10 INTRODUCTION. 



produce on that tendency. It is purely a science of experiment, 

 and is irreducible to calculation. 



The theory of heat and that of electricity belong either to Dyna- 

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

 considered. 



The ruling method in all the branches of general physics consists 

 in insulating bodies, reducing them to their greatest simplicity, in 

 bringing each of their properties separately into action, either by 

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

 and finally, in generalising and connecting the laws of these pro- 

 perties, so as to form codes, and, if it were possible, to refer them 

 to one single principle into which they might 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 numer- 

 ous and varied beings which exist in nature, in order to explain the 

 phenomena which each of them presents. 



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 permit it to be cultivated by the 

 students of the latter. 



Natural History, then, is confined to objects which do not allow of 

 exact calculation, nor of precise measurement in all their parts. 

 Meteorology also is substracted from it and united to general phy- 

 sics; so that, properly speaking, it considers only inanimate bodies 

 called minerals, 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 chemical 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 con- 

 ditions 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 for the 

 purpose of discovering amid the complication, the effects of known 



