EMPIRICAL LAWS. 



339 



breeds, both animal and vegetable, 

 are improved by crossing : that gases 

 have a strong tendency to permeate 

 animal membranes : that substances 

 containing a very high proportion of 

 nitrogen (such as hydrocyanic acid 

 and morphia) are powerful poisons : 

 that when different metals are fused 

 together, the alloy is harder than the 

 various elements : that the number of 

 atoms of acid required to neutralise 

 one atom of any base is equal to the 

 number of atoms of oxygen in the 

 base : that the solubility of substances 

 in one another depends * (at least in 

 some degree) on the similarity of their 

 elements. 



An empirical law, then, is an ob- 

 served uniformity, presumed to be 

 resolvable into simpler laws, but not 

 yet resolved into them. The ascertain- 

 ment of the empirical laws of pheno- 

 mena often precedes by a long interval 

 the explanation of those laws by the 

 Deductive Method ; and the verifica- 

 tion of a deduction usually consists in 

 the comparison of its results with 

 empirical laws previously ascertained. 



§ 2. From a limited number of ulti- 

 mate laws of causation, there are 

 necessarily generated a vast number 

 of derivative uniformities, both of 

 succession and of co-existence. Some 

 are laws of succession or of co-exist- 

 ence between different effects of the 

 same cause : of these we had examples 

 in the last chapter. Some are laws 



' * Thus, water, of which eight-ninths in 

 weight are oxygen, dissolves most bodies 

 "whicli contain a high proportion of oxygen, 

 such as all the nitrates (which have more 

 oxygen than any others of the common 

 salts,) most of the sulphates, many of ihe 

 carbonates, <fec. Again, bodies largely com- 

 posed of combustible elementa, like hydro- 

 gen and carbon, are soluble in bodies of 

 similar composition ; rosin, for instance, 

 will dissolve in alcohol, tar in oil of tur- 

 pentine. This empirical genenilisation is 

 far from being universally true ; no doubt 

 because it is a remote, and therefore easily 

 defeated, result of general laws too deep 

 for us at present to penetrate ; but it will 

 probably in time suggest processes of in- 

 quiry, leading to the discovery of those 

 laws. 



of succession between effects and their 

 remote causes, resolvable into the 

 laws which connect each with the in- 

 termediate link. Thirdly, when causes 

 act together and compound their 

 effects, the laws of those causes gene- 

 rate the fundamental law of the effect, 

 namely, that it depends on the co- 

 existence of those causes. And, finally, 

 the order of succession or of co-exist- 

 ence which obtains among effects 

 necessarily depends on their causes. 

 If they are effects of the same cause, 

 it depends on the laws of that cause ; 

 if on different causes, it depends on 

 the laws of those causes severally, and 

 on the circumstances which determine 

 their co-existence. If we inquire fur- 

 ther when and how the causes will 

 co-exist, that, again, depends on their 

 causes ; and we may thus trace back 

 the phenomena higher and higher, 

 until the different series of effects 

 meet in a point, and the whole is 

 showTi to have depended ultimately 

 on some common cause ; or until, 

 instead of converging to one point, 

 they terminate in different points, 

 and the order of the effects is proved 

 to have arisen from the collocation 

 of some of the primeval causes or 

 natural agents. For example, the 

 order of succession and of co-existence 

 among the heavenly motions, which 

 is expressed by Kepler's laws, is de- 

 rived from the co-existence of two 

 primeval causes, the sun and the 

 original impulse or projectile force 

 belonging to each planet. * Kepler's 

 laws are resolved into the laws of 

 these causes and the fact of their co- 

 existence. 



Derivative laws, therefore, do not 

 depend solely on the ultimate laws 

 into which they are resolvable : they 

 mostly depend on those ultimate laws 

 and an ultimate fact, namely, the 

 mode of co-existence of some of the 

 component elements of the universe. 

 The ultimate laws of causation might 

 be the same as at present, and yet 

 the derivative laws completely dif- 



* Or (according to Laplace's theory) tha 

 sun and the sun'g rotation. 



