440 THOUGHTS ON THE 



supposition that we mean some invented matter of the 

 schools, intimate thus much in further explanation ; 

 namely, that the matter here introduced by us, is such, and 

 with such attributes invested, that it may be truly affirmed 

 of it, that more of that matter is present in one body, and 

 less (though they occupy the same dimensions) in another. 

 For instance, there is more of it in lead, less in water, 

 greatly less still in air, and that not in a vague sense, or a 

 dubious and unsatisfactory manner, but specifically, so as 

 to be matter of exact computation, as that there is twice as 

 much of it in this body, thrice as much in that, and so on. 

 If any one were to say, then, that air could be made out of 

 water, or water, again, out of air, I should listen to him ; 

 but should he say, that a like*quantity of water could be 

 made into a like quantity of air, I should not listen. For 

 that would be equivalent to saying that something could be 

 made into nothing. In like manner, conversely, if he were 

 to say that a determinate quantity of air (that, for example, 

 contained in a vessel of a given measure) could be con 

 verted into a like quantity of water, it would be the same 

 as saying that something can be made out of nothing. 

 From these principles, three rules or practical directions 

 seem to me deducible, in order that men may with greater 

 skill, and, in consequence of skill, with greater success, 

 conduct their trade with nature. The first is in this wise, 

 that men ought often to control nature by a counter-reckon 

 ing, in giving in her account ; that is, that when they see 

 some body, which had previously been full in the eye of 

 sense, make its escape and vanish, they should not at once, 

 as it were, authenticate and clear off the account of nature, 

 till a correct voucher has been given to them, whither such 

 body has transferred itself, and in what it has found a re 

 cipient. This, as matters now go, is most carelessly done, 

 and contemplation in general stops with appearances ; thus 

 men are ignorant of the recipient of flame, the most common 

 of substances ; for it is a perfect fallacy to suppose that it 

 is converted into the substance of the air. The second is 

 thus ; that while men regard the property inherent in matter 

 of being self-sustained, and not dropping into annihilation 

 or dissolution, as an adamantine necessity of nature, they 

 ought to permit no method to escape them of torturing and 

 agitating matter, if they would detect and drag to light its 

 ultimate workings and obstinately preserved secrets. Now 

 this may seem to be, what I at once admit that it is, an 

 admonition which it requires little sagacity to give : yet it 

 seems to contain in it something of real use ; it is not a 



