PREFACE. Xiil. 
sistently together,—with what propriety I have added this 
portion of the great chain of beings and of truths to its 
major part as it now exists, I leave the critical reader to 
determine. Theoretic knowledge is the great end of 
science, and while a number of its followers are loud in 
their denunciations of“ theory and speculation,’ and in their 
commendation of the acquisition of facts, they are mean- 
while insensibly cultivating the former in the accustomed 
manner. A man cannot well regard a fact without con- 
sidering it in its relative character to some other, and with 
respect to its influence on some theory or deduction however 
vague, limited, and unscientific ; theory is the pivot or 
centre on which the utility of all scientific knowledge, 
more or less revolves, itis the fruit borne on the branches 
of the tree formed by the aggregate of facts. Is a man 
actually substantially wiser because he knows the number, 
the names, the qualities of all the rocks which occur in our 
district ? Is a man really wiser if he know the names of 
our migrating birds, and can discriminate one from another ? 
I greatly question it ; the knowledge which these things 
convey rests in their philosophy, and that embraces in the 
one case a theoretic consideration of the origins, the ages, 
the order of deposition, the probable intermixtures and 
chemical actions of the formations of the ancient epochs, 
the probable condition of the beings which resided on the 
earth or in its seas in those zeras, and the mode in which 
they were destroyed and impacted in their present sites, 
and so forth, while in the other, its philosophy includes a 
whole train of enquiries equally congenial to the minds of 
rational creatures, and honorable to those who systemati- 
cally pursue them,—such are the physical powers of birds, 
their contrivances to shorten their migratory routes, the 
