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. 



Methods of Study. 



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 f 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, pubHshed by Wiley & Son, New York, 

 t^ Text-Book of Mineralogy. E. S. D.ina. Wiley & Son. 



