Rivieio of Cleaveland^s Mineralogy, 43 



lography, physical and external characters, and chemical 

 characters. 



He has given a clear view of the Abbe Haiiy's curious dis- 

 coveries regarding the six primitive figures or solids which 

 form the bases of all crystals — the three integrant particles or 

 molecules which constitute the primitive forms, and of the 

 theory by which it is shown how the immensely numerous 

 and diversified secondary or actual forms arise out of these 

 few elementary figures. 



This is certainly one of the most singular and acute disco- 

 veries of our age. It is true, there is a difference of opinion 

 among mineralogists as to the practical use of crystallography 

 in the discrimination of minerals. Some dwell upon it with 

 excessive minuteness, and others seem restless and impatient 

 of its details. The truth seems to be, that those who under- 

 stand it, derive from it (wherever it is applicable) the most 

 satisfactory aid ; and it requires only a moderate knowledge of 

 geometry to understand its principal outlines. On the other 

 hand, it is no doubt possible, in most instances, to dispense 

 with its aid, and to discriminate minerals by their other pro- 

 perties. 



Of the external and physical characters of Mr. Werner, Mr. 

 Cleaveland has given a clear account, combining into the same 

 view the fine discriminations of the French authors, particu- 

 larly regarding refraction, phosphorescence, specific gravity, 

 electricity, chatoyement, and magnetism. The same may be 

 said of the chemical characters. We do not know a more 

 satisfactory and able view of the characters of minerals than 

 Professor Cleaveland has exhibited. 



We would however ask, whether, in enumerating the kinds 

 of lustre, the term adamantine should not be explained, as it is 

 not understood by people in general, while the terms denoting 

 the other kinds are generally intelligible ; whether in the enu- 

 meration of imitative forms, lenticular and acicular should not 

 rather be referred to the laws of crystallization ; whether reni- 

 form and mamillary are synonymous ; whether sandstone, as 

 being a mfere aggregate oi fragments, is a good instance of the 

 ^ramdar fracture ; whether in its natural state (at least the 



