as a Branch of Natural History, ^c. 237 



groups of more or less imperfect crystals of a similar sub- 

 stance ; or to those amorphous and compact uncrystallized 

 masses, which, on reasonable induction from analogies, and of- 

 ten from observed facts, may also be considered as groups not 

 only of microscopic, but rather, if we may say so, of molecular 

 crystals, invisible to the eye even armed with the most powerful 

 instruments, such amorphous masses being often formed of a 

 pure homogenous substance, or of individuals of the same che- 

 mical nature (amorphous quartz, chalcedony, limestone, gold, 

 platina, &c.), or being often formed of an intimate mixture of 

 two different substances, or of two sorts of individuals, each of a 

 different chemical nature (agates, jaspers, coloured marbles, &c.) 



Now, in zoology or botany, no one has ever thought of ad- 

 mitting into the classification which comprehends only individuals 

 in their most perfect states, all the mutilated, imperfect, and 

 diseased animals or plants which may occur in nature, still less to 

 give a place to herds of animals, with the animals which compose 

 them, to forests of trees, either of one or of various species, to 

 heaps of decayed wood, with the different species of trees which 

 botany has to describe. Such, however, is what has always been 

 done in mineralogy. 



But here comes the objection, — if we admit in the classification 

 nothing but single and perfect crystals, we shall leave out of the 

 domain of mineralogy, a very great part of what has always been 

 thought to belong to it. Were it so, we maintain that there is 

 now a sufficient quantity of known crystals, differing from each 

 other in shape or substance, to render their consideration and 

 arrangement worthy of the attention of the natural historian. 

 But it will be shewn hereafter, that by a suitable employment 

 of appendices to the classes, families, genera, &c. for minerals 

 differing from the other ones, but not yet found in perfect crys- 

 tals, and, by mentioning historically after the description of 

 €ach genus or of each species, the most ordinary modes in 

 which individuals, small or large, microscopic or molecular, per- 

 fect or mutilated, are assembled together in groups, we shall 

 have in fact enumerated the same bodies which all other works 

 on mineralogy describe ; but only in giving them their proper 

 place, in distinguishing what is to be distinguished, and in pre- 



