4 HISTORY OF CHEMISTRY. [LECTURE I. 



announced by some one, or often by several persons simul- 

 taneously. Further, by the study of history our faith in 

 authority is diminished a faith which produces pernicious 

 effects by obstructing the way for any original development of 

 the individual. 



On the other hand we also learn, it is true, that theories 

 are necessary for further development ; and that, although the 

 actual teachings of science may lie in the facts, the real intel- 

 lectual significance can only be acquired by connecting isolated 

 observations by means of hypotheses ; so that the present posi- 

 tion consists far more in the mode of explaining observations 

 than in the observations themselves. 



When the point of view which I regard as essential for our 

 subject is thus made clear, it will be understood that I direct 

 my attention principally to theories, and only take cognisance 

 of those experimental investigations which have contributed to 

 the establishment or the overthrow of general views. 



The early history of our science has been treated most 

 excellently, and in detail, by Hermann Kopp ; and for this 

 reason I confine myself to the last hundred and twenty years ; 

 that is, to the period of modern chemistry, or to that of quan- 

 titative investigations. 1 I must not omit, . however, to give a 

 short description of the views which prevailed in chemistry 

 prior to Lavoisier. 



The influence of the Greeks upon art and literature, on 

 their reawakening after several hundred years' sleep, is so well 

 known that it need not surprise us if we recognise a similar 

 influence in science also. The four elements of Empedocles, 

 water, earth, fire, and air, which, in Aristotle's system, are repre- 

 sentative of the four cardinal properties, moist, dry, hot, and 

 cold, are quite familiar. I attach great importance to finding 

 fire here amongst the elements, and to seeing it regarded as a 

 material substance. As we shall learn in what follows, the first 

 chemical theories have reference to the phenomena of combus- 



1 Kopp's Entwickelung der Chemie in der neueren Zeit (1873) appeared 

 five years after the publication of the first German edition of this book. 



