XH PREFACE* 



which are the Fibrolite^ Sillimanitc, Finite, Fowlerite, 

 Deweylite, Marmolite, &tc. 



But while I have constantly been concerned to find good 

 reasons for reducing the number of the species, I cannot 

 concur in the proposal of ROSE for uniting Pyroxene and 

 Hornblende, notwithstanding the ingenious reasons he uses 

 in favor of this procedure. To overlook their marked dis- 

 agreement in crystalline structure and to cause them to co- 

 alesce, would shake to the foundations the most secure sup- 

 port of all specific distinction. These species as they oc- 

 cur in the United States do not at all favor his conclusion, 

 inasmuch as they exist together at several places in dolo- 

 mite, preserving their peculiar angles and cleavages. 



The proposed union of Schiller Spar with Pyroxene by 

 KOBELL, is equally in violation of two of the best specific 

 properties in the absence of crystalline form ; viz. specific 

 gravity and hardness. Indeed, all conclusions in case of 

 such complex compounds, drawn from chemical composi- 

 tion, must necessarily be indecisive. 



The introduction of historical matter, as well as a notice 

 of the authorities quoted, has been avoided, excepting 

 only the mention of the author to the systematic name of 

 the species, and occasionally the source whence the angles 

 and the specific gravity have been derived.* To have car- 

 ried these acknowledgments farther, would have swelled 

 the dimensions of the work to an inconvenient size, without 

 having proportionably enhanced its value as an elementary 

 treatise. The more accomplished mineralogist will of 



* The works to which I have been most indebted in the preparation 

 of this Treatise, are mentioned at the conclusion of the preface. 



