HOMOLOGIES. 201 
CHAPTER XIII. 
HOMOLOGIES. 
Ir may seem to some of my readers that I 
have wandered from my subject and forgotten 
the title of these articles, which purport to be a 
series of papers on “* Methods of Study in Natu- 
ral History.”’ But some idea of the progress of 
Natural History, of its growth as a science, of 
the gradual evolving of general principles out of 
a chaotic mass of facts, is a better aid to the stu- 
dent than direct instruction upon special modes 
of investigation ; and it is with the intention of 
presenting the study of Natural History from 
this point of view that I have chosen my title. 
I have endeavored thus far to show how scien- 
tific facts have been systematized so as to form a 
classification that daily grows more true to Na- 
ture, in proportion as its errors are corrected by 
a more intimate acquaintance with the facts ; but 
I will now attempt a more difficult task, and try 
to give some idea of the mental process by which 
facts are transformed into scientific truth. I fear 
that the subject may seem very dry to my read- 
9 * 
