2 INTRODUCTION. 



The theory of heat and that of electricity belong either to Dynamics 

 or Chemistry, according to the point of view in which they are consi- 

 dered. 



The ruling method in all the branches of general physics consists in 

 insulating bodies, reducing them to their greatest simplicity by bring- 

 ing each of their properties separately into action, either by reflection 

 or experiment, and by observing or calculating the results ; and finally, 

 by generalising and connecting the laws of these properties, so as to 

 form a code, referring them, if possible, to one single principle, into 

 which they may all be resolved. 



The object of Particular Physics, or of Natural History for the 

 terms are synonymous is the special application of the laws recognised 

 by the various branches of general physics to the numerous and varied 

 beings which exist in nature, in order to explain the phenomena which 

 each of them present. 



Within this extensive range, Astronomy also would be included; 

 but that science, sufficiently elucidated by Mechanics, and completely 

 subjected to its laws, employs methods differing too widely from those 

 required by Natural History, to admit of their being cultivated together 

 successfully. Natural History, then, is confined to objects which do not 

 allow of exact calculation, or of precise measurement in all their parts. 

 Meteorology also is subtracted from it and united to general physics; so 

 that, properly speaking, it considers only inanimate bodies called mine- 

 rals, and the different kinds of living beings, in all of which we may 

 observe the effects, more or less various, of the laws of motion and che- 

 mical attraction, and of all the other causes analysed by general physics. 



Natural History, in strictness, should employ similar methods with 

 the general sciences ; and it does so, in fact, whenever the objects it 

 examines are sufficiently simple to allow it. This, however, is but very 

 rarely the case. 



An essential difference between the general sciences and Natural 

 History is, that, in the former, phenomena are examined, whose condi- 

 tions are all regulated by the examiner, in order, by their analysis, to 

 arrive at general laws ; whereas, in the latter, they take place under 

 circumstances beyond the control of him who studies them, and who 

 seeks to discover, amid their complication, the effects of some general 

 principle already known. He is not, like the experimenter, allowed to 

 subtract them successively from each other, and thus reduce the 

 problem to its elements; he is compelled to take them entire, with all 

 their conditions at once, and can only perform the analysis in thought. 

 Suppose, for example, we attempt to insulate any of the numerous 



