ADVANCEMENT OF LEARNING 101 



may much more probably be effected by a man acquainted with 

 the nature of gravity, color, malleability, fixedness, volatility, 

 the principles of metals and menstruums, than by one who is 

 ignorant of these natures, by the bare projection of a few grains 

 of the elixir. The same may be understood of the prolongation 

 of youth or retarding of old age, which may more rationally 

 be expected by dietary, regimen, bathings, anointing, and 

 proper medicines, directed by an accurate knowledge of the hu- 

 man frame, the nature of rarefaction, sustentation, assimila- 

 tion, and the reciprocal action of the mind upon the body, than 

 by a few drops or scruples of some precious liquor or quintes- 

 sence. But men are so headstrong and notional, as not only 

 to promise themselves things impossible, but also hope to ob- 

 tain the most difficult ends without labor or exertion. 



This practical doctrine of nature requires two appendages of 

 very great consequence. The first is, that an inventory be made 

 of the stock of mankind, containing their whole possessions 

 and fortunes, whether proceeding from nature or art, with the 

 addition also of things formerly known, but now lost ; so that 

 he who goes upon new discoveries may have a knowledge of 

 what has already been done. This inventory will be the more 

 artificial and useful, if it also contain things of every kind, which, 

 according to common opinion, are impossible ; as likewise such 

 as seemed next to impossible, yet have been effected, the one 

 to whet the human invention, and the other to direct it, so that 

 from these optatives and potentials actives may the more read- 

 ily be deduced. 



The second thing is, that a calendar be made of such experi- 

 ments as are most extensively useful, and that lead to the dis- 

 covery of others. For example, the experiment of artificial 

 freezing, by means of ice and bay salt, is of infinite extent, and 

 discovers a secret method of condensation of great service to 

 mankind ; fire is ready at hand for rarefaction, but the means 

 of condensation are wanted. And it would greatly shorten the 

 way to discoveries, to have a particular catalogue of these lead- 

 ing experiments. 



