PREFACE

TO THE FIRST EDITION.

NEARLY one-third the present volume appeared a few months ago in the form of a series of sketches in the Witness newspaper. A portion of the first chapter was submitted to the public a year or two earlier, in Chambers' Edinburgh Journal. The rest, amounting to about two-thirds of the whole, appears for the first time.

Every such work has its defects. The faults of the present volume,-faults all too obvious, I am afraid,—would have been probably fewer had the writer enjoyed greater leisure. Some of them, however, seem scarce separable from the nature of the subject: there are others for which, from their opposite character, I shall have to apologize in turn to opposite classes

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PREFACE TO THE FIRST EDITION.

of readers. My facts would, in most instances, have lain closer had I written for geologists exclusively, and there would have been less reference to familiar phenomena. And had I written for only general readers, my descriptions of hitherto undescribed organisms, and the deposits of little-known localities, would have occupied fewer pages, and would have been thrown off with perhaps less regard to minute detail than to pictorial effect. May I crave, while addressing myself, now to the one class and now to the other, the alternate forbearance of each?

Such is the state of progression in geological science, that the geologist who stands still for but a very little must be content to find himself left behind. Nay, so rapid is the progress, that scarce a geological work passes through the press in which some of the statements of the earlier pages have not to be modified, restricted, or extended in the concluding ones. The present volume shares, in this respect, in what seems the common lot. In describing the Coccosteus, the reader will find it stated that the creature, unlike its cotemporary the

Pterichthys, was unfurnished with arms. Ere arriving at such a conclusion I had carefully examined at least a hundred different Coccostei; but the positive evidence of one specimen outweighs the negative evidence of a hundred; and I have just learned from a friend in the north (Mr Patrick Duff of Elgin), that a Coccosteus lately found at Lethen-bar, and now in the possession of Lady Gordon Cumming of Altyre, is furnished with what seem uncouth paddle-shaped arms, that project from the head. All that I have given of the creature, however, will be found true to the actual type; and that parts should have been omitted will surprise no one who remembers that many hundred belemnites had been figured and described ere a specimen turned up in which the horny prolongation, with its inclosed ink bag, was found attached to the calcareous spindle; and that even yet, after many thousand trilobites have been carefully examined, it remains a question with the oryctologist, whether this crustacean of the earliest periods was furnished with legs, or creeped on an abdominal foot, like the snail. I owe to the kindness of Mr Robertson, In

b

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PREFACE TO THE FIRST EDITION.

verugie, the specimen figured in Plate V. fig. 7, containing shells of the only species yet discovered in the Old Red Sandstone of Scotland. They occur in the Lower Formation of the system, in a quarry near Kirkwall, in which the specimen figured, with several others of the same kind, was found by Mr Robertson in the year 1834. In referring to this shell, page 99,* I have spoken of it as a delicate bivalve, much resembling a Venus; drawing my illustration naturally enough, when describing the shell of an ocean deposit, rather from among marine than fluviatile testacea. I have since submitted it to Mr Murchison, who has obligingly written me, that he " can find no one to say more regarding it than that it is very like a Cyclas." He adds, however, that it must be an ocean production notwithstanding, seeing that all its cotemporaries in England, Scotland, and Russia, whether shells or fish, are unequivocally marine.

With the exception of two of the figures in Plate IX., the figures of the Cephalaspis and the Holoptychius, and one of the sections in the * Page 123 of the present edition.

Frontispiece, section 2, all the prints of the volume are originals. To Mr Daniel Alexander of Edinburgh,—a gentleman who to the skill and taste of the superior artist, adds no small portion of the knowledge of the practical geologist, I am indebted for several of the drawings that of fig. 2 in Plate V., fig. 1 in Plate VI., fig. 2 in Plate VIII., and fig. 3 and 4 in Plate IX. I am indebted to another friend for fig. 1 in Plate VII. Whatever defects may be discovered in any of the others must be attributed to the untaught efforts of the writer, all unfamiliar hitherto with the pencil, and with by much too little leisure to acquaint himself with it now.