132 Rejoinder of Prof. Shepard to Prof. Del Rio. 



pies I have advanced, which are very unaccountably supposed to 

 preclude all regard to a difference of color and lustre between these 

 species. My treatise however is very explicit in the definition of the 

 natural properties of minerals, and in the enumeration of these prop- 

 erties among them. His assertion that I exclude color, fracture and 

 lustre, from the list of natural properties, is farther proof of the hasty 

 manner in which he has considered the subject of his criticisms; and 

 has no better foundation than my having pronounced identical the 

 three varieties of Galena proposed by him as a puzzle for the pu- 

 pil using my book. These varieties were supposed to differ in 

 structure: one of them is crystallized in the form of the cube, an- 

 other massive in large individuals, and the third fine granular. How 

 it is possible for these varieties to be identical in the sense of Natu- 

 ral History, will appear, if any one will peruse the remarks on Iden- 

 tity, ■§> 104, p. 30 of my Treatise, and that without overlooking struc- 

 ture, color and lustre, as natural properties. 



Prof. Del Rio is at a loss to understand how the frequent divis- 

 ion of the species is a consequence, as I had asserted, of providing 

 means for the determination of imperfect minerals. When any one 

 will attempt to secure the object at which I aimed, in a manner 

 equally effectual, he will probably comprehend the nature of the ne- 

 cessity. I intended by the remark, however, simply to say that I 

 could not accomplish the task and avoid such a division. Should it 

 be performed without involving this inconvenience, my assertion will 

 be found untrue, and I shall cheerfully encounter the mortification it 

 may occasion, for the sake of the improvement; though I must de- 

 ny having triplicated (as charged by my reviewer) or even duplicated, 

 the species by the process I have adopted. 



Prof. Del Rio recommended the arrangement of Leucite, Anal- 

 cime and Garnet under a new order, the trapezohedron. I had a 

 right to conclude that this was done as likely, in his opinion, to lead 

 the pupil to the names of these minerals with greater facility than 

 on the disposition I had made of them. In adhering to my arrange- 

 ment, therefore, I do not perceive the impropriety of saying, in re- 

 ply, that it would lead to no confusion, provided I showed satisfac- 

 torily, as I trust I did, that none could occur. 



I notice also with regret, that Prof. Del Rio adheres to his for- 

 mer assertion concerning the determination of Quartz, as included in 

 my order of the rhomboid ; and that he has become so extravagant 

 as to deny that it ever presents itself under the figure of its primi- 



