TERMINOLOGY AND NOMENCLATURE. 249 



(which often depends very much on brevity,) are greatly pro 

 moted by giving distinctive names not to the elements alone, 

 but also to all combinations which are of frequent recurrence. 

 On this occasion I cannot do better than quote from Dr. 

 Whewell* some of the excellent remarks which he has made 

 on this important branch of our subject. 



&quot;The meaning of [descriptive] technical terms can be 

 fixed in the first instance only by convention, and can 

 be made intelligible only by presenting to the senses that 

 which the terms are to signify. The knowledge of a colour 

 by its name can only be taught through the eye. No 

 description can convey to a hearer what we mean by apple- 

 green or French-grey. It might, perhaps, be supposed that, 

 in the first example, the term apple, referring to so familiar 

 an object, sufficiently suggests the colour intended. But it 

 may easily be seen that this is not true ; for apples are of 

 many different hues of green, and it is only by a conventional 

 selection that we can appropriate the term to one special 

 shade. When this appropriation is once made, the term 

 refers to the sensation, and not to the parts of the term ; for 

 these enter into the compound merely as a help to the memory, 

 whether the suggestion be a natural connexion as in apple- 

 green, or a casual one as in French-grey. In order to 

 derive due advantage from technical terms of this kind, they 

 must be associated immediately with the perception to which 

 they belong; and not connected with it through the vague 

 usages of common language. The memory must retain the 

 sensation ; and the technical word must be understood as 

 directly as the most familiar word, and more distinctly. When, 

 we find such terms as tin-white or pinchbeck-broivn, the metallic 

 colour so denoted ought to start up in our memory without 

 delay or search. 



&quot; This, which it is most important to recollect with 

 respect to the simpler properties of bodies, as colour and 

 form, is no less true with respect to more compound notions. 

 In all cases the term is fixed to a peculiar meaning by con- 



* History of Scientific Ideas, ii. 110, 111. 



