PREFACE. 
* The last or sixth edition of my “ Elements of Geology ” 
was already put of print before the end of 1868 , in which 
year I brought out the tenth edition of my Principles of 
Geology.” 
In writing the last-mentioned work I had been called upon 
to pass in review almost all the leading points of specula¬ 
tion and controversy to which the rapid advance of the sci¬ 
ence had given rise, and when I proposed to bring out a 
new edition of the “ Elements ” I \Yas strongly urged by my 
friends not to repeat these theofetical discussions, but to 
confine myself in the new treatise to those parts of the “ Ele¬ 
ments ” which were most indispensable to a beginner. This 
was to revert, to a certain extent, to the original plan of 
the first edition; but I found, after omitting a great number 
of subjects, that the necessity of bringing up to the day those 
which remained, and adverting, however briefly, to new dis¬ 
coveries, made it most difficult to confine the proposed 
abridgment within moderate limits. Some chapters had to 
be entirely recast, some additional illustrations to be intro¬ 
duced, and figures of some organic remains to be replaced 
by new ones from specimens more perfect than those which 
had been at my command on former occasions. By these 
changes the work assumed a form so different from the sixth 
edition of the “ Elements,” that I resolved to give it a new 
title and call it the “ Student’s Elements of Geology.” 
In executing this task I have found it very difficult to 
meet the requirements of those who are entirely ignorant of 
the science. It is only the adept who has already overcome 
