120 Mr Glover on Forms of Induction. 



but all the particular instances included in that class need not 

 be known.* By the term property is meant a structure, a qua- ■ 

 lity, or a function. Our observations with regard to laws ap- 

 ply to such general exj^ressions as include all their particulars 

 with logical certainty ; and if in any place another meaning be 

 attached to the term, it shall be stated explicitly. 



On examination, the above definition will probably be found 

 to include every thing absolutely requisite to constitute a phy- 

 sical law ; and to be so general, that scarcely a law will be 

 found without some physical or metaphysical properties super- 

 added to those in the definition. But when illustrations are 

 sought, they will doubtless be found in accordance with our 

 statement. Thus, to take two examples differing in some re- 

 spects from each other ; the series of laws composing the New- 

 tonian doctrine of gravitation, and the generic terms of the me- 

 thod of natural families of plants, present laws expressing 

 generally, in the one case, the fact, that matter, in separate 

 masses, and within certain observed limits, has been found en- 

 dued with the property of gravitation, -f- — and in the other, 

 that in certain groups of plants, the individuals resembling one 

 another in form, do also agree in respect of medicinal and cu- 

 linary virtues. 



' This distinction is believed to be of great importance ; perhaps the fol- 

 ^Qwing illustration may explain more fully its nature. The first law in the 

 theory of gravitation was proved nearly as we are about to mention. Galilee 

 found experimentally a few balls of different materials to obey the law of gra- 

 vity within very short distances of the earth. Newton proved by calculation, 

 that the same law extends to the moon. And by trials of ^'^ery dissimilar 

 substances on the surface of our planet, it seemed to be made out that the 

 property of gravitation could belong to them only because it belongs to all 

 matter in their circumstances ; those bodies being so unlike, as that they could 

 scarcely owe the property to anything, except a common material nature. 

 Thus, when the law of gravity is stated as holding true of matter within cer- 

 tain limits, it includes in its expression (with logical propriety) innumerable 

 individual instances, many of which probably may differ somewhat from the 

 iustancesjoriginally experimented on. But if the grounds of the original 

 conclusion were correct, this latitude of expression cannot be objected to. 



t Dr Brown first shewed, in his usual forcible manner, that the law of gra- 

 vity could not be extended with logical propriety or physical certainty, beyond 

 observed limits. See sect. 8, p. 177 of the 1st vol. of his Lectures, 8vo ed., 



