190 ADVANCEMENT OF LEARNING. [bOOK V^ 



Amber and jet, chafed, attract straws, whence query, if they 

 will not do the same when warmed at the fire ? 



An experiment may be varied in quantity, wherein very 

 great care is required, as being subject to various errors. 

 For men imagine, that upon increasing the quantity the 

 virtue should increase proportionably; and this they com- 

 monly postulate as a mathematical certainty, and yet it is 

 utterly false. Suppose a leaden ball of a pound weight, let 

 fall from a steeple, reaches the earth in ten seconds, will a 

 ball of two pounds, where the power of natural motion, as 

 they call it, should be double, reach it in five? No, they 

 will fall almost in equal times, and not be accelerated ac- 

 cording to quantity.*^ Suppose a drachm of sulphur would 

 liquefy half a pound of steel, will, therefore, an ounce of sul- 

 phur liquefy four pounds of steel? It does not follow; for 

 the stubbornness of the matter in the patient is more in- 

 creased by quantity than the activity of the agent.'* Besides, 

 too much as well as too little may frustrate the effect, — thus, 

 in smelting and refining of metals it is a common errcr to 

 increase the heat of the furnace or the quantity of the flux; 

 but if these exceed a due proportion, they prejudice the 

 operation, because by their force and corrosiveness they turn 

 much of the pure metal into lumes, and carry it off", whence 

 there ensues not only a loss in the metal, but the remaining 

 mass becomes more sluggish and intractable. Men should 

 therefore remember how ^jEsop's housewife was deceived, who 

 expected that by doubling her feed her hen should lay two 

 eggs a day; but the hen grew fat, and laid none. It is abso- 

 lutely unsafe to rely upon any natural experiment before 

 proof be made of it, both in a less and a larger quantity. 



"* Because its surface in relation to its solidity is less than the first 

 fall, and consequently encounters less resistance fiom the air, with re- 

 spect to the entire quantity of its motion. Ed. 



*» This only happens when the increased content is attended with aug- 

 mentation ol surface. It may be accepted as a principle, that bodies are 

 exposed to tlie action of external agents in pro-portion as their surface is 

 extended, an increased size presenting a greater quantity of pores, 

 through which the agent may insinuate itself. As surfaces are only 

 as the squares of their diameters, and the contents increase in the ratio 

 of the cubes of their diameters, it follows that, in the &ame subject 

 matter, those bodies are more extended in relation to their soli- 

 dity, which have less bulk, and consequently more liable to the ftctioii 

 of external bodies, as Pjmjod reoaarks. Ed. 



