82 ADVANCEMENT OF LEARNING. [BOOK II. 



The magnetic virtue of iron was not first discovered in bars, 

 but in needles. 



But in my judgment the use of mechanical history is, of 

 all others, the most fundamental towards such a natural 

 philosophy as shall not vanish in the fume of subtile, 

 sublime, or pleasing speculations ; but be operative to the 

 endowment and benefit of human life ; as not only suggest 

 ing, for the present, many ingenious practices in all trades, 

 by connecting and transferring the observations of one art. 

 to the uses of another, when the experience of several arts 

 shall fall under the consideration of one man ; but as giving 

 a more true and real illumination with regard to causes and 

 axioms, than has hitherto appeared. For as a man s tempei 

 is never well known until he is crossed ; in like manner the 

 turns and changes of nature cannot appear so fully, when 

 she is left at her liberty, as in the trials and tortures of art. 



We add, that the body of this experimental history should 

 not only be formed from the mechanic arts, but also from the 

 operative and effective part of the liberal sciences, together 

 with numerous practices, not hitherto brought into arts ; so 

 that nothing may be omitted which has a tendency to inform 

 the understanding. 6 



e And therefore the history of sophistications, or adulterations and 

 frauds practised in arts and trades, ought to be inserted, which the 

 learned Morhof adds as a fourth part of this experimental history, 

 though it may seem nufficiently included under the history of arts, as 

 being the secret part essential to every art, and properly called the 

 mystery or craft thereof. Of these impositions, a large number may be 

 readily collected, and serve not only to quicken the understanding and 

 enrich experimental history, but also to contribute to perfect the science 

 of economical prudence. For contraries illustrate each other, and to 

 know the sinister practices of an art gives light to the art itself, as well 

 as puts men upon their guard against being deceived. See M.orhof s 

 &quot;Pdyhist.&quot; torn. ii. p. 128. Shew. 



