainted themselves with the generally ascertained facts of their science, are curious to cultivate a further knowledge with such new facts as in the course of discovery are from time to time added to the common fund. In such of the following Lectures as deal with but the established geologic phenomena, and owe whatever little merit they may possess to the inferences drawn from these, or on the conclusions based upon them, most of the figured illustrations, though not all, will be recognized as familiar: in the two concluding Lectures, on the contrary, they will be found to be almost entirely new. They are contributions, representative of the patient gleanings of years, to the geologic records of Scotland; and exhibit, in a more or less perfect state, no inconsiderable portion of all the forms yet detected in the rocks of her earlier Palæozoic and Secondary floras.

It will be seen that I adopt, in my Third and Fourth Lectures, that scheme of reconciliation between the Geologic and Mosaic Records which accepts the six days of creation as vastly extended periods; and I have been reminded by a somewhat captious critic that I once held a very different view, and twitted with what he terms inconsistency. I certainly did once believe with Chalmers and with Buckland that the six days were simply natural days of twenty-four hours each, - that they had compressed the entire work of the existing creation, and that the latest of the geologic ages was separated by a great chaotic gap

from our own. My labors at the time as a practical geologist had been very much restricted to the Palæozoic and Secondary rocks, more especially to the Old Red and Carboniferous Systems of the one division, and the Oolitic System of the other; and the long extinct organisms which I found in them certainly did not conflict with the view of Chalmers. All I found necessary at the time to the work of reconciliation was some scheme that would permit me to assign to the earth a high antiquity, and to regard it as the scene of many succeeding creations. During the last nine years, however, I have spent a few weeks every autumn in exploring the later formations, and acquainting myself with their peculiar organisms. I have traced them upwards from the raised beaches and old coast lines of the human period, to the brick clays, Clyde beds, and drift and boulder deposits of the Pleistocene era, and again from these, with the help of museums and collections, up through the mammaliferous crag of England, to its Red and its Coral crags. And the conclusion at which I have been compelled to arrive is, that for many long ages ere man was ushered into being, not a few of his humbler contemporaries of the fields and woods enjoyed life in their present haunts, and that for thousands of years anterior to even their appearance, many of the existing molluscs lived in our seas. That day during which the present creation came into being, and in which God, when he had made "the beast of the earth after his kind, and the cattle after their kind,” at length terminated the work by moulding a creature in his own image, to whom he gave dominion over them all, was not a brief period of a few hours' duration, but extended over mayhap millenniums of centuries. No blank chaotic gap of death and darkness separated the creation to which man belongs from that of the old extinct elephant, hippopotamus, and hyæna; for familiar animals such as the red deer, the roe, the fox, the wild cat, and the badger, lived throughout the period which connected their times with our own; and so I have been compelled to hold, that the days of creation were not natural, but prophetic days, and stretched far back into the bygone eternity. After in some degree committing myself to the other side, I have yielded to evidence which I found it impossible to resist; and such in this matter has been my inconsistency,

,- an inconsistency of which the world has furnished examples in all the sciences, and will, I trust, in its onward progress, continue to furnish many more

EDINBURGH, DECEMBER, 1856.

[The last procfs of this preface were despatched by the Author to his printer only the day before that melancholy termination of his life, the details of which will be found in the “MEMORIALS” following. - Am. PUBLISHERS.)

List of Pllustrations.

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A Restoration of Sphenopteris affinis (Frontispiece). 1. The Genealogy of Plants, 2. Cyclopteris Hibernicus, 3. Conifer of the Lower Old Red Sandstone, . 4. The Genealogy of Animals, 5. Oldhamia antiqua (oldest known Zoophyte), 6. Palæochorda minor, . 7. Lycopodium clavatum, 8. Equisetum fluviatile, 9. Osmunda regalis (Royal Fern), 10. Pinus sylvestris (Scotch Fir), 11. Calamite? of the Lower Old Red Sandstone, 12. Lycopodite? of the Lower Old Red Sandstone, 13. Fern? of the Lower Old Red Sandstone, 14–19. Ferns of the Coal Measures, 20. Altingia excelsa (Norfolk Island Pine), 21. East Indian Fern (Asophila perrotetiana), 22. Section of Stem of Tree-Fern (Cyathea), 23–25. Lepidodendron Sternbergii, 26. Calamites Mougeotii, 27. Sphenophyllum dentatum, 28. Sigillaria reniformis, 29. Sigillaria reniformis (nat. size), 30. Sigillaria pachyderma, 31. Stigmaria ficoides, 32. Favularia tessellata, 33 Lepidodendron obovatum, 34. Cycas revoluta, 35. Zamia pungens, 36. Zamia Feneonis, 37. Mantellia nidiformis,

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