224 ADVANCEMENT OF LEARNING 



by a due dose, might in good measure check that wasting 

 inflammation which steals on with age. 



An experiment is inverted when the contrary of what 

 the experiment shows is proved; for example, heat is in 

 creased by burning glasses; but may cold be so too? So 

 heat in diffusing itself rather mounts upward, but cold in 

 diffusing itself rather moves downward. Thus, if an iron 

 rod be heated at one end, then erected upon its heated end, 

 and the hand be applied to the upper part of the rod, the 

 hand will presently be burned; but if the heated end be 

 placed upward and the hand applied below, it will be burned 

 much slower. But if the whole rod were heated, and one 

 end of it wet with snow or a sponge dipped in cold water, 

 would the cold be sooner propagated downward than up 

 ward if the sponge were applied below? Again, the rays 

 of the sun are reflected from a white body, but absorbed by 

 a black ove. Are shadows also scattered by black and col 

 lected by white bodies ? We see in a dark place, where 

 light comes in only at a small hole, the images of external 

 objects are received upon white paper, but not upon black. 



An experiment is compelled where it is urged or pro 

 duced to the annihilation or destruction of the power, the 

 prey being only caught in the other chases, but killed in 

 this. Thus the loadstone attracts iron urge, therefore, the 

 iron, or urge the loadstone, till they attract no longer; for 

 example, if the loadstone were burned, or steeped in aqua 

 fortis, would it entirely, or only in part, lose its virtue? 

 So if iron were reduced to a crocus, or made into prepared 

 steel, as they call it, or dissolved in aqua-fortis, would the 

 loadstone still attract it ? The magnet draws iron through 

 all known mediums gold, silver, glass, etc. Urge the me 

 dium, therefore, and, if possible, find out one that intercepts 

 the virtue. Thus make trial of quicksilver, oil, gums, 

 ignited gold, and such things as have not yet been tried. 

 Again, microscopes have been lately introduced which 

 strangely magnify minute objects; urge the use of them, 

 either by applying them to objects so small that their power 



