LITHOLOGY. 241 
this work, it will be noticed that a large number and a large variety of 
rocks have been classified under a small number of heads. The effort 
has been made to show that by the introduction of the microscopic 
method, many of the difficulties which have complicated the study of 
our crystalline rocks disappear, while its interest and beauty are 
increased; for not only are the compositions and present conditions 
of the rocks easily determined, but the thin sections contain a chapter 
of their histories and a record of the changes through which they 
have passed. I wish to recall again the scope of the work. It has 
not aimed to be a description of the rocks of the state, but has rather 
aimed to be a study of specimens which have been carefully selected, 
with the hope that all our important rocks would be represented 
among them. As, now, each new section that has been prepared has 
almost always presented some new features, I am certain that those 
people in the state who may be encouraged to pursue these studies 
will find in the specimens they examine, even from the very ground 
that I have traversed, as many other things of interest as have been 
here developed. New Hampshire is grand in her rocks, and it has 
been an object of this treatise to show that the beauty of them is 
not confined to those modes of arrangement which cause our state to 
be filled with the most picturesque scenery that this part of the coun- 
try has to offer, but that our rocks, in their minutest structures, are 
beautiful, and possess features which, though small, are of remarkable 
interest and of geological significance. 
VOL. IV. 31 
