162 CORRELATION OF PHYSICAL FORCES, 



same category. What is called voltaic electricity might equally, 

 perhaps more appropriately, be called voltaic chemistry. I 

 mention these facts to show that the distinction in the name 

 may frequently be much greater than the distinction of the 

 subject which it represents, and vice versa, not as at all object- 

 ing to the received nomenclature on these points ; nor do I 

 say it would be advisable to depart from it : were we to do 

 so, inevitable confusion would result, and objections equally 

 forcible might be found to apply to our new terminology. 



Words, when established to a certain point, become a part 

 of the social mind ; its powers and very existence depend 

 upon the adoption of conventional symbols ; and were these 

 suddenly departed from, or varied, according to individual 

 apprehensions, the acquisition and transmission of knowledge 

 would cease. Undoubtedly, neology is more permissible in 

 physical science than in any other branch of knowledge, 

 because it is more progressive ; new facts or new relations 

 require new names, but even here it should be used with great 

 caution. 



Si forte necesse est 



Indiciis monstrare recentibus abdita rerum, 

 Fingere cinctutis non exaudita Cethegis 

 Continget ; dabiturque licentia, sumpta pudenter. 



Even should the mind ever be led to dismiss the idea of 

 various forces, and regard them as the exertion of one force, 

 or resolve them definitely into motion, still we could never 

 avoid the use of different conventional terms for the different 

 modes of action of this one pervading force. 



Reviewing the series of relations between the various forces 

 which we have been considering, it would appear that in many 

 cases where one of these is excited or exists, all the others are 

 also set in action : thus, when a substance, such as sulphuret 

 of antimony, is electrified, at the instant of electrisation it 

 becomes magnetic in directions at right angles to the lines of 

 electric force ; at the same time it becomes heated to an extent 

 greater or less according to the intensity of the electric force. 

 If this intensity be exalted to a certain point the sulphuret 

 becomes luminous, or light is produced : it expands, conse- 

 quently motion is produced ; and it is decomposed, therefore 



