636 CROSS, 1DDINGS, PIRSSON, WASHINGTON 



Habit. — In order to express the fact that one rock resembles 

 in general appearance another well-known rock by exhibiting 

 some of its characteristic features without being identical in 

 composition or mode we propose to use the term habit, formerly 

 in constant requisition among petrographers. The features of a 

 rock characterizing its habit may be both textural and mineral. 

 For example : one rock may be porphyritic, with a dark-colored, 

 aphanitic groundmass, and the phenocrysts rhombic feldspars. 

 Another rock may have these features, but belong to a chem- 

 ically different magma. The two may be said to have the same 

 habit. And the second may be sufficiently described by giving 

 its proper magmatic name qualified by an adjective indicating 

 the habit of the first rock. 



To accomplish this we propose that the habit of a rock be 

 expressed by a word formed similarly to one expressing type 

 but with the termination -oid. The root of the word is to be 

 taken from some geographical locality. It may be the same as 

 one used for a type, since a common type rock may be one whose 

 habit will often be used in describing another, less common, 

 rock. 



Thus a particular form of rock belonging to the Order 

 russare, of the persalanes, may constitute the tingual type, with 

 definite norm, mode, and texture ; while a somewhat similarly 

 appearing rock belonging to the Order norgare, of the dosalane 

 Class may possess a tinguoid habit. 



The habital qualifier may be applied to a magmatic name of any 

 systematic division, since it does not specify the composition of 

 a rock. Thus we may describe a rock as a tinguoid dosalane, or 

 a tinguoid norgare, a tinguoid laurdalase, etc. There may be 

 tinguoid persalanes and salfemanes. 



It is obvious that, with the use of types and habits, the 

 nomenclature will tend to become binomial, and hence much 

 more easy of application than in the present systems, or in the 

 full one proposed here. It will, however, differ radically from 

 the binomial nomenclature in use in the organic sciences, since 

 the habital qualifier will not correspond to the specific terms of 



