10 



other students, in their early efforts, will meet with similar diffi- 

 culties. In short, whenever any doubt has arisen, from whatever 

 cause, having relation to any of the prominent characters em- 

 ployed in these tables, as fusibility, volatility, hardness, specifie 

 gravity, and magnetism, the mineral which is the subject of it, has 

 been repeated to meet all views ; a plan which removes the risk 

 which might otherwise exist of its being omitted in its proper 

 place. 



It is to be hoped that these tables will not suffer condemnation 

 if they should not always conduct the student to a right conclu- 

 sion, for, owing partly to the uncertain nature of the science it- 

 self, partly to the constant discovery of new minerals, and partly 

 to the difficulty or rather impossibility of drawing an artificial 

 distinction, where perhaps no natural one exists, (to say nothing 

 of the compiler's incompetency, which cannot of course be urged 

 in mitigating critical censure,) it is impossible to provide against 

 disappointment in all cases. He must not however conclude that 

 his mineral has been omitted, because a first attempt to identify 

 it should fail. On the contrary, when such a disappointment oc- 

 curs, recourse must be had to the sub-division or section, &c. 

 whose characteristic is next nearest in apparent agreement. It 

 may rarely indeed happen that reference must be had to even a 

 different grand division to the one the mineral seems to belong 

 to, as in the instance of an unobserved though existing volatility 

 the specimen being fusible, in which case it is obvious that failing 

 to find it described in the second grand division, it must be sought 

 for in the first. It is evident also that in all attempts of this na- 

 ture, to be useful, something must be left to the discretion and 

 judgment of the student, to whom I offer the two following closing 

 hints. 1st. It is in mineralogy as in navigation ; he who steers 

 for a certain port, must not expect that all his nautical observa- 

 tions on the voyage will precisely agree with those of the indi- 

 vidual who, has preceded him ; an approximation in the main 

 features of the journals is all that is required, and all that probably 

 will be found. 2nd. If in consulting these tables, he finds him- 

 self embarrassed, he is requested to seek a solution of his diffi- 

 culty, by giving greater prominency to thi. "subordinate charac- 

 teristics. 



