﻿172 Shepard's Treatise on Mineralogy. 



ity," which obliges me to attempt their vindication from this new 

 attack against their sufficiency; for it may be recollected that the 

 first edition of the treatise brought down upon my characteristic 

 numerous objections from Prof. Del Rio, which I endeavored to 

 controvert in Vol. xxvn, p. 312, of this Journal. In proof of 

 your charge you merely cite the specific character of apatite, fol- 

 lowing it up by this single observation, "This is all the informa- 

 tion which the author thinks necessary to enable the learner to 

 determine this species. 5 ' But in making this charge, you over- 

 look the characters I have also given, in their proper places, for 

 determining the class, order, and section, respectively, to which 

 apatite belongs. You must be aware that my characteristic is 

 no more liable to the charge made, than would that in botany be, 

 because the usual specific character for the Cornus Canadensis 

 (which is "herbaceous, leaves at the top whorled, veiny, involu- 

 cres ovate, acuminate, fruit globose") is insufficient for its deter- 

 mination. In both cases it is alike required that the characters 

 for the higher ideas in the system be first availed of, beginning 



with the most comprehensive, and descending, gradatim, to the 

 species. 



Before then you can affirm that my tables for determination 

 are insufficient, you must show that a student with an individual 

 of apatite in hand, after the use of the appropriate means for learn- 

 ing its form, hardness, and gravity, cannot by the rules given re- 

 fer it to its appropriate species. When this is done, you will 

 have demonstrated the failure of my characteristic in respect to 

 one of its 343 species* 



* I should be less anxious to vindicate the practical part of the treatise from the 

 force of your objection, did I not suppose it to be the most original feature of the 

 production. Indeed, it was the construction of a characteristic analogous to those 

 emp^-ed in zoology a „d botany, which first led me to become a writer on this 

 •^en ; and I may perhaps be allowed here to state the peculiarity of my method, 

 as the subject is one of admitted importance, and respecting which my first re- 

 v^ewer (Del R IO ) remarked--'' the mere attempt to solve a difficult problem is 

 in i se worthy of praise, although the method be complicated, b< ause it can be 

 subsequent y simplified." This method has been gr,ally modified in the second 



on although us principal feature is still retained, which is that of distributing 

 minerals into classpc * n A ~-j . .1 



contents of the ordL ; "! some &* neral 8 ro ' J " ds > ™° *•■ arranging the 



contents of tli« <x r A • g«iiet«« giuuuus, ana men arranging — 



and ending *tb th7hl! J "*" de P endin * »- hardness, placing the softest first 

 scale of M„„. • Sf '' s; lhc haruncs 3 of each being given by the 



in the list tl" a C " immediiltel - v ' to the ««*»« of t"« names for each species 

 in* the -ravitie J T"| g thlS a " d on the ri S ht a S ain > is appended a column contain- 

 00 »o "'e species; and whenever it is supposed that these two prop- 



