132 NOVUM ORGANUM 



No negative is here subjoined, except the remark that 

 sparks are not kindled by flint and steel, or any other hard 

 substance, unless some small particles of the stone or metal 

 are struck off, and that the air never forms them by friction, 

 as is commonly supposed; besides, the sparks from the 

 weight of the ignited substance have a tendency to descend 

 rather than to rise, and when extinguished become a sort 

 of dark ash. 



We are of opinion that here again there is no negative; 

 for we are not acquainted with any tangible body which does 

 not become decidedly warm by friction, so that the ancients 

 feigned that the gods had no other means or power of creat 

 ing heat than the friction of air, by rapid and violent rota 

 tion. On this point, however, further inquiry must be 

 made, whether bodies projected by machines (as balls from 

 cannon) do not derive some degree of heat from meeting the 

 air, which renders them somewhat warm when they fall. 

 The air in motion rather cools than heats, as in the winds, 

 the bellows, or breath when the mouth is contracted. The 

 motion, however, in such instances is not sufficiently rapid 

 to excite heat, and is applied to a body of air, and not to 

 its component parts, so that it is not surprising that heat 

 should not be generated. 



We must make a more diligent inquiry into this in 

 stance; for herbs and green and moist vegetables appear 

 to possess a latent heat, so small, however, as not to be 

 perceived by the touch in single specimens, but when they 

 are united and confined, so that their spirit cannot exhale 

 into the air, and they rather warm each other, their heat 

 is at once manifested, and even flame occasionally in suit 

 able substances. 



Here, too, we must make a more diligent inquiry; for 



