PREFACE. Xlll 



In my Essay entitled Erste Ideen zur Theorie des Lichts, der 

 Finsterniss, der Farben und der Warme ; Jena bey Frommann, 

 1808, 4to, I pointed out, that the Light could be nothing but a 

 polar tension of the aether, evoked by a central body in antagonism 

 with the planets ; and that the Heat were none other than the 

 motion of this aether. This doctrine appears to be still in a state of 

 fermentation. 



In my Essay entitled Grundzeichnung des natiirlichen Systems 

 der Erze ; Jena bey Frommann, 1809, 4to, I arranged the Ores 

 for the first time, not according to the Metals, but agreeably to their 

 combinations with Oxygen, Acids, and Sulphur, and thus into 

 Oxyden, Halclen, Glanzen, and Gediegenen. This has imparted to 

 the recent science of Mineralogy its present aspect or form. 



In the first edition of my Lehrbuch der Naturphilosophie, 

 1810 and 1811, I sought to bring these different doctrines into 

 mutual connexion, and to show, forsooth, that the Mineral, Vege- 

 table, and Animal classes are not to be arbitrarily arranged in 

 accordance with single or isolated characters, but to be based upon 

 the cardinal organs or anatomical systems, from which a firmly 

 established number of classes must of necessity result ; moreover, 

 that each of these classes commences or takes its starting-point 

 from below, and consequently that all of them pass parallel to each 

 other This parallelism is now pretty generally adopted, at least--in 

 England and France, though with sundry modifications, which, 

 from the principles being overlooked or neglected, are based at ran- 

 dom, and are not therefore to be approved of. As in chemistry, 

 where the combinations follow a definite numerical law, so also in 

 Anatomy the organs, in Physiology the functions, and in Natural 

 History the classes, families and even genera of Minerals, Plants 

 and Animals, present a similar arithmetical ratio. The genera are 

 indeed, on account of their great number and arbitrary erection to 

 the rank whose title they bear, not to be circumscribed or limited in 

 every case with due propriety, nor brought into their true scientific 

 place in the system ; it is nevertheless possible to render their 

 parallelism with each other clear, and to prove that they by no 

 means form a single ascending series. If once the genera of 

 Minerals, Plants and Animals come to stand correctly opposite each 

 other, a great advantage will accrue therefrom to the science of 

 Materia Medica ; for corresponding genera will act specifically upon 

 each other. 



These principles, which I have now carried out into detail, were 



