LAWS OF NATURE. 383 



is called its weight, or of the downward pressure on 

 the mercury not being propagated equally in an 

 upward direction, or of a body pressed in one direc- 

 tion and not in the direction opposite, either not 

 moving in the direction in which it is pressed, or 

 stopping before it had attained equilibrium. If we 

 knew, therefore, the three simple laws, but had never 

 tried the Torricellian experiment, we might deduce its 

 result from those laws. The known weight of the air, 

 combined with the position of the apparatus, would 

 bring the mercury within the first of the three in- 

 ductions ; the first induction would bring it within 

 the second, and the second within the third, in the 

 manner which we so fully illustrated in treating of 

 Ratiocination. We should thus come to know the 

 more complex uniformity, independently of specific 

 experience, through our knowledge of the simpler 

 ones from which it results ; although, for reasons 

 which will appear hereafter, verification by specific 

 experience would still be desirable, and might possibly 

 be indispensable. 



Complex uniformities which, like this, are mere 

 cases of simpler ones, and have, therefore, been vir- 

 tually inferred in affirming those, may with propriety 

 be called laws, but can scarcely, in the strictness of 

 scientific speech, be termed Laws of Nature. It is the 

 custom of philosophers, wherever they can trace 

 regularity of any kind, to call the general proposition 

 which expresses the nature of that regularity, a law ; 

 as when, in mathematics, we speak of the law of 

 decrease of the successive terms of a converging series. 

 But the expression, law of nature, is generally em- 

 ployed by scientific men with a sort of tacit reference 

 to the original sense of the word law, namely, the 

 expression of the will of a superior ; the superior, in 



