a, ee PREFACE. 
general principles of the science remain uniform, ve receive some- 
times a clearer, sometimes a somewhat different, light from the 
rocks of other countries than our own. If from these references he is 
induced to turn to the labours of our fellow-workers on the Continent, 
and to share my respect and admiration for them, a large part of 
my design will have been accomplished. If, further, he is led to 
study with interest the work of our brethren across the Atiantic, and 
to join in my hearty regard for it and for them, another important 
section of my task will have been fulfilled. And if in perusing 
these pages he should find in them any stimulus to explore nature 
for himself, to wander with the enthusiasm of a true geologist over 
the length and breadth of his own country, and, where opportunity 
offers, to extend his experience and widen his sympathies by ex- 
ploring the rocks of other lands, the remaining and chief part of my 
aim would be attained. 
Geology is so progressive a science, and the amount of literature 
devoted to its illustration is so constantly increasing, that in a work 
of such proportions as the present it must necessarily happen that 
between the printing off of the earlier portions and the final publi- 
cation of the book, memoirs appear which the author regretfully 
finds himself precluded from using as he would gladly have done 
had they been earlier available. As examples in the present instance, - 
I may refer to Mr. Darwin’s ‘ Vegetable Mould,’ Mr. Fisher’s ‘ Physics 
of the Earth’s Crust,’ Mr. Judd’s ‘ Volcanoes,’ Dr. Tietze’s ‘ Memoir 
on Lemberg’ (Jahrb. K.K. Geolog. Reichsanst. xxxil. 1882), and Mr. 
Reusch’s paper on ‘ Upper Silurian Fossils among the Metamorphic 
Rocks of Bergen’ (Christiania, Universitetsprogram. 1882). 
The illustrations of Fossils in Book VI. have been chiefly drawn 
by Mr. George Sharman; a few by Mr. B. N. Peach, and one or two 
by Dr. R. H. Traquair, F.R.S., to all of whom my best thanks are 
due. The publishers having become possessed of the wood-blocks 
of Sir Henry De la Beche’s ‘Geological Observer,’ I gladly made - 
use of them as far as they could be employed in Books III. and LY. 
Sir Henry’s sketches were always both clear and artistic, and I 
hope that students will not be sorry to see some of them revived. 
They are indicated by the letter (B). The engravings of the micro- — 
scopic structure of rocks are from my own drawings, and I have 
also availed myself of materials from my sketch-books. The 
frontispiece is a reduction of a drawing by Mr. W. H. Holmes, 
whose pictures of the scenery in the Far West of the United States 
are by tar the most remarkable examples yet attained of the union of 
artistic effectiveness with almost diagrammatic geological distinctness 
and accuracy. Captain Dutton, of the Geological Survey of the United 
States, furnished me with this drawing and also requested Mr. Holmes 
to make for me the cafon-sections given in Book VII. ‘To both of 
these kind friends I desire to acknowledge my indebtedness. 
28, JERMYN STREET, LONDON, 
12th June, 1882. 
