INTRODUCTION. 5 
he has employed, and so many of whose observations he has repeated. 
He hopes only to have added some facts of value from our country to 
the general store. 
I wish to thank Prof. Hitchcock for the opportunities and facilities that 
he has given to me for the prosecution of these studies. The people of 
the state are much indebted to Prof. George J. Brush, of New Haven, 
who has so kindly allowed his instruments and books, as well as all the 
resources of the scientific school, to be freely used for the benefit of the 
survey. I wish to render my personal thanks to my instructors,—Pro- 
fessors Brush and Dana, of New Haven, and Prof. A. von Lasaulx, of 
Breslau. The friendliness that these gentlemen have shown the writer 
made his studies peculiarly pleasant. 
In the pages that follow, I think all the things that are referred to and 
not explained will be found in Prof. Dana’s Mineralogy. I have, how- 
ever, been requested, by the chief of the survey, to elucidate my refer- 
ences to microscopic mineralogy, in order to make the work clearly intel- 
ligible to all. This will explain the introduction of so much elementary 
material upon this subject. 
MetTuops or Stupy. 
In the study of our minerals and rocks, only simple means and appli- 
ances have been employed. Many most complicated instruments, and all 
the appliances of large laboratories, are often employed in such studies ; 
but the means and instruments to which references are made in this 
work are within the reach of all. 
It is unnecessary to say anything about the chemical study. Refer- 
ences are sometimes made to the common blow-pipe tests. All the in- 
struments and reactions that are mentioned will be found described in 
any work on the blow-pipe.* In regard to the physical study it is also 
almost unnecessary to speak, since we have excellent treatises upon 
physical mineralogy; and the new work by Mr. E. S. Dana contains 
a very clear and concise statement of all those optical principles that 
are employed in investigating minerals. It is only because the applica- 
* See a treatise upon the blow-pipe, by Prof. Geo. J. Brush, published by Wiley & Son, New York. 
+A Text-Book of Mineralogy, E.5. Dana. Wiley & Son. 
