EXPLANATION OF LAWS. 557 



mena have recently been subsumed under known 

 laws of electricity. It is thus that the most general 

 laws of nature are usually arrived at : we mount to 

 them by successive steps. For, to arrive by correct 

 induction at laws which hold under such an immense 

 variety of circumstances, laws so general as to be 

 independent of any varieties of space or time which 

 we are able to observe, requires for the most part 

 many distinct sets of experiments or observations, 

 conducted at different times and by different people. 

 One part of the law is first ascertained, afterwards 

 another part : one set of observations teaches us that 

 the law holds good under some conditions, another 

 that it holds good under other conditions, by com- 

 bining which observations we find that it holds 

 good under conditions much more general, or even 

 universally. The general law, in this case, is literally 

 the sum of all the partial ones ; it is the recognition 

 of the same sequence in different sets of instances ; 

 and may, in fact, be regarded as merely one step in 

 the process of elimination. That tendency of bodies 

 towards one another, which we now call gravity, had 

 at first been observed only upon the earth's surface, 

 where it manifested itself only as a tendency of all 

 bodies towards the earth, and might, therefore, be 

 ascribed to a peculiar property of the earth itself : one 

 of the circumstances, namely, the proximity of the 

 earth, had not been eliminated. To eliminate this 

 circumstance required a fresh set of instances in other 

 parts of the universe : these we could not ourselves 

 create ; and though nature had created them for us, 

 we were placed in very unfavourable circumstances 

 for observing them. To make these observations, fell 

 naturally to the lot of a different set of persons from 

 those who studied terrestrial phenomena, and had, 



