m 



appal-emment avoit ete faite votre traduction ; je trouvai a raon grand etonne* 

 ment, que rimprimeur avoit fait cette meme faute dans toutes les copies, 

 malgre que roriginal public dans les Transactions Philosophiques avoit ete 

 datte, comme il devoit I'etre, de Janvier 84. Jevous serai tr^s oblige. Mon- 

 sieur, de vouloir bien faire mention de cette meprise dans le caliier prochain de 

 votre Journal. 



Je suis mortifie d'etre dans le cas d'ajouter qu'il s'en faut de beaucoup que la 

 traduction soit exacte ; on a manque le sens en plusieurs endroits. 

 J'ai I'honneur d'etre avec des sentimens distingues. 

 Monsieur, 

 Votre tres humble et tres obeiss' serviteur. 

 A Monsieur T. A. Mongez, le Jeune, &c. &c. &c., 

 Au Bureau du Journal de Physique a Paris. 



EXTRACT FROM A LETTER OF CAVENDISH TO DR. BLAGDEN. 



I have been reading La V. preface. It has only served the more to con- 

 vince me of the impropriety of systematic names in chemistry, & the great 

 mischief which will follow from his scheme, if it should come into use. He 

 says, very justly, that the only way to avoid false opinions is to suppress 

 reasoning as much as possible, unless of the most simple kind, & reduce it 

 perpetually to the test of experiment ; & can anything tend more to rivet a 

 theory in the minds of learners than to found all the names which they are 

 to use upon that theory ? 



But the great inconvenience, is the confusion which will arise from the dif- 

 ferent hypotheses entertained by different people, & the different notions 

 which must be expected to arise from the improvements continually making. 

 If the giving systematic names becomes the fashion, it must be expected that 

 other chemists, who differ from these in theory, will give other names agree- 

 ing with their particular theories, so that we shall have as many different sets 

 of names as there are theories : in order to understand the meaning of the 

 names a person employs, it will be necessary first to inform yourself what 

 theories he adopts. An equal inconvenience, too, will arise from the neces- 

 sity of altering the terms as often as new experiments point out inaccuracies 

 in our notions, or give us further knowledge of the composition of bodies. 

 But to show the ill consequence of what they are about, let them only con- 

 sider what would be the present confusion, if it had formerly been the fashion 

 to give systematic names, & that those names had been continually altered 

 as people's opinions altered. The great inconvenience is the fashion which 

 so much prevails among philosophers, of giving new names whenever they 

 think the old ones improper, as they call it. If a name is in use, & its 

 meaning well ascertained, there is no inconvenience arises from its conveying 

 an improper idea of the nature of the thing ; & the attempting to alter it 

 serves only to make it more difficult to understand people's meaning. 



With regard to distinguishing the- neutral salts of less common use by 

 names expressive of the substances they are composed of, the case is different ; 

 for their number is so great, that it would be endless to attempt to distinguish 



