NATURE OF THINGS. 441 



counsel that has nothing in it. Let us now, however, add 

 to this subject, if you please, a sprinkling of actual obser 

 vation. Thus, then, the greatest difficulty man encounters 

 in operation or experiment is, that it is scarcely possible to 

 keep together, act upon, and master the refractory properties 

 of a given quantity of matter, without such substance un 

 dergoing diminution or augmentation ; but a separation of 

 the parts taking place, the effort of experiment is rendered, 

 in the last resort, abortive. Now separation interposes 

 thus in two ways ; either so that a part of the matter flies 

 off as in extraction, or at least that a segregation of parts 

 takes place as in cream. The intention, therefore, of a 

 complete and thorough change of bodies is no other than 

 to vex matter by every well digested method of scrutiny ; 

 always, however, with due prevention of these two kinds of 

 separation, during the period of such process. For then, 

 and not till then, is matter truly delivered up bound into 

 our hands, when every avenue of escape has been closed 

 up. The third direction is this, that when men behold 

 alterations take place in the same section of matter, without 

 its being either increased or diminished, they should first 

 free their imagination from the deeply-rooted error, that 

 alteration is effected by separation alone ; and should then 

 begin painfully and carefully to discriminate the various 

 forms of alteration, when they ought to be placed to the ac 

 count of separation, when to that of disorganization only, 

 and a different collocation of the same parts, without other 

 separation ; when to that of both together. For I do not 

 believe, that when we shuffle hard, throw about, and melio 

 rate in our hands a harsh and untimely pear, by which it 

 acquires sweetness, or when amber or a diamond reduced 

 to an extremely fine dust, are divested of colour, that there 

 is any perceptible fraction of the substance of either lost, 

 but only that their component parts are arranged differently 

 as to place. 



It remains that we try to eradicate from the minds of men 

 an error of which the influence is such, that if credit con 

 tinues to be attached to it, several of the investigations we 

 have mentioned must be given up in despair as impracti 

 cable. For it is the common persuasion, that the ethers 

 (or spirits) of substances, when they have been brought to 

 an extreme degree of exility by heat, evaporate even in the 

 most solid vessels (such as silver or glass retorts), through 

 certain imperceptible pores and crevices. This is not true. 

 For neither air, nor such ethers, not even flame itself, 

 volatilize so perfectly, as to become capable of seeking or 



