MICA AND THE MICA MINES. 653 



gible tiling to "be a Phegopteris dryopteris, and in most cases goes 

 away perfectly satisfied. Occasionally, however, it does occur to 

 him that he is just as wise as he was before, and not one whit 

 more so. These are not imaginary cases. It was from being 

 several times in the position of the non-botanical member that led 

 me to reflect that the function of a definition is to define. Now, 

 who is to blame for this extreme haziness of intercourse, Linnseus 

 or his friend ? Perhaps both of them. 



In the face of these experiences, it is difficult to answer the 

 seemingly simple question, " What is mica ? " To say that it is a 

 unisilicate in which the predominant protoxide is potash and the 

 predominant sesquioxide is alumina, is to say something that is 

 fairly unintelligible to those who are not chemists, and something 

 which even to those who are chemists gives only a bit of classifi- 

 cation and partial composition, but in reality explains little about 

 the mineral itself. Any answer that we can give is only satis- 

 factory until we learn to push the question a step further. Gau- 

 tama well expresses the difficuly when he says in the Light of 



Asia: 



" Shall any gazer see with mortal eyes, 

 Or any searcher know by mortal mind, 

 Veil after veil will lift hut there must be 

 Veil upon veil behind." 



But this is a difficulty which besets us on all sides when we 

 question any of the thousand and odd minerals described in Dana, 

 or for that matter when we put questions to Nature in any direc- 

 tion. 



In the case of minerals we know enough to perceive that there 

 is much yet unexplained which lies well within the domain of the 

 knowable. But it is as difficult for the mineralogist as for the 

 botanist to give even fair descriptions of the objects of his study, 

 for he so soon runs against his brick wall when he comes to talk 

 about either the physical or chemical properties of minerals. The 

 processes of crystallization are as profound a mystery as the life 

 process itself. "We are much in the position of the zoologists of 

 the last century, who named and labeled their specimens without 

 knowing the significance of their relationship. 



The name mica is not that of a single mineral, but is a family 

 cognomen, which includes a number of varieties. With the out- 

 ward attributes of the family we are all more or less familiar, for 

 under the common name of isinglass it forms a small part of 

 the stock in trade of every householder. The family is one of 

 some importance in the mineralogical hierarchy. All are shining 

 members, and are alike in splitting into extremely thin leaves or 

 plates ; in being more or less transparent ; in being highly elastic ; 

 and in having certain ingredients in common. There are seven 



