x PREFACE. 
The phenomena of nature are ever before us, and their 
variety is without limit. One, therefore, who has 
pursued the study of nature throughout his course of 
education will never be at a loss for fresh material for 
observation. Especially is this true of that science to 
which the pupil is introduced in the present work. 
The only other consideration which I shall present 
is the moral effect of the early study of natural science. 
Ever varying views of the traces of the wisdom, power, 
and goodness of the Deity can not fail to lodge in the 
young mind sentiments and opinions, which will be 
apt to forestall successfully the arguments of skep- 
ticism that may be presented in after years. No 
mere general views can do this, though they are often 
relied upon; but the actual and definite knowledge 
which study and observation give is required to effect 
it. This benefit can hardly be overestimated. The 
preoccupation of the mind by clear and abundant evi- 
dence is a preventive measure of vast importance. 
Better is it thus to shut out error, than to permit its 
admission and then attempt to cast it out. 
The author has in the course of preparation books 
on some of the other natural sciences—Natural Philos- 
ophy, Chemistry, ete.—having the same general plan 
which has been adopted in this work. His object is 
to aid in the introduction of these studies into the 
common school, as well as the academy and college. 
The books which I have already prepared have 
been used in some schools as reading-books at the 
same time that they are used for study, and with 
marked success. The plan adopted is this. The 
class read the lesson, the teacher remarking upon it 
so far as is thought proper; and then the recitation is 
