2 INTRODUCTION, 



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

 isolating bodies, reducing them to their greatest simplicity, in bringing 

 each of their properties separately into action, either by reflection or ex- 

 periment, and by observing or calculating the results ; and finally, in gene- 

 ralising and connecting the laws of these properties, 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 numerous 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 sub- 

 jected to its laws, employs methods, differing too widely from those re- 

 quired 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 subtracted from it and united to general physics ; so that, properly 

 speaking, it considers only inanimate bodies called minerals, and the dif- 

 ferent 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 doss 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 conditions 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 general laws. He is not, like the 

 experimenter, allowed to subtract them successively from each condition, 

 and to reduce the problem to its elements — he is compelled to take it in 

 its entireness, with all its conditions at once, and can perform the analysis 

 only in thought. Suppose, for example, we attempt to insulate the nu- 

 merous phenomena which compose the life of any of the higher orders of 

 animals ; a single one being suppressed, every vestige of life is annihi- 

 lated. 



Dynamics have thus nearly become a science of pure calculation; che- 



